Based on the work ofT.J. Wormald

sareeAgcnty foi Reapotch Cooperation

onth Clevelopmq Count roa

FOODAND

AGRtCULTUREORGANIZATION

OF THEUNITED NATIONS

Rome, 1992

Mixec nd purforest plantat nsin the tropicsE nl subtr pics

FAOFORESTRY

PAPER

103

Mixed and pu re forest plantations in the tropics and su btropics

Based on the work of T.J. Wormald

FAO FORESTRY

PAPER

103

sarec

FOOD AND

AGRICUL TURE ORGANIZATION

OF THE UNITED NATIONS

Rome, 1992

The designations employed and the presentation of material in thispublication do not imply the expression of any opinion whatsoever onthe part of the Food and Agriculture Organization of the UnitedNations concerning the legal status of any country, territory, city orarea or of its authorities, or concerning the delimitation of its frontiersor boundaries.

M-30ISBN 92-5-103216-5

All rights reserved. No part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by any means, electronic, mechani-cal, photocopying or otherwise, without the prior permission of the copyright owner.Applications for such permission, with a statement of the purpose and extent of thereproduction, should be addressed to the Director, Publications Division, Food andAgriculture Organization of the United Nations, Viale delle Terme di Caracalla,00100 Rome, Italy.

© FAO 1992

The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

M-30 ISBN 92-5-103216-5

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechani­cal, photocopying or otherwise, without the prior permission of the copyright owner. Applications for such permission, with a statement of the purpose and extent of the reproduction , should be addressed to the Director , Publications Division, Food and Agriculture Organization of the United Nations, Viale delle Terme di Caracalla, 00100 Rome, Italy.

© FAO 1992

(i)

ROREWORD

"Plantation forests represent approximately 3% of the present forestarea but contribute a much higher proportion of the annual world productionof wood"1. In several countries in the tropics these plantations have beenthe primary source of wood products and in others have even been seen asalternative sources of supply to the natural forest, which they thus protectfrom over-exploitation. Plantations are also established to provide shelterfor livestodk and to prevent erosion by wind or water, and to provide a rangeof non-wood forest products. Recently there have been proposals to createplantations to act as "c.97-bon sinks" with the aim of reducing global warningcaused by the greenhouse effect. The objectives of plantations weresummarised in one of the recommendations of the 10th World ForestryCongress:"A large increase in the area of plantations is an absolute necessity, inorder to satisfy a growing demand for wood products, to reduce stress onnatural forest ecosystems and to sequester atmospheric carbon".

Yet forest plantations have attracted criticism, despite their potentialbenefits. The rapid expansion of industrial plantations in the last fortyyears has led at times to strongly adverse reactions. These plantations havebeen overwhelmingly composed of only a few species on any scheme, andgenerally of a single, even-aged species in a compartment. Sometimes, increating these plantations, the rights of access of local people to the sitehave been lost, or species have been replaced on which they depended for saneaspect of their daily lives; often the clearing of the land and the burningof debris have caused erosion. TO many people the appearance of suchplantations, even in maturity, is artificial. Some temperate countries haveclaimed that stream flow is acidified in certain situations; sane othercountries have suspected that site productivityhas been reduced in second orsubsequent rotations. The mcst apparent cause of these problems is theperceived unnatural composition and structure of the large, even-aged blocksof one or a few species, and the apparent solution seems at first sight to beto plant a mixture of many species and ages.

A similar situation of criticism on the one hand and large potentialbenefits on the other arose with increasing emphasis on the use of speciesof the genus Eucalyptus. The Swedish International Development Agency (SIDA)commissioned FAO in 1985 to prepare a study2 to review the availableinformation on the ecological effects of Eucalyptus plantations which providedan authoritative report on the state of knowledge at that time. The presentstudy and extensive annotated bibliography has been commissioned by theSwedish Agency for Research Cooperation within Developing Countries (SAREC)with the aim of objectively analyzing the available evidence for or againstthe establishment of plantations composed of several species compared withthose composed of one species.

1 The Paris Declaration.to 26th September, 1991.

2 "The ecological effectsFAD Forestry Paper 59. 1985.

Tenth World Forestry Congress, Paris. 17th

of Eucalyptus" by M.E.D.Poore and C. Fries.

(il

FDREI'l)RD

"Plantation forests represent approximately 3% of the present forest area rut contriWte a lTU.lch higher proportion of the annual world production of wood" '. In several countries in the tropics these plantations have been the priIrary source of wood products and in others have even been seen as alternative sources of supply to the natural forest, which they thus protect fran over-exploitation. Plantations are also established to provide shelter for livestock and to prevent erosion by wind or water, and to provide a range of non-wood forest products . Recently there have been proposals to create plantations to act as "carbon sinks" with the aim of reducing global wanning caused by the greenhouse effect. The objectives of plantations were surmarised in one of the reccmrwandations of the 10th World Fbrestry Congress: "A large increase in the area of plantations is an absolute necessity, in order to satisfy a growing demand for wood products, to reduce stress on natural forest ecosystems and to sequester atrrospheric carbon".

Yet forest plantations have attracted criticism, despite their potential benefits. The rapid expansion of industrial plantations in the last forty years has led at times to strongly adverse reactions . These plantations have been oveJ:Whelmingly ccmposed of only a few species on any scherre, and generally of a single, even-aged speCies in a carpa.rt:ment . Sanetimes, in creating these plantations, the rights of access of local people to the site have been lost, or species have been replaced on which they depended for sare aspect of their daily lives; often the clearing of the land and the rurning of debris have caused erosion. To many people the appearance of such plantatiOns, even in maturity, is artificial. Sane tenperate countries have claimed that stream flCM is acidified in certain Situations; sare other countries have suspected that site productivity has been reduced in second or subsequent rotations. The II'OSt apparent cause of these problems is the perceived unnatural ccmposition and structure of the large, even-aged blocks of one or a few speCies, and the apparent solution seems at first sight to be to plant a mixture of many species and ages.

A similar situation of criticism on the one hand and large potential benefits on the other arose with increasing errphasis on the use of species of the genus Eucalyptus. The SWedish International Developrent Agency (SIDAl ccmnissioned mID in 1985 to prepare a studt to review the available infonnation on the ecological effects of Eucalyptus plantations which provided

. an authoritative report on the state of knCMledge at that time . The present study and extensive annotated bibliography has been ccmnissioned by the SWedish Agency for Research C=peration within Developing Countries (SARECl with the aim of objectively analyzing the available evidence for or against the establisrnent of plantations ccmposed of several species a::npared with those ccmposed of one species.

1 The Paris Declaration. Tenth World Fbrestry Congress, Paris . 17th to 26th September, 1991.

2 "The ecological effects of Eucalyptus" by M.E.D.Pcore and C.Fries. ~ Forestry Paper 59 . 1985.

FAD is indebted toMr. T. J.Wörmald, who had overall responsibility fordrafting the study, and to Mr J. Cedergren and Ms F. Goulet who did ncst ofthe literature research; to Messrs G. B. Applegate, C. Cossalter, R.

Delmastro, S. T. Mok, F. Cuino, A. Persson and J. L. Whitmore who with manymore from around the world provided helpful comment on the first draft; andfor the bibliographic assistance of the Director, Librarian and Staff of theOxford Forestry Institute (OFI, UK) and the Director and Staff of the CentreTechnique Forestier Tropical (caTT, France), which proved invaluable. WithinFAO the study WaR coordinated by J. B. Ball, with inputs from G. S. Child, W.M.Ciesla, S. Darroze, K. Janz, C.Palmberg-Lerche, W. A. Rodgers, P. Vantornmeand P. A. Wardle.

It is hoped that this study will be useful to foresters and othersinvolved in forestry development in the tropics and sub-tropics, to assistthemto decide on a sound technical and economic basis the species compositionof forest plantations and to put in proportion those dogmatic or emotionalstatements in favour or against single or multiple species plantations.

J. P. LanlyDirector

Forest Resources DivisionForestry Department

(ii)

F1IO is indebted to Mr. T. J. Wormald, who had overall responsibility for drafting the study, and to Mr J. Cedergren and Ms F. Goulet who did !lOSt of the literature research; to Messrs G. B. Applegate, C. Cossalter, R. Delmastro, S. T. M::lk, F. <Mino, A. Persson and J. L. Whitm::>re who with many lOClre fran around the world provided helpful a::mrent on the first draft; and for the bibliographic assistance of the Director, Librarian and Staff of the OXford Forestry Institute (OFl, UK) and the Director and Staff of the Centre Technique Forestier Tropical (CTFT, France), which proved invaluable. Within F1IO the study was coordinated by J. B. Ball, with inputs fran G. S. Child, W. M. Ciesla, S. Darroze, K. Janz, C. PaJroberg-Lerche, W. A. Rodgers, P. Vantame and P . A. Wardle .

It is hoped that this study will be useful to foresters and others involved in forestry developrent in the tropiCS and sub-tropiCS, to assist than to decide on a sound technical and econanic basis the species carp:lSition of forest plantations and to put in proportion those dogmatic or EmOtional statarents in favour or against single or Irn.lltiple species plantations.

J. . Lanly Director

Forest Resources Division Forestry Depart:ment

1 INTRODUCTION

BackgroundObjectives of the study 2

Scope of the study 2

Importance of management objectives 3

Good forestry practice 4Definitions of "mixture" 5

Extent of monospecific plantations 6

2 FOREST ECOSYSTEMS 8

3 ENVIRONMENTAL IMPACT 11

3.1 SOILS 11

Soil characteristics 11

Evidence for second rotation yield decline 13

Role of mixtures in soil management 17

Conclusions on soils 18

3.2 CLIMATE AND POLLUTION 19

Climate change 19

CO2 reservoirs 21

Microclimate 21

Pollution 22

3.3 FIRE 23

3.4 CONSERVATION OF ANIMAL AND PLANT GENETIC RESOURCES 23

General considerations 23

Conservation of biodiversity 24Wildlife management 26

Conclusions on conservation 29

3.5 INSECTS AND DISEASES 29

Stability of forest ecosystems 30

Same opposing views 31

Role of mixed planting 34

Conclusions on insects and diseases 36

3.6 CONCLUSIONS ON ENVIRONMENTAL IMPACT 37

4 NON-INDUSTRIAL PRODUCTS AND SERVICES 39

Non-commercial uses 39

FUelwood and poles 40

Fodder 40

Rehabilitation of degraded sites 40Shelterbelts and windbreaks 41

Urban and periurban planting 42

Sane examples of non-industrial plantations 42

Conclusions on non-industrial products and services 44

CONTENTS

Page

Background Objectives of the study Scope of the study

(iii)

Importanoe of management objectives Good forestry practioe Definitions of "mixture" Extent of rronospecific plantations

2 roms!' EXX>SYS':W!IS

3 ElWIKHmITAL IMPACT

3.1 SOILS

Soil characteristics Evidenoe for seccnd rotation yield decline Role of mixtures in soil management COnclusions on soils

3 . 2 CLIMATE AND Klu.UrION

Clinate change CO

2 reservoirs

Microclinate Pollution

3.3 FIRE

3 . 4 CONSERVATION OF ANIMAL AND PLANT GENErIC RESOURCES

General considerations COnservation of biodiversity Wildlife management Conclusions on conservation

3 . 5 INSEcr8 AND DISEASES

Stability of forest eccsystems Sane opposing views Role of mixed planting Conclusions on insects and diseases

3 .6 OONCLUSIONS ON ENVIRONMENTAL IMPAcr

Non-commercial uses FUelwood and poles Fodder Rehabilitation of degraded sites Shelterbelts and windbreaks Urban and periurban planting Sane examples of non-industrial plantations COnclusions on non-industrial products and servioes

1 2 2 3 4 5 6

8

11

11

11 13 17 18

19

19 21 21 22

23

23

23 24 26 29

29

30 31 34 36

37

39

39 40 40 40 41 42 42 44

(iv)

Page

5 THE MANAGEMENT OF MIXTURES 45

A classification of mixtures 45Silvicultural criteria for successful mixtures 49Methods of establishing mixtures 50Management skills 51Sane experiences with mixtures 52Conclusions on the management of mixtures 55

6 YIELDS 56

North America and temperate Asia 56Europe 57

Tropics 59Conclusions on yields 61

7 ECONMICS 62

The economics of mixtures 63Temperate experience 63Tropical experience 64Long term gains and losses 65Risk evaluation 66Conclusions on economics 67

8 MAIN CONCLUSIONS 68

Plantations in the tropics and sub-tropics 68Decline in yields of wood 68Importance of site and objectives 69Risk 69Synergy 70Types of plantations 70Conservation of wildlife 71

9 RECOMMENDATIONS 72

Objectives of plantations 72Matching species and management practices to site 72Situations where mixtures are appropriate 72

Growth monitoring 73Research 73Economic analysis 74

APPENDICES

1 Annotated Bibliography 75

2 Soils 119

3 Species mixtures 129

4 Sandalwood 145

5 Photographs 148

(iv)

5mE~OF~

A classification of mixtures Silvicultural criteria for sucoessful mixtures Methods of establishing mixtures Management skills sane experienoes with mixtures Conclusions on the management of mixtures

6 YIEIDS

North AIrerica and temperate Asia Europe Tropics Conclusions on yields

7 EXXH:IfiCS

The econanics of mixtures Temperate experienoe Tropical experienoe Long tenn gains and losses Risk evaluation Conclusions on econanics

Plantations in the tropics and sub-tropics Decline in yields of wood Importanoe of site and objectives Risk Synergy Types of plantations Conservation of wildlife

Objectives of plantations Matching species and management practices to site Situations where mixtures are appropriate Growth monitoring Research Econanic analysis

APPElIDICES

1 Annotated Bibliography

2 Soils

3 Species mixtures

4 Sandalwood

5 Photographs

45

45 49 50 51 52 55

56

56 57 59 61

62

63 63 64 65 66 67

68

68 68 69 69 70 70 71

72

72 72 72 73 73 74

75

119

129

145

148

1. INTRODUCTION.

Background

The total area of forest plantations in the world was estimated in1980 to be About 100 million hectares of which About 35 million ha were indeveloping countries; About 10 million ha were in tropical countries whichwere establishing new plantations at the rate of about 1.1 million hayearly (Lanly, 1982, FAO, 1988). While this rate of afforestation andreforestation was only a small proportion of that in the sub-tropical andtemperate zones it seems likely to increase as many countries seek tocompensate for the loss of natural forests. Due to the high potentialyields from plantations in the tropics (and sub-tropics) their contributionto wood production should be proportionately much greater than their area.About 40% of the existing and planned plantations have been established forfuelwood production and other non-industrial purposes (Lanly, 1982) but therest have been for the production of industrial roundwood. These latterplantations are typically simple in both structure and species composition;it has been pointed out (EVans, 1982) that pioneers such as Eucalyptusspecies, pines and teak account for 85% of all forest plantations in thetropics.

Despite the undoubted benefits of industrial roundwood plantations,such monospecific plantations and especially monocultures - the successionof one pure stand by another of the same species - carry risks ofcatastrophes such as wind blow and loss from pests and disease and thelikelihood of soil degradation and decline in yields. With theaccelerating destruction of natural forests in the tropics there areincreased fears that the forest plantation programme may be contributing tothe process of environmental degradation. Nevertheless in the developingcountries the heavy investment in forestry plantations that started in theparly years of the century and which increased dramatically in the nineteenfifties has relied to a large extent on monospecific, short rotationplantations. Although the investment has been large in relation toprevious work, in fact the total achievement is small in comparison to thepredicted demand for industrial roundwood. Rotations are commonly 20 to 30years, are seldom longer than 60 years and may be as short as 5 or 6 years(for example EUcalyptus globulus coppice in Ethiopia; Albizia falcatarialin Sabah, Fast Malaysia, Eucalyptus species in Brazil). Second rotationplantations are common and on sane sites third rotation crops have beenestablished. As a result of advances in tree breeding and in silviculturaltechniques the potential exists for increased yields; vegetativepropagation techniques make a quidk consolidation of these gains possible.But if rare is not taken there is also a risk that these techniques willlead to a reduction in the genetic diversity available for use andimprovement. The question needs to be asked whether these developmentstowards more intensive plantation operations carry unacceptable risks.

1 Previously known as Albizia fálcata and as A. moluccana and nowknown as Faraserianthes falcataria. Since the name Albizia fálcataria isbetter known to foresters it has been used throughout this study.

The total area of forest plantations in the world was estjroated in 1980 to be about 100 million hectares of which about 35 million ha were in developing countries; about 10 million ha were in tropical =untries which were establishing new plantations at the rate of about 1 .1 million ha yearly (Lanly, 1982, F7\0, 1988). While this rate of afforestation and reforestation was only a small proportion of that in the sub-tropical and tarperate zones it searlS likely to increase as many =untries seek to CCIlp€IlSate for the loss of natural forests. Due to the high potential yields fran plantations in the tropics (and sub-tropics) their contril:ution to wood production should be proportionately much greater than their area. About 40% of the existing and planned plantations have been established for fuelwood production and other non-industrial purposes (Lanly, 1982) rut the rest have been for the production of industrial roundwo:ld . These latter plantations are typically sirople in both structure and species carposition; it has been pointed out (Evans, 1982) that pioneers such as Eucalyptus species, pines and teak account for 85% of all forest plantations in the tropiCS.

Despite the undoubted benefits of industrial roundwo:ld plantations, such monospecific plantations and especially monocultures - the succession of one pure stand by another of the same species - carry risks of catastrophes such as wind blCM and loss fran pests and disease and the likelihood of soil degradation and decline in yields. With the accelerating destruction of natural forests in the tropics there are increased fears that the forest plantation prograrrme may be =ntril:uting to the process of environrrental degradation. Nevertheless in the developing countries the heavy invest:mant in forestry plantations that started in the early years of the century and which increased dramatically in the nineteen fifties has relied to a large extent on monospecific, short rotation plantations. Although the invest:mant has been large in relation to previous work, in fact the total achieverent is small in ccnparison to the predicted danand for industrial roundwo:ld. Rotations are ccmronly 20 to 30 years, are seldon longer than 60 years and may be as short as 5 or 6 years (for e:x:anple Eucalyptus globllus =ppice in Ethiopia; Albizia falcataria' in Sabah, East Malaysia, Eucalyptus species in Brazil). Second rotation plantations are ccmron and on sane sites third rotation crops have been established. As a result of advances in tree breeding and in silvicultural techniques the potential exists for increased yields; vegetative propagation techniques make a quick =nsolidation of these gains possible. But if care is not taken there is also a risk that these techniques will lead to a reduction in the genetic diversity available for use and iroproverent . The question needs to be asked whether these developrents tCMards more intensive plantation operatiOns carry unacceptable risks.

, Previously knCMn as Albizia falcata and as A. moluccana and nCM knCMn as Paraserianthes falcataria. Since the name Albizia falcataria is better knCMn to foresters it has been used throughout this study.

Objectives of the study

The objectives of this study are to:

review and analyse the benefits and draWbacks of mixed and pureplantations in the tropics and sub-tropics,to collate the field experiences of mixed and pure plantings,to determine, if possible, principles to be followed in establishingplantations,to suggest guidelines for field foresters and decision-makers.

This study has been derived fram an extensive review of theliterature and from contacts with foresters worldwide. Documentedreferences to mixed plantings in the tropics, however, are sparse anduneven, both in geographical distribution and in quality. Therefore whereexperience in the temperate zones has appeared to be relevant it has beenused

This paper is directed primarily to those foresters who have theresponsibility for planning plantation projects and to senior field staffand decision-makers who are responsible for prescribing the detailedmanagement of plantations. Secondarily, it is directed to policy makerswho must also be aware of the limitations of pure plantations and the roleof mixed plantations.

Scope of the study

The tropics are a fairly clearly defined belt spanning the equator.Whether the boundaries are set by latitude - the tropics of Cancer andCapricorn - or by the mean temperature of the coldest month (1892), or bythe difference in temperature between the coolest and warmest month (5°C)the countries covered do not change much. The growing conditions in thosecountries can, however, be very variable - humid rainforests, deserts,savannas and cool montane climates. The scope of this study also includesthe sub-tropics, the definition of which is geographically much more vague.Experiences have been included from the Himalayas, southern Africa andChile; experiences in south Australia have been discussed in some detail,because so much of the evidence for and against second rotation yielddecline has been collected there. The literature from northern Africa wasnot examined in detail, nor WaS that from the southern United States,though same data from there have been noted where they filled a gap in thetropical experience. Evidence from temperate zones has also been used inorder to supplement deficiencies in the tropical data, where consideredrelevant. The selection of literature has been directed towards developingcountries where possible; the availability of pdblished records has been amajor influence in determining which countries have been included.

Same technical limits have been set to the study. Those tree cropsusually considered to fall within the agricultural sector, such as rdbberor oil palm, and even those grown under the shade of trees, such as tea,coffee or cocoa, have been excluded. Mixtures involving the more obviouslyagricultural crops such as occur in agroforestry systems have been

22

~jectives of the study

The objectives of this study are to:

review and analyse the benefits and dl:awbacks of mixed and pure plantations in the tropics and sub-tropics, to collate the field experiences of mixed and pure plantings, to detennine, if possible, principles to be foll~ in establishing plantations, to suggest guidelines for field foresters and decision-makers.

This study has been derived fran an extensive review of the literature and fran contacts with foresters worldwide. IlocI.mented references to mixed plantings in the tropics, ~ver, are sparse and uneven , roth in geographical distribution and in quality . Therefore where experience in the te:rperate zones has appeared to be relevant it has been used.

This paper is directed primarily to those foresters who have the responsibility for planning plantation projects and to senior field staff and decision-makers who are responsible for prescribing the detailed managenent of plantations. Secondarily, it is directed to policy makers who must also be aware of the limitations of pure plantations and the role of mixed plantations.

Scqle of the study

The tropics are a fairly clearly defined belt spanning the equator . Whether the roundaries are set by latitude - the tropics of Cancer and Capricorn - or by the mean te:rperature of the coldest IlOl1th (18Ce), or by the difference in te:rperature between the coolest and warmest IlOl1th (5OC) the countries covered do not change much. The grcMing conditions in those countries can, ~ver, be very variable - humid rainforests, deserts, savannas and cool IlOl1tane climates. The scope of this study also includes the sub-tropiCS, the definition of which is geographically much !lOre vague. Experiences have been included fran the Himalayas, southern Africa and Chile; experiences in south Australia have been discussed in sane detail, because so much of the evidence for and against second rotation yield decline has been collected there. The literature fran northern Africa was not examined in detail, nor was that fran the southern United states, though sane data fran there have been noted where they filled a gap in the tropical experience. Evidence fran te:rperate zones has also been used in order to supplenent deficiencies in the tropical data, where considered relevant . The selection of literature has been directed t~ developing countries where possible; the availability of published records has been a major influence in detennining which countries have been included .

Sane technical limits have been set to the study . Those tree crops usually considered to fall within the agricultural sector, such as rubber or oil palm, and even those gra.m under the shade of trees, such as tea, coffee or cocoa, have been excluded . Mixtures involving the !lOre obviously agricultural crops such as oc= in agroforestry systems have been

3

excluded, because they are covered in the extensive agroforestryliterature.

This is a study of forest plantations, therefore naturallyregenerated mixtures have not been considered, except in so far asnaturally regenerated indigenous species may contribute to diversity inartificially established stands. Enrichment planting is in concept atechnique for improving natural stands and as such would be excluded fromthis study, but the distinction between enrichment planting and replacementplanting is often a fine one. Enrichment planting is used to establishfavoured species in a matrix of naturally occurring trees; such plantingscan eventually through selective felling of the natural stand be convertedto a pure plantation. This technique has been used to establish some of thegenera in the family Meliaceae. Enrichment planting is therefore discussedbriefly.

The natural regeneration of herbs and shrubs in tree plantations,whether of a single or several species, has been considered to provide someof the benefits of a mixture; these same herbs and shrubs may be referredto as "weeds", however, when they interfere with the planted trees,especially during the establishment phase.

Importance of management objectives

The need for clear objectives for plantation establishment isparamount and is stressed throughout this study. The objectives will to alarge extent determine the manner in which a plantation is established andmanaged as well as the species used. If the primary objective is to raisea uniform product, as is usual for an industrial process, then the scopefor mixed plantations may be limited. Conversely if the primary objectiveis to protect a sensitive site, then mixtures may be more appropriate, andmany of the techniques suited to industrial production may becameunacceptable. Where the site is not a limiting factor, the end product orproducts and the biology of the species selected will determine theappropriateness of mixed or pure plantations.

Mbst of the literature discusses mixtures in relation to industrialplantations. But in the developing countries a high proportion ofplantations are for "non-industrial" purposes (primarily fuelwood andpoles) (FAO 1988). In the Middle East all plantations have been describedas non-industrial; in West Sahelian Africa over 80% are non-industrial; inseveral regions, including East Africa, Insular Africa (Madagascar andother islands), South Past Asia from Myanmar to Vietnam, more than 50% ofplantations were non-industrial in 1980.

Table 1: Areas ('000ha) of established in 1980.plantations,

Source: FAO 1988

TotalHardwoods

Industrial Non industrialSoftwoods

Africa 642 (21%) 659 (22%) 1686 (56%) 2987Asia(excl China)

2891 (55%) 592 (11%) 1759 (34%) 5242

S.America 1085 (28%) 2322 (37%) 2170 (35%) 5877Pacific Ocean 5 78 (89%) 5 ( 6%) 88Total 4623 (33%) 3651 (26%) 5620 (41%) 13894

3

excluded, because they are covered in the extensive agroforestry literature.

This is a study of forest plantations, therefore naturally regenerated mixtures have not been considered, except in so far as naturally regenerated indigenous species may contriblte to diversity in artificially established stands . Enrichment planting is in concept a technique for improving natural stands and as such would be excluded fran this study, rut the distinction between enrichment planting and replac::arent planting is often a fine one. Enrichment planting is used to establish favoured species in a matrix of naturally oc=ing trees; such plantings can eventually through selective felling of the natural stand be converted to a pure plantation. This technique has been used to establish SCIre of the genera in the family Meliaceae. Enrichment planting is therefore discussed briefly.

The natural regeneration of herbs and shrubs in tree plantations, whether of a single or several species, has been considered to provide SCIre

of the benefits of a mixture; these same herbs and shrubs may be referred to as "weeds", ~ver, when they interfere with the planted trees, especially during the establishment phase.

IDportance of management: objectives

The need for clear objectives for plantation establishment is pararrount and is stressed throughout this study. The objectives will to a large extent detennine the manner in which a plantation is established and managed as well as the species used . If the primary objective is to raise a unifolJll product, as is usual for an industrial prooess, then the scope for mixed plantations may be limited. Conversely if the primary objective is to protect a sensitive site, then mixtures may be more appropriate, and many of the techniques suited to industrial production may bec:are unacceptable. Where the site is not a limiting factor, the end product or products and the biology of the species selected will detennine the appropriateness of mixed or pure plantatiOns.

MOst of the literature discusses mixtures in relation to industrial plantations. But in the developing countries a high proportion of plantations are for "non-industrial" purposes (primarily fuelwood and poles) (TIlO 1988). In the Middle East all plantations have been described as non-industrial; in West Sahelian Africa over 80% are non-industrial; in several regions, including East Africa, Insular Africa (Madagascar and other islands), South East Asia fran Myanmar to Vietnam, more than 50% of plantations were non-industrial in 1980 .

Table 1: Areas (' OOOha) of established plantations, in 1980 . Industrial Non industrial

Hardwoc:rls Softwoods Africa Asia (excl China) S.l\Irerica Pacific Ocean Total

642 (21%) 659 (22%) 2891 (55%) 592 (11%)

1085 5

4623

(28%)

(33%)

2322 78

3651

(37%) (89%) (26%)

Source : TIlO 1988

1686 1759

2170 5

5620 .

(56%) (34%)

(35%) ( 6%) (41%)

Total

2987 5242

5877 88

13894

4

A large proportion of the forestry effort in the tropics andsubtropics is involved in growing products, such as fuelwood, for whichuniformity of size or technical properties is not of major importance andtherefore mixtures may be suitable.

It is usual for plantation projects to have more than one objective.It is readily adknowledged that in industrial plantation projects anobjective should be the maintenance of site fertility. It is probably lessreadily recognised that the management of a protection forest will alsoyield forest products and a financial return and, where there is pressureon the land, it is extremely difficult to protect forests unless they canbe seen to be managed and to be productive. Production, stbject to goodforestry practice, is an essential paxt of active management and can helpsatisfy the requirements of villagers neighbouring the forest; furthermorein many developing countries revenue is required in order to maintainprotection.

Good Forestry Practice

Reference has already been made to good forestry practice and theneed for it will be stressed throughout this study. Good forestry practicemeans the conduct of forestry operations in sudh a way that not only is theplantation maintained in a vigorous and hPalthy condition, but also thatthe fertility of the site is maintained in future rotations. Good forestrypractice is the tedhnical contribution to sustainable forestry development;social and economic considerations are also of major importance. The needfor good forestry practice is particularly apparent at four stages in arotation.

Species selection.

It is necessary to match species to site with particular reference toclimate and soil; planting a species or provenance in conditions that aredifferent fram those of its natural range, that is "off-site", generallycauses problems sooner or later.

Site clearance and establishment.

Site clearing and establishment techniques must be appropriate to thesite with particular reference to the species as well as soil type, slopeand rainfall intensity. Any practice that risks serious erosion or loss offertility is not good forestry practice; the maintenance of ground coverand the minimal use of fire and of earth moving equipment during sitepreparation is indicated.

maintenance and management.

During the establishment phase it is iwortant to ensure that thecrop gets a good start. This is usually done by enabling the crop todominate the site as quiCkly as possible and is achieved by weed controland ensuring that there are adequate nutrients and moisture, for example byadding fertiliser and by mulching or maintaining ground cover.

In later phases of growth, at least for wood production, it isimportant to prevent stagnation. This is achieved by timely thinning whenbasal area current annual increment falls off. Overstocking in older

4

A large proportion of the forestry effort in the tropics and subtropics is involved in grcMing products, such as fuelwood, for which unifonnity of size or technical properties is not of I!'ajor iroportance and therefore mixtures I!'ay be suitable.

It is usual for p l antation projects to have lOClre than one objective. It is readily acknCMledged that in industrial plantation projects an objective should be the I!'aintenance of site fertility . It is probably less readily recognised that the I!'anagement of a protection forest will also yield forest products and a financial return and, where there is pressure on the land, it is extremely difficult to protect forests unless they can be seen to be I!'anaged and to be productive . Production, subject to good forestry practice, is an essential part of active I!'anagement and can help satisfy the requirements of villagers neighbouring the forest; furtheDOClre in I!'any developing countries revenue is required in order to I!'aintain protection .

Good Forestry Practice

Reference has already been I!'ade to good forestry practice and the need for it will be stressed throughout this study. Good forestry practice rreans the conduct of forestry operations in such a way that not only is the plantation I!'aintained in a vigorous and healthy condition, rut also that the fertility of the site is I!'aintained in future rotations . Good forestry practice is the technical contriWtion to sustainable forestry developnent; social and econanic considerations are also of I!'ajor iroportance . The need for good forestry practice is particularly apparent at four stages in a rotation.

1. Species selection.

It is necessary to I!'atch species to site with particular reference to cliI!'ate and soil; planting a species or provenance in conditions that are different fran those of its natural range, that is "off-site", generally causes problems sooner or later.

2. Site clearance and establishment .

Site clearing and establishment tec,~iques must be appropriate to the site with particular reference to the species as well as soil type, slope and rainfall intensity. Any practice that risks serious erosion or loss of fertility is not good forestry practice; the I!'aintenance of ground cover and the minimal use of fire and of earth lOClving equipnent during site preparati on is indicated .

3. Maintenance and I!'anagement.

During the establishment phase it is iroportant to ensure that the crop gets a good start. This is usually done by enabling the crop to daninate the site as quickly as possible and is achieved by weed control and ensuring that there are adequate nutrients and lOClisture, for exanple by adding fertiliser and by lIUllching or I!'aintaining ground cover.

In later phases of grCMth, at least for wood production, it is iroportant to prevent stagnation . This is achieved by tiIooly thinning when basal area current annual increment falls off. OIrerstocking in older

5

plantations is a common feature of poorly managed plantations and resultsin almost complete ladk of an understorey and herb layer.

4. Protection.

Practising good forest hygiene to control potential sources of pestsand diseases.

It is not always easy to reconcile the practices recammended; forexample forest hygiene or weed control may best be achieved by a hot fireduring site preparation, but that may promote erosion. Decisions depend onlocal circumstances and if there is a conflict between the species proposedand good forestry practice then it may well indicate that the wrong speciesis being raised.

Good forestry practices apply both to pure and mixed plantations, butsometimes the promotion of mixed species plantations - to obtain soilcoverage, or to improve soil quality through influence on microfauna andflora - is an essential part of good forestry practice, especially onenvironmentally sensitive sites.

Definitions of Ionixture".

A classification is given in chapter 5 which considers mixtures firstin terms of whether the mixture is single layered, that is a mixture ofdominants, or whether it is two or more layered; secondly whether themixture is temporary or permanent. This is a convenient classification fordescribing silvicultural requirements. It is also worth remembering thatthere is a spectrum of degrees of mixture from one extreme of "purity" tobe found in a monoclonal plantations, through polyclonal plantations,monospecific (single or multiple provenances), plantations of a few speciesgrown in blocks of one age and finally, at the other extreme, to apolyspecific all-age plantation. This spectrum also exists in nature,where natural forests may not necessarily be composed of many, or evenseveral, species. A pure plantation is generally taken to be amonospecific crop which may consist of one or several provenances; in thetropics a mixed industrial plantation is usually a mixture of two species,but the manner of mixture may be quite varied - for instance single ormulti-layered, coppice, temporary or permanent. Mixtures are not alwaysthe consequence of a deliberate planting policy, they may be created as aresult of the natural regeneration of understorey "weed" species inplantations maintained at a relatively wide spacing. Polyspecific all-agedindustrial plantations are not common, though the SundapolaMahogany/Teak/Jak plantations in Sri Lanka (Tisseverasinghe andSatchithananthan 1957; MUttiah 1965, 1991) can be considered to be a smallscale example. The very complex mixture approximating to a natural mixedtropical forest described above might, however, be appropriate to fuelwoodplantations and would certainly be appropriate to protection plantations onsensitive sites.

The definitions of mixtures given above imply an intimate, tree bytree or line by line mixture or possibly mixtures of small groups. But amixture, in the broad sense, can also be obtained by planting adjacentcompartments or blocks with different species and a mixture of a differentkind can also be achieved by rotating species. In this study all levels ofmixture are considered; lessons can be learned from the techniques for

5

plantations is a ccmron feature of poorly managed plantations and results in alIoclst canplete lack of an understorey and herb layer.

4 . Protection.

PractiSing good forest hygiene to control potential sources of pests and diseases .

It is not always easy to reconcile the practices recx:mrended; for example forest hygiene or weed control may best be achieved by a hot fire during site preparation, rut that may prarote erosion. Decisions depend on local circumstances and if there is a conflict between the species proposed and good forestry practice then it may well indicate that the wrong species is being raised .

Good forestry practices apply both to pure and mixed plantations, rut saneti:rres the prarotion of mixed species plantations - to obtain soil coverage, or to improve soil quality through influence on mi=fauna and flora - is an essential part of good forestry practice, especially on environmentally sensitive sites.

Definitions of ''mixture''.

A classification is given in chapter 5 which considers mixtures first in tenns of whether the mixture is single layered, that is a mixture of daninants, or whether it is two or IOOre layered; secondly whether the mixture is tE!rq;lorary or pennanent . This is a convenient classification for describing silvicultural requirarents. It is also worth rem3llbering that there is a spectrum of degrees of mixture fran one extrem;! of "purity" to be found in a IOOnoclonal plantatiOns, through polyclonal plantations, m:mospecific (single or IlIIlltiple provenances), plantations of a few species 9= in blocks of one age and finally, at the other extrem;!, to a polyspecific all-age plantation . This spectrum also exists in nature, where natural forests may not necessarily be canposed of many, or even several, species . A pure plantation is generally taken to be a m:mospecific crop which may consist of one or several provenances; in the tropics a mixed industrial plantation is usually a mixture of two species, rut the manner of mixture may be quite varied - for instance single or IlIIllti-layered, coppice, tE!llpOrary or pennanent. Mixtures are not always the consequence of a deliberate planting policy, . they may be created as a result of the natural regeneration of understorey "weed" species in plantations maintained at a relatively wide spacing . Polyspecific all-aged industrial plantations are not carrron, though the Sundapola Mahogany/Teak/Jak plantations in Sri Lanka (Tisseverasinghe and Satchithananthan 1957; Mllttiah 1965, 1991) can be considered to be a small scale example. The very canplex mixture approximating to a natural mixed tropical forest described above might, hC1Never, be appropriate to fuelwood plantations and would certainly be appropriate to protection plantatiOns on sensitive sites .

The definitions of mixtures given above imply an intimate, tree by tree or line by line mixture or possibly mixtures of small groups. But a mixture, in the broad sense, can also be obtained by planting adjacent canpart:rrents or blocks with different species and a mixture of a different kind can also be achieved by rotating species. In this study all levels of mixture are considered; lessons can be learned fran the techniques for

achieving clonal mixtures as much as fram mixtures of species or genera.In particular attention is drawn to the potential for the use of a "broadsense" mixture of baocks rather than a "narrow sense" intimate, tree bytree mixture. One of the objectives of this study is to examine haw thedesirable effects of mixtures can be achieved with the minimum complexityof management systems.

The extent of monospecific plantations

A recent assessment of the aras of forest plantations in the tropicsshows that eucalypts, pines, teak and acacias are the most frequentlyplanted species. In Africa and in tropical Latin America, Eucalyptus spp.and pines comprise About 50% and 80% respectively of the plantation area,whereas in tropical Asia there are a large number of species, of which theeucalypts, teak and various acacias comprise 32% (Pandey, 1992).

The extent to which pure plantations have been established in thetropics is not known, but is indicated by the following relatively smalllist of the major plantation species of the tropics (Evans 1987):

PinesP.patu1a, P.caribaea, P.e11iottii, P.kesiya,P..merkusii, P.00cazpa & others

Other conif ersAraucaria curiningharaii, A.angustifolia, Cupressus1usitanica & others

EucalyptsE.grandis, E.cama1du1ensis, E.g1obulus, E.saligna,E.deg1upta, E. te.reticorr2is, E.robusta,E.citriodora, E.urophy11a & others

Teak Tectona grandisOther hardwoods

Acacia, ame1ina arborea, Meliaceaea, Terminaliaspp. Albizia spp . , Trip1ochiton scieroxy1on &others

34%

3%

37%

14%12%

This list narres 10 coniferous species, 9 eucalypt species and 7 otherhardwood families or genera. Given the range of soils and climates in thetropics this would appear to imply the likelihood of a still morerestricted range of species in a country or in a relatively homogenouslocation such as a district. However, some of these species, e.g.EUcalyptus cama1du1ensis occur naturally over a very large area and have anumber of different provenances.

Mixtures in the narro» sense of raising more than one species in acompartment are not commaim in industrial plantations. In the broader senseof establishing different species in neighbouring compartments it is hardto estimate from published records the extent to which mixing is takingplace. In Nie Zealand Pinus radiata accounts for 85% of forest plantations(Burdon 1982), so clearly there is very little mixing there. In same ofthe states in Australia the proportion is even higher (Fergusson 1983).

Same of the pulp plantations in southern Africa may involve largeblocks of Pinus patu1a or of eucalypts. The Usutu plantations inSwaziland, which cover 52 000 ha, have predaminantly been established toRratu1a as has the Viphya plateau in Malawi and the same applies to the

6

achieving clonal mixtures as IlUlch as fran mixtures of species or genera. In particular attention is drawn to the potential for the use of a "broad sense" mixture of blocks rather than a "na.rrow sense" intlinate, tree by tree mixture. One of the objectives of this study is to examine heM the desirable effects of mixtures can be achieved with the minilln.lm carplexity of management systems . .

'l!Je extent of III' I sped fie plantat.iorls

A recent assesSllalt of the areas of forest plantations in the tropics shcMs that eucalypts, pines, teak and acacias are the most frequently planted species. In Africa and in tropical Latin America, Eucalyptus spp. and pines carprise about 50% and 80% respectively of the plantation area, whereas in tropical Asia there are a large number of species, of which the eucalypts, teak and various acacias carprise 32% (Pandey, 1992).

The extent to which pure plantations have been established in the tropics is not kna-/Il, rut is indicated by the following relatively small list of the !l'ajor plantation species of the tropics (Evans 19B7):

Pines 34% P.patula, P. caribaea, P.elliottii, P.kesiya, P.merJrusii, P.oocarpa & others

Other conifers 3% Araucaria cunninghamii, A. angustifolia, Cupressus lusitanica & others

Eucalypts 37% E.grandis, E.camaldulensis, E.globulus, E.saligna, E.deglupta, E. tereticornis, E.rol:.usta, E.citriodora, E.urophylla & others

Teak 7ectooa grandis 14% Other llaJ:dwoods 12%

Acacia, Gnelina arborea, Meliaceaea, TeIIlZinalia spp., Albizia spp., Triplochiton scleroxylon & others

This list names 10 coniferous speCies, 9 eucalypt species and 7 other haJ:dwood families or genera. Given the range of soils and cllinates in the tropics this would appear to imply the likelihood of a still rrore restricted range of species in a country or in a relatively harogenous location such as a district. Hcw=ver, sane of these species, e. g . Eucalyptus camaldulensis oc= naturally over a very large area and have a number of different provenances.

Mixtures in the na.rrow sense of raising rrore than one species in a c:anpart:nent are not c:c:mOCm in industrial plantations. In the broader sense of establishing different species in neighbouring c:anpart:nents it is hard to estlinate fran published records the extent to which mixing is taking place. In New Zealand Pinus radiata accounts for 85% of forest plantations (Burdon 1982), so clearly there is very little mixing there. In sane of the states in Australia the proportion is even higher (Fergusson 1983).

Sare of the pulp plantations in southern Africa !l'ay involve large blocks of Pinus patula or of eucalypts. The Usutu plantations in swaziland, which cover 52 000 ha, have predaninantly been established to P.patula as has the Viphya plateau in Malawi and the same applies to the

7

pulp planting schemes in East Africa at Sao Hill in Tanzania and Turbo inKenya.

It used to be the practice in many of the forest districts in thehighlands of East Africa to plant a range of fast growing species such asP.radiata, P.patula, CUpressus lusitanica and same _Eucalyptus species.This range, however, has been steadily eroded. The area of eucalyptplanted was reduced sharply when the railways converted to oil burning,P.radiata ceased to be planted on any scale in the nineteen sixties becauseof Zuothistroma blight and now C.lusitanica and other Cupressaceae aresubject to severe attack by the aphid Cinara cupressi which may precludethem from future plantation programmes in East Africa. In Kenya softwoodplanting in the highlandR is now largely confined to one species, Pinuspatula.

It appears that monospecific industrial plantations are common, hitthere are reports of extensive plantations of mixed species (arcalyptustereticcrnis and Acacia auriculifbrmis) in Vietnam (Cossalter 1991) andelsewhere, though it is not clear whether these are industrial plantationsnor whether they have been successful in meeting defined objectives.

7

pulp planting schem:s in East Africa at Sao Hill in Tanzania and Turbo in Kenya.

It used to be the practice in many of the forest districts in the highlands of East Africa to plant a range of fast grc1Ning species such as P.radiata, P.patula, Cupressus lusitanica and saoo Eucalyptus species. This range, ~ver, has been steadily eroded . The area of eucalypt planted was reduced sharply when the railways converted to oil ruming, P .radiata ceased to be planted on any scale in the nineteen sixties because of Ibthistrana blight and new C.lusitanica and other cupressaceae are subject to severe attack by the aphid Cinara cup:ressi which may preclude them fran future plantation progranrnes in East Africa. In Kenya sof~ planting in the highlands is new largely confined to one species, Pinus patula .

It appears that monospecific industrial plantations are ccmnon, rut there are reports of extensive plantations of mixed species (Eucalyptus te:reticornis and Acacia auriculifo:cmis) in Vietnam (Cossalter 1991) and elsewhere , though it is not clear whether these are industrial plantations nor whether they have been successful in meeting defined objectives .

2. FOREST ECOSYSTEMS,,

Natural forest ecosystems vary from great complexity tocomparative simplicity of species associations. Ecosystemsimplification is associated with specialisation and tends to bea response to extreme climatic, edaphic or other abioticconditions. Thus forests with simplified structures and areduced number of specialised species are more common in theharsher climate of the colder areas of the world; the birchforests of the northern boreal forests, Pinus mugo and P.cembraat high elevations in Europe, Cupressus sempervirens on south-facing limestone slopes in Crete, Alnus glutinosa in peatyvalleys in Britain (Rackham 1990). In South Australia theindigenous woodland is characterized by near monospecific stands(Boardman 1990).

Although in the humid tropics rainforests are typicallypolyspecific and many layered, stands having reduced diversitydo occur; they include natural stands of Eucalyptus species andtropical pines, as well as mangrove swamps and tree savannas withlow rainfall and frequent fires, both of which are relativelypoor in tree species. In Uganda stands dominated by Cynometraalexandri and by Parinari excelsa are two examples of naturalstands in which the number of species is limited. Elsewhere inAfrica pure stands of Acacia tortilis, A.nilotica andColophospermum mopane are not uncommon. In Latin American dryzones large areas may be covered by a single Prosopis spp. Inthe Kemahang forest in the Malay peninsular there was, beforeexploitation in the nineteen sixties, a reduced number ofdipterocarp species and of other species in the familiesBurseraceae, Lauraceae, Myristaceae, Myrtaceae and Sapotaceae andwhich are believed to have arisen after a freak storm of November1888 (Whitmore 1984). Agathis species in south Kalimantanoccurred, before logging, in stands up to 5000 ha in area inwhich it foLmed the main or sole top-of-canopy species (Whitmore1984). In many cases within polyspecific stands there may begroups of a single species, or even clumps of a single clone.Thus although, given conditions of adequate nutrient supply,plenty of moisture and high solar radiation, complex polyspecificecosystems are normal, there is nothing inherently unnaturalabout monospecific stands; where natural mixtures occur, on theother hand, they are often temporary.

All natural ecosystems are dynamic and are characterisedby successional phases. Disturbances occur at irregularintervals in natural forests, sometimes after centuries, but onsome sites, for instance savannas prone to fire, at frequentintervals. The stages of a secondary succession after adisturbance to a forest ecosystem are typically characterised byan early invasion of a few light demanding, aggressive but short-lived pioneer species frequently occurring in single speciesstands, which are followed by colonisation with successively moreshade tolerant species which grow up through the canopy of thepreceding seral stage eventually to become dominants. Ultimatelyin some ecosystems in the late successional stage a relativelyconstant mix of species is reached, which will last until the

88

2. FOREST ECOSYSTEMS.

Natural forest ecosystems vary from great complex ity to comparative simplicity of species associations. Ecosys tem simplification is associated with specialisation and tends to be a response to extreme climatic, edaphic or other abiotic conditions . Thus forests with simplified structures and a reduced number of specialised species are more c ommon in the harsher climate of the colder areas of the world; the birch forests of the northern boreal forests, Pinus mugo and P . cembra at high elevations in Europe, Cupressus sempervirens on south­facing limestone slopes in Crete, Aln us glutinosa in peaty valleys in Britain (Rackham 1990). In South Australia the indigenous woodland is characterized by near monospecific stands (Boardman 1990) .

Although in the humid tropics rainforests are typically polyspecific and many layered, stands having reduced diversity do occur; they include natural stands of Eucalyptus species and tropical pines, as well as mangrove swamps and tree savannas with low rainfall and frequent fires, both of which are relatively poor in tree species. In Uganda stands dominated by Cynometra alexandri and by Parinari e xcelsa are two e xamples o f na tural stands in which the number of species is limited. Elsewhere in Africa pure stands of Acacia tortilis, A.nilotica and Colopbospermum mopane are not uncommon. In Latin American dry zones large areas may be covered by a single prosopis spp. In the Kemahang forest in the Malay peninsular there was, before exploitation in the nineteen sixties, a reduced number of dipterocarp species and of othe r s pe cies in the families Burseraceae, Lauraceae, Myristaceae, Myrtaceae and Sapotaceae and which are believed to have arisen after a freak storm of November 1888 (Whitmore 1984 ) . Agatbis species in south Kalimantan occurred, before logging, in stands up to 5000 · ha in area in which it formed the main or sole top-of-canopy species (Whitmore 1984). In many cases within polyspecific stands there may be groups of a single speCies, or even clumps of a single clone. Thus although, given conditions of adequate nutrient supply , plenty of moisture and high solar radiation, complex polyspecific ecosystems are normal, there is nothing inherently unnatural about monospecific stands; where natural mixtures occur, on the other hand, they are often temporary.

All natural ecosystems are dynamic and are characterised by successional phases . Disturbance s occur at irregular intervals in natural forests, sometimes after centuries, but on some sites, for instance savannas prone to fire, at frequent intervals . The stages of a secondary succession after a disturbance to a forest ecosystem are typically characterised by an early invasion of a few light demanding, aggressive but short­lived pioneer species frequently occurring in single species stands, which are followed by colonisation with successively more shade tolerant species which grow up through the canopy of the preceding seral stage eventually to become dominants. Ultimately in some ecosystems in the late successional stage a relatively constant mix of species is reached, which will last until the

9

next disturbance (Whitehead 1982), although in others especiallyin the temperate zones but also in moist high forest systems (seethe examples from Uganda mentioned above) the climax forests maybe more or less single species.

After a major disturbance to the ecosystem initial growthrates tend to be high and for some pioneer species in the earlysuccessional stages can be very high; these pioneer species arebetter able to respond to site fertility, but are relativelyvulnerable to stress. Subsequently in the later successionalstages as the biomass increases the pioneer species are replacedby more shade tolerant species, which are slower growing, butmore resistant to harmful factors. Eventually the situation maybe reached in late successional stages when biomass may be veryhigh, but growth rates are negligible.

Some ecologists have argued that this final state is theideal climax representing a stable and self sustaining condition- although as noted above it may not be very diverse in terms oftree species. Others have pointed out that it is doubtful if atrue climax is ever attained (Jones 1945), because sooner orlater disturbances occur. The significant point is thatstability in an ecosystem is considered to be attained when thereis an adequate diversity of functions. But a species can havemore than one function and a function can be performed by morethan one species. In industrial plantations stability isachieved when there are no major unprescribed changes in yieldsor production and site fertility and soil structure aremaintained. Even though stability may be dependent to someextent on species diversity, it does not necessarily follow thatthe aim in plantation forestry should be to have as many speciesas possible in order to achieve maximum stability or even thatgreater species diversity must imply greater stability. Theessential for achieving stability is that there should be enoughspecies to achieve an adequate diversity of functions (Zwolinski1990) and the number of species required for stability inindustrial plantations will depend on the site.

The objective in growing plantations for commercial gain isfrequently to take advantage of the high growth rates in theearly stages of succession; in the tropics and sub-tropicsincrements in plantations are three to seven times those of themerchantable species in the later successional stages of thenatural forest (Evans 1990), though this is a consequence ofselection and tree breeding, close spacing and management as wellas the utilization of initial high growth rates. The harvest istaken when, or shortly after, growth starts to slow down. Theact of harvesting causes a major disturbance to the ecosystemwhich allows the cycle to be restarted in the fast growth phaseagain. In commercial plantation forestry the objective is tomaintain the ecosystem in a state of controlled instability,locked in a given successional stage, but experience has shownthat sustainable yields can usually only be maintained with someartificial inputs such as fertilizer, insecticides, fungicidesetc. combined with sound forestry practice

9

next disturbance (Whitehead 1982), although in others especially in the temperate zones but also in moist high forest systems (see the examples from Uganda mentioned above) the climax forests may be more or less single species.

After a major disturbance to the ecosystem initial growth rates tend to be high and for some pioneer species in the early successional stages can be very high; these pioneer species are better able to respond to site fertility, but are relatively vulnerable to stress. Subsequently in the later successional stages as the biomass increases the pioneer spec~es a~e replaced by more shade tolerant species, which are slower growing, but more resistant to harmful factors. Eventually the situation may be reached in late successional stages when biomass may be very high, but growth rates are negligible.

Some ecologists have argued that this final state is the ideal climax representing a stable and self sustaining condition - although as noted above it may not be very diverse in terms of tree species. Others have pointed out that it is doubtful if a true climax is ever attained (Jones 1945), because sooner or later disturbances occur . The significant point is that stability in an ecosystem is considered to be attained when there is an adequate diversity of functions. But a species can have more than one function and a function can be performed by more than one species. In industrial plantations stability is achieved when there are no major unprescribed changes in yields or production and site fertility and soil structure are maintained. Even though stability may be dependent to some extent on species diversity, it does not necessarily follow that the aim in plantation forestry should be to have as many species as possible in order to achieve maximum stability or even that greater species diversity must imply greater stability. The essential for achieving stability is that there should be enough species to achieve an adequate diversity of functions (Zwolinski 1990) and the number of species required for stability in industrial plantations will depend on the site.

The objective in growing plantations for commercial gain is frequently to take advantage of the high growth rates in the early stages of succession; in the tropics and sub-tropics increments in plantations are three to seven times those of the merchantable species in the later successional stages of the natural forest (Evans 1990), though this is a consequence of selection and tree breeding, close spacing and management as well as the utilization of initial high growth rates. The harvest is taken when, or shortly after, growth starts to slow down. The act of harvesting causes a major disturbance to the ecosystem which allows the cycle to be restarted in the fast growth phase again. In commercial plantation forestry the objective is to maintain the ecosystem in a state of controlled instability, locked in a given successional stage, but experience has shown that sustainable yields can usually only be maintained with some artificial inputs such as fertilizer, insecticides, fungicides etc. combined with sound forestry practice

10

If, however, the objective is protection of the site withoutconsideration of commercial profit, then the ecosystem requiredis one that can provide this function, possibly but notnecessarily by progress to a late successional stage. Theobjective will be fully met if the ecosystem can be made self-sustaining, possibly by retaining a wide range of species.

Management, aimed mainly the conservation of biologicaldiversity, implies the retention of the maximum number of speciesand within-species diversity, and furthermore it requires themaintenance of all successional stages in the ecosystem.Maintaining an ecosystem, however, does not necessarily mean theconservation of all its species, and it is possible to conservea species and lose genetically distinct populations or geneswhich may be of value in adaptation and future improvement of thespecies (Wilcox, 1982).

In plantation forestry,particularly where rotations areshort, some trade offs have to be made. Gains in yields may beoffset by negative factors such as the removal of nutrients inlogging, a reduction in nutrient cycling ability, damage to thesoil structure or a possible lowering of resistance to pests anddiseases, which have to be made good if yields are to besustained. Skill is required to determine how to minimise theselosses by matching species to site and by good forestry practicesand to determine where, how and when natural processes (such asthe regeneration of an understorey) can and should be used andto what extent they should be supplemented artificially. Mixedplanting does play a role and should be based on accurateobservation of local succession, where this information isavailable. But if short rotation forestry is an acceptable usefor a site, mixed planting by itself cannot be a panacea for theproblems associated with commercial forestry. The shorter therotation, the closer the situation approaches to that of anagricultural crop and the greater becomes the importance of soilfertility (Lundgren 1980) and the more likely that fertilizerswill have to be added.

10

If, however, the objective is protection of the site without consideration of commercial profit, then the ecosystem required is one that can provide this function, possibly but not necessarily by progress to a late successional stage. The objective will be fully met if the ecosystem can be made self­sustaining, possibly by retaining a wide range of species.

Management, aimed mainly the conservation of biological diversity, implies the retention of the maximum number of species and within-species diversity, and furthermore it requires the maintenance of all successional stages in the ecosystem. Maintaining an ecosystem, however, does not necessarily mean the conservation of all its species, and it is possible to conserve a species and lose genetically distinct populations or genes which may be of value in adaptation and future improvement of the species (Wilcox, 1982) .

In plantation forestry,particularly where rotations are short, some trade offs have to be made. Gains in yields may be offset by negative factors such as the removal of nutrients in logging, a reduction in nutrient cycling ability, damage to the soil structure or a possible lowering of resistance to pests and diseases, which have to be made good if yields are to be sustained . Skill is required to determine how to minimise these losses by matching species to site and by good forestry practices and to determine where, how and when natural processes (such as the regeneration of an understorey) can and should be used and to what extent they should be supplemented artificially. Mixed planting does play a role and should be based on accurate observation of local succession, where this information is available . But if short rotation forestry is an acceptable use for a site, mixed planting by itself cannot be a panacea for the problems associated with commercial forestry. The shorter the rotation, the closer the situation approaches to that of an agricultural crop and the greater becomes the importance of soil fertility (Lundgren 1980) and the more likely that fertilizers will have to be added.

3. ENVIROMENIAL IMPACT.

3.1 SOILS

One of the major concerns expressed concerning the risk of creatingmonospecific plantations is that they cause a loss of fertility and soildegradation. The main features of soils onwhich afforestation in the tropicsand subtropics mcstly takes place and the interaction between tree crops andthe soil is discussed in detail in Appendix II.

Soil characteristics

Soils available for afforestation in the tropics and sub-tropics areoften intensely weathered and frequently deficient in nutrients, bit even whenthey are less weathered they are liable to loss of nutrients through leaching.In the wet tropics these soils can support a heavy biomass by virtue of therapid decomposition of the litter and mineralization of nutrients In thetopmost layers of the soil. On clearing the vegetation for agriculturalcrops or for establishing tree crops there is a high risk of loss of organicmatter, leaching and the loss of this fertility. It is important that thesesensitive sites are not cleared; on sites that have became badly degraded thefirstpriority must be to re-establish the organicmatter content of the soil.In the arid and semi-arid zones the litter layer and organic content of thesoil maybe further depleted by fires and as a result the natural climax treespecies tend to be fire resistant, bit the sites only carry a low stockingbecause they are infertile.

The ability of trees to take up nutrients is determined not only bytheir availability in the topsoil bit also by soil moisture and the soilstructure. The requirements for each nutrient vary with the stage ofdevelopment of the stand; it tends to be at a maximum imediately after crownclosure in plantations . For Safe nutrients, phosphate in particular, the rateof release fram mineral soil is slaw. The quantity in solution available atanyone time for use hythe trees is very small in comparison with the annualrequirement of the trees and with the quantities locked up in the tree biomassand in the litter on the forest floor. In these conditions healthy, vigorousgrowth is dependent on rapid decomposition of the litter to maintain thenutrient cycle.

The process of decomposition is closely associated with the activitiesof the soil microfauna and flora. The function of soil microfauna and florahave not been studied in the tropics andsub-tropics as closely-as they havebeen in the temperate zones. But it is clear that microfauna fragment and insame instances (for example termites) mineralize litter; the process iscampletedbyfungi and more particularlyby bacteria. The mixture of speciescomposing a stand, by influencing both the proportion of cellulose and proteinin the litter and the soil acidity, can be of great significance in affectingthe populations of the soil microfauna and flora and their performance and achange in the composition of the leaf littermay favour one component of themicroflora at the expense of another.

Sane symbiotic fungi can not only exist in association with one speciesin a mixture, bit can also benefit other components of a stand; for examplein Britain Suillus variega tus on Pinussylvestris can make available nutrientswhich can be used by Picea abies (Ryan and Alexander 1990). In Swaziland ithas been found that at higher altitudes considerable quantities of needle

1111

3. ElIVIKHmf.rAL IMPACT.

3.1 SOILS

One of the major =cems expressed =ceming the risk of creating llOIlospecific plantations is that they cause a loss of fertility and soil degradation. The main features of soils on which afforestation in the tropics and subtropics IOClStly takes place and the interaction between tree crops and the soil is discussed in detail in Appendix II .

Soil cbaracteristics

Soils available for afforestation in the tropics and sub-tropics are often intensely weathered and frequently deficient in nutrients, rut even when they are less weathered they are liable to loss of nutrients through leaching. In the ¥let tropics these soils can support a heavy bianass by virtue of the rapid dea:iuposition of the litter and mineralization of nutrients in the toprost layers of the soil. On clearing the vegetation for agricultural crops or for establishing tree crops there is a high risk of loss of organic matter, leaching and the loss of this fertility. It is ilIportant that these sensitive sites are not cleared; on sites that have becane badly degraded the first priority llU.lSt be to re-establish the organic matter =tent of the soil. In the arid and semi -arid zones the litter layer and organic =tent of the soil may be further depleted by fires and as a result the natural climax tree species tend to .be fire reSistant, rut the sites only carry a low stocking because they are infertile.

The ability of trees to take up nutrients is determined not only by their availability in the topsoil rut also by soil llOisture and the soil structure. The requira:rents for each nutrient vary with the stage of developrent of the stand; it tends to be at a maxilm.lm i1lInediately after crown closure in plantations. For sate nutrients, phosphate in particular, the rate of release fran mineral soil is slow. The quantity in solution available at anyone time for use by the trees is very small in carparison with the annual require:rent of the trees and with the quantities locked up in the tree bianass and in the litter on the forest floor. In these conditions healthy, vigorous growth is dependent on rapid decanposition of the litter to maintain the nutrient cycle.

The process of decanposition is closely associated with the activities of the soil microfauna and flora. The function of soil microfauna and flora have not been studied in the tropics and sub-tropics as closely as they have been in the temperate zones. But it is clear that microfauna fragment and in sane instances (for exanple termites) mineralize litter; the process is CCIlpleted by fungi and llOre particularly by bacteria. The mixture of species canposing a stand, by influencing both the proportion of cellulose and protein in the litter and the soil aCidity, can be of great significance in affecting the populations of the soil microfauna and flora and their perfonnance and a change in the canposition of the leaf litter may favour one CCIlpOnent of the microflora at the expense of another .

Sane symbiotic fungi can not only exist in association with one species in a mixture, rut can also benefit other a::nponents of a stand; for exanple in Britain Suillus variegatus on Pinus sylvestris can make available nutrients which can be used by PiC£Ja abies (Ryan and Alexander 1990). In SWaziland it has been found that at higher altitudes considerable quantities of needle

12

litter can build up under Pinus patula maintained at a close spacing (Morris1986); in these circumstances the formand numbers of mycorrhizae may change(Robinson 1973). It is observable that the problem of litter accumulation isparticularly acute in close canopy softwood conifer stands in the tropics andsub-tropics, but is less of a problem in open stands having an understorey ofbroadleaf species; in effect the mixture of species provided by theunderstorey promotes the breakdown of forest floor litter.

Concern has been expressed at the effect on the soil of close plantingof pure stands of teak. The problem is that teak is deciduous and the leaves,which do not readily decompose, are highly inflammable; as a result fires arefrequent in teak plantations on sites having a pronounced dry season and inconsequence the forest floor in plantations is frequently bare at the startof the rains. Additionally the leaves of teak are large and the drip from theleaves on the tree intensifies the erosive effect. Planting teak at widerspacing and either planting a mixture of other species with more easilydecomposed and less inflammable leaves or allowing shrUb or herb species tocome in as an understorey reduces the incidence of fire and erosion (Bell1963).

Though mcst of the nutrients in the topsoil are derived from mineralsin the subsoil or fram litter, sane nutrients are accumulated in the topsoilfrom the atmosphere. Nitrogen fixation in the roots of sane plants is anexample of this process. This process is chiefly associated with legumes, butfixation of nitrogen can occur in over 200 species from 20 genera (Bond 1983),of which Casuarina is probably the most significant non-legume tropical tree.Nitrogen fixation can operate as a direct transfer from the root nodules tothe soil, but the most common pathway appears to be through the leaf litter(El 1986). In Hawaii the nitrogen fixing effect of Adbizia falcataria onsoil nitrogen levels was much greater than that of Acacia aelanoxylorn (DeBellet al 1985), which may be because A.falcataria has a much smaller and moreeasilydecomposed leaf. It should be noted, however, that the very favourableeffects of mixingAlbizia falcataria with Eucalyptus saligna in Hawaii (DeBellet al 1985; 1987; 1989) was achieved on old sugar cane fields, where pastfertilizing regimes and the nutrient demands of the sugar cane crop may haveresulted in unique soil nutrient conditions.

For nitrogen fixing plants to make a positive contribution to standgrowth the site conditions must be suitable; that is there must not only bea deficiency of nitrogen but other nutrients, especially phosphate, andmoisture (Sprent 1985) must also not be limiting. On sites where nitrogen isnot deficient it has been shown that an admixture of nitrogen fixing treesdoes not enhance growth of the main species and may even inhibit it throughcompetition for light, moisture or other nutrients (Binkley 1983; 1984; 1990).It is possible that nitrogen fixing trees are only effective when they aredominants or codominants (Binkley 1990), so there is doubt concerning theeffectiveness of nitrogen fixing species grown as an understorey. Ittherefore appears that there is a comparatively narrcm range of conditions inwhich nitrogen fixing plants will enhance stand growth. The beneficialeffects of mixtures with nitrogen fixing trees, such as acacias in pinestands, are not always apparent (Turvey et al 1984).

12

litter can ruild up under Pinus patula maintained at a close spacing (M:)rris 1986); in these circumstances the fom and numbers of mycorrhizae may change (Robinson 1973). It is ol:servable that the problem of litter aCCUllRllation is particularly acute in close canopy softwood conifer stands in the tropics and sub-tropics, rut is less of a problem in open stands having an understorey of broadleaf species; in effect the mixture of species provided by the understorey promotes the breakdown of forest flcor litter.

Concern has been expressed at the effect on the soil of close planting of pure stands of teak. The problem is that teak is deciduous and the leaves, which do not readily decanpose, are highly inflanrnable; as a result fires are frequent in teak plantations on sites having a pronounoed dry season and in consequence the forest floor in plantations is frequently bare at the start of the .rains. Additionally the leaves of teak are large and the drip fran the leaves on the tree intensifies the erosive effect. Planting teak at wider spacing and either planting a mixture of other species with more easily decanposed and less inflammable leaves or allowing shrub or herb species to a::rne in as an understorey reduces the incidence of fire and erosion (Bell 1963) .

Though most of the nutrients in the topsoil are derived fran minerals in the subsoil or fran litter, saoo nutrients are accumulated in the topsail fran the atmosphere. Nitrogen fixation in the roots of sare plants is an example of this process. This process is chiefly associated with legumes, rut fixation of nitrogen can oc= in over 200 species fran 20 genera (Bond 1983), of which casuarina is probably the most significant non-legume tropical tree . Nitrogen fixation can operate as a direct transfer fran the root nodules to the soil, rut the most CCIlII011 pathway appears to be through the leaf litter (Ewel 1986) . In Hawaii the nitrogen fixing effect of Albizia falcataria on soil nitrogen levels was much greater than that of Acacia melanoxylon (DeBell et al 1985), which may be because A.falcataria has a much smaller and more easily decanposed leaf . It should be noted, however, that the very favourable effects of mixing Albizia falcataria with Eucalyptus saligna in Hawaii (DeBell et al 1985; 1987; 1989) was achieved on old sugar cane fields, where past fertilizing reg:ilres and the nutrient demands of the sugar cane crop may have resulted in unique soil nutrient conditions.

For nitrogen fixing plants to make a positive contribJ.tion to stand grCMth the site conditions must be suitable; that is there must not only be a deficiency of nitrogen rut other nutrients, especially phosphate, and moisture (Sprent 1985) must also not be limiting . On sites where nitrogen is not deficient it has been shown that an admixture of nitrogen fixing trees does not enhance grCMth of the main species and may even inhibit it through ~tition for light, moisture or other nutrients (Binkley 1983; 1984; 1990) . It is possible that nitrcigen fixing trees are only effective when they are daninants or codaninants (Binkley 1990), so there is doubt concerning the effectiveness of nitrogen fixing species grown as an understorey. It therefore appears that there is a carparatively narrow range of conditions in which nitrogen fixing plants will enhance stand growth . The beneficial effects of mixtures with nitrogen fixing trees, such as acacias in pine stands, are not always apparent (TUrveyet al 1984).

13

EVidence for changes in site paraneters reflected in second rotation yielddecline

The species composition of a natural stand or of a plantation have astrong influence on the site, and particularly on soil properties. Aplantation of a single species may alter the nutrient status or the physicalproperties of a soil from its original state under natural forest; this changemay reduce both the actual and potential productivity of the site as well asthe composition of the understorey or undergrowth. On the other hand aplantation of a single species may have a positive effect on the soil if itis established where there was no cover. If therefore there are changes insite properties these may be expected to be reflected indifferences ingrowthand yield in the second and subsequent generations fram the first - althoughsuch changes could be the result of different management practices ordifferent seed as well as the result of a dhange in species composition or ofa shift to a single species.

The concern over the possibility of second (and subsequent) rotationdecline is chiefly based on two experiences, that of spruce (Picea abies) inCentral Europe and specifically in Saxony, starting in the middle of thenineteenthcentury, and that of Rinus radiata in South Australia in the middleof the twentieth century. In addition detailed graoith records fram PermanentSample Plots, which now span three rotations, have been maintained in theUsutu plantations in Swaziland. In order to understand the phenamenon ofsecond rotation decline it is worth examining these experiences in samedetail.

(a) Spruce in Saxony.

Spruce was planted in central Europe on a large scale in pure blocksfrom the middle of the eighteenth century partly because decline was thoughtto have been detected in the beech and oak forests. Spruce had always beengraan satisfactorily as a pure crop on the higher elevation podsols and indeedoccurs naturally in pure stands, bit bythe middle of the nineteenth centurya decline in yields was observed in particular on the lowland clay soils.This decline in yield was attributed to the repeated establishment of purespruce stands. In the nineteen twenties Wiedemann made extensiveinvestigations into the problem in Saxony (summarised in Jones 1965). Partlybecause the analytic procedures available at the time were inadequate he wasnever able to pinpoint the cause of the problem. He did note that not allspruce plantations were affected, that in same the growth was chedked bit itlater recovered and that there was same correlation with dry summers. As aresult of his and subsequent work same of the confounding factors have beenidentified and possible causes of the problem suggested. These include

on clay soils the spruce is very shallua rooting; in the first rotationit can often make use of old root lines, bit by the second rotationthese have silted up and the spruce is rooted almost entirely in thehumus layer which dries out in droughts and may became water-logged inwinter.much of the planting was on old arable land or cultivated plots in theforest - waldféldbau; spruce is notoriously susceptible to the root rot

13

EVidence far changes in site parameters reflected in second rotation yield decline

The species CXIIifXJSition of a natural stand or of a plantation have a strong influence on the site, and particularly on soil properties. A plantation of a single species may alter the nutrient status or the physical properties of a soil fran its original state under natural forest; this change may reduce l:oth the actual and potential productivity of the site as well as the cx::rrposition of the understorey or undergrc:Mth. On the other hand a plantation of a single species may have a positive effect on the soil if it is established where there was no cover. If therefore there are changes in site properties these may be expected to be reflected in differences in gr=th and yield in the second and sul:x3equent generations fran the first - although such changes oould be the result of different management practices or different seed as well as the result of a change in species CXIIifXJSition or of a shift to a single species .

The concern over the possibility of second (and sul:x3equent) rotation decline is chiefly based .on b;o experiences, that of sp=ce (PiCEa abies) in Central Europe and specifically in Saxony, starting in the middle of the nineteenth century, and that of Pinus radiata in South Australia in the middle of the twentieth century. In addition detailed gr=th records fran Pennanent Sarrple Plots, which n= span three rotations, have been maintained in the Usutu plantations in SWaziland. In order to understand the phenaoonon of second rotation decline it is worth examining these experiences in sane detail .

(a) Sp=ce in Saxony.

Sp=ce was planted in central Europe on a large scale in pure blocks fran the middle of the eighteenth century partly because decline was thought to have been detected in the beech and oak forests. Sp=ce had always been grown satisfactorily as a pure crop on the higher elevation podsols and indeed occurs naturally in pure stands, rut by the middle of the nineteenth century a decline in yields was observed in particular on the l=land clay soils. This decline in yield was attriJ::uted to the repeated establishttent of pure spruce stands. In the nineteen twenties Wiedemann made extensive investigations into the problem in Saxony (sUlllllarised in Jones 1965) . Partly because the analytiC procedures available at the time were inadequate he was never able to pinpoint the cause of the problem . . He did note that not all sp=ce plantations were affected, that in sane the gr=th was checked rut it later recovered and that there was sane correlation with dry S\lllll"ers. As a result of his and sul:x3equent work sane of the confounding factors have been identified and possible causes of the problem suggested. These include

on clay soils the sp=ce is very shall= rooting; in the first rotation it can often llI3ke use of old root lines, rut by the second rotation these have silted up and the sp=ce is rooted alrrost entirely in the h1millS layer which dries out in droughts and may becane water-logged in winter. IlUlch of the planting was on old arable land or cultivated plots in the forest - waldfeldbau; sp=ce is notoriously susceptible to the root rot

14

Fans annosusl in these circumstances, hit it takes up to a rotationfor the effects of the fungus to become apparent since it entersthrough freshly-cut stumps and then through root grafts to livingtrees. Hence what was in fact a problem of the first rotation was onlymanifested in the second rotation.the soils on many of the sites had already been impoverishedbefore thespruce was established as a result of the prevailing custam ofcollecting all the litter beneath the previous stands.management practices at the time favoured very dense stands whichtended to cause an accumulation of litter which in turn impairednitrogen mineralization.

Thus there is a range of possible explanations, which taken togethercould account to a great extent for the check in growth. A point ofsignificance is that the problem was most apparent where spruce was plantedoff its natural site on the lowland clay soils. Unfortunately there hastended to be an uncritical acceptance of the initial explanation thatattributed the phenomenon of spruce check to the use of monocultures. In factthis explanation connected unrelated events as cause and effect which has ledto pure spruce frequently being equated to a pure crop of any conifer and evento a pure crop of any species (Jones 1965).

?re recently it has been claimed that for middle age classes of Piceaabies in Germany, despite the occurrence of needle loss and crown decline,yields are 20% to 40% higher than anticipated; this has been attributed toincreased temperature, increased rainfall and CO2 and higher mineralization(Kenk 1990b).

(b) Pinus radiata in South Australia.

P.radiata had been planted on infertile sandysoils in South Australia.The first rotation was felled at about 25 years of age and produced reasonableyields. When the second rotation was about ten years old it became apparentfram the analysis of permanent sample plots that the plantations had droppedone or two and sometimes even three Site Quality (SQ) Classes (Keeves 1966).Each quality class represented 140 NO/ha at rotation age; SQ VII had astanding volume of about 5 000 ft3/ac (350 m3/ha) and SQ IV 11 000 ft3/ac (770NO/ha). This was therefore a serious loss. There was some indication thatyield decline had not occurred in stands where slash arising from clearfelling had not been burnt and natural regeneration had taken. place. Burningbefore replanting was normal practice.

Overthe next two decades research was directedto the decline in yield.The soils are coarse sands of poor water holding capacity, from whichnutrients are easily leached. It was found that particular attention neededto be paid to the interaction between water availability and nutrient supply.The maintenance of the organic matter content of the topsoil was crucial tothis relationship (Sands 1983). Not only did organicmatter increase nitrogenavailability and the cation exchange capacity, hit it also reduced bulkdensity and increased the field capacity; in the absence of sufficient waterthe trees were unable to make use of nutrients even when they were available(Boardman 1982). Second rotation yield decline was thus associated with l.1

Mbre correctly heterobasidicn annosum hit generally recognised byforesters under its old narre.

14

Ftznes annosus' in these circumstances, rut it takes up to a rotation for the effects of the fungus to bea:Jne apparent since it enters through freshly-cut stumps and then through root grafts to living trees . Hence what was in fact a problem of the first rotation was only manifested in the second rotation. the soils on many of the sites had already been impoverished before the spruce was established as a result of the prevailing custan of collecting all the litter beneath the previous stands . managanent practices at the t:iJre favoured very dense stands which tended . to cause an aCClmUllation of litter which in turn impaired nitrogen mineralization .

Thus there is a range of possible explanations, which taken together could aCCO\IDt to a great extent for the check in growth. A point of significance is that the problem was lOOSt apparent where spruce was planted off its natural site on the laYland clay soils . Unfortunately there has tended to be an un=itical acceptance of the initial explanation that attrib..lted the phenanenon of spruce check to the use of lOClllOCUltures . In fact this explanation connected unrelated events as cause and effect which has led to pure spruce frequently being equated to a pure crop of any conifer and even to a pure crop of any species (Jones 1965) .

More recently it has been cla:iJred that for middle age classes of Picea. abies in Gennany, despite the occurrence of needle loss and crown decline , yields are 20% to 40% higher than anticipated; this has been attrib..lted to increased t~rature, increased rainfall and CO

2 and higher mineralization

.(Kenk 1990b).

(b) Pinus radiata in SOuth Australia .

P.radiata had been planted on infertile sandy soils in SOuth Australia. The first rotation was felled at about 25 years of age and produced reasonable yields . When the second rotation was about ten years old it became apparent fran the analysis of pennanent sarrple plots that the plantations had dropped one or t= and serret:iJres even three Site Q.Jality (SQ) Classes (Keeves 1966). Each quality class represented 140 m3jha at rotation age; SQ VII had a standing volume of about 5 000 ft3/ac (350 m3jha) and SQ N 11 000 ft'/ac (770 m3jha) . This was therefore a serious loss . There was serre indication that yield decline had not occurred in stands where slash arising fran clear felling had not been b..lrnt and natural regeneration had taken place. Burning before replanting was nonnal practice.

OVer the next t= decades research was directed to the decline in yield. The soils are coarse sands of poor water holding capacity, fran which nutrients are easily leached . It was found that particular attention needed to be paid to the interaction between water availability and nutrient supply. The Ill3.intenance of the organic matter content of the topsoil was crucial to this relationship (Sands 1983) . Not only did organic matter increase nitrogen availability and the cation exchange capacity, rut it also reduced rulk density and in=eased the field capacity; in the absence of sufficient water the trees were unable to make use of nutrients even when they were available (Boardman 1982) . Second rotation yield decline was thus associated with laY

1 More correctly Heterobasidion annasum rut generally recognised by foresters under its old name .

15

nutriett status, layq moisture availability and loss of organic matter from-thesoil as well as soil compaction and weed competition (TUrner 1983; Squire1983).

The solution to the problem lay in good forestrypractice, that is, thepreparation of the site with more care, the elimination of burning, theretention of branches as a mulch after felling and the reduction ofcompetition from other species. The phased application of fertilizer wasintroduced in order to overcome the tendency to leaching in the sandy soilsand in order to maintain the supply of nutrients at times of peak demand; thiswas found to be well suited to the P..radiata rooting habit (Boardman 1982).These practises coMbined with genetic selection for vigour have resulted ina general second rotation gain in yields.

It is claimed that no studies have shown that nutrient removals inlogging or conversion to pine have led to productivity decline in SouthAustralia (TUrner 1983). The problem of second rotation decline in Australiais confined to soils of low nutrient status. On heavy relatively fertileclays ínNew South Wales P.radiata was thought to have improved the site indexfrom H of 60m in the first rotation to HumM of 70 or 80 m in the second

cizrn(20) .

rotation MUir 1970).

The points of significance appear to be that:

the problem was noticed as a result of measurements of Permanent SamplePlots, which were first established in 1935 (Boardman 1988);

the problem occurs on difficult soils with low initial nutrient statusand law water holding capacity;

there were adequate resources to research the prbblem and find ananswer;

the potential for second rotation decline on infertile soils exists;the solution consists largely in good forestry practice to conserve thesoil moisture content and to maintain the organic content of the soilbacked up by repeated applications of fertilizer adjusted to the crop'srequirements at each stage of development.

(c) Usutu plantations, Swaziland.

Monitoring of the Usutu plantations, which have primarily beenestablishedtoPinuspatula, with some P. elliottii andP.taeda, started in thelate nineteen sixties Early in the second rotation Permanent Sample Plotswere established which have been monitored ever since. Sane sites are nicarryingtheir third rotation of pine (Evans 1975,1988). In 1983 an intensivesoil survey was undertaken (Murris 1986).

The findings of the soil survey are discussed in more detail in Appendix2. Of particular note is the fact that whereas most of the area overliesgranites, 15% of the plantation area is on the Usushwana complex soilsoverlying gabbro, and these soils are seriously deficient in phosphates.Unless corrective measures are taken yield declines are highly likely on theUsushwana soils.

15

nutrient status, 1= lIOisture availability and loss of organic matter fran the soil as well as soil c:atq?action and weed canpetition (Turner 1983; Squire 1983) .

The solution to the problem lay in good forestry practice, that is, the preparation of the site with IIOre care, the elimination of I:::uming, the retention of branches as a mulch after felling and the reduction of canpetition fran other species. The phased application of fertilizer was introduced in order to overa::ma the tendency to leaching in the sandy soils and in order to maintain the supply of nutrients at times of peak demand; this was found to be well suited to the P.radiata rocting habit (BoaIdrran 1982). These practices cx:mbined with genetic selection for vigour have resulted in a general second rotation gain in yields.

It is cl.ainEd that no studies have shown that nutrient rem:>vals in logging or conversion to pine have led to productivity decline in South Australia (Turner 1983). The problem of second rotation decline in Australia is confined to soils of 1= nutrient status. On heavy relatively fertile clays in New South Wales P.radiata was thought to have inproved the site index fran Hcbn(20) of 60 In in the first rotation to Hcbn(20) of 70 or 80 In in the second rotation tM..!ir 1970).

The points of significance appear to be that:

the problem was noticed as a result of measurements of Pennanent Sarrple Plots, which were first established in 1935 (BoaIdrran 1988);

the problem occurs on difficult soils with 1= initial nutrient status and 1= water holding capacity;

there were adequate resources to research the problem and find an answer;

the potential for second rotation decline on infertile soils exists; the solution consists largely in good forestry practice to conserve the soil rroisture content and to maintain the organic content of the soil backed up by repeated applicatiOns of fertilizer adjusted to the crop's requirarents at each stage of develoJm2l1t.

(c) Usutu plantations, swaziland.

M:mitoring of the Usutu plantations, which have primarily been established to Pinus patula, with sane P.elliottii and P. taeda, started in the late nineteen sixties. Early in the second rotation Pennanent Sarrple Plots were established which have been llOnitored ever since. scme sites are nCM

carrying their thil:d rotation of pine (Evans 1975,1988). In 1983 an intensive soil survey was undertaken (M::lrris 1986).

The findings of the soil survey are discussed in rrore detail in Appendix 2. Of particular note is the fact that whereas rrost of the area overlies granites, 15% of the plantation area is on the Usushwana ccmplex soils overlying gabbro, and these soils are seriously deficient in phosphates. Unless corrective measures are taken yield declines are highly likely on the Usushwana soils.

16

The Usutu plantations lie between about 1000 m and 1450 m altitude;above about 1350 m there is a problem of litter accumulating on the forestfloor on both granite soils and on soils of the Usushwana complex. Theimmobilisation of nutrients in the litter layer caMbined with their loss atharvesting might result in a deficiency of nutrients, especially nitrogen,phosphate and potassium. At one time it was the practice to burn branches,tops and also needle litter after clear felling, but this has beendiscontinued since 1973, because it was associated with subsequent attacks ofthe pathogen Rtizina undulata. But there is, however, evidence that whenburning is not practised the accumulation of litter under second rotationcrops is much greater, though the loss of nitrogen and sulphur to theatmosphere is reduced. Analysis of the growth records and the PermanentSample Plots at Usutu has confirmed that on the Usushwana complex soils ayield decline occurs in the third rotation, of about 30%, but trials haveindicated that plantations on these sites will respond to P fertilizer, whichmay resolve the problem .

The analysis of growth records from the plantations on soils derivedfrom granites has proved to be more complicated. The (arly figures for secondrotation growth indicated a faster rate in the first two years in comparisonto the first rotation and then a slower rate over the next four years or so.This was explained by two facts. First, in the second rotation the trees wereestablished onto weed free sites. Second, there had been a series of yearswith low rainfall at planting time in the second rotation; Usutu receives onlyjust enough rain to support .P.patula and therefore drought years have acritical effect on yields (Evans 1975).

Results are na0.7 available for second rotation crops at twelve years ofage and for up to six years in the third rotation. In the second rotationplots there were non-significant declines of 8% on the Usushwana complex and4% on granites. Second rotation P.elliottii showed a non-significant drop inheight of .36m (fram 15.57 n) at age twelve. In the third rotation, althoughthere has been the marked decline in yields on the Usushwana complex soilsnoted above, on one set of plots on a small area over granite there has beena significant gain of 21% over second rotation yields, while on the largerarea there WaS a non-significant gain of 4%. The general conclusion is thaton the granite soils, even after allowance is made for yield increasesattributable to improved genetic materials and improved establishmenttechniques, no yield decline has been detected (Evans 1988).

The points of importance appear to be:

that a system of Permanent Sample Plots has been set up so that it ispossible to monitor growth with precision;

that, whereas it has been indicated that there should be a generalreduction of nutrients with time and in consequence a decline in yields(Morris 1986), it has not been possible to detect this from growthrecords, except on one difficult site;

the prOblem of litter accumulation at higher altitudes remainsunresolved and could be a cause of nutrient depletion in Rpatulastands.

16

The Usutu plantations lie between about 1000 rn and 1450 rn altitude; above about 1350 rn there is a problem of litter accumulating on the forest floor on both granite soils and on soils of the Usushwana canplex. The ilmobilisation of nutrients in the litter layer CCIlIbined with their loss at harvesting might result in a deficiency of nutrients, especially nitrogen, phosphate and potassium. At one time it was the practice to I:m:n branches, tops and also needle litter after clear felling, rut this has been discontinued since 1973, because it was associated with subsequent attacks of the pathogen Rhizina undulata. But there is, hcMever, evidence that when I:m:ning is not practised the accumulation of litter under second rotation crops is much greater, though the loss of nitrogen and sulphur to the atmosphere is reduced. Analysis of the grcMth records and the Pennanent Sarrple Plots at Usutu has confinrvad that on the Usushwana canplex soils a yield .decline occurs in the third rotation, of about 30%, rut trials have indicated that plantations on these sites will respond to P fertilizer, which may resolve the problem .

The analysis of grcMth records fran the plantations on soils derived fran granites has proved to be IOClre canplicated. The early figures for second rotation grcMth indicated a faster rate in the first two years in canparison to the first rotation and then a slower rate over the next four years or so. This was explained by two facts. First, in the second rotation the trees were established onto weed free sites . Second, there had been a series of years with l~ rainfall at planting time in the second rotation; Usutu receives only just enough rain to support P.patula and therefore drought years have a critical effect on yields (Evans 1975).

Results are n~ available for second rotation crops at twelve years of age and for up to six years in the third rotation. In the second rotation plots there were non-significant declines of 8% on the Usushwana canplex and 4% on granites. Second rotation P.elliottii shoNed a non-significant drop in height of .36 rn (fran 15.57 rn) at age twelve. In the third rotation, although there has been the marked decline in yields on the Usushwana canplex soils noted above, on one set of plots on a small area over granite there has been a significant gain of 21% over second rotation yields, while on the larger area there was a non-significant gain of 4%. The general conclusion is that on the granite soils, even after all~ce is made for yield increases attrirutable to improved genetiC materials and improved establishment techniques, no yield decline has been detected (Evans 1988).

The points of importance appear to be:

that a system of Pennanent Sarrple Plots has been set up so that it is possible to monitor grcMth with precision;

that, whereas it has been indicated that there should be a general reduction of nutrients with time and in consequence a decline in yields (Morris 1986), it has not been possible to detect this fran ~h records, except on one difficult site;

the problem of litter aCCUllUllation at higher altitudes ranains unresolved and could be a cause of nutrient depletion in P.patula stands.

17

(d) Conclusion on second rotation yield decline.

There is a role for mixtures in soil management, bit insofar as secondrotation yield decline reflects changes in site properties, the evidencesuggests that it is a potential problem on infertile soils and on same othersites, but that on these sites yield decline can be controlled by goodforestry practice, in particular the matching of species to site, and theapplication of fertilizer to correct nutrient deficiencies. Although onfertile sites it may not yet be possible to obtain statistically significantevidence of yield decline, soil scientists have provided sufficient evidenceof the likelihood of a loss of nutrients (Lundgren 1980; Morris 1986; Young1976) that foresters cannot afford to be complacent. The need for soilconservation is evident, especially through the avoidance of compaction byheavymachinery or exposure of the soil byburning. These are not necessarilyproblems of growing plantations as single species or in mixtures of species.

The importance of Permanent Sample Plots as a tool to help in thedetection of yield Changes has been stressed in this study. But declines inyields may not be detected until well into the rotation or even into thefollowing rotation because of problems in sampling and interpretation (Ryan1985). Silvicultural practices which are likely to deplete the topsoil ofnutrients, moisture or organic matter must be avoided on all sites.

The role of mixtures in soil management.

The situations in which mixtures might be recommended appear to be asfollows.

(a) Ground cover.

The introduction of a matrix of trees or shrubs that will provide quidkground cover is often desirable on sites where it is important that soils arenot left exposed for long periods, in the plantation establishment phase, dueto the risks of erosion. But often the same effect can be obtained with non-woody legumes, sudh as lupins, or by allowing suitable herbs or shrubs tocolonize the site temporarily. A situation in which it is important that thesoil is not exposed is most likely to occur on rainforest sites. If

protection and conservation of the soil is of critical importance, then it isprobable that the site is unsuitable for clearing and consideration should begiven to enrichment planting. On sane sites, sudh as coarse sands, groundcover may be better achieved using mulches of plant residues after clearingthe site or after clear-felling; the balancing of the need to protect the soilby encouraging ground cover on the one hand and to reduce competition byweeding on the other requires knowledge of the site.

Irrespective of species composition, sane management regimes, whichinvolve the destruction or removal of litter, for example as a result of theuse of bulldozers to clear the site, or as a consequence of burning slash orthrough collection of litter for livestodk bedding or as fuel, are likely tocause a marked reduction of organic matter in the topsoil. This has anadverse effect on cation exchange capacity, water availability and soilstructure with a consequent risk of erosion. Teak plantations in India,Indonesia and Trinidad or eucalypt plantations on steep slopes in Ethiopia aresome examples. These problems are primarily of administration and protectionthan species selection or composition.

17

(d) Conclusion on second rotation yield decline.

There is a role for mixtures in soil managemant, rut insofar as second rotation yield decline reflects changes in site properties, the evidence suggests that it is a potential problem on infertile soils and on sare other sites, rut that on these sites yield decline can be oontrolled by good forestry practice, in particular the matching of species to site, and the application of fertilizer to correct nutrient deficiencies. Although on fertile sites it may not yet be possible to obtain statistically significant evidence of yield decline, soil scientists have provided sufficient evidence of the likelihood of a loss of nutrients (Lundgren 1980; M::>=is 1986; Young 1976) that foresters cannot afford to be carplacent. The need for soil conservation is evident, especially through the avoidance of carpaction by heavy machinery or exposure of the soil by J::urning. These are not necessarily problems of grcMing plantations as single species or in mixtures of species.

The inportance of Permanent Sarrple Plots as a tool to help in the detection of yield changes has been stressed in this study. But declines in yields may not be detected until well into the rotation or even into the following rotation because of problems in sarrpling and interpretation (Ryan 1985). Silvicultural practices which are likely to deplete the topsoil of nutrients, llOisture or organic matter must be avoided on all sites.

i'be role of mixtures in soil management.

The situations in which mixtures might be rec::cmrended appear to be as follows.

(a) Ground cover.

The introduction of a matrix of trees or shrubs that will provide quick ground oover is often desirable on sites where it is inportant that soils are not left exposed for long periods, in the plantation establishm=nt phase, due to the risks of erosion. But often the sane effect can be obtained with non­woody legumes, such as lupins, or by allowing suitable herbs or shrubs to colonize the site tetrp:Jrarily. A situation in which it is inportant that the soil is not exposed is IlOSt likely to oc= on rainforest sites. If protection and conservation of the soil is of critical inportance, then it is probable that the site is unsuitable for clearing and consideration should be given to enrichm=nt planting. On sare sites, such as coarse sands, ground cover may be better achieved using Imllches of plant residues after clearing the site or after clear-felling; the balancing of the need to protect the soil by encouraging ground cover on the one hand and to reduce carpetition by weeding on the other requires knowledge of the site.

Irrespective of species carposition, sare managemant regimes, which involve the destruction or reroval of litter, for ex.arrple as a result of the use of rulldozers to clear the site, or as a consequence of J::urning slash or through collection of litter for livestock J:x:dding or as fuel, are likely to cause a marked reduction of organic matter in the topsoil. This has an adverse effect on cation exchange capacity, water availability and soil structure with a consequent risk of erosion. Teak plantatiOns in India, Indonesia and Trinidad or eucalypt plantations on steep slopes in Ethiopia are sare ex.arrples. These problems are prirnaril y of administration and protection than species selection or carposition.

(b) Promotion of litter breakdown.

On sites where there is a risk of a litter build up there is a case forintroducingan admixture of tree species whose leaves are known to be favouredby soil biological agents and which will therefore promote quiCker litterbreakdown and nutrient mineralization. Cordia alliodbla leaves decomposedmore quicklywhen the trees were grown in mixture with other tree species thanas a pure crop (Babbar and Ewel 1989). The same effect can also be achievedby alternating rotations of species tending towards litter accumulation (e.g.conifers on sane sites) with those that pramote its decomposition (e.g. sanebroadleaf species). Sometimes a reduction in stodking will promote thenatural regeneration of a beneficial understorey of small trees, shrubs andherbs, which will achieve the same objective.

Nitrogen fixing.

The introduction of nitrogen fixing species can benefit overall yieldon nitrogen deficient sites IncrPases in soil nitrogen have been noted inHawaii (DeBell et al. 1985), India (Samraj et al 1977), but whether nitrogenfixers grown in semi-shade as an understorey species actually fix muchnitrogen is uncertain.

Conclusions on so_i_Ls

Mary of the soils available for forestry plantations in the tropics andsub-tropics are inherently infertile and are easily degraded.

Sane of the methods used for clearing sites for planting are excessivelydestructive of the soils. These include the use of heavy machinery andindiscriminate use of fire which result in the removal and exposure of the topsoil. Soils under rainforests will be damaged if these techniques are used.It should be noted, however, that many of the forest plantations in therainforest zone are being established on sites that have already beendegraded, and in fact afforestation in the tropics is more usual in grassland,scrUb, savanna woodland or disturbed vegetation than in dense polyspecificforests (Wood & Dawkins 1971).

The maintenance of the topsoil organic content and the rapid recyclingof nutrients by the decomposition of the litter layer on the forest floor areimportant contributors to the maintenance of soil fertility.

Losses of nutrients from exploited plantations are inevitable (throughremoval of biomass at harvesting), but second rotation yield decline shouldonly be expected on nutrient deficient sites and can be corrected. Secondrotation decline is not an inevitable consequence of monospecific plantations.Many of the fertility problems associated with monospecific plantationforestry can be overcame, or at least greatly ameliorated, by good forestrypractice, such as care in the use of clearing techniques, particularly in theuse of heavy machinery and fire, the maintenance of a balance between soilexpasureand control of competition from other species, the avoidance of over-stocking (so that small tree, shrUb and herb strata can develop) and theaddition of supplementary fertilizers. These practices are equallyappropriate whether the plantations are mixed or pure.

Mixed plantations can make a contribution to the management of soilfertility in same circumstances:

1818

(b) Promotion of litter breakdown.

On sites where there is a risk of a litter b..lild up there is a case for introducing an admixture of tree species whose leaves are knCMIl to be favoured by soil biological agents and which will therefore promote quicker litter breakdown and nutrient mineralization . Co:cdia alliodora leaves decarposed rrore quickly when the trees were grCMIl in mixture with other tree species than as a pure crop (Rabrer and Ewel 1989). The sarre effect can also be achieved by alternating rotations of species tending tooards litter aCCllllUllation (e .g. conifers on sema sites) with those that promote its deCCllpOSition (e.g. sema broadleaf species). sanet:ines a reduction in stocking will promote the natural regeneration of a beneficial understorey of small trees, shrubs and herbs, which will achieve the sarre objective.

Nitrogen fixing.

The introduction of nitrogen fixing species can benefit overall yield on nitrogen deficient sites. Increases in soil nitrogen have been noted in Hawaii (DeBell et al. 1985), India (Samraj et al 1977), rut whether nitrogen fixers grCMIl in sani-shade as an understorey species actually fix much nitrogen is uncertain.

Ccmcins;cms on soils .

1 . Many of the soils available for forestry plantations in the tropics and sub-tropiCS are inherently infertile and are easily degraded .

2. sane of the methods used for clearing sites for planting are excessively destructive of the soils. These include the use of heavy rrachinery and indiscriminate use of fire which result in the rE!lOval and exposure of the top soil. Soils under rainforests will be darraged if these techniques are used. It should be noted, InoIever, that rrany of the forest plantations in the rainforest zone are being established on sites that have already been degraded, and in fact afforestation in the tropics is rrore usual in grasSland, scrub, savanna ~and or disturbed vegetation than in dense polyspecific forests (Wood & Dawkins 1971).

3 . The rraintenance of the topsoil organic content and the rapid recycling of nutrients by the deCCllpOSition of the litter layer on the forest floor are important contriWtors to the rraintenance of soil fertility.

4. Losses of nutrients fran exploited plantations are inevitable (through rE!lOvalof biomass at harvesting), rut second rotation yield decline should only be expected on nutrient deficient sites and can be corrected. Second rotation decline is not an inevitable consequence of rronospecific plantations . Many of the fertility problems associated with IOCll1ospecific plantation forestry can be overccma, or at least greatly arreliorated, by good forestry practice; such as care in the use of clearing techniques, particularly in the use of heavy rrachinery and fire, the rraintenance of a balance between soil exposure and control of carpatition fran other species, the avoidance of over­stocking (so that small tree, shrub and herb strata can develop) and the addition of supplE!llS1tary fertilizers. These practices are equally appropriate whether the plantatiOns are mixed or pure.

5 . Mixed plantations can make a contriWtion to the managE!llS1t of soil fertility in scma circumstances:

19

to provide heterogeneity of leaf litter to help in promoting litterdecomposition and thereby to prevent the accumulation of litter on theforest floor and so to maintain the organic matter content of topsoils;

to provide ground cover in order to reduce the risk of erosion by windor rain and also prevent insolation of the topsoil and the consequentdamage to soil microfauna and microflora; this is of particularimportance in the establishment phase.

These two effects can often be achieved by encouraging and controllingthe growth of natural vegetation under pure plantations:

the admixture of nitrogen-fixing trees and shrubs, although these arelikely to be beneficial on sites on which only nitrogen is deficient,while other nutrients and moisture are not limiting and as previouslystated, these species may not be effective growing as understoreyspecies. The number of suitable sites is likely to be limited;

other potential advantages to soil management of mixing species, suchas the "nutrient pump effect", in which deep rooting species tapnutrients in the subsoil and deposit them at the surf ace in theirlitter, and beneficial interactions with mycorrhizae, are unproven inthe tropics.

3.2 CLIMATE AND POLLUTICK.

Climate change

The Changes in the climate that are predicted in the short- to medium-term may have beneficial or harmful effects on the growth of trees andforests. The increase in CO,levels and the rise in temperatures may increasegrowth rates, hit decreased insolation and drought may reduce them. Sameclimates may become more variable. The present ranges of species orprovenances that are not sufficiently buffered against environmental changes,such as climate change, will be reduced and some species or provenances maybecome extinct. This section discusses the likely reaction of single ormulti-species plantations to climatic change.

It is known that the concentrations of certain gases, such as carbondioxide (CO2), methane (CEO and nitrous oxide (NO2) have increased since thestart of the Industrial Revolution in the mid-18th century and it has beenpredicted that this will lead to global warming (the greenhouse effect). Oneestimate is that since 1765 levels of CO, have increased by 25%, of CH, by100% and of N20 by 10% (Jones 84 Wigley 1990.); another estimate is of 26%, 143%and 17% respectively since 1850 (Andrasko 1990). CO, concentrations havevaried throughout geological time, but present day levels are as high as theyhave everbeen in the last 160,000 years (Andrasko 1990). Estimates of annualincrements of CO, are imprecise; one source alone gives a range from .25% to.7% (Andrasko 1g90), implying that a doUbling of CO2 fram pre- IndustrialRevolution levels could occur as early-as the middle of the 21' century or aslate as the 23"1 century.

There is a general concensus that global temperatures have risen by0.5°C over the last century (Andrasko 1990, Jones and Wigley 1990). The

19

to provide heterogeneity of leaf litter to help in praroting litter dea:J:[ifXJSition and thereby to prevent the aCCllllUllation of litter on the forest floor and so to maintain the organic matter =tent of topsoils;

to provide ground cover in order to reduce the risk of erosion by wind or rain and also prevent insolation of the topsoil and the consequent damage to soil microfauna and microflora; this is of particular inportance in the establishllent phase.

These tvlo effects can often be achieved by encouraging and =trolling the grcMth of natural vegetation under pure plantations:

the admixture of nitrogen-fixing trees and shrul::s, although these are likely to be beneficial on sites on which only nitrogen is defiCient, while other nutrients and II'Oisture are not limiting and as previously stated, these species may not be effective growing as understorey species. The nl.mlber of suitable sites is likely to be limited;

other potential advantages to soil managetreIlt of mixing species, such as the "nutrient ptlllp effect", in which deep rooting species tap nutrients in the subsoil and deposit than at the surface in their litter, and beneficial interactions with rnycorrhizae, are unproven in the tropiCS.

3.2 CLDIM.'E AND FOLUJTI(B.

Climate change

The changes in the climate that are predicted in the short- to m=dium­teIIll may have beneficial or haIIIlful effects on the grcMth of trees and forests. The increase in O)~ levels and the rise in tatperatures may increase grcMth rates, rut decreasea insolation and drought may reduce than. Sate climates may becctte II'Ore variable. The present ranges of species or provenances that are not sufficiently b.lffered against environmental changes, such as climate change, will be reduced and sane species or provenances may becare extinct. This section discusses the likely reaction of single or multi-species plantations to climatic change.

It is kn= that the =centrations of certain gases, such as carbon dioxide (0)2)' methane (CH.) and nitrous oxide (NOi1~ have increased since the start of t.lie Industrial Revolution in the mid-18th century and it has been predicted that this will lead to global wanning (the greenhouse effect). One estimate is that since 1765 levels of 0) have increased by 25%, of CH by 100% and of Np by 10% (Jones & Wigley 1990); another estimate is of 26%, 143% and 17% respectively since 1850 (Andrasko 1990). 0)..2 concentrations have varied throughout geological time, rut present day leveLS are as high as they have ever been in the last 160,000 years (Andrasko 1990). Estimates of annual inCretrents of O)z are irrprecise; one source alone gives a range fran .25% to .7% (Andrasko 1~90), irrplying that a doubling of 0)2 fran pre-Industrial Revolution levels could occur as early as the middle of the 21st century or as late as the 23~ century.

There is a general =census that global tatperatures have risen by 0.5OC over the last century (Andrasko 1990, Jones and Wigley 1990). The

20

increase in temperature, however, cannot be directly related to the increasein CO. There are other factors which cause a rise in temperature such asvolcanic eruptions, solar flares and the movement of ocean currents, whichtend to occur eLLdtically. The effect of CO2 could account for a rise intemperature over the last century as high as 0.8°C or as little as 0.2°C(Jones and Wigley 1990).

If the concentration of atmospheric CO2 doUbles, then globaltemperatures may increase by 3°C to 5°C and regional averages could vary by-3°C to +10°C; global precipitation might increase by 7% to 15% and regionalaverages vary by -20% to +20%; regional soil moisture may vary by -30% to +30%(Andrasko 1990). Sane calculations have been made for South East Asia andWest Africa which predict that for a doUbling of atmospheric CO, there willbe a general increase in temperature of 3°C in South Fast Asia and of 4.5°C inWest Africa; rainfall changes include significantly increased seasonalvariation - more rain in the mcnsoons and less in the inter monsoon dryseasons - for South East Asia and a slight gain (0.1 mm/day) in West Africa.

The effect of temperature and rainfall Changes on vegetation is evenmore difficult to predict than the changes themselves. While temperate andsub-tropical forests may spread towards the poles, the sub-tropical moistforests may be replaced by tropical dry forests and grassland, savannawoodland and deserts may expand (Andrasko 1990, Calabri 1991). There may bean increase in the frequency and severity-of forest fires and pest outbreaksas a result of the accumulation of litter and deadwood arising from increasedvegetative growth due to CO2 enrichment.

It is possible that one of the effects of warning will be a generalextension of dry zones away from the equator. But the warming and dryingeffect will not be uniform over the whole world; in sane localitiestemperatures may drop or rainfall increase and in many areas rainfall willbecome more erratic. At the extremes of the Intertropical Convergence Zonein Africa rainfall is already erratic and it can be expected to become moreso.

The first effect on tree crops is likely to be that more frequentfailures of the rains at planting time will make regeneration more difficult.If such an effect occurs then more drought resistant species will need to beselected for planting. Those species considered to be at the limit of theirrange will have to be replaced by more drought hardy species or be proven tobe capable of maintaining their growth. Drought induced mortality of maturetrees may take longer to became apparent; but these trees will be understress and therefore the incidence of pests and diseases can be expected toincrease and the fire hazard can became worse. Climatic change can also beexpected to cause pests and diseases to change their range. The fungusGuignardiaaesculi on horse-chestnut (Aesculushippccastaneum) has, in recentyears, moved north of the Alps and is now to be found even in southernScandinavia; Ceratogystisfimbriata, a dise_ase of plane trees (Platanus spp),and its insect vector are moving north flum the Mediterranean. Although noconnection with warning of the climate has been proved, these examples givean indication of trends which may develop (Donnabauer 1991).

A policy of mixed planting will be justified on sites where presentrainfall is adequate but variable and it is hoped to establish a medium tolong rotation valuable species that is lacking in drought hardiness. In suchinstances a mixture of less valuable, but more drought hardy species will act

20

increase in tanperature, ~ver, cannot be directly related to the increase in CO

2• There are other factors which cause a rise in tanperature such as

volcanic eruptions, solar flares and the !lOvemant of ocean currents, which tend to = erratically. The effect of CO

2 =uld ac=unt for a rise in

tanperature over the last century as high as O. 8"C or as little as 0 . 2"C (Jones and Wigley 1990).

If the concentration of atllOspheric CO2

doubles, then global tanperatures may increase by 3"C to 5°C and regional averages =uld vary by -3"C to +10"C; global precipitation might increase by 7% to 15% and regional averages vary by -20% to +20%; regional soil!lOisture may vary by -30% to +30% (Andrasko 1990). Serna calculations have been made for South East Asia and West Africa which predict that for a doubling of atllOspheric COz there will be a general increase in tanperature of 3"C in South East Asia ana of 4. 5"C in West Africa; rainfall changes include significantly increased seasonal variation - !lOre rain in the IOCll1SOOllS and less in the inter m::msoon dry seasons - for South East Asia and a slight gain (0 .1 nmjday) in West Africa .

The effect of tanperature and rainfall changes on vegetation is even !lOre difficult to predict than the changes thanselves. While tanperate and sub-tropical forests may spread tcWcirds the poles, the sub-tropical !lOist forests may be replaced by tropical dry forests and grassland, savanna YKlOdland and deserts may expand (Andrasko 1990, calabri 1991) . There may be an increase in the frequency and severity of forest fires and pest outbreaks as a result of the aCCUllUllation of litter and dead wo::d arising fran increased vegetative grcMth due to CO

2 enrichment .

It is possible that one of the effects of warming will be a general extension of dry zones away fran the equator. But the warming and drying effect will not be uniform over the whole world; in sane localities tanperatures may drop or rainfall increase and in many areas rainfall will becane !lOre erratic. At the extremes of the Intertropical Convergence ZOne in Africa rainfall is already erratic and it can be expected to bea:m= !lOre so.

The first effect on tree =ps is likely to be that !lOre frequent failures of the rains at planting time will rrake regeneration !lOre difficult. If such an effect occurs then !lOre drought resistant species will need to be selected for planting. Those species =nsidered to be at the limit of their range will have to be replaced by !lOre drought hardy species or be proven to be capable of maintaining their growth. Drought induced !lOrtality of mature trees may take longer to bea:m= apparent; rut these trees will be under stress and therefore the incidence of pests and diseases can be expected to increase and the fire hazard can bea:m= worse. Climatic change can also be expected to cause pests· and diseases to change their range . The fungus Guignardia aesculi on horse-chestnut (AeSClllus hippocastaneum) has, in recent years, !lOved north of the Alps and is new to be found even in southern Scandinavia; Ceratcx::ystis fimbriata, a disease of plane trees (Platanus spp), and its insect vector are !lOving north fran the Mediterranean. Although no =nnection with warming of the climate has been proved, these exarrples give an indication of trends which may develop (Donnabauer 1991).

A policy of mixed planting will be justified on sites where present rainfall is adequate rut variable and it is hoped to establish a rredium to long rotation valuable species that is lacking in drought hardiness. In such instances a mixture of less valuable, rut !lOre drought hardy species will act

21

as an insurance against total biological failure. There is no evidence thatmixtures will enhance the survival of less hardy species.

Bruenig (1991) considers that climate change is happening and points outthat " ...this chanae will af fect the functions of forests and consequentlytheir role in the biosphere and their utility to humanity." He points to theneed for foresters to structure man-made forests to be more resilient toclimatic changes and extremes, to maintain high levels of biodiversity and tochoose species and design species mixtures that will adapt not only to futurechanges in climate bit also to changes in the economic and social environment .

Techniques are now available for selecting and breeding trees adaptedto specific sites and conditions. There is therefore potential to establishplantations relatively resilient to a Changed climate, bit for this to havea positive effect the changes should be predicted accurately. The lessvariation there is the greater the risk and the largest risk will be inmonoclonal plantations. Mixed plantations could be part of the strategy.However, provenances and clones that are highly specific to a site areacceptable in short rotation projects, providing there is a pool of geneticmaterial adapted to different climatic conditions which can be used to replaceunsuitable genetic materials at short notice. "Insurance" can be taken outin the form of more intensive research into genetic variation or in themixture of species in a plantation. This is discussed further in chapter 7.The Choice depends very much on the objectives of management and financialresources.

CO2 reservoirs

Growing trees remove CO2 from the atmosphere and store it in the formof cellulose. When the plantings are used (for instance for firewood) or whenthey reach maturity, however, the death of individuals and the naturalprocesses of decay return CO2 to the atmosphere at the same rate as it isremoved so that there is no net increase in storage. The use of plantationsto sequester CO2 will be most effective when they are used as a short-termsolution or when the final product is timber which is converted into durableproducts.This immobilizes CO2as cellulose for long periods after harvesting.Fuelwood plantations make a contribution while the trees are grawing and couldhelp reduce the rate of increase of atmospheric CO2, especially if thefuelwood is sUbsequently used efficiently. Fast growing, light demandingspecieswould give an early-effect, bit if an admixture of shade bearing tree,shrtb or herb species can improve the total yield of a site then a mixturewill be a more effective CO2 reservoir.

Microclimate.

Forests ameliorate the local climate, lowering temperatures andincrpsing humidity. Mixed plantations which produce multilayered forests aremore effective in achieving this. The contrast between the more uniform,microclimates to be found in the mixed (and all aged) mahogany/teak/jakplantations and the relativelymore extreme climatic fluctuations to be foundin the pure teak plantations at Sundapola, Sri Lanka is marked (Ng 1991).

A windbreak moderates the microclimate for up to twenty or more timesits height to leeward. A windbreak is most effective if, rather than actingas a wall which causes turbulence dcwnwind, it filters the wind and has aprofile that allows the wind to pass smoothly over the windbreak. Awindbreak

21

as an insurance against total biological failure. There is no evidence that mixtures will enhance the survival of less haJ:dy species .

Bruenig (1991) considers that climate change is happening and points out that " ... this change will affect the functions of forests and consequently their role in the biosphere and their utility to hl.mlaIlity." He points to the need for foresters to structure man-made forests to be IIDre resilient to climatic changes and extremas, to maintain high levels of biodiversity and to choose species and design species mixtures that will adapt not only to future changes in climate rut also to changes in the econanic and social envirorment.

Techniques are nON available for selecting and breeding trees adapted to specific sites and conditions. There is therefore potential to establish plantations relatively resilient to a changed climate, rut for this to have a positive effect the changes should be predicted accurately. The less variation there is the greater the risk and the largest risk will be in IIDnoclonal plantations . Mixed plantations could be part of the strategy. Hi::W:::!ver, provenances and clones that are highly specific to a site are acceptable in short rotation projects, providing there is a poel of genetic material adapted to different climatic conditions which can be used to replace unsuitable genetic materials at short notice. "Insurance" can be taken out in the form of IIDre intensive research into genetiC variation or in the mixture of species in a plantation . This is discussed further in chapter 7. The choice depends very much on the objectives of managarent and financial resources.

CO2 reservoirs

GrOiling trees rarove OJ2

fran the at:rrosphere and store it in the form of cellulose . When the plantings are used (for instance for firewood) or when they reach maturity, hOilever, the death of individuals and the natural processes of decay return OJ

2 to the at:rrosphere at the sane rate as it is

raroved so that there is no net increase in storage. The use of plantations to sequester OJ

2 will be IIDSt effective when they are used as a short-term

solution or when the final product is timber which is converted into durable products. This ilrm:Jbilizes OJ

2 as cellulose for long periods after harvesting.

Fuelwood plantations make a contriWtion while the trees are grONing and could help reduce the rate of increase of atIIDSpheric OJ

2, especially if the

fuelwood is subsequently used efficiently. Fast grONing, light demanding species would give an early effect, rut if an admixture of shade bearing tree, shrub or herb species can improve the total yield of a site then a mixture will be a IIDre effective OJ

2 reservoir.

Microclimate.

Forests ~liorate the local climate, 10Nering tarp=ratures and increasing humidity. Mixed plantations which produce multilayered forests are IIDre effective in achieving this . The contrast between the IIDre uniform, microclimates to be found in the mixed (and all aged) mahogany/teak/jak plantations and the relatively IIDre extrare climatic fluctuations to be found in the pure teak plantations at Sundapola, Sri Lanka is marked (Ng 1991).

A windbreak moderates the microclimate for up to twenty or IIDre tines its height to leewaId. A windbreak is IIDSt effective if, rather than acting as a wall which causes turrulence damwind, it filters the wind and has a profile that allCMS the wind to pass srroothly over the windbreak. A windbreak

22

havingtall trees at the centre and shorter ones at the outsidP will reproducethis profile. This can be achieved by using a mixture of tall and shortspecies.

Po_Uut 'ion

Forest damage caused by air pollution arising frananthropogenic sources(such as sulphur dioxide, acid rain or heavy metals) is primarily a problemin countries where there are heavy industries, electric power generatingplants and large numbers of motor vehicles, all burning fossil fuels. Whilethese prdblems are acute in developed countries, however, some tropicalcountries, such as India and Brazil, have heavy industries and there ispotential for damage, although no records of this have been noted. It islikely that in developing countries strong economic pressures coMbined withweak social and political pressures on industries will cause pollution tocontinue and even get worse. Same species are better adapted to withstandingpollution than others; for example in the Carpathian foothills of the USSR,an oak/silver fir mixture was found to be more resistant to kainite dust,hydrochloric acid and organic fats from a potash factory than either speciesalone or any other species. Ayoung oak/alder plantation withstood soot andcarbon monoxide from an activated carbon factory better than other species(Vbron 1979). In the hills around Mexico City, one of the most heavilypolluted cities in the world, natural forests of pure Aboies religiosa havebeen almost completely killed as a result of high levels of ozone pollution,while other species have survived (Ciesla and Macias 1987, Whitmore 1991)including Pinus hartwegii growing at higher elevations. In the SanBernardino Mountains of California Pinus jeffreyi and P. ponderosa have beenadversely affected by air pollution, while Calocedrus decurrens (incensecedar) and Abies cor2color(wbite fir) have been relatively unaffected (Millerand Elderman 1977). These references illustrate that individual species maybe tolerant of various forms of pollution but there is no evidence that theexamples of mixtures of species proving more resistant to pollution were infact more successful than the sama species grown in pure association.Presumably a mixture of species resistant to different types of pollutionwould be an "insurance" against complete failure in a situation where thelevel or the type of pollution were expected to change with time.

The use of municipal waste waters to irrigate plantations on sewagefarms is becoming more common in the tropics. In South Australia a mixtureof Casuarina glauca and Eucalyptus occidentalis has been found to be effectivein using saline effluent; in less saline conditions C.cunninghamiana can beused in the mixture. E.camaldulensis and E.occidentalis mixtures are alsolikelyto tolerate conditions of flooding and salinity. Atwo tier plantationdisposal system is being.developed in which a vigorous potentially high valuespecies is established and irrigation from municipal reclaimed water ismatchedto saturation deficiency; other species are grown on a site simulatinga winter-spring flood plain system during the rainy season. It is intendedto use mixtures of two or three species (Boardman 1990). These examplesoffer, however, no comparison with the performance of a single species notgrown in mixture.

22

having tall trees at the centre and shorter ones at the outside will reproduce this profile. This can be achieved by using a mixture of tall and short species.

Pollution

Forest damage caused by air pollution arising fran anthropogenic sources (such as sulphur dioxide, acid rain or heavy rretals) is primarily a problan in countries where there are heavy industries, electric power generating plants and large numbers of motor vehicles, all b..!rning fossil fuels. While these problans are acute in developed countries, ~ver , sane tropical countries, such as India and Brazil, have heavy industries and there is potential for damage, although no records of this have been noted. It is likely that in developing countries strong econanic pressures a::mbined with weak social and political pressures on industries will cause pollution to continue and even get worse. Sare species are better adapted to withstanding pollution than others; for example in the carpathian foothills of the USSR, an oak/silver fir mixture was found to be more resistant to kainite dust, hydrochloric acid and organic fats fran a potash factory than either species alone or any other species. A young oak/alder plantation withstood soot and carl:Jon monoxide fran an activated carbon factory better than other species (Voron 1979). In the hills around Mexico City, one of the most heavily polluted cities in the world, natural forests of pure Abies religiosa have been almost cc:rrpletely killed as a result of high levels of ozone pollution, while other species have survived (Ciesla and Macias 1987, Whitmore 1991) including Pinus hartl.egii growing at higher elevations. In the San Bernardino M:Juntains of california Pinus jeffreyi and P. ponderosa have been adversely affected by air pollution, while Calocedrus decurrens (incense cedar) and Abies cmcolor (white fir) have been relatively unaffected (Miller and Elderman 1977). These references illustrate that individual species may be tolerant of various fonns of pollution rut there is no evidence that the examples of mixtures of species proving more resistant to pollution were in fact more successful than the same species grown. in . pure association. Presumably a mixture of species resistant to different types of pollution would be an "insurance" against cc:rrplete failure in a situation where the level or the type of pollution were expected to change with tiIne.

The use of rrrunicipal waste waters to i=igate plantations on sewage fanns is becaning more canron in the tropiCS. In South Australia a mixture of Casuarina glauca and Eucalyptus occidentalis has been found to be effective in using saline effluent; in less saline conditions C.cunninghamiana can be used in the mixture. E. camaldulensis and E. occidentalis mixtures are also likely to tolerate conditions of flcxxl.ing and salinity. A two tier plantation disposal systan is being developed in which a vigorous potentially high value species is established and i=igation fran rrrunicipal reclaiIred water is matched to saturation deficiency; other species are grown. on a site sirmllating a winter-spring flood plain systan during the rainy season. It is intended to use mixtures of two or three species (BoaIdman 1990). These examples offer, ~ver, no c:x:nparison with the performance of a single species not grown. in mixture.

3.3 FIRE

Global statistics on forest fire incidence and area burned are lacking,but, between 1980 and 1988, Europe (excluding the USSR) and North Amaricasuffered an average of about 20 000 forest fires yearly, most of which arosefluri human causes such as negligence and arson. The area burned each year wasabout 4 million ha, causing enormous but unquantified losses of timber,environmental benefits, amenity, cultural values and even property and humanlives (Calabri 1991). Howmany of those fires occurred in plantations is notrecorded but in Brazil over 200 000 ha of plantations were burned between 1983and 1988, out of a total plantation area of 6million ha. This may appear avery small proportion of the total area but the monetary cost to the nationWaS estimated to be $US 199.6 million (Soares 1991).

The reduction of fire hazard may be achieved through variousinterventions, for example, mechanical means sudh as firebreaks or roads(which are costly and may lead to loss of amenity), the use of herbicides(which is both costly and environmentally damaging) and biological means, suchas grazing within woodlands, which is difficult to control and to reconcilewith forest and soil conservation. Prescribed burning has been proposed butcarries the risk that the fire may spread and in Europe and North America itsuse may not be acceptable to the public in some places (Calabri 1991).

The incidence of fires in forests (including plantations), is growingrapidly around the world, but there are difficulties of caMbatting orpreventing forest fires in ways that are environmentally and sociallyacceptable. It is therefore surprising that the effect of mixed speciesplantations on severity of fire damage has not been more widely tested.Velez (1991) has drawn attention to the need for discontinuities inplantations and themodification of inflammability models (whichare relatedto the moisture content of the fuel and the structure of the vegetation) toslaw the spread of fire. The incorporation of other species, especiallyhardwoods, in intimate or discrete mixtures would net these aims.

3.4 CONSERVATION OF ANIMAL AND PLANT GENETIC RESOURCES

General considerati.ons

Plantations are specialised but generally simplified ecosystems, inwhich plant diversity has been reduced in order to allow the maximumproduction of a single valuable component. The most valuable component isusually the woody stem of the planted tree species. When indigenous plantcommunities (forest, woodland or grassland) are converted to monospecific orpolyspecific plantations of native or exotic species, with the main purposeof wood production, generally there will be a reduction in both habitat andspecies diversity at that site. This may affect wildlife requirements for focdor shelter, or both.

The biological diversity at a site is associated firstly with thediversity of habitats or cammunities at that site in terms of structuralvariation (forest, grassland habitats, etc.); and secondly the diversity ofspecies within each habitat or community. Habitat diversity varies at severallevels - from individual trees to block sizes of several hectares (e.g. Clout1985, Gepp 1985, discussing birddiversities in plantations in New Zealand and

2323

3.3 FIRE

Global statistics on forest fire incidence and area b.lmed are lacking, but, be~ 1980 and 1988, Europe (excluding the USSR) and North America suffered an average of about 20 000 forest fires yearly, IOOSt of which arose fran hlmIan causes such as negligence and arson. The area b.lmed each year was about 4 million ha, causing enontOUS but unquantified losses of timber, environmental benefits, amenity, cultural values and even property and human lives (calabri 1991) . Jb.I many of those fires occurred in plantations is not reco:rded but in Brazil over 200 000 ha of plantations YJere b.lmed be~ 1983 and 1988, out of a total plantation area of 6 million ha. This may appear a very small proportion of the total area but the monetary cost to the nation was estimated to be $US 199.6 million (soares 1991).

The reduction of fire hazard may be achieved through various interventions, for exarrple, rrechani.cal rreans such as firebreaks or roads (which are costly and may lead to loss of amenity), the use of herbicides (which is both costly and envirormwantally damaging) and biological rreans, such as grazing within wood,lands, which is difficult to control and to reconcile with forest and soil conservation. Prescribed b.lming has been proposed but carries the risk that the fire may spread and in Europe and North America its use may not be acceptable to the public in sare places (calabri 1991).

The incidence of fires in forests (including plantations), is grcMing rapidly around the VlOrld, but there are difficulties of canbatting or preventing .forest fires in ways that are envirormwantally and socially acceptable . It is therefore surprising that the effect of mixed species plantations on severity of fire damage has not been m::>re widely tested. Velez (1991) has drawn attention to the need for discontinuities in plantations and the m::>dification of inflarrmability m::>dels (which are related to the m::>isture content of the fuel and the structure of the vegetation) to slow the spread of fire . The incorporation of other species, especially haJ:dwoods, in intimate or discrete mixtures would meet these aims.

General mnsi deraticns

Plantations are speCialised but generally silrplified ecosystans, in which plant diversity has been reduced in order to allow the maximum production of a single valuable c:x:rrp:nent . The IOOSt valuable c:x:rrp:nent is usually the VJOOdy stan of the planted tree species. When indigenous plant ccmmmities (forest, VJOOdland or grassland) are converted to monospecific or polyspecific plantations of native or exotic species, with the main purpose of VJOOd production, generally there will be a reduction in both habitat and species diversity at that site. This may affect wildlife requirarents for food or shelter, or both.

The biological diversity at a site is associated firstly with the diversity of habitats or ccmmmities at that site in tenns of structural variation (forest, grassland habitats, etc.) i and secondly the diversity of species within each habitat or ccmmmity. Habitat diversity varies at several levels - fran individual trees to block sizes of several hectares (e.g. Clout 1985, Gepp 1985, discussing bird diversities in plantations in New Zealand and

24

Australia respectively). A growing literature in "conservation biology"addresses the issue of diversity (e.g. Wilson 1988, Soule 1986).

Diversity-in the plantation tree layer can thus arise in several ways:

from multi-species plantings;from mixed age plantings in mixtures or in adjacent small blocks;flout retaining same level of natural vegetation as patches or asindividual trees or shrubs within the plantation.

The maximization of cost effective tiMber yield per unit area is likelyto be incompatible with maintaining either high levels of "natural"biodiversity or high densities of favoured wildlife species. But this does notmean that plantation forestry is necessarily always detrimental to wildlifeinterests. Plantations have a major role to play in wildlife conservation andmanagement at both the national and local level. This role may be direct - inproviding a habitat for target species; or indirect - in relieving pressureon other wildlife habitats.

Arry form of forest management, including the planting of trees, is goingto dhange not only-the pattern of bindiversity, but also wildlife parameterssuch as biamass and species densities. Whilst the replacement of a degradedscrUbland by a productive multispecies plantation may greatly increasewildlife species richness and bianass, this maybe seen as a negative changeif the original scrUbland fauna and flora is globally at risk.

Rehmani (1989) describes the loss of the natural dry grasslandcommunities of central India with the endangerment of the associated fauna ofbustard, gazelle and wolf. Its replacement with eucalypt plantation which mayhave higher densities of Axis deer is not a conservation gain if the aim isto conserve the maximum number of wildlife species.

This Change in natural biodiversity has two implications in terms ofdesigning and managing plantations for the conservation and management ofnatural resources. These are:

the conservation of overall biodiversity - the total range of genetic,species and carmunity diversity of all plants and animals at that site;

the management of the plantation habitat to produce wildlife species ofpotential positive benefit (i. e. deer for hunting) or to reduce speciesof potential negative benefit (e.g. pest species which decrease woodproduction).

These two Objectives and ensuing management activities are so differentas to warrant separate discussion.

Conservation of biodiversity

Background

The necessity for slowing the rate of loss of total biologicaldiversity, especially that contained in tropical forest ecosystems, is welldescribedin recent literature and plantation forestryhas a significant roleto play in conservation planning and management (Poore & Sayer 1987 forexample). Three activities are of importance:

24

AUstralia respectively). A growing literature in "conservation biology" addresses the issue of diversity (e.g. Wilson 1988, SOule 1986).

Diversity in the plantation tree layer can thus arise in several ways:

fram multi-species plantings; fram mixed age plantings in mixtures or in adjacent small blocks; fram retaining sane level of natural vegetation as patches or as individual trees or shrubs within the plantation.

The max:imization of cost effective tllnber yield per unit area is likely to be inc:arpa.tible with maintaining either high levels of "natural" biodiversity or high densities of favoured wildlife species. But this does not nean that plantation forestry is necessarily always detrinaltal to wildlife interests. Plantations have a major role to play in wildlife conservation and managanent at both the national and local level. This role may be direct - in providing a habitat for target species; or indirect - in relieving pressure on other wildlife habitats.

Any fonn of forest managanent, including the planting of trees, is going to change not only the pattern of biodiversity, rut also wildlife paraIOOters such as bianass and species densities. Whilst the replacanent of a degraded scrubland by a productive multispecies plantation may greatly increase wildlife species richness andbianass, this maybe seen as a negative change if the original scrubland fauna and flora is globally at risk.

Rehmani (1989) describes the loss of the natural dry grassland camnmities of central India with the endangenrent of the associated fauna of J::ustarii, gazelle and ~lf. Its replacanent with eucalypt plantation which may have higher densities of Axis deer is not a conservation gain if the aim is to conserve the maximum number of wildlife species .

This change in natural biodiversity has ~ irrplications in tenus of designing and managing plantations for the conservation and managanent of natural resources. These are :

the conservation of overall biodiversity - the total range of genetiC, species and camnmity diversity of all plants and animals at that site;

the managanent of the plantation habitat to produce wildlife species of potential positive benefit (Le . deer for hunting) or to reduce species of potential negative benefit (e .g. pest species which decrease wood production) .

These ~ objectives and ensuing managanent activities are so different as to warrant separate discussion.

CLDservation of biodiversity

Background

The necessity for slowing the rate of loss of total biological diversity, especially that contained in tropical forest ecosystans, is well described in recent literature and plantation forestry has a significant role to play in conservation planning and managanent (Pocre & Sayer 1987 for example). Three activities are of irrportance :

25

Developing forest cover, through afforestation or reforestation, toincrease the effective size of the forest or protected area. This could be ingeneral, to raise populations of key wildlife species above minim= levels forviability by creating a larger area, or, more specifically, by providing coveralong dispersal routes or "corridors" used by these species.

Developing peripheral plantations to act as a buffer zone for resourceuse around forested areas that are threatened by intense exploitation pressurewithout due management .

Developing multiple-use resource plantations for rural communities soas to reduce their need to exploit nearby protected areas of conservationimportance. These plantations need not be adjacent to the protected area.

The first category of plantation and to a lesser extent the second wouldbetter fulfil their conservation function if their structure and compositionresembled the natural forest cannunity. Multi-species plantations which allowan understorey and have a structural diversity through multi-age blockplanting and the maintenance of gaps, etc are thus of greater importance thanstn.icturally homogenous monospecific blocks. There is an extensive literatureon the design of man-made (and managed) forests for joint conservation/production objectives frcrt the United States (e.g. Thomas 1979, Harris 1984,Hoover& Wills 1987, McTaggart-Cowan 1985, Salwasser 1985, 1990) and elsewhere(Ratcliffe & Petty 1988; Hobbs, Saunders & Hussey 1990; and generally, Poore& Sayer 1987; Kemp, 1992).

For conservation purposes, species mixtures have to provide realecological differences; two dif ferent conifers would not necessarily providebenefit over a single species. Mixtures of a deciduous and eveigreen speciesor the addition of edible fruit or fodder species to a principal timberspecies can provide real differences in niche availability and hence habitatdiversity. In Indian pdantation forestry practice species mixtures are nibeing considered, where same 10 - 20% of trees are included beca.use of theirvalue to local people or wildlife (Wildlife Institute of India - forestmanagement guidelines). Note that modern conservation sees a strong linkaaebetween satisfying resource requirements of people and ensuring sustainableconservation.

Species mixtures can include mixing the main plantation species withspecies already in situ. This can be in blocks or strips of natural growthorby the retention of individual tree species e.g. figs or overemature "snag"trees which provide nesting sites or insects as food (Rodgers 1992). Naturalopenings such as roCky areas, marshy areas should be retained.

Plantation management as well as the initial design is of importance.Plantation thinning and felling practice can be designed to benefit diversityof plant and animal species. Sane old growth can be retained and some fallenlogs left in situ for example. Specific management practices will follow framthe Objectives of the plantation as a whole and the objectives of eachparticular zone in the plantation. MUlti-purpose plantations are bestconsidered through internal zonation, where different priorities can be givento different objectives within each zone.

Where plantations are to be developed adjacent to natural forest ofbiological importance, it is essential to ensure that plantation mixtures donot include invasive species. The development of commercial hardwood

25

Developing forest cover, through afforestation or reforestation, to increase the effective size of the forest or protected area. This could be in general, to raise populations of key wildlife species above minimum levels for viability by creating a larger area, or, IlOre specifically, by providing cover along dispersal routes or "corridors" used by these species.

Developing peripheral plantations to act as a J::uffer zone for resource use around forested areas that are threatened by intense exploitation pressure without due management.

Developing multiple-use resource plantations for rural CCIlI!D.lIlities so as to reduce their need to exploit nearby protected areas of conservation importance . These plantations need not be adjacent to the protected area .

The first category of plantation and to a lesser extent the second would better fulfil their conservation function if their structure and CCIIpJSition resanbled the natural forest CCIlI!D.lIlity. Multi-species plantations which allow an understorey and have a structural diversity through multi-age block planting and the maintenance of gaps, etc are thus of greater importance than structurally haoogenous IIalospecific blocks. There is an extensive literature on the design of man-made (and managed) forests for joint conservation/ production objectives fran the United states (e.g. Thanas 1979, Harris 1984, Hoover & Wills 1987, McTaggart-Cowan 1985, Salwasser 1985, 1990) and elsewhere (Ratcliffe & Petty 1988; Hobbs , Saunders & Hussey 1990; and generally, Poore & Sayer 1987 ; Karp, 1992) .

Fbr conservation purposes, species mixtures have to provide real ecological differences; two different conifers would not necessarily provide benefit over a single species. Mixtures of a deciduous and evergreen species or the addition of edible fruit or fodder species to a principal timber species can provide real differences in niche availability and hence habitat diversity. In Indian plantation forestry practice species mixtures are now being considered, where scm= 10 - 20% of trees are included because of their value to local people or wildlife (Wildlife Institute of India - forest management guidelines) . Note that m::Jdem conservation sees a strong linkage between satisfying resource requirements of people and ensuring sustainable conservation .

Species mixtures can include mixing the main plantation species with species already in situ . This can be in blocks or strips of natural growth or by the retention of individual tree species e .g. figs or over-mature "snag" trees which provide nesting sites or insects as food (Rodgers 1992) . Natural openings such as rocky areas, marshy areas should be retained.

Plantation management as well as the initial design is of importance. Plantation thinning and felling practice can be designed to benefit diversity of plant and animal species. SCIre old growth can be retained and scm= fallen logs left in situ for ~le. Specific management practices will follow fran the objectives of the plantation as a whole and the objectives of each particular zone in the plantation. Multi-purpose plantations are best considered through internal zonation, where different priorities can be given to different objectives within each zone .

Where plantations are to be developed adjacent to natural forest of biological importance, it is essential to ensure that plantation mixtures do not include invasive species . The developnent of carmercial hardwood

26

plantations in the East Usambara Mountains of Tanzania used the locally exoticMaesopsis eminii as a nurse crop for the valuable endemic Cephalospha erausarnbarensis. The f ormer is naa considered a major pest species, aggressivelyinvading natural forest in competition with local species (Hamilton & Bensted-Smith 1990) .

Il asures to increase species diversity in plantations

It is possible to give same general guidelines for increasing totaldiversity in plantations, assuming that plantation objectives indicate theneed to consider the conservation of the fullest range possible of nativeplant and animal species. The guidelines are as follows:

maintenance of areas of natural habitat within or close to theplantation area; there is same doUbt whether these patches should belarge or whether groups of smaller areas are to be prefer_ ed (Clout1985); this will depend on the exact objectives, such as, for exampleconservation of intraspecific variation of plants, when patches wouldbe appropriate, or the conservation of large mammals, when large areasare required. In Queensland 500 ha of native forest types are usuallyretained for every 4000 ha of plantations established; at least 200 haof the reserved forest is in a single block. These arPas are additionalto those excluded as not suitable for planting, because of steepness,rockiness, salinity, etc. (Francis and Shea 1987);

retention of indigenous forest strips, especially along water courses,linking larger natural reserves for which they form corridors formovement of wildlife;

a planting plan that, as far as possible, juxtaposes compartments ofdifferent species and of different ages;

the retention of indigenous trees or shrubs within the plantations,which may be justifiable for the encouragement of specific wildlifespecies e.g. the retention of flowering trees to attract nectar feedingor insectivorous birds, fruit trees for bats or leaf fodder forprimates, etc.;

care in planning the felling operations to allow escapereduce the period of disturbance to a minimum.

Wildlife monagenent

Wildlife for utilisation

cover and

For many plantation areas there will not be an overriding requirementto maintain or support the natural level of total diversity of plants andanimals. Plantation design could then maximize e.g. timber production.However other plantation products could be of subsidiary importance, forexample species of secondary commercial value suCh as bamboo or rattan, or ofsubsistence values such as fruit or leaf fodder. Wild animal products fitwithin both categories. For example at a commercial level, sport hunting oftigers and other species, and the cropping of populations such as muskdeer,butterflies etc. At subsistence level, the managed hunting of meat animals andother food species can be of great value to rural people and often createsupport for plantation inputs at local level.

26

plantations in the East Usambara M:>untains of Tanzania used the locally exotic Maescpsis eninii as a nurse =p for the valuable endemic Cephalosphaera usambarensis. The fonrer is nCM considered a major pest species, aggressively invading natural forest in carq:>etition with local species (Hamilton & Bensted­Smith 1990).

M:asures to increase species diversity in plantations

It is possible to give same general guidelines for increasing total diversity in plantations, assuming that plantation objectives indicate the need to consider the conservation of the fullest range possible of native plant and animal species . The guidelines are as follCMS :

maintenance of areas of natural habitat within or close to the plantation area; there is Sate doubt whether these patches should be large or whether groups of smaller areas are to be preferred (Clout 1985); this will depend on the exact objectives, such as, for exanple conservation of intraspecific variation of plants, when patches would be appropriate, or the conservation of large rnarn:nals, when large areas are required. In QJeensland 500 ha of native forest types are usually retained for every 4000 ha of plantations established; at least 200 ha of the reserved forest is in a single block. These areas are additional to those excluded as not suitable for planting, because of steepness, rockiness, salinity, etc. (Francis and shea 1987);

retention of indigenous forest strips, especially along water courses, linking larger natural reserves for which they fonn corridors for movement of wildlife;

a planting plan that, as far as possible, juxtaposes ~ts of different species and of different ages;

the retention of indigenous trees or shrubs within the plantations, which may be justifiable for the encouragement of specific wildlife species e.g. the retention of flCMering trees to attract nectar feeding or insectivorous birds, fruit trees for bats or leaf fodder for primates, etc.;

care in planning the felling operations to allCM escape cover and reduce the period of disturbance to a minimum.

Wildlife ~~'eit J

Wildlife for utilisation

For many plantation areas there will not be an overriding requiratent to maintain or support the natural level of total diversity of plants and animals. Plantation design could then maximize e. g . timber production. f!cJNever other plantation products could be of sul:Eidiary :ilrp:lrtance, for exanple species of secondary ccmrercial value such as bamboo or rattan, or of subsistence values such as fruit or leaf fodder. Wild animal products fit within both categories. For exanple at a ccmrercial level, sport hunting of tigers and other species, and the cropping of p:>pUlations such as llIllSkdeer, rutterflies etc. At subsistence level, the managed trunting of neat animals and other food species can be of great value to rural people and often create support for plantation inputs at local level.

27

This section describes factors affecting the design and management ofa plantation for increasing such wildlife products. The planning stage is ofgreat importance and should involve identification of products seen asimportant by local caTmunities Large plantation blocks would probably involveseveral zones giving different levels of priority to different objectives andproducts.

Plantations as wildlife habitat

Plantationsmayprovide ideal habitat conditions for certain generalistspecies at sane particular stage of the plantation cycle. This could be at themore gTassy post-clearing and seedling stages for grazers, or at the oldermore mature crop stage, especially if there is an understorey vegetation layerfor forest dwelling browsers. This means that the pattern of wildlife useresulting fram the establishment of plantations is not simply to cause anexodus of wildlife fran the anea, as some generalist species will remain, andpla.ntations may attract or support different species fron those that existedin the previous state. The pattern of species use will change through the lifeof the plantation. Introduction of desired species may be necessary orbeneficial at different stages.

Large blocks of pole stage exotic pine plantations were found to beparticularlypoor in wildlife in NOW Zealand - for example bird species (Clout1985)- but taking all plantation age classes into consideration, it was foundthat the number of species in the plantation was almost the same as in thenative vegetation in South Australia (Gepp 1976). Higher densities ofinsectivores, macrppods and sane seed-eaters may occur in plantations than innatural cammunities (Gepp, 1985). In Knysna, South Africa, although the totalrequirements of bushbuck (ndgelaphus scriptus) were best met by theindigenous broadleaved everyleen forest, the clearfelled areas were used atnight, and dense Pinusradiata and P. elliottii plantations by day (Odendaaland Bigalke 1979). P. radiata plantations on the KikuyuEscarpment in Kenyawere less favourable to bird species with specialised habitat requirements,but several generalist species with broader habitat requirements adaptedwellto them, and palaearctic rnigrants made greater use of plantations than naturalforest (Carlson 1986).

The creation of a mixed stand may even be deleterious for some wildlifespecies. In Britain the admixture of oak into a pine cannunity is knuoln to befatal for red squirrels, because grey-squirrels are far more successful in theconifer/broadleaved mixture and the indigenous red cannot coexist with theexotic grey squirrel (Kenward 1990).

The boundary between two habitats, whether between forest andagricultural areas or between two structural forest or plantation types, oftenhas a higher number of species and biomass than any one of the communities(Moss 1979; Friend 1980). This is the well known "edge effect" of wildlifebiology. Greater levels of "edge" can increase numbers of several generalistherbivores, deer being the prime example. Edges are not beneficial, however,when the conservation goal is to foster a habitat specialist which isdependent on large areas of forest. There is increasing debate on the valuesof edges in conservation biology (Reese and Ratti 1988).

Large mammal use of plantations is much greater when there is anunderstorey of native plants which provides shelter and food (Gepp 1985). Ifsuch wildlife production is a required output, then the plantation canopy

27

This section describes factors affecting the design and managarent of a plantation for increasing such wildlife prcxiucts. The plarming stage is of great importance and should involve identification of products seen as important by local camrunities . Iarge plantation blocks VlOUld probably involve several zones giving different levels of priority to different objectives and products .

Plantations as wildlife habitat

Plantations may provide ideal habitat conditions for certain generalist species at SCIre particular stage of the plantation cycle . This could be at the IlOre grassy post-clearing and seedling stages for grazers , or at the older IlOremature crop stage, especially if there is an understorey vegetation layer for forest dwelling broYSers. This rreans that the pattern of wildlife use resulting fran the establishment of plantations is not simply to cause an exodus of wildlife fran the area , as sare generalist species will ranain, and plantations may attract or support different species fran those that existed in the previous state . The pattern of species use will change through the life of the plantati on . Intrcxiuction of desired species may be necessary or beneficial at different" stages .

Iarge blocks of pole stage exotic pine plantations were found to be particularlypoor in wildlife in New Zealand - for exarrple bi rd species (Clout 1985) - rut taking all plantation age classes into consideration, it was found that the number of species in the plantation was alI!Ost the same as in the native vegetation in South Australia (Gepp 1976). Higher densities of insectivores , macropods and SCIre seed-eaters may occur in plantations than in natural camrunities (Gepp , 1985) . In Knysna , South Africa, although the total requirarents of J::ushl::uck (Tragelaphus s=iptus) were best net by the indigenous broadleaved evergreen forest, the clearfelled areas were used at night, and dense Pinus radiata and P. elliottii plantations by day (Odendaal and Bigalke 1979) . P . radiata plantations on the Kikuyu Esca.Ipllent in Kenya were less favourable to bird species with specialised habitat requirarents, rut several generalist species with broader habitat requirarents adapted well to than, and palaearctic migrants made greater use of plantations than natural forest (carlson 1986) .

The creation of a mixed stand may even be deleterious for SCIre wildlife species . In Britain the admixture of oak into a pine camrunity is knoon to be fatal for red squirrels , because grey squirrels are far IlOre successful in the conifer/broadleaved mixture and the indigenous red cannot coexist with the exotic grey squirrel (Kenward 1990).

The boundary between two habitats, whether between forest and agricultural areas or between two structural forest or plantation types, often has a higher number of species and bianass than anyone of the camrunities (M:lss 1979 ; Friend 1980). This is the well knoon "edge effect" of wildlife biology . Greater levels of "edge" can increase numbers of several generalist herbivores, deer being the prine exarrple . Edges are not beneficial, tJa.Jever, when the conservation goal is to foster a habitat specialist which is dependent on large areas of forest . There is increasing debate on the values of edges in conservation biology (Reese and Ratti 1988) .

Iarge marnral use of plantations is IlDlch greater when there is an understoreyof native plants which provides shelter and food (Gepp 1985) . If such wildlife prcxiuction is a required output, then the plantation canopy

28

should not be allowed to became too dense. In South India in a teak plantationwithin a wildlife area the thinning operations were carnbined with tending andweeding activities which resulted in a hamogenous grass layer. This attractedthe generalist Axis deer. But densities of elephant, saMbar deer (Cervusunicolor) and slothbear declined as they are all dependent on a denser forestand shrUb cover. Management was advised to consider leaving two out of everyten rows untended (Rodgers 1992).

In Swaziland the establishment of well protected exotic pine plantationson highveld grassland which had been used for sheep farming and had beenregularly hunted, has resulted in an increase in some wildlife species.Bushbudk and leopard and many other species of mammals are now common (Evans1988). In this example the increase in wildlife has in part been due to theprotection that could be afforded in the plantations, but which wasimpractical on the open grassland, but it also reflects an increase in speciesresulting from the creation of ni habitats and to the favourable conditionscreated at the boundaries of plantations and grasslands or rides. Generalistwildlife species are at far higher densities in the plantation areas of BoriReserved Forest in central India than in the adjacent neighbouring naturalmoist deciduous teak community. The plantation area is a mixture of pure teak,failed teak turned into bamboo plantation, grassy clearings and patches ofnatural forest. This is naa the preferred tourist area with high probabilitiesof sighting tigers and several large herbivores (Rodgers 1992). Thirty yearoldinixed plantations of indigenous Dalbergia sissoo, acacias, and Bombax sp.on the grassland are of Dudhwa National Park in North India are a major foodand shelter resource for large mammals and contribute to overall wildlifevalue. This contrasts with nearby stands of non-palatable teak and eucalyptwhidh are little used by wildlife species (Rodgers 1992).

This pattern of increased wildlife abundance may have its disadvantagessince same forms of life, whether insects or mammals such as elephant, deer,pig or mcnkey, can cause considerable damage in plantations. Such damage cansametims be reduced by planting unpalatable species at the boundaries betweenplantations and indigenous forests. In Sabah it was noted that deer damage toGMelina arborea plantations declined to negligible proportions 1 km fram theindigenous forest (Duff et al. 1984). It is possible that a "barrier" ofunpalatable species, such as Acacia mangium, established next to the boundarywith the natural forest will reduce damage by browsing mammals.Mbrphologically different species, such as are contained in the understoreyof a forest plantation, can also be a natural barrier. On the other hand someinsectivorous birds are beneficial in helping to control insect attacks inplantations and can be encouraged by retaining strips and mosaics of naturalforest (Aracruz 1988). Natural forest strips will also harbour greaterarthropod diversities which will be advantageous in dealing with pests(through parasitic and predatory Hymenoptera for example). Action that can betaken before plantation establishment and during plantation management toincrease the biamass of desired species of wildlife includes:

the retention of strips of natural cover especially along streams anddrainage lines;

a planting plan that, as far as possible, juxtaposes compartments ofdifferent species and of different ages, and of grassy clearings andother natural vegetation;

28

should not be all~ to l::lecarE too dense. In SOuth India in a teak plantation within a wildlife area the thinning operations were canbined with tending and ',oIeeding activities which resulted in a harogenous grass layer. This attracted the generalist Axis deer. But densities of elephant, sambar deer (Cervus unicolor) and sloth bear declined as they are all dependent on a denser forest and shrub cover. ManagE!leIlt was advised to consider leaving tvlo out of every ten rows untended (Rodgers 1992).

In swaziland the establishrrent of well protected exotic pine plantations on highveld grassland which had been used for sheep fanning and had been regularly hunted, has resulted in an increase in sare wildlife species . Bushl::uck and leopard and many other species of rnarrrnals are now c::arm::m (Evans 1988). In this example the increase in wildlife has in part been due to the protection that could be afforded in the plantations, rut which was inpracticalon the open grassland, rut it also reflects an increase in species resulting fran the creation of new habitats and to the favourable conditions created at the boundaries of plantations and grasslands or rides. Generalist wildlife species are at far higher densities in the plantation areas of Bori Reserved Fbrest in central India than in the adjacent neighbouring natural llOist deciduous teak ccmnunity. The plantation area is a mixture of pure teak, failed teak turned into bamboo plantation, grassy clearings and patches of natural forest. This is now the preferred tourist area with high probabilities of sighting tigers and several large herbivores (Rodgers 1992). Thirty year old mixed plantations of indigenous Dalbergia sissoo, acaCias, and Banbax sp. on the grassland areas of Dudhwa National Park in North India are a Irajor food and shelter resource for large rnarrrnals and contriWte to overall wildlife value. This contrasts with nearby stands of non-palatable teak and eucalypt which are little used by wildlife species (Rodgers 1992).

This pattern of increased wildlife ahmdance Iray have its disadvantages since sare foDllS of life, whether insects or rnarrrnals such as elephant, deer, pig or rronkey, can cause considerable daIrage in plantations . Such daIrage can saretimes be reduced by planting unpalatable species at the boundaries between plantations and indigenous forests. In Sabah it was noted that deer daIrage to GneliIJa ar.borea plantations declined to negligible proportions 1 kIn fran the indigenous forest (Duff et al. 1984). It is possible that a "barrier" of unpalatable speCies, such as Acacia rnangium, established next to the boundary with the natural forest will reduce daIrage by browsing rnarrrnals. M:lrphologically different species, such as are contained in the understorey of a forest plantation, can also be a natural barrier. On the other hand sane insectivorous birds are beneficial in helping to control insect attacks in plantations and can be encouraged by retaining strips and rrosaics of natural forest (Aracruz 1988). Natural forest strips will also harbour greater arthropod diversities which will be advantageous in dealing with pests (through parasitic and predatory Hymencpteza for example). Action that can be taken before plantation establishrrent and during plantation IranagE!leIlt to increase the bianass of desired species of wildlife includes:

the retention of strips of natural cover especially along streams and drainage lines;

a planting plan that, as far as possible, juxtaposes a::npart:ments of different species and of different ages, and of grassy clearings and other natural vegetation;

29

extreme care in the use of fire which can have positive and negativeimpacts. Many grazers benefit from an occasional burn. Forestspecialists will not;

a policy of heavy thinning in the middle and late stages of plantationdevelopment,which will encourage the indigenous understorey and groundcover in the plantations;

the retention of indigenous trees and shrubs within the plantations,which may be justifiable for the encouragement of specific wildlifespecies e.g. the retention of flowering trees to attract nectar feedingor insectivorous birds, fruit trees for bats or leaves for orang-utans.

Conclusions on the conservation of animal and plant genetic resources

Any natural change or man-induced intervention in an ecosystem willaffect the wildlife population; the simplification and specialisation of thetree layer in the ecosystem will result in a reduction in wildlife diversityin comparison to a natural community, but the impoverishment will not beuniform. To stigmatise moncspecific plantations as "biological deserts"(quotationnoted in Friend 1980) is more an expression of emotional commitmentthan a rational analysis of the problem. Plantation management can go a longway to improving both natural diversity levels and to increasing wildlifeamenity values.

Good planning, starting with a statement of what priority and specificaims the conservation of biodiversity or the production of wildlife shouldhave, is essential. Various strategies are available, including the broadsense mixing of species in neighbouring compartments, which will encouragewildlife in industrial plantations without the creation of mixtures in thenarrow sense of polyspecific compartments. Where mixed plantations areappropriate, whether for specific products or for rehabilitation, diversityof structure and age is as important as diversity of species to encouragewildlife.

3.5 INSECTS AND DISEASES

There are few references in the forestry literature which compare theeffects of mixtures in artificial stands on the incidence of insects anddiseases or of the effects of insects or diseases on mixed stands. This makesa canparison of pure andmixed stands difficult. Extrapolation of informationfram agrosystems is not always sound because of the longer time scalesinvolved in forestry, although the tendencytaaards short rotation tree crops,for example Adbizia falcataria with a rotation of five to eight years inMalaysia or Eucalyptus species with a rotation as short as five years inBrazil, makes the comparison more valid. The tendency has been to comparepure artificial stands with mixed natural stands and in consequence other siteand environmental factors have confounded the comparisons.

29

extrema care in the use of fire which can have positive and negative inpacts. Many grazers benefit frcrn an occasional rum. Forest specialists will not;

a policy of heavy thinning in the middle and late stages of plantation developrent, which will encourage the indigenous understorey and ground cover in the plantations;

the retention of indigenous trees and shrubs within the plantations, which may be justifiable for the encouragE!lalt of specific wildlife species e . g. the retention of flowering trees to attract nectar feeding or insectivorous birds, fruit trees for bats or leaves for orang-utans.

Conclusions an the omservatian of animal and plant genetic resoorces

Any natural change or man-induced intervention in an ecosystem will affect the wildlife population; the sillq:Jlification and specialisation of the tree layer in the ecosystem will result in a reduction in wildlife diversity in a::rnparison to a natural CCIlIlDJIlity, rut the illq:Joverishm=nt will not be unifoDn . To stigIll3.tise lOClIlospecific plantatiOns as "biological deserts" (quotation noted in Friend 1980) is more an expression of emotional ccmnitment than a rational analysis of the problem. Plantation managE!lalt can go a long way to illq:Jroving both natural diversity levels and to increasing wildlife amenity values .

Good planning, starting with a statE!lalt of what priority and specific airos the conservation of biodiversity or the production of wildlife should have, is essential . Various strategies are available, including the broad sense mixing of species in neighbouring c::crrpartments, which will encourage wildlife in industrial plantations without the creation of mixtures in the narrcM sense of pol yspecific c::crrpartments. Where mixed plantatiOns are appropriate , whether for specific products or for rehabilitation , diversity of structure and age is as illq:Jortant as diversity of species to encourage wildlife.

3.5 DlSEC'l'S AND DISEASES

There are few references in the forestry literature which a::rnpare the effects of mixtures in artificial stands on the incidence of insects and diseases or of the effects of insects or diseases on mixed stands. This makes a a::rnparison of pure andmixed stands difficult. Extrapolation of infonnation frcrn agrosystems is not always sound because of the longer tine scales involved in forestry, although the tendencytCMards short rotation tree crops, for exarrple Albizia falcataria with a rotation of five to eight years in Malaysia or Eucalyptus species with a rotation as short as five years in Brazil, makes the a::rnparison more valid . The tendency has been to a::rnpare pure artificial stands with mixed natural stands and in consequence other site and enviromental factors have confounded the a::rnparisons.

Stability of forest ecosystems

One of the primary factors which regulate pest pppulations is theavailability of suitable host material. Natural forests which contain amixture of species achieve a state of complexity in which the vegetation isbroadly in balance with pests and disposes. These ecosystems include a widerange of insects, fungi and bacteria living- on the trees and herbaceousvegetation. An increase in the proportion of any host plant in an ecosystemtends to be followed by a corresponding increase in the pest or pathogenpopulation whose activities eventually reduce the host population baCk to alaw level. Insects and diseases help to control the size of individualspecies populations and thereby maintain the species diversity in thatecosystem; subsequently the populations of these organisms are themselvescontrolledby the reduction in available food andby the activities of naturalenemies. Way(1977) has describedthe sprucebudvaorm Choristoneura lumiteranain eastern North America as an example of this species-destabilizing, butcarrnunity-stabilizing activity. The tendency is, then, for the insects anddiseases to prevent any one plant component of the ecosystem dominating it.Therefore the simplification of an ecosystem to one tree species, as in amonospecific plantation, would appear to increase the risk of a serious attadkby an insect or disease unless other habitat requirements of the attadkingorganism can also be managed (Way 1977).

Diversity is greatest at the interface between two types of habitat.This can lead to problems with pest species which require elements of eachhabitat for their survival. The problems of raising sorghum in Sudan are anexample of this; many of the pests, such as elea finch, grasshoppers etc.live in the natural bush. In Bangladesh the invasion of GWelina artcreaplantations by the mistletoe Lcranthus perasitica, which invades framneighbouring natural forest, is another example on a smaller scale (Gibson andJones 1977). One solution to this problem is to continue the simplificationprocess ruthlessly-so that there is only one crop over a wide area (Way 1977).The agricultural practice of large scale monocropping, such as wheat farmingin the prairies, has the incidental effect of eliminating interface zones, bitthis is a solution that, even if it was appropriate, should not be applied inthe marginal and highly variable sites usually made available for large scaleforestry, where the first priority is to match species to site. There arenumerous examples in both agriculture and forestry where interfaces betweentwo ecosystems provide habitat requirements for natural enemies of pestspecies.

It might be thought that natural carmunities , especially where they arediverse, though capable of harbouring pest species, should be less susceptiblethan monospecif ic crops to catastrophic attacks . But diversity in itself doesnot prevent catastrophes especially in the rase of introduced pests . Sane ofthe catastrophic losses caused by introduced diseases in both Europe and NorthAmerica - Dutch Elm disease, Ophicstrana (=Ceratocystis) ulmi, ChestnutBlight , Endothia parasitica and White Pine Blister Rust , Cronartium ribicala -have occurred in natural polyspecif ic carrnunities . The balance achieved overmany years in natural forests is disrupted when new pests are introduced whichhave not co-evolved with their new host , are introduced into ecosystems whichlack natural enemies or when new tree species are established in an ecosystem.In the last case the relative advantage of an exotic crop is frequentlyattributable to a lad( of pests in its new surroundings . This adv-antage willdiminish as local pests and disposes adapt to the new host and will beeliminated if an exotic pest or disease is introduced (Gibson and Jones 1977) .

3030

stahl 1 j ty of forest ecosystems

One of the primary factors which regulate pest populations is the availability of Suitable host material. Natural forests which =tain a mixture of species achieve a state of a::nplexity in which the vegetation is broadly in balance with pests and diseases. These ecosystems include a wide range of insects , filllgi and bacteria living on the trees and herbaceous vegetation . An increase in the proportion of any host plant in an ecosystem tends to be foll~ by a corresponding increase in the pest or pathogen population whose activities eventually reduce the host population back to a low level . Insects and diseases help to =trol the size of individual species populations and thereby maintain the species diversity in that ecosystem; subs9:Illently the populations of these organisms are themselves =trolled by the reduction in available food and by the activities of natural enemies . Way (1977) has described the spruce bJdwonn CiJoristoneura lumiferana in eastern North AIrerica as an exanple of this species-destabilizing, but camumity-stabilizing activity. The tendency is, then, for the insects and diseases to prevent anyone plant a::nponent of the ecosystem daninating it . Therefore the siIrplification of an ecosystem to one tree species, as in a monospecific plantation , would a~ to increase the risk of a serious attack by an insect or di sease illlless other habitat ~irem=nts of the attacking organism can also be managed (Way 1977) .

Diversity is greatest at the interface between ~ types of habitat . This can lead to problems with pest species which ~ire elarents of each habitat for their survival. The problems of raising sorghum in Sudan are an exanple of this ; many of the pests, such as QJelea finch, grasshoppers etc . live in the natural bush . In Bangladesh the invasion of Gnelina arrorea plantations by the mistletoe Ioranthus parasitica, which invades fran neighbouring natural forest, is another exanple on a smaller scale (Gibson and Jones 1977) . One solution to this problem is to continue the siIrplification process ruthlessly so that there is only one crop over a wide area (Way 1977) . The agricultural practice of large scale monocropping, such as wheat fanning in the prairies, has the incidental effect of eliminating interface zones, but this is a solution that, even if it was appropriate, should not be applied in the marginal and highly variable sites usually made available for large scale forestry, where the first priority is to match species to site . There are numerous exanples in both agriculture and forestry where interfaces between ~ ecosystems provide habitat r9:Illirem=nts for natural enemies of pest species.

It might be thought that natural camrunities, especially where they are diverse, though capable of harbouring pest species, should be less susceptible than monospecific crops to catastrophic attacks. But diversity in itself does not prevent catastrophes especially in the case of introduoed pests . SCIre of the catastrophic losses caused by introduoed diseases in both Europe and North AIrerica - Dutch Elm disease, ct>hiostrana {=Ceratocystis} ulmi, Chestnut Blight, Endothia parasitica and White Pine Blister Rust , Cronartium ribicola -have occurred in natural polyspecific camrunities . The balance achieved over many years in natural forests is disrupted when new pests are introduoed which have not co-evolved with their new host, are introduoed into ecosystems which lack natural enemies or when new tree species are established in an ecosystem. In the last case the relative advantage of an exotic crop is f~ently attributable to a lack of pests in its new surroundings. This advantage will diminish as local pests and diseases adapt to the new host and will be eliminated if an exotic pest or disease is introduoed (Gibson and Jones 1977).

31

Large areas of pure plantations have been established and though there havebeen epidemics and failures, the majority of the plantations are reasonablysuccessful. An outstanding example is that of rUbber (hrevea brasiliensis)which has heen grown as an exotic in pure stands in Malaysia for over acentury with remarkably fi problems from pests and diseases (Ng 1991).Outbreaks of pests and diseases in plantations, whether pure or mixed, arefrequently a secandary problem due to failure to match species to site, poormanagement or other forms of stress.

The mechanisms and stratagems by which insects find a host tree andthemechanisms by which the enemies of those insects find their hosts are variedand camplex. Increased species diversity inplantations can be of assistancein preventing attacks on trees by providing camouflage for the crop at risk,hydreating barriers or by providing food and refuge for the natural enemiesof foraging insects. In Poland the use of the places cmplexes system hasbeen developed (Birot 1991), in which monospecific stands of Pinussylvestrisare broken up with small blocks of a few hectares of highly poly-specificplantation in order to diversify the wildlife habitat and to encourage thepresence of birds in particular, with the aim of controlling pest-insectpopulations (an exampleof the beneficial effects of interface zones discussedin the section on Conservation). The possibility that a mixture of speciesmay provide alternate hosts maybe harmful if the alternate host is essentialto the life cycle of the pest, or beneficial if the alternate host distractsthe pest from a more valuable species. On the other hand decreased diversitycan dislocate the pest's life cycle in several ways, such as by depriving itof alternate food sources if they are needed, by reducing the diversity ofcontiguous habitats in which many pests thrive, or by diluting the effect ofthe pest hythe volume of the material produced. Marqpest species have a highreproductive potential, however, and are able to expand their numbers inresponse to a high proportion of suitable host material. Decreased diversitycan also aid enemies of pests hydecreasing the occurrence of their enemies.Little, however, is known about the nature of spatial diversity that hamperspests (Way 1977).

Sane opposing vi.

There are sharply divided views on the desirability of pure plantationswith regard to the abundance of pests. Boyce (1954) expressed many of theviews of the proponents ofinixed forests. He advocated indigenous speciesratherthan exotic, natural regeneration rather than plantingand mixed ratherthan pure plantations. He claimed that a pure stand is ideal for a pathogento huid up to epidemic proportions and cited the failure of rubberplantations in South America as a result of severe infestation of SouthAmerican Leaf Blight (SALE). Rubber occurs naturally as a scattered tree inSouth American forests where the pathogen is also present. It does littleharm to the wild rUbber tree, but pure plantations were attadked and failedand so it has been argued that pure plantations, which provided a large volumeof host material, were a causal factor leading to the failure. It has beennoted, however, that the plantations in question were in fact establishedusing seedlings reintroduced from Malaysia. SALB does not occur yet inMalaysia and furthermore all rUbber trees there originate from an initialintroduction of 22 seedlings (Chou 1981). It is not surprising that plantingmaterial having such a narrow genetic base and which had been bred in theabsence of any selective pressure for resistance to SALE should fail.

31

Large areas of pure plantations have been established and though there have been epidanics and failures, the majority of the plantations are reasonably successful. An outstanding example is that of rubber (Hevea brasiliensis) which has been grown as an exotic in pure stands in Malaysia for over a century with remarkably few problems fran pests and diseases (Ng 1991). Outbreaks of pests and diseases in plantations, whether pure or mixed, are frequently a secondary problem due to failure to match species to site, poor managemant or other foDllS of stress .

The mechanisms and stratagems by which insects find a host tree and the rrechanisms by which the enemies of those insects find their hosts are varied and ccmplex. Increased species diversity in plantations can be of assistance in preventing attacks on trees by providing camouflage for the crop at risk, by creating barriers or by providing food and refuge for the natural enemies of foraging insects. In Poland the use of the places carplexes system has been developed (Birot 1991), in which m:xlospecific stands of Pinus sylvestris are broken up with small blocks of a few hectares of highly poly-specific plantation in order to diversify the wildlife habitat and to encourage the presence of birds in particular, with the aim of controlling pest-insect populations (an example of the beneficial effects of interface zones discussed in the section on Conservation). The possibility that a mixture of species may provide alternate hosts may be haDnful if the alternate host is essential to the life cycle of the pest, or beneficial if the alternate host distracts the pest fran a rrore valuable species. On the other hand decreased diversity can dislocate the pest's life cycle in several ways, such as by depriving it of alternate food sources if they are needed, by reducing the diversity of contiguous habitats in which many pests thrive, or by diluting the effect of the pest by the volume of the material produced. Many pest species have a high reproductive potential, hcMever, and are able to expand their nlnnbers in response to a high proportion of suitable host material. Decreased diversity can also aid enemies of pests by decreasing the occurrence of their enemies. Little, hcMever, is known about the nature of spatial diversity that harrpers pests (Way 1977).

Salle q:p>S; ng views.

There are sharply divided views on the desirability of pure plantations with regard to the ab..mdance of pests. Boyce ( 1954) expressed many of the views of the proponents of mixed forests. He advocated indigenous species rather than exotic, natural regeneration rather than planting and mixed rather than pure plantations. He clairred that a pure stand is ideal for a pathogen to ruild up to epidemic proportions and cited the failure of rubber plantations in South America as a result of severe infestation of South American Leaf Blight (SALE). Rubber occurs naturally as a scattered tree in South American forests where the pathogen is also present. It does little hann to the wild rubber tree, rut pure plantations were attacked and failed and so it has been argued that pure plantations, which provided a large volume of host material, were a causal factor leading to the failure. It has been noted, hcMever, that the plantations in question were in fact established using seedlings reintrcrluced fran Malaysia. SALE does not occur yet in Malaysia and furthennore all rubber trees there originate fran an initial introduction of 22 seedlings (Chou 1981). It is not surprising that planting material having such a ~ genetic base and which had been bred in the absence of any selective pressure for resistance to SALE should fail.

32

Perry and Maghembe (1989) in their appraisal of plantation forestry andecosystem concepts noted that diversity is an important defence mechanismagainst pests and diseases. The statement that "the Chances that a geneticmonoculture will be rObust against pests and diseases over the time periodrequired to reach maturity seems small.., the evolutionary capacity of short-lived pests and pathogens is enormous" , correctly draws attention to the risksof epidemics in monoclonal plantations and to the fact that pests often passthrough several generations of breeding and natural selection in a year (ascanpared to several years or even decades inmost tree species), and that theytherefore relatively easily-can overcome various types of disease resistanceoriginally found in the host species. Risks can be minimized through shortrotations (taking calculated risks), rotationof clones in space and time, andalternative end use options in the case of disease, based on early harvestingand replacement of diseased clones Large-scale clonal plantations, such asthose in Congo (see e.g Delwaulle 1989) and Brazil (Burley and Ikemori 1988;Campinhcs and Ikemori 1986), have been established with these considerationsin mind and, although not without problems, generally have avoided large-scalepest attack. Thus, provided that a broad genetic base is maintained inseparate base populations, to be used as "badk-ups" for narrowly-basedplantations or plantations established using single clone blocks; andprovided adequate attention is given to the continuing development of newhigh-yielding clones for intensive tree farming activities, the use even ofmonoclonal plantations can be biologically-as well as economically feasible.

Perry and Maghembe (1988) also cite the failure of Rinus radiata inAfrica after the introduction of ropthistrama blight, attacks by the nativecerambycid borer Chemida gahani on CUpzessus lusitanica in East Africa and thefact that several pines in Southern Africa suffer severely fran Diplodia pineaas arguments against the planting of pure stands. But it is by no meanscertain that pure stands are the prime cause of these problems. IsolatedP.radiata are just as susceptible to Bothistrcma blight as pure plantations(Gibson and Jones 1977). Dothistroma blight is of little significance in thesouth of Australia. On the other hand it has been devastating in Africa whereP.zadiata has been planted off-site in summer rainfall zones. Cemida gahanigains entry through wounds such as pruning scars, but has been largelycontrolled by better forest hygiene to remove breeding sites in slash anddebris (Gibson and Jones 1977). ailcdcdia rdnea is as serious a disease onisolatedtrees as in plantations and is prevalmtwhere pines are planted off-site in Southern Africa (Barnes and MUllin 1976).

There are other examples of pest and diseases that cause severe damagein plantations, but the prime cause cannot be attribilted to the fact that theplantations are monospecific. The root decay fungus fieterobasidice (=Fbmes)annosus is a wood (iPstroying basidianycete that colonizes woody residues, suchas stumps left in the ground in a clearing operation or as a consequence ofthinning operations. It can occur in either pure or mixed plantations butsince it is transmitted by root grafts, pure plantations favour the spread ofthe disease. H. annosus is, however, also thought to be favoured by sitesfrom which other antagonistic fungi have been eliminated; this occurs whenplantations are established on abandoned farmland (Gibson and Jones 1977).For this reason the disease may be regarded as a consequence of failing tomatch species to site as well as a disease of monospecific crops.

Rhizina undulata infection of pines is associated with the use of fireand so is another example of a disease owing more to the prehistory of thesite than to the fact that the crop is monospecific. Because/R.undu/ata causes

32

Perry and Maghanbe (1989) in their appraisal of plantation forestry and ecosystem concepts noted that diversity is an iItp:lrtant defence mechanism against pests and diseases. The statenent that "the chances that a genetic m::moculture will J:e ral:ust against pests and diseases over the t:ime period required to reach maturity seems small. .. the evolutionary capacity of short­lived pests and pathogens is enonnous", correctly draws attention to the risks of epidemics in m::moclonal plantations and to the fact that pests often pass through several generations of breeding and natural selection in a year (as carpared to several years or even decades in IOOSt tree species), and that they therefore relatively easily can overcare various types of disease resistance originally found in the host species. Risks can J:e minimized through short rotations (taking calculated risks), rotation of clones in space and t:ime, and alternative end use options in the case of disease, based on early harvesting and replacement of diseased clones. Large-scale clonal plantations, such as t.ho!>e in Congo (see e.g Delwaulle 1989) and Brazil (Burley and Ikemori 1988; Canpinhos and Ikemori 1986), have J:een established with these considerations in mind and, although not without problems , generally have avoided large-scale pest attack. Thus, provided that a broad genetiC base is maintained in separate base populations, to J:e used as "back-ups" for na.rrowly-based plantations or plantations established using single clone blocks; and provided adequate attention is given to the continuing developrent of new high-yielding clones for intensive tree faIming activities, the use even of m::moclonal plantations can J:e biologically as \0911 as econcrnically feasible .

Perry and Maghanbe (1988) also cite the failure of Pinus radiata in Africa after the introduction of Dothistrcma blight, attacks by the native cerarnbycid borer canida gahani on Cupressus lusitanica in East Africa and the fact that several pines in Southern Africa suffer severely fran Diplodia pinea as arguments against the planting of pure stands. But it is by no means certain that pure stands are the pr:ime cause of these problems. Isolated P.radiata are just as susceptible to Dothistrcma blight as pure plantations (Gibson and Jones 1977). Dothistrcma blight is of little significance in the south of Australia. On the other hand it has J:een devastating in Africa where P.radiata has J:een planted off-site in sl.lllll'er rainfall zones. canida gahani gains entry through wounds such as pruning scars, bit has J:een largely controlled by J:etter forest hygiene to remove breeding sites in slash and debris (Gibson and Jones 1977). Diplodia pinea is as serious a disease on isolated trees as in plantations and is prevalent where pines are planted off­site in Southern Africa (Barnes and Mullin 1976).

There are other exanples of pest and diseases that cause severe damage in plantations, rut the pr:ime cause cannot J:e attrib.lted to the fact that the plantations are m::mospecific. The root decay fungus Heterobisidion (=Fares) annosus is a wood destroying basidianycete that colonizes woody residues, such as stumps left in the ground in a clearing operation or as a consequence of thinning operations. It can oc= in either pure or mixed plantations rut since it is transmitted by root grafts, pure plantations favour the spread of the disease. H. annosus is, ha-lever, also thought to J:e favoured by sites fran which other antagonistic fungi have J:een eliminated; this occurs when plantations are established on abandoned fannland (Gibson and Jones 1977). Fbr this reason the disease may J:e regarded as a consequence of failing to match species to site as \0911 as a disease of monospecific crops.

Rhizina undulata infection of pines is associated with the use of fire and so is another exanple of a disease owing IOC>re to the prehistory of the site than to the fact that the crop is rronospecific. Because R.undulata causes

33

so many problems, the practice of burning plantation residues after clearfelling has largely been abandoned for sites planted to pine in southernAfrica as well as in northern EUrope.

In Ghana the scolytid beetles Xyleborus mascarensis, X. sha.rpae and X.semiopacus caused extensive damage and death in line planted Khaya ivorensisand Aucomnea _klaineana. The problem was attributed to the creation of a largeamount of woody debris as a result of ref ining operations to open up theforest for line planting. This debris formed an ideal breeding ground for theinsects and when it became depleted they turned to the -transplants (Gibson andJones 1977) .

Plneus pini is an introduced aphid in Africa and is an example of aninsect that has found natural polyspecific stands andmonospecific plantationsequally attractive. P.pini has been observed attacking isolated P.patula asseverely as plantations (Gibson and Jones 1977).

The opposite view, that large scale establishment of even-aged standsdoes not increase the risk of pests and diseases, has been propounded by Chou(1981). Chou uas defending the planting of .P.radiata in New Zealand wheremonospecific planting has been highly successful on a limited range ofenvironmental conditions. Briefly the points that he has made are:

there is no such thing as a generalised or typical epidemic, thereforethere is no reason to believe that a generalised prescription reommendingmixed plantations will be effective in preventing epidemics;

in certain circumstances indiscriminate mixtures can increase risk, forexample if alternate hosts for pests or diseases are introduced or if a mildlysusceptible species is mixadwith a very susceptible species. This point isalso made by Perry and Maghembe (1989);

sane pathogens attack a wide range of hosts. Thytophthora cinnamorni isknown to affect 444 species in 131 genera and 48 families including bothangiosperms and gymnosperms. Annillaria spp.contain a large number of strainsthat are relatively host-specific but with a host list that includes 677species in 276 genera it is unlikely that mixtures 14111 be completelyeffective as a barrier to the spread of these pathogens unless there is gooddata available on the relative susceptibility of the species to be includedin the mixture;

diversification of species implies diversification of the effort tocontrol diseases and pests and a dilution of the effort applied to any onespecies and therefore an increase in the risk for that species. Where, as aresult of a diversification policy, planting material has to be imported, thatin itself represents a risk of introducing disease and pests;

pure even-aged stands facilitate human intervention for the control ofpests and diseases. On the other hand in mixed stands, particularly all-agedstands, where selective felling is a management tool, the lik.elihood of damageto standing trees and the subsequent risk of entry by pathogens may beincreased.

33

so many problE!llS, the practice of l:un1ing plantation residues after clear felling has largely been abandoned for sites planted to pine in southern Africa as well as in northern Europe.

In Ghana the scolytid beetles Xyleborus mascarensis, X. shaIpae and X. sffiliopacus caused extensive damage and death in line planted Khaya i vorensis and Aucoumea klaineana. The problem was attriJ::uted to the creation of a large aIOClunt of WXldy debris as a result of refining operations to open up the forest for line planting. This debris fornwed an ideal breeding ground for the insects and when it became depleted they turned to the transplants (Gibson and Jones 1977) .

Pineus pini is an introduced aphid in Africa and is an exarrple of an insect that has found natural polyspecific stands and llOIlospecific plantations equally attractive. P.pini has been observed attacking isolated P.patula as severely as plantations (Gibson and Jones 1977).

The opposite View, that large scale establishment of even-aged stands does not increase the risk of pests and diseases, has been propounded by Chou (1981) . Chou was defending the planting of P.radiata in New zealand where llOIlospecific planting has been highly successful on a limited range of enviroorrental conditions . Briefly the points that he has made are:

there is no such thing as a generalised or typical epidemic, therefore there is no reason to believe that a generalised prescription recommending mixed plantations will be effective in preventing epidemics;

in certain circumstances indiscriminate mixtures can increase risk, for exarrple if alternate hosts for pests or diseases are introduced or if a mildly susceptible species is mixed with a very susceptible species. This point is also made by Perry and Maghanbe (1989);

sare pathogens attack a wide range of hosts . Phytophthora cinnartr:mi is kna.m to affect 444 species in 131 genera and 48 families including both angiospenns and gymnospenns . AImillaria spp. contain a large number of strains that are relatively host-specific but with a host list that includes 677 species in 276 genera it is unlikely that mixtures will be carpletely effective as a barrier to the spread of these pathogens unless there is good data available on the relative susceptibility of the species to be included in the mixture;

diversification of species :irrq?lies diversification of the effort to control diseases and pests and a dilution of the effort applied to anyone species and therefore an increase in the risk for that species. Where, as a result of a diversification policy, planting material has to be :irrq?orted, that in itself represents a risk of introducing disease and pests;

pure even-aged stands facilitate human intervention for the control of pests and diseases . On the other hand in mixed stands, particularly all-aged stands, where selective felling is a managemant tool, the likelihood of damage to standing trees and the subsequent risk of entry by pathogens may be increased .

Rae ccf mixed planting.

Although diversity of species may contribute to stability in naturalstands, it cannot be assumed that species diversity must necessarily providestability in all artificial stands. A legitimate Objective of the managementof plantations, whether industrial or non-industrial, is the maximization ofgrowth, or the production of other specified outputs, onto the mcst valuablespecies for the Objectives specified. This, for a variety of economic andindustrial reasons, reduces the number of species considered for planting.What is generally agreed is that though a reduction in diversity can resultin an increased risk of pest and pathogen damage, not nearly enough is knownabout the mechanisms by which diversity does create stability (Boyce 1954;Chou 1981; Perry and Maghembe 1989). There is as a consequence a lack ofknowledge on what species mixtures are desirable for controlling attacks bypests and pathogens, particularly in exotic plantations.

It is worth noting some of the situations in which mixtures have provedbeneficial in controlling attacks by pests and diseases. The cerarnbycid borerPhryneta leprosa attacks Milicia (=Chlorophora) excelsa through blistersresulting fram sun scordh in even aged plantations. It has caused losses intrial plots in Tanzania and very severe and widespread losses in Zaire (Gibsonand Jones 1977). Shading will control sun scorch and an admixture of otherspecies will provide shade when the AL excelsa plantations are established.

Itytolyma lata causes leaf gall on AL excelsa and can be very damaging,but the insect has a limited range of dispersal. However, control of theinsect is only achieved when the host tree is dispersed in a matrix of otherspecies to such an extent that one is bound to consider the proposition statedin the 1939 Dehra Dun conference: if the nurse species has to form the majorportion of the crop and is of law value, then another crop should beconsidered; if the nurse species is of equal value to thernain species, thereis little point in planting the main species (Indian Forest Service 1939).

The stem borers Hyp,sipyla grandella (in the NewWorld) and H.robusta (inthe Old World) are notorious for the damage that they cause to the leadingshoots of young trees in the sub-family Swietenioideae of the 141iaceae, mostof which are valuable timber trees.

Table 2 Host Genera of the stem Borers lipsipyla spp.Africa Asia South AmericaLovca Tbona SWieteniaMaya Chukrasia CedrelaEntandrqphragma Scymdcla CarapaCarepe10eudocedrelaGUarea (attadk recorded though in IN.I lioideae, Styles 1991).

Ayloaarpus sppwhich are in the sub-family Swietenioideae have not beenreported as being attacked (Styles 1991) and in South America Glared isreputedly not attadked (Wnibmore 1976). To same extent the two Hypsipylaspecies are specific to the tree species of their own zones. For example,Tocna ciliata, which is heavily attacked by H.rabusta in Australia, is notattadked, or is only lightly-attacked, by H.grandella in Costa Rica, where thenative Cedrela cdorata, on the other hand, is heavily attackadby.H. grandella(GrijErna and Ramallo 1973). 11.robusta attacks Swieteniamacrophylla in India

3434

Role of mixed plant.ing.

Although diversity of species may contrib..!te to stability in natural stands, it cannot be assurood that species diversity Il\USt necessarily provide stability in all artificial stands. A legitimate objective of the managarent of plantations, whether industrial or non-industrial, is the maximization of gro.-Ith, or the production of other specified outputs, onto the IOClSt valuable species for the objectives specified. This, for a variety of econanic and industrial reasons, reduces the number of species considered for planting. What is generally agreed is that though a reduction in diversity can result in an increased risk of pest and pathogen damage, not nearly enough is known about the nechanisms by which diversity does create stability (Boyce 1954; Chou 1981; Perry and Maghanbe 1989) . There is as a consequence a lack of knCXolledge on what species mixtures are desirable for controlling attacks by pests and pathogens, particularly in exotic plantations.

It is worth noting sore of the situations in which mixtures have proved beneficial in controlling attacks by pests and diseases. The cerambycid borer PhIyneta leprosa attacks Milicia (=Chlorophora) excelsa through blisters resulting fran sun scorch in even aged plantations . It has caused losses in trial plots in Tanzania and very severe and widespread losses in Zaire (Gi.I::5on and Jones 1977). Shading will control sun scorch and an admixture of other species will provide shade when the M. excelsa plantations are established.

Phytolyma lata causes leaf gall on M. excelsa and can be very damaging, rut the insect has a limited range of dispersal. lbYever, control of the insect is only achieved when the host tree is dispersed in a matrix of other species to such an extent that one is bound to consider the proposition stated in the 1939 Dehra Dun conference: if the nurse species has to form the major portion of the crop and is of lCXol value, then another crop should be considered; if the nurse species is of equal value to the main species, there is little point in planting the main species (Indian Forest Service 1939).

The stem borers Hypsipyla grandElla (in the NewWorld) and H.rol:usta (in the Old World) are notorious for the damage that they cause to the leading shoots of young trees in the sub-family SWietenioideae of the M::!liaceae, IOClSt of which are valuable timber trees.

Table 2 Host Genera of the stem Borers HypsipYla ~ Africa Asia south America Lovre To::n3 SWietenia Khaya Chukrasia Cedrela Entandrophragma Soymida Cdrapa Cdrapa Pseudocedrela Guarea (attack recorded though in M::!lioideae, Styles 1991) .

Xylocarpus spp which are in the sub-family SWietenioideae have not been reported as being attacked (Styles 1991) and in SOUth America Guarea is reputedly not attacked (Whitrrore 1976) . To sare extent the two Hypsipyla species are specific to the tree species of their own zones . For example, To::n3 ciliata, which is heavily attacked by H.rol:usta in Australia, is not attacked, or is only lightly attacked, by H.grandella in Costa Rica, where the native Cedrela cdorata, on the other hand, is heavily attacked by H. grandella (Grijpna and Ramallo 1973). H.rol:usta attacks SWietenia macrophylla in India

35

and Sri Lanka and H.grandella attacks Rhaya senegalensis in Martinique(Grijpma 1973).

Shade is effective in reducing, but does not fully control, attack byHypsipyla (Whitmore 1976). Shade is normally provided by other specieseither planted concurrently with the Meliaceae or in the form of residualstands into which the Meliaceae are line planted. Suitable mixtures have beeninvestigated extensively in West Africa (Dupuy and Mille 1991); this isdiscussed more fully under Management in Chapter 5. But another species isnot always required to produce the shade; S. gacrpphylia is being regeneratedsuccessfully-at Sundapola in Sri Lanka under the shade of mature trees mostlyof the same species (Mattiah 1991).

The establishment of Meliaceae susceptible to h7rpsipyla under a nursecrop to provide shade is an obvious example of the use of mixtures inindustrial plantations, but it has to be noted that in francophone WestAfrica, where most recent work on the silvicultural management of Meliaceaehas been carried out, the decision has been taken not to plant Meliaceae(Cossalter 1991). On the other hand the Sundapola mahogany plantations wereestablished very successfully in mixture and in the Solomon Islands it isproposed to establish S. macrophylla in a matrix of Securinega flexuosa(Solomon Islands 1988 a and b).

In Kenya a canker on Cypress (CUpressus macrocarpa), is caused bySeridium unicornis (the imperfect state of Rhynchosphaeria cupressi). Thisfungus gains entry through wounds and pruning scars, but has a limited rangeof effective dispersal and it would therefore appear that the proximity oftrees in a pure plantation must contribute to the spread of the diseaseMixed planting of CUpressus macrocarpa and Gtevillea robusta has been triedin Kenya (Graham 1945 and 1949), but the management of such mixtures hasproved difficult resulting in poor form (butt sweep and lean) of trees of bothspecies. There was little evidence that the mixture controlled the diseaseEventually the decision was made to replace C. macrocarpa with C. lusitanica,a less vigorous species, but which is less susceptible to cypress canker andwhich has a better form.

. In India and Pakistan the insect Hoplocerambyx spinicorr2is has changedfrcm being an inhabitant of felled logs and moribund trees of Shorea robustain natural forests to attadking healthy mature trees when that species wasextensively established in pure plantations; the change in habits has beenattributed to the improved opportunities for reproduction provided inplantations (Gibson and Jones 1977) and may owe something to incre,9sed foodsupplies and even to stress arising from planting the species on an unsuitablesite. In Nigeria hecqphora testa tor, an insignificant pest of the naturalforest, caused widespread damage to pure plantations of Nauclea diderrichii(Gibson and Jones 1977). Mixtures of Nauclea diderichii with Lovoatrichilioides and EntandraThragma utile have, however, been successful (Lamb1991; Lowe 1991).

In Africa, at least, the most important and largest number of examplesof insect pests attributable to the establishment of monospecific plantationsare defoliators, and to a lesser extent borers (Gibson and Jones 1977).Nudaureliacytherea, Orgya mixta and Pachypasa capensis were noted as examplesof defoliators of Btachystegia woodland, which have over a period of yearsadapted to and cause extensive damage pine plantations; BUzura edWardsi isanother example. But there is no indication that mixed plantings will reduce

35

and Sri lanka and H. grandella attacks Khaya senegalensis in M3.rtinique (Grijpn3. 1973).

Shade is effective in reducing, rut does not fully control, attack by Hypsipyla (Whltnore 1976). Shade is nOllll3.lly provided by other species either planted concurrently with the M:liaceae or in the fom of residual stands into which the M:liaceae are line planted. Suitable mixtures have been investigated extensively in West Africa (Dupuy and Mille 1991); this is discussed m::>re fully under M:magarent in Chapter 5. But another species is not always required to produce the shade; S. macrophylla is being regenerated successfully at SUndapola in Sri lanka under the shade of mature trees lOClStly of the same species (M..lttiah 1991).

The establisl"lnent of M:liaceae susceptible to Hypsipyla under a nurse crop to provide shade is an obvious exanple of the use of mixtures in industrial plantations, rut it has to be noted that in francophone West Africa, where lOClSt recent work on the silvicultural managarent of M:liaceae has been carried out, the decision has been taken not to plant M:liaceae (Cossalter 1991). Ckl the other hand the Sundapola mahogany plantations were established very successfully in mixture and in the 801aron Islands it is proposed to establish S. macrophylla in a matrix of Securinega flexuasa (801aron Islands 1988 a and b).

In Kenya a canker on Cypress (Cupressus macrocarpa) , is caused by Seridium unicornis (the :inperfect state of RhynchospiJaeria cupressi). This fungus gains entry through wounds and pruning scars, rut has a limited range of effective dispersal and it would therefore appear that the proximity of trees in a pure plantation llUlSt contrib.lte to the spread of the disease. Mixed planting of Cupressus macr0ca.zp3 and Grevillea rorusta has been tried in Kenya (Graham 1945 and 1949), rut the managarent of such mixtures has proved difficult resulting in poor fom (rutt sweep and lean) of trees of both species. There was little evidence that the mixture controlled the disease. Eventually the decision was made to replace C. macr0ca.zp3 with C. lusitanica, a less vigorous species, rut which is less susceptible to cypress canker and which has a better fom.

In India and Pakistan the insect Hoplocerambyx spinicomis has changed fran being an inhabitant of felled logs and m::>rib.lnd trees of Shorea rorusta in natural forests to attacking healthy mature trees when that species was extensively established in pure plantations; the change in habits has been attrib.lted to the iIrproved opportunities for reproduction provided in plantations (Gibson and Jones 1977) and may owe sarething to increased food supplies and even to stress arising fran planting the species on an unsuitable site. In Nigeria Heoqphora testator, an insignificant pest of the natural forest, caused widespread damage to pure plantations of Nauclea diderrichii (Gibson and Jones 1977). Mixtures of Nauclea diderichii with Lovoo trichilioides and Entandrophragma utile have, tJa..lever, been successful (Lamb 1991; Lowe 1991).

In Africa, at least, the lOClSt iIrq:lortant and largest number of exanples of insect pests attrib.ltable to the establisl"lnent of IOC>nospecific plantations are defoliators, and to a lesser extent borers (Gibson and Jones 1977 ) . Nudaurelia cytherea, Orgya mixta and Pachypasa capensis were noted as exanples of defoliators of Brachystegia woodland, which have over a period of years adapted to and cause extensive damage pine plantations; Buzura edwardsi is another exanple. But there is no indication that mixed plantings will reduce

36

the attacks. In Malawi an attack of Plagiotriptuspinivora caused sufficientdamage to pine plantations to justify-control by aerial spraying (Gibson andJones 1977).

Conclusions on insects and diseases.

The evidence of serious losses due to pests or diseases resulting frommonospecific plantations is confusing. Gibson and Jones (1977), while statingon the one hand that the most pessimistic forecasts of traditional foresterson the dangers arising from forestmonocultures have been fully vindicated,were also able to give as their opinion that pest and disease prOblemsengendered by forest monocultures have seldom reached the catastrophic levelsof certain pests and diseases of natural forests or tree crops grown for non-commercial ends. This situation may be dhanging as more pest species areintroduced; for example three introduced species of conifer aphids havedevastated Pines and Cypresses in eastern and southern Africa. The pinewoollyaphid Pineuspini and the pine needle aphid Eulachnus rileyi were firstnoticed in 1968 while the cypress aphid Cinara cupressi was discovered in1986. They ni constitute a major threat to the future of conifers in theplantation programmes of the region, and the cypress aphid is also attadkingthe native conifers Jnniperus procera and Widdringtonia mdiflora (Ciesla1991; FAO 1991a).

It is to be noted that though most work on forest pathology andentomology is related to intensivelymanaged stands and little is known of therole of pests and pathagens in the ecosystems of most natural forests in thetropics, yet the knowledge on forest plantations still lags behind theknowledge of these prbblems in agrisystems (Gibson and Jones 1977).

Management that is based on a policy-of "high input/high output" will insiston answers being found which do not greatly-lower outputs and will ensure thatfinances are made available to find solutions. These solutions are likely-tobe either in the form of biological or chemical control or tree breeding todevelop resistant strains or through a change in the species. It is ofinterest that Peace (1957) discounted the possibility of spraying forests tocontrol diseases, but less than thirty-years later aerial spraying to controlDrothistram blight was standard practice in many young P. radiata plantationsinNewZealand (Chou 1981). It is also to be noted that the "law technology"solution of mixed planting to control Hypsipyla damage in francophone WestAfrica has apparently been abandoned.

Where uniformity of product is not so important andwhere less intensivemanagement is practised, as in many fuelwood plantations, then a "lawinput/law output" management poliqy will be more appropriate and mixedplantings are one of the possible solutions. In this case the establishmentof mixed plantings maybe used for "insurance" purposes, while most knowledgeis likely to be available.on appropriate mixtures of indigenous species. Inthe low technology situation where maintenance of ground cover is of as greator greater importance than economic return mixtures may be considered as aninsurance against complete failure.

It is recognized that until more is known about the mechanisms andstrategies of pests and diseases and of their predators in the natural foresttheremay be few, if any-benefits to be derived from the use of mixed speciesplantations to prevent or control the spreadof insects or diseases, and theremay even be disadvantages, for example,by providing alternative hosts orpossibly acting as barriers to predators (Chou 1981; Perry and Maghembe 1989).

36

the attacks. In Malawi an attack of Plagiotriptus pinivora caused sufficient damage to pine plantations to justify control by aerial spraying (Gibson and Jones 1977).

Cax:1nS;('I"IS on insects and diseases.

The evidence of serious losses due to pests or diseases resulting fran nonospecific plantations is confusing. Gibson and Jones (1977), while stating on the one hand that the roost pessimistic forecasts of traditional foresters on the dangers arising fran forest rronocultures have been fully vindicated, were also able to give as their opinion that pest and disease problems engendered by forest nonocultures have seldon reached the catastrophic levels of certain pests and diseases of natural forests or tree crops gr= for non­ccmrercial ends . This situation may be changing as rrore pest species are introduced; for example three introduced species of conifer aphids have devastated Pines and Cypresses in eastern and southern Africa. The pine woolly aphid Pineus pini and the pine needle aphid Eulachnus rileyi were first noticed in 1968 while the cypress aphid Cinara cupressi was discovered in 1986. They IlCM constitute a major threat to the future of conifers in the plantation progranmes of the region, and the cypress aphid is also attacking the native conifers Juniperus procera and Widdringtooia nodiflora (Ciesla 1991; F1IO 1991a).

It is to be noted that though roost work on forest pathology and entarology is related to intensively managed stands and little is known of the role of pests and pathogens in the ecosystems of roost natural forests in the tropics, yet the knowledge on forest plantations still lags behind the knowledge of these problems in agrisystems (Gibson and Jones 1977 ) . Managemmt that is based on a policy of "high input/high output" will insist on answers being found which do not greatly l~r outputs and will ensure that finances are made available to find solutions. These solutions are likely to be either in the fonn of biological or chemical control or tree breeding to develop resistant strains or through a change in the species . It is of interest that Peace (1957) discounted the possibility of spraying forests to control diseases, rut less than thirty years later aerial spraying to control Dothistrana. blight was standard practice in many young P . radiata plantatiOns in New Zealand (Chou 1981) . It is also to be noted that the "low technology" solution of mixed planting to control Hypsipyla damage in francophone West Africa has apparently been abandoned.

Where unifonnity of product is not so irrportant and where less intensive managemmt is practised, as in many fuelwood plantatiOns, .then a "low input/low output" managemmt policy will be rrore appropriate and mixed plantings are one of the possible solutions. In this case the establishrrent of mixed plantings may be used for "insurance" purposes, while roost knowledge is likely to be available ·on appropriate mixtures of indigenous species. In the low technology situation where maintenance of ground cover is of as great or greater irrportance than econanic return mixtures may be considered as an insurance against canplete failure.

It is recognized that until rrore is known about the mechanisms and strategies of pests and diseases and of their predators in the natural forest there may be few, if any benefits to be derived fran the use of mixed species plantations to prevent or control the spread of insects or diseases, and there may even be disadvantages, for exarrple,by providing alternative hosts or possibly acting as barriers to predators (Chou 1981; Perry and Maghembe 1989).

37

A major problem is the fact that modern communications facilitate thetransferof pests and disPases round the world. Protective systems which havebeen evolved in natural forests are very vulnerable to exotic organisms. Itis unlikely that mixtures will be effective in controlling epidemics of exoticorigins, therefore the best hope of control is the introduction of naturalenemies, breeding for resistance or chemical control - or a coMbination ofthese. Chemicals are more Pasily applied in pure plantations bit the need toprotect the environment frail pollution and the high cost makes this tactic ameasure of last resort.

3.6 CONCLUSIONS ON ENVIRONMENTAL IMPACT

Environmental impact has been considered under the separate heads ofsoil, climate, fire, wildlife, pests and diseases. These factors, and others,interact to form the forest ecosystem and it should be the objective of theforester to ensure that it is resistant to agents of change but that at thesane time the site retains its productive potential. The occurrence ofdevastating attacks by pests and diseases are often a symptom of poormanagement decisions, such as species selection or delayed thinning, and thesolution lies in good forestry practice. In these circumstances where basicmanagement errors have been made it is unlikely that a mixture will be of anyhelp in controlling an attadk. Mixed plantations are likely to be beneficialin projects managed extensively-and where there may be unpredictable pest ordisease attacks or climatic events. Mixed plantings are then an insuranceagainst complete failure and they may be effective in reducing thevulnerability of an indigenous species to an indigenous pest or disease,providing that it has been properly managed - see above - but the degree ofdispersal required may call in question the fPasibility of managing thatspecies intensively.

The possible deterioration in site fertility is in some ways a moreinsidious problem in that without a well maintained network of PermanentSample Plots the problemmay go unnoticed until fertility has been seriouslyimpaired. Even with a good monitoring system it is unlikely that sitedeterioration caused by a particular type of plantation, as indicated byChanges in yield, will be detected until the following rotation. Though thedetailed functioning of soil micro-flora and micro-fauna is not wellunderstood in the tropics, provided fertility problems are recognised in timethe action needed to prevent loss in fertility are well known:

retention of topsoil and organic matter when establishing plantations;

replacement of nutrients and restoration of physical condition afterharvesting, and

ensuring that crpp nutrient requirements do not exceed the sitecapacity by, for example, overstocking or as a result of litter buildup.

Mixed plantations are a management tool for influencing soil conditionsby providing ground cover to protect against soil erosion and moisture stressor to ameliorate topsoil conditions to favou_r beneficial micro-organisms. Themixture may be achieved by planting or by allowing a natural understorey toinvade under an open canopy. Plantation management, based on clear

37

A major problem is the fact that roodem camrunications facilitate the transfer of pests and diseases round the world. Protective systems which have been evolved in natural forests are very vulnerable to exotic organisms. It is unlikely that mixtures will be effective in controlling epidemics of exotic origins, therefore the best hope of control is the introduction of natural enemies, breeding for resistance or chemical control - or a canbination of these. Chanicals are m:>re easily applied in pure plantations rut the need to protect the environment fran pollution and the high cost makes this tactic a rreasure of last resort.

Environmental inpact has been considered under the separate heads of soil, climate, fire, Wildlife, pests and diseases. These factors, and others, interact to fom the forest ecosystem and it should be the objective of the forester to ensure that it is resistant to agents of change rut that at the sarna time the site retains its productive potential. The occurrence of devastating attacks by 'pests and diseases are often a synptan of poor managem:nt decisions, such as species selection or delayed thinning, and the solution lies in good forestry practice. In these circumstances where basic managem:nt e=rs have been made it is unlikely that a mixture will be of any help in controlling an attack. Mixed plantations are likely to be beneficial in projects managed extensively and where there may be unpredictable pest or disease attacks or climatic events . Mixed plantings are then an insurance against canplete failure and they may be effective in reducing the vulnerability of an indigenous species to an indigenous pest or disease, providing that it has been properly managed - see alxlve - rut the degree of dispersal required may call in question the feasibility of managing that species intensively.

The possible deterioration in site fertility is in sane ways a m:>re insidious problem in that without a well maintained network of Pennanent sample Plots the problem may go unnoticed until fertility has been seriously inpaired. Even with a good m:>nitoring system it is unlikely that site deterioration caused by a particular type of plantation, as indicated by changes in yield, will be detected until the follCMing rotation. Though the detailed functioning of soil micro-flora and micro-fauna is not well understood in the tropiCS, provided fertility problems are recognised in time the action needed to prevent loss in fertility are well knCMn:

retention of topsoil and organic matter when establishing plantations;

replacement of nutrients and restoration of physical condition after harvesting, and

ensuring that crop nutrient requirem=nts do not exceed the site capacity by, for exarrple, overstocking or as a result of litter ruild up.

Mixed plantations are a managem:nt tool for influencing soil conditions by providing ground cover to protect against soil erosion and m:>isture stress or to arreliorate topsoil conditions to favour beneficial micro-organisms. The mixture may be achieved by planting or by allCMing ,a natural understorey to invade under an open canopy. Plantation managem:nt, based on clear

38

objectives, can also pramote the conservation of animal and other geneticresources.

Fire is a serious and increasing hazard to plantations, with heavydirect and indirect costs. Investigations into the potential of mixtures ofspecies to reduce the incidence of fires or to slowdown their spread have notbeen documented bit would appear to be worth further study.

Because of the unpredictable nature of epidemics and climatic change themaintenance of genetic diversity in a plantation is essential. Diversity mayoccur at different levels; there is both diversity between species and withinspecies. Total diversity gives the stand a better chance to evolve to copewith new conditions and also gives same insurance against complete loss.Diversity, however, can also be achieved in the broad sense by having amixture of baocks or compartments rather than a mixture in the narrow sense.The decision whether to have mixed plantations in the narra sense must dependon the objectives of management. Intensive managerrent of industrialplantations will probably indicate pure plantations, while more extensivemanagement of, for example, fuelwood plantations may benefit frail mixtures andif the prime objective is rehabilitation then mixed planting will frequentlybe called for. But it must never be forgotten that management objectivesshould anly be set after due consideration of the potential and limitationsof the site and that objectives may have to be further mcdified in the lightof species available for the site. The maintenance of long termsustainabilityand site fertility is all too often given insufficient emphasisin plantation schemes (Lundgren 1980).

38

objectives, can also prarote the CXlI1SE!:rvation of animal and other genetic resources.

Fire is a serious and increasing hazard to plantations, with heavy direct and indirect costs. Investigations into the potential of mixtures of species to reduce the incidence of fires or to sl~ ~ their spread have not been documented rut w::>uld appear to be worth further study.

Because of the unpredictable nature of epidemics and climatic change the maintenance of genetiC diversity in a plantatien is essential. Diversity may occur at different levels; there is J::oth diversity ben-m species and within species. Total diversity gives the stand a better chance to evolve to cope with new ccnditions and also gives sane insurance against a::rrplete loss. Diversity, ~ver, can also be achieved in the broad sense by having a mixture of blocks or c:arpartnents rather than a mixture in the ~ sense. The decisien whether to have mixed plantations in the ~ sense Il1llSt depend en the objectives of managarent. Intensive managarent of industrial plantations will probably indicate pure plantations, while IOOre extensive managarent of, for exanple, fuelwood plantations may benefit fran mixtures and if the prime objective is rehabilitatien then mixed planting will frequently be called for . But it Il1llSt never be forgotten that managarent objectives should cnly be set after due consideratien of the potential and limitations of the site and that objectives may have to be further nodified in the light of species available for the site. The maintenance of long tenn sustainabilityand site fertility is all too often given insufficient arphasis in plantatien schanes (Lundgren 1980).

39

4. NON-INDUSTRIAL PRODUCTS AND SERVICES

Mixtures have not historically been used in plantations for theproduction of industrial wood products, but have generally been thought of asmore suitable for non-industrial products or the provision of environmentalservices. The special case of non-industrial products and services istherefore considered in this chapter.

Nan-connercial uses

It is now widely acknowledged that forests provide a wealth of productswhich are used by local communities living in or near them. Though some ofthe products arise from sources outside the forest - in compound farms,out lying farms or as fodder trees on farra boundaries - many are collected asa "free good" from the forest. It is evident that farmers have knowledge ofthe site and silvicultural requirements of the species grown in compounds andoutlying farms. But these species are usually raised in small plots in anagroforestry environment and have been excluded from consideration in thisstudy. In Nigeria (and prdbably most of the African humid tropics) theknowledge of the silvicultural requirements of the species collected from theforest is often laCking (Okafor 1977). No reference was found to theestablishment of mixed forest plantations in the humid tropics by localcommunities for the provision of the range of goods used by them or of theirdeliberate management of natural forests. This should not be taken to implythat there has been a complete absence of traditional management by localcommunities in tropical forests. SuCh management systems have existed buthave not been recorded. In countries that have passed through a period ofcolonialism traditional management systems have often been made unworkable byforesters and administrators, for instance:by-the creation of forest reservesand the imposition of forest rules which have ignored local managementsystems. Traditional management of natural forests has tended to concentrateon the organisation of the distribution of an available resource rather thanon the manipulation of the ecosystem in order to benefit any particularcomponent species. Where human population has created increased pressure onthe forest then traditional management systems tend to break down. In thecountries in the sub-tropics, such as Nepal, there is a better history ofcontrolled exploitation of forests by local communities, but again managementhas not really involved the manipulation of the forest to produce specific endproducts.

An added problem is that in many societies in the tropics there islittle respect for the natural forest, because the first requirement is tohave land for cultivation and because forest products are regardedas a freegood. Although the forest's worth may be appreciated, there is littlefeeling of individual responsibility for protecting the forest becausebenefits tend to be so widespread. Artificially-established plantations areoften treated with more respect than natural forest even when it is undermanagement.

It is generally recognized that the loss of natural forest in the humidtropics deprives local com-nunities of marw products, but there is insufficientknowledge to establish and maintain the plantations provide those products.Forestry projects have been criticized for replacing polyspecific naturalforests with mcnospecific plantations that do not produce the many otherproducts to be found in the natural forests. But if there is any pressure foragricultural land, the solution of protection and low intensity management of

39

Mixtures have not historically been used in plantations for the production of industrial VIOOd products, rut have generally been thought of as rrore suitable for non-industrial products or the provision of envirormental services. The special case of non-industrial products and services is therefore considered in this chapter.

It is naY widely acknaYledged that forests provide a wealth of products which are used by local carmunities living in or near than. Though sane of the products arise fran sources outside the forest - in carqJOUIJd fanns, outlying fanns or as fodder trees on fann boundaries - rranyare collected as a "free gcxxi" fran the forest . It is evident that fanners have knaYledge of the site and silvicultural requirarents of the species gravn in carqJOUIJds and outlying fanns. But these species are usually raised in small plots in an agroforestry environment and have been excluded fran consideration in this study. In Nigeria (and . probably rrost of the African humid tropics) the knaYledge of the silvicultural requirements of the species collected fran the forest is often lacking (Okaior 1977). No reference was found to the establishnent of mixed forest plantations in the humid tropics by local carmunities for the provision of the range of goods used by than or of their deliberate rranagemant of natural forests. This should not be taken to imply that there has been a ccrrplete absence of traditional rranagemant by local carmunities in tropical forests. Such rranagemant systems have existed rut have not been recorded. In countries that have passed through a period of colonialism traditional rranagemant systems have often been made unworkable by foresters and administrators, for instance by the creation of forest reserves and the imposition of forest rules which have ignored local rranagemant systems . Traditional rranagemant of natural forests has tended to concentrate on the organisation of the distril:lltion of an available resource rather than on the rranipulation of the ecosystem in order to benefit any particular ccrrponent species. Where human population has created increased pressure on the forest then traditional rranagemant systems tend to break davn. In the countries in the sub-tropiCS, such as Nepal, there is a better history of controlled exploitation of forests by local carmunities , rut again rranagemant has not really involved the rranipulation of the forest to produce specific end products .

An added problem is that in rrany societies in the tropics there is little respect for the natural forest , because the first requirement is to have land for cultivation and because forest products are regarded as a free gcxxi . Although the forest's worth may be appreciated, there is little feeling of individual responsibility for protecting the forest because benefits tend to be so widespread . Artificially established plantations are often treated with rrore respect than natural forest even when it is under rranagemant .

It is generally recognized that the loss of natural forest in the humid tropics deprives local carmunities of rrany products, rut there is insufficient knaYledge to establish and maintain the plantations provide those products. FOrestry projects have been criticized for replacing polyspecific natural forests with rronospecific plantations that do not produce the rrany other products to be found in the natural forests . But if there is any pressure for agricultural land, the solution of protection and laY intensity rranagemant of

40

the natural forest is usuallyimpossible. Since there is currently inadequateknowledge to establish mixed forest plantations to meet the requirements oflocal communities, the only possibility-left is to protect and manage an areaof natural forest in coMbination with a commercial, possibly monospecific,plantation project. The heavy requirements for fuel and poles can then be metfrcm the plantations, while the natural forest provides other products. Michmore needs to be known about the silvicultural requirements of the largenumbers of fruit trees, medicinal trees and herbs etc that the local communityuse, hit which may be only locally valued, before it will be possible toestablish mixed plantations which can also be used for the satisfaction ofsuch needs.

Fuelwood and poles .

By 1980 same 39% of plantations in Africa, Asia, South America and thePacific Islands1 were classified as non-industrial (FAO 1988). In theestimate of the area planted between 1981 to 1985 the proportion increased to46% (FAO 1988).

Mbst non-industrial plantations are established with the objective ofprcducingpoles or fuelwood. Usually the production is for a local market andaminimum of processing will be involved. There is, therefore, less incentiveto use highly mechanized harvesting techniques and as a consequenceplantations can be established on steeper and rodkier sites, unsuitable forindustrial plantations. Mixed plantations may thus be very suitable for theproduction of fuelwood and poles, provided suitable species are selected bothfor the site and to meet the user's requirements, hit unfortunately the lessfertile sites that are often available may limit the choice to a singlespecies. The experience in Nepal is described in more detail later in thischapter.

Fodder

Braase and fodder for livestodk are at a premium in any climate that hasa long dry season. Grass in woodland can be grazed and forests, particularlyon the hills with a higher rainfall, can be reserved for dry season fodder;grass can also be cut and carried to the livestock. Grass, however, dries upand dies early in the dry sPson, while tree foliage and fruits, for exampleAcacIaFcds, can remain palatable and nutritiousmuch longer. But the abilityof a tree to retain its 1PAves or pods varies with the species, therefore toensure a supply of fodder throughout the dry season a mixture of species isessential in order to have a sequence of species from those that shed theirleaves early in the dry season to evergreens, such as sane of the oaks(Cuercus semecarpifOlia for instance) and Ilex spp in the Himalayas.Relatively-little has been published on the management of tree fodder crops,hit same work is being done in Nepal (Gilmour et al 1989;1990; Applegate andGilmour 1987; Mohns et al. 1988).

Rehabilitation of degraded sites.

The af forestation of degraded sites in order to revegetate the area andto regain a gocd soil structure is increasingly being recognized as a f orestry

1 Excluding South Africa and also China and Argentina for which thereare no detailed data.

40

the natural forest is usually impossible. Since there is currently inadequate kncwledge to establish mixed forest plantations to meet the requirements of local CXIlIlIllIlities, the only possibility left is to protect and l!\3Ilage an area of natural forest in canbination with a a::mnercial, possibly IlOnospecific, plantation project. The heavy requirements for fuel and poles can then be met fran the plantations, while the natural forest provides other products. Much IlOre needs to be knc:wn about the silvicultural requirements of the large numbers of fruit trees, medicinal trees and herbs etc that the local CXIlIlIllIlity use, rut which may be only locally valued, before it will be possible to establish mixed plantations which can also be used for the satisfaction of such needs.

FUel.wood and poles .

. By 1980 sare 39% of plantations in Africa, Asia, South Anerica and the Pacific Islands l were classified as non-industrial (F7IO 1988). In the estimate of the area planted between 1981 to 1985 the proportion increased to 46% (F7IO 1988).

MOst non-industrial plantations are established with the objective of producing poles or fuelwood. Usually the production is for a local market and a mininrum of processing will be involved . There is, therefore, less incentive to use highly mechanized harvesting techniques and as a consequence plantations can be established on steeper and rockier sites, unsuitable for industrial plantations. Mixed plantations may thus be very suitable for the production of fuelwood and poles, provided suitable species are selected both for the site and to meet the user's requirements, rut unfortunately the less fertile sites that are often available may limit the choice to a single species. The experience in Nepal is described in IlOre detail later in this chapter.

Fodder.

Brc:wse and fodder for livestock are at a premium in any climate that has a long dry season. Grass in woodland can be grazed and forests, particularly on the hills with a higher rainfall, can be reserved for dry season fodder; grass can also be cut and carried to the livestock. Grass, ~ver, dries up and dies early in the dry season, while tree foliage and fruits, for exarrple Acacia pods, can remain palatable and nutritious much longer . But the ability of a tree to retain its leaves or pods varies with the species, therefore to ensure a supply of fodder throughout the dry season a mixture of species is essential in order to have a sequence of species fran those that shed their leaves early in the dry season to evergreens, such as sare of the oaks (Q:1ercus stmeCaIpifolia for instance) and Ilex spp in the Himalayas . Relatively little has been published on the l!\3Ilagement of tree fodder crops, rut sare work is being doile in Nepal (GilIrour et al 1989;1990; Applegate and GilIrour 1987; M:>hns et al. 1988).

Rehabilitation of degJ:aded sites.

The afforestation of degraded sites in order to revegetate the area and to regain a good soil structure is increasingly being recognized as a forestry

1 Excluding South Africa and also China and Argentina for which there are no detailed data.

41

objective in itself. In these circumstances law growing trees and shrubs,which can provide ground cover, may playas important a role as large trees.Nevertheless it is often difficult to protect and manage such sites,particularly-if there is any pressure for alternative (even if unsustainable)use for the land, unless it is possible for local communities to benefit fromtree products on the site. Therefore a mixture of ground cover and soilforming species with fodder, fuelwood, pole and tiMber species is desirable.

In Brazil experimental work has been done on rehabilitating degradedsites paying particular attention to the ecological requirements of eachspecies and the position in the ecological succession (Nogueira 1977; Duriganand Nogueira 1990). Results have been generally good bit an analysis ofsubsequent natural regeneration indicates that there will be a progressivetendency to a reduction in species diversity (ahether natural or induced) byin succeeding generations.

In India afforestation of dolomite mine overburden (Ram Prasad andCamire 1988) has been reported. Acacia auriculifOrmis, A. caqpylacantha,GMelina aztorea and Ibngamia pinnata showed slightly better height anddiameter growth when rnixed with bamboo; the growth of Albizia prooera wassomewhat retarded by bamboo. In Madhya Pradesh a bauxite mine site has beenrevegetatedwith Shorea robusta in mixture with Gtevillea robusta, EUcalyptuscamaldulensis, Tbona ciliata and linus kesiya (Ram Prasad 1988); the reasonfor selecting this very diverse mix of trees is not clear and no informationwas given on the success of the mixtures.

The shrub Hippophae rhamnoides (sea buckthorn) is frequently planted inmixture with forest trees in China. It is resistant to drought and cold andis valued for soil conservation and improvement due to its nitrogen-fixingability as well as for its fruits (which are rich in vitamin C) and otherproducts such as fuelwood, fodder, medicines and oil. The shrtb is raixed withlbpulus spp. in soil conservation works and in shelterbelts, but although60 000 ha of the species are planted yearly there is no estimate of the amountplanted in mixture, nor of the possible relative advantages such mixturesmight have over pure plantations. The tree Robinia pseudoacacia (falselocust) is also used in mixture with poplar in China. In neither case haverecords been found of improvements in the growth of the main tree crop, norof increased production fram the site, when compared with the poplar grownalone.

Shelterbelts and windbreaks.

This function has been mentioned in the section on climate. Becausewindbreaks are usually planted to protect crops, they need to be narrow inorder to minimize the area of land taken out of agricultural production, bitin order to reduce turbulence a windbreak should be triangular in crosssection rather than a tall straight sided barrier. A mixture of species ofvarying heights at maturity will achieve the desired cross section shape andare also likely to filter the wind better than a dense paanting of a singlespecies. In Kano, Nigeria, shelterbelts were planted with eight central rowsof Eucalyptus camaldulensis and four rows of another species on either side.The other species included Acacia spp, Azadirachta indica and Anacardiumoccidentale (suited to the more humid sites), the intention being to fell halfthe widthat age eight and then alternative halves every four years to producepoles and firewood (Lowe 1991).

41

objective in itself . In these circumstances 1= groNing trees and shrubs , which can provide ground rover, rray playas :inportant a role as large trees . Nevertheless it is often difficult to protect and rranage such sites, particularly if there is any pressure for alternative (even if unsustainable) use for the land, unless it is possible for local carmunities to benefit fran tree products on the site . Therefore a mixture of ground rover and soil fonning species with fodder, fuelwood, pole and t:irober species is desirable .

In Brazil experimantal work has been done on rehabilitating degIaded sites paying particular attention to the erological requirarents of each species and the position in the erological succession (Nogueira 1977; Durigan and Nogueira 1990) . Results have been generally good but an analysis of sul::sequent natural regeneration indicates that there wi ll be a progressive tendency to a reduction in species diversity (whether natural or induced) by in succeeding generations .

In India afforestation of dolanite mine overburden (Ram Prasad and camire 1988) has been reported. Acacia auriculifo:rmis, A. carrpylacantha, GrJelina a.r.ro.rna and Poogamia pinnata showed slightly better height and diarreter grCMth when mixed with bamboo ; the grCMth of Albizia p:roceza was saoowhat retarded by bamboo . In Madhya Pradesh a bauxite mine site has been revegetated with Sbo.rna rol:xlsta in mixture with GIevillea rol:xlsta, Eucalyptus camaldulensis, 7boI1a ciliata and Pinus kesiya (Ram Prasad 1988); the reason for selecting this very diverse mix of trees is not clear and no inforrration was given on the success of the mixtures.

The shrub Hippophae rhamnoides (sea buckthorn) is frequently planted in mixture with forest trees in China . It is resistant to drought and rold and is valued for soil ronservation and improvement due to its nitrogen-fixing ability as well as for its fruits (which are rich in vitamin C) and other products such as fuelwood, fodder, roodicines and oil. The shrub is mixed with Populus spp . in soil ronservation works and in shelterbelts, but although 60 000 ha of the species are planted yearly there is no estirrate of the arrount planted in mixture, nor of the possible relative advantages such mixtures might have over pure plantations . The tree Robinia pseudoacacia (false locust) is also used in mixture with poplar in China. In neither case have reroros been found of improvements in the grCMth of the rrain tree crop, nor of increased production fran the site, when a::nprred with the poplar grown alone .

Sbelterhelts and windbreaks.

This function has been rrentioned in the section on clirrate. Because windbreaks are usually planted to protect crops, they need to be narrc:M in order to minimize the area of land taken out of agricultural production, but in order to reduce turbulence a windbreak should be triangular in cross section rather than a tall straight sided barrier . A mixture of species of varying heights at rraturity will achieve the desired cross section shape and are also likely to filter the wind better than a dense planting of a single species . In Kana, Nigeria, shelterbelts were planted with eight central rCMS of Eucalyptus camaldulensis and four rCMS of another species on either side . The other species included Acacia spp, Azadirachta indica and Anacaz:dium occidentale (suited to the more humid sites), the intention being to fell half the width at age eight and then alternative halves every four years to produce poles and firEMJOd (lave 1991) .

Urban and periurban planting.

Trees in cities improve the microclimate and cut noise transmission.Periarbanplanting is not only an ipportant amenity, but in arid and semi-aridareas can reduce wind and dust in the city. Both urban and periurbanplantings are at risk from the unpredictable effects of air pollution. Amixture of species is desirable both from the arrenity point of view, to avoidthe appearance of uniformity, and in order to increase the chance of survivalof same tree cover in the event of biotic or abiotic damage. The severeimpact of ozone pollution on natural forests of AJoies religiosa in the hillsround Mexico city has been noted earlier as has the damage done to Pinusjeffreyi in the San Bernardino Mountains of California where incense cedar((7-97ocedrus deourrens) and white fir (Abies amabilis) have survived largelyunscathed.

Same examples of non-industrial plantations

Cammunity forestry in Nepal

There has been a tradition of controlled exploitation by the localccurnunities in the hills of Nepal, but controls have broken dawn and excessiveexploitation has reduced many hillside forests to over-grazed grasslandcarrying a few heavily lopped stumps. A reforestation programme was initiatedin the nineteen seventies; much of the early planting was with native chirpine (Pinus roxburghli). It was found that once a site was closed to grazingthere was a good regeneration of hardwccds such as Schima wallichii from oldstumps, from suckers and later from seed. These hardwoods have very muchhighervalue to the local communities for fodder, firewood and farm implementsthan pine has. Since 1979 the Nepal/Australian Forestry Project has beenrunning experiments to see haw pine/hardwood mixtures can be managed toproduce different end products and to determine their yields. The optionstested have been to thin to favour the pines or the hardwoods in variousproportions or to coppice the hardwoods (Gilmour et al. 1989,1990; Applegateand Gilmour 1987; 1988; MOhns et al 1988). Enrichment planting has beenincluded and the whole operation is more a matter of enrichment planting intogrossly over-exploited natural woodland than establishment of mixedplantations. It is too early to draw defini-te conclusions, but there are samegeneral lessons to be learned from this experience which can be applied to thecommunity forestry elsewhere and in particular to assisting local people inmaking the choice between mixed or pure plantations:

it is essential to include the local communities in the management andplanning of the established woodlots;

if the community is.to make an informed contribution to managementplanning it must have a clear idea of the options, therefore demonstrationplots are required;

prescriptions must be simple, but there is no particular problem inmanipulating the species mixtures to the extent of varying the proportion ofpines and broadleaf species.

4242

Urban and periurban planting.

Trees in cities :ilrprove the microclimate and cut noise transmission. Periurban planting is not only an iIrp:>rtant amenity, rut in arid and semi -arid areas can reduce wind and dust in the city. Both urban and periurban plantings are at risk fran the unpredictable effects of air pollution. A mixture of species is desirable roth fran the amenity point of view, to avoid the appearance of unifonnity, and in order to increase the chance of survival of same tree cover in the event of biotic or abiotiC damage. The severe :ilrpact of ozone pollution on natural forests of Abies religiosa in the hills round Mexico city has been noted earlier as has the damage done to Pinus jeffreyi in the San Bernardino M:>untains of california where incense cedar (Calocedrus decurrens) and white fir (Abies amabilis) have survived largely unscathed.

Salle exanpl es of nco-:i.Jd.Jstrial plantatiorls

Ccrmrunity forestry in Nepal

There has been a tradition of controlled exploitation by the local carmunities in the hills of Nepal, rut controls have broken CbIn and excessive exploitation has reduced many hillside forests to over-grazed grassland carrying a few heavily lopped sturrqlS . A reforestation prog:ranne was initiated in the nineteen seventies; IlUlch of the early planting was with native chir pine (Pinus IOXWrghii). It was found that once a site was closed to grazing there was a good regeneration of hardwoods such as SChima wallichii fran old sturrqlS, fran suckers and later fran seed. These hardwoods have very IlUlch higher value to the local carmunities for fodder, firewood and fam :ilrplements than pine has. Since 1979 the Nepal/Australian Forestry Project has been running experiments to see heM pine~ mixtures can be managed to produce different end products and to detennine their yields. The optiOns tested have been to thin to favour the pines or the hardwoods in various proportions or to coppice the hardwoods (Gillrour et al. 1989,1990; Applegate and Gilm::>ur 1987; 1988; M:>hns et al 1988). Enrichrent planting has been included and the whole operation is IOOre a matter of enrichrent planting into grossly over-exploited natural woodland than establishment of mixed plantations . It is teo early to draw definite conclusions, rut there are same general lessons to be learned fran this experience which can be applied to the carmunity forestry elsewhere and in particular to assisting local people in making the choice bebYeen mixed or pure plantations:

it is essential to include the local carmunities in the management and planning of the established woodlots;

if the carmunity is · to make an infonned contril::ution to management planning it IlUlSt have a clear idea of the options, therefore daoonstration plots are required;

prescriptions IlUlSt be s:ilrple, rut there is no particular problem in manipulating the species mixtures to the extent of varying the proportion of pines and broadleaf species.

Rattan.

Rattans, which are a family of cliMbing palms, are exploited both tosatisfy the needs of local communities and as a major export crop framIndonesia and Malaysia in particular. Of the small carie rattans only Calamuscaesius and C. trachycoleus are planted extensively in the rainforest belt ofthis region. They are cluster rattans and C. caesius has traditionally beentreated as a crop of shifting cultivation, being harvested completely at ageseven to ten years and again at the end of the fallow period at about agefourteen. If, however, the clusters are harvested selectively in alternateyears, they can be managed on a sustained yield basis for many years(Dransfield 1979).

Canes are usually cultivated in secondary forest, bit they have beenraised successfully in abandoned rUbber plantations and even in a Rinusoccarpa plantation and a Shorea robusta plantation in Bangladesh (Davidson1986). Themanipulation of the shade is critical to the production of qualityrattan; too much shade, for example under Dillenia spp., results in poorgrowth of the rattan, bit with longer internodes, which is a desirablefeature. In Sabah, Fast Malaysia the yield of Clamus trachycoleus after 11years has been estimated at 2.5 tons/ha/year with a sale value of US$800/tonunprocessed and US$1 500/ton processed (Dransfield 1988).

C. manan is usually grown for the production of large canes; thisspecies is not a cluster rattan and does not shoot frcn the base after cut-tingand therefore can only be cut once. Other large cane rattans which do formclusters, e. g. C. inermis or C. merrillii from the Philippines are possiblealternatives. Another problem with C. manan is that the its weight (it cangroka to 180 m in length) can break supporting trees. Other rattans are grownin India and Sri Lanka and there is even one African species of rattan.

Rattanwould appear to offer attractive financial returns, up to aboutUS$3 500/ha/year gross after only 11 years, with few management expenses. Ithas to be grown in mixture, but to what extent the other species of the cropcan contribute to returns is not clPar. The options would appear to be eitherto consider the rattan to be a component of the early secondary successionalstage-of the ecosystem and to accept that it will be replaced in laterstages, or to attempt to manipulate the canopy in order to retain itthroughout a longer rotation, or to maintain the plantation in an early stageof succession to favour the rattan at the expense of other components of thecrop. There is scope for further investigation.

Sandalwood (see also Appendix 4)

Sandalwood is a root hemi-parasite that can grow in association with awide range of hosts, including grasses. The genus occurs in India, Australiaand the Pacific basin. There are fourteen species, bit the most valuable andone of the most vigorous is Santa/um album which occurs naturally in India andin West Timor, Indonesia; this species is ni being planted in WesternAustralia and also in many of the Pacific Islands, where indigenous specieshave been heavily exploited.

Sandalwoodis one of the most valuable timbers on the world market. Itis used for carving in India for which use it can fetch up to $US 9 400 pertonne. Australian grown sandalwood is mostly sold on the Far FAst market forincense and even wood chips and powder can command prices of about $US 2 300

4343

Rattan.

Rattans, which are a family of climbing palms, are exploited roth to satisfy the needs of local c:cmmmities and as a major export crop fran Indonesia and Malaysia in particular. Of the small cane rattans only caJ.amus caesius and c. trachy=leus are planted extensively in the rainforest belt of this region. They are cluster rattans and c. caesius has traditionally been treated as a crop of shifting cultivation, being harvested c:arpletely at age seven to ten years and again at the end of the fallCM period at about age fourteen . If, lJa.Iever, the clusters are harvested selectively in alternate years, they can be managed on a sustained yield basis for many years (Dransfield 1979).

Canes are usually cultivated in secondary forest, rut they have been raised successfully in abandoned rubber plantations and even in a Pinus oocarpa. plantation and a Shorea roblsta plantation in Bangladesh (Davidson 1986) . The manipulation of the shade is critical to the production of quality rattan; too Irnlch shade, for exarrple under Dillenia spp . , results in poor grCMth of the rattan, rut with longer internodes, which is a desirable feature. In Sabah, East Malaysia the yield of Calamus trachy=leus after 11 years has been estimated at 2 . 5 tons/ha/year with a sale value of US$800/ton unprocessed and US$l 500/ton processed (Dransfield 1988).

C. manan is usually grCMIl for the production of large canes; this species is not a cluster rattan and does not shoot fran the base after cutting and therefore can only be cut once. Other large cane rattans which do fonn clusters, e.g. C. inezmis or C. merrillii fran the Philippines are possible alternatives . Another problen with C. manan is that the its weight (it can grCM to 180 In in length) can break supporting trees. Other rattans are grCMIl in India and Sri Lanka and there is even one African species of rattan.

Rattan would appear to offer attractive financial returns, up to about US$3 500/ha/year gross after only 11 years, with few managem:mt expenses. It has to be grCMIl in mixture, rut to what extent the other species of the crop can contriOOte to returns is not clear. The options would appear to be either to consider the rattan to be a c:arponent of the early secondary successional stage · of the ecosysten and to accept that it will be replaced in later stages, or to attarpt to manipulate the canopy in order to retain it throughout a longer rotation, or to maintain the plantation in an early stage of succession to favour the rattan at the expense of other c:arponents of the crop . There is scope for further investigation.

Sandalvo:rl (see also Appendix 4)

Sandalvo:rl is a root heni -parasite that can grCM in association with a wide range of hosts, including grasses . The genus occurs in India, Australia and the Pacific basin . There are fourteen speCies, rut the m:JSt valuable and one of the m:JSt vigorous is Santalum alliJm which occurs naturally in India and in West T:im:>r, Indonesia; this species is nCM being planted in Western Australia and also in many of the Pacific Islands, where indigenous species have been heavily explOited.

Sandalvo:rl is one of the m:JSt valuable timbers on the world market. It is used for carving in India for which use it can fetch up to $US 9 400 per tonne . Australian grCMn sandalvo:rl is m:JStly sold on the Far East market for incense and even vo:rl chips and pooder can ccmnand prices of about $US 2 300

44

per tonne. Sandalwood oil sells on the European and North American marketsat sus 1 500 per kg.

It has been found that establishment can be improved if a primary hostis used in the nursery, but that in the field the sandalwood and its primaryhost should be planted out near to a secondary host, usually a larger, morevigorous species. The primary host should be a low growing shrUb, sudh asCajanus ca jan or Séstania grandiflora; Acacia spp, Albizia spp and otherlegumes such as Bauhiniabiloba, Ealberyia sissoo and TerminaLiaspp have beenfound suitable, but Pinus caribaea and Araucaria spp have been recorded asgiving poor results.

Conclusions on non-industrial products and services

The inclusion of species that provide non-industrial products andservices inplantations is an important way in which the needs of rural peoplefor many forest products can be met and in which they can be involved in theproduction of goods for use elsewhere, such as in the growing of rattan orsandalwood. It is likelythat there is a far wider range of such species thanhas been reported here, which suggests not that the demand for their productsdoes not exist but that they have not been adequately investigated with a viewto incorporating them in single species plantations as a form of enrichmentplanting.

44

per tonne. SandalYlOOd oil sells on the European and North Airerican markets at $US 1 500 per kg .

It has been found that establislment can be improved if a primary host is used it1 the nursery, rut that in the field the sandalYlOOd and its primary host should be planted out near to a se=nda.ry host, usually a larger, JOC)re vigorous species. The primary host should be a low growing shrub, such as Cajanus cajan or Sesbania grandiflora; Acacia spp, Albizia spp and other legumes such as Bauhinia bilob:J, Dalbergia sissoo and Terminalia spp have been found SUitable, rut Pinus caribaea and Araucaria spp have been recorded as giving pcor results.

Concl.usi ems OIl DOD-industrial procmcts and services

The inclusion of species that provide non-industrial products and services in plantations is an important way in which the needs of rural people for many forest products can be mat and in which they can be involved in the production of goods for use elsewhere, such as in the growing of rattan or sandalYlOOd. It is likely that there is a far wider range of such species than has been reported here, which suggests not that the demand for their products does not exist rut that they have not been adequately investigated with a view to inCOI:pOrating than in single species plantations as a fom of enriclment planting.

5. THE MAMGEMINT OF MIXTURES.

There are two important sources which review the classification ofmixtures, methods of achieving them and their success:

The Indian Forest Service in the fourth and fifth SilviculturalConferences in Dehra Dun in 1934 and 1939. The minutes of these conferencesgive an extensive account of experiences and logical guidelines forestablishing forest plantations in mixture in the Indian subcontinent.

The Centre Technique Forestier Tropical has studied the subject in WestAfrica and various reports and papers have been brought together in a chapterof FAO Forestry Paper no. 98 - Les Plantations a Vocation de Bois d'Oeuvre enAfrique Intertropical amide (TiMber Production Plantations in the amidTropics of Africa) (FAO 1991b). A classification and criteria for selectingand managing mixtures are given.

These two sources are complementary and come to similar conclusions.The following classification is drawn from both sources.

A Classification of mixtures.

No classif ication of plantation mixtures is entirely satisfactory, sinceclasses of mixtures are not discrete, but tend to grade from one to anotherin a spectrum, depending on site and the degree of silvicultural intervention.The following classification, based on stand structure and the duration of themixture relative to the rotation, is proposed:

Two-layered canopy.1.1. Temporary mixture, end result moncspecific.1.2. Permanent, end result multi-specific.

Single-layered canopy.Generally permanent mixture, end result multi-specific.

In general reference will be made to mixtures of two species; morecomplex mixtures are possible bit the management of even two species in aplantation is not easy and each adriitional species campounds the difficulties.

1. Two layered canopy.

1.1. Temporary mixtures, designed to become monospecific before theend of the rotation.

Nurse Crops are used to bring a more valuable species through adifficult establishment stage. The most common circumstances in whichthey are used are to protect against adverse climatic factors - frost,insolation - or to deter insect attacks. In temperate zones the use ofnurse crops to give frost protection is well known and they are of usefor this purpose in parts of the subtropics such as the Himalayas. Inthe tropics the use of fast growing trees to nurse valuable species ofthe family 1461iaceae and other species such as Milicia (=Chlorpphora)excelsa through the stage in which they are at risk of attadk fromshoot borers is common. Few references to investigations into theeffectiveness of this strategy were found, but the borers are thoughtto be inhibited by shade. The Sundapola SWietenia macrqphylla(mahogany) plantations in Sri Lanka are a goal example of the

4545

5. '!HE MI\NI\GDmfT OF KIn'URES.

There are two iJrportant sources which review the classification of mixtures, methods of achieving than and their success:

The Indian Forest Service in the fourth and fifth Silvicultural Conferences in Dehra Dun in 1934 and 1939. The minutes of these conferences give an extensive account of experiences and logical guidelines for establishing forest plantations in mixture in the Indian subcontinent.

The Centre Technique Forestier Tropical has studied the subject in West Africa and various reports and papers have been brought together in a chapter of ~ Forestry Paper no. 98 - Les Plantations a Vocation de Bois d'Oel1V1:"e en Afrique Intertropical Humide (Timber Production Plantations in the Humid Tropics of Africa) (~1991b). A classification and criteria for selecting and rranaging mixtures are given .

These two sources are canplementary and cane to similar conclusions. The follCMing classification is drawn fran both sources .

A Classification of mixtures.

No classification of plantation mixtures is entirely satisfactory, since classes of mixtures are not discrete, rut tend to grade fran one to another in a spectrum, depending on site and the degree of silvicultural intervention. The follCMing classification, based on stand structure and the duration of the mixture relative to the rotation, is proposed:

1 . 'lWo-layered canopy. 1.1. Temporary mixture, end result rronospecific. 1.2. Pennanent, end result multi-specific .

2. Single-layered canopy. Generally pennanent mixture, end result multi-specific.

In general reference will be made to mixtures of two species; lOOre canplex mixtures are possible rut the rranagement of even two species in a plantation is not easy and each additional species canpounds the difficulties.

1 . TWo layered canopy.

1.1. Temporary mixtures, designed to becane rronospecific before the end of the rotation.

Nurse Crops are used to bring a lOOre valuable species through a difficult establishrrent stage. The lOOSt camon circumstances in which they are used are to protect against adverse climatic factors - frost, insolation - or to deter insect attacks . In temperate zones the use of nurse crops to give frost protection is well known and they are of use for this purpose in parts of the subtropics such as the Himalayas. In the tropics the use of fast grCMing trees to nurse valuable species of the family Meliaceae and other species such as Milicia (=Chlorophora) excelsa through the stage in which they are at risk of attack fran shoot borers is camon. Few references to investigations into the effectiveness of this strategy were found, rut the borers are thought to be inhibited by shade. The Sundapola SWietenia macrophylla (mahogany) plantations in Sri Lanka are a good exarrple of the

46

successful use of nurse crops, though the opinion in the Dehra Dunconference (1939) was that teak:Swietenia macrophylla mixtures were notsuccessful in India and Sri Lanka. The pure mahogany plantations ofFiji and Martinique were, however, successfully raised without thebenefit of a nurse crop and evidently without large-scale attadk byborers.

An understanding of the succession of species in the local ecosystemwill often help in the selection of nurse species. Milicia (=Chlorophcra)excelsa and Ebtandrophragma grandifOlicla were established successfully infire prone Terminalia woodland using Ihyllanthus discoideus as a nurse crop(Dawkins 1949). After forty years, though the site has suffered severalvicissitudes, the AL excelsa and E. grandifOliola are reported to have donewell on moisture receiving microsites.

In Nepal there is an interesting variation on nurse crops. There theplanting of pines in village afforestation schemes defines very cle4Arly thearea to be reforested and thereby makes the protection of the site againstunplanned cutting by the villagers and unmanaged browsing by their cattlesimpler and more effective. Often there is no need to fence. As a resultthere has been satisfactory regeneration of the more valuable hardwoods underthe pine canopy. Subsequently, the pines can be removed or allowed to growon as a further component in a mixed hardwood stand (Gilmour et al 1990).

Silvicultural reasons, in order to improve the form of the main crop.This may be an effect of spacing, and it has not been scientificallytested, but the form of Iterocarpus dalbergicides in the AndamanIslands is considered to be improved when the tree is gran through anoverstorey of Lagerstrcemia hypoleuca, Terminalia bialata etc.Dalbergia latifOlia is similarly improved by growing through anoverstorey (Indian Fbrest Service 1939).

In-fillers can be used if there is a shortage of the main species, orthe main species is expensive or difficult to establish. In that cAsethe main crop can be planted at wide spacing in a matrix of cheap in-fillers whidh can suppress weeds, supply side shade to the main crop orprovide ground cover to protect the soil. In Indonesia Altingiaexcelsa, Schima wallichii var. noronhae, Eugenia pcdyantha wererecommended for planting under Tbcna sureni, in order to provide groundcover with wood production as only a secondary objective (Grutterink1930).

In many respects these three functions of nurse crops, silviculturalimprovement and in-filler can be achieved by enrichment planting in forestsin the humid tropics. The naturally-occurring law value residual species incut-over forest have a nursing, cultural or in-filling function, though theadvantage of the latter is seriously-reduced by the prevalence of climbers onmany sites. It is hard to find examples where enrichment planting toestablish industrial plantations can be considered an unqualified economicsuccess. There was some optimism that trials involving group planting ofMesopsis eminii and the exploitation of the residual forest for Charcoalwould be profitable (Earl 1968), but there have been no recent reports of thiswork. On the other hand, introduced species, such as Albizia chinensis, Akdiaazedarach,AU/detia dura and in particular Maesopsis eminii have invaded thenatural forest in the East UsaMbara mountains of Tanzania, where they are nowcarpeting with the indigenous species (Binggeli and Hamilton 1990). Hbwever,

46

successful use of nurse crops, though the opml.On in the Dehra Dun conference (1939) was that teak :SWietenia macrophylla mixtures were not successful in India and Sri Ianka. The pure mahogany plantations of Fiji and Martinique were, halever, succes~fully raised without the benefit of a nurse crop and evidently without large-scale attack by borers .

An understanding of the succession of species in the local ecosystem will often help in the selection of nurse species . Milicia (=Chlorophora) excelsa and Entandrophragma grandifoliola were established successfully in fire prone 7ezminalia ~ using Phyllanthus dis=idEus as a nurse crop (Dawkins 1949). After forty years, though the site has suffered several vicissitudes, the M. excelsa and E. grandifoliola are reported to have done well on !lOisture receiving microsites .

. In Nepal there is an interesting variation on nurse crops. There the planting of pines in village afforestation schemes defines very clearly the area to be reforested and thereby makes the protection of the site against unplanned cutting by the villagers and unmanaged broosing by their cattle sinpler and !lOre effective . Often there is no need to fence. As a result there has been satisfactory regeneration of the !lOre valuable hardwoods under the pine canopy. Subsequently, the pines can be removed or allCMed to grcM on as a further c::arp:>nent in a mixed hardwood stand (Gilm:Jur et al 1990).

Silvicultural reasons, in order to inprove the fonn of the main crop. This may be an effect of spacing, and it has not been scientifically tested, rut the fonn of Fterocarpus dalbergioides in the Andaman Islands is considered to be inproved when the tree is g= through an overstorey of Lagerstroemia hypoleuC8, 7ezrninalia bialata etc. D3 ltergia latifolia is similarly inproved by grcMing through an overstorey (Indian Forest Service 1939) .

In-fillers can be used if there is a shortage of the main species, or the main species is expensive or difficult to establish. In that case the main crop can be planted at wide spacing in a natrix of cheap in­fillers which can suppress weeds , supply side shade to the main crop or provide ground cover to protect the soil . In Indonesia Altingia excelsa, Schima wallichii var. noIOllhae, Eugenia polyantha were recx:rrrrended for planting under 1bona sureni, in order to provide ground cover with wood production as only a secondary objective (Grutterink 1930) .

In many respects these three functions of nurse crops, silvicultural inprovement and in-filler can be achieved by enrichment planting in forests in the humid tropiCS. The naturally occurring lCM value residual species in cut-over forest have a nursing, cultural or in-filling function, though the advantage of the latter is seriously reduced by the prevalence of clilnbers on many sites . It is hard to find exanples where enrichment planting to establish industrial plantations can be considered an unqualified ec:onanic success. There was sore optimism that trials involving group planting of Maesopsis aninii and the exploitation of the residual forest for charcoal would be profitable (Earl 1968) , rut there have been no recent reports of this work. On the other hand, introduced speCies, such as Albizia chinensis, Melia azedarach, Milletia dura and in particular Maesopsis eminii have invaded the natural forest in the East Usambara !lOuntains of Tanzania, where they are nCM a::npeting with the indigenous species (Binggeli and Hamilton 1990). However,

47

where the prime objective is not so much wood production as the maintenanceof a diverse ecosystem, enrichment planting is to be recommended because thesoil is not put at risk during the establishment process.

Early economic returns can sometimes be obtained through the use ofmixtures when the main crop is a valuable, but slaw growing, shadebearer having no value as thinnings. An early-return from an admixtureof a fast growing species can make a project economically moreattractive. In India and Myanmar the planting of 21lia dolabriformiswith teak was not considered a success (Indian Forest Service 1939),but as the teak which tended to suppress the X. dolabriformis wasrather more valuable the failure was not too serious, especially as themixture had the effect of spacing the teak out at a period when it wascustomary to plant teak too close. In Nigeria the establishment ofLovaa trichilioides and Entandrophragva utile with Naucleawhich can be exploited for poles at the age of 15 years, was considereda success (LaMb 1991; Lowe 1991). In the Solomon Islands experimentshave been instituted for raising SWietenia nacrophylla in a matrix ofSecurinega flexuosa, which has a ready market as house poles at agefive or six and is also expected to reduce the incidence of Hypsipylashoot borer in the Mahogany (Solomon Islands 1988a).

The timing of the removal of the temporary crop and the care needed toensure that the main crop is not damaged during removal of the nurse trees isof great importance.

1.2. Permanent mixtures

Understorey for soil improvement. The necessity for maintaining theorganic matter content of the topsoil and the conditions under which itcan be expected to be depleted, for example through the huid up oflitter (Mbrris 1986) or litter removal byfire under teak (Bell 1973),have been noted in the section on soils. Some species have leaves thatbreakdown more easily and provide a better environment for microfaunaand flora which are the main agents for converting litter to organicmatter in the soil. Themixtare of other species with Cordia alliodozain Costa Rica has been shown to increase the rate of decomposition ofthe C. alliodacza leaves markedly (Babbar and Ewel 1989). Theintroduction of understorey species into the teak plantations inIndonesia in the early part of the twentieth century was largelymotivated by a desire to improve soils or hydrological conditions,though the production of more saleable wood from the understorey wasalso considered an essential requirement of understorey planting.ppinions were sharply divided on the necessity or utility of plantingmixtures. Pythe nineteen thirties evidence had been collected to showthat the planting of mixtures was unprofitable in economic terms (Hart1931a) and that an economically better, but ecologically similar,result could be achieved by encouraging a natural understorey (KUnst1918). It was suggested that the beneficial effects of an understoreyof Leucaena sp. could be attributed to the effects of the cultivationrather than to the species (Hart 1931b). In north-east Zambia the ladkof a deep litter layer under twenty year old Rkesiya (18 m. tall; 23an dbh; soil pH 6.2) was associated with an open canopy and a goodground cover including Desmcdium ascendens var. robustum andgphenostylis marginata and the presence of earthworms (Lawton 1991). '

47

where the prirre objective is not so llUlch wood production as the maintenance of a diverse ecosystem, enriclmant planting is to be reccmrended because the soil is not put at risk during the establishment process .

Early econanic returns can scmatirres be obtained through the use of mixtures when the main crop is a valuable, rut SICM grCMing, shade bearer having no value as thinnings . An early return fran an admixture of a fast grCMing species can make a project econanically rn:>re attractive. In India and Myanmar the planting of Xylia dolabrifoIIllis with teak was not considered a success (Indian Forest Service 1939), rut as the teak which tended to suppress the X. dolabrifoIIllis was rather rn:>re valuable the failure was not too seriOUS, especially as the mixture had the effect of spacing the teak out at a period when it was custanary to plant teak too close . In Nigeria the establistment of Lovoa trichilioides and Entandrophragma utile with Nauclea diderrichii, which can be exploited for poles at the age of 15 years, was considered a success (Lamb 1991; ~ 1991). In the Solaron Islands experirrents have been instituted for raising SWietenia macrophylla in a matrix of Securinega flexuosa , which has a ready market as house poles at age five or six and is also expected to reduce the incidence of Hypsipyla shoot borer in the Mahogany (Solaron Islands 1988a) .

The timing of the renoval of the teng:JOrary crop and the care needed to ensure that the main crop is not damaged during renoval of the nurse trees is of great importance.

1.2 . Pennanent mixtures

Understorey for soil improvemant. The necessity for maintaining the organic matter content of the topsOil and the conditions under which it can be expected to be depleted, for exa:rrple through the ruild up of litter (Mo=is 1986) or litter renoval by fire under teak (Bell 1973), have been noted in the section on soils. Sane species have leaves that break dCMn rn:>re easily and provide a better environrrent for microfauna and flora which are the main agents for converting litter to organic matter in the soil. The mixture of other species with Cordia alliodora :in Costa Rica has been shcMn to increase the rate of decanposition of the C. alliodora leaves markedly (Rabrer and Ewel 1989). The introduction of understorey species into the teak plantations in Indonesia in the early part of the tYientieth century was largely rn:>tivated by a desire to improve soils or hydrological conditions, though the production of rn:>re saleable wood fran the understorey was also considered an essential requirem:mt of understorey planting. Opinions were sharply divided on the necessity or utility of planting mixtures . By the nineteen thirties evidence had been =llected to shCM that the planting of mixtures was unprofitable in e=nanic tenns (Hart 1931a) and that an e=nanically better, rut e=logically similar, result =uld be achieved by encouraging a natural understorey (Kunst 1918) . It was suggested that the beneficial effects of an understorey of Leucaena sp . could be attrililted to the effects of the cultivation rather than to the species (Hart 1931b). In north-east Zambia the lack of a deep litter layer under tYienty year old P.kesiya (18 m. tall; 23 an dbh; soil pH 6.2) was associated with an open canopy and a good ground =ver including Desrrodium ascendens var . rotastum and Sphenostylis marginata and the presence of earthwonns (Lawton 1991).

48

In Trinidad the practice arose of close planting teak and in consequencethere was an increased incidence of fire because the deciduous teak leavesaccumulated on the forest floor without decamposing. As a result fire-tenderspecies were eliminated which in turn resulted in the almost complete loss oforganic matter in the topsoil and serious erosion. Previously the teakplantations had been established at a wider spacing and with an admixture ofother species. In those plantations the teak leaves decomposed much fasterand the forest floor, being much less prone to fire, provided conditionssuitable for natural regeneration of local trees and shrubs. There was moreground cover, better soil conditions and less erosion (Bell 1973).

The use of N2-fixing trees, particularly acacias, is often advocatede.g. Acacia auricarifomiswhich may be cpppiced under Eucalyptus exserta inChina (Barnes 1991, Kaeokamnerd 1991) or the mixtures of poplars withHippophae rhamnoides or Robinia pseudoacacia (see Chapter 4). Soil conditionsare improved through the growth of the N2-fixing species and the utility ofthe plantations to people is improved through a wider range of products, butthere is little evidence fram the tropics that the main crop is significantlyimproved. There are, however, well-documented instances of N2-fixingoperating beneficially on the growth of one of more components of a mixturein Nbrth America.

2. Single layered canopy

Bythis is meant the maintenance of a mixture of twowoodyspecies, bothof which are dominants. This mixture is usually permanent for the durationof the rotation, but there is always an option to convert to a single speciesthereby making the mixture temporary. The reasons for attempting a singlelayered mixture include:

Synergy. Two species growing together may give a higher yield than themean of those two in separate pure plantations. The mixed specieseffect has been noted in Scandinavia with pine and spruce (Jonsson1961) and in the beech/oak forests of Belgium, Germany and France. InQueensland it has been the practice to plant Pinus elliottii withAraucaria cunninghamii; there has been a positive response in theA.cunninghamii growth, but the sites have been outside the normal rangeof that species and the practice has been discontinued (Applegate1991). A mixture of Banbax nalabaricum and Acacia catechu has beennoted to have better growth than either species alone in India (IndianForest Service 1939).

The Eucalyptus/Albizia mixture in Hawaii (DeBell et al. 1985) is atropical example of apparent synergy associated with N2-fixing; somewhatunusually in this case the N2-fixing species is in fact larger and fastergraaing than the "main species". This example is discussed more fully laterin this chapter.

Reduction in attacks by pests and diseases. This is covered in detailin Chapter 3. Permanent mixtures only appear to act effectively as abarrier to diseases and pests when the valuable trees to be protectedare highly dispersed as in the case of Milicia (=Chlorophora) excelsaliable to attaCk by Phytalyna lata (Gibson and Jones 1977). There areinstances where mixtures may actually increase the likelihood ofattacks, e.g. the introduction of an alternate host species, and

48

In Trinidad the practice arose of close planting teak and in consequence there was an increased incidence of fire because the deciduous teak leaves accumulated on the forest floor without deCXlllfXJSing . As a result fire- tender species were eliminated which in turn resulted in the alIrost CCIlq:>lete loss of organic matter in the topsoil and serious erosion. Previously the teak plantations had been established at a wider spacing and with an admixture of other species. In those plantations the teak leaves deCCllq:>OSed llUlch faster and the forest floor, being llUlch less prone to fire, provided conditions suitable for natural regeneration of local trees and shruJ:s. There was IIOre ground cover, better soil conditions and less erosion (Bell 1973).

The use of Nz-fixing trees, particularly acacias, is often advocated e. g. Acacia auriCLUifonnis which may be coppiced under Eucalyptus exserta in China (Eames 1991, Kaeok.amnerd 1991) or the mixtures of poplars with Hippophae rhamnoides or Robinia pseudoacacia (see Chapter 4). Soil conditions are iIlproved through the grONth of the N

2-fixing species and the utility of

the plantations to people is iIlproved through a wider range of products, but there is little evidence fran the tropics that the main crop is significantly iIlproved. There are, haoJever, well-documented instances of N

2-fixing

operating beneficially on the grONth of one of IIOre canponents of a mixture in North Alrerica.

2. Single layered canopy

By this is meant the maintenance of a mixture of two woody speCies, both of which are daninants . This mixture is usually permanent for the duration of the rotation, but there is always an option to convert to a single species thereby making the mixture tarporary. The reasons for atterrpting a single layered mixture include:

Synergy. Two species growing together may give a higher yield than the mean of those two in separate pure plantations. The mixed species effect has been noted in Scandinavia with pine and spruce (Jonsson 1961) and in the beech/oak forests of Belgium, Germany and France. In QJeensland it has been the practice to plant Pinus elliottii with Araucaria =ni.nghamiij there has been a positive response in the A. =ni.nghamii grONth, but the sites have been outside the nODll3.1 range of that species and the practice has been discontinued (Applegate 1991). A mixture of Banbax malabaricum and Acacia catechu has been noted to have better grONth than either species alone in India (Indian Forest Service 1939).

The Eucalyptus/Albizia mixture in Hawaii (DeBell et al. 1985) is a tropical exarrple of apparent synergy associated with N

2-fixingj scmewhat

unusually in this case the N2-fixing species is in fact larger and faster

growing than the ''main species" . This exarrple is discussed IIOre fully later in this chapter.

Reduction in attacks by pests and diseases. This is covered in detail in Chapter 3 . Permanent mixtures only appear to act effectively as a barrier to diseases and pests when the valuable trees to be protected are highly dispersed as in the case of Milicia (=Chlorcphora) excelsa liable to attack by Phytolyma lata (Gfrson and Jones 1977). There are instances where mixtures may actually increase the likelihood of attacks, e.g. the introduction of an alternate host species, and

49

therefore mixtures cannot be assumed to provide added protection on allsites or for all species .

Wind. It is possible that in temperate zones the mixture of e.g. beechwith larch may incrPase resistance to windthrow, but there is littleevidence from the tropics. In South Africa it was hoped that theintroduction of the supposedly deeper rooting Pinus radiata into standsof Acacia mEdanoxylon, which is liable to windthrow, would improvestability. This was not a success (de Zwaan 1981).

Economic insurance. This is discussed further in Chapter 7. If it isuncertain which species will perfora best on a site, or if there is arisk of an unpredictable event - late frost, wind, drought - then itmaybe justifiable to plant two or more species (Indian Forest Service1939, HeYbroek and van Tol 1985). In this case the mixture is oftentemporary because it will be found that a monospecific stand hasdeveloped by the end of the rotation and the mixture may well beredundant for the second rotation, because information will have beengained on the site requirements for each species in the mixture(Heybroek and van Tol 1985). The mixture should be carefully matchedto the site and a knowledge of the local ecosystem successional speciesis useful.

Silvicultura], criteria for successful mixtures.

In temporary mixtures the species should be compatible to the extentthat the secondary species is not too demanding; for example it shouldnot have too vigorous a crown, so that the two species can coexist forseveral years without intervention.

In permanent single layer canopy mixtures there is a narrow range ofsites, silvicultural characteristics and management options withinwhich successful growth of mixtures is likely.

The site must be suited to both species (Jonsson 1961; FAO 1991b). Theoverlap of the site requirements of two species is often narro. The rangeof sites on which two species can be grown together can be extended bysilvicultural intervention, but that usually implies a reduction in economicprofitability. This observation is merely an extension of the fact, alreadyemphasised, that matching species to site is one of the first requirements ofgood forestry practice, whether the plantations are pure or mixed.

Silvicultural characteristics must be canpatible; essentially this meansthat the two species should represent approximately the same stage in thesecondary succession and should have similar crown Characteristics. Inaddition the initial height growth should be comparable. Thus the mixture ofslow growing Khaya spp or Ehtandrqphragma spp with Tbiminalia spp orTriplochitcn scleroxylon is unlikely to be successful, while mixtures ofTbrminalia super-La, T.ivorensis and Triplcchition scleroxylan do have a chanceof success (FAO 1991b).

The threshold at which competition starts and hence the density atplanting, the maximum basal area and-the timingand intensity of thinning alsoneed to be similar.

49

therefore mixtures cannot be assumed to provide added protection on all sites or for all species.

Wind . It is possible that in taTperate zones the mixture of e.g. beech with larch llI3.y increase resistance to windthrCM, rut there is little evidence fran the tropics. In South Africa it was hoped that the introduction of the supposedly deeper rooting Pinus radiata into stands of Acacia melanoxyloo, which is liable to windthrCM, would :iJrprove stability. This was not a success (de zwaan 1981).

Econanic insurance. This is discussed further in Chapter 7. If it is uncertain which species will perfODll best on a site, or if there is a risk of an unpredictable event - late frost, Wind, drought - then it llI3.y be justifiable to plant tYIO or IOClre species (Indian Forest Service 1939, Heybroek and van Tol 1985). In this case the mixture is often tarporary because it will be found that a lOClnospecific stand has developed by the end of the rotation and the mixture llI3.y _11 be redundant for the se<Xllld rotation, because inforlll3.tion will have been gained on the siterequiremants for each species in the mixture (Heybroek and van Tol 1985) . The mixture should be carefully llI3.tched to the site and a knowledge of the local ecosystem successional species is useful .

Silvialltural criteria for suocessful mixtures.

In temporary mixtures the species should be carq:atible to the extent that the secondary species is not too dananding; for exarrtJle it should not have too vigorous a crCMn, so that the tYIO species can coexist for several years without intervention.

In perlll3.nent single layer canopy mixtures there is a narrCM range of Sites, silvicultural characteristics and llI3.nagarent options within which successful grCMth of mixtures is likely .

The site ImlSt be suited to both species (Jonsson 1961; FM 1991b). The overlap of the site requiremants of tYIO species is often narrCM. The range of sites on which tYIO species can be grCMn together can be extended by silvicultural intervention, rut that usually :iJrplies a reduction in econanic profitability. This oooervation is IlErelyan extension of the fact, already emphasised, that llI3.tching species to site is one of the first requiremants of good forestry practice, whether the plantatiOns are pure or mixed.

Silvicultural characteristics must be carq:atible; essentially this I!EanS

that the tYIO species should represent approximately the SallE stage in the secondary succession and should have similar CrCMn characteristics. In addition the initial height grCMth should be carq:arable . Thus the mixture of SlCM growing Khaya spp or Entandrophragma spp with Tenninalia spp or Triplochitoo scleroxylon is unlikely to be successful, while mixtures of Tenninalia superba, T.ivorensis and Triplochitoo scleroxyloo do have a chance of success (FM 1991b).

The threshold at which c::x:rrp=tition starts and hence the density at planting, the maxilmlm basal area and the timing and intensity of thinning also need to be similar.

50

In the tropics it is advantageous if the rotation ages are similar (FM)1991b); this is because dominant trees in the tropics usually carry broadcrowns and thinning operations can cause considerable damage to residualtrees. In Scandinavia where crowns are relatively narrow, the removal ofbirch from pine and spruce at about 60% rotation age is recommended(Mielikainen 1985; Tham 1988).

Recently much thought has been given in Germany and other centralEuropean countries to putting plantation forestry onto a sound ecologicalbasis. The criticism is made of many monospecific plantations that there istoo great a risk attached to-the attempts at narrow optimization of objectives(Brunig 1983), though the advantages of selection forests and "natural"management are probably overestimated (Kenk 1990). Mixed planting wouldachieve a broadening of objectives, bit whether the advocated use of yieldmodels instead of the more rigid yield tables is practicable in tropicalpolyspecific stands remains to be tested. The recommended policy ofmaintaining very open stands to encourage indigenous undergrowth achievessimilar effects as the policy of heavy thinning, in order to put maximumgrowth on the most valuable stems, advocated on econamic grounds in SouthAfrica nearly forty years ago (Craib 1947). Examples of overstockedplantations of pine, cypress and teak are common in same tropical countriesand the adverse effects on the sites are apparent; such effects are due to themanagement rather than to the single species composition.

tiethods of establishing mixtures.

Mixtures can be established as intimate mixtures (that is, the speciesare mixed within the lines), by line planting (in which case each line isplanted to only one species), which may be a coMbination of any number oflines of each species, or by groups. The ooMbinations of mixtures within andbetween lines are described in same detail in the fourth Dehra Dunsilvicultural conference (Indian Forest Service 1934). Ageneral conclusionwas that mixtures are extremely difficult to manage unless one component isclearly dominant and the other is a shade bearer that can survive in a semi-suppressed state; in other words a two layered mixture is easier to managethan a one layered mixture. Administratively line planting is the easiest toestablish, but it is also the most difficult to manage technically,particularly if the species are not campatible. An example of a line mixturethat did not succeed is the Cupressus spp. /Grevillea robusta mixtures in Kenya(Graham 1949); the trees were not compatible and as a result the cypressneighbouring the G. robusta lines developed severe butt sep. Intimatemixtures are the most satisfactory if the mixture has been planted as an"insurance", since the crowns of successful trees can expand into the spaceleft by failures with the minimum edge effect. The natural occurrence of amixture, however, is often as a mosaic of small groups in response to minorsite differences.

In Zaire plantations have been established using groups of up to 37plants at close (.5m) spacing within the groups and 10 m spacing betven thegroups in a matrix of natural bush. The species used included a range ofexotics such as eucalypts and pines, Grevillea robusta and Acacia decurrens;in one variant of the technique the species CUpressus lusitanica, Eucalyptusgrandis and Acacia decurrens were mixed within each group. The species didnot appear to have been selected with compatibility inmind. At 30 months thegrowth, as indicated byphotographs, appeared good within the groups but thereappeared to be no matrix and edge effects must have been large. The

50

In the tropics it is advantageous if the rotation ages are similar (F7IO 1991b); this is because daninant trees in the tropics usually carry broad crowns and thinning operations can cause considerable damage to residual trees. In Scandinavia where crowns are relatively !la.l:rCM, the raroval of birch fran pine and spruce at about 60% rotation age is rea:::mtended (Mielikainen 1985; Tham 1988).

Recently IlUlch thought has been given in GeIIl\aIly and other central European countries to putting plantation forestry onto a sound ecological basis. The criticism is made of many llOIlospecific plantations that there is too great a risk attached to the attE!rpts at narrCM optimization of objectives (Brunig 1983), though the advantages of selection forests and "natural" managaoont are probably overestimated (Kenk 1990) . Mixed planting would achieve a broadening of objectives, rut whether the advocated use of yield rrodels . instead of the m:lre rigid yield tables is practicable in tropical pol yspecific stands ranains to be tested. The rea:::mtended policy of maintaining very open stands to encourage indigenous undergrCMth achieves similar effects as the policy of heavy thinning, in order to put rnaxinrum grCMth on the m:lSt valuable stans, advocated on econanic grounds in South Africa nearly forty years ago (Craib 1947). Exarrples of overstocked plantations of pine, cypress and teak are CCIlIOCl!l in sare tropical countries and the adverse effects on the sites are apparent; such effects are due to the managaoont rather than to the single species c:crnposition.

Methods of establishing mixtures.

Mixtures can be established as intimate mixtures (that is, the species are mixed within the lines), by line planting (in which case each line is planted to only one species), which may be a canbination of any number of lines of each speCies, or by groups. The canbinations of mixtures within and berneen lines are described in sare detail in the fourth Debra Dun silvicultural conference (Indian Forest Service 1934). A general conclusion was that mixtures are extremely difficult to manage lIDless one CCIlIpOl1ent is clearly daninant and the other is a shade bearer that can s1,lIVive in a seni­suppressed state; in other words a two layered mixture is easier to manage than a one layered mixture. Administratively line planting is the easiest to establish, rut it is also the m:lSt difficult to manage technically, particularly if the species are not cx::Ilp3.tible. An exarrq::>le of a line mixture that did not succeed is the CUpressus spp./ Grevillea rorusta mixtures in Kenya (Graham 1949); the trees were not cx::Ilp3.tible and as a result the cypress neighbouring the G. rorusta lines developed severe rutt sweep. Intimate mixtures are the m:lSt satisfactory if the mixture has been planted as an "insurance", since the crowns of successful trees can expand into the space left by failures with the minimllm edge effect. The natural oc=ence of a mixture, ~ver, is often as a m:lSaic of small groups in response to minor site differences. .

In Zaire plantations have been established using groups of up to 37 plants at close (.5 m) spacing within the groups and 10 m spacing berneen the groups in a matrix of natural rush. The species used included a range of exotics such as eucalypts and pines, Grevillea rorusta and Acacia decurrens; in one variant of the technique the species CUpressus lusitanica, Eucalyptus grandis and Acacia decurrens were mixed within each group. The species did not appear to have been selected with cx::Ilp3.tibility in mind. At 30 llOIlths the grCMth, as indicated by photographs, appeared good within the groups rut there appeared to be no matrix and edge effects ImlSt have been large. The

51

technique, based on Anderson's groups (Anderson 1953) was also proposed forKivu and Ruanda (Pierlot 1955); no further reports have been noted.

Abroad sense mixture (Chapter 1) was defined as being different speciesor provenances in neighbouring blocks. Mixtures of clones may be also definedin the broad sense of neighbouring blodks. An example of this form of mixinghas been used in Aracruz, Brazil where clones of eucalyptus have beendeveloped for each site type in the estate and there is a policy to ensurethat out of a total of same 100 available clones a selection of 10 to 15clones are used on each site in blocks of 5 to 30 ha (Burley and Ikemori1988).

Management skILLs

MixEkipaantations require more intensive management than single speciesplantations so that while the basic skills maybe the same for either type themanagement of the former requires greater attention to detail and has lessroom for error than the latter. The skills required maybe summarised underthree headings.

Clear abjectives.

There must be a clear statement of objective for the mixture; whetherit is soil improvement, increased yield by synergy, the reduction of adverseeffects on wildlife etc. Only when the objectives are clearly defined can thefield staff he expected to establish and maintain the mixture. Ideally,objectives should be held constant for a rotation but in fact one of theadvantages of a mixture may be that if markets change then there is theflexibility to change objectives to meet the new demands.

Experience.

The point has been made that management of mixed plantations is adelicate operation (Dupuy 1986) . Prescriptions can be established for guidingfield foresters, butmanagement decisions have to take account of small sitedifferences and must be made in the field. The knowledge of what is the besttreatment on anyone site can onlybe obtained by experience and specificallyexperience of that site. The fact that same of the Sapoba mixed taungyaplantations in Nigeria have eventually produced worthwhile mahogany treesdespite discontinuous and inadequate management (LaMb 1991; Lowe 1991), doesnot invalidate the need for skilled management forinixed plantations to beeconomically successful.

Continuity of management.

In same parts of central Europe it is not unknown for a forest to bemanaged over many decadPs successively by three generations of one family.In this way experience is built up and passed on. By contrast in samecountries it is civil service policy to transfer staff, even down to quitejunior ranks every three years. In that way detailed experience of thesilvicultural requirements of a forest can neither be obtained nor retained.Goal management plans, records and the discipline to enforce theirprescriptions can go same way to off-setting the effect of staff transfers.But though very long postings are usually impractical, without continuity ofmanagement and guaranteed finances the chances for successful managementespecially of mixed plantations are small.

51

technique, based on Anderson's groups (Anderson 1953) was also proposed for Kivu and Ruanda (Pier1ot 1955); no further reports have been noted.

A broad sense mixture (Chapter 1) was defined as being different species or provenances in neighlxJuring blocks. Mixtures of clones may be also defined in the broad sense of neighbouring blocks. An exarrple of this fom of mixing has been used in Aracruz, Brazil where clones of eucalyptus have been developed for each site type in the estate and there is a policy to ensure that out of a total of same 100 available clones a selection of 10 to 15 clones are used on each site in blocks of 5 to 30 ha (Burley and IkEm::>ri 1988) .

Manat;Eiie .. L skills.

Mixed plantations require rrore intensive management than single species plantations so that while the basic skills may be the same for either type the management of the fomer requires greater attention to detail and has less roan for e=r than the latter. The skills required may be surrmarised under three headings.

Clear objectives .

There l!Il.lSt be a clear statement of objective for the mixture; whether it is soil illq:>rovement, increased yield by synergy, the reduction of adverse effects on wildlife etc . Only when the objectives are clearly defined can the field staff be expected to establish and maintain the mixture. Ideally, objectives should be held constant for a rotation rut in fact one of the advantages of a mixture may be that if markets change then there is the flexibility to change objectives to rreet the new danands .

Experience.

The point has been made that management of mixed plantations is a delicate operation (Dupuy 1986). Prescriptions can be established for guiding field foresters, rut management decisions have to take account of small site differences and l!Il.lSt be made in the field . The knowledge of what is the best treatment on anyone site can only be obtained by experience and specifically experience of that site. The fact that same of the Sapoba mixed taungya plantations in Nigeria have eventually produced worthwhile mahogany trees despite discontinuous and inadequate management (Lamb 1991; r.a.e 1991), does not invalidate the need for skilled management for mixed plantations to be econanically successful.

Continuity of management.

In sare parts of central Europe it is not unknCMll for a forest to be managed over many decades successively by three generations of one family . In this way experience is ruilt up and passed on. By contrast in sare countries it is civil service policy to transfer staff, even dCMll to quite junior ranks every three years . In that way detailed experience of the silvicultural requirarents of a forest can neither be obtained nor retained. Good management plans, records and the discipline to enforce their prescriptions can go same way to off-setting the effect of staff transfers. But though very long postings are usually illq:>ractical, without continuity of management and guaranteed finances the chances for successful management especially of mixed plantations are small.

52

The consequence of lack of management is likely to be a tendency for onespecies to gain dominance and to four' monospecific stands or groups .

Same experiences with mixtures.

Sane examples illustrate relevant points.

The re-creation of natural forest conditions.

Tropical rainforests, if destroyed by man over an area larger than asmall plot, will require several hundred years to readh a climax naturally(Adlard 1978) . In Ma.laysia the dipterocarp demonstration plots at the ForestResearch Institute, Kepong were established artificially in the nineteenthirties by planting under Albizia falcafria nurse crops. The plots wereestablished on reclaimed tin mines or onto abandoned vegetable plots. Thisnurse crop was removed fairly soon, but over the years local species haveregenerated under the dipterocarps. Now, sixty years later, some of theseplots are believed to be a goal approximation to the secondary succession ofthe natural forest that once grew on the site (Ng 1991).

In some areas of Brazil attempts havebeen made to re-create the naturalforest. A wide range of species, mostly indigenous but including sameexotics, has been planted on a few sites. These plantings have been studiedto determine the species' ecological requirements and successional position(Nogueira 1977; Kageyama et al. 1990). In Sao Paulo an experimental plantingof an area deforested for 50 years was, after 22 years, considered to be avigorous semi-deciduous forest with trees up to 20m tall. At Candida Mote,however, a study of natural regeneration in a 15 year old riverbank plantingshaged that though 42 species had regenerated, 64% were Nectandra megapotamicaand there is a strong tendency towards the development of a "homogenous"forest (Durigan and de Souza Dias 1990). Aknowledge of local ec,ology and thespecies of each successional stage is helpful. In Uganda the selection ofnurse trees for Chlorophora excelsa was based on a knowledge of local ecology(Dawkins 1949) and has apparently proved to have been reasonably successful.In Cuba a dRtailed classification of species by their successional stage andsilvicultural requirements has been made for Sie/La del Rosario (Canizares etal 1987).

There is no indication that the Brazilian plantings (above) are likelyto produce oommercial timber or that they were ever intended for anything-butprotection planting on riverbanks. But the Kepongdipterocarp plots, thoughthey are in fact ncw being used as a recreational area, are carryingcannercial timber of exploitable size. This one example has shcwn that re-creation of secondaayforest conditions is possible in a reasonable time spanin very small plots.

A Mahogany plantation.

At Sundapola in Sri Lanka a mixture of mahogany (Swieteniamacrophylla),teak (Tectona grandis) and jak (Artocarlaus integrifolius) was established atthe beginning of the twentieth century. The mixture was intended to protectthe mahogany from attacks by Hypsipyla robusta. By the nineteen fifties therewas profuse regeneration of the mahogany although whether this arose becauseof protection from borer attack or because mahog-any is a shade tolerant andfast growing tree is not clear. A decision was made to manage the area as aselection forest favouring the more valuable mahogany (Tisseverasinghe and

52

The consequence of lack of management is likely to be a tendency for one species to gain daninance and to fODn m:mospecific stands or groups.

Salle experiences with mixtures.

Sate examples illustrate relevant points .

(a) The re-creation of natural forest conditions.

Tropical rainforests, if destroyed by man over an area larger than a small plot, will require several hundred years to reach a climax naturally (Adlard 1978) . In Malaysia the dipterocaIp dem:mstration plots at the Forest Research Institute, Kepong were established artificially in the nineteen thirties by planting under Albizia falcataria nurse crops. The plots were established on reclaiIred tin mines or onto abandoned vegetable plots . This nurse crop was renoved fairly soon, rut over the years local species have regenerated under the dipterocarps. Now, sixty years later, Sate of these plots are believed to be a good approximation to the secondary succession of the natural forest that once grew on the site (Ng 1991) .

In Sate areas of Brazil atterpts have been made to re-create the natural forest . A wide range of species , mostly indigenous rut including Sate exotics, has been planted on a few sites. These plantings have been studied to detennine the species' ecological requirements and successional position (Nogueira 1977; Kageyama et al. 1990) . In Sao Paulo an experiIrental planting of an area deforested for 50 years was, after 22 years, considered to be a vigorous sani-deciduous forest with trees up to 20 m tall. At Candida MJte, ~ver, a study of natural regeneration in a 15 year old river bank planting slJa.led that though 42 species had regenerated, 64% were Nectandra megapotamica and there is a strong tendency towards the developnent of a "harogenous" forest (D.n:igan and de Souza Dias 1990) . A knowledge of local ecology and the species of each successional stage is helpful . In Uganda the selection of nurse trees for Chlorop!Jora excelsa was based on a knowledge of local ecology (Dawkins 1949) and has apparently proved to have been rea.s<Jnably successful . In CUba a detailed classification of species by their successional stage and silvicultural requirements has been made for Sierra del Rosario (Canizares et a1 1987) .

There is no indication that the Brazilian plantings (above) are likely to produce cc:mrercial timber or that they were ever intended for anything rut protection planting on river banks. But the Kepong dipterocaIp plots, though they are in fact now being used as a recreational area, . are carrying cc:mrercial timber of exploitable size . This one example has shown that re­creation of secondary forest conditions is possible in a reasonable t:ilre span in very small plots.

(b) A Mahogany plantation.

At Sundapola in Sri Lanka a mixture of mahogany (SWietenia macrophylla) , teak (Tectona grandis) and jak (Artocarpus integrifolius) was established at the beginning of the twentieth century. The mixture was intended to protect the mahogany fran attacks by Hypsipyla robusta . By the nineteen fifties there was profuse regeneration of the mahogany although whether this arose because of protection fran borer attack or because mahogany is a shade tolerant and fast growing tree is not clear. A decision was made to manage the area as a selection forest favouring the IlOre valuable mahogany (Tisseverasinghe and

53

Satdhithananthima 1957) . This has been done successfully for scale thirty yearsnow and the teak and jak had been reduced to about 20% of the crop by 1963(MUttiah 1965). Felling is undertaken with great care and because of thevalue of the mahogany it is possible to insist on the contractors deliMbingthe trees before felling.

This is a rather unusual example of anurse crop achieving its objectiveand then being retained as an equal partner in the upper canopy of the cropalthough much reduced from its original stocking. It also illustrates thatthere is the option to change the crop to be monospecific, though thecircumstances at Sundapola are unusual in that selection felling techniquesare being applied in essentially monospecific plantations in the tropics.

(c) West Africa

Expertise has been obtained in handling mixtures involving Terminaliaspp., Khaya spp., heritiera utilis, Triplochiton scleroxylon, Naucleadiderrichii, Lowe trichilioides and Aucoumeaklaineana among the indigenousspecies and teak, Cedrela odorata, GMelina artorea and pines as exotics (FAD1991b)

In the dense evergreen forests the establishment of heritiera utilis,Aucomea Alaineana, Bauclea diderrichii (long rotation - greater than 35years) and Terminalia ivorensis, T. super-La, GMelina arborea and pines (shortrotation, 20 to 25 years) can be achieved in pure stands. Mixtures are neededfor raising Rhaya ivorensis, K. senegalensis and K. anthotheca with Heritierautilis and Nauclea dirirrichii; in which case there is the option to convertto the secondary species if the Maya proves unsatisfactory.

In the transition zone from dense evergreen to dense semi-deciduousforests Terminalia ivona2sisand T. superta can be established as mixtures oreither of these two species can be mixed with Triplochiton scleroxylon; theproportion of the components can be controlled by early or late thinning. Inthe dense semi-deciduous forest zone these species and also GMelina artoreacan be raised with teak as a secondary species. But all these speciestogether with Cedrela odorata can also be raised as pure crops.

In the tree savannas teak ,and G.arborea can be raised either pure or inmixture.

It is of interest that teak is considered to be a secondary, shadetolerant species, wherPas elsewhere it is usually considered as a dominant,light demanding species. Of the ave species the light demanders areTerminalia spp., Triplochi ton scleroxylon, Aucoumea Alaineana, GMelineartorea, Cediela odorata and the pines, while heritiera utilis, Khaya spp.,Nauclea diderrichii and teak are considered to be relatively shade tolerant.

According to experience, the mixtures to be avoided because ofincompatible growth rates (Dupuy 1985) are:

Tieghemella spp with heritiera utilisCedrela odorata with _altandroptiragma utile or Terminalia ivorensisTerminalia ivorensis with Khaya spp or .a2tandrophragma utileTriplochiton scleroxylon with Rhaya spp or Tieghemella spp.

53

Satchithananthan 1957). This has been done successfully for sane thirty years now and the teak and jak had been reduced to about 20% of the crop by 1963 (M..!ttiah 1965). Felling is undertaken with great care and because of the value of the mahogany it is possible to insist on the contractors deliInbing the trees before felling.

This is a rather tmusual exarrple of a nurse crop achieving its objective and then being retained as an equal partner in the upper canopy of the crop although I!D.lch reduced fran its original stocking. It also illustrates that there is the option to change the crop to be m:mospecific, though the circumstances at Stmdapola are tmusual in that selection felling techniques are being applied in essentially m:mospecific plantations in the tropics.

(c) West Africa

Expertise has been obtained in handling mixtures involving Tezminalia spp., Khaya spp., Heritiera utilis, Triplochiton scleroxylon, Nauclea diderrichii, LoV03 trichilioides and Auooumea klaineana aIOOI1g the indigenous species and teak, Cedrela cdorata, Gnelina arborea and pines as exotics (Fro 1991b)

In the dense evergreen forests the establishment of Beritiera utilis, Auooumea klaineana, Nauclea diderrichii (long rotation - greater than 35 years) and Tezminalia ivorensis, T . superba, Gnelina arborea and pines (short rotation, 20 to 25 years) can be achieved in pure stands. Mixtures are needed for raising Khaya ivorensis, K. senegalensis and K. anthotheca with Heritiera utilis and Nauclea diderrichii; in which case there is the option to convert to the secondary species if the Khaya proves tmSatisfactory.

In the transition zone fran dense evergreen to dense semi --deciduous forests Tezminalia ivorensis and T. superba can be established as mixtures or either of these two species can be mixed with Triplochiton scleroxylon; the proportion of the carg;x:ments can be controlled by early or late thinning. In the dense semi -deciduous forest zone these species and also Gnelina arborea can be raised with teak as a secondary species. But all these species together with Cedrela cdorata can also be raised as pure crops.

In the tree savannas teak and G.arborea can be raised either pure or in mixture.

It is of interest that teak is considered to be a secondary, shade tolerant speCies, whereas elsewhere it is usually considered as a daninant, light dananding species. Of the above species the light demanders are Tezminalia spp., Triplochiton scleroxylon, Auooumea klaineana, Gnelina arborea, Cedrela cdorata and the pines, while Beritiera utilis, Khaya spp., Nauclea diderrichii and teak are considered to be relatively shade tolerant.

According to experience, the mixtures to be avoided because of in~tible growth rates (Dupuy 1985) are:

Tieghemella spp with Beritiera utilis Cedrela cdorata with Entandrophragma utile or Tezminalia ivorensis Tezminalia ivorensis with Khaya spp or Entandrophragma utile Triplochiton scleroxylon with Khaya spp or Tieghemella spp.

54

In Mamu River Forest Reserve in Nigeria mahoganies (Khaya spp,Ehtandrqphragma spp and Lovoa trichilioidés) were ised in a matrix ofGffielina artorea, which was felled on a ten year coppice rotation. After twoor three such rotations the mahoganies over-topped the G. artorea and formeda closed canopy, bit it was doubtful if there was a positive economic return(Lowe 1991).

The essential lessons to be learned fran the West African experience isthat successful mixtures for wood production depend on the careful matchingof species to site and a knowledge of which species are ecologically andsilviculturally compatible.

(d) Eucalyptus clonal plantations.

At Aracruz in Brazil a pulp mili has been built which is served by82,000 ha of eucalypt plantations. They are managed on a seven to eight yearrotation and as a result of an intensive breeding programme are highlyproductive and eadh of the varieties used is very uniform. This has beenachieved by developing clones with the required characteristics for vigour,straightness, branching, coppicing ability, disease resistance, wood densityetc (Burley and Ikemori 1988; Aracruz Cellulose 1988; Campinhos and Ikemori1986). Forestry plantations here approach about as close as they-can to shortterm agricultural crops and are, one might think, about as far removed framthe concept of mixed plantations as is possible, although it should be notedthat there are different species and hybrids. Though there is always thetemptation to concentrate effort on the very highest yielding clones, adecision was made to have a pool of about one hundred clones and furthermoreto ensure that a selection from 15 to 20 clones should be used on each sitetype. The decision then had to be made whether to mix clones in onecompartment or whether to achieve a mixture in the broad sense by juxtaposingcompartments of different clones. The latter course was taken partly becauseunless the clones were equally competitive one would be suppressed with acertain loss in uniformityand a probable loss in yield, but also because anintirnate mixture was considered to give no advantage in combatting pests anddisposes and quite possibly might make attacks more likely. It has beenspeculated that a mixture of a few clones carries a higher risk of losses frampests and diseases than does either a mixture of many clones or a single clone(Libby 1982). With a monoclonal plantation unsatisfactory carpartments couldhe harvested early-and replaced with the minimum disruption to routine, whilea mixed compartment of which one component was unsatisfactory would bedifficult to treat.

In addition there is a policy at Aracruz of retaining 20% of the area,mostly along rivers, under indigenous forest and these have been enriched withfruit and other trees. The Objective here is both soil protection and theencouragement of insectiVorous birds whichmayhelp control insect attacks onthe eucalyptus as well as conserving biological diversity.

Thus even in this very high yielding operation in which speciesdiversity has been deliberately reduced, a policy decision has been made toforgo same short term gains in order to have a mixture of clones available andthereby to include an element of diversity. In the eucalypt plantations atPointe Noire, Congo, the pool of clones is smaller and over half the area hasbeen established with only 5 clones (Martin et al. 1989). The genetic basehas recently been widened through the development of a concurrent programmeof controlled crossing (Martin 1991). There has also been diversification

54

In MarrUl River Forest Reserve in Nigeria mahoganies (Khaya spp, Entandrophragma spp and Lovoa trichilioides) were raised in a matrix of GT/eliIJa aroo.rea, which was felled on a ten year coppice rotation . After two or three such rotations the mahoganies over-topped the G. aroo.rea and fomed a closed canopy, rut it was doubtful if there was a positive econanic return (Ia-Ie 1991).

The essential lessons to be learned fran the West African experience is that successful mixtures for wood production depend on the careful matching of species to site and a knowledge of which species are ecologically and silviculturally compatible.

(d) Eucalyptus clonal plantations .

. At Aracruz in Brazil a pulp mill has been ruilt which is served by 82,000 ha of eucalypt plantations . They are managed on a seven to eight year rotation and as a result of an intensive breeding prograrrme are highly productive and each of the varieties used is very uniform. This has been achieved by developing clones with the required characteristics for vigour, straightness, branching, coppicing ability, disease resistance, wood density etc (Burley and Ikarori 1988; Aracruz Cellulose 1988; Campinhos and Ikarori 1986). Forestry plantations here approach about as close as they can to short term agricultural crops and are, one might think, about as far raroved fran the concept of mixed plantations as is possible, although it should be noted that there are different species and hybrids . Though there is always the tarptation to concentrate effort on the very highest yielding clones, a decision was made to have a pool of about one hundred clones and furthermore to ensure that a selection fran 15 to 20 clones should be used on each site type . The decision then had to be made whether to mix clones in one campartmant or whether to achieve a mixture in the broad sense by juxtaposing campartmants of different clones. The latter course was taken partly because unless the clones were equally carnpetitive one would be suppressed with a certain loss in uniformity and a probable loss in yield, rut also because an intimate mixture was considered to give no advantage in canbatting pests and diseases and quite possibly might make attacks IWre likely. It has been speculated that a mixture of a few clones carries a higher risk of losses fran pests and diseases than does either a mixture of many clones or a single clone (Libby 1982) . With a IWnoclonal plantation unsatisfactory canpartm:mts could be harvested early and replaced with the miniIrrum disruption to routine, while a mixed canpartm:mt of which one canponent was unsatisfactory would be difficult to treat.

In addition there is a policy at Aracruz of retaining 20% of the area, IWStlyalong rivers, under indigenous forest and these have been enriched with fruit and other trees. The objective here is both soil protection and the encouragement of insectiVorous birds which may help control insect attacks on the eucalyptus as well as conserving biological diversity .

Thus even in this very high yielding operation in which species diversity has been deliberately reduced, a policy decision has been made to forgo sane short term gains in order to have a mixture of clones available and thereby to include an element of diversity. In the eucalypt plantations at Pointe NOire, Congo, the pool of clones is smaller and over half the area has been established with only 5 clones (Martin et al . 1989) . The genetic base has recently been widened through the developrent of a con=ent prograrrme of controlled crossing (Martin 1991). There has also been diversification

55

into sawn timber production (Cossalter 1991). The means by which the risksinvolved in the use of clonal material maybe reduced have been summarised byMatziris (1991) as the use of a large number of clones in mixture or mosaic,the rotation of clones over time and the regular introduction of new clonescoMbined with sexual reproduction for the production of new clonal materialand as a badk up.

Conclusions on the management of mixtures.

Successful mixtures of two or more species on one site, to meet any oneor more Objectives, depend on management having clearly defined aims forestablishing mixed plantations and then on selecting species that arecompatible. A knowledge of the position of the species in the successionalhierarChy in the ecosystem is helpful, but information is also needed on thesilvicultural requirements of each species.

Mixtures involving the growth of one species under another, for examplenurse crops or ground oover, are generally relatively easy to manage, thoughskill is still needed in removing an overstorey if the shade tolerant speciesis to form the final crop.

The management of mixtures of two daninants is much more difficult; theycan usually only be managed on a narro range of sites and often result in thesuppression of one of the species and hence a reversion to an essentiallymonospecific stand. Although examples have been quoted where two or morespecies have been grown together on the sama site, in general it is believedthat the laCk of trained and experienced staff in many tropical countries,coMbined with the ladk of continuity of staff and financial guarantees makethe successful management of dominant mixtures unlikely at the present time.

There is sane justification for planting mixtures as an insuranceagainst an unpredictable event, e.g. drought, frost, waterlogging, salinity,but the need to ensure that the species are broadly matched to the site stillremains and there is a general tendency for these mixtures to becomehomogeneous tythe end of the rotation. There is little evidence to indicatethat mixtures are effective in preventing attacks by unspecified pests ordiseases.

A strategy of broad sense mixtures, where a range of suitable speciesare available, and the enforcement of good forestry practice, will very oftenachieve the required stability. Sane of the strategies now being advocatedon ecological grounds in Germany, such as wider spacing in plantations, arevery similar ineffect to sane of those adopted in southernAfrica forty yearsearlier on economic grounds.

55

into sawn timber production (Cossalter 1991). The means by which the risks involved in the use of clonal material may be reduced have been sunmarised by Matziris (1991) as the use of a large mnnber of clones in mixture or m::JSaic, the rotation of clones over time and the regular introduction of new clones canbined with sexual reproduction for the production of new clonal material and as a back up.

('ax:lnsions OIl the lIIim'~JB""i1t of mixtures.

Successful mixtures of two or rrore species on one site, to rreet anyone or rrore objectives, depend on management having clearly defined aims for establishing mixed plantations and then on selecting species that are carpatible. A kncJtdedge of the position of the species in the successional hierarchy in the ecosystem is helpful, rut infonnation is also needed on the silvicultural requirements of each species.

Mixtures involving the g:rcMth of one species under another, for exarrple nurse crops or ground cover, are generally relatively easy to manage, though skill is still needed in .removing an overstorey if the shade tolerant species is to fonn the final crop.

The management of mixtures of two daninants is IlUlch rrore difficult; they can usually only be managed on a = range of sites and often result in the suppression of one of the species and hence a reversion to an essentially rronospecific stand. Although exarrples have been quoted where two or rrore species have been gra.m together on the same site, in general it is believed that the lack of trained and experienced staff in many tropical countries, canbined with the lack of continuity of staff and financial guarantees make the successful management of daninant mixtures unlikely at the present time .

There is sane justification for planting mixtures as an insurance against an unpredictable event, e.g. drought, frost, waterlogging, salinity, rut the need to ensure that the species are broadly matched to the site still ranains and there is a general tendency for these mixtures to becane hanogeneous by the end of the rotation. There is little evidence to indicate that mixtures are effective in preventing attacks by unspecified pests or diseases.

A strategy of broad sense mixtures, where a . range of suitable species are available, and the enforcement of good forestry practice, will very often achieve the required stability. Sane of the strategies nCM being advocated on ecological grounds in Gennany, such as wider spacing in plantations, are very similar in effect to sane of those adopted in southern Africa forty years earlier on econanic grounds.

6. YIELDS.

The measurerrent of yields of wood (as opposed to other benefits) in longrotation tree crops is not easy. Longterm experiments need to be large, aredifficult to control, have a high incidence of mishaps and in consequence ahigh coefficient of residual variation. For these reasons there has been atendency to use mathematical modelling techniques to derive yields, but thesemeasure yield potential under optimal or standardized conditions and theinputs to the models are often fram undisturbed plots. The measurement ofactual yields, however, reflects the real situation and the inputs then arederived fram average plots exposed to average treatment and to the averageoccurrence of calamities. The emphasis in this case will be on large datainput, the relevant grouping of stands and plots and the use of regressionfunctions for describing the processes.

North America and temperate Asia.

Same attention has been given to the effect on yields of wood of anadmixture of nitrogen-fixing species.

Alder (mostly Al.r2us rubra) in North America in mixture with coniferse.g. Douglas fir (Pseudotsugamenziesii) on nitrogen poor sites can result ina large increase in the conifer yields, though the increase may not beapparent until after about age 30 in the case of the conifer (Binkley 1984;Binkley& Greene 1983). The beneficial effects may only be apparent when thenitrogen fixing species is dominant or co-dominant in the stand and onnutrient-poor sites these species are unable to fix N2. On nitrogen richsites overall yields usually remain unaffected or may decrease, while theyield of the conifer component usually decreases (Binklay and Greene 1983).

Admixtures of alder, black locust (Robinia pseudoacacia) and inparticular autumn olive (Elaeagnusumbellata) can have an effect on the grawthof walnut (Juglansnigra) in NorthAmerica; nitrogen mineralization is greatlyincre_ased and there may be a corresponding increase in the yield of the walnutwhich can be as high as 30 fold (Paschke et al. 1989; Schlesinger and Williams1984). But there is also an instance of walnut basal area growth not beingclosely correlated with soil nitrogen concentration, even though nitrogen wasbeing fixed satisfactorily in the topsoil by alder and other nitrogen fixingspecies (Friederich and Dawson 1984).

In mixtures of light demanding species one component tends to besuppressed by the other. Cherrybark oak (Cuercusfalcatavarpagodifolia) willbe suppressed up to the age of 25 years when grown in close association withsweetgum (Liguidanbar styzaciflua) or american sycamore (Platanusoccidentalis). The more valuable cherrybark oak had better form when grownin close association with other species and after 25 years of age was able tocompete with than (Clatterbudk et al. 1987; Clatterbudk and Hodges 1988).

The concept that one species can fill a niche in a stand withoutdetriment to the main species is attractive. It is suggested that this mayoccur in rather special circumstances such as in Finland in spruce/birchmixtures where Betula putescens grows in gaps in badly established spruce(Mielikainen 1985). But an example from North America shows that though thenatural admixture of Thuga canadensis into hardwood stands increased thestanding volume on two sites by 30% & 20%, this in fact involved a 20%

5656

6. YIEUlS.

Themeasurarent of yields of wood (as opposed to other benefits) in long rotation tree crops is not easy . L:lngteIIll experiments need to 1:e large , are difficult to a:mtrol, have a high incidence of mishaps and in consequence a high coefficient of residual variation . For these reasons there has 1:een a tendency to use mathanatical modelling techniques to derive yields , rut these measure yield potential under optimal or standardized conditions and the inputs to the models are often fran undisturl:ed plots . The measurement of actual yields, hcw:ver, reflects the real situation and the inputs then are derived fran average plots exposed to average treatment and to the average occurrence of calamities. The emphasis in this case will 1:e on large data input, the relevant grouping of stands and plots and the use of regression functions for describing the processes .

North America and tEDp"ZClte Asia.

scme attention has 1:een given to the effect on yields of wood of an admixture of nitrogen-fixing species .

Alder (rrostly Alnus zubIa) in North Alrerica in mixture with a:mifers e.g. Douglas fir (Pseudotsuga menziesii) on nitrogen poor sites can result in a large increase in the conifer yields, though the increase may not 1:e apparent until after about age 30 in the case of the conifer (Binkley 1984; Binkley & Greene 1983). The beneficial effects may only 1:e apparent when the nitrogen fixing species is daninant or c:o--Qaninant in the stand and on nutrient-poor sites these species are unable to fix N

2• On nitrogen rich

sites overall yields usually remain unaffected or may decrease, while the yield of the a:mifer carp:l!1ent usually decreases {Binkley and Greene 1983).

lIdmixtures of alder, black locust (Robinia pseudoacacia) and in particular autumn olive (Elaeagnus umbellata) can have an effect on the g:rcMth of walnut (Juglans nigra) in North Alrerica; nitrogen mineralization is greatly increased and there may 1:e a corresponding increase in the yield of the walnut which can 1:e as high as 30 fold (Paschke et al. 1989; Schlesinger and Williams 1984). But there is also an instance of walnut basal area grCMth not l:eing closely correlated with soil nitrogen a:mcentration, even though nitrogen was l:eing fixed satisfactorily in the topsoil by alder and other nitrogen fixing species (Friederich and Dawson 1984) .

In mixtures of light dananding species one carp:l!1ent tends to 1:e suppressed by the other. Cherrybark oak (CUercus falcata var pagcdifolia) will 1:e suppressed up to the age of 25 years when grc:MIl in close association with sweetgum (Liquidamb3r styraciflua) or american sycam:::>re (Platanus occidentalis). The more valuable cherrybark oak had l:etter fOIIll when grc:MIl in close association with other species and after 25 years of age was able to caIlpete with than (Clatterruck et al. 1987 ; Clatterruck and Hodges 1988).

The a:mcept that one species can fill a niche in a stand without detriment to the main species is attractive . It is suggested that this may occur in rather special circumstances such as in Finland in spruce/birch mixtures where Betula pubescens grCM.3 in gaps in bad! Y established spruce (Mielikainen 1985). But an exarrple fran North Alrerica shCM.3 that though the natural admixture of Tsuga canadensis into hardwood stands increased the standing volume on two sites by 30% & 20%, this in fact involved a 20%

57

reduction in the vollzne of the more valuable hardwoods, such as Quercus rubra(Kelty 1989) .

In Japan a mixture of akamatsu (Pinus densiflora) and hinoki(Chamaegyparis obtusa) resulted in a greater overall volume, but a lowervolume of hinoki (Kawahara and Yamamoto 1986).

Europe

The admixture of beech (Iagus sylvatica) with spruce (Picea abies) isclailuxito increase total yields by 15% (Schutz 1989). This is, however, lessan example of an interaction between the species than a reflection of the factthat the spruce grows faster than the beech; pure spruce stands may be evenmore productive.

The interaction of Picea abies and Finus sylvestris has been examinedin some detail in Scandinavia (Jonsson 1961). A positive interaction, knownas the "mixed species effect", has been identified when pine and spruce aremixed on sites where both species can be expected to do well The benefitsof this effect reduce as the site changes to favour one or other of thespecies - drier, less fertile sites favour pine; wetter, more fertile sitesfavourspruce. There is also a corresponding tendencyfor the favoured speciesto become dominant and to form monospecific stands, or at least a mosaic ofmonospecific groups. This tendency has also been noted with other species inBblland (Heybroek and Tol 1985). The mixed species effect varies with theparameter measured; for height it is positive for both species; for diametergrowth, however, it is positive for pine, but of no effect or slightlynegative for spruce (jcnsson 1961). Mbre receatvoprkon pineruce mixtureson Ca11una heaths and peat has indicated a strong positive effect on thegrowth of Piceasitchensis (Aalcolm et a1 1990). Themixed species effect (orsynergy) makes canparison between mixed and pure natural stands on differentsites difficult, if the Site Index is defined by dominant height, since mixedstands will be tend to be compared with pure stands of a higher Site Index.This fact may have disguised the benefits of mixed stands (Jonsson 1961).Site Index has then to be defined by the less precise method of observing soilcharacteristics, vegetation types and indicator species.

The interaction of birch with conifers is more complex. This has beeninvestigated in two studies in Finland and Sweden (Mielikainen 1985; Tham1988) using yield modelling techniques. The general interpretation of theinteractions of birdhes with conifers is similar in the two studies, but theyields and scale of benefits are much higher in Sweden; this maybe an effectof site or only of the assumptions made in the models. a pendtda, a pioneerspecies that initially dominates the main crop may have a beneficial effecton spruce (Picea abies), which is a shade tolerant species, even when thebirch is retained to full rotation. Pine (Pinus sylvestris) is a shadeintolermtspecies andtherefore though birch increases yields in open stands,in close competition birdh depresses height growth of the pine. One solutionis to cut the birch back for the first seven or eight years until the pine hasa 1 m height advantage (Mielikainen 1985), but this would appear to reduce thevalue of the birch as a nurse crop. Birch should never be allowed to remainto full rotation in pine stands, because the total yield will be depressed.B. pubesoens may have a depressing effect on conifers (Mielikainen 1985) andis less beneficial (Tham 1988).

57

reduction in the volume of the more valuable hardwoods, such as Q:lercus IUbra. (Kelty 1989).

In Japan a mixture of akamatsu (Pinus densiflora) (Cbamaecyparis obtusa) resulted in a greater overall volume, volume of hinoki (Kawahara and Yam3IlOto 1986) .

I!mcpe.

and hinoki rut a lCMer

The admixture of beech (Fagus sylvatica) with spruce (Picea abies) is cla.im2d to increase total yields by 15% (Schutz 1989) . This is, hcMever, less an example of an interaction between the species than a reflection of the fact that the spruce ~ faster than the beech; pure spruce stands may be even more productive.

The interaction of Picea abies and Pinus sylvestris has been examined in sane detail in Scandinavia (Jonsson 1961) . A positive interaction, known as the ''mixed species effect", has been identified when pine and spruce are mixed on sites where both species can be expected to do well . The benefits of this effect reduce as the site changes to favour one or other of the species - drier, less fertile sites favour pine; wetter, more fertile sites favour spruce . There is also a oorresponding tendency for the favoured species to becane daninant and to fonn IlOIlospecific stands, or at least a mosaic of monospecific groups. This tendency has also been noted with other species in Holland (Heybroek and Tol 1985). The mixed species effect varies with the parameter measured; for height it is positive for both species; for diameter grcwth, hcMever, it is positive for pine, rut of no effect or slightly negative for spruce (Jonsson 1961). M:Jre recent work on pine/spruce mixtures on Calluna heaths and peat has indicated a strong positive effect on the grcwth of Picea sitchensis (M:l.loolm et al 1990) . The mixed species effect (or synergy) makes a::IIparison between mixed and pure natural stands on different sites difficult, if the Site Index is defined by daninant height, since mixed stands will be tend to be a::IIpared with pure stands of a higher Site Index. This fact may have disguised the benefits of mixed stands (Jonsson 1961) . Site Index has then to be defined by the less precise nethod of ol::.serving soil characteristics, vegetation types and indicator species .

The interaction of birch with conifers is more ~lex. This has been investigated in two studies in Finland and Sweden (Mielikainen 1985; ThaIn 1988) using yield modelling techniques. The general interpretation of the interactions of birches with conifers is similar in the two studies, rut the yields and scale of benefits are much higher in Sweden; this may be an effect of site or only of the assllI1ptions made in the models. B. pendula, a pioneer species that initially dominates the main crop may have a beneficial effect on spruce (Picea abies), which is a shade tolerant speCies, even when the birch is retained to full rotation. Pine (Pinus sylvestris) is a shade intolerant species and therefore though birch increases yields in open stands, in close ~tition birch depresses height grCMth of the pine. One solution is to cut the birch back for the first seven or eight years until the pine has a 1 m height advantage (Mielikainen 1985), rut this would appear to reduce the value of the birch as a nurse crop. Birch should never be allCMed to remain to full rotation in pine stands, because the total yield will be depressed . B. pubescens may have a depressing effect on oonifers (Mielikainen 1985) and is less beneficial (ThaIn 1988).

58

Table 3 Spruce - Birch Yield estimates - Sweden

Pire MixedAge Species #/ha Ht Vol #/ha Ht Vol

F7ha m r7177-ha

25 Spruce 1936 5.3 39 1936 5.5 23

Birch - - - 600 15.8 78 thinnedat age 25

50 Spruce 1237 14.6 300 1238 15.0 300

Total yield 300 378

Source: Tham (1988)

Note: This assumes a light thinning of the spruce at age 30 & 40 years.

Thus by retaining the B. pendula an extra 78 m3/ha is obtained andthough this is at the expense of 40% of the spruce yield at age 25, thatdeficit is made up over the following 25 years to give an overall gain as muChas 25% in a 50 year rotation. The gain in yield is dependent on the abilityof the spruce to respond to release after being semi-suppressed, since shadeintolerant species do not have this ability. If B. ptiLescens is used the gainis sane 20 nO less, possibly because of the fast initial growth of this latterbirch species.

Table 4 Spruce-Birch & Pine-Birch Yield estimates - Finland

B. pendUla B. putescensTotal Saw Total Saw

Timber TimberVol e

Spruce SI 24(00) Rotation 90 years

Spruce 100% 425 266 415 257

+ Birch 25% 438 282 394 217

+ Birch 50% 433 251 390 184

Pine SI 28(1W) Rotation 80 years

Pine 100% 615 371B.pendula 100% 493 200Mixed 50% 625 350 birch thinned out age 40

Source: Mielikainen (1985)

Note: A 25% admixture of B. pendula in a stand of spruce increased totalyields by 3% and saw timber by 6% in comparison to a pure spruce stand, buta 50% mixture resulted in a lower increase of either spruce or pine and adepression of saw timber production.

The evidence fram Sweden and Finland suggests that a "mixed species"effect can be Obtained with careful management, but interpretation andextrapolation of the results is not simple. In the first place, the bircharises f ULL natural regeneration, rather than from planted stock, and secondly

58

Table 3 Spruce = Birch Yield estimates = SWeden

Pure Mixed ~ S~cies #/ha Ht Vol ~ Ht vol

m ii?7ha m ii?7ha 25 Spruce 1936 5 . 3 39 1936 5.5 23

Birch 600 15.8 78 thinned at age 25

50 Spruce 1237 14.6 300 1238 15.0 300

Total yield 300 378

Source: Tham (1988)

Note: This assumes a light thinning of the spruce at age 30 & 40 years.

Thus by retaining the B . pendula an extra 78 m3/ha is obtained and though this is at the expense of 40% of the spruce yield at age 25, that deficit is made up over the following 25 years to give an overall gain as much as 25% in a 50 year rotation. The gain in yield is dependent on the ability of the spruce to respond to release after being semi-suppressed, since shade intolerant species do not have this ability. If B. pubescens is used the gain is sore 20 m3 less, possibly because of the fast initial growth of this latter birch species.

Table i Spruce-Birch ~ Pine-Birch Yield estimates = Finland

B. pendula B. pubescens Total Saw Total Saw

T~r T~r

----------------------- vol m3 -----------------

Spruce SI 24(100) Rotation 90 years

Spruce 100% + Birch 25% + Birch 50%

425 438 433

266 282 251

Rotation 80 years

371 200

415 394 390

Pine SI 28 (100)

Pine 100% B.pendula 100% Mixed 50%

615 493 625 350 birch thinned out age 40

Source: MieliJtiiinen (1985)

257 217 184

Note: A 25% admixture of B. pendula in a stand of spruce increased total yields by 3% and saw t~r by 6% in ccrrparison to a pure spruce stand, rut a 50% mixture resulted in a lower increase of either spruce or pine and a depression of saw t~r production.

The evidence fran SWeden and Finland suggests that a "mixed species" effect can be obtained with careful managemant, rut interpretation and extrapolation of the results is not siIrple. In the first place, the birch arises fran natural regeneration, rather than fran planted stock, and secondly

59

the effect is more important on the stocking of the site as a determinant ofyield, than on yield at a given stocking. Despite the increase in woodproduction shown in experiments there are doubts whether, in practice, theadvantages can be clearly established (Agestam 1991).

It is much more difficult to construct a yield model for a bispecificstand than for a monospecific stand; eadh additional species compounds thedifficulties. Amodel has been developed for southern USA which assumes thatindividual carponents of mixtures behave very much the sane as for pure stands(Nelson 1964); there is no indication that this model has been tested in thetropics and it is not known whether it would be valid there.

Trcpics.

The outstanding example of the benefit of mixtures is the Ricalyptussaligna/Albizia talcataria experiments on the Hamakua coast of Hawaii on anabandoned sugar estate. In one experiment, whidh also included Acaciamelanoxylon as one treatment, a 40:60 Eucalyptus:Albizia mixture resulted ina 140% increase in total yield of wood over the pure E7.1calyptus at the age of65 months. Even when only the Eucalyptus component of the mixture wasconsidered that showed a 60% increase over the pure plot. A 50:50 mixture ofAcaciamelanoxylon and Eucalyptusgave a lesser respcnse,but even that showeda 50% overall increase and only a slight drop in the yield of Elica7yptus inthe mixture. The experiment received an application of fertilizer to alltreatments. (DeBell et al. 1985).

In another experirnent in which all treatments received fertilizer in thefirst year but only the Eucalyptus plot received further applications in eachof the follaaing three years, the admixture of 25% or less Albizia falcat,Iriaresulted in a drop in total yield at the age of 48 months, while if theproportion of Albizia was increased to 34% or higher then the total yield ofthe mixture was greater, but not significantly so, than the pure Eucalyptusplot. The yield of the alcalyptus in the mixtures was consistently less thanin the pure plot, but when the A_Zbizia component exceeded 50% the Eicalyptusindividual tree volumes were significantly greater than in the pure plot.There was no comparison with a plot of pure Albizia. As the comparison wasbeing made with a heavily fertilized pure plot of Eucalyptus the results werebiased against the mixture. It is assumed that a comparison with Eucalyptusreceiving standard rates would have shown all the mixtures in a much morefavourable light (DeBell et al. 1989).

59

the effect is IOClre ilrportant on the stocking of the site as a detenninant of yield, than on yield at a given stocking . Despite the increase in wood production s~ in exper:ilrents there are doubts whether, in practice, the advantages can be clearly established (Agestam 1991).

It is much IOClre difficult to construct a yield nodel for a bispecific stand than for a IroIlospecific stand; each additional species canpounds the difficulties . A =del has been developed for southern USA which assurres that individual c:arp:lI1ents of mixtures behave very much the saIOO as for pure stands (Nelson 1964); there is no indication that this =del has been tested in the tropics and it is not ~ whether it would be valid there.

T.tqlics.

The outstanding exanple of the benefit of mixtures is the Eucalyptus saligna/Albizia falcataria exper:ilrents on the Hamakua coast of Hawaii on an abandoned sugar estate. In one exper:ilrent, which also included Acacia melanaxylon as one treatnent, a 40:60 Eucalyptus:Albizia mixture resulted in a 140% increase in total yield of wood over the pure Eucalyptus at the age of 65 IroIlths. Even when only the Eucalyptus a:::rrg:xnent of the mixture was considered that slJa.led a 60% increase over the pure plot . A 50: 50 mixture of Acaciamelanaxylon and Eucalyptus gave a lesser response, rut even that slJa.led a 50% overall increase and only a slight drop in the yield of Eucalyptus in the mixture . The exper:ilrent received an application of fertilizer to all treatnents. (DeBell et al. 1985).

In another exper:ilrent in which all treatnents received fertilizer in the first year rut only the Eucalyptus plot received further applications in each of the following three years , the admixture of 25% or less Albizia falcataria resulted in a drop in total yield at the age of 48 IroIlths, while if the proportion of Albizia was increased to 34% or higher then the total yield of the mixture was greater, rut not significantly so, than the pure Eucalyptus plot. The yield of the Eucalyptus in the mixtures was consistently less than in the pure plot, rut when the Albizia canponent exceeded 50% the Eucalyptus individual tree volurres were significantly greater than in the pure plot . There was no CCIl1pClIison with a plot of pure Albizia. As the CCIl1pClIison was being made with a heavily fertilized pure plot of Eucalyptus the results were biased against the mixture. It is assurred that a CCIl1pClIison with Eucalyptus receiving standard rates would have s~ all the mixtures in a much IOClre favourable light (DeBell et al. 1989) .

Table 5:

ExperimentMixture

E.saligna-Albizia

1 65 monthsStems Dry Wgtper ha tonne/ha

2200 37.6 Eucal t 2396 93.7

1012 35.3 Eucalypt 2101 58.11012 16.2 Albizia 11%278 8.92024 51.5 2379 67.0

falcataria & E.saligna-Acacia melanoxylonmixtureHawaii.

60

Experiment 2 48 monthsMixture Stems Dry wgt

per ha tonne/ha

Eucalypt (standard 44.0fertilizer )

Source: DeBell et al. (1985, 1989)

It is to be inferred fram these figures that the beneficial effect ofthe nitrogen fixing Albizia falcataria (or Acacia melanoxylon) only takeseffect when there is a sufficiently high proportion of the nitrogen fixingspecies. This effect was noted in North America (see chapter 3).

The experiment was cxmducted on an old sugar estate, where soil nitrogenis likely to have been depleted, but other nutrients may still have been ingood supply. It should never be overlooked that on other sites in Hawaii thismixture has done poorly or has even failed.

In Espirito Santo, Brazil a mixture of Eucalyptus urophylla and Leucaenaleucocephala resulted in higher mortality in the eucalypt and lower totalyield at the age of seven years . It was thought that the mixture had promotedhumid conditions which had favoured the spread of spores of Cryphonectriacutensis which attadked the eucalypt . The plots had received nitrogenfertilizer which may have prohibited the N-fixing effect of the L. leucocephala(Mbraes de Jesus and Brouard 1989) .

Measurements of yields of mixed plantaticns have been made in the hillsof Nepal, not far from Kathmandu. Oarparative measurements of pure and mixedstands were not made, but the differential response to site of the plantedpines (P. roxbcryii, P. wallichiana and P. patula) and broadleaved speciesddrninated by Schirnawallichii, which appear naturally in the pine plantations,was apparent. In a ten year old plantation the yield (stem plus leaf) of thepines varied fram .8 to 6.7 tons/ha/year with the highest yields on oldgrazing sites which had few remnant broadleaved species, while the broadleafspecies (with yields of 1.8 to 6.7 tons/ha/year) did best on old forest sitesand on Abandoned cultivation on terraces. On these latter sites the pinessuffered from campetition with the broadleaved species (Mohns et al. 1988).

Eucalypt 838 58.2 Eucalypt 1562 57.8Aibizia 60% 1225 37.1 Aibizia 50%833 44.8

2063 95.3 2395 102.6

Eucalypt 815 53.4Albizia 66% 1632 50.8

2447 104.2

Eucalypt

EucalyptAcacia 50%

60

Table 5: E.saligna-Albizia falcataIia & E .saligna-Acacia melanoxylOl1 mixture

Experiment ! Mixture Stems

~ha

Eucalypt 2200

Eucalypt 1012 Acacia 50% 1012

2024

Eucalypt 838 AThizia 60% 1225

2063

Hawaii.

65 IlOl1ths Dry Wgt tonnejha

37 .6

35.3 16.2 51.5

58.2 37.1 95.3

Experiment 2 48 rronths Mixture -Stems Dry wgt

~ ha tonnejha

Eucalypt 2396

Eucalypt 2101 AThizia 11%278

2379

Eucalypt 1562 AThizia 50%833

2395

93 .7

58.1 8.9

67 .0

57.8 44.8

102.6

Eucalypt AThizia 66%

815 1632 --2447

53 . 4 50 .8

104.2

Eucalypt (standard 44 .0 fertilizer

Souroe: DeBell et al. (1985 , 1989)

It is to be inferred fram these figures that the beneficial effect of the nitrogen fixing Albizia falcataIia (or Acacia melanoxylon) only takes effect when there is a sufficiently high proportion of the nitrogen fixing species. This effect was noted in North America (see chapter 3) .

The experiment was conducted on an old sugar estate, where soil nitrogen is likely to have been depleted, rut other nutrients may still have been in good supply. It should never be overlooked that on other sites in Hawaii this mixture has done poorly or has even failed .

In Espirito Santo, Brazil a mixture of Eucalyptus urophylla and Leucaena leucocephala resulted in higher rrortality in the eucalypt and lower total yield at the age of seven years . It was thought that the mixture had praroted humid oonditions which had favoured the spread of spores of Cryphonectria cubensis which attacked the eucalypt. The plots had reoeived nitrogen fertilizer which may have prohibited the N-fixing effect of the L . leucocephala (M::lraes de Jesus and Brouard 1989) .

Measurements of yields of mixed plantations have been made in the hills of Nepal, not far fram Kathnandu . canparat i ve measurateIlts of pure and mixed stands were not made, rut the differential response to site of the planted pines (P. roxturgii, P . wallichiana and P . patula) and broadleaved species daninated by Schima. wallichii, which appear naturally in the pine plantations, was apparent. In a ten year old plantation the yield (stem plus leaf) of the pines varied fram .8 to 6 .7 tonsjha/year with the highest yields on old grazing sites which had few remnant broadleaved species, while the broadleaf species (with yields of 1.8 to 6.7 tonsjha/year) did best on old forest sites and on abandoned cultivation on terraoes . On these latter sites the pines suffered fram ccrrpetition with the broadleaved species (M::lhns et al. 1988) .

Conclusions on yields.

There are same examples in both temperate and tropical zones of highertotal yields of wood volume of mixtures as compared to pure plantations. Butaccurate species/site matching and the choice of complementary species iscritical to success and the effect of one species on another can Change withsite and in time; gains are also dependent on the timing and scale of forestmanagement interventions. Furthermore the total gains may be small and inindustrial plantations may not be on the most valuable component of themixture.

The construction of polyspecific yield models of tropical rainforestspecies in plantatians, given the potential number of species and the ladk ofdata, is difficult. But just because it may prove *possible to predict thedevelopment of mixtures in the tropics with any precision, it does not followthat such mixtures should not be tried.

The number of examples of yield records in the tropics are limited andwhere mixtures have not resulted in gains, it often appears that there hasbeen a laCk of clarity in defining the objective of the mix and therefore apossibility-that the species are inappropriate. The outstanding example fromHawaii quoted above must be treated with caution as a general model becauseof the confounding factors applying there.

Yieldof wood is a good measure of success of industrial plantations andfor fuelwood and pole plantations, bit it is inapprppriate where plantationshave been established for environmental reasons - to control erosion, enhancesoil fertility, ameliorate the microclimate or to provide direct socialbenefits. The evaluation of these "non-market" benefits are discussed in moredetail in the next chapter.

6161

Concl''5jms 00. yields.

There are sore exarrples in roth tarperate and tropical zones of higher total yields of wood voluroo of mixtures as ~ to pure plantations. But accurate speCies/site matching and the choice of canplementary species is critical to success and the effect of one species on another can change with site and in tine; gains are also dependent on the timing and scale of forest management interventions. FW:theIIOOre the total gains may be small and in industrial plantations may not be on the rrost valuable canponent of the mixture.

The construction of polyspecific yield models of tropical rainforest species in plantations, given the potential mxnber of species and the lack of data, is difficult . But just because it may prove ~sible to predict the developnent of mixtures in the tropics with any precision, it does not follow that such mixtures should not be tried.

The number of exarrples of yield records in the tropics are limited and where mixtures have not resulted in gains, it often appears that there has been a lack of clarity in defining the objective of the mix and therefore a possibility that the species are inappropriate . The outstanding exarrple fran Hawaii quoted arove nrust be treated with caution as a general model because of the confounding factors applying there.

Yield of wood is a good measure of success of industrial plantatiOns and for fuelwood and pole plantations, but it is inappropriate where plantations have been established for envirornrental reasons - to control erosion, enhance soil fertility, aneliorate the microclimate or to provide direct social benefits . The evaluation of these "non-market" benefits are discussed in rrore detail in the next chapter .

7. EIDONCMICS.

Economics concerns the commitment of resources to production and thereturn in yields of value to society. Plantation forestry in tropicalcountries may be favoured by the availability of land with low opportunitycost and the availability-of labour at lad wage costs. Technological know-hcwand managerial skills, however, may he more scarce and therefore more costly.The physical environment may be favourable to rapid, high volume growth offavoured species. This has a commensurate cost in that weed growth is alsoheavy and therefore expensive to control. The local market value of theproduct may be relatively law because of law demand from the low incomeeconamy due to the availability of low-cost alternative wood material framnatural forest or because of the distance and cost of transportation involved-in reaching alternative markets. The equation alters as the local economydevelops, changing both the supply cost of inputs and the demand for products.

Aninvestment in tree planting matures over several years and it is mostimportant in assessing such an investment to take account of the displacementin time between the expenditure and the income. In the rase of many tropicaltree crops this displacemaatmay be relatively short compared with equivalentperiods in temperate countries - 10 to 20 years campared with 50 to 100 yearsfor example, to produce final yields of 200 to 400 m3/ha.

The concept of Net Present Value provides a useful tool for evaluatingon a comparable basis expenditure and income occurring at different times inthe production cycle and thereby allowing the comparison of the"profitability" of different crops and different options within crops. In suchassessments the assumption is made that all costs and benefits can beexpressed in monetary terms and that a discount rate can be selected whichrelates all values occurring at different times to present day values.

In industrial plantations, where revenue from sales is the prime benefitand the inputs are bought and sold in established markets, a financialanalysis is straightforward. Thus a positive financial return may be expectedfram a high-yielding species in favourable and constant growing conditionswith established markets, as with plantations of eucalypts at Aracruz inBrazil or at Pointe Noire in Congo. On the other hand, cost/benefit analysisof the United Kingdom Forestry Commission plantations, considering only"market" benefits gave a negative financial return. Including "non-market"values and environmental benefits, such as amenity, recreation, preservationof the landscape and the function of plantations as carbon sinks indicated apositive economic return (Batan 1991). When the main objective of aplantation is to rehabilitate degraded sites, the protection of watershedsor soil conservation, then the correct pricing of environmental benefitsbecomes even more important although the criteria for assessing environmentalbenefits are not well developed. It is to be noted, however, that thenecessity for pricing environmental benefits is becoming generally accepted.An analysis of rates of return of Wbrld Bank forestry projects showed 15-21%for 8 Watershed Rehabilitation projects, 15-30% for 27 Agroforestry/Ftelwood/Community/Social projects, bit only 10-15% for 15 Industrial plantationprojects (Spears 1985). However, it is not clear to what extent "non-market"value:shave been included in the economic analysis of any plantation projects.

Scarcity of investment resources leads financial authorities to adopthigh discount rates which favour high yielding species, short rotations andmanagement policies of minimum cost and high output, which in the absence of

6262

7. PIXNJlICS.

Econanics concerns the ccmnitment of resources to production and the return in yields of value to society. plantation forestry in tropical countries may be favoured by the availability of land with la-r opportunity cost and the availability of labour at la-r wage costs. Technological knC1N-ha-i' and managerial skills, tJa..iever, may be !lOre scarce and therefore !lOre costly. The physical environment may be favourable to rapid, high volurre grCMth of favoured species. This has a cx::mrensurate cost in that weed grCMth is also heavy and therefore expensive to control. The local market value of the product may be relatively la-r because of la-r demand fran the la-r ineate ec:onany due to the availability of la-r-cost alternative ~ material fran natural forest or because of the distance and cost of transportation involved -in reaching alternative markets. The equation alters as the local ec:onany develops, changing roth the supply cost of inputs and the demand for products.

An investment in tree planting matures over several years and it is !lOSt :irrIJortant in assessing such an investment to take account of the displacement in time between the expenditure and the ineate . In the case of many tropical tree crops this displaC€!OOllt may be relatively short canpared with equivalent periods in temperate countries - 10 to 20 years canpared with 50 to 100 years for example, to produce final yields of 200 to 400 m3/ha.

The concept of Net Present Value provides a useful tool for evaluating on a canparable basis expenditure and incane oc=ing at different times in the production cycle and thereby alla-ring the carparison of the "profitability" of different crops and different options within crops. In such assessments the assumption is made that all costs and benefits can be expressed in monetary tenns and that a discount rate can J:e selected which relates all values oc=ing at different times to present day values.

In industrial plantations, where revenue fran sales is the prime benefit and the inputs are !::ought and sold in established markets, a financial analysis is straightforward. Thus a positive financial return may J:e ~cted fran a high-yielding species in favourable and constant gra-ring conditions with established markets, as with plantations of eucalypts at Aracruz in Brazil or at Pointe Noire in Congo. On the other hand, costjbenefit analysis of the United Kingdon Forestry Cormission plantations, considering only "market" benefits gave a negative financial return. Including "non-market" values and environmental benefits, such as arrenity, recreation, preservation of the landscape and the function of plantations as carbon sinks indicated a positive econanic return (Bate:nan 1991). When the main objective of a plantation is to rehabilitate degraded sites, the protection of watersheds or soil conservation, then the correct pricing of environmental benefits becanes even !lOre :irrIJortant although the criteria for assessing environmental benefits are not well developed. It is to J:e noted, tJa..iever, that the necessity for pricing environmental benefits is becaning generally accepted. An analysis of -rates of return of World Bank forestry projects shCMed 15-21% for 8 Watershed Rehabilitation projects, 15-30% for 27 Agroforestry/FUel~/ carmunity/Social projects, rut only 10-15% for 15 Industrial plantation projects (Spears 1985). Ha.-lever, it is not clear to what extent "non-market" values have J:een included in the econanic analysis of any plantation projects.

Scarcity of investment resources leads financial authorities to adopt high discount rates which favour high yielding species, short rotations and managem:mt policies of minimum cost and high output, which in the absence of

63

adequate trials and experience may also tend to involve high risk. Such apolicy will oblige managers to employ quick acting, often expensive solutionsto problems such as the addition of artificial fertilizers to relieveunforeseen nutrient problems, the use of Chemicals and aerial spraying toovercame outbreaks of disease and pests. Where benefits are perceived frunthe establishment of mixed plantations, on the other hand, they may beachieved at the expense of laaer yield. This "low input/low output/law risk"approach is likely to be of value in long rotation crops, bit would be ruledout by high compound interest rates over long periods. Sane authors havequestioned whether high discount rates are appropriate for the analysis oflong term projects and have also suggested that the longterm "real" interestrates in industrial countries are only in the order of 2-4% (Leslie 1987).

Be that as itmay, it is clearly ipprudent to enter into an investmentin plantations without ensuring that the expected returns will be sufficientto repay the costs and liabilities involved in the project. Society, throughthe Government or the community, may be willing to increase funding in orderto pay to secure benefits from whidh there is no direct cash return to theinvestor, bit which are perceived to be of value to the community- soil andwater conservation, amenity and other environmental benefits are examples.Clear identification of these benefits in the objectives of a plantationproject is essential to a sound economic evaluation.

The economics of mixtures.

Mixtures may have advantages of symbiosis, although the evidencepresented in Chapter 6 on the effects on yield of wood is not conclusive.Theymay have advantages of spreading the income-generating period through theremoval and sale of the products of one of the species early in the rotation.Species may be mixed as an insurance against the risk that one or another willbe attacked by pests or disease. On the ground that the trees remaining willhave gained from the intermixture during formative years the loss fram pestsor disease may be less than proportional to the deaths since the dying onesmay also be harvested. Finally, there may be an amenity, aesthetic orecological preference for mixture.

The economics of each of these types of scheme maybe analyzed throughthe present value assessment discussed Above, through appropriate estimationof costs and revenue and evaluation of non-market benefits.

Temperate experience.

In Scandinavia thought has been given to the theory of mixed plantationeconomics, bit is mainly centred on the management of naturally occurringbroadleaved species in planted conifer stands. Because harvesting is so longafter establishment and prices for the final product are unpredictable, theargument has been proposed that:

the initial investment should provide a choice (i.e. should be amixture), not least because there is a strong possibility that over along rotation objectives may be redefined;

thinning and a final choice between the two components for the finalcrop should be delayed as long as possible.

63

adequate trials and experience may also tend to involve high risk. Such a policy will oblige managers to employ quick acting, often expensive solutions to problans such as the addition of artificial fertilizers to relieve unforeseen nutrient problans, the use of chanicals and aerial spraying to overcare outbreaks of disease and pests. Where benefits are perceived fran the establisJ:ment of mixed plantations, on the other hand, they may be achieved at the expense of lower yield. This "low input/low output/low risk" approach is likely to be of value in long rotation crops, rut ~d be ruled out by high a:JI1?OllIld interest rates over long periods. Sane authors have questioned whether high discount rates are appropriate for the analysis of long tenn projects and have also suggested that the long tenn "real" interest rates in industrial countries are only in the order of 2-4% (leslie 1987).

Be that as it may, it is clearly ilrprudent to enter into an investment in plantations without ensuring that the expected returns will be sufficient to repay the costs and liabilities involved in the project. Society, through the Government or the a::mmmity, may be willing to increase funding in order to pay to secure benefits fran which there is no direct cash return to the investor, rut which are perceived to be of value to the camn.mity - soil and water conservation, amenity and other enviroIlllEIltal benefits are exarrples. Clear identification of these benefits in the objectives of a plantation project is essential to a sound econanic evaluation.

'l.'he ecuuoics of m:ixt:mes.

Mixtures may have advantages of symbiosis, although the evidence presented in Chapter 6 on the effects on yield of wood is not conclusive. They may have advantages of spreading the incare-generating period through the reroval and sale of the products of one of the species early in the rotation. species may be mixed as an insurance against the risk that one or another will be attacked by pests or disease. On the ground that the trees remaining will have gained fran the intermixture during fonnative years the loss fran pests or disease may be less than proportional to the deaths since the dying ones may also be harvested. Finally, there may be an amenity, aesthetic or e=logical preference for mixture.

The econanics of each of these types of sche!re may be analyzed through the present value assesSllalt discussed above, through appropriate estimation of costs and revenue and evaluation of non-market benefits.

'J.'eIIperate experience.

In Scandinavia thought has been given to the theory of mixed plantation econanics, rut is mainly centred on the managenent of naturally occurring broadleaved species in planted =nifer stands. Because harvesting is so long after establisJ:ment and prices for the final product are unpredictable, the a.rgurrent has been proposed that:

the initial investment should provide a choice (Le. should be a mixture), not least because there is a strong possibility that over a long rotation objectives may be redefined;

thinning and a final choice between the two canponents for the final crop should be delayed as long as possible.

64

This gives the best opportunity to identify the species that will havethe greatest chance of commanding the higher value at final felling andproviding that both species are equally suited to the site, at no extra riskof the biological failure of one of the species. This principle has, ofcourse, to be constrained within silvicultural and management limits; forexample, overstocking may lead to stagnation, or late thinnings may causeexcessive damage to residuals. It is also confined to market values ratherthan to the values of other benefits, nor does it take into account the effecton the soil over several generations. Within these limitations, the theoryassumes that relative price dhanges are essentially random, but are relatedto previous prices in inverse proportion to the time elapsed. In other wordspredictions of prices are likely to be more accurate over a short time spanthan over a long one. It has been suggested that economic gains frultmixedstands, which may in addition include eA.rly returns fram more valuablethinnings, have been underestimated and are in all probability much largerthan the much-discussed, but often small and doUbtful mixed species effect(Lohmander 1990). It should be noted that in Scandinavia the secondaryspecies, which are mcstly bdrch and aspen, and also the regeneration ofconifers, occur naturallyin plantations. The broadleaved species have untilcomparatively recently been treated as weeds; it is only since a market forbirdh has re-developed that it has contributed to income.

The argument is sometimes made that the inclusion of a secondary speciescan improve the quality and hence the profitability of the main species.Examples include:

suppress ion of epicormics on red oak and the maintenance of a groundcover suitable for odk regeneration by the hemlock understorey (Kelty1989);

increased bole length in cherrybark oak in competition with Liquidambar(Clatterbuck and Hodges 1988) ;

suppression of spruce side branches by B. pendula resulting in a 6%gain in saw tiMber yields (Mielikainen 1985). But though the admixtureof 25% B. pendula resulted in a small gain in total yield of pines itapparently depressed saw timber yields by 5% - see Table 4;

other studies show that retention of birch increased the height ofself-pruning on pine and reduced the knotty core; any extra tendingcosts paid were covered by returns. These were, however, effects ofdensity rather than of species mixture and could - though at extracost - prObably have been achieved by closer spacing of pines (Haegg1988, 1989, 1990).

It is not known haw large these benefits will be.

Tropical experience.

No economic analysis of mixed plantations in the tropics was noted inthis study. In the accounts of the ElIcalyptus/Albizia experiments in Hawaiithere was no mention of the economics of gravaing the mixture. The trees werebeing raised for an energy project, therefore the prime Objective must havebeen to grow as much biomass as possible. Although the lighter A. falcatoriawood would be more expensive to handle because of the larger number of stemsand because it is branchy it would be more liable to felling damage, its value

64

This gives the best opportunity to identify the species that will have the greatest chance of ccmnanding the higher value at final felling and providing that both species are equally suited to the Site , at no extra risk of the biological failure of one of the species. This principle has, of course, to be constrained within silvicultural and managarent limits; for exarrple, overstocking may lead to stagnation, or late thinnings may cause excessive damage to residuals. It is also confined to market values rather than to the values of other benefits, nor does it take into account the effect on the soil over several generations. Within these limitations, the theory assumes that relative price changes are essentially randan, rut are related to previous prices in inverse proportion to the time elapsed. In other YJOIDs predictions of prices are likely to be IlOre accurate over a short time span than over a long one. It has been suggested that econanic gains fran mixed stands, which may in addition include early returns fran IlOre valuable thinnings, have been underestimated and are in all probability much larger than the much-discussed, rut often small and doubtful mixed species effect (Lohrnander 1990). It should be noted that in Scandinavia the secondary species, which are IlOStl y birch and aspen, and also the regeneration of conifers, oc= naturally in plantations. The broadleaved species have until canparatively recently been treated as weeds; it is only since a market for birch has re-developed that it has contrihlted to incane.

The argument is saretimes made that the inclusion of a secondary species can ilrprove the quality and hence the profitability of the main species . Examples include:

suppression of epicormics on red oak and the maintenance of a ground cover suitable for oak regeneration by the hemlock understorey (Kelty 1989) ;

increased bole length in cherrybark oak in canpetition with LiquidBInbar (Clatterruck a.'ld Hodges 1988);

suppression of spruce side branches by B. pendula resulting in a 6% gain in saw timber yields (Mielikainen 1985). But though the admixture of 25% B. pendula resulted in a small gain in total yield of pines it apparently depressed saw timber yields by 5% - see Table 4;

other studies shc:M that retention of birch increased the height of self-pruning on pine and reduced the knotty core; any extra tending costs paid ~re covered by returns. These ~re, hcMever, effects of density rather than of species mixture and could _ . though at extra cost - probably have been achieved by closer spacing of pines (Haegg 1988, 1989, 1990).

It is not known hc:M large these benefits will be.

Tnlpical experience.

No econanic analysis of mixed plantations in the tropics was noted in this study. In the accounts of the Eucalyptus/Albizia experiments in Hawaii there was no rrention of the econanics of growing the mixture. The trees ~re being raised for an energy project, therefore the prime objective must have been to grow as much bianass as possible. Although the lighter A. falcataria YJOOd YJOuld be IlOre expensive to handle because of the larger number of stems and because it is branchy it YJOuld be IlOre liable to felling damage, its value

65

as biomass would he nearly as high as that of the eucalypt. In an energyplantation the mixture, given the results quoted, can be expected to be aneconomic success. But if the objective had been to gro the eucalyptus forsaw tiMber, the economic advantages of the mixture would not have been soobvious; the value of the two tiMbers in relation to end use is important.

In Nigeria, as mentioned earlier, Nauclea diderrichii (opepe) is usedas a nurse crop formembers of the Meliaceae family - EY2tandrophragma, 10]aya,Lovoa - thereby reducing the incidence of Hypsipyla robusta and giving anintermediate yield from the sale of the poles of the Opepe. It was found thatthe Internal Rate of Return for Opepe grown on a tiMber rotation of 60 yearswas 4.5% whereas when it was mixed 5 Opepe to 1 14e1iaceae the IRR increasedslightly, to 4.6% over the same rotation (Ball 1979). The reason for thesmall difference between the two rates was the lower final volume of theMeliaceaecampared to pure Opepe, despite the higher value of the Afeliaceae.It was also found that the high demand for the Opepe poles led to felling ofthe hest-formed in the early thinnings, leaving the poorest for the finalcrop, and causing severe damage to the final crop trees in the process.

The mixed plantations of Swietenia/Securir2ega being tried in the SolomonIslands also have this potential. But in this and other rases, the extraincome is only possible if there is a market for thinnings. In the nineteenfifties there was no local market for nine year old thinnings in Nigeria(Henry 1960) whereas the rapid extension of the electricity supply in thenineteen seventies led to a high but unforeseen demand for Opepe poles. In

India the use of GMelina artorea as a nurse for Dipterocarpus turbina tusworked well silviculturally, but the nurse crop had to be removed before itwas saleable and there were problems in controlling the coppice regrowth(Indian Forest Service 1939).

In Scandinavia it has been shown (above) that the retention of naturallyoccurring mixtures can be economically advantageous. A comparable situationin the tropics - invasion of a plantation by pioneer species such as Mararangaspp., Anthocephalus chinensis, Neoboutonea macrocalyx or Croton spp. caneasily be envisaged. But the interaction with the main species, particularlyif that is an exotic conifer, may not be so benign as in Scandinavia andmarkets for the secondary species have not been widely developed.

Long term gains and losses.

The benefits of mixed planting to soil improvement and the maintenanceof site conditions over several rotations are of the utmost importance. Theseare benefits that are difficult to quantify or, since the time scale is solong, to accommodate in an economic model. The situation can arise in whicha crop can deplete a site of one nutrient without necessarily reaching acondition of deficiency in the first few rotations. The yields of that cropwould be considered sustainable, if no account were taken of the loss ofnutrients and the risk of a sudden decline in yield when the threshold forthat nutrient is crossed. In the long run what is needed is sustainedfertility as well as sustained yields. To achieve this it will be necessaryto incur costs or to forgo short term financial benefits. The short term (oneor two rotations) economic models usually applied should not be used to blindforesters to the risks of long term site deterioration, which can possibly beameliorated by the use of mixtures.

65

as bianass would be nearly as high as that of the eucalypt. In an energy plantation the mixture, given the results quoted, can be expected to be an econanic success. But if the objective had been to grew the eucalyptus for saw timber, the econanic advantages of the mixture would not have been so obvious; the value of the two timbers in relation to end use is important.

In Nigeria, as mentioned earlier, Nauclea diderrichii (opepe) is used as a nurse crop for members of the Meliaceae family - Entandrophragma, Khaya, Lovoo - thereby reducing the incidence of Hypsipyla robusta and giving an interrrediate yield fran the sale of the poles of the Opepe. It was found that the Internal Rate of Return for Opepe grcwn on a timber rotation of 60 years was 4.5% whereas when it was mixed 5 Opepe to 1 Meliaceae the IRR increased slightly, to 4.6% over the sarre rotation (Ball 1979). The reason for the small difference be~ the two rates was the lower final volume of the Meliaceae CCIlp3red to pure Opepe, despite the higher value of the Meliaceae. It was also found that the high demand for the Opepe poles led to felling of the best-fomed in the early thinnings, leaving the poorest for the final crop, and causing severe damage to the final crop trees in the process .

The mixed plantations of SWietenia/Securinega being tried in the Solaoon Islands also have this potential. But in this and other cases, the extra ina::rre is only possible if there is a market for thinnings. In the nineteen fifties there was no local market for nine year old thinnings in Nigeria (Henry 1960) whereas the rapid extension of the electricity supply in the nineteen seventies led to a high rut unforeseen demand for Opepe poles. In India the use of Gnelina arborea as a nurse for Dipterocarpus turbinatus worked well silviculturally, rut the nurse crop had to be rerroved before it was saleable and there were problems in controlling the coppice regrcwth (Indian Forest Service 1939).

In Scandinavia it has been shewn (above) that the retention of naturally oc=ing mixtures can be econanically advantageous. A a::uparable situation in the tropics - invasion of a plantation by pioneer species such as Macaranga spp., Anthocephalus chinensis, Neoboutonea macrocalyx or croton spp. can easily be envisaged. But the interaction with the main speCies, particularly if that is an exotic conifer, may not be so benign as in Scandinavia and markets for the secondary species have not been widely developed.

IaIg teIm gains and losses .

The benefits of mixed planting to soil linprovanent and the maintenance of site conditions over several rotations are of the utIrost importance. These are benefits that are difficult to quantify or, since the time scale is so long, to acccnm::rlate in an econanic m:del. The situation can arise in which a crop can deplete a site of one nutrient without necessarily reaching a condition of deficiency in the first few rotations. The yields of that crop would be considered sustainable, if no account were taken of the loss of nutrients and the risk of a sudden decline in yield when the threshold for that nutrient is crossed. In the long run what is needed is sustained fertility as well as sustained yields. To achieve this it will be necessary to incur costs or to forgo short tenn financial benefits. The short tenn (one or two rotations) econanic rrodels usually applied should not be used to blind foresters to the risks of long tenn site deterioration, which can possibly be arreliorated by the use of mixtures.

Risk evalua-tian.

Economic analysis should include same evaluation of the risk of failureattached to any enterprise. Those who advocate mixed plantations are oftenmotivated by the desire to reduce the risk of a major failure from sameunpredictable catastrophe, such as insect or fungal attack or drought etc.The concept of mixtures as an insurance, discussed in Chapters 3 and 6, is arecognition of this risk. However, this insurance may entail a cost inreduced yieldR and higher establishment and management costs. In New Zealand,where 85% of the plantations are planted to Pinus radiata, the argument hasbeen proposed (Burdon 1982) that a policy of investing in one species isjustified on the following grounds:

that P.radiata has been well matched to the sites available in NewZealand and there is no particular reason to anticipate catastrophicepidemics,

that should a serious disease or pest arise, such as Dothistraria pini,New Zealand has the financial and staff resources to combat it,

that there is no evidence that P.radiata is any more susceptible topests or diseases than native naturally regenerated stands, sudh as,for example, insect (Platypus) attacks on Atthotagus,

that within this one species an investment has been made in maintainingas broad a genetic base as possible, which reduces the chances ofcatastrophic epidemics such as have occurred in poplars,

that silvicultural management includes early and heavy thinnings androtations are short, so that in the event of an epidemic harvesting canbe brought forward at a minimum loss and the affected site can be re-established to another provenance or species. In the past epidemics,e.g. Sirex wood wasp, have been the consequence of lack ofsilvicultural management, and

that researdh into other species potentially suitable to New Zealandconditions is being carried out and tested alternative species could beintroduced into the plantation programme at short notice if required.

In short, New Zealand having selected a species for wood production andwatershed protection that is well matched to the available sites and havingmade a careful analysis of the risks, has decided that it is more advantageousto continue to invest in a proven highly profitable species rather than toreduce profits by investing in a range of lower yielding species.

The risk analysis that has been undertaken at Aracruz, Brazil hasarrived at a similar answer. The objective is high yields over a shortrotation. On the one hand the risks attached to reduced species and within-species diversity in the production populations are considered to be small andthere is a good capability for handling any "catastrophe". On the other handthe convenience of management and the gain in yields of monoclonal plantationsare highly attractive. Provided precautions sudh as maintaining a largegenetic base in parallel base populations are taken, a reduction in speciesand within-species diversity can he justified.

6666

Risk evaluation.

Econanic analysis should include SCDe evaluation of the risk of failure attached to any enterprise. Those who advocate ~ plantations are often I!()tivated by the desire to reduce the risk of a rrajor failure fran SCDe

unpredictable catastrophe, such as insect or fungal attack or drought etc. The concept of mixtures as an insurance, discussed in Chapters 3 and 6, is a rerognition of this risk. !biever, this insurance rray entail a cost in reduced yields and higher establisbrrent and managEm2llt costs . In New Zealand, where 85% of the plantations are planted to Pinus radiata, the argument has been proposed (Burdon 1982) that a policy of investing in one species is justified on the follOWing grounds:

that P.radiata has been well rratched to the sites available in New Zealand and there is no particular reason to anticipate catastrophic epidemics,

that should a serious disease or pest arise, such as Dothistrana pini, New Zealand has the financial and staff resources to ccmbat it,

that there is no evidence that P.radiata is any I!()re susceptible to pests or diseases than native naturally regenerated stands, such as, for ~le, insect (Platypus) attacks on Nothofagus,

that within this one species an investm:mt has been rrade in rraintaining as broad a genetic base as possible, which reduces the chances of catastrophic epidemics such as have occurred in poplars,

that silvicultural managEm2llt includes early and heavy thinnings and rotations are short, so that in the event of an epidemic harvesting can be brought fornard at a minimum loss and the affected site can be re­established to another provenance or species . In the past epidemics, e . g . Sirex \oJOOd wasp, have been the consequence of lack of silvicultural managEm2llt, and

that research into other species potentially suitable to New Zealand conditions is being carried out and tested alternative species could be introduced into the plantation prograrme at short notice if required.

In short, New Zealand having selected a species for \oJOOd production and watershed protection that is well rratched to the available sites and having rrade a careful analysis of the risks, has decided that it is I!()re advantageous to continue to invest in a proven highly profitable species rather than to reduce profits by investing in a range of lower yielding species .

The risk analys1.s that has been undertaken at Aracruz, Brazil has arrived at a similar answer. The objective is high yields over a short rotation. On the one hand the risks attached to reduced species and within­species diversity in the production populations are considered to be srrall and there is a good capability for handling any "catastrophe" . On the other hand the convenience of managEm2llt and the gain in yields of =noclonal plantations are highly attractive. Provided precautions such as rraintaining a large genetic base in parallel base populations are taken, a reduction in species and Within-species diversity can be justified.

67

Many developing countries wish to invest in industrial plantations buthave neither the resources for research to counter epidemics nor the knowledgeof a species that the foresters of New Zealand have of P.radiata or thatAracruz Cellulose has of Eucalyptus spp. For developing countries a policyof spreading the risk by having a mixture of species in industrial shortrotation plantations in the broad sense, in which the species are carefullymatched to the sites available, may be desirable. Where long rotation cropsare proposed the policies of reducing the risk by careful species/sitematching and of spreading the risk by using more than one species are of asmuch (if not more) importance as with short rotation crops, and there may beopportunities for intimate mixtures if circumstances permit - that is, ifthere is sufficient knaaledge of the silviculture of the species proposed forthe mixture, the objectives can be met or other benefits can be identified.Where the objective is watershed management or rehabilitation of degradedlands then mixtures, especially in the sense of encouraging an understorey,are often the most appropriate composition.

Conclusions on economics.

Little fully evaluated informationon the economics of growingmixturesin temperate regions or in the tropics was found in this study. Theorysuggests that establishingmixed plantations makes it possible to keep optionsopen as long as possible in order to obtain the best prices or range ofproducts. If mixtures, such as birdh/spruce in Scandinavia, can be obtainedat little cost it is possible that the economic gains can be added to anysynergies in yields that there may be, but there are indications that theexpenses of establishing and maintaininixed industrial plantations in thetropics are often high. There are, however, circumstances where non-marketbenefits associated with amenity or ecology are regarded as important (seebelow).

The profitability and overall desireability of a mixture may depend onthe ability to harvest one component of a mixture parly in the rotation as inthe case of Nauclea diderichii in mixture with Atliaceae in Nigeria. Theincreasing local markets for small wood or other products (such as rattan)will favour thinnings and in doing so will make the management of mixedspecies crops easier because there will be a wider range of species that canbe considered for mixtures. The acre species there are that have a commercialvalue the more economically attractive mixtures become, though thesilvicultural requirements for releasing the main crop do not always coincidewith the best moment for marketing thinnings.

The economic and biological success of mixed plantations will depend anthe availability- of adequate financial resources and of skilled staff as wellas species suited to the sites, compatible with the other components andmatched to the end uses available.

The above has considered only the effect on returns arising frommixtures in the provision of wood products. Species may be included inmixtures for other values - for instance, for the provision of fodder, fruitor nuts, or for the soil-improving properties of their 'ves or associatednitrogen-fixingbacteria, or for their visual appearance. These are all validreasons for planting mixtures, but they are difficult to evaluate becausetheir products are not usually traded in markets.

67

Many developing countries wish to invest in industrial plantations rut have neither the resources for research to counter epidemics nor the kn<Mledge of a species that the foresters of New Zealand have of P.radiata or that Aracruz Cellulose has of Eucalyptus spp. For developing countries a policy of spreading the risk by having a mixture of species in industrial short rotation plantations in the broad sense, in which the species are carefully matched to the sites available, may be desirable. Where long rotation crops are proposed the policies of reducing the risk by careful species/site matching and of spreading the risk by using rrore than one species are of as much (if not rrore) :irrq;lortance as with short rotation crops, and there may be opportunities for intimate mixtures if circumstances permit - that is, if there is sufficient kn<Mledge of the silviculture of the species proposed for the mixture, the objectives can be met or other benefits can be identified. Where the objective is watershed managemmt or rehabilitation of degraded lands then mixtures, especially in the sense of encouraging an understorey, are often the rrost appropriate ~ition .

Little fully evaluated infonnation on the econanics of gr<Ming mixtures in t~rate regions or in the tropics was found in this study. Theory suggests that establishing mixed plantations makes it possible to keep options open as long as possible in order to obtain the best prices or range of products. If mixtures, such as birch/spruce in ScandinaVia, can be obtained at little cost it is possible that the econanic gains can be added to any synergies in yields that there may be, rut there are indications that the expenses of establishing and maintaining mixed industrial plantations in the tropiCS are often high. There are, ha;ever, circumstances where non-market benefits associated with amenity or ecology are regarded as :irrq;lortant (see bel<M) .

The profitability and overall desireability of a mixture may depend on the ability to harvest one carq;x:>nent of a mixture early in the rotation as in the case of Nauclea diderichii in mixture with M:liaceae in Nigeria. The increasing local markets for small wood or other products (such as rattan) will favour thinnings and in doing so will make the managemmt of mixed species crops easier because there will be a wider range of species that can be considered for mixtures . The rrore species there are that have a ccm:rercial value the rrore econanically attractive mixtures becane, though the silvicultural requiremmts for releasing the main crop do not always coincide with the best rrarent for marketing thinnings.

The econanic and biological success of mixed plantations will depend on the availability of adequate financial resources and of skilled staff as well as species suited to the sites, c:anpatible with the other ccmponents and matched to the end uses available.

The aOOve has considered only the effect on returns ariSing fran mixtures in the provision of wood products . Species may be included in mixtures for other values - for instance, for the provision of fodder, fruit or nuts, or for the soil-improVing properties of their leaves or associated nitrogen-fixing bacteria, or for their visual appearance. These are all valid reasons for planting mixtures, rut they are difficult to evaluate because their products are not usually traded in markets.

8. HIN CONCLUSIONS.

Plantations in the tropics and sub-tropics.

Plantations can supplement, but never fully substitute for, the rangeof goods and services provided fruit natural forests. Criticisms arefrequentlymade of plantations on the grounds that they lead to impoverishedecosystems and a decrease in the number of plant and wildlife species.Although plantations could he established for the specific purpose ofconserving genetic resources of one or a few specified tree species, andalthough the reconstruction of ecosystems has been attempted on a limitedscale, most plantations are not established for such purposes and (unless theyhave replaced natural forest on the same site) their benefits should not beevaluateddirectly against the natural forest. It is also important to stressthat the establishment of production plantations, which frequanUy implies theuse of fast-growing, pioneer species, must not preclude reseArdh anddevelopment of a range of other, local, species; and that if an ecosystem ischanged through the establishment of forest plantations (or agriculturalcrops) then care must be taken to conserve elsewhere representative examplesof the local flora and fauna.

Forestry plantations in the tropics and sub-tropics make a greatercontribution to people' s needs for forest products than their relatively smallarea suggests, not just to the supplyof industrial roundwood but also throughthe provision of many other goods and environmental services. The area offorestry plantations is likely to increase considerably, particularly whenestablished outside the government sector by communities and individuals; theuse of tree plantations to sequester carbon to reduce the accumulation ofcarbon dioxide in the atmosphere is also attracting much attention. Theeffect of species composition on sustaining the flow of benefits from theseplantations is of considerable importance.

Mixtures of species in forest plantations may he deliberately created,or theymay develop naturally through the natural regeneration of other woodytree species in otherwise single species plantations. Mixtures cover a widerange of options, from simple even-aged mixtures of two species to severalspecies in a plantation managed as a selection forest. Mixtures are alsotaken to mean the planting of different species in adjacent blocks. Mostplantations are at present planted with a single species, but objections tothis on the grounds that it is environmentally unsound overloOk the manysingle species associations that occur naturally. In fact, the fast-growingspecies best adapted to producing wood products on short rotations arefrequently those typical of early stages in the forest succession in whichthere are few species; they may thus not be naturally adapted to growth inmixtures.

Decline in yields of wood

The evidence for a decline in yields of wood fram single speciesplantations in the second or subsequent rotations appears to be based more ona failure to match species to site than to be due to the pure plantationitself. Nevertheless, nutrients will be lost frum plantations due toharvesting,in particular those grown on short rotations. Permanent SamplePlots will be an important tool in detecting yield decline, but meanwhileforesters should avoid silvicultural practices likely to lead to losses of

6868

8. MIWI CXH:LUSIaIS.

Plantations in the t:rqrl.cs am. sub-t:rqrl.cs.

Plantations can supplement, but never fully substitute for, the range of goods and services provided fran natural forests. Criticisms are frequently llI3.de of plantations on the grounds that they lead to :inp:lverished ecosystans and a decrease in the number of plant and wildlife species. Although plantations could be established for the specific purpose of conserving genetic resources of one or a few specified tree species, and although the reconstruction of ecosystans has been attarpted on a limited scale, rrost plantations are not established for such purposes and (unless they have replaced natural forest on the same site) their benefits should not be evaluated directly against the natural forest. It is also :inp:lrtant to stress that the establislment of production plantations, which frequently iltplies the use of fast-growing, pioneer speCies, ImlSt not preclude research and developrent of a range of other, local, species; and that if an ecosystem is changed through the establishment of forest plantations (or agricultural crops) then care ImlSt be taken to conserve elsewhere representative exarrples of the local flora and fauna.

Forestry plantations in the tropics and sub-tropiCS make a greater contriOOtion to people's needs for forest products than their relatively SllI3.l1 area suggests, not just to the supply of industrial roundwood rut also through the provision of =y other goods and environrrental services. The area of forestry plantations is likely to increase oonsiderably, particularly when established outside the gove:rnrrent sector by ccmnunities and individuals; the use of tree plantations to sequester carbon to reduce the accumulation of carbon dioxide in the atrrosphere is also attracting much attention . The effect of species cullfX"1Cition on sustaining the flCM of benefits fran these plantations is of considerable :inp:lrtance.

Mixtures of species in forest plantatiOns llI3.y be deliberately created, or they llI3.y develop naturally through the natural regeneration of other woody tree species in otheIWise single species plantations . Mixtures oover a wide range of options, fran siltple even-aged mixtures of two species to several species in a plantation llI3.naged as a selection forest. Mixtures are also taken to m=an the planting of different species in adjacent blocks. M:Jst plantations are at present planted with a single species, rut objections to this on the grounds that it is envirOIll1l9Iltally unsound overlook the =y single species associations that occur naturally. In fact, the fast-grCMing species best adapted to producing wood products on short . rotations are frequently those typical of early stages in the forest succession in which there are few species; they llI3.y thus not be naturally adapted to grCMth in mixtures.

Dec] j TV> in yields of wood

The evidence for a decline in yields of wood fran single species plantations in the second or subsequent rotations appears to be based IOC)re on a failure to llI3.tch species to site than to be due to the pure plantation itself. Nevertheless, nutrients will be lost fran plantatiOns due to harvesting, in particular those 9"I"GIIl on short rotations . Pennanent Sarrple Plots will be an :inp:lrtant tool in detecting yield decline, rut meanwhile foresters should avoid silvicultural practices likely to lead to losses of

69

soil or organic matter. Silvicultural practice must also contribute to therecycling of nutrients through rapid litter breakdown.

Importance of site and objectives.

Species must be matched to the site; problems will arise where trees areplanted off-site, There will, however, usually be a range of species that aresilviculturally suited to anyone site; the choice is then determined by theObjectives of management. When objectives can be achieved through extensivemanagement practices, as in the case of watershed management, rehabilitationof degraded sites, amenityplanting and sometimes the production of fodder forlivestodk, it will often bebeneficial to use species which, biologically, areable to grow in mixed stands and which can complement each other in theprovision of a range of goods and environmental services. If, on the otherhand, the objective is high yields of a uniform product, for example for aspecific industrial process, then it is likely that monospecific, shortrotation, intensivelymanaged pioneer species will best satisfy the objectivesof management.

In all plantation projects, however, there will be other objectives andconstraints to the achievement of the main objects of management; suchconstraints should include the production of sustainable yields and themaintenance of site fertility. These secondary objectives or constraints toensure environmental sustainability may lead policies away from single speciesplantations;, for instance, to the creation of mixtures in the broad sensethrough grouping of monospecific plantations, or by rotating crops ofdifferent species, or by undertaking heavy thinnings to encourage thedevelopment of an understorey of shrubs and herbs.

Risk.

A mixture of species often provides an insurance against the risk of atotal loss as a result of some catastrophic event or a dhange in markets ordemand. The use of mixtures for the purpose of reducing overall risk inintensivelymanaged plantations usually implies a reduction in profits becauseof the partial substitution of a valuable species by a less valuable one orbecause of greater management costs. Mbnospecific and, even more so,monoclonal plantations are usually associated with a "high input/high output"policy whidh is also often high risk. The justification for sudh a policydepends to a large extent on the ability of the manager (government,community, individual or company) to evaluate the risk, to allocate resourcesto overcome potential problems and to undertake research to anticipateprdblems. It depends too on the length of the rotation. Successfulmonospecific plantation projects are found in many countries, for example NewZealand, South Africa, some of the Australian states,Brazil, Chile and Congo,but where an organization cannot guarantee continuing resources same risk-spreading is advisable, even if only in the use of mixtures in the broadsense.

Although mixtures have usually been seen as an insurance against risk,examples have been quoted where species diversity has proved ineffective incontrolling a disease, for example Chestnut blight in USA or aothistromablight in P.radiata in East Africa.. It has been argued that mixtures can evenincrease risk from disease by providing an alternate host. There is littleknowledge of the mechanisms by which pests and diseases spre_ad and are

69

soil or organic I113.tter . Silvicultural practice must also contrihlte to the recycling of nutrients through rapid litter b~.

IqIartance of site and objectives.

Species must be I113.tched to the site; problans will arise where trees are planted off-Site, There will, lJa.iever, usually be a range of species that are silviculturally suited to anyone site; the choice is then detennined by the objectives of I113.nagel!EIlt. When objectives can be achieved through extensive I113.nagerrent practices, as in the case of watershed I113.nagerrent, rehabilitation of degraded sites, arrenity planting and saretimes the production of fodder for livestock, it will often be beneficial to use species which, biologically, are able to grc:M in mixed stands and which can cc:rrplerrent each other in the provision of a range of goods and envirormental services. If, on the other hand, the objective is high yields of a unifonn product, for exarrple for a specific industrial process, then it is likely that lOClllospecific, short rotation, intensively I113.naged pioneer species will best satisfy the objectives of I113.nagerrent.

In all plantation projects, lJa.iever, there will be other objectives and constraints to the achieverrent of the I113.in objects of I113.nagerrent; such constraints should include the production of sustainable yields and the I113.intenance of site fertility. These secondary objectives or constraints to ensure environmental sustainability I113.y lead poliCies away fran single species plantations;. for instance, to the creation of mixtures in the broad sense through grouping of lOClllospecific plantations, or by rotating crops of different speCies, or by undertaking heavy thinnings to encourage the developnent of an understorey of shrubs and herbs.

Risk.

A mixture of species often provides an insurance against the risk of a total loss as a result of sare catastrophic event or a change in =kets or demand. The use of mixtures for the purpose of reducing overall risk in intensivelyIll3.nagedplantations usually:iIrq;Jlies a reduction in profits because of the partial substitution of a valuable species by a less valuable one or because of greater I113.nagerrent costs. MJrlospecific and, even rrore so, rronoclonal plantations are usually associated with a "high input/high output" policy which is also often high risk. The justification for such a policy depends to a large extent on the ability of the I113.nager (government, camrunity, individual or cc:rrpany) to evaluate the risk, to allocate resources to overcare potential problans and to undertake research to anticipate problans. It depends too on the length of the rotation. Successful lOClllospecific plantation projects are found in =y countries, for exarrple New zealand, SOuth Africa, sare of the Australian states, Brazil, Chile and Congo, rut where an organization cannot guarantee continuing resources sore risk­spreading is advisable, even if only in the use of mixtures in the broad sense.

Although mixtures have usually been seen as an insurance against risk, exarrples have been quoted where species diversity has proved ineffective in controlling a disease, for exarrple Chestnut blight in USA or Dothist.rr:m3 blight in P.radiata in East Africa. It has been argued that mixtures can even increase risk fran disease by providing an alternate host. There is little knowledge of the mechanisms by which pests and diseases spread and are

70

controlled in a forest ecosystem; the chances that unproven, indiscriminatemixtures will control pests or diseases are small.

Monitoring growth, yields and soil fertility is important, bit themonitoring of fertility is difficult and yield trends may be masked byadvances in tree breeding and in silvicultural techniques and may not bedetected until the next rotation. The need for action to sustain soilfertility-through sound management practices has already been noted, and theuse of mixtures may contribute to this aim.

Synergy.

There are sane documented instances of mixtures enhancing not only-totalyield bit also the yield of specific, valuable components of a crop. InScandinavia this "IlliJUNi species" effect may be small, bit there areindications that the use of nitrogen fixing co-daminant species could resultin increases in yield. Such synergies are worth pursuing, bit the sites onwhich they are achievable are limited and the conditions under which theyoperate have not been well researched in the tropics.

Types of plantations

(a) Industrial Plantations

Reduction of diversity in the production population is an object ofmanagement in order to maximize growth on valuable species and to obtainuniformity for industrial processes. Sane natural ecosystems consist of asingle or a few species, bit in a single species plantation there is anincreased risk of instability, although monospecific plantations maybe easierto treat than polyspecific plantations in the event of attacks by pests ordiseases.

The efficacy of mixtures to control attacks of pests and diseases isvariable and uncertain. The mechanisms involved are often complex and thedegree of mixing required may make it uneconomic to graa a vulnerable species.It is recognizedthat some vaIuabdetropical timbers, notably sanemahoganies,can only be established satisfactorily in shade which helps control attadksby liTiosipyla. Usually shade is best provided by another species and mixedmahogany plantations have proved silviculturally successful in many parts ofthe tropics.

The skills required to manage mixed plantations, particularly mixturesof dominants and co-dominants, are greater than for managing monospecificplantations. 13adlytimed interventions or incompatibility of the species usedmay result in malformation of stems or possibly a natural reversion to amonospecific condition.

Since the products of the final felling of industrial plantations in thetropics are often intended for the export market, mixtures may be economicallymore viable if a nurse or "in-filler" crop can be harvested early in therotation. But this is dependent on there being a market for small size ornon-wood produce from the nurse crop.

Second rotation decline is a real risk on infertile sites and cannot bediscounted on fertile sites. It is controllable by good forestry practicewhich may include temporary or permanent mixtures of species to improve the

70

controlled in a forest ecosystem; the chances that unproven, indiscriminate mixtures will control pests or diseases are small.

Monitoring grcMth, yields and soil fertility is :irrportant, rut the rronitoring of fertility is difficult and yield trends may be masked by advances in tree breeding and in silvicultural techniques and may not be detected until the next rotation. The need for action to sustain soil fertility through sound management practices has already been noted, and the use of mixtures may contrihlte to this aim.

Synezgy.

There are sate docurrented instances of mixtures enhancing not only total yield rut also the yield of specifiC, valuable canponents of a crop. In Scaridi.na.via this ''mixed species" effect may be small, rut there are indications that the use of nitrogen fixing =-daninant species could result in increases in yield. Such synergies are worth pursuing, rut the sites on which they are achievable are limited and the conditions under which they operate have not been well researched in the tropics.

Types of plantations

(a) Industrial Plantations

Reduction of diversity in the production population is an object of management in order to max:irnize grcMth on valuable species and to obtain uniformity for industrial processes. SCIre natural ecosystems consist of a single or a few species, rut in a single species plantation there is an increased risk of instability, although rronospecific plantations may be easier to treat than polyspecific plantations in the event of attacks by pests or diseases.

The efficacy of mixtures to control attacks of pests and diseases is variable and uncertain. The I\'echanisms involved are often a::rrplex and the degree of mixing required may make it uneconanic to grcM a vulnerable species. It is recognized that sane valuable tropical timbers, notably sane mahoganies, can only be established satisfactorily in shade which helps control attacks by Hypsipyla. Usually shade is best provided by another species and mixed mahogany plantations have proved silviculturally successful in many parts of the tropics.

The skills required to manage mixed plantations, particularly mixtures of daninants and =-daninants, are greater than for managing rronospecific plantations. Badly tiIred interventions or ina::rrpatibility of the species used may result in malfonnation of stems or possibly a natural reversion to a rronospecific condition.

Since the products of the final felling of industrial plantations in the tropics are often intended for the export market, mixtures may be econanicall y m::>re viable if a nurse or "in-filler" crop can be harvested early in the rotation. But this is dependent on there being a market for small size or non-wood produce fran the nurse crop.

Second rotation decline is a real risk on infertile sites and cannot be discounted on fertile sites. It is controllable by good forestry practice which may include temporary or permanent mixtures of species to :iIrq?rove the

71

decomposition of litter and thereby promote the recycling of nutrients andincreasing the organic content of the topsoil.

Less intensively managed plantations.

In fuelwood and pole plantations there is usually less need foruniformity of product and there is often greater scope for unmechanizedharvesting and extraction. Therefore the factors that militate againstmixtures in industrial plantations are less pressing and the opportunity toinclude mixtures to reduce risks or to favour soil improvement can be taken.

Fbdder plantations should generally be mixed to give a succession ofleaf forage throughout the year, particularly in the dry season. Windbreaksshould also generally be of several species, to provide shelter at differentlevels and of different densities.

The growing of other woody species in association with the main speciesmay of fer economic advantages; two examples that are quoted are of rattans andof sandalwood.

Plantations for site improvement.

Plantations established with the objective of site improvement -

watershed management, rehabilitation of degraded soils and amenity canfrequently be established as mixtures. The sites often present specialproblems about which little is known and a mixture represents an insuranceagainst failure, though natural succession mayanyway tend towards a limiteddiversity. A knowledge of the natural ecological succession of the site ishelpful.

Conservatica of wildlife

Most large plantations will have one main Objective (such as woodproduction), with other subsidiary objectives or perhaps constraints to themain objective (such as soil conservation, catchment protection or theprovision of direct social benefits). There may often also be objectives ofwildlife conservation.

The maintenance of suitable habitats for the conservation of geneticresources and the production of wildlife species of commercial or subsistencevalue are the main Objectives of wildlife conservation within forestryplantations. The contribution of forestry plantations to those aims can begreatly enhanced by adequate pre-planting planning and design, as well as bythe actual day-to-daymanagement of the plantation. Plantation schemes shouldbe seen within the wider land use context, and within the scheme bufferplantings, corridors, the retention of islands of natural forest within theplantations and incentives to local people can all contribute to wildlifeconservation.

The more the management of a plantation encourages overall plantdiversity and the closer the plantation reseMbles the natural forest thegreater will he the contribution to wildlife conservation. Mixtures of ageclasses and of appropriate species, along with the retention of same naturalforest,will generallypromote this conservation. Generalist large herbivorescan reach high density where there is structural diversity in the plantationor even in young plantations or on clear felled sites.

71

decanposition of litter and thereby prarote the recycling of nutrients and increasing the organic content of the topsoil .

(b) Less intensively managed plantations.

In fuelVA:lOd and pole plantations there is usually less need for unifonnity of product and there is often greater scope for unmechanized harvesting and extraction. Therefore the factors that militate against mixtures in industrial plantations are less pressing and the opportunity to include mixtures to reduce risks or to favour soil improvement can be taken.

FOdder plantations should generally be mixed to give a succession of leaf forage throughout the year, particularly in the dry season . Windbreaks should also generally be of several species, to provide shelter at different levels and of different densities.

The grcwing of other VA:lOdy species in association with the main species may offer econanic advantages; ~ examples that are quoted are of rattans and of sandalVA:lOd.

(c) Plantations for site improvement.

Plantations established with the objective of site improvement -watershed management, rehabilitation of degraded soils and amenity can frequently be established as mixtures. The sites often present special problems about which little is kn~ and a mixture represents an insurance against failure, though natural succession may anyway tend tc::W<lIds a limited diversity. A knowledge of the natural ecological succession of the site is helpful.

Camervation of wildlife

Most large plantations will have one main objective (such as VA:lOd production), with other su1::sidiary objectives or perhaps constraints to the main objective (such as soil conservation, catchment protection or the provision of direct social benefits). There may often also be objectives of wildlife conservation.

The maintenance of suitable habitats for the conservation of genetiC resources and the production of wildlife species of o::mnercial or su1::sistence value are the main objectives of wildlife coriservation within forestry plantations . The contribution of forestry plantations to those aims can be greatly enhanced by adequate pre-planting planning and design, as well as by the actual day-to-daymanagernent of the plantation. Plantation scharies should be seen within the wider land use context, and within the schare buffer plantings, co=idors, the retention of islands of natural forest within the plantations and incentives to local people can all contribute to wildlife conservation .

The IOOre the management of a plantation encourages overall plant diversity and the closer the plantation resanbles the natural forest the greater will be the contribution to wildlife conservation. Mixtures of age classes and of appropriate species, along with the retention of sane natural forest, will generallyprarote this conservation. Generalist large herbivores can reach high density where there is structural diversity in the plantation or even in young plantations or on clear felled sites.

9 . RECOMMENDATIONS .

An exhaustive review of the literature comparing theadvantages and disadvantages of mixed or pure plantations hasbeen made. While there are many references concerned with tnesubject few of them record direct comparisons of plantationscomposed of a single species with those composed of more thanone. This section makes some recommendations for practisingforesters, forest research workers and planners concerned withforestry plantation development in the tropics and sub-tropicsbased upon the evidence that is available as well as upon thosegaps in knowledge of the behaviour of species in pure and mixedassociations.

The objectives of plantations.

It is recommended that plantations are established withspecific objectives in mind in order to be able to evaluate theircosts and benefits fully. It is only under these conditions thatthe choice can be made between single or multiple speciescomposition.

Matching species and management practices to the site.

One of the principal recommendations arising from this studyis of the importance of matching not only species and provenancesbut also management practices to the site to ensure that growthand yield of desired products are sustained in the long term.This recommendation will acquire added weight as plantations areextended in the tropics and sub-tropics onto sites that aremarginal for the growth of the traditional plantation species.

Plantation guidelines, formulated at national and sub-national level and given the status of forest regulations arerecommended in order to implement good forestry practice inplantation development. Such guidelines have been produced, forexample, in Queensland (Kanowski and Savill 1990) and by theInternational Tropical Timber Organization in collaboration withFAO. Guidelines drawing attention to "best practice" in theplanning, establishment and management of plantations have alsobeen prepared by other organizations.

Situations where mixtures are appropriate

There are certain situations where it is recommended thatthe forest manager or planner should consider the use of mixturesof one sort or another in a forest plantation. These include,but are not limited to, the following:

community forests, where more than one species in themixture helps to meet multiple end-uses and acts as an insuranceagainst failure of a single species;

7272

9. RECOKMEHDATIONS.

An exhaustive review of the literature comparing the advantages and disadvantages of mixed or pure plantat ions has been made. While there are many references concerned with tne subject few of them record direct comparisons of plantations composed of a single species with those composed of more than one. This section makes some recommendations for practising foresters, forest research workers and planners concerned with forestry plantation development in the tropics and sub-tropics based upon the evidence that is available as well as upon those gaps in knowledge of the behaviour of species in pure and mixed associations.

The objectives of plantations .

It is recommended that plantations are established with specific objectives in mind in order to be able to evaluate their costs and benefits fully . It is only under these conditions that the choice can be made between single or multiple species composition.

Matching species and management practices to the site.

One of the principal recommendations arising from this study is of the importance of matching not only species and provenances but also management practices to the site to ensure that growth and yield of desired products are sustained in the long term . This recommendation will acquire added weight as plantations are extended in the tropics and sub-tropics onto sites that are marginal for the growth of the traditional plantation species .

Plantation guidelines, formulated at national and sub­national level and given the status of forest regulations are recommended in order to implement good forestry practice in plantation development. Such guidelines have been produced, for example, in Queensland (Kanowski and Savill 1990) and by the International Tropical Timber Organization in collaboration with FAO . Guidelines drawing attention to "best practice" in the planning, establishment and management of plantations have also been prepared by other organizations.

Situations where mixtures are appropriate

There are certain situations where it is recommended that the "forest manager or planner should cons ider the use of mixtures of one sort or another in a forest plantation. These include, but are not limited to, the following:

communi ty forests, where more than one species in the mixture helps to meet multiple end-uses and acts as an insurance against failure of a single species;

73

firebreaks in pure plantations, either in lines to createa discontinuity or in intimate mixture to introduce lessflammable fuel;

nurse crops, especially for reduction of insect attack asin the mixture of Nauclea diderichii with Meliaceae to reduce theincidence of Hypsipila;

areas in which wildlife conservation is a stated objective,as distinct from action to minimise the impact of plantations onwildlife, through the creation of mixed plantations to establisha suitable habitat for wildlife.

Also, although different from a mixture of tree species:

encouragement of a shrub and herb layer, through regularthinning and avoidance of overstocking; in fact, the goodforestry practice recommended above;

clonal forestry, where there should be a mixture of blocksof clones in the annual plantation area and the regularintroduction of new clones arising from a continuing breedingprogramme of sexual reproduction (including hybridisation).

Growth monitoring.

There is little information in the tropics on the growth ofpure stands on a full range of sites; the information on mixedstands is negligible. It is recommended that a network ofPermanent Sample Plots in forest plantations should beestablished by countries with significant forest plantationprogrammes (including community tree planting). These plotsshould be maintained over several rotations, and are required inall major species; they must be established on a full range ofpotential planting sites. The Permanent Sample Plots should bebacked by other growth studies including plots on which not onlywill the same species be re-established in successive rotations,but in addition the tree seed will be obtained from the same seedsource as that of the original plantation, to minimiseexperimental error. The short rotations on which many speciesare managed in the tropics make this practicable. The plots willalso be useful for deriving yield models.

Research.

There is an almost complete lack of experimental evidenceon the benefits and constraints to the establishment, growth andmarketing of forest plantations consisting of mixtures or singlespecies in the tropics and sub-tropics. It is recommended thatnational, regional and international research institutionsinclude such investigations in their programmes of plantationresearch. Some examples are given below:

73

firebreaks in pure plantations, either in lines to create a discontinuity or in intimate mixture to introduce less flammable fuel;

nurse crops, especially for reduction of insect attack as in the mixture of Nauclea diderichii with Meliaceae to reduce the incidence of Hypsipila;

areas in which wildlife conservation is a stated objective, as distinct from action to minimise the impact of plantations on wildlife, through the creation of mixed plantations to establish a suitable habitat for wildlife.

Also, although different from a mixture of tree species:

encouragement of a shrub and herb layer, thinning and avoidance of overstocking; in forestry practice recommended above;

through regular fact, the good

clonal forestry, where there should be a mixture of blocks of clones in the annual plantation area and the regular introduction of new clones arising from a continuing breeding programme of sexual reproduction (including hybridisation).

Growth monitoring.

There is little information in the tropics on the growth of pure stands on a full range of sites; the information on mixed stands is negligible. It is recommended that a network of Permanent Sample Plots in forest plantations should be established by countries with significant forest plantation programmes (including community tree planting). These plots should be maintained over several rotations, and are reqUired in all major species; they must be established on a full range of potential planting sites. The Permanent Sample Plots should be backed by other growth studies including plots on which not only will the same species be re-established in successive rotations, but in addition the tree seed will be obtained from the same seed source as that of the original plantation, to minimise experimental error. The short rotations on which many species are managed in the tropics make this practicable. The plots will also be useful for deriving yield models.

Research.

There is an almost complete lack of experimental evidence on the benefits and constraints to the establishment, growth and marketing of forest plantations conSisting of mixtures or single species in the tropics and sub-tropics. It is recommended that national, regional and international research institutions include such investigations in their programmes of plantation research. Some examples are given below:

74

effect on long-term soil fertility and yield, especially thepotential of nitrogen-fixing species to increase yields inmixtures and the effect of harvesting on soil nutrient status andthe yield of subsequent rotations;

identification of new species and provenances of trees andshrubs for use in mixtures, related not just to their yields ofwood but also to their non-wood products and other benefits.Research may be needed to develop markets for the products oflesser-known species;

compatibility of different species, whether trees or shrubs,when grown in mixture, particularly the existence of synergybetween species and methods of management of mixtures;

the potential of mixtures for forest protection, whetherfrom insects, disease or fire, and particularly the mechanismsby which diseases and insect pests spread in forest ecosystemsand the processes by which they are controlled naturally.

Economic analysis.

While data on the economics of plantations in the tropicsin general is scarce, there is virtually no information on theeconomics of mixed plantations. It is possible that cost andrevenue data are available, but there is no evidence that suchfigures have been collated and analyzed. It is recommended thatdata on the costs and benefits of plantation programmes arecollected in such a way that would allow reliable comparisonbetween mixed and pure plantations, especially over severalrotations. Such data should attempt to quantify other benefitsarising from the plantations in addition to wood products.

Most of the emphasis in this study has been on thebiological effects of mixed and pure plantations but there maybe important social or cultural reasons for the inclusion ofspecies other than those traditionally planted for wood productsin plantations. It is recommended that consideration is givento these factors when evaluating the options for the speciescomposition of plantations.

74

effect on long-term soil fertility and yield, especially the potential of nitrogen-fixing species to increase yields in mixtures and the effect of harvesting on soil nutrient status and the yield of subsequent rotations;

identification of new species and provenances of trees and shrubs for use in mixtures, related not just to their yields of wood but also to their non-wood products and other benefits. Research may be needed to develop markets for the products of lesser-known species;

compatibility of different species, whether trees or shrubs, when grown in mixture, particularly the existence of synergy between species and methods of management of mixtures;

the potential of mixtures for forest protection, whether from insects, disease or fire, and particularly the mechanisms by which diseases and insect pests spread in forest ecosystems and the processes by which they are controlled naturally.

Economic analysis.

While data on the economics of plantations in the tropics in general is scarce, there is virtually no information on the economics of mixed plantations. It is possible that cost and revenue data are available, but there is no evidence that such figures have been collated and analyzed. It is recommended that data on the costs and benefits of plantation programmes are collected in such a way that would allow reliable comparison between mixed and pure plantations, especially over several rotations. Such data should attempt to quantify other benefits arising from the plantations in addition to wood, products.

Most of the emphasis in this study has been on the biological effects of mixed and pure plantations but there may be important social or cultural reasons for the inclusion of species other than those traditionally planted for wood products in plantations. It is recommended that consideration is given to these factors when evaluating the options for the species composition of plantations.

75

APPENDIX 1

ANNOTATED BIBLIOGRAPHY

These references are far from comprehensive; the spread of subjectswhich touch on mixed planting is very wide. The notes only refer to aspectsof the publication that appear to he of relevance to mixed planting.

Adlard, P.G. 1978. Tropical forests - comparisons and contrasts. In: Theecology of even-aged forest plantations. Proceedings of the meeting ofDivision I, IUFRO, Edinburgh, Sept. 1978. Institute of TerrestrialEcology, Cambridge (UK), 1979.The tropics: Management. SoilsNet primary production in a rain forest may be used for maintaining adynamic equilibrium. Nitrogen fixers may be particularly important inthese forests. High temperatures and intensive rainfalls increaseleaching in the tropics. Fertilization is costly and may cause leachingand may damage nitrogenous bacteria and mycorrhizae.

Adlard, P.G., 1990. Procedures for Mbnitoring Tree Growth and SiteChange. Tropical Forestry Papers 23, Oxford Forestry Institute (UK).General: Management, ResearchA,manual for designing and setting out Permanent Sample Plots.

Agarwal, S.C., Chinnamani, S. and Rege, N.D. 1961. Mixed plantations foreffective soil conservation in the Nilgiris. Indian Forester 87 (1):26-33India: Soils. ManagementNatural regeneration of Acacia molissima under Eucalyptus globulusseems to work well. The protective value of the mixture is greater thaneither alone.

Agestam, E. 1991. Blandskogens produktion. (The production of mixedstands). Skog och FoLskning 2/91: 44-51.Scandinavia: Yield.A review of mixtures. Despite the theoretical advantages of mixing, itis difficult to demonstrate significant practical gains.

Alphen de Veer, F.J. van 1950. Loofhout in Pinus-culturen. (Broadleavedspecies in pine plantations.) Unpublished. Noted in Indonesian ForestryAbstracts, PUDOC, Wageningen, 1982. Abstract 590Indonesia: ManagementMbnocultures are warned against. Mixing with broadleaved species isrecommended to avoid the hazards.

Alphen de Veer, F. J. van 1950. Loofhoutmenging Pinus Takengon. (MixingPinus with broadleaved species in Takengon, Aceh.) Handwritten. Notedin Indonesian Forestry Abstracts, PUDOC, Wageningen, 1982. Abstract597Indonesia: ManagementWide spacing and an understorey of broadleaved species is recommended.Broadleaves can be planted after the first thinning. A number ofsuitable species in listed.

Alrasyid, H. 1985. Percobaan penanarnan kayu eboni (Diospyros celebica) diLaNa tekagan jati di Jawa. (The plantation trial of ebony wood(Dicspyros celebica) under teak forest stand in Java.) Buletin Pene-litian HUtan NO. 464: 23-37.Indonesia: Management

75

APPENDIX 1

ANNOl'ATED BIBLIOGRAPHY

These references are far fran canprehensive; the spread of subjects which touch on mixed planting is very wide. The notes only refer to aspects of the publication that appear to be of relevance to mixed planting.

l\dl.ard, P.G. 1978. Tropical forests - canparisons and contrasts. In: The ecology of even-aged forest plantations. Proceedings of the meeting of Division I, IUFRO, Edinburgh, Sept. 1978 . Institute of Terrestrial Ecology, Cambridge (UK), 1979 . The tropics: Management . Soils Net primary prodUction in a rain forest may be used for maintaining a dynamic equilibrium. Nitrogen fixers may be particularly important in these forests . High temperatures and intensive rainfalls increase leaching in the tropics. Fertilization is costly and may cause leaching and may damage nitrogenous bacteria and mycorrhizae.

l\dl.ard, P.G., 1990 . Procedures for MJnitoring Tree GrO.-lth and Site Change . Tropical Forestry Papers 23, Oxford Forestry Institute (UK). General : Management, Research A manual for designing and setting out Permanent Sample Plots.

Agarwal, S.C., Chinnamani, s. and Rege, N. D. 1961. Mixed plantatiOns for effective soil conservation in the Nilgiris. Indian Forester 87 (1): 26-33 India: Soils. Management Natural regeneration of Acacia molissima under Eucalyptus globulus seems to work well. The protective value of the mixture is greater than either alone .

Agestam, E. 1991. Blandskogens produktion. (The production of mixed stands) . Skog och Forskning 2/91: 44-5l. Scandinavia : Yield. A review of mixtures. Despite the theoretical advantages of mixing, it is difficult to demonstrate significant practical gains.

Alphen de Veer, F.J. van 1950. Loofhout in pinus-culturen . (Broadleaved species in pine plantations . ) Unpublished. Noted in Indonesian Forestry Abstracts, PUIXlC, Wageningen, 1982 . Abstract" 590 Indonesia: Management MJnocultures are warned against . Mixing with broadleaved species is recommended to avoid the hazards.

Alphen de Veer, F.J. van 1950. LoofhoutmeIJging Pinus Takengon. (Mixing Pinus with broadleaved species in Takengon, Aceh.) Handwritten. Noted in Indonesian Forestry Abstracts, PUIXlC, Wageningen, 1982. Abstract 597. Indonesia : Management Wide spacing and an understorey of broadleaved species is reccmmended. Broadleaves can be planted after the first thinning. A number of suitable species in listed.

Alrasyid, H. 1985. Percobaan penanaman kayu eboni (Diospyros celebica) di rewa tekagan jati di Jawa . (The plantation trial of ebony wcod (Diospyros celebica) under teak forest stand in Java . ) Buletin Pene­litian Rutan No. 464: 23-37 . Indonesia : Management

76

A trial to underplant ebony in teak plantations has been made. It isconcluded that the height growth of ebony under teak in a monsoonalclimate is low.

Althen, F.W. von 1968. Incompatibility of bladk walnut and red pine.Bimonthly Research Notes, Department of Forestry, Canada. 2.Canada: Management. EnvironmentalAn experiment to establish the effects of juglone, a substance excretedby walnut roots, on red pine. Results suggest that the effects are verybad, sometimes lethal.

Althen, F.W. von 1974. Successful establishment of sugar maple in a Scotspine plantation. Information Report, Great Lakes Forest Research Cen-tre, Canada, No. O-X-208.Canada: ManagementSugar maple grows poorly on abandoned farmland in pure stands. Attemptsat planting it under Pinus sylvestris have shown promising results.

Ananthia'.Padmanabha,H.S., NAgareni,H.C. and Rai,S.N. 1988. Influence of hostplants on growth of Sandal. Myforest 24 (2): 154-160.India: ManagementSuitable hosts for Santalum album are suggested. Suggestions aresupported by pot culture and leaf analysis for Mg, N, P and K.

Anderson, M.L. 1953. Spaced group planting. Unasylva 7: 55-63,Tropics: ManagementDescribes a system of group planting.

Andexsson, S.O. 1985. Treatment of young mixed stands with birches andconifers. In: Broadleaves in Boreal Silviculture - An Obstacle or anAsset? Swedish University of AsjLicultural Sciences, Department ofSilviculture, Report No. 14.Sweden: ManagementThe advantages of retaining broadleaves as nurse stands are consideredto outweigh the losses of increment.

Andrasko, K. 1990. Climate change and global forests: current knowledgeof potential effects, adaptation and mitigation options. FO:MISC/90/7,FAO, Rome. pp 60.General: ClimateA, review of factors causing climatic change and the effect on forests.

Anon 1974. Supplementary planting in logged beech forest. What's New inForest Research 10. Forest Research Institute, Rotorua, New Zealand.New Zealand: Management.Eucalyptus is used in Podocarpus-Nothofagus forest where rimu(.Dacrydium cupressinum) grows in mixture with the beech.

Applegate, G.B. 1991. Personal communication.Applegate, G.B. and Bragg, A.L. 1988. Agroforestry tree spedies for north

Queensland. Paper presented at Conference on Reforestation on the NorthCoast of New South Wales, Queensland Forest Department.Australia: ManagementA comparison of Tacna australiensis, pure or in mixture with Grevillearobusta. Best results were achieved when pure or under a one yearnurse. It is important to thin out the nurse.

Applegate, G.B. and Gilmour, D.A. 1987. Operational Experiences in ForestManagement Development in the Hills of Nepal. International Centre forIntegrated Mbuntain Development (ICIMOD) Occasional Paper No.6,Kathmandu. pp 40.Nepal: Management, YieldA forest classification and management options, depending on initialstand to be nsed in village level work plans.

76

A trial to underplant ebony in teak plantations has been made. It is concluded that the height growth of ebony under teak in a monsoonal climate is low.

Althen, F.W. von 1968. Incanpatibilityof black walnut and red pine. Bimonthly Research Notes, Department of Forestry, Canada. 2. Canada: Management. Environmental An experiment to establish the effects of juglone, a substance excreted by walnut roots, on red pine. Results suggest that the effects are very bad, sanet:ilnes lethal.

Althen, F.W. von 1974. Successful establishment of sugar maple in a Scots pine plantation. InfoIrnation Report, Great Lakes Forest Research Cen­tre, Canada, No. 0-X-20S. Canada: Management Sugar maple grows poorly on abandoned fannland in pure stands. Attempts at planting it under Pinus sylvestris have shown premising results.

Ananthia Padnanalila,H.S., Nagareni,H.C. and Rai,S.N. 1988. Influence of host plants on growth of Sandal. Myforest 24 (2): 154-160. India: Management Suitable hosts for Santall.1Ill album are suggested. Suggestions are supported by pot culture and leaf analysis for Mg, N, P and K.

Anderson, M.L. 1953. Spaced group planting. Unasylva 7: 55-63. Tropics: Management Describes a system of group planting.

Andersson, S.O. 1985. Treatment of young mixed stands with birches and conifers. In: Broadleaves in Boreal Silviculture - An Obstacle or an Asset? SWedish University of Agricultural Sciences, Department of Silviculture, Report No. 14. SWeden: Management The advantages of retaining broadleaves as nurse stands are considered to outweigh the losses of increment.

Andrasko, K. 1990. Climate change and global forests: =ent knowledge of potential effects, adaptation and mitigation options. FO:MISC/90/7, FAD, Rare. pp 60. General: Climate A review of factors causing climatic change and the effect on forests.

Anon 1974. Supplementary planting in logged beech forest. What's New in Forest Research 10. Forest Research Institute, Rotorua, New zealand. New zealand: Management. Eucalyptus is used in Podocarpus-Nothofagus forest where rimu (Dacrydil.1Ill cupressinl.1Ill) grows in mixture with the beech.

Af,plegate, G.B. 1991. Personal carmunication. Af,plegate, G.B. and Bragg, A.L. 1988. Agroforestry tree species for north

Oleensland. Paper presented at Conference on Reforestation on the North Coast of New South Wales, Oleensland Forest Department. Australia: Management A <=nparison of 'lbona australiensis, pure or in mixture with Grevillea rolxlsta. Best results were achieved when pure or under a one year nurse. It is :important to thin out the nurse.

Af,plegate, G.B. and Gi 1 nX"lI]r , D.A. 1987. Operational Experiences in Forest Management Developnent in the Hills of Nepal. International Centre for Integrated M:Juntain Developnent (ICIMJD) Occasional Paper No.6, Kathmandu. pp 40. Nepal: Management, Yield A forest classification and management options, depending on initial stand to be used in Village level work plans.

77

Applegate,G.B. andGilmour, D.A. 1988.Biomass andproductivity estimates forcommunity forest management: a case study from the hills of Nepal - I.Biomass and productivity of Chir pine (Timis roxburgtii Sargent)plantations. Biomass 17: 115-136.Nepal: YieldPresents regressions for predicting site class= from internode lengthand for predicting stem weight, branch weight and foliage weight fromdbh for Chir pine.

Applegate, G.B. et al 1990a. Sandalwood in the Pacific: a state-of-knowledge synthesis and summary from the April 1990 symposium. InProceedings of the Symposium on Sandalwood in the Pacific, April 1990,Honolulu,Hawaii. US Department of Agriculture, Forest Service, GeneralTechnical Report PSW-122. pp 1-11.Tropics: Management, Ecology, UtilisationA resume of the papers presented in the symposium.

Applegate, G.B., Davis, A.G.W. and Annable, P.A. 1990b. ManagingSandalwood for conservation in North Queensland. In Proceedings of theSymposium on Sandalwood in the Pacific, April 1990, Honolulu, Hawaii,US Department of Agriculture, Forest Service, General Technical ReportPSW-122. pp 12-18.Australia: ManagementA general description of Sandalwood in North Queensland.

Aracruz Celulose S.A. 1988. Technology, Social Progress and theEnvironment. Leaflet describing the company's activities.Brazil: Management20% of the area under native forests. Fruit trees being planted toencourage birds as predators.

Aubreville, A. 1953. Une visite aux fdantaticns dé limbo du Atyen-Congo.(A visit to the limbo plantations in central Congo.) Bois et Forêts desTropiques 27: 3-8.Congo: ManagementExperiments have shown that Terminalia supérta can he planted in widelyspaced strips with a comparatively l1 number of seedlings per hectare,and still produce high grade timber.

Auclair, D. 1978. La sylviculture dé fdréts m6langees. Etudebiblipgraphique. (The silviculture of mixed forests. A review of theliterature.) Document Centre de Recherches Forestières d'Orléans No.78/30.

Review: ManagementA review of literature concerning the silviculture of mixed stands.

Babar, L.I. and EWel, J.J. 1989. Decanposicion del follaje en diveiscsecosistemas sucesionales tropicales. (Decomposition of foliage insuccessional tropical ecosystems.) Biotropica 21 (1): 21-29.Costa Rica: SoilsCbrdia alliodora leaves in a pure plantation decomposed slowly (22%mass and <50% of all elements, except P and K, in 15 weeks as against50% of mass and elements, except N and S, in 6 weeks in a simulatedspecies-rich successional stand).

Bakhoven, A-C. 1930. VUl-drijf en dikkingshout in wildhoutbergculturen,dan wei, de in de Lergwildhoutbergrulturen in te brengen houtscortenvor blijvend ondertestand en ondergroei. (Auxiliary, nursing and soilcovering tree species to mix in non-teak plantations in the mountains,or, to form a permanent understorey tree layer and undergrowth.)Tectona 23: 558-569, 569-581. Noted in Indonesian Forestry Abstracts,PUDOC, Wageningen, 1982. Abstract 591.Indonesia: Management. Soils

77

AWlegate, G.B. andGi1mrur, D.A. 1988. Bianass and productivity estilPates for ccmnunity forest management: a case study fran the hills of Nepal - 1. Bianass and productivity of Chir pine (Pinus roxburghii Sargent) plantations. Bianass 17: 115-136. Nepal: Yield Presents regressions for predicting site class(20) fran internode length and for predicting stem weight, branch weight and foliage weight fran dbh for Chir pine.

AWlegate, G.B. et al 1990a. Sandalwood in the Pacific: a state-of­kn=ledge synthesis and surrrnary fran the April 1990 symposium. In Proceedings of the Symposium on Sandalwocxi in the Pacific, April 1990, Honolulu, Hawaii. US Departrrent of Agriculture, Forest Service, General Technical Report PSW-122. pp 1-11 . Tropics: Management, Ecology, Utilisation A resume of the papers presented in the symposium.

AWlegate, G.B., Davis, A.G.W. and Annable, P.A. 1990b. Managing Sandalwocxi for conservation in North QJeensland. In Proceedings of the Symposium on Sandalwocxi in the Pacific, April 1990, Honolulu, Hawaii. US Departrrent of Agriculture, Forest Service, General Technical Report PSW-122. pp 12-18. Australia: Management A general description of Sandalwood in North QJeensland .

Aracruz Celulose S.A. 1988. Technology, Social Progress and the Environment. Leaflet describing the carnpany's activities. Brazil: Management 20% of the area under native forests. Fruit trees being planted to enoourage birds as predators.

Aubreville, A. 1953. lme visite aux plantations de limbo du M:Jyen-Congo. (A visit to the lirobo plantations in central Congo.) Bois et Forets des Tropiques 27: 3-8. Congo: Management Experiments have shown that Tezminalia superba can be planted in widely spaced strips with a canpa.ratively 1= nlxnber of seedlings per hectare, and still produce high grade timber.

Anclajr, D. 1978. La sylviculture de forets melangees. Etude bibliographique. (The silviculture of mixed forests. A review of the

. literature . ) Document Centre de Recherches Forestieres d'Orleans No . 78/30 . Review: Management A review of literature ooncerning the silviculture of mixed stands .

Babhar , L.I. and :Diel., J.J. 1989. Decanposicion del follaje en diversos ecosistemas sucesionales tropicales. (Decanposition of foliage in successional tropical eoosystems.) Biotropica 21 (1): 21-29. Costa Rica: Soils Cordia alliodora leaves in a pure plantation decanposed sl=ly (22% mass and <50% of all elements, except P and K, in 15 weeks as against 50% of mass and elements, except N and S, in 6 weeks in a simulated species-rich successional stand).

Bakhoven, A.C . 1930. Vul-drijf en dikkingshout in wildhoutbergculturen, dan wel, de in de bergwildhoutbergculturen in te brengen houtsoorten vor blijvend onderbestand en ondergroei. (Auxiliary, nursing and soil oovering tree species to mix in non-teak plantations in the lOCluntains, or, to fonn a pennanent understorey tree layer and undergrCMth . ) Tectona 23: 558-569, 569-581. Noted in Indonesian Forestry Abstracts, PUIXlC, Wageningen, 1982. Abstract 591. Indonesia: Management. Soils

78

Silvicultural guidelines for establishing vertirally closed mixedplantations, considered superior from the hydrological point of vi.

Ball, J.B. 1979. Plantations. Technical Report No. 3, Forestry Des.eiciment

Project, Nigeria. FAO, Rome.Nigeria: Mixtures of Nauclea diderichii with NkliaceaeGrowth models and calculation of internal rate of return.

Bandara, P.D.M.G.D. 1990. Insects and diseases of forest plantations inSri Lanka. In Pests and Diseases of Forest Plantations. HUtacharen, C.,MacDicken, K.G., Ivory, M.H. and Nair, K.S.S. eds. FAD Regional Officefor Asia and the Pacific, Bangkok.Sri Lanka: Pests and diseasesNotes pest and diseases of forest plantations and lists areas ofplantations by species (total 180,000 ha).

Barnes, R.D. 1991. Personal communication.Barnes, R.D. and MulLin, L.J. 1976. Selection of forest tree species in

Rhodesia. South African Forestry Journal 98: 16-19.Southern Africa: Management. EnvironmentalFailures in tree plantations in southern Africa can often he attributedto planting off-site.

Basu, B.K. and Aparajita, M. 1987. Effect of Eucalyptus monocultures onthe soils of southwest Bengal, MUdnapore district, India.India: SoilsSoils analysed under three hybrid Eucalyptus plantations (ages 14, 10and 4 - dbh 19.1, 9.5, 6.8 cm). pH increased from 5.2 to 5.7 withincreasing age; organic content increased (result of fire protection),also N, exchangeable Ca and K and total MgO and K20.

Bateman, I. 1991. Placing money values on the unpriced benefits offorestry. Quarterly Journal of Forestry (UK) 85 (3): 152-165.UK: EconomicsCost Benefit Analysis of the UK Forestry Commission.

Bates, A. L. and Thor, E. 1970. Mixed-species plantations: composition andgrowth as related to soil/site characteristics. Journal of Forestry 68(4): 234-236.USA: YieldPure Pinus echinata was compared to mixtures with Pinus strobus andLiriodendron tulipiféra in 25 year old stands. There were no signs ofincreased growth in the mixtures.

Becking, J. H. 1928. Le djaticultur op Ja va. Een verlijkend onderzoek naarde uitkomsten van veischillende verjcngingsmethoden van den djati opJava. (The cultivation of teak in Java. A comparative investigationinto the results of different methods of teak regeneration in Java.)Meded, P.v.b.H. 22, Thesis, Agricultural University, the Netherlands.Noted in Indonesian Forestry Abstracts, PUDOC, Wageningen, 1982.

Abstract 714.Indonesia: ManagementThe taungya system for regenerating teak is compared to regenerationfrom coppice. Best results are achieved with taungya with interplantingof Leucaena.

Bell, T.I.W. 1973. Erosion in the Trinidad teak plantations. CommonwealthForestry Review 52 (3): 223-233.Trinidad: Soils. ManagementComparative measurements of soil losses between 10 and 13 year old teakplantations and natural forest showed a greater soil loss under teak byfactors ranging from 2.5 to 9. Until 1919 teak was raised in mixturesin Trinidad.

78

Silvicultural guidelines for establishing vertically closed mixed plantations, considered superior fran the hydrological point of view.

Ball, J .B. 1979. Plantations. Tectmical Report No.3, Forestry IB.elq:nent Project, Nigeria . FAD, Rane. Nigeria: Mixtures of Nauclea diderichii with Meliaceae Growth models and calculation of internal rate of return.

Bandara, P.D.H.G.D. 1990. Insects and diseases of forest plantatiOns in Sri Lanka. In Pests and Diseases of Forest Plantations. Hutacharen, C., MacDicken, K.G., Ivory, M.H. and Nair, K.S.S. eds. FAD Regional Offioe for Asia and the PacifiC, Bangkok. Sri Lanka: Pests and diseases Notes pest and diseases of forest plantations and lists areas of plantations by species (total 180,000 hal.

Barnes, R.D. 1991. Personal carmunication. Barnes, R.D. and !t.1l.l.in, L.J. 1976. Selection of forest tree species in

Rhodesia. South African Forestry Journal 98: 16-19 . Southern Africa: Management. Environmental Failures in tree plantations in southern Africa can often be attributed to planting off-site.

Basu, B.X. and Aparajita, H. 1987. Effect of Eucalyptus IlIOnocultures on the soils of southwest Bengal, Mudnapore district, India. India: Soils Soils analysed under three hybrid Eucalyptus plantatiOns (ages 14, 10 and 4 - dbh 19.1, 9.5, 6.8 an). pH increased fran 5.2 to 5 . 7 with increasing age; organic content increased (result of fire protection), also N, exchangeable Ca and K and total MgO and Kp.

Bateman, 1. 1991. Placing IlIOney values on the unpriced benefits of forestry. Quarterly Journal of Forestry (UK) 85 (3): 152-165. UK: Econanics Cost Benefit Analysis of the UK Forestry Commission.

Bates, A.L. and Tbor, E. 1970. Mixed-species plantations: canposition and growth as related to soil/site characteristics. Journal of Forestry 68 (4): 234-236. USA: Yield Pure Pinus echinata was c:anpared to mixtures with Pinus strobus and Liriodendron tulipifera in 25 year old stands. There were no signs of increased grCMth in the mixtures.

Becking, J.H. 1928 . De djaticultur op Java. Een verlijkend onde=oek naar de uitkansten van verschillende verjongingsmethoden van den djati op Java. (The cultivation of teak in Java. A c:anparative investigation into the results of different methods of teak regeneration in Java.) Meded. P.v.b.H. 22, TheSiS, Agricultural University, the Netherlands. Noted in Indonesian Forestry Abstracts, PUlXlC, Wageningen, 1982 . Abstract 714. Indonesia: Management The taungya system for regenerating teak is canpared to regeneration

. fran coppioe . Best results are achieved with taungya with interplanting of Leucaena.

Bell, T.1.W. 1973. Erosion in the Trinidad teak plantations. Ccmnonwealth Forestry Review 52 (3): 223-233. Trinidad: Soils . Management Canparative measurements of soil losses between 10 and 13 year old teak plantatiOns and natural forest shONed a greater soil loss under teak by factors ranging fran 2.5 to 9 . Until 1919 teak was raised in mixtures in Trinidad.

79

Benites, J.R. 1990. Agroforestry systems with potential for acid soils ofthe humid tropics of Latin America and the Caribbean. Forest Ecologyand Management 36: 81-101.South America and Caribbean: SoilsGMelina artorea and sane other species have a great Ability to increasetop soil Ca and Mg. But exchangeable K may decrease to very low levelsand trigger deficiencies.

Bhatia, N. and Promila Rapear. 1984. Neighbour interactionsbetween Leucaena leucocephala and Acacia nilotica in Punjab. LeucaenaResearch Reports 5: 18-19.India: YieldL. leucocephala and A. nilotica have been mixed at different levels.Observations during the first 30 veeRs suggest that this mixture is

Persson, E., Uppsala, Sweden.Tanzania: Management, Ecology.Describes the invasion of natural forests by exotics and the stepsneeded to rehabilitate the forests.

Binkley, D. 1983. Ecosystem production in Douglas-fir plantations:interaction of red alder and site fertility. Forest Ecology andManagement 5 (3): 215-227.USA: SoilsOn a site deficient in N, red alder increased Douglas fir mean dbh butnot b.a., total biomass (including alder) gave 2.5-fold increase. Therewas an increase in foliar N. On the N-rich site red alder caused areduction in dbh and b.a. of Douglas fir.

Binkley, D. 1984. Importance of size-density relationship in mixed standsof Douglas fir and red alder. Forest Ecology and Management 9 (2): 80-85

Canada: Yield. SoilsPairs of Douglas fir and Douglas fir/red alder plots were compared.Mbrtality was higher for mixed stands on fertile sites. It seems thatunderutilized resources are available for the alder on infertile sites.

Binkley, D. 1990. Mixtures of N2-fixing and non-N2-fixing tree species.In Ecology of Mixed Stands of Trees. British Ecological Society andIUFRO Div S2.01 Symposium.Temperate forests: SoilsEffects can only be expected on N-deficient sites where the N-fixingtrees are dominant or co-dominant. Increased growth may give rise toincreased nutrient demands. Then, the rate of nutrient cycling may notbe enough for maintaining the growth rate.

Binkley, D. and Greene, S. 1983. Production in mixtures of conifers andred alder: the importance of site fertility and stand age. GeneralTechnical Report, Pacific Northwest Forest and Range ExperimentStation, US Dept. of Agriculture Forest Service 163: 112-117.USA: SoilsOn infertile sites mixed alder/conifer stands increased rates ofecosystem production. Gains in conifer production occurred after age30. On fertile sites mixed stand productivity did not exceed that ofpure stands and conifer production was impaired.

Birot, Y. 1991 Boisement et reboisement. Position paper, Theme 13, 10thWorld Forestry Congress, Paris, 1991. Proceedings Vol. 5: 9-19.Global: General survey including examples of the use of mixtures.

very promising.Binggeli, P. and Hamilton, A.C. 1990. Tree species invasion and

sustainable forestry in the East Usambaras. In Research forConservation of Tanzanian Catchment Forests. ed Hedberg, I. and

79

Benites, J.R. 1990. Agroforestry systems with potential for acid soils of the humid tropics of Latin America and the Caribbean. Forest Eoology and Management 36: 81-101. South America and Caribbean: Soils GrElina aroorea and sane other species have a great ability to increase top soil ca and Mg. But exchangeable K may decrease to very lCM levels and trigger deficiencies.

Bhatia, N. and Prani.l.a Kapoor. 1984. Neighbour interactions between Leucaena leucocephala and Acacia nilotica in Punjab. IBucaena Research Reports 5 : 18-19. India: Yield L. leucocephala and A. nilotica have been mixed at different levels. Observations during the first 30 weeks suggest that this mixture is very pranising.

Binggeli, P. and Hamilton, A.C. 1990. sustainable forestry in the East Conservation of Tanzanian catchrrent Persson, E., Uppsala, SWeden. Tanzania: Management; Eoology.

Tree species invasion Usarnbaras. In Research Forests. ed Hedberg, I .

and for and

Describes the invasion of natural forests by exotics and the steps needed to rehabilitate the forests.

Binkley, D. 1983. Ecosystem production in Douglas-fir plantations: interaction of red alder and site fertility. Forest Eoology and Management 5 (3): 215-227. USA: Soils On a site deficient in N, red alder increased Douglas fir mean dbh but not b. a., total biarass (including alder) gave 2. 5-fold increase. There was an increase in foliar N. On the N-rich site red alder caused a reduction in dbh and b .a. of Douglas fir.

Binkley, D. 1984. Importance of size-density relationship in mixed stands of Douglas fir and red alder. Forest Eoology and Management 9 (2): 80-85 canada: Yield . Soils Pairs of Douglas fir and Douglas fir/red alder plots were canpared. M::lrtality was higher for mixed stands on fertile sites. It seems that underutilized resources are available for the alder on infertile sites.

Binkley, D. 1990. Mixtures of N2-fixing and non-N

2-fixing tree species .

In Eoology of Mixed stands of Trees. British Ecological Society and IUFRO Div S2.01 Symposium. Temperate forests: Soils Effects can only be expected on N-deficient sites where the N-fixing trees are daninant or oo-daninant. Increased grCMth may give rise to increased nutrient demands. Then, the rate of nutrient cycling may not be enough for maintaining the grCMth rate.

Binkley, D. and Greene, S. 1983. Production in mixtures of conifers and red alder: the importance of site fertility and stand age. General Technical Report, Pacific Northwest Forest and Range Experiment Station, US Dept. of Agriculture Forest Service 163: 112-117 . USA: Soils On infertile sites mixed alder/oonifer stands increased rates of ecosystem production . Gains in oonifer production occurred after age 30. On fertile sites mixed stand productivity did not exoeed that of pure stands and conifer production was impaired.

BiIot, Y. 1991 Boisement et reboisement. Position paper, Theme 13, 10th World Forestry Congress, Paris, 1991. Proceedings Vol. 5: 9-19. Global: General survey including examples of the use of mixtures.

80

Bjorkdahl, G. and Eriksson, EL 1989 Effects of crown decline on incrementin Norway spruce (Picea abies (L.) KUnst.) in southern Sweden. Medd.Norsk. Inst. Skogforst 42 (1): 19-36.Sweden: Disease; YieldAn account of the effect of crown decline on yields.

Boardman, R. 1978. Productivity under successive rotations of Radiatapine. Australian Forestry 41(3): 177-179.Australia: YieldSecond rotation decline was correlated to site quality of the firstrotation. It is important to stimulate the growth of young stands.

Boariman, R. 1982. Use of balanced fertilizers to produce acceptablegrowth rates in Finus radiata on marginal sites in South Australia. In:RTFRo Symposium on Forest Site and Continuous Productivity, Washington,323-332.Australia: Soils. ManagementAnalysis of rooting strategies. Yield decline overcome by payingattention to organic matter content of the topsoil, the principalsource of he exchanges. Lack of organic mat'cer results in compaction.Litteraccumulation must be avoided. Stepped application of fertilizersis well suited to Pinus radiata.

Boardman, R. 1988. Living on the edge - the development of silviculturein South Australia pine plantations. Australian Forestry 51 (3): 135-156.

Australia: ManagementA history of silviculture in S.Australia.

Boardman, R. 1990. The use of species mixtures in plantations for reha-bilitation purposes in the winter rainfall areas of South Australia. InEcology of Mixed Stands of Trees. British Ecological Society and IUFRODiv S2.01 Symposium.Australia: ManagementDiscusses compatibility in mixtures using evidence from spaced groupplantings in Eucalyptus and from espacement trials in P.radiata toproduce vigour models. Mixtures are being used in effluent schemes.

Boardman, R. 1991. Personal communication.Australia: ManagementIntrinsically lower rate of nitrogen mineralisation in P.radiataplantation in comparison to natural woodland.

Bond, G. 1983. Taxonomy and distribution of non-legume N-fixing systems.In: Biological Nitrogen fixation in forest ecosystems: Foundations andapplications. J.C.Gordon and C.T. Wheeler eds. Martinus Nijhoff/DrW.Junk publishers.General: SoilsLists genera which include species bearing Alnus-type nodules.

Bossut, P. 1988. Premiers resultats des plantaticns d'acaciasAnstraliens. AFR1 (Togo), urn', unpublished.Togo: Yield. SoilsLine mixtures established 1982-83 to improve sites unsuitable for pureeucalyptus plantations were enumerated. The acacia, on average,produced twice as much wood as eucalyptus.

Boyce, J.S. 1954. Forest plantation protection against disease and insectpests. FAO Forestry Development Paper 3 pp 41.General: Pests and DiseasesA general review of pest and disease problems .

Brandis, D. 1901. Pure forests and mixed forests. Transactions of theRoyal Scottish Arboricultural Society.Germany: Management

80

Bjorkdahl., G. and Eriksson, H. 1989 Effects of cr= decline on inCrem2l1t in NOrway spruce (Picea abies (L.) Kunst.) in southern SWeden. Medel. Norsk. Inst. Skogforst 42 (1): 19-36. SWeden: Disease; Yield An account of the effect of cr= decline on yields.

Boardnan, R. 1978. Productivity under successive rotations of Radiata pine. Australian Forestry 41(3): 177-179. Australia: Yield Second rotation decline was correlated to site quality of the first rotation. It is important to stimulate the grCMth of young stands.

Boardnan, R. 1982. Use of balanced fertilizers to produce acceptable grCMth rates in Pinus radiata on marginal sites in SOuth Australia. In: IUFRO Sympcsium on Forest Site and Continuous productivity, Washington, 323-332. Australia: SOils. Management Analysis of rooting strategies. Yield decline overcane by paying attention to organic matter content of the topsoil, the principal source of base exchanges. Lack of organic matter results in carpaction. Litter accumulation must be avoided. stepped application of fertilizers is well suited to Pinus radiata.

Boardnan, R. 1988. Living on the edge - the developnent of silviculture in South Australia pine plantations. Australian Forestry 51 (3): 135-156. Australia: Management A history of silviculture in S.Australia.

Boardnan, R. 1990. The use of species mixtures in plantations for reha­bilitation purposes in the winter rainfall areas of SOuth Australia. In Ecology of Mixed Stands of Trees. British Ecological Society and IUFRO Div S2.01 Symposium. Australia: Management Discusses carpatibility in mixtures using evidence fram spaced group plantings in Eucalyptus and fran espacement trials in P.radiata to produce vigour roodels. Mixtures are being used in effluent schemes .

Boardnan, R. 1991. Personal crnrnunication. Australia: Management Intrinsically lower rate of nitrogen mineralisation in P.radiata plantation in carparison to natural woodland.

Bond, G. 1983. Taxonany and distribution of non-legume N-fixing systems . In: Biological Nitrogen fixation in forest ecosystems: Foundations and applicatiOns. J . C . Gordon and C. T. Wheeler eds. Martinus Nijhoff/Dr W.Junk publishers. General: Soils Lists genera which include species bearing Alnus-type nodules.

Bossut, P. 1988. Premiers resultats des plantations d'acacias Australiens. AFRI (Togo), Cl'FT, unpublished . Togo: Yield. SOils

. Line mixtures established 1982-83 to :iroprove sites unsuitable for pure eucalyptus plantatiOns were enumerated. The acacia, on average, produced twice as much wood as eucalyptus.

Boyce, J. S. 1954. Forest plantation protection against disease and insect pests. FAD Forestry Developnent Paper 3 pp 41 . General: Pests and Diseases A general review of pest and disease problems .

Brandis, D. 1901. Pure forests and mixed forests. Transactions of the Royal Scottish Arboricultural Society. Gemany: Management

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Pine/Spruce and Pine/Beech mixtures are less prone to Nun moth (Eiparismonarcha) attacks . Pine/Beech and Larch/Beech mixtures have better soilstructure. Oak/Beech mixtures in Spessart depend on early felling ofbeech for glassworks, allowing oak to came through.

Brown, A.H.F. 1990. FUnctioning of mixed species stands: the Gisburnexperiment in NW England. In Ecology of Mixed Stands of Trees. BritishEcological Society and IUFRO Div S2.01 Symposium.UK: SoilsMixture effect may be positive, negative or compensatory. In the caseof spruce N (and possibly P) nutrition appeared to be implicated,availability of which may vary with differences in turnover of organicmatter or camplementarity of rooting patterns.

Brown, A.H.F. and Harrison, A.F. 1983. Effects of tree mixtures onearthworm populations and nitrogen and phosphorus status in Norwayspruce (Picea abies) stands. In New Trends in Soil Biology. Lebrun,P., Andre, H.M. and Medts, A. (eds.) p 101-108. Université Catholiquede Louvain, Louvain-la-Neuve. pp 703.UK: Soils26-year-old mixture of Spruce, Alder and Scots pine at Gisburn.Earthworm numbers and weight, soil NO,, P status and tree height wereincreased by an admixture of alder and more so of pine. Admixed treesare assumed to have encouraged earthworms, resulting in an increasedmineralisation of N and P.

Bruenig, E.F. 1983. Designing ecologically stable plantations. In:

Strategies and Designs for Afforestation and Tree Planting. Proceedingsof an International Symposium (Wiersum, K. F. ed.), PUDOC, Wageningen,1984Germany: Management. YieldThe rigidity of present-day forestry is criticized. Guidelines for amore flexible and functional forestry are given. A practical example ofimplementation of these is provided.

Bruenig, E.F. 1991(a). ITTO guidelines for the sustainable management ofman-made tropical forests (First Draft). Presented to the Permanentcommittee on reforestation and Forest Management at the seventhsession, Quito, Ecuador.Tropics: ManagementOutlines 48 principles and suggests 56 possible lines of action, withparticular reference to maintaining stability and reducing risk. Mixedplanting strongly favoured.

Bruenig, E.F. 1991(b). Forests and climate: new dimensions andperspectives. Position Paper, Theme 1, 10th World Forestry Congress,Paris, 1991. Proceedings Vol. 2: 9-15.Global: ManagementDraws attention to the problems inherent in man-made forests due totheir design for maximum production leading to ecological instability.Man-made forests must be modified to cope with impending climaticchanges.

Budowski, G. 1983. Biological diversity and forestation in the tropics.In: Strategies and Designs for Afforestation and Tree Planting.Proceedings of an International Symposium (Wiersum, K. F. ed.), PUDOC,Wageningen, 1984.The tropics: ManagementAdvantages of plantations over natural forests are summarized. The sofar limited, and largely disappointing, experiences of mixedplantations is discussed. An exception is the use of cover and shadecrops.

81

Pine/Spruce and Pine/Beech mixtures are less prone to Nun roth (Liparis monarcha) attacks. Pine/Beech and Larch/Beech mixtures have better soil structure. Oak/Beech mixtures in Spessart depend on early felling of beech for glassworks, allowing oak to cane through.

Brown, A.H.F. 1990. FUnctioning of mixed species stands: the Gisbum experiment in NW England. In Ecology of Mixed Stands of Trees. British Ecological 8=iety and IUFRO Div S2.01 Syrrposium. UK: Soils Mixture effect may be positive, negative or ccnpensatory. In the case of spruce N (and possibly P) nutrition appeared to be irrplicated, availability of which may vary with differences in turnover of organic matter or complementarity of rooting patterns.

Brown, A.H.F. and Harrison, A.F. 1983. Effects of tree mixtures on earthwonn populations and nitrogen and phosphorus status in NoJ:WaY spruce (Picea abies) stands. In New Trends in Soil Biology. Lebrun, P., Andre, H.M. and Medts, A. (eds.) P 101-108 . Universite catholique de Louvain, Louvain-la-Neuve. pp 703. UK: Soils 26-year-old mixture of spruce, Alder and Scots pine at Gisbum. Earthwonn numbers and weight, soil NO., P status and tree height were increased by an admixture of alder ana rore so of pine. Admixed trees are assumed to have encouraged earthwonns, resulting in an increased mineralisation of N and P.

Bruenig, E.F. 1983. Designing ecologically stable plantations. In : Strategies and Designs for Afforestation and Tree Planting. proceedings of an International Syrrposium (Wiersum, K.F. ed.), PUlXlC, Wageningen, 1984. Gennany: Management. Yield The rigidity of present-day forestry is criticized. Guidelines for a rore flexible and functional forestry are given . A practical example of irrplementation of these is provided.

Bruenig, E.F. 1991(a). ITIO guidelines for the sustainable management of man-made tropical forests (First Draft). Presented to the Pennanent carrnittee on reforestation and Fbrest Management at the seventh session, Quito, Ecuador. Tropics: Management Outlines 48 principles and suggests 56 possible lines of action, with particular reference to maintaining stability and reducing risk. Mixed planting strongly favoured.

Bruenig, E.F. 1991(b). Forests and climate: new dimensions and perspectives. Position Paper, Theme 1, 10th World Fbrestry Congress, Paris, 1991. Proceedings Vol. 2: 9-15. Global: Management Draws attention to the problems inherent in man-made forests due to their design for maximum production leading to ecological instability. Man-made forests must be Il'Cldified to cope with irrpending climatic changes.

Budowski, G. 1983. Biological diversity and forestation in the tropics. In: Strategies and Designs for Afforestation and Tree Planting . Proceedings of an International Syrrposium (Wiersum, K.F. ed.), PUlXlC, Wageningen, 1984 . The tropics: Management Advantages of plantations over natural forests are summarized. The so far limited, and largely disappointing, experiences of mixed plantations is discussed. An exception is the use of cover and shade crops.

82

Bule, L. and Daruhi, G. 1990. Status of Sandalwood resources in Vanuatu.In Proceedings of the Symposium on Sandalwood in the Pacific, April1990, Honolulu, Hawaii. US Department of Agriculture, Forest Service,General Technical Report PSW-122. pp 79-84.Vanuatu: Management.A history of exploitation of Sandalwood in Vanuatu and an account ofcurrent problems and research.

Burdon, R.D. 1982. Mbnocultures - how vulnerable? What's new in ForestResearch No. 115. Forest Research Institute, Rotorua.New Zealand: Environmental. SoilsCriticism of pure even aged plantations are summarized and discussed.It is concluded that pure even aged stands are not automatically morevulnerable thaninixed stands. The limited success of exotics other thanRadiata pine in New Zealand is noted.

Burley, J. and Ikemori, Y.K. 1988. Tropical forest production: the impactof clonal propagation technology. In Towards an Agro-industrial Future,Royal Agricultural Society of England, Mbnograph Series 8: 169-180.Brazil: ManagementA description of the tree breeding and cloning programme of Aracruz,Brazil.

Butterfield, J., Standen, V. and Benitez MaIvido, J. 1990. The effect ofmixed species planting on the distribution of soil invertebrates inbroadleaved and conifer stands. In Ecology of Mixed Stands of Trees.British Ecological Society and IUFRO Div S2.01 Symposium.UK: SoilsDistribution of Enchytraeidae carabid ground beetle determined by soiltype and tree species.

Calabri, G. 1991. Problems and prospects for forest fire prevention andcontrol. Position Paper, Theme 5, 10th World Forestry Congress, Paris,1991. Proceedings, Vol.2: 405-414.Global: ManagementStatistics on forest fires and means of hazard reduction.

Campinhos, E. and ikemori, Y. K. 1986. Breeding Eucalyptus in Brazil.Aracruz Florestal S.A. mdmeographed Report pp 9.Brazil: ManagementReviews the need for improvement in genetic quality in treeplantations. Beside increases in volume etc major improvements in wooddensity, pulp yield, coppicing ability achieved. Economic advantageBrazil $55/ton pulp v. Finland $155.

Campinhos, E. and Claudio-da-Silva, E. 1990. Development of theEucalyptus tree of the future. Paper presented to ESPRA Springconference, Seville, Spain. Aracruz Florestal S.A. mimeographed report.Brazil: ManagementImportance of breeding for pulp quality. Volume mai (1990) has fallento 35m3 as against 45m3 in 1985 as a result of drought.

Canizares, E.G. et al. (1987?). Propuesta de planificacion territorial dela actividad forestal en la Sierra del Rosario, alba. IESACC, A. P.8010, C. Habana 10800.Cuba: ManagementDerives a stress index for sites, and an index for each species'ability to cope with the stress. Using these indices, it should bepossible to match species to sites.

Carlson, A. 1986. A comparison of birds inhabiting pine plantation andindigenous forest patches in a tropical mountain area. BiologicalConservation 35: 195-204.Kenya: Wildlife

82

Bu1e, L. and Daruhi, G. 1990. Status of Sandalwood resources in Vanuatu. In Proceedings of the S~itnn on Sandalwood in the Pacific, April 1990, Honolulu, Hawaii. US Department of Agriculture, Fbrest Service, General Technical Report PSW-122. pp 79-84 . Vanuatu: Management. A history of exploitation of Sandalwood in Vanuatu and an account of current problems and research.

Burdon, R.D. 1982. MJnocultures - h~ vulnerable? What's new in Fbrest Research No. 115. Forest Research Institute, Rotorua. New Zealand: Environmental. Soils Criticism of pure even aged plantations are s\.ll11l1arized and discussed. It is concluded that pure even aged stands are not automatically more vulnerable than mixed stands. The limited success of exotics other than Radiata pine in New Zealand is noted.

Burley, J. and IkaJDri., Y.K. 1988. Tropical forest production: the impact of clonal propagation technology. In T~ an Agro-industrial FUture, Royal Agricultural Society of England, MJnograph Series 8: 169-180 . Brazil: Management A description of the tree breeding and cloning programme of Aracruz, Brazil.

Butter.fie1d, J., standen, V. and Benitez Malvido, J. 1990. The effect of mixed species planting on the distribution of soil invertebrates in broadleaved and conifer stands. In Ecology of Mixed Stands of Trees. British Ecological Society and IUFRO Div S2.01 Sympositnn. UK: Soils Distribution of Enchytraeidae carabid ground beetle detennined by soil type and tree species.

Ca1abri, G. 1991. Problems and prospects for forest fire prevention and control. Position Paper, Theme 5, 10th World Forestry Congress, Paris, 1991. Proceedings, Vol.2: 405-414. Global: Management Statistics on forest fires and means of hazard reduction.

CaIpinhos, E. and IkaJDri., Y.K. 1986. Breeding Eucalyptus in Brazil. Aracruz Florestal S.A. mimeographed Report pp 9. Brazil: Management Reviews the need for improvement in genetiC quality in tree plantations. Beside increases in volume etc major improvements in wood density, pulp yield, coppicing ability achieved. Econanic advantage Brazil $55/ton pulp v. Finland $155.

Caopinhos, E. and C1anilio-da-Silva, E. 1990. Developrent of the Eucalyptus tree of the future. Paper presented to ESPRA Spring conference, SeVille, Spain. Aracruz Florestal S.A. mimeographed report. Brazil: Management Importance of breeding for pulp quality. Volume mai (1990) has fallen to 35m3 as against 45m3 in 1985 as a result of drought.

Canizares, E.G. et al. (i987?). Propuesta de planificacion territorial de la actividad forestal en la Sierra del Rosario, Cul:E . IESACC, A.P. 8010, C. Habana 10800. CUba: Management Derives a stress index for sites, and an index for each species' ability to cope with the stress. Using these indices, it should be possible to match species to sites.

carlson, A. 1986. A canparison of birds inhabiting pine plantation and indigenous forest patches in a tropical mountain area. Biological Conservation 35: 195-204. Kenya: Wildlife

83

Specialist species were more impoverished in Radiata pine plantationsthan were generalists. Palaearctic species were favoured by pine.Native forests reserves are needed, and islands and mosaics of nativeplant species.

Carlson, P.J. and Dawson J.0. 1984. Effects of autumn-olive and blackalder leaf mulches on the growth of eastern cotton wood in two soils.Forestry Research Report, Dept. of Forestry, Agricultural ExperimentStation, University of Illinois 84-1: pp 3.USA: SoilsIn pot experiments, mulch of Alms glutinosa and Eaaeagnus umbellataleaves (especially of the latter) improved growth of Populus deltoddesin both loamy prairie soil and 2:1:1 sand:peat:soil mixture. N-fixingspecies may be beneficial even on fertile prairie soil.

Cellier, KiM., Boardman, R., Boamsma, D.E. and Zed, P. G. 1985. Responseof Pinus radiata D.Don to various silvicultural treatments on adjacentfirst- and second-rotation sites near Tantanoola, south Australia. I.Establishment and growth up to age 7 years. Australian FOrestryResearch 15: 431-447.Australia: Management, SoilsDescription of treatments on paired first- and second-rotation plots.Of particular effect were weed control using a herbicide, Phosphateaddition at high level and Nitrogen at moderate level; lime effectiveon 2nd rotation. No difference between yields of two rotations atoptimum levels; overall increase in yield of 30%.

Chaffey, D.R. 1978. Decline in productivity under successive rotations offorest monoculture. Land Resources Division, Miscellaneous Report 243,ODA, London.General reviewLiterature review under the following main headings; pathogens, soil -physical properties, soil- chemical properties, biological factors andclimate.

Champion, H.G. 1954. Forestry. Oxford University Press (UK).General textbook: ManagementLine and matrix mixing are briefly explained. The relative rarity ofsuccessful mixtures is noted.

Champion, H.G. and Griffith, A.L. 1948. Manual of general silviculturefor India. Geoffrey Cumberlege, Oxford University Press (UK).India: Management, textbookImportant reasons for failures with mixed plantations are summarised.Limited present knowledge means that work must probably be experimentalfor many years to came. Evidence indicates that benefits from mixturesmust be derived from the maintenance of soil over future rotations.

Chapman, K., Whittaker, J.B. and Heal, O.W. 1988. Metabolic and faunalactivity in litters of tree mixtures compared with pure stands.Proceedings: Wbrkshop on interactions between soil-inhabitinginvertebrates and microorganisms in relation to plant growth, Columbus,Ohio, March 1987. In: Agriculture, Ecosystems and Environment V. 24 (1-3), Elsevier, 1988.UK: SoilsVis-a-vis single species stands, nutrient availability and tree growthwere enhanced in spruce/pine and depressed in spruce/alder andspruce/oak mixtures. Mbbilization rates were correlated positively withmetabolic activity, and related to changes in the decomposer communityof the forest floor.

Chaturvedi, A.R. 1983. Eucalyptus for Farming. Uttar Pradesh ForestBulletin 48. 48pp

83

Specialist species were more impoverished in Radiata pine plantati ons than were generalists. Palaearctic species were favoured by pine. Native forests reserves are needed, and islands and mosaics of native p l ant species.

carlson, P.J. and Dawson J .D. 1984. Effects of auturrm- olive and black alder leaf llDllches on tbe gra-vth of eastern cotton wocd in two soils. Fbrestry Research Report, Dept. of Forestry, Agricultural Experiment Station, University of Illinois 84- 1: pp 3. USA: Soils In pot experiments, llDllch of Alnus glutinosa and Elaeagnus umbellata leaves (especially of the latter) improved grCMth of Populus deltoides in both loamy prairie soil and 2:1:1 sand:peat:soil mixture. N-fixing species may be beneficial even on fertile prairie soil.

Cellier, K.M., Boarduan, R., lloansma, D.B. and Zed, P.G. 1985. Response of Pinus radiata D.Don to various silvicultural treat:rrents on adjacent first- and second- rotation sites near Tantanoola , south Australia . I. Establishment and grCMth up to age 7 years . Australian Forestry Research 15: 431-447. Australia : Management, Soils Description of treat:rrents on paired first- and second-rotation plots . Of particular effect were weed control using a herbiCide, Phosphate addition at high level and Nitrogen at moderate level; lime effective on 2nd rotation . No difference between yields of two rotations at optimum levels; overall increase in yield of 30%.

Chaffey, D.R. 1978. Decline in productivity under successive rotations of forest monocul ture. Land Resources Division, Miscellaneous Report 243, ODA, London. General review Literature review under the follONing main headings; pathogens, soil -physical properties, soil - chemical properties , biological factors and climate.

Chanpion, H. G. 1954. Forestry . Oxford University Press (UK) . General textbook: Management Line and matrix mixing are briefly explained . The relative rarity of successful mixtures is noted .

Chaopion, H.G. and Griffith, A.L. 1948. Manual of general silviculture for India. Geoffrey CUmberlege , Oxford University Press (UK). India: Management, textbook !rrq?ortant reasons for failures with mixed plantatiOns are sUlllllarised. Limited present knONledge means that work must probably be experimental for many years to cane . Evidence indicates that benefits fran mixtures llDlSt be derived fran the maintenance of soil over future rotations.

ChapDan, K., Whittaker, J.B. and Heal, D.W. 1988. Metabolic and faunal activity in litters of tree mixtures canpared with pure stands. Proceedings: Workshop on interactions between soil-inhabiting invertebrates and microorganisms in relation to plant grCMth, Columbus, Ohio, March 1987. In: Agriculture, Ecosystems and Environment V. 24 (1-3), Elsevier, 1988 . UK: Soils Vi s-a.-vis single species stands, nutrient availability and tree gra-vth were enhanced in spruce/pine and depressed in spruce/alder and spruce/oak mixtures . MJbilization rates were correlated positively with metabolic activity, and related to changes in the decanposer ccmnuni ty of the forest floor .

Chaturvedi, A.N. 1983. Eucalyptus for Farming. Uttar Pradesh Forest Bulletin 48 . 48pp

84

India: ManagementSuppression inevitably occurs in a mixture. Eucalyptus tends to suffermore from competition. 9 mixtures have been tried and rejected.

Chijioke, E.O. 1980. Empact on soils of fast-growing species in lowlandhumid tropics. André Mayer Research Fellowship. FAO Forestry Paper 21,FAO, Rome.Tropics: SoilsNo evidence that monoculture leads to a more rapid depletion of thesoil nutrient reserves than would mixtures having the same biomassproduction, rotation length and the same proportion of the crop removedin harvesting.

Chou, C.K.S. 1981. Mbnoculture, species diversification, and diseasehazards in plantation forestry. New Zealand Journal of Forestry 26

(1): 20-42.New Zealand: Environmental, Pests and diseasesThe issue of stand composition and disease hazard is unclear. If apathogen has several host species, mixtures may be no safer than purestands. This makes prescription of safe mixtures hard. Regimes formixed stands may by themselves create disease problems. Crop rotationis a form of mixture that may prove necessary.

Chu, C.G.1980. (Study on biological productive forces of Pinus koraiensisartificial forest.) Institute of Forestry and Pedology, AcademiaSinica.China: YieldPure and mixed stands of Pinus koraiensis are compared. Total biomasswhen mixed with broadleaves is higher than in pure stands. Quality andvigour of mixed stands is also higher.

Ciesla, W.M. 1991. Cypress aphid: a new threat to Africa's forests.Unasylva 167. Vol.42: 51-55.Eastern Africa: Insect attadkAccount of attacks to CUpressus lusitanica by Cinara cupressi.

Ciesla, W.H. and J.E. Mari as Samano. 1987. Desierto de los Leones: Aforest in crisis. American Forests 93: 29-31, 72-74.Environment: Pollution

Clatterbuck, W. K., Oliver, C.D. and Burkhardt, E. C. 1987. The silvi-cultural potential of mixed stands of cherrybark oak and Americansycamore: Spacing is the key. Southern Journal of Applied Forestry 11:158-161.USA: ManagementLine mixture of Cuercus falcata var. pagudifolia, Platanus occidentalisand Populusdeltoides(died out). Q. falcata, the more valuable species,was suppressed by neighbouring P. occidentalis. At 24 years dominant Q.falcata caught up with P. occidentalis. Management obviously important.

Clattetbudk, W.K. and Hodges, J.D. 1988. Development of cherrybark oak andsweet gum in nixed, even-aged bottomland stands in central Mississippi,USA. Canadian Journal of Forest Research 18(1): 12-18.USA: Yield. Management"Restricted" development occurred at a spacing of 5.5 m. Liquidambarstyraciflua dominated for 20 years. By age 58 Q. falcata had a dbh of61 an and a height of 34 m. "Unrestricted" development occurred wheredominants or codominants were more than 5.5 m apart. Then Q. falcataachieved 56 an dbh and 26 m in height at age 40.

Clout,M.N. 1985. Wildlife in pine plantations - the New Zealand position.In: Wildlife management in the forests and forestry controlled lands inthe tropics and southern hemisphere. ed J.Kikkawa. IUFRO Workshop heldat University of Queensland, Australia.

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India: Management Suppression inevitably occurs in a mixture . Eucalyptus tends to suffer rrore fran ccrnpetition. 9 mixtures have been tried and rejected.

Chijioke, E.O. 1980. Impact on soils of fast-growing species in lowland humid tropiCS. Andre Mayer Research Fellowship. F7IO Forestry Paper 21, F7IO, Rare. Tropics: Soils No evidence that rronoculture leads to a rrore rapid depletion of the soil nutrient reserves than would mixtures having the same bianass production, rotation length and the same proportion of the crop rem:Jved in harvesting.

Chou, C.K.S. 1981. M:moculture, species diversification, and disease hazards in plantation forestry . New Zealand Journal of Forestry 26 (1): 20-42 .

. New Zealand: Envirornnental, Pests and diseases The issue of stand canposition and disease hazard is unclear. If a pathogen has several host species, mixtures may be no safer than pure stands. This makes prescription of safe mixtures hard. Regimes for mixed stands may by themselves create disease problems. crop rotation is a fonn of mixture that may prove necessary.

elm, C.G.1980. (Study on biological productive forces of Pinus koraiensis artificial forest.) Institute of Forestry and Pedology, Academia Sinica. China: Yield Pure and mixed stands of Pinus koraiensis are carpared. Total bianass when mixed with broadleaves is higher than in pure stands. QJ.ality and vigour of mixed stands is also higher.

Ciesla, W.M. 1991. Cypress aphid : a new threat to Africa's forests. Unasylva 167. Vol.42: 51-55. Eastern Africa: Insect attack Account of attacks to Cupressus lusitanica by Cinara cupressi.

Ciesla, W.M. and J.E. Macias Samano. 1987. Desierto de los Leones: A forest in crisis . American Forests 93: 29-31, 72-74. Envirornnent: Pollution

Clatt:erl:JUck, W.K., Oliver, C.D. and Burkhardt, E.C. 1987. The silvi­cultural potential of mixed stands of cherrybark oak and American sycarrore: Spacing is the key. Southern Journal of Applied Forestry 11: 158-16l. USA: Management Line mixture of Olercus falcata var. pagcxlifolia, Platanus occidentalis and Populus deltoides(died out). Q. falcata, the rrore valuable speCies, was suppressed by neighbouring P. occidentalis. At 24 yean; daninant Q. falcata caught up with P. occidentalis. Management obviously important.

Clatt:erl:JUck, W.K. and Hodges, J.D. 1988. Developnent of cherrybark oak and sweet gum in mixed, even-aged bottanland stands in central MiSSiSSippi, USA. Canadian Journal of Forest Research 18(1): 12-18. USA : Yield. Management "Restricted" developnent oc=ed at a spacing of 5.5 In. Liquidambar styraciflua daninated for 20 years . By age 58 Q. falcata had a dbh of 61 an and a height of 34 In. "Unrestricted" developnent oc=ed where daninants or codaninants were rrore than 5.5 In apart. Then Q. falcata achieved 56 an dbh and 26 In in height at age 40.

Clout,M.N. 1985. Wildlife in pine plantations - the New Zealand position . In : Wildlife management in the forests and forestry controlled lands in the tropics and southern hemisphere. ed J. Kikkawa . IUFRO Workshop held at University of QJeensland, Australia.

85

Tropics and southern hemisphere: WildlifeDiversityof native bird species is positively correlated to structuralhabitat diversity. Young pine plantations are particularly poorhabitats for native birds.

Cossalter, C. 1991. Personal communication.Coster, C. 1934. Rapport over de raboisatie der Tegal-Naroe landen.

(Report of the reafforestation of the Tegal Waru lands 1934.)Unpublished.Noted in Indonesian Forestry Abstracts, PUDOC, Wageningen,1982. Abstract 626.Indonesia: ManagementRecommendations of methods to reafforest grasslands. Mixtures withAlbizia falcataria in the top storey is among the methods recommended.

Cot6, B. and Camire, C. 1987. Tree growth and nutrient cycling in denseplantings of hybrid poplar and black alder. Canadian Journal ofForest Research 17 (6): 516-523.Canada: SoilsAlnus glutinosa and POpulus nigra x P. trichocarpa. Stimulatory effectof alder on poplar growth decreased over three years. Reducedcompetition of the smaller alder for soil N and light in the firstgrowing season is considered the most important factor in increasingindividual poplar growth.

Courrier, G. and Garbaye, J. 1981. A propos dé la sylviculture despeuplementsmélanges. On exemple de l'effet tenefique de l'aulne sur lacroissance des peupliers. Revue Forestier Franr,laise 33 (4): 289-292.France: SoilsFertilizer effects on loppulus "Fritzi Pauley" had completelydisappeared after 10 years, but there was strong correlation betweenpoplar volume and number of Alms glutinosa.

Craib, I.J. 1947 The silvicultura of exotic conifers in South Africa.Journal of the South African Forestry Association 15: 11-45.South Africa: ManagementRecommendations for heavy early thinnings in conifers to maximiseeconomic returns.

Ciki 1977 (?). Frojet de pdantation du framiré en mélange avec d'autresessences (fraké, samba, cedrela, ou corola). Iroposé à la _Direction deRéboisement de la SODEFOR. MIT Division d'Entomologie et de PathologieForestieres (unpublished).c'1101': Management, regeneration, spacingIt has been found that efforts at raising Terminalia ivorensis are moresuccessful when they are raised at low densities. To keep up

profitability, mixtures have been tried.Liki 1991. ESsais: Composition de peuplement 'in6lange d'essences"

(Experiments: Mixed stands). Unpublished. Nogent-sur-Marne.West Africa (+ Madagascar, French Guyana, New Caledonia); Management,YieldsA summary of each of 63 experiments (active or closed) mainly-in 8 WestAfrican francophone countries.

Darrah, G.V. and Dodds, J.W. 1967. Growing broadleaved trees in mixturewith conifers. Forestry 40 (2): 220-228. UK.UK: ManagementCompatibility between species, or provenances, is important to thesuccess of a mixture. Yields of conifers are often less than optimalbecause thinnings occur at inconvenient times, especially if the mix isincompatible.

Darroze, S. 1991. Personal communication.

85

Tropics and southern hemisphere: Wildlife Diversity of native bird species is positively correlated to structural habitat diversity. Young pine plantations are particularly poor habitats for native birds.

Cossalter, C. 1991. Personal carmunication. Coster, C. 1934. Rapport over de reJ::.oisatie der Tegal-Waroe landen.

(Report of the reafforestation of the Tegal Waru lands 1934.) Unpublished. Noted in Indonesian Forestry Abstracts, PUIXlC, Wageningen, 1982. Abstract 626. Indonesia: Management Recarrnendations of methods to reafforest grasslands. Mixtures with Albizia falcataria in the top storey is among the methods recarrnended .

Cote, B. and Camire, C. 1987. Tree grCMth and nutrient cycling in dense plantings of hybrid poplar and black alder. Canadian Journal of Fbrest Research 17 (6): 516-523. Canada: Soils Alnus glutinosa and Populus nigra x P. trichocazpa. stimulatory effect of alder on poplar grCMth decreased over three years . Reduced canpetition of the srraller alder for soil N and light in the first grow-ing season is considered the lOC)st important factor in increasing individual poplar grCMth.

Courrier, G. and Garllaye, J. 1981. A propos de la sylviculture des peuplements melanges . Un exanple de 1 'effet benefique de 1 'aulne sur la croissance des peupliers. Revue Forestier Fran<;aise 33 (4): 289-292. France: Soils Fertilizer effects on Populus "Fritzi Pauley" had canpletely disappeared after 10 years, but there was strong correlation between poplar volume and mxnber of Alnus glutinosa.

Craib, I.J. 1947 The silviculture of exotic conifers in South Africa. Journal of the South African Fbrestry Association 15: 11-45. South Africa: Management Recarrnendations for heavy early thinnings in conifers to maximise economic returns.

CTE"l'1977 (?). Projet de plantation du framire en melange avec d'autres essences (frake, saml::e., cedrela, ou cordia). Propose a la Direction de RelxJisement de la SODEFOR. CTFT Division d'Entarologie et de Pathologie Fbrestieres (unpublished). CTFT: Management, regeneration, spacing It has been found that efforts at raising Tenninalia ivorensis are lOC)re successful when they are raised at lCM densities. To keep up profitability, mixtures have been tried.

CTE"l' 1991. Essais: Cmposition de peuplement 'melange d'essences" (Experiments: Mixed stands). Unpublished. CTFT, Nogent-sur-Marne. West Africa (+ Madagascar, French Guyana, New caledonia); Management, Yields A stmrnary of each of 63 experiments (active or closed) mainly in 8 West African francophone countries.

Darrah, G.V. and Dodds, J.W. 1967. GrCMing broadleaved trees in mixture with conifers. Fbrestry 40 (2): 220-228. UK. UK: Management carpatibility between species, or provenances, is important to the success of a mixture. Yields of conifers are often less than optimal because thinnings occur at inconvenient times, especially if the mix is incanpatible.

Darroze, s. 1991. Personal carmunication.

86

Davidson, J. 1986. Underplanting, interplanting and buffer planting forforest plantations. Assistance to the Forestry Sector of Bangladesh.UNDP/FAO Project BGD/79/017. Working Paper 18. Bangladesh: ManagementUnderplanting of ground cover crops is advocated. Examples ofsuccessful legumes are given. Two species mixtures with one legume arerecommended.

Dawkins, H.C. 1949. Timber planting in the Terminalia woodland ofNorthern Uganda. Empire Forestry Review 28 (3): 226-246.Uganda: ManagementEstablishment of Chlorophora excelsa and Khaya grandifdliola in amatrix of Phyllanthus discoideus and Grlelina aztorea. An analysis ofecological succession in a dry (5 months dry season) site from fire-prone Terminalia grassland to fire tender spp - Entandrophragmaangolense etc.

Dawson, J.0., Dzialowy, P.J., Gertner, G.Z. and Hansen, E.A. 1983.

Changes in soil nitrogen concentration around Aininz; glutinosa in amixed, short-rotation plantation with hybrid Populus. Canadian Journalof Forest Research 13(4): 572-576.USA: SoilsIn a 4-year-old mixed plantation N accretion was greatest inalder:poplar 1:1 plantations, less in 2:1 mixture and least in 3:1 mix.It is hypothesised that early accretion of N in soil results fromcompetition-induced stress resulting from shading by poplars or poplarallelochemicals.

DeBell,S.D., Whitesell,C.D. and Sdhaert,T.H. 1985. Mixed plantations ofEucalyptus and leguminous trees enhance biomass production. ResearchPaper PSW-175. Berkeley, CA: Pacific Southwest Forest and RangeExperiment Station, Forest Service, US Dept. of Agriculture. pp 6.Hawaii: Yield. SoilsN-fixingspecies, Acacia melanoxylon and Albizia falcataria, were grownin line mixtures of Eucalyptus grandis and E. saligna. At 65 monthsheight growth of eucalyptus was greater in mixtures with Albizia.Foliar nutrient concentrations were higher, and soil nutrients lower,in the mixtures.

DeBp11, D. S., Whitesell, C.D. and Crab, T. B. 1987. Benefits ofEUcalyptus-Albizia mdxtflres vary by site on Hawaii Island, ResearchPaper PSW-187. Berkeley, CA. Pacific Southwest Forest and RangeExperiment Station, Forest Service, US Dept. of Agriculture.

PP 5-Hawaii: Yield. ManagementInorganic fertiliser applied to pure and mixed plantations. Admixtureof Albizia tal cataría into EUcalyptus saligna plantations improvedeucalyptus growth on the two wetter sites, but not on the two driersites. On one site the Albizia failed. Failure attributed to lawrainfall. Acacia mangium may be an alternative to Albizia.

DeBell, D. S., Whitesell, C.D. and Sdhlibert, T.H. 1989. Using N2-fixingAlbizia to increase growth of Eucalyptus plantations in Hawaii. ForestScience 35 (1): 64- 75.Hawaii: Soils. YieldIn comparison to pure (heavily fertilised) eucalyptus (94 t/ha drymatter) those mixtures with 11 and 25% Albizia depressed yield by up to29%; higher proportions of Albizia increased yields by up to 12%. Buteven the plot with the lowest yield (67 t - 11% Albizia) had a higheryield than pure eucalyptus (outside the experiment) receiving standardfertilizer application (yield 44 t).

86

Davidson, J. 1986. Underplanting, inteI:planting and buffer planting for forest plantations. Assistance to the Forestry Sector of Bangladesh. UNDP/FAO Project BGD/79/017. Working Paper 18 . Bangladesh: Management Underplanting of ground cover crops is advocated. Examples of successful legumes are given. 'IWo species mixtures with one legume are recarmended.

Dawkins, H.C. 1949. Timber planting in the Tenninalia woodland of Northern Uganda. Empire Forestry Review 28 (3): 226-246. Uganda: Management Establishment of Chlorophora excelsa and Khaya grandifoliola in a matrix of Phyllanthus discoideus and Gnelina arrorea. An analysis of ecological succession in a dry (5 months dry season) site fran fire­prone Tenninalia grassland to fire tender spp - Entandrophragma. angolense etc.

Dawson, J.O., Dzialowy, P.J., Gertner, G.Z. and Hansen, E.A. 1983. Changes in soil nitrogen concentration around Alnus glutinosa in a mixed, short-rotation plantation with hybrid Populus. Canadian Journal of Forest Research 13(4): 572-576. USA: Soils In a 4-year-old mixed plantation N accretion was greatest in alder: poplar 1: 1 plantations, less in 2: 1 mixture and least in 3: 1 mix. It is hypothesised that early accretion of N in soil results fran carpetition-induced stress resulting fran shading by poplars or poplar allelochemicals.

DeBell ,S.D., Whitesell,C.D. and Schubert,T.H. 1985. Mixed plantations of Eucalyptus and leguminous trees enhance bianass production. Research Paper PSW-175. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, Forest Service, US Dept. of Agriculture. pp 6. Hawaii: Yield. Soils N-fixing speCies, Acacia melanoxylon and Albizia falcataria, were grown in line mixtures of Eucalyptus grandis and E. saligna. At 65 roonths height grCMth of eucalyptus was greater in mixtures with Albizia. Foliar nutrient concentrations were higher, and soil nutrients lower, in the mixtures.

DeBell, D.S., Whitesell, C.D. and Crabb, T.B. 1987. Benefits of Eucalyptus-Albizia mixtures vary by site on Hawaii Island. Research Paper PSW-187. Berkeley, CA. Pacific Southwest Forest and Range Experiment Station, Forest Service, US Dept. of Agriculture. pp 5. Hawaii: Yield. Management Inorganic fertiliser applied to pure and mixed plantations. Admixture of Albizia falcataria into Eucalyptus saligna plantations improved eucalyptus grCMth on the two wetter sites, but not on the two drier sites. On one site the Albizia failed. Failure attributed to law rainfall. Acacia mangium may be an alternative to Albizia.

DeBell, D.S., Whitesell, C.D. and Schubert, T.H. 1989. Using N2-fixing

. Albizia to increase grCMth of Eucalyptus plantatiOns in Hawaii. Forest Science 35 (1): 64- 75. Hawaii: Soils. Yield In canparison to pure (heavily fertilised) eucalyptus (94 t/ha dry matter) those mixtures with 11 and 25% Albizia depressed yield by up to 29%; higher proportions of Albizia increased yields by up to 12%. But even the plot with the lowest yield (67 t - 11% Albizia) had a higher yield than pure eucalyptus (outSide the experiment) receiving standard fertilizer application (yield 44 t).

87

Delwaulle, J.C. 1989. Plantations clonales au Congo. Point des recherchessur le cholg des clones dix ans apr'es les premie'res plantations. In:Gibson, G.L., Griffin, A.R. and Matheson, A.C. (eds). Proceedings of aConference on Breeding Tropical Trees: Population Structure and GeneticImprovement Strategies in Clonal and Seedling Forestry, held inPattaya, Thailand, 28 November - 3 December 1988. IUFRO WPs S2.02-08and S2.02-09.0xford Forestry Institute, UK. 431-434.Congo: Management

Delvaux, J. 1971. (Pure or mixed stands.) Bull. Soc. For. Belg. 78(4): 183-197.Reviewing articleA general discussion on the merits and drawbacks of mixed and purestands.

Deventer, A.J. van. 1913. Gemengde djatibosschen (prae-advies). Mixed teakforests (proposals).) Tectona 6: 273-293. Noted in Indonesian ForestryAbstracts, PUDOC, Wageningen, 1982. Abstract 600.Indonesia: SoilsA cover crop in a teak plantation must give soil protection, be shadetolerant, never overgrow the teak, and yield a marketable product.Kesmabi (Schleichera oleosa) is recommended for this.

Donaubauer, E. 1991. Plantation Management: Aspects of Resistance andResilience to Pests, Diseases and Abiotic Factors. UnpUblished reportfor FAO.General: Pests and DiseasesA review of the literature.

Dransfield, J. 1977. Calamus caesius and C. trachycoleus compared.Gardens' Bulletin, Singapore 30: 75-78.Indonesia: ManagementCalamus caesius, a rattan species, can be completely harvested twice,at 7-10 years and 4 years later, before exhaustion. This fits in witha shifting cultivation system where at least 14 years fallow needed.But if selective cutting is used, the plant's life is very much longer.C.trachycoleus has longer stolons and it therefore establishes itself.

Dransfield J. 1988. Prospects for rattan cultivation. Advances inEconomic Botany 6: 190-200.Malaysia/Indonesia: Management. Yield. EconomyHeavy shade results in poor growth, but longer internodes which isdesirable. Canes can be cultivated in secondary forest, poor qualityrubber plantations or under pines.

Duff, A-B., Hall, R.A. and Marsh, C.W. 1984. A survey of wildlife in andaround a commercial tree plantation in Sabah. The Malaysian Forester 47(3): 197-213.Malaysia (Sabah): WildlifeWildlife damage can be reduced by separating natural forests andplantations, or by planting unpalatable species at the boundary to thenatural forest. Islands of natural forests are beneficial to predators.Mammal presence is higher where ground cover is available.

Dunikowski, S. 1991. Protection des fOréts contre les agressions biotiques etabiotiques. Position Paper, Theme 4, 10th World Forestry Congress,Paris, 1991. Proceedings, VO1.2: 285-290.General: EnvironmentNeed to transform pure conifer stands, which are susceptible todamage from atmospheric pollution, into raixed stands with a highproportion of broadleaved trees.

87

DelwaulJ.e, J . C. 1989 . Plantations clonales au Congo. Point des recherches sur le choix des clones dix ans apres les premieres plantations . In : Gibson, G.L . , Griffin, A.R . and Matheson, A.C. (eds). Proceedings of a Conference on Breeding Tropical Trees: Population structure and Genetic Irrprovement Strategies in Clonal and Seedling Forestry, held in Pattaya, Thailand, 28 November - 3 December 1988. IUFRO WPs S2 . 02-08 and S2.02-09.Oxford Ferestry Institute, UK. 431-434. Congo: Management

Delvaux, J. 1971. (Pure or mixed stands . ) Bull. Soc. Fer. Belg. 78 (4): 183- 197. Reviewing article A general discussion on the merits and drawbacks of mixed and pure stands.

Deventer, A.J. van. 1913. GemengdedjatiJ:xJsschen (prae-advies). Mixed teak forests (proposals).) Tectona 6: 273-293 . Noted in Indonesian Forestry Abstracts, PUJX)C, Wageningen, 1982. Abstract 600. Indonesia : Soils A cover crop in a teak plantation must give soil protection, be shade tolerant, never overgrew the teak, and yield a marketable product. Kesrnabi (Schleichera oleosa) is recxmnended for this .

Donauhauer , E. 1991. Plantation Management : Aspects of Resistance and Resilience to Pests, Diseases and Abiotic Factors. Unpublished report for ElID. General: Pests and Diseases A review of the literature.

Dransfield, .J . 1977. calamus caesius and C. trachycoleus canpared. Gardens' Bulletin, Singapore 30 : 75-78. Indonesia: Management Calamus caesius, a rattan species, can be canpletely harvested twice , at 7-10 years and 4 years later, before exhaustion. This fits in with a shifting cultivation system where at least 14 years fallew needed . But if selective cutting is used, the plant's life is very much longer. C. trachycoleus has longer stolons and it therefore establishes itself.

Dransfield J. 1988. Prospects for rattan cuI ti vat ion . Advances in Economic Botany 6 : 190-200 . Malaysia/Indonesia: Management. Yield . Econany Heavy shade results in poor grcwth, but longer internodes which is desirable. Canes can be cultivated in secondary forest, poor quality rubber plantatiOns or under pines.

Duff, A.B . , Hall, R.A. and Marsh, C.W. 1984. A survey of wildlife in and around a a:mnercial tree plantation in Sabah . The Malaysian Forester 47 (3) : 197- 213. Malaysia (Sabah): Wildlife Wildlife damage can be reduced by separating natural forests and plantations, or by planting unpalatable species at the J::.oundary to the natural forest. Islands of natural forests are beneficial to predators. Mammal presence is higher where ground cover is available.

IlUnikcwski., S. 1991. Protection des forets contre les agressions biotiques et abiotiques. Position Paper, Theme 4, lOth World Forestry Congress, Paris, 1991 . Proceedings, Vol . 2 : 285-290. General : Environment Need to transfonn pure conifer stands, which are susceptible to damage fran atmospheriC pollution, into mixed stands with a high proportion of broadleaved trees.

88

Dupuy, B. 1985. Plantations à vocation tois d'oeuvre et associationsd'esp6ces en Ee6lange: objectifS et contraintes sylvicoles. crier, Cated'Ivoire (unpublished).Cate d'Ivoire: Management, Yields

Dupuy, B. 1986. (The main silvicultural rules for timber productionplantations.) calq, Cate d'Ivoire (unpublished draft).Cate d'Ivoire: ManagementMixtures can be classified into those made up of one main species andone with a cultural role, and those consisting of species of equalsilvicultural importance. Possible associations andregimes are discus-sed.

Dupuy, B. 1989a. Etude de E61ange: GMelina artorea/Acacia auriculifOrmis.C2Y2 (unpublished).Cate d'Ivoire: Management4 mixtures of G. artorea/A. auriculifOrmis were tested, 50, 33, 20 and10% of acacia. GMelina outgrew the acacias, except in the 10% mixture.In this kind of mixture firewood can be collected after 5 to 6 years,while the dominant species is allowed to grow.

Dupuy, B., 1989b. Sylviculture des peuplement en Epélange fraké/framiré.cfrT, Cate d'Ivoire (unpublished).Cate d'Ivoire: Management. YieldMixtures of Terminalia ivorensis/Terminalia superta, 50/50, 25/75 and6/94%, were compared. Rate of mixture does not appear to affect growthof either species. Silvicultural methods depend on which species is tobe favoured in the thinnings.

Durigan, G. and de Souza Dias, H.C. 1990. Abundancia e diversidade daregeneracao natural sob mata ciliar implantada. Instituto Florestal,Sao Paulo, Brazil. Mimeographed Paper presented to 6th Congresso Flo-restal Brasiliero.Brazil: ManagementRegeneration under riparian forest planted 1973 (17 years old) inCandida Mbta-SP. 150 species rianted, 41 other spp. regeneratednaturally. Only p. few plantad species regenerated, these includedexotics. Generally low species diversity in regeneration, tending to ahomogenous forest in the next succession stage.

Durigan, G. and Nogueira, J.C.B. 1990 Recomposicao de matas ciliares.Instituto Florestal Serie Registros, Sao Paulo 4: 1-14.Brazil: ManagementLists appropriate species for creating natural forests on river banksand classifies them by their ecological requirements and position inecological succession.

Earl, D.E. 1968. Latest techniqes in the treatment of natural high forestin South Mengo District. Paper to 9th Commonwealth Forestry Conference,India.Uganda: ManagementThe use of charcoal burning as a management tool in natural forestmanagement.

Eidmann, F.E. 1932. Bet onderplantingsvraagstuk van den djati. (Theproblem of underplanting teak.) Korte Meded. B.P.S. 27 and Tectona 25:671-690, 1628-1682. Noted in Indonesian Forestry Ahetracts, PUDOC,Wageningen, 1982, Abstract 984.Indonesia: ManagementIt is expected that the only successful way of underplanting teak willto thin regularly and heavily to open the canopy and at the same timeintroduce a shade tolerant, deep rooting species that will producevaluable wood.

88

nJpuy, B. 1985. Plantations a vocation bois d'oeuvre et associations d'especes en nelange: objectifs et contraintes sylvicoles. Cl'FT, COte d'Ivoire (unpublished). COte d' Ivoire: Managerrent, Yields

nJpuy, B. 1986. (The main silvicultural rules for timber production plantations.) Cl'FT, COte d' Ivoire (unpublished draft) . COte d'Ivoire: Managerrent Mixtures can be classified into those made up of one main species and one with a cultural role, and those consisting of species of equal sil vicul tural importance. Possible associations and regimes are discus­sed.

nJpuy, B. 1989a. Etude de nelange: Gnelina arborea/ Acacia auriculiformis. Cl'FT (unpublished). COte d'Ivoire: Managerrent 4 mixtures of G. arborea/A. auriculiformis were tested, 50, 33, 20 and 10% of acacia . Gnelina outgrew the acacias, except in the 10% mixture. In this kind of mixture firewocd can be collected after 5 to 6 years, while the daninant species is allowed to gr=.

nJpuy, B., 1989b. Sylviculture des peuplement en nelange frake/framire. Cl'FT, COte d' Ivoire (unpublished). COte d' Ivoire: Managerrent. Yield Mixtures of Terminalia ivorensis/Terminalia superb3, 50/50, 25/75 and 6/94%, were ~ed. Rate of mixture does not appear to affect grCMth of either species. Silvicultural methods depend on which species is to be favoured in the thinnings.

IJurigan, G. and de Souza Dias, H.C. 1990. Ahlndimcia e diversidade da regeneracao natural sob mata ciliar implantada. Instituto Florestal, Sao Paulo, Brazil. Mimeographed Paper presented to 6th Congresso Flo­restal Brasiliero. Brazil: Managerrent Regeneration under riparian forest planted 1973 (17 years old) in Candida MJta-SP. 150 species :-lanted, 41 other spp. regenerated naturally. Only -<;i few planted species regenerated, these included exotics. Generally 1= species diversity in regeneration, tending to a homogenous forest in the next succession stage.

IJurigan, G. and Nogueira, J.C . B. 1990 Reccmposicao de matas ciliares. Instituto Florestal Serie Registros, Sao Paulo 4: 1-14. Brazil: Managerrent Lists appropriate species for creating natural forests on river banks and classifies them by their ecological requirements and position in ecological succession.

Earl, D.E. 1968. Latest techniqes in the treatment of natural high forest in South Mengo District. Paper to 9th Catrronwealth Forestry Conference, India. Uganda: Managerrent The use of charcoal burning as a managerrent tool in natural forest managerrent.

EidDann, F.E. 1932. Het onderplantingsvraagstuk van den djati. (The problem of undeI:planting teak.) Korte Meded. B. P. S. 27 and Tectona 25: 671-690, 1628-1682. Noted in Indonesian Forestry Abstracts, PUIXlC, Wageningen, 1982, Abstract 984. Indonesia: Managerrent It is expected that the only successful way of underplanting teak will to thin regularly and heavily to open the canopy and at the same time introduce a shade tolerant, deep rooting species that will produce valuable wood.

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Evans, J. 1975. Two rotations of Pinuspatula in the Usutu forests,Swaziland. Commonwealth Forestry Review 54 (1): 69-81.Swaziland: YieldA slight increase in second rotation yield noted and attributed tobetter than average rainfall and reduced grass competition at time ofestablishment.

EVans, J. 1978. A further report on second rotation productivity in theUsutu forest, Swaziland - results of the 1977 reassessment.Commonwealth Forestry Review 57 (4): 253-261.Swaziland: YieldAverage rainfall was 1230 nim. Late arrival of spring rains 1974-6 canbe detected in growth rates (reports of drought-induced deaths).Reports on yields obtained from the second rotation or later arereviewed.

EVans, J. 1987. Site and species selection - changing peispectives.Forest Ecology and Management 21: 299-310.The tropics: Management. YieldReviews the need for the use of appropriate species, including theappropriateness for the end use, including village use. An analysis ofplantation species used in the tropics in order of frequency, excludingsouthern China.

EVans, J. 1988. The Usutu forest: 20 years later. Unasylva 159 (40):19-29.Swaziland: Yield. ManagementLaw rainfall in 1958-65 and 1978-82 is a confounding factor incomparing yields . Fertility losses maybe due to nutrient drain throughbiomass removals, alteration of soil characteristics or compaction anderosion resulting from the extraction. 15% of the area is on gabbrorock formations and here phosphate reserves may have been criticallydepleted.

EVans, J. 1990. Long-term productivity of forest plantations - status in1990. Procedings of IUFRO XIX World Congress, Montreal. Vol 1: 165-181.Tropics; Management, SoilsA review of yields attained in later rotations.

EWel, J.J. 1986. Designing agricultural ecosystems for the humid tropics.Annual Review of Ecology and Systematics 17: 245-271.The tropics: SoilsA general review of the literature. Deep rooted species increase thesoil volume exploited. N fixers may use the N themselves and only makeit available through leaf fall. Organic matter accounts for up to 50%of total P in surface horizon of tropical soils.Organic P circulates rapidly.

FAO. 1988. An interim report on the state of forest resources in thedeveloping countries. Forestry Department FO:M1SC/88/7, FAO, Rome.The tropics: ManagementAn analysis of forest types and plantations as at 1980 with plantingestimates for 1981 to 1985.

FAO, 1991a. Exotic aphid pests of conifers: A crisis in African forestry.Workshop Proceedings, FAO/Kenya Forestry Research Institute, June 1991

FAO. 1991b. Les plantations à vocation de Lois d'oeuvre en Aftioueintertrqpicale huraidé. FAO Forestry Paper 98.West Africa: ManagementA silvicultural manual with a chapter on mixtures.

Farridhon, V. 1987. Résultats des 'etudes men6es au projet APRI d'avril1986 à Mai 1987. COvaraison de deux esp6ces d'eucalypts (T. tereti-cornis et E. torelliana) utilisées auprojet AEU. CIYI! (unpublished).

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Evans, J. 1975. Two rotations of Pinus patula in the Usutu forests, SWaziland. Ccmronwealth Forestry Review 54 (1): 69-8l. SWaziland: Yield A slight increase in second rotation yield noted and attributed to better than average rainfall and reduced grass carpetition at ti1lle of establishment .

Evans, J. 1978. A further report on second rotation productivity in the Usutu forest, SWaziland results of the 1977 reassessment. Commonwealth Forestry Review 57 (4): 253- 261. SWaziland: Yield Average rainfall was 1230 rrrn. Late arrival of spring rains 1974-6 can be detected in grCMth rates (reports of drought-induced deaths) . Reports on yields obtained fran the second rotation or later are reviewed .

Evans, J. 1987. Site and species selection - changing perspectives . Forest Ecology and Management 21: 299-310. The tropiCS: Management. Yield Reviews the need for the use of appropriate species, including the appropriateness for the end use, including village use . An analysis of plantation species used in the tropics in order of frequency, excluding southern China.

Evans, J. 1988 . The Usutu forest : 20 years later. unasylva 159 (40): 19-29. SWaziland: Yield . Management LcM rainfall in 1958-65 and 1978-82 is a confounding factor · in canparing yields . Fertility losses may be due to nutrient drain through bianass removals, alteration of soil characteristics or ccrrpaction and erosion resulting fran the extraction. 15% of the area is on gabbro rock fonmations and here phosphate reserves may have been critically depleted.

Evans, J. 1990. Long-tenn productivity of forest plantations - status in 1990. Procedings of IUFRO XIX World Congress, M:lntreal. Vol 1 : 165-18l. Tropics; Management, SOils A review of yields attained in later rotations.

Ewel, J.J. 1986. Designing agricultural ecosystems for the humid tropics. Annual Review of Ecology and SystematiCS 17 : 245-271. The tropics: SOils A general review of the literature . Deep rooted species increase the soil volume exploited. N fixers may use the N themselves and only make it available through leaf fall . Organic matter accounts for up to 50% of total P in surface horizon of tropical soils. Organic P circulates rapidly.

Ero. 1988. An interim report on the state of forest resources in the developing countries . Forestry Department FD:MISC/88/7, FAD, Rane. The tropics : Management An analysis of forest types and plantations as at 1980 with planting estimates for 1981 to 1985 .

Ero, 1991a. Exotic aphid pests of conifers: A crisis in African forestry. Workshop Proceedings, FAD/Kenya Forestry Research Institute, June 1991

Ero. 1991b. Les plantations a v=ation de bois d'oeuvre en Afrique intertropicale humide. FAD Forestry Paper 98. West Africa : Management A silvicultural manual with a chapter on mixtures.

Farrichan, V. 1987. Resultats des etudes menees au projet AFRI d'avril 1986 a mai 1987. CmJparaison de deux especes d'eucalypts (E. tereti ­cornis et E. torelliana) utilisees au projet AFRI. Cl'FT (unpublished).

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Togo: YieldIn a line mixture of E. tereticornis and E. torreliana, E. tereticarnishas proved to be the more competitive of the two.

Ferguson, I.S. 1983. Plantation Management in Australia. New ZealandJournal of Forestry 28 (3): 327-338.Australia: ManagementAn analysis of national forest policy in relation to plantationestablishment and the need for understanding marketing issues; includesa statement of areas under various tree crops.

Ferguson, J.H.A., Hellinga, G. and Alphen de Veer, F.J. van. 1949. Eenigegedachten over de Pinus kultur in indonesie. (Sane ideas about thecultivation of pines in Indonesia.) Tectona 39: 383-387. Noted in In-donesian Forestry Abstracts, PUDOC, Wageningen, 1982. Abstract 584.Indonesia: Management, cover cropTo avoid the risks of pure plantations when establishing plantationsof PiI2USmerkusii, mixing with Swieteniarnacrophylla on the plains, andwith Agathis loranthifolia in the mountains on not too poor soils isdiscussed.

Florence, R.G. 1967. Factors that may have a bearing upon the decline ofproductivity under forest monoculture. Australian Forestry 31: 51-71.General: SoilsAnalysis of factors that may lead to a long term decline inproductivity.

Florence, R.G. ami Lanib, D. 1974. Influence of stand and site on Radiatapine litter in South Australia. New Zealand Journal of Forest Science4 (3): 302-310.Australia: SoilsLitter accumulation related more to soil type than to site quality andto rate of decomposition than to rate of fall.

Francis, P.J. ami Shea, G.M. 1987. Management of tropical and sub-tropical pines in Queensland. In Forest Management in Australia;Proceedings of a Conference of the Institute of Foresters of Australiapp 273-280.Australia: Management

Franzini, F. 1957. Les reboisement artificiels dans les savanes de larégicn dé Ebinte Noire. (Afforestation of savannah land in the PointeNoire region.) Bois et Forêts des Tropiques 53: 25-32.Congo: ManagementExperiments in afforestation of savannas with Eucalyptus saligna,Eucalyptus camaldulensis and Casuarina equisetifolia are described.

FriedriCh, J.M. and Dawson, J.O. 1984. Soil nitrogen concentration andJuglans nigra grckath in mixed plots with nitrogen-fixing Alms, Elaeag-nus, Lespedeza and Ro_bi_nia species. Canadian Journal of Forest Research14 (6): 864-868.USA: SoilsIn a 14-year-old plantation with spacings of 3.7x4.9 and 9. 8m, thehighest total soil N concentration in top 30 cm was under closely-spaced Elaeagnus and both spacings of Robinia (girdled). Walnut basalarea was not strongly correlated with soil nitrogen concentration.

Friend, G.R. 1980. Wildlife conservation and softwood forestry inAustLdlia: same considerations. Australian Forestry 43 (4): 217-224.Australia: WildlifeRadiata plantations are specialised and simplified habitats. They areimpoverished in that they lack diversity in wildlife. Animals withoutspecialist requirements are least affected, even favoured, by planta-tions. Measures to counter this impoverishment are discussed

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Togo: Yield In a line mixture of E. tereti=rnis and E. torreliana, E. tereti=rnis has proved to be the more competitive of the two.

Ferguson, I.S. 1983. Plantation Management in Australia. New Zealand Journal of Forestry 28 (3): 327-338 . Australia: M3nagement An analysis of national forest policy in relation to plantation establishment and the need for understanding marketing issues; includes a statement of areas under various tree crops.

Ferguson, J.H.A., Hel.linga, G. and Alphen de Veer, F.J. van. 1949. Eenige gedachten over de Pinus kultur in Indonesie. (sane ideas aOOut the cultivation of pines in Indonesia.) Tectona 39: 383-387. Noted in In­donesian Forestry Al::.6tracts, PUiXlC, Wageningen, 1982. Al::.6tract 584 . Indonesia : M3nagement, cover crop To avoid the risks of pure plantations when establishing plantations of Pinus merkusii, mixing with SWietenia macrophylla on the plains, and with Agathis loranthifolia in the mountains on not too poor soils is discussed .

Florence, R.G. 1967 . Factors that may have a bearing upon the decline of productivity under forest monoculture. Australian Forestry 31 : 51-71. General: Soils Analysis of factors that may lead to a long tenn decline in productivity.

Florence, R.G. and Ianb, D. 1974. Influence of stand and site on Radiata pine litter in South Australia. New Zealand J ournal of Forest Science 4 (3): 302-310. Australia: Soils Litter accumulation related more to soil type than to site quality and to rate of decomposition than to rate of fall.

Francis, P . J . and Shea, G.K. 1987. Management of tropical and sub­tropical pines in Q.leensland . In Forest Management in Australia; Proceedings of a Conference of the Institute of Foresters of Australia pp 273-280. Australia : M3nagement .

Franzini , F . 1957 . Ies rel::oisement artificiels dans les sa vanes de la region de Pointe Noire . (Afforestation of savannah land in the Pointe Noire region.) Bois et Forets des Tropigues 53 : 25-32. Congo: Managernent Experiments in afforestation of savannas with Eucalyptus saligna, Eucalyptus camaldulensis and casuarina equisetifolia are described .

Friedrich, J .K. and DaWson, J .0. 1984. Soil nitrogen concentration and Juglans nigra grcMth in mixed plots with nitrogen-fixing Alnus, Elaeag­nus, Iespedeza and Robinia species . Canadian Journal of Forest Research 14 (6): 864-868. USA: Soils In a 14-year-old plantation with spacings of 3 . 7x4. 9 and 9. Sm, the highest total soil N concentration in top 30 an was under closely­spaced Elaeagnus and both spacings of Robinia (girdled). Walnut basal area was not strongly correlated with soil nitrogen concentration.

Friend, G.R. 1980. Wildlife conservation and softwood forestry in Australia : same considerations. Australian Forestry 43 (4): 217-224 . Australia : Wildlife Radiata plantations are specia lised and s:il!lplified habitats. They are :impoverished in that they lack diversity in wildlife. Animals without specialist requirements are least affected, even favoured, by planta­tions. Measures to counter this :impoverishment are discussed

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Ftivold, L.H. 1982. Edandhingsskorgens status i eurqpeiskt skogsbruk.(Status of mixed forests in European forestry.) Tidsskrift foerskogsbruk 90 (3): 250-261.Europe: Reviewing articleMbst investigations of the "mixed species effect" cannot positivelyrule out site differences. Investigations concluding that spruce mono-cultures lead to soil degradation deserve attention. Experience sug-gests certain mixtures raise timber quality. Pure stands may be moresensitive to calamities than mixed, stand vigour may also play a rolein this. Mixed stands are probably more wind resistant.

Fkivold, L.EL 1985. Mixed broadleaved stands - Sara silvicultural con-siderations. In: Broadleaves in Boreal Silviculture - An Obstacle or anAsset? Swedish University of Agricultural Sciences, Report 14.Boreal forests: Reviewing articleA "mixed species effect" cannot be ruled out. The effect is probablynot greater than a few percent. Data on the relationship betweenstability and diversity are few. Mixed stands may, in same cases, bemore stable than pure. Evidence regarding sustainability and mixturesis contradictory.

Garrido,14.A. and Poggiani,F. 1979. Caracteristicas silviculturais cincoespecies indigenas plantadas empovoamentospuros e mistos. (Silvicu-ltural characteristics of five indigenous species in pure and mixedstands.) Silvicultura en Sao Paulo 13/14 pp 33-44.Brazil: Management5-year growth statistics for Piptadenia macrocarpa, Astroniumurundura,Mcquinia polymorpha, Cblubrina rufa and Tabebuia impetiginosa grownpure and mixed. P.macrocarpa had better dbh and height growth than themixture as a group. Of the individual species only C.rufa andT.impetiginosa did better in mixture.

Geldenbuys, C.J. 1975. Die kunstmatige verstiging van inheemse Los in dieSuid-Rap. (The artificial establishment of indigenous forest in thesouthern Cape.) Bosbou in Suid Afrika 16: 45-53.South Africa: ManagementThe taungya system was used to establish ten species of the Capeindigenous forest. Stem number and survival was higher than in anadjacent forest under production management.

Gepp, B.C. 1976. Bird species distribution and habitat diversity in anexotic forest in south Australia. Australian Forestry 39 (4): 269-287.Australia: WildlifePine plantations, native forests and grasslands were compared as tobird habitats. Lowest diversity occurred in the interior of unthinnedplantations. The number of species in the plantations was almost thesame as in the native vegetation. The landscape mosaic seems to provideniches enough for most species in the area.

Gepp, B. 1985. Values of wildlife in forest plantations in the tropics andsouthern hemisphere. In Wildlife Management in the Forests and ForestryControlled Lands in the Tropics and Southern Hemisphere. ed J.Kikkawa.IUFRO Workshop held at University of Queensland, Australia.General: WildlifeConditions in plantations change. The pole stage (app. 20% of therotation) is the most uniform stage, and least suited to wildlife.Wildlife in plantations favours areas with native regeneration.Retention of islands or a mosaic of native species is helpful. Planta-tions on farm or grassland may raise diversity.

Gibson, I.A.S. and 'Tones, T. 1977. Mbnoculture as the origin of majorforest pests and diseases, especially in the tropics and southern

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Frivold, L.H. 1982. Blandningsskogens status i europeiskt skogsbruk. (Status of mixed forests in European forestry.) Tidsskrift foer skogsbruk 90 (3): 250-261 . Europe: Reviewing article M:Jst investigations of the "mixed species effect" cannot positively rule out site differences. Investigations concluding that spruce rrono­cultures lead to soil degradation deserve attention. Experience sug­gests certain mixtures raise timber quality. Pure stands may be rrore sensitive to calamities than mixed, stand vigour may also play a role in this. Mixed stands are probably rrore wind resistant.

Frivold, L.H. 1985. Mixed broadleaved stands - Sane silvicultural con­siderations. In: Broadleaves in Boreal SilViculture - An Obstacle or an Asset? SWedish University of Agricultural Sciences, Report 14. Boreal forests: Reviewing article A "mixed species effect" cannot be ruled out. The effect is probably not greater than a few percent. Data on the relationship between stability and diversity are few. Mixed stands may, in sare cases, be rrore stable than pure. Evidence regarding sustainability and mixtures is contradictory.·

Garrido,M.A. and Poggiani,F. 1979. Garacteristicas silviculturais cinco especies indigenas plantadas em ]XJvoamentos puros e mistos. (Silvicu­ltural characteristics of five indigenous species in pure and mixed stands.) Silvicultura em Sao Paulo 13/14 pp 33-44 . Brazil: M3nagement 5-year grCMth statistics for Piptadenia macrocaIpa, Ast=ium urundura, M:x:Juinia ]XJlynvrpha, Colubrina rufa and Tabel::Rlia impetiginosa grown pure and mixed. P.macrocaIpa had better dbh and height grCMth than the mixture as a group. Of the individual species only C.rufa and T . impetiginosa did better in mixture.

Geldenhuys, C.J. 1975. Die Jrunstmatige verstiging van inheemse]:os in die Suid-Kap. (The artificial establishment of indigenous forest in the southern cape . ) Bosbou in Suid Afrika 16: 45-53 . South Africa: Management The taungya system was used to establish ten species of the cape indigenous forest . stem number and survival was higher than in an adjacent forest under production management.

Gefp, B.C. 1976. Bird species distribution and habitat diversity in an exotic forest in south Australia . Australian Forestry 39 (4): 269-287. Australia: Wildlife Pine plantatiOns, native forests and grasslands were canpared as to bird habitats . ~st diversity oc=ed in the interior of unthinned plantations. The number of species in the plantations was alrrost the same as in the native vegetation. The landscape rrosaic seems to provide niches enough for rrost species in the area.

Gefp, B. 1985. Values of wildlife in forest plantations in the tropics and southern hemisphere. In Wildlife M3nagement in the Forests and Forestry Controlled Lands in the Tropics and Southern Hemisphere . ed J . Kikkawa . IUFRO Workshop held at University of Queensland, Australia . General: Wildlife Conditions in plantatiOns change. The pole stage (app. 20% of the rotation) is the rrost uniform stage, and least suited to wildlife. Wildlife in plantatiOns favours areas with native regeneration. Retention of islands or a rrosaic of native species is helpful. Planta­tions on farm or grassland may raise diversity.

Gibson, LA.S. and Janes, T. 1977. Monoculture as the origin of major forest pests and diseases, especially in the tropi cs and southern

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hemisphere. Origins of Pest, Parasite, Disease and Weed Problems. edCherrett, J.M and Sagar, G.R. Blackwell, Oxford (UK) pp 139-161.General: Environmental, pests and diseasesDiseases in monocultures are more numerous for species growing in theirnative range than for exotics. Plantation forestry allows for moreexpenditure on protection measures than other kinds of forestry.

Gilmour, D.A., Ingles, A. and MAharjan, N.R. 1989. Preliminary harvestingguidelines for community forests in Sindhu Palchok and KAbhrePalanchok. Technical Note 2/89, Nepal Australia Forestry Project, Kath-mandu 9p.Nepal: Management: SocialPrescriptions for the management, by village communities, of coppice-with-standards, mixed and single species high forest, including pine-broadleaved mixtures.

Gilmour, D. A., King, G. C., Applegate, G. B. and Mans, B. 1990.Silviculture of plantation forest in central Nepal to maximisecommunity benefits. Forest Ecology and Management 32: 173-186.Nepal: Management. Yields. SocialA trial of management techniques for Pinus roxburghii plantations inwhich rrti.ced broad leaved species (predominantly Schima wallichii) haveregenerated. The objective has been to devise techniques that willresult in sustainable yield of products that the villagers require.

Gonggrijp, L. 1929. Ecelbewuste kunstmatige mengir2g van djati enwi/dhout.(Artificial mixing of teak with other trees.) Tectona 22:1287-1294. Noted in Indonesian Forestry Abstracts, PUDOC, Wageningen,1982. Abstract 592.Indonesia: EconomyThe author feels that the necessity of mixtures is unproven, and thatthe economy of mixing has received too little attention.

Graham, RIC 1945. Notes on the ylowing of cypress timber on farms. EastAfrica Agricultural Journal 11: 132-139.Kenya: Soils. Environmental, pests and diseasesGrevillea robusta is considered suitable for mixture with Cupressusmacrocarpa. This is done to avoid hazards with monoculture e.g. soildegradation, pests and diseases.

Graham, R.M. 1949. Plantation management order no. 5. Grevillea robusta.Forest Department, Colony and Protectorate of Kenya.Kenya: ManagementConsiderable quantities of Grevillea robusta have been grown in mixturewith cypresses and other species. The species is worth growing for itsown sake. A regime is suggested.

Granert, W. G. and Cadampog, Z. 1980. Leucaena as a nurse tree. LeucaenaNews Letter 1: 21.Philippines: ManagementTeak and mahogany (SWietenia macrophylla) planted with ipil-ipil(Leucaena leucocephala). No effect on the growth of teak was observed,but it was considered straighter. No growth improvements noted formahogany either, but incidence of tip borer attacks was reduced underipil-ipil.

Gray, B. 1972. Economic tropical entomology. Annual review of Entomology17: 313-353.Tropics: Pests

Grijpma, P. 1973. Immunity of Tacna ciliata Roem. var australis(F.v.M)C.D.C. and Rhaya ivorensis A.Chev. to attacks of hypsipylagrandella (Zeller) in Turriaiba, Costa Rica. In Studies on theShootborer hypsipyla grandella (Zeller) Lep. Pyralidae Vol. I Inter-

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hemisphere. Origins of Pest, Parasite, Disease and weed Problems . ed Cherrett, J.M and Sagar, G.R. Blackwell, Oxford (UK) pp 139-161. General: Environmental, pests and diseases . Diseases in IlOnocultures are 1l'Dre numerous for species growing in their native range than for exotics . Plantation forestry allows for IlOre expenditure on protection measures than other kinds of forestry.

GilJDCAIr, D.A., Ingles, A. and Maharjan, M.R. 1989. Preliminary harvesting guidelines for oarnmunity forests in Sindhu Palchok and Kabhre Palanchok. Technical Note 2/89, Nepal Australia Forestry Project, Kath­mandu 9p. Nepal: Management: Social Prescriptions for the management, by village communities, of coppioe­with-standards, mixed and single species high forest, including pine­broadleaved mixtures.

GilJDCAIr, D.A., King, G.C., Afplegate, G. B. and Mohns, B. 1990. Silviculture of plantation forest in central Nepal to maximise community benefits. Forest Ecology and Management 32: 173-186. Nepal: Management . Yields. Social A trial of management techniques for Pinus roxburghii plantatiOns in which mixed broad leaved species (predaninantly Schima wallichii) have regenerated. The objective has been to devise techniques that will result in sustainable yield of products that the Villagers require .

Garqp:ijp, L. 1929. Doelbewuste kunstmatige menging van djati en wildhout. (Artificial mixing of teak with other trees.) Tectona 22 : 1287 -1294. Noted in Indonesian Forestry Abstracts, PUIXlC, Wageningen, 1982 . Abstract 592. Indonesia : Econany The author feels that the necessity of mixtures is unproven, and that the econany of mixing has received too little attention.

Graham, R.M. 1945. Notes on the growing of cypress timber on fanns . East Africa Agricult~dl Journal 11: 132-139. Kenya: SOils. Environmental, pests and diseases Grevillea robusta is considered suitable for mixture with CUpressus macr=a.rpa. This is done to avoid hazards with 1l'Dnoculture e .g . soil degradation, pests and diseases.

Graham, R.M. 1949. Plantation management order no. 5 . Grevillea robusta. Forest Department, Colony and Protectorate of Kenya. Kenya: Management Considerable quantities of Grevillea robusta have been grown in mixture with cypresses and other species. The species is worth growing for its own sake. A regime is suggested.

Granert, W.G. and CadanJx'g, Z. 1980. I.eucaena as a nurse tree. Leucaena News Letter 1: 21. Philippines: Management Teak and mahogany (SWietenia macropbylla) planted with ipil-ipil (I.eucaena leucocephala). No effect on the growth of teak was observed, rut it was considered straighter. No growth :iIrq:>rovements noted for mahogany either, rut incidence of tip berer attacks was reduced under ipil-ipil.

Gray, B. 1972. Econanic tropical entanology . Annual review of Entanology 17: 313-353. Tropics: Pests

Grijpna, P. 1973. Irrrnunity of Toona ciliata Roem . var australis (F.v.M)C.D .C. and Khaya ivorensis A.Chev. to attacks of Hypsipyla grand ella (Zeller) in Tu=ialba, Costa Rica. In Studies on the Shootbcrer Hypsipyla grandella (Zeller) Lep. Pyralidae Vol. I Inter-

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American Institute for Cooperation on Agriculture (IICA) Misc. Pub. 101p 18-25.Tropics: Pests11.grandélla (New World) and 11.robusta (Old World) appear to herelatively specific to indigenous Meliaceae; SWietenia macrophylla inIndia and Sri Lanka and Rhaya ivorensis in Martinique are exceptions.

Grijpma, P. and Ramaido, Et. 1973. Tbona spp posibles alternativas para elproblem del Larrendorhypsipyla grandélla dé los likliaceae en AmericaLatina. In Studies on the Shootborer hTpsipyla (Zeller) Lep. PyralidaeVol. I. Inter-American Institute for Cooperation on Agriculture (IICA)Misc. Pub. 101 p 3-17.Central America: PestsT.ciliata though heavily attadked by liroLusta in Australia is notattadked by 11.grandella in Costa Rica.

Groulez, J. 1975. Notes sur les plantations dé conversion dans les fOrétstropicaleshignides. (A, note on conversion plantations in moist tropicalforests.) Bois et Forêts des Tropiques 162: 3-26.Tropics: ManagementDiscusses the pros and cons of conversion plantations (that is,

replacing the natural forest) and despite problems of costs and lack ofprofitability considers them promising. 26,000 ha Auctsneaklaineana inGabon, 6,000 ha Terminalia superta in Congo, 50,000 ha anelina inBrazil.

Grutterink, E. J. 1930. Verslag van de excursie op 21 maart 1930 naar déLoscomplexen Natoetoetoek, Fantodomas en de sagerij Sapoeran der Firma

Nélle. (Report of the excursion on 21March 1930 to Watoetoetoekand Pantodomas forest complexes and the Dapuran sawmill of the firmJ.v.d. Welle.) Tectona 23: 633-640. Noted in Indonesian Forestry Abst-racts, PUDOC, Wageningen, 1982. Abstract 593.Indonesia: SoilsMixtures of shade-tolerant species are to be preferred from thehydrological point of view. Planting light demanders means that a goodprotection forest will not be formed.

GUizoi, P. 1985. Les plantations m6langees. Ecole Nationale du GénieRural des Eaux et des Forêts, France, pp. 18.France: ManagementA survey of mixed stands in France. Advantages of mixing arelisted, and suitable mixtures recommended.

Guizol, P. 1983/85. Les rdantations mélangees. Mixed plantations. Eléve-Ingénieur Civil de Forêts, Promotion. Ecole Nationale du Genie Rural,des Eaux et des Foréts.France: ManagementA survey of mixed stands in France. Comparisons are nade to see whatmixtures gave the best results. Objectives of mixing are discussed.

Hagg, A. 1988. Loensamheten avbjoerkinblandningi barrskog. (The

profitability of a birch admixture in coniferous forests.) SwedishUniversity of Agricultural Sciences, Department of Forest Products,Report No. 208.Sweden: EconomyIt is profitable to retain birches to increase stand density. Birchadmixture Laises the quality of pines. Selective removals of birch inmature stands can be increased. Costs for this are counterbalanced bylower future tending costs.

Hagg, A. 1989. Ejoerkens inverkan paa tallens grengrovlek ochgrenrensningi blandadebestaand. (The influence of the birch upon the

93

American Institute for c=peration on Agriculture (IrCA) Misc. Pub. 101 P 18-25 . Tropics : Pests H. grandella (New World) and H.robusta (Old World) appear to be relatively specific to indigenous Meliaceae; SWietenia macrophylla in India and Sri Lanka and Kbaya ivorensis in Martinique are exceptions.

Grijpna., P. and Ramaldo, R. 1973 . Toona spp posibles alternativas para el problem del b3rrendor Hypsipyla grandella de los M2liaceae en America Latina. In Studies on the Shootl::orer Hypsipyla (Zeller) I.ep. Pyralidae Vol. 1. Inter-American Institute for C=peration on Agriculture (IrCA) Misc. Pub. 101 P 3-17 . Central America: Pests T.ciliata though heavily attacked by H.rob.zsta in Australia is not attacked by H. grandella in Costa Rica .

Groulez , J . 1975. Notes sur les plantations de conversion dans les forets tropicales humides. (A note on conversion plantations in IrDist tropical forests . ) Bois et Fbrets des Tropiques 162: 3-26. Tropics: Manag~t Discusses the pros and cons of conversion plantatiOns (that is, replacing the natural forest) and despite problems of costs and lack of profitability considers them pranising . 26,000 ha Aucumea klaineana in Gabon , 6 , 000 ha Terminalia superl:a in Congo, 50,000 ha Gnelina in Brazil .

Grutt erink, B. J . 1930 . Verslag van de excursie op 21 maart 1930 naar de boscaIfJlexen Watoetoetoek, Pantcxiana5 en de sagerij Sapoeran der Finna. J. v.d. Welle. (Report of the excursion on 21 March 1930 to Watoetoetoek and Pantodamas forest complexes and the Dapuran sawmill of the finn J.v .d . Welle . ) Tectona 23: 633-640. Noted in Indonesian Forestry Abst­racts, PUDJC , Wageningen, 1982 . Abstract 593. Indonesia : SOils Mixtures of shade-tolerant species are to be prefe=ed fran the hydrological point of view. Planting light demanders means that a good protection forest will not be formed.

Gil; zal , P. 1985. Les plantations melangees . Ecole Nationale du Genie Rural des Eaux et des Forets, France, pp. 18 . France : Management A survey of mixed stands in France . Advantages of mixing are listed, and suitable mixtures recommended.

Gil; zal, P . 1983/85 . Les plantatiOns melangees . Mixed plantations . Eleve­Ingenieur Civil de Forets , Promotion . Ecole Nationale du Genie Rural, des Eaux et des Forets. France : Management A survey of mixed stands in France. Ccrnparisons are made to see what mixtures gave the best results. Objectives of mixing are discussed.

Hagg, A. 1988. Loensamheten av bjoerkinblandning i b3rrskog. (The profitability of a birch admixture in coniferous forests . ) SWedish University of Agricultural Sciences , Department of Forest Products, Report No . 208. Sweden: Econany It is profitable to retain birches to increase stand density . Birch admixture raises the quality of pines. Selective removals of birch in mature stands can be increased. Costs for this are counterbalanced by lower future tending costs.

Hagg, A. 1989 . Bjoerkens inverkan paa tallens grengrovlek och grenrensning i blandade bestaand. (The inf luence of the birch upon the

94

branch diameter and the self-pruning of pine trees in mixed stands.)Swedish University of Agricultural Sciences, Department of Forest Pro-ducts, Report NO. 208.Sweden: Management. EconomyIncrease in stand density caused by naturally regenerated birchesresults in a lower branch diameter of the butt log. If birches areretained after cleaning operations this effect is enhanced and self-pruning increased.

Hagg, A. 1990. Loensamheten av att anvaenda sjaelvfOerynyLad Ljoerk foerkvalitetsdaning av planterad tall. (The profitability of using self-regenerated birch for shaping the quality of the planted pine.) SwedishUniversity of Agricultural Sciences, Department of Forest Products,Report No. 214.Sweden: Economy. ManagementBranch diameter of pines depends on stand density, not on mixtures.Retaining 1400 and 7900 birches/ha. is compared. Calculations shcm thatretaining birch is profitable, this is enhanced hgfertilization after50 years. For the regime of 7900 birches to be the more profitable, itmust produce 38% more of prime grade timber than the other.

Hansen, E.A. and Dawson, J.O. 1982. Effect of Alnus glutinosa on hybrid.Ropulus height growth in a short rotation intensively culturedplantation. Forest Science 28 (1): 49-59.USA: Yield. SoilsIn a 3-year-old 'immixture, poplar height increased with the share ofalder, and decreased with distance between the two species. In aneighbouring stand significant N accretion occurred up to 15 an fromalder stems.

Barencarspel, W. van 1908. Menging van lichtbehoeftige met sterk Le-schaudwende houtsoorten. (The mixing of light demanding tree specieswith tree species producing shade.) Tectona 1: 182-184. Noted in In-donesian Forestry Abstracts, PUDOC, Wageningen, 1982, Abstract 594.Indonesia: ManagementGroup mixing CUpressus and Casuarina with species that will not growtall is to be preferred to individual mixing.

Harrington, C.A. 1982. Sitka alder, a candidate for mixed stands.

Canadian Journal of Forest Research 12 (1): 108-111.Canada: ManagementAnalysis of height growth pattern (max. 5m in 14 years) suggests thatAlnu sinuata may be a suitable nurse for Pseudotsuga menziesii, butadvance planting of large P.menziesii is the stock advisable on poorsites.

Hart, H.M.J. 1931a. Gemengde djaticulturen, deel I+11. (Mixed teakplantations Part I and II.) Meded. P.v.h.B. 24: pp 170 (part I) and pp400 (part II). NOted in Indonesian Forestry Abstracts, PUDOC, Wage-ningen, 1982, Abstract No. 602.Indonesia: Management. SoilsIt is concluded that mixing is favourable only under specialcircumstances. Inmost cases examined mixing proved to be unfavourable.

Hart, 1931b. Gemengde djaticulturen. (Mixed teak plantations(proposal).) Tectona 24: 88-107. Noted in Indonesian ForestryAbstracts, PUDOC, Wageningen, 1982. Ahstract 603.Indonesia: ManagementMbst of the supposed beneficial effects of mixing have proved to be un-founded. Intensive soil cultivation stimulates the growth of youngteak. Interplanting of leucaena may have the same effect.

94

branch diameter and the self-pruning of pine trees in mixed stands.) SWedish University of Agricultural Sciences, Department of Forest Pro­ducts, Report No. 208. Sweden: Management. Econany Increase in stand density caused by naturally regenerated birches results in a lCMer branch diameter of the butt log. If birches are retained after cleaning operations this effect is enhanced and self­pruning increased.

Hiigg, A. 1990. IAJensamiJeten avatt anvaenda sjaelvfoeryngrad bjoerk foer kvalitetsdaning av planterad tall. (The profitability of using self­regenerated birch for shaping the quality of the planted pine.) SWedish University of Agricultural Sciences, Department of Forest Products, Report No. 214. Sweden: Econany. Management Branch diameter of pines depends on stand density, not on mixtures. Retaining 1400 and 7900 birches/ha. is canpared. calculations shcM that retaining birch is profitable, this is enhanced by fertilization after 50 years. For the regime of 7900 birches to be the rrore profitable, it must produce 38% rrore of prime grade timber than the other.

Hansen, E.A. and Dawson, J.D. 1982. Effect of Alnus glutinosa on hybrid Fbpulus height growth in a short rotation intensively cultured plantation. Forest Science 28 (1): 49-59. USA: Yield. Soils In a 3-year-old line mixture, poplar height increased with the share of alder, and decreased with distance between the two species. In a neighbouring stand significant N accretion oc=ed up to 15 an fran alder sterns.

Harencarspel, W. van 1908. Menging van lichtbehoeftige met sterk be­schaudwende houtsoorten. (The mixing of light demanding tree species with tree species producing shade.) Tectona 1: 182-184. Noted in In­donesian Forestry Abstracts, PUIX:lC, Wageningen, 1982, Abstract 594. Indonesia: Management Group mixing CUpressus and casuarina with species that will not grow tall is to be preferred to individual mixing.

Harrington, C.A. 1982. Sitka alder, a candidate for mixed stands. canadian Journal of Forest Research 12 (1): 108-111. canada: Management Analysis of height growth pattern (max. 5m in 14 years) suggests that Alnus sinuata may be a suitable nurse for Pseudotsuga menziesii, but advance planting of large P.menziesii is the stock advisable on poor sites .

Hart, H.M.J. 1931a. Gelrengde djaticulturen, deel I+II. (Mixed teak plantations Part I and II.) Meded. P.v.h.B. 24: pp 170 (part I) and pp 400 (part II). Noted in Indonesian Forestry Abstracts, PUIX:lC, Wage­ningen, 1982, Abstract No. 602. Indonesia: Management. Soils It is concluded that mixing is favourable only under special cirCUlllStances. In rrost cases examined mixing proved to be unfavourable.

Hart, H.M.J. 1931b. Gelrengde djaticulturen. (Mixed teak plantations (proposal).) Tectona 24: 88- 107. Noted in Indonesian Forestry Abstracts, PUIX:lC, Wageningen, 1982. Abstract 603. Indonesia: Management M;)st of the supposed beneficial effects of mixing have proved to be un­founded. Intensive soil cultivation stimulates the growth of young teak. Intel:planting of leucaena may have the same effect.

95

Hart, HM.J. 1931c. Gemengde djaticulturen. (Mixed teak plantations(explanation and discussion) ) Tectona 24: 488-511. Noted in IndonesianForestry Abstracts, PUDOC, Wageningen, 1982. Abstract 604Indonesia: ManagementThe poorer the soil the more adverse is the influence of mixing.Natural pruning is better in pure teak plantations.

Hart, H.M.J. and Nolt6e, A.C. 1927. Verjonging en verpleging van dendjati. (Regeneration and tending of teak.) Tectona 20: 199-213. Notedin Indonesian Forestry Abstracts, PUDOC, Wageningen, 1982. Abstract 568Indonesia: ManagementA historic survey of regeneration techniques for teak.

Hasan, SM., al Saraf, 11.J. and Khalil, 14.T. 1980. (Comparative studieson the growth of Pinus brutia in pure and mixed plantations.) Mesopo-tamia Journal of Agriculture (from Forestry Abstracts Vol.42 2949).Iraq: YieldPure Pinus brutia was compared to P.brutia inteiplanted with Acaciafarnesiana.After three growing seasons height growth was significantlyhigher in the mixed stand.

Heald, R.C. and Haight, R. 1979. A new approach to uneven-aged silvicul-ture and management of mixed conifer-oak forests. California Agric. 33(5): 20-22.ManagementAmethod of identification of vegetation types is presented. Managementis directed at maintaining these types.

Heilman, P. and Stettler, R.F. 1985. Mixed short rotation of red alder andblackcottonwocd: Growth, coppicing, nitrogen fixation and allelopathy.Forest Science 31 (3): 607-616.North America: Soils. YieldBeneficial effects of mixing with red alder cannot be ruled out by thisstudy.

Henry, P.W.T. 1960. The Akilla plantation. Inform. Bull. Dep. For. Res.Nigeria 9: 1-4.Nigeria: ManagementOf the species tried for planting in tropical lowland rain forest, thegreatest success has been achieved with Nauclea diderichli, pure or in5/1 mixture with ilkliaceae.

HeYbrodk, H.M. 1980. Mbnoculture versus mixture: interactions betweensusceptible and resistant trees in a mixed stand. In: Resistance todiseases and pests in forest trees, Proceedings of the ThirdInternationalWorkshop on the Genetics of Hbst-Parasite Interactions inForestry, Wageningen, September 1990. PUDOC, 1982. pp 20.General: Environmental, pests and diseasesMixing of hosts and non-hosts to diseases may be effective, but as itoften means mixing species, it may entail silvicultural problems.Mixing of genotype is a poor substitute for breeding for resistance.

Heybroek, H.M. and Tbl, G. van 1985. Experiences with genetically mixedforest plantations in the Netherlands. Forest Ecology and Management12: 155-162.The Netherlands: ManagementMixtures are difficult to maintain over rotations, they often developinto more or less pure stands, or mosaics thereof. In clonal forestry,a mosaic of pure stands is preferable to individual mixtures.

Hirano, R.T. 1990. Propagation of Santalum, Sandalwood tree. In

Proceedings of the Symposium on Sandalwood in the Pacific, April1990, Honolulu, Hawaii. US Department of Agriculture, Forest Service,

General Technical Report PSW-122. p43-45.

95

Hart, H.M.J. 1931c. Ganengde djaticulturen . (Mixed teak plantations (explanation and discussion).) Tectona 24: 488-511. Noted in Indonesian Forestry Abstracts, PUIXX:, Wageningen, 1982. Abstract 604 Indonesia: Management The poorer the soil the IIDre adverse is the influence of mixing. Natural p=ing is better in pure teak plantations.

Hart, H.M.J. and Noltee, A.C. 1927. Verjonging en verpleging van den djati. (Regeneration and tending of teak.) Tectona 20: 199-213. Noted in Indonesian Forestry Abstracts, PUIXX:, Wageningen, 1982. Abstract 568 Indonesia : Management A historic survey of regeneration techniques for teak.

Hasan, S.M., al Saraf, M.J. and Khalil, M.T. 1980. (Ccrrg;Jarative studies on the grCMth of Pinus brutia in pure and mixed plantations.) Mesopo­tamia Journal of Agriculture (fran Forestry Abstracts Vo1.42 2949). Iraq: Yield Pure Pinus brutia was canpared to P.brutia interplanted with Acacia farnesiana . After three grCM"ing seasons height grCMth was significantly higher in the mixed stand.

Heald, R.C. and Haight" R. 1979. A new- approach to uneven-aged silvicul­ture and management of mixed conifer-oak forests. California Agric. 33 (5): 20-22. Management A method of identification of vegetation types is presented. Management is directed at maintaining these types.

Heilman, P. and stettler, R.F. 1985. Mixed short rotation of red alder and black cottonwood: GrCMth, coppicing, nitrogen fixation and allelopathy. Forest Science 31 (3): 607-616. North America: Soils. Yield Beneficial effects of mixing with red alder cannot be ruled out by this study.

Henry, P.W.T. 1960. The Akilla plantation . Inform. Bull. Dep. For. Res. Nigeria 9: 1-4. Nigeria: Management Of the species tried for planting in tropical lCM"land rain forest, the greatest success has been achieved with Nauclea diderichii, pure or in 5/1 mixture with M21iaceae.

Heybroek, H.M. 1980. M:lnoculture versus mixture: interactions between susceptible and resistant trees in a mixed stand. In: Resistance to diseases and pests in forest trees, Proceedings of the Third International Workshop on the Genetics of Host-Parasite Interactions in Forestry, Wageningen, September 1990. PUIXX:, 1982. pp 20. General: Envirorunental, pests and diseases Mixing of hosts and non-hosts to diseases may be effective, but as it often means mixing speCies, it may entail silvicultural problems . Mixing of genotype is a poor substitute for breeding for resistance.

Heybroek, H.M. and Tol, G. van 1985. Experiences with genetically mixed forest plantations in the Netherlands. Forest Ecology and Management 12: 155-162. The Netherlands: Management Mixtures are difficult to maintain over rotations, ' they often develop into IIDre or less pure stands, or rrosaics thereof . In clonal forestry, a rrosaic of pure stands is preferable to individual mixtures.

Hirano, R.T. 1990. Propagation of Santalum, Sandalwocd. tree. In Proceedings of the Symposium on Sandalwocd. in the Pacific, April

1990, Honolulu, Hawaii. US Department of Agricul ture, Forest Service, General Technical Report PSW-122 . p43-45.

96

Hawaii: ManagementA brief description of Sandalwood trade in Hawaii and notes on nurserypractice.

Ikemori, Y.K. 1990. Genetic variation in characteristics of EUcalyptusgrandis (Hill) Maiden raised frcra micro-propagation, macro-propagationand seed: D.Phil thesis, University of Oxford (UK).Brazil: YieldsAverage yield has been raised from 30 to 45m3/h.a/yr with anticipationof raising to 55m3. Specific wood consumption should be reduced from4.2m3/tonnes pulp to 3.7m3.

Indian Forest Service 1934, Fourth Silvicultural Conference, Item 8.

Debra Dun, India.India: ManagementA document discussing mixed plantation at sane length.

Indian Forest Service 1939. Fifth Silvicultural Conference, Item 14,

Dehra Dun.India: ManagementThis document contains one of the most detailed discussions encounteredon the subject.

Ingles, A. 1990. Demonstration of forest management options in shrUblandsand mixed pine - broadleaf forests. Discussion Paper of Nepal-AustraliaForestry Project, Kathmandu. pp 47.Nepal: Social. Management. YieldsManagement options for different vegetation types are suggested.

Ishibasbi, H. 1987. The development and problems in the anti-erosionplantations in Japan. Mitteilungen der Forstlichen Bundes-Versuchanstalt, Wien, No. 138.Japan: SoilsTerraces are planted with a mixture of Pinus thunbergii and Alnupendula. Big areas have developed into stands of little or no pine,which erode and need intensive treatment; the regime is described.

Japing, H. W. about 1931. Het verjongingsonderzoek van sandelhout (Santalumalbum) qp Java. (Research on the regeneration of sandalwood (Santalumalbum) in Java. UnpUblished. Noted in Indonesian Forestry Abstracts,PUDOC, Wageningen, 1982. Abstract 638.Indonesia: ManagementBrief presentation of trials to raise sandalwood in mixture.

Jones, A.D., Davies, H. I. ami Sinden, J.A. 1990. Relationships betweeneucalypt diebadk and land use in southern New England, New SouthWales. Australian Forestry 53 (1): 13-23.Australia: Environmental: Pests and diseasesAn analysis of a time series of aerial photographs using as-sociations in multiway tables. No clear relationship cOuld bedetected between increased species diversity and reduction indieback.

Jones, E.W. 1945. Structure and reproduction of the virgin forests of thenorth temperate zone. New Phytologist 44: 130-148.North temperate: Ecology

Jones, E.W. 1965. Pure conifers in central Europe - A review of sane oldand new work. Journal of Oxford University Forestry Society 13: 3-15Europe: ManagementImportant works concerning the subject are reviewed.

Jones, P.D ami Wigley, T.M.L. 1990. Global warming trends. ScientificAmerican 263 (2): 66-73.General: Environmental

96

Hawaii: Management A brief description of Sandalwood trade in Hawaii and notes on nursery practice.

IkeJDri, Y.K. 1990. Genetic variation in characteristics of Eucalyptus grandis (Hill) Maiden raised fran micro-propagation, macro-propagation and seed: D.Phil theSiS, University of OXford (UK). Brazil: Yields Average yield has been raised fran 30 to 45m3/ha/yr with anticipation of raising to 55m3 • Specific wood consumption should be reduced fran 4. 2m3/tonnes pulp to 3. 7m3

•

Indian Forest Service 1934. Fourth silvicultural Conference, Item 8. Dehra Dun, India. India: Management A docurrent discussing mixed plantation at sane length.

Indian Forest Service 1939. Fifth silvicultural Conference, Item 14, . Dehra Dun. India: Management This document contains one of the rrost detailed discussions encountered on the subject.

Ingles, A. 1990. Demonstration of forest management options in shrublands and mixed pine - broadleaf forests. Discussion Paper of Nepal-Australia Forestry Project, Kathmandu. pp 47. Nepal: 8=ial . Management . Yields Management options for different vegetation types are suggested.

Ishibashi, H. 1987. The developnent and problems in the anti-erosion plantations in Japan. Mitteilungen der Forstlichen Bundes­Versuchanstalt, Wien, No. 138 . Japan : Soils Terraces are planted with a mixture of Pinus tbunbergii and Alnus pendula. Big areas have developed into stands of little or no pine, which erode and need intensive treabnent; the regime is described.

Japing, H.W. about 1931. Het verjongingsonderzoek van sandelhout (Santalum album) op JaM'!. (Research on the regeneration of sandalwood (Santalum album) in Java. Unpublished. Noted in Indonesian Forestry Abstracts, PUL'OC, Wageningen, 1982. Abstract 638. . Indonesia: Management Brief presentation of trials to raise sandalwocd in mixture.

Janes, A.D., Davies, H. I. and Sinden, J .A. 1990. Relationships between eucalypt dieback and land use in southern New England, New South Wales. Australian Forestry 53 (1): 13-23. Australia: Environmental: Pests and diseases An analysis of a time series of aerial photographs using as­sociations in multiway tables. No clear relationship cOuld be detected between increased species diversity and reduction in dieback.

Jones, E.W. 1945. Structure and reproduction of the virgin forests of the north terrperate zone. New Phytologist 44 : 130-148 . North terrperate : Ecology

Janes, E.W. 1965. Pure conifers in central Europe - A review of sane old and new work. Journal of OXford University Forestry 8=iety 13: 3-15 Europe: Management Important works concerning the subject are reviewed .

Janes, P.D and Wigley, T.M.L. 1990. Global warming trends. Scientific American 263 (2): 66-73 . General: Environmental

97

A "greenhouse" mathematical model has predicted that the warming in thelast century should have been .5 to 1.3° C and will be +4° C by the year2050. The model does not fit the facts as known exactly - 1920-40warmer than predicted; 1940-70 cooler.

Jonsson, B. 1961-62. an Larrbiandskogens produktion. (Yield of mixedconiferous forests.) Meddelanden fran statens skogsforskningsinstitut,50

Sweden: YieldResults indicate that mixtures affect yield. The effect is greatest onsites suited to both Pinus silvestris and Picea abies. In eitherdirection the effect diminishes, finally becoming negative.

jardan, C.F. and Farnworth, E.G. 1982. Natural versus plantation forests.Acase study of land reclamation strategies for the humid tropics. En-vironmental Management 6 (6): 485-492.Puerto Rico: YieldAfter four decades the productivity of the natural regeneration plot inthe experiment was higher or equal to that of the plantation.

Kaeokamnerd, W.. 19910 Travel Report to People's Republic of China.Mimeographed pp 60. UNDP/FAO/SIDA/RFD Project THA/86/016, Royal ForestDepartment, Bangkok.China: ManagementMixtures of Eucalyptus camaldulensis and E. exserta with Acacia auri-culiformis in alternate rows to improve soils and coppices noted.

Kageyama, BiellA, L.C. ami Palermo, A. 1990. Plantacoes mistas cornespecies nativas fins de protecao e reser vatorios.Paper presented to6th Congresso Florestal Brasileiro, Campos do Jordao, Sao Paolo,Mimeograph 11 p.Brazil: ManagementAnalysis of one year old mixed plantations. Silvicultural performance,height growth, is correlated to ecological groups of secondary succes-sion.

Kanowski, P. J. ami Savill, P. S.. with Adlard, P. G., Burley, J., EVans, J.,Palmer, J.R., ami Wbod, P.J. 1990. Plantation forestry. World Bank

Forestry Policy. Issues Paper. Oxford Forestry Institute.General: Soils. Environmental, pests and diseasesSecond rotation decline of the kind observed in South Australia can be.avoided by appropriate silviculture and tree breeding.

Kawahara, T. ami Yamamoto, K. 1986. (Studies on mixed stands of akamatsu(Pinus densiflora) and hinoki (Chamaecyparis obtusa) (III) Stem volumeof mixed stands.) Journal of Japanese Forestry Society 68 (8): 327-332.Japan: YieldHinoki height is equal in mixed and pure stands, diameter and treevolume greater in pure. Total stem volume is greater in mixed standsthan pure stands of either species.

Kawahara, T., Sato, A-, Takeuchi, I., Tadaki, Y. and Hatiya, K. (1981).Litter fall and its decomposition in a mixed stand of Japanese larch(flarixleptolepis) and hinoki (Chamaecyparisobtusa). Bulletin Forestryand Forest Products Research Institute, Japan. No.313: 79-91.Japan: SoilsLeaf decomposition was faster for mixed leaves than for either speciesalone

Keating, W.G. 1981. Utilization of mixed species through grouping andstandards. kistralian Forestry 43 (4): 233-244.Australia: ManagementThe author recommends grouping of timbers into strength groups based onthe requirements for structural materials to overcome the problem of

97

A "greenhouse" mathematical rocdel has predicted that the warming in the last century should have been .5 to 1. 30 C and will be +40 C by the year 2050. The rocdel does not fit the facts as known exactly - 1920-40 waLmer than predicted; 1940-70 cooler.

Jonsson, B. 1961-62. On b3.rrblandskogens prcxiuktion. (Yield of mixed coniferous forests . ) Meddelanden fran statens skogsforskningsinstitut, 50. SWeden: Yield Results indicate that mixtures affect yield. The effect is greatest on sites suited to both Pinus silvestris and Picea abies. In either direction the effect diminishes, finally becoming negative.

Jordan, C.F. and Faznworth, E.G. 1982. Natural versus plantation forests. A case study of land reclamation strategies for the humid tropics. En­virormmtal Managerrent 6 (6): 485-492. Puerto Rico: Yield After four decades the productivity of the natural regeneration plot in the experiment was higher or equal to that of the plantation.

KaeokaImerd, W. 1991. Travel Report to People's Republic of China. Milreographed pp 60 . UNDP /FAO/SIDA/RFD Project THA/86/016, Royal Forest Depar1:Irent, Bangkok. China: Managerrent Mixtures of Eucalyptus camaldulensis and E. exserta with Acacia auri­culifoLmis in alternate rows to improve soils and coppices noted .

Kageyama, P.Y., Biella, L.C. and PaleJllD, A. 1990. Plantacoes mistas can especies nativas fins de protecao e reser vatorios. Paper presented to 6th Congresso Florestal Brasileiro, campos do Jordao, Sao Paolo, Milreograph 11 p. Brazil: Managerrent Analysis of one year old mixed plantations. Silvicultural performance, height grCMth, is correlated to ecological groups of secondary succes­sion.

Kanowski, P.J. and Savill, P.S. with Mlard, P.G., Burley, J., Evans, J., Palmer, J.R., and Wood, P.J. 1990. Plantation forestry . World Bank

Fbrestry Policy. Issues Paper. Oxford Forestry Institute. General: Soils. Envirormmtal, pests and diseases Second rotation decline of the kind observed in South Australia can be

,avoided by appropriate silviculture and tree breeding. Kawahara, T. and YamaDDto, K. 1986. (Studies on mixed stands of akamatsu

(Pinus densiflora) and hinoki (Chamaecyparis obtusa) (III) Stem volurre of mixed stands.) Journal of Japanese Forestry Society 68 (8): 327-332. Japan: Yield Hinoki height is equal in mixed and pure stands, diameter and tree volurre greater in pure. Total stem volurre is greater in mixed stands than pure stands of either species.

Kawahara, T., Sato, A., Takeuchi,!., Tadaki, Y. and Hatiya, K. (1981). Litter fall and its deoomposition in a mixed stand of Japanese larch (Larix leptolepis) and hinoki (Chamaecyparis obtusa). Bulletin Forestry and Forest Products Research Institute, Japan. No.313: 79-91. Japan: Soils Leaf deoomposition was faster for mixed leaves than for either species alone.

Keating, W.G. 1981. Utilization of mixed species through grouping and standards . Australian Forestry 43 (4) : 233-244. Australia: Managerrent The author recarmends grouping of timbers into strength groups based on the requirerrents for structural materials to overcame the problem of

98

marketing mixed species. This requires good knowledge of the charac-teristics of each species and effective grading techniques.

Reeves, A. 1966. Sane evidence of loss of productivity with successiverotations of Pinus radiata in the south east of South Australia.Australian Forestry 30; 51-63.Australia: YieldFirst rotation felled at 24.5 years after a fire, second rotationassessed at 9.5 years. Commonly a drop of 1 - 2 Site Quality classes,sometimes as much as 4 classes.

Kelty, M.J. 1989. Productivity of New England hemlock/hardwood stands asaffected by species composition and canopy structure. Forest Ecologyand Management 28: 237-257.USA: YieldHemlock presence resulted in lower stoCking of hardwoods in mixedstands (30%) as well as lower volume (20%) and 5 year increment (14%)of the hardwoods. Total stocking increased (65%) as well as volume(27%) and increment (18%). Silvicultural gains are better conditionsfor regeneration and less epicormics.

Kemp, R.H. 1992. The conservation of genetic resources in managed tropicalforests. Unasylva 43 (169): 34 - 40.

Kerik, G.K. 1990a. The silviculture of mixed species stands in Germany. InEcology of Mixed Stands of Trees. British Ecological Society and IUFRODiv S2.01 Symposium, Edinburgh.Germany: ManagementClear objectives of mixtures, knowledge of sites and of growing ratesof coMbining species are indispensable. The selection forest is oftenseen as an ideal, but its possibilities get over estimated. 672 mixedstand types identified.G.K. 1990b. Effects of air pollution on forest growth in

southwestern Germany - hunting for a phantom? Proceedings Div.2 XIXIUFRO World Congress. Aug 1990, Montreal. p 388-395.Germany: Yields, DiseaseComments on the yields of stands suffering crown decline in whichyields may he higher than predicted. May he due to increasedtemperature, CO2, rainfall or mineralization.

Kenward, R.E. 1990. Are tree species mixtures too good for greysquirrels? In Ecology of Mixed Stands of Trees. British EcologicalSociety and IUFRO Div S2.01 Symposium, Edinburgh.UK: WildlifeAn analysis of the grey squirrel problem in forestry.

Kerr, G., Nixon, C.J. and Matthews, R.W. 1990. The silviculture and yieldof mixed species stands: the UK experience. In Ecology of Mixed Standsof Trees. British Ecological Society and IUFRO Div 52.01 Symposium,Edinburgh.UK: Management. YieldIt is believed that nurse crops increase profitability and flexibilityin the lowlands. In the uplands benefits have been clearly demonstratedon certain soils. Mixing spruce with pine or larch is recommended onnutritionally deficient soils in the upland heaths.

Kio, P.R.O. 1976. What future for natural regeneration of tropical highforest? in appraisal with examples from Nigeria and Uganda.Commonwealth Forestry Review 55 (4): 309-318.Nigeria: Economy. ManagementIt is argued that natural regeneration is more economic than planta-tions (GMelina on a 40-year rotation), that includes an assumed 25%decline in yield in the second rotation.

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marketing mixed species. This requires good knowledge of the charac­teristics of each species and effective grading techniques.

Keeves, A. 1966. Sore evidence of loss of productivity with successive rotations of Pinus radiata in the south east of South Australia. Australian Forestry 30; 51-63. Australia: Yield First rotation felled at 24.5 years after a fire, second rotation assessed at 9.5 years. Ccnrronly a drop of 1 - 2 Site Quality classes, sometimes as much as 4 classes.

Kelty, M.J. 1989. Productivity of New England hemlockjhardwood stands as affected by species camposition and canopy structure. Forest Ecology and Management 28: 237-257. USA: Yield Hemlock presence resulted in lower stocking of hardwoods in mixed stands (30%) as well as lower volume (20%) and 5 year increment (14%) of the hardwoods. Total stocking increased (65%) as well as volume (27%) and increment (18%). Silvicultural gains are better conditions for regeneration and less epiconnics.

KeDp, R.H. 1992. The conservation of genetic resources in managed tropical forests. Unasylva 43 (169): 34 - 40.

Kenk, G.K. 1990a. The silviculture of mixed species stands in Gennany. In Ecology of Mixed Stands of Trees. British Ecological Society and IUFRO Div 52.01 Symposium, ~h.

Gennany: Management Clear objectives of mixtures, knowledge of sites and of growing rates of canbining species are indispensable. The selection forest is often seen as an ideal, but its possibilities get over estimated . 672 mixed stand types identified.

Kenk, G.K. 1990b. Effects of air pollution on forest growth in southwestern Gennany - hunting for a phantan? Proceedings Div . 2 XIX IUFRO World Congress. Aug 1990, Montreal. p 388-395. Gennany: Yields, Disease Ccrmients on the yields of stands suffering crown decline in which yields may be higher than predicted. May be due to increased tanperature, m

2, rainfall or mineralization.

Kenward, R.E. 1990. Are tree species mixtures too good for grey squirrels? In Ecology of Mixed Stands of Trees . British Ecological Society and IUFRO Div 52.01 Symposium, ~h. UK: Wildlife An analysis of the grey squirrel problem in forestry.

Kerr, G., Nixon, C.J. and Matthews, R.W. 1990. The silviculture and yield of mixed species stands: the UK experience. In Ecology of . Mixed Stands of Trees. British Ecological Society and IUFRO Div 52.01 Symposium, Edinburgh. UK: Management. Yield It is believed that nurse crops increase profitability and flexibility in the lowlands. In the uplands benefits have been clearly daronstrated on certain soils. Mixing spruce with pine or larch is recxmnended on nutritionally deficient soils in the upland heaths .

Kio, P . R.O. 1976. What future for natural regeneration of tropical high forest? An appraisal with examples fran Nigeria and Uganda. Ccnrronwealth Forestry Review 55 (4): 309-318. Nigeria: Economy . Management It is argued that natural regeneration is I'OClre econanic than planta­tions (Gnelina on a 40-year rotation), that includes an assumed 25% decline in yield in the second rotation .

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Kolesnidhenko, ELV. and Chumakov, V.V. 1973. Basis for selection ofspecies for admixture in mixed plantations of Canadian poplar. LesnoiZhurnal 16 (5): 12-16.USSR: Soils, nutrientsEetula verrucosa, Sambucus racemosa and U/mus pi/Eli/a var. artorea in-hibited poplar growth. Robinia pseudoacacia, Caragna arborescens,Lcnicera tatarica, Alnus glutinosa, Cbtinus coggyria and Fraxinaqpennsylvanica activated. It is suggested that inhibitor spp. should beincluded (10-20%) to promote a "response reaction" in the poplar.

Kan, I. 1973. Growth of Cryptomeria japcnica in mixture with Pinuselliottii var elliottii on the Arraial Estate, Parana, Brazil. Floresta4 (2): 30-33.Brazil: YieldA note on the performance of the species after three years.

Kormanik, P. P. 1979. Biological means of improving nutrient uptake intrees. In the Ecology of even-aged forest plantations. Ford, E.D., Mal-colm, D.C. and Atterson, J. eds. Proceedings Div 1. IUFRO. Institute ofTerrestrial Ecology, CaMbridge.General: Soils, nutrientsReviews the N fixing role of micro-organisms and mycorrhizal fungi.

Kramer, F. 1925. Het verjongingsondérzoek van sandélhout (Santalum album)op Java. (Research on the regeneration of sandalwood (Santalum album)in Java.) Korte Meded. P.v.b.H. 10 and Tectona 18: 455-498. Noted inIndonesian Forestry Abstracts, PUDOC, Wageningen, 1982. Abstract 642.Indonesia: ManagementSantalum album was mixed with field crops and Leucaena glauca. Manyseedlings died when unable to reach the roots of plants in the inter-mediate row. Low herbs around the seedlings helped. Once the rootsreached the Leucaena, they developed well.

Krishnamorthy, K., Eimegowda, N. K. and Rajagopal, D. 1990. Outbreak ofPsyllid, Heteropsylla cubana Crawford on Leucaena and its outlook inalley cropping in India. In Leucaena Psyllid: Problems and Management.International Workshop, Bogar, Indonesia ed. Napompeth, B. andMacDicken, K. G. pp 17-24.India: PestsDescribes distribution, damage and attempts at control of the insect.

KUnst, E.D. 1918. Tbelichtingen Lie de excursie der houtvesters in de 2deen 5dé Inspectie-afdeeling naar Raranggedeh qp 21 December 1918.(Explanations at the excursions of the forest district officers of thesecond and fifth inspection division to Karanggedeh on 21 December1918.) In: Ebschwesen, Dienst van het, 1918. Attulen van de gecom-bieerde dienstvergaderingrder tweede en vijfde inspectieaafdeeling vanhet Ebschwesen te Samarang qp den 20 December 1918. (Minutes of thecoMbined service meeting of the second and fifth inspection division ofthe forest service in Samarang, 20 DeceMber 1918.) Unpublished. Notedin Indonesian Forestry Abstracts, PUDOC, Wageningen, 1982. Abstract606Indonesia: ManagementIf fires are avoided, natural mixing species develop vigorously.Natural mixing is to be preferred to artificial.

Lahiri, A.K. 1987. A note on the prospects of Tectona grandis and XyliadolabrifOrmis mixtures in North Bengal. Indian Journal of Forestry 10(3): 232-233.India: ManagementA line mixture of Xylia dolabrifOrmis and Tectona grandis. 2x2 mspacing, 4 lines teak, 4 lines of Xylia and 4 lines of Schima

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Kolesnichenko, H.V. and CluoakrN, V.V. 1973. Basis for selection of species for admixture in mixed plantations of canadian poplar. Lesnoi Zhurnal16 (5): 12-16. USSR: Soils, nutrients Betula verrucosa, Sambucus racerocJSa and Ulmus pumila var. arrorea in­hibited poplar grcMth. Robinia pseudoacacia, Garagna arrorescens, Lonicera tatarica, Alnus glutinosa, Cotinus coggyria and Fraxinus pennsylvanica activated. It is suggested that inhibitor spp. should J:e included (10-20%) to prarote a "response reaction" in the poplar.

ROn, I. 1973. GroNth of Cryptaneria japonica in mixture with Pinus elliottii var elliottii on the Arraial Estate, Parana, Brazil . Floresta 4 (2) : 30-33. Brazil: Yield A note on the perfonnance of the species after three years.

Kmmanik, P.P. 1979. Biological means of improving nutrient uptake in trees. In the Ecology of even- aged forest plantations. Ford, E. D., Mal­colm, D.C . and Atterson, J . eds . Proceedings Div 1. IUFRO. Institute of Terrestrial Ecology, Cambridge. General: Soils, nutrients Reviews the N fixing role of micro-organisms and mycorrhizal fungi.

Kramer, F. 1925. Het verjongingsonderzoek van sandelhout (Santalum aJ.J:xzm) op Java. (Research on the regeneration of sandalwood (Santalum aJ.J:xzm) in Java.) Korte Meded. P.v.b.H. 10 and Tectona 18: 455-498. Noted in Indonesian Forestry Abstracts, PlIDX:, Wageningen, 1982. Abstract 642 . Indonesia: Management Santalum aJ.J:xzm was mixed with field crops and Leucaena glauca. Many seedlings died when unable to reach the roots of plants in the inter­mediate roo. ION heroo around the seedlings helped. Once the roots reached the Leucaena, they developed well.

Krislmim.nthy, K., !t.megowda, H.K. and Rajagqlill., D. 1990. Outbreak of Psyllid, Heteropsylla cubana Crawford on Leucaena and its outlook in alley cropping in India. In Leucaena Psyllid: Problems and Management. International Workshop, Bogor, Indonesia ed. Napa:rpeth, B. and MacDicken, K.G. pp 17-24. India: Pests DescriJ:es distribution, damage and attempts at control of the insect .

Kunst, E.D. 1918. Toelichtingen bie de excursie der houtvesters in de 2de en 5de Inspectie-afdeeling naar Karanggedeh op 21 December 1918 . (Explanations at the excursions of the forest district officers of the second and fifth inspection division to Karariggedeh on 21 December 1918.) In: Boschwesen, Dienst van het, 1918. Notulen van de gecan­bieerde dienstvergadering der thllgede en vijfde inspectieaafdeeling van het Boschwesen te Samarang op den 20 December 1918. (Minutes of the canbined service meeting of the second and fifth inspection division of the forest service in Samarang, 20 December 1918.) Unpublished. Noted in Indonesian Forestry Abstracts, PlIDX:, Wageningen, 1982 . Abstract 606. Indonesia: Management If fires are aVOided, natural mixing species develop vigorously. Natural mixing is to J:e preferred to artificial.

Lahiri, A.K. 1987. A note on the prospects of Tectona grandis and Xylia dolabriformis mixtures in North Bengal. Indian Journal of Forestry 10 (3): 232-233. India: Management A line mixture of Xylia dolabriformis and Tectona grandis. 2x2 m spacing, 4 lines teak, 4 lines of Xylia and 4 lines of Schima

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wallichii, Chukrasia tabularis, Michaelia chanpaca mixed. The last twoare fire tender and tended to be eliminated. At 5 years mean height 6m, dbh of fire tender spp. 5.1 am, the rest 7-8 am.

Lamb, A.F.A. 1969. Artificial regeneration within the humid lowlandtropical forest. Commonwealth Forestry Review 48 (1): 41-53.Nigeria: Management.Naucleadiderrichii used in matrix with Meliaceae, Lovca trichilioides,Rhaya ivorensis, Entandrophragma utile, E.cylindricum, E.angolense. 5Aauclea to 1 Atliaceae. 3.7m spacing. Nauclea removed at age 12 to 15.Atdiaceae harvested at 60 to 70 years. On Amazon infertile soilsalternate rotations of shade tolerants is recommended.

Laibb, A.F-A. 1991. Personal communication.Nigeria: ManagementLovca too slow growing to keep up with the Nauclea. Cedrela odorata notattacked by Iiypsipoyla in Nigeria.

Lawton, R.M. 1991. Personal communication.Leclerq, I'LL., 1960. Fbmes annosu and Prunus serotina. Ned. Bosb. Tijd-

schr. Vol 33 (2): 74-75.The Netherlands: Environmental, pests and diseasesThe possible danger of using Prunus serotina in coMbination withconifers is discussed.

Leslie, A.J. 1966. The problem of limited funds in tropical forestry.Commonwealth Forestry Review 45 (2): 156-159.The tropics: Management. EconomyThere is no case for allocating scarce funds for extensive silvicul-tural work in natural forests, achieving low economic returns, at theexpense of intensive work in high yielding plantations.

Leslie, A.J. 1987. A second look at the economics of natural managementsystems in tropical mixed forests. Unasylva 155 (1): 47-58.Tropics: EconomicsIn the management of tropical mixed forests the "non-revenue" benefitsmust not be overlooked. Economic prospects are largely governed by therate of interest selected; the choice is subjective, but theappropriate rate is likely to be at the lower end of any plausiblerange.

Leyy, G. 1982. Estimation de l'utilité d`une introduction d'aulne gluti-neux en mélange a dé jeunes plants drépicéa commun sur sol a hydromor-phie tenporaire superficielle. Annales des Sciences Forestieres 39 (1):33-40.France: Soils. ManagementTwo year data from a trial with alder mixed with Norway spruce (1:5) introughs with pseudogley soils. Water table was 5 cm below surface.Evapotranspiration 19-34% greater than control. Lowering the watertable improved rooting, N uptake, and spruce survival. In summer alowered water table may have adverse effects on spruce.

Libby, W.J. 1982. What is the safe number of clones per plantation? InResistance to Disease and Pests in Forest Trees. eds Heybroek, H.M.,Stephan, B.R. and von Weissenberg, K. Proceedings Third InternationalWorkshop on the Genetics of Host Parasite Interactions in ForestrySeptember 1980. Wageningen, Netherlandspp 342-360.Environmental: pests and diseasesCross adaption of a short generation pest maybe more likely among manyclones than among a few unrelated clones. Monoclonal plantations are agood strategy, 2-3 clones possibly the worst strategy. A robust andperhaps optimum strategy is 7-25 clones.

100

wallichii, Chukrasia tabularis, Michaelia chanpaca mixed. The last two are fire tender and tended to be eliminated. At 5 years mean height 6 m, dbh of fire tender spp. 5.1 am, the rest 7-8 am.

Lamb, A.F .A. 1969. Artificial regeneration within the humid lowland tropical forest. Crnmonwealth Forestry Review 48 (1): 41-53. Nigeria: Management. Nauclea diderrichii used in matrix with Meliaceae, Lovoa trichilioides, Khaya ivorensis, Entandrophragma utile, E.cylindrictUll, E.angolense. 5 Nauclea to 1 Meliaceae. 3.7 m spacing. Nauclea removed at age 12 to 15. Meliaceae harvested at 60 to 70 years. On Amazon infertile soils alternate rotations of shade tolerants is recommended.

Lamb, A.F.A. 1991. Personal catIllunication. Nigeria: Management Lovoa too slow growing to keep up with the Nauclea. Cedrela odorata not attacked by Hypsipyla in Nigeria.

Lawton, R.M. 1991. Personal catmUnication. Leclerq, W.L., 1960. Fl:Ines annosus and PLlllJUS serotina. Ned. Bosb. Tijd­

schr. Vol 33 (2): 74-75. The Netherlands: Environmental, pests and diseases The possible danger of using PLlllJUS serotina in canbination with conifers is discussed.

Leslie, A.J. 1966. The problem of limited funds in tropical forestry. Crnmonwealth Forestry Review 45 (2): 156-159. The tropics: Management. Econany There is no case for allocating scarce funds for extensive silvicul­tural work in natural forests, achieving low econanic returns, at the expense of intensive work in high yielding plantations.

Leslie, A.J. 1987. A second look at the econanics of natural management systems in tropical mixed forests. Unasylva 155 (1): 47-58. Tropics: Econanics In the management of tropical mixed forests the "non-revenue" benefits must not be overlooked. Econanic prospects are largely governed by the rate of interest selected; the choice is subjective, but the appropriate rate is likely to be at the ICMer end of any plausible range.

levy, G. 1982. Estimation de 1 'utilite d'tme intrcduction d'aulne gluti­neux en melange a de jetmes plants d' epicea ccmnun sur sol a hyriraror­phie terrporaire superficielle. Annales des Sciences Forestieres 39 (1): 33-40. France: Soils. Management 'lWo year data fran a trial with alder mixed with NOIWaY spruce (1: 5) in troughs with pseudogley soils. Water table was 5 am below surface. Evapotranspiration 19-34% greater than control. ~ring the water table improved rooting, N uptake, and spruce survival. In sunmer a ICMered water table may have adverse effects on spruce.

L:il::by, W.J. 1982. What is the safe number of clones per plantation? In Resistance to Disease and Pests in Forest Trees. eds Heybroek, H.M., Stephan, B.R. and von Weissenberg, K. Proceedings Third International Workshop on the Genetics of Host Parasite Interactions in Forestry September 1980. Wageningen, Netherlands pp 342-360. Envi ronmental: pests and diseases Cross adapt ion of a short generation pest may be rrore likely arrong many clones than arrong a few unrelated clones. M:Jnoclonal plantations are a good strategy, 2- 3 clones possibly the worst strategy. A robust and perhaps optimum strategy is 7-25 clones.

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LOhmander, P. 1990. Flexibilitet - en ledstjaerna rber a11 skogligplanering. Skogsfakta, inventering och ekonomi 23, Swedish Universityof Agricultural Sciences.Sweden: EconomyLong-teila predictions of timber prices and logging costs areimpossible. So is the future impact of environmental changes.Therefore,maintenance flexibility is of vital importance. Mixed standspermit more flexibility. The most economic species can be encouraged infuture thinnings.

Lowe, R.G. 1991 Personal communication.Nigeria: Management

Lundgren, B. 1980. Plantation forestry in tropical countries - physicaland biological potentials and risks. Rural Development Studies 8.

Swedish University of Agricultural Sciences, International RuralDevelopment Centre, Uppsala, Sweden.The tropics: SoilsArgues that plantation forestry in the tropics should be treated muchmore as a short term crop, comparable to an agricultural crop, and thatsoil and site management has not been given adequate attention.

MacGregor, W.D. 1934. Silviculture of the mixed deciduous forests ofNigeria with special reference to the south-western provinces. OxfordForest Memoirs 18. Oxford Forestry Institute (UK).Nigeria: ManagementPrimarily concerned with natural forests, but the success of plantationmixtures and enrichment planting is commented on.

McColl, J.G. and Edmonds, R.L. 1983. Symbiotic nitrogen fixation byLaviesia mimasoides under Eucalyptus. In: IUFRO Symposium on ForestSite and Continuous Productivity, Seattle, Washington, August 1982.General Technical Report, Pacific Northwest Forest and Range ExperimentStation, US Dept. of Agriculture Forest Service (1983), No. PNW-163,pp. 122-129.Australia: SoilsOn red earth kraznozems derived from highly weathered Ordoviciansediments E.dives and E.dalrympleana grow on exposed ridges with anunderstorey of D. mimosoides, fixing 4.5-7 kg/ha/yr. The pattern of Nfixing is examined. N fixing rate constant at normal soil tension, a

. drop when plants reach wilting point. Increased N fixing up to -.01then sudden drop (anaerobic conditions).

Milroy, J.C. 1978. The effects of forestry practice on wildlife inAustralia. A review. Australian Forestry 41 (2): 78-94.Australia: WildlifeThe general effect of forestry practices is to reset or initiatesuccession of plant and animal communities. Management plans cannotwholly replace reserves and national parks.

MtEinnell, F.H. 1990. Status of management and silviculture research onSandalwood in Western Australia and Indonesia. In Proceedings of theSymposium on Sandalwood in the Pacific, April 1990, Honolulu, Hawaii.US Department of Agriculture, Forest Service, General Technical ReportPSW-122. p 19-25.Australia, Indonesia: ManagementA general description of Sandalwood management and research in WesternAustralia and Indonesia.

Maheut, J. and Dommergues, Y. 1959. La fixation par le reboisement dédunes de la presqu'île dé Cap Vert et l'évolution des sols. (Fixationof the Cape Verde Peninsula sand hills by reafforestation.) Bois etForêts des Tropiques No. 63: 3-16.

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Idmander, P. 1990. Flexibilitet - en ledstjaerna foer all skoglig planering. Skogsfakta, inventering och ekonani 23, SWedish University of Agricultural Sciences. SWeden: Econany wng-tenn predictions of timber prices and logging costs are impossible. So is the future impact of environmental changes. Therefore, maintenance flexibility is of vital importance. Mixed stands pennit Il'Ore flexibility. The Il'OSt econanic species can be encouraged in future thinnings.

rowe, R.G. 1991 Personal carmunication. Nigeria: Management

llmvdgLltrr ... ern,., B. 1980. Plantation forestry in tropical countries - physical and biological potentials and risks. Rural Developnent Studies 8. SWedish University of Agricultural Sciences, International Rural Developnent Centre, Uppsala, SWeden. The tropics: Soils Argues that plantation forestry in the tropiCS should be treated nruch Il'Ore as a short tenn crop, canparable to an agricultural crop, and that soil and site management has not been given adequate attention.

Mad;r:egor, W.D. 1934. Silviculture of the mixed deciduous forests of Nigeria with special reference to the south-Western provinces. Oxford Forest MeiOOirs 18 . Oxford Forestry Institute (UK). Nigeria : Management Primarily concerned with natural forests, but the success of plantation mixtures and enrichment planting is carrnented on.

Mcfi>ll, J .G. and Edoonds, R.L. 1983. Symbiotic nitrogen fixation by Daviesia nllmosoides under Eucalyptus. In : IUFRO Symposium on Forest Site and Continuous Productivity, Seattle, Washington, August 1982. General Technical Report, Pacific Northwest Forest and Range Experiment Station, US Dept. of Agriculture Forest Service (1983), No. PNW-163, pp. 122-129. Australia: Soils On red earth kraznozems derived fran highly weathered Ordovician sediments E.dives and E.c1alryrrpleana grow on exposed ridges with an understoreyof D. nllmosoides, fixing 4.5-7 kg/ha/yr. The pattern of N fixing is examined. N fixing rate constant at nonnal soil tension, a drop when plants reach wilting point. Increased N fixing up to -.01 then sudden drop (anaerobic conditions).

McIlroy, J.e. 1978. The effects of forestry practice on wildlife in Australia. A review. Australian Forestry 41 (2): 78-94. Australia: Wildlife The general effect of forestry practices is to reset or initiate succession of plant and animal carmunities. Management plans cannot wholly replace reserves and national parks.

~, F.H. 1990. Status of management and silviculture research on Sandalwood in Western Australia and Indonesia. In Prooeedings of the Symposium on Sandalwood in the Pacific, April 1990, Honolulu, Hawaii. US Departrrent of Agriculture, Forest Service, General Technical Report PSW-122. p 19-25. Australia, Indonesia : Management A general description of Sandalwood management and research in Western Australia and Indonesia.

Maheut, J. and IlcmDezgues, Y. 1959. La fixation par 1e reboisffi/ellt de dl.llles de la presqu' ile de cap Vert et l' evolution des sols. (Fixation of the Cape Verde Peninsula sand hills by reafforestation.) Bois et Fbrets des Tropiques No. 63 : 3-16.

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Senegal: SoilsCasuarina eguisetifolia raises biological activity. Therefore it isconsidered a suitable species for reafforestation sand hill soils. Croprotation may prove necessary.

and Depari, K.S. 1958. (Insect and fungus attacks in thepine forest of northern Sumatra.) Rimba Indonesia 10-12: 417-452.Indonesia: Environmental, pests and diseasesMixing with deciduous species is among the measures recommended tolessen the insect attacks on Pinusimarkusii in the area.

Maheut, J. and Dommergues, Y. 1960. Les teckeraies de Casamance -

Capacité de production des peuplement caractéristigues biologigues etHaintien du potentiel praluctif des sols. (Teak plantations of Casaman-ce - Biological characteristics and maintenance of the productivepotential of soils.) Bois et Foréts de Tropiques 70: 25-42.Senegal: Soils. YieldThere is reason to fear a future decline in the yield of teak planta-tions in Casamance. Mixing is among the preventive measures suggested.

Malcolm, D.C. 1979. The future development of even-aged plantations:silvicultural implications. In: the ecology of even-aged forestplantations. Proceedings of the meeting of Division I, IUFRO,Edinburgh, Sept. 1978. Institute of Terrestrial Ecology, CaMbridge(UK), 1979. pp 481-504.UK: Ecology. Management

Malcolm, D.C. and Titus, B.D. 1983. Decomposing litter as a source ofnutrients for second rotation Sitka Spruce established on peaty gleysoils. In: IUFRO Symposium on Forest Site and Continuous Productivity,Seattle, Washington, August 1982. General Technical Report, PacificNbrthwest Forest and Range Experiment Station, US Dept. of AgricultureForest Service (1983), No. PNW-163, pp 138-145.UK: SoilsLeaving brash after felling on gley soils promoted a high release ofnutrients and weed growth. Without brash there was a tendency fornutrients to be lost in run off.

Mlcolm, D.C., Hooker, J. E. and Wheeler, C.T. 1985. Ilankia symbiosis asa source of nitrogen in forestry: a case study of symbiotic nitrogen-fixation in a mixed Picea-Alnus plantation in Scotland. In Symbiosisand Plant Nutrition. Proceedings of the Royal Society of Edinburgh 85(3/4): 263-282.UK: SoilsIn a 16-year-old plantation on moderately fertile clay a line mixtureof Alnus rubra did not improve growth of P.sitchensis as against a purespruce plantation. The presence of alder increased upper soil N statusby 585 kg/ha.

Malcolm, D.C., Campbell, J.M. andMargan, J. L. 1990. Synergism in mixedspecies stands on oligotrophic sites in Scotland. In Ecology of MixedSpecies Stands of Trees. British Ecological Society and IUFRO Div 2.01Symposium, Edinburgh.UK: SoilsBeneficial effects of Pine and Larch mixtures with Spruce start toappear about age 6 - 8. Differences in rooting intensities and patternstogether with increased N mineralisation rates in organic surface soilsappear to be sufficient to account for the enhanced growth in mixtures.

Mallet, B. 1988. Note sur la croissance dé Khaya senegalensis en planta-tions en zone de for-6f semi-décidue en Cate d'Ivoire. C1101

(unpUblished).Cate d'Ivoire: Management

102

Senegal: Soils casuarina equisetifolia raises biological activity . Therefore it is oonsidered a suitable species for reafforestation sand hill soils. Crop rotation may prove necessary.

Magundikcro, LA. and Depari, K.S. 1958. (Insect and fungus attacks in the pine forest of northern Sumatra.) RiInba Indonesia 10-12: 417-452. Indonesia: Environmental, pests and diseases Mixing with deciduous species is arrong the measures recarrrended to lessen the insect attacks on Pinus IfY2rkusii in the area.

Maheut, J. and DaJmergues, Y. 1960 . Les teckeraies de casamance -Gap3cite de prcxiuction des peuplement caracteristiques biologiques et maintien du potentiel prcxiuctif des sols. (Teak plantations of Casaman­ce - Biological characteristics and maintenance of the productive potential of soils.) Bois et Forets de Tropiques 70 : 25-42. Senegal : Soils. Yield There is reason to fear a future decline in the yield of teak planta­tions in Casamance. Mixing is arrong the preventive measures suggested.

Malcolm, D.C . 1979. The future developnent of even-aged plantations : silvicultural iInplications. In: the eoology of even-aged forest plantations. proceedings of the meeting of Division I, IUFRO, Edinb..rrgh, Sept . 1978. Institute of Terrestrial Eoology, cambridge (UK), 1979. pp 481-504 . UK: Eoology. Management

Malcolm, D.C. and Titus, B.D. 1983. Decanposing litter as a source of nutrients for second rotation Sitka spruce established on peaty gley soils. In: IUFRO Syrrposiurn on Forest Site and Continuous Productivity, Seattle, Washington, August 1982. General Technical Report, Pacific Northwest Forest and Range Experiment station, US Dept. of Agriculture Forest Service (1983), No. PNW-163, pp 138-145 . UK: Soils Leaving brash after felling on gley soils promoted a high release of nutrients and weed grCMth. Without brash there was a tendency for nutrients to be lost in run off.

Malcolm, D.C., Hooker, J.E. and Wheeler, C.T. 1985. Frankia symbiosis as a source of nitrogen in forestry: a case study of symbiotic nitrogen­fixation in a mixed Picea-Alnus plantation in Sootland . In Symbiosis and Plant Nutrition. Proceedings of the Royal Society of Edinburgh 85 (3/4): 263-282 . UK: Soils In a 16-year-old plantation on moderately fertile clay a line mixture of Alnus zubra did not iInprove grCMth of P. si tchensis as against a pure spruce plantation. The presence of alder increased upper soil N status by 585 kg/ha.

Malcolm, D.C., CilIIJlhell, J .M. and Kxgan, J .L. 1990. Synergism in mixed species stands on oligotrophic sites in Sootland. In Eoology of Mixed Species Stands of Trees. British Eoological Society and IUFRO Div 2.01 Syrrposiurn, Edi.nbrrgh. UK : Soils Beneficial effects of Pine and Larch mixtures with Spruce start to appear about age 6 - 8. Differences in rooting intensities and patterns together with increased N mineralisation rates in organic surface soils appear to be sufficient to acoount for the enhanced grCMth in mixtures .

Mallet, B. 1988. Note sur la croissance de Khaya senegalensis en planta­tions en zone de foret sffili -decidue en cote d ' Ivoire . CI'FT (unpublished) . cote d'Ivoire: Management

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Khaya senegalensis seems to grow best in openings, although lypsipylarobusta poses problems. Stem fault is better when mixed with Leur!aenaleucocephala or Cedrela odorata, attacks of H. robusta being delayed.

Mangoendihardjo, S., Wagiman, F.X., Suthoni, A. and SUbyanto. 1990.Economic impact of Leucaena Psyllid infection on estate crops and teakforest plantation. In Leucaena Psyllid: Problems and Management.Wbrkshop in Bogor, Indonesia. F/FRED Coordinating Unit, Bangkok. pp184-188.Indonesia: PestsGives details of areas infected and financial loss involved.

Manil, G. 1971. (The problem of maintaining the fertility of the soilsunder pure conifer plantations.) Bull. Soc. For. Belg. 78 (5): 217-250.Belgium: SoilsA review of the effect of conifer plantations on soils and ecosystems.

Martin, B., Laplace, P. and Quillet, G. 1989. L'UAIC Afocel-ArmefInformations Forêt. No.2 - 1989. Pointe-Noire, Congo.Congo: ManagementDescription of clonal eucalypt plantations. Spatial mixtures achievedby mixing clones, 42 clones used but on 50% of the area only 5 wereused. Mixtures were also achieved over time by succession. Advantagesinclude large genetic base and uniformity of output.

Martin, B. 1991. Les croisements controlés industriels: appui Hajeur A lavole clonale. Nouvelle stratégie pour les plantations fOrestièresintensives. Paper, Theme 13, 10th World Forestry Congress, Paris, 1991.Proceedings, Vb1.5: 43-49.Congo: Clonal forestry

Mathew, G. 1990. Cossid pests of teak in the Asian Region and thepossibilities of their control. In Pests and Diseases of ForestPlantations in the Asia-Pacific Region. FAO, Regional Office for Asiaand the Pacific, Bangkok. pp 204-213.Asia: PestsA review of these pests and their control.

Matziris, D. 1991. Selection and plantation of species and provenances inrelation to sites and objectives. Paper, Theme 13.2, 10th WorldForestry Congress, Paris, 1991. Proceedings, VO1.5: 77-84.Includes a recommendation for the use of mixtures.

Merlin, M. and Van Ravenswaay, D. 1990. The history of human impact on thegenus Santalum in Hawaii. In Proceedings of the Symposium on Sandalwoodin the Pacific, April 1990, Honolulu, Hawaii. US Dept. of AgricultureForest Service, General Technical Report PSW-122.pp 46-60.Hawaii: Management, exploitation and conservationA brief survey.

Mielikainen, K. 1985. The structure and development of pine and sprucestancis with birch mixture. In: Broadleaves in Boreal Silviculture - AnObstacle or an Asset? (Eagglund, B. and Petterson G. eds). SwedishUniversity of Agricultural Sciences, Department of Silviculture, Report14: 189-206.Finland: YieldAdmixture of Betulapendula, 25 to 50%, enhances yield of spruce at allages. Mixed with pine, it enhances yieldq only if removed early, 20-30years. Mixed with pine it depresses sawtimber yields. Eetula pubesoensdoes not enhance spruce growth, but can act as filler in gappy planta-tions.

Miller, P. R. and Eiderman, M.J. (eds). 1977. Photochemical oxidant airpollutant effects on a mixed conifer forest ecosystem.

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Khaya senegalensis seems to grON best in openings, although Hypsipyla robusta poses problems . stem fonn is better when mixed with Leucaena leucocephala or Cedrela odorata, attacks of H.robusta being delayed .

Mangoendihardjo, S . , wagiman, F .X., Suthoni, A. and Subyanto. 1990. Econanic :i.uqJact of Leucaena Psyllid infection on estate crops and teak forest plantation . In Leucaena Psyllid : Problems and Management. Workshop in Bogor, Indonesia. F /FRED C=rdinating Unit, Bangkok. pp 184-188. Indonesia : Pests Gives details of areas infected and financial loss involved.

ManU, G. 1971 . (The problem of maintaining the fertility of the soils under pure conifer plantations . ) Bull . Soc. For. Belg . 78 (5): 217-250 . Belgium: Soils A review of the effect of conifer plantations on soils and ecosystems.

Martin, B. , T,aplace, P. and ~et, G. 1989 . L 'UAIC Afocel-Annef Informations Fbret . No. 2 - 1989 . Pointe-Noire, Congo . Congo : Management Description of clonal eucalypt plantations. Spatial mixtures achieved by mixing clones, 42 clones used but on 50% of the area only 5 were used . Mixtures were also achieved over time by succession. Advantages include large genetic base and unifonnity of output.

Martin, B. 1991 . Les croisements cantroles industriels : appui majeur a la voie c1anale. Nouvelle strategie pour les plantations forestieres intensives. Paper, Theme 13, lOth World Forestry Congress, Paris, 1991. Proceedings, Vol. 5: 43-49. Congo:. Clonal forestry

Mathew, G. 1990 . Cossid pests of teak in the Asian Region and the possibilities of their control. In Pests and Diseases of Forest Plantations in the Asia-Pacific Region. TIIO, Regional Office for Asia and the Pacific, Bangkok . pp 204-213. Asia : Pests A review of these pests and their control .

Matziris, D. 1991. Selection and plantation of species and provenances in relation to sites and objectives. Paper, Theme 13. 2, lOth World Forestry Congress, Paris, 1991. Proceedings, Vol.5 : 77-84. Includes a reoammendation for the use of mixtures.

Merlin, M. and Van Ravenswaay, D. 1990. The history of human :i.uqJact on the . genus Santalum in Hawaii. In Pr=eedings of the Symposium on Sandalwood

in the PacifiC, April 1990, Honolulu, Hawaii . US Dept. of Agriculture Forest Service, General Technical Report PSW-122. pp 46-60. Hawaii: Management, explOitation and conservation A brief survey.

Mielikainen, K. 1985. The structure and developnent of pine and spruce stands with birch mixture. In : Broadleaves in Boreal Silviculture - An Obstacle or an Asset? (Hagglund, B. and Petterson G. eds). Swedish University of Agricultural Sciences, Department of SilViculture, Report 14: 189-206. Finland : Yield Admixture of Betula pendula, 25 to 50%, enhances yield of spruce at all ages . Mixed with pine, it enhances yields only if rerooved early, 20-30 years. Mixed with pine it depresses sawtimber yields. Betula pubescens does not enhance spruce grONth, but can act as filler in gappy planta­tions.

Miller, P.R. and Eidennan, M.J . (eds). 1977. Phot=hemical oxidant air pollutant effects on a mixed conifer forest ecosystem.

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EPA 600/3-77-104. USEPA, Corvallis, Oregon. pp 338.Environment: Pollution

Mbffat, A.J. and Boswell, R.C. 1990. Effect of tree species and speciesmixtures on soil properties at Gisburn forest, Yorkshire. Soil Use andManagement 6 (1): 46-51.UK: Soils32 year old mixture experiment with Scots pin, Norway spruce, oak,alder and grass control. The soil under conifers and alder was slightlymore acid than under oak and grass. pH decline on all plots. Conifershad thicker F and H, but thinner A, horizons. Conifers and alder mayhave retarded formation of an iron deficient B horizon.

Mans, B., Applegate, G.B. and Gilmour, D.A. 1988. Biomass and produc-tivity estimations for community forest management: a case study fromthe hills of Nepal - II. Dry matter production in mixed young stands ofChir pine (Rinus roxburghii) and broad leaved species. Biomass 17: 165-184Nepal: YieldsStanding biomass varied from 15t/ha (7.74 pine, 7.26 broadleaves) onsouthern slope ridge to 41.77 (29.73 pine, 12.04 broadleaves) onnorthern slope. Annual dry matter production from 4.50t/ha/yr (2.27pine, 2.23 broadleaves) to 10.82 (6.74 pine, 4.08 broadleaves).

Mooney, J.W.C., 1962. The tropical shelterwood system in the high forestof Ghana. Commonwealth Forestry Review 41 (3): 205-208.Ghana: ManagementDiscusses the need for clear objectives and management of incompatiblespecies. Mbst valuable timbers are slow growing shade bearers. Highervolumes can be achieved with light demanders. Higher utilisation inproduction for the local market than for export. TSS consideredunsuitable for production of "quality" species.Bilan 1987. Essais comportement Cedrela odorata.CTi,2 (unpUblished).Cate d'Ivoire: YieldProductivity of pure stands of Cedrela odorata was found to be higherthan stands of C.cdorata and Terminalia ivorensis mixed.

Mbraes de Jesus, R. and Brouard, J.S. 1989. Eucalyptus-Leucaena mixtureexperiment. I. Growth and yield. International Tree Crops Journal 5:257-269.Brazil: YieldA trial with E. urophylla and two varieties of L. leucccephala. At age7 eucalyptus survival varied from 75% (control) to 50% mixture).Leucaena survival was 95%. Eucalyptus yield in control was greater thanin raixed plots, in turn greater than the Leucaena. Inorganic fertilizermay have reduced the N fixing of the Leucaena.

Mbrris, A.R. 1986 Soil Fertility and Long term Productivity of Pinuspatula in Swaziland. Unpublished Thesis for PhD, Reading University(UK). pp 398.

Swaziland: SoilsEstimates of nutrient removal, nutrient content of the mature stand,soil nutrient content and nutrient removal in harvested logs.

Mbss, D. 1979. Even-aged plantations as a habitat for birds. In: Theecology of even-aged forest plantations. Proceedings of the meeting ofDivision I, IUFRO, Edinburgh, Sept. 1978. Institute of TerrestrialEcology, CaMbridge (UK), 1979.UK: WildlifeWildlife diversity increases at the boundaries of two habitats. Declineof a species may be due to the removal of its food supply rather than

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EPA 600/3-77-104. USEPA, Corvallis, Oregon. pp 338 . Environrrent: Pollution

!t>fiat, A.J. and Boswell, R.C. 1990. Effect of tree species and species mixtures on soil properties at Gisburn forest, Yorkshire . Soil Use and Management 6 (1): 46-51. UK: Soils 32 year old mixture experiment with Scots pine, No:rway spruce, oak, alder and grass control. The soil unde r conifers and alder was slightly rrore acid than under oak and grass. pH decline on all plots . Conifers had thicker F and H, but thinner A, horizons . Conifers and alder may have retarded formation of an iron deficient B horizon.

K:lhns, B., ARllegate, G.B. and Gilmour, D.A. 1988. Biarass and produc­tivity estimations for community forest management: a case study fram the hills of Nepal - II. Dry matter production in mixed young stands of Chir pine (Pinus roxburghii) and broad leaved species . Biarass 17: 165-

· 184 Nepal: Yields Standing biarass varied fram 15t/ha (7 .74 pine , 7.26 broadleaves) on southern slope ridge to 41.77 (29 . 73 pine, 12 . 04 broadleaves) on northern slope. Annual dry matter production fram 4. 50t/ha/yr (2.27 pine, 2 . 23 broadleaves) to 10.82 (6. 74 pine, 4 . 08 broadleaves).

M:xlney, J.W.C., 1962. The tropical she l terwood system in the high forest of Ghana . Ccmmonwealth Forestry Review 41 (3) : 205-208 . Ghana: Management Discusses the need for clear objectives and management of incanpatible species. M:Jst valuable timbers are slow growing shade bearers . Higher volumes can be achieved with light demanders . Higher utilisation in production for the local market than for export . TSS considered unsuitable for production of "quality" species.

Iii:.pri Bilan 1987. Essais carportement Cedrela odorata . CI'FT (unpublished). COte d' Ivoire: Yield Productivity of pure stands of Cedrela odorata was found to be higher than stands of C.odorata and Tenninalia ivorensis mixed.

M:lraes de Jesus, R. and Brouard, J .S. 1989. Eucalyptus-Leucaena mixture experiment. I. Growth and y i e ld . International Tree Crops JournalS: 257-269. Brazil: Yield A trial with E. urophylla and two varieties of L. leucocephala . At age 7 eucalyptus survival varied fram 75% (control) to 50% mixture). Leucaena survival was 95%. Eucalyptus yield in control was greater than in mixed plots, in turn greater than the Leucaena. Inorganic fertilizer may have reduced the N fixing of the Leucaena. .

MJrris, A.R. 1986 Soil Fertility and IDng tenn Productivity of Pinus patula in Swaziland. Unpublished Thesis f or PhD, Reading University (UK). pp 398. Swaziland: Soils Estimates of nutrient removal, nutrient content of the mature stand, soil nutrient content and nutrient removal in harvested logs .

K:lss, D. 1979. Even-aged plantations as a habitat for birds. In : The ecology of even-aged forest plantations . Proceedings of the meeting of Division I, IUFRO, Edinburgh, Sept . 1978 . Institute of Te=estrial Ecology, Cambridge (UK), 1979 . UK: Wildlife Wildlife diversity increases at the boundaries of two habitats. Decline of a species may be due to the removal of its food supply rather than

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the presence of trees (e.g. ravens and sheep on moorlands). Diversityof structure (all ages) as important as diversity of species.

Muir, W.D. 1970. The problem of maintaining site fertility withsuccessive croppings. Australian Journal of Science 32 (8): 316-324General: SoilsDecline in productivity in second rotation crops appears to he confinedto soils of low natural fertility.

MUrray, M.D. and Miller, R.E. 1986. Early survival and growth of plantedDouglas-fir with red alder in four mixed regimes. Pacific North WestResearch Station, US Dept. of Agriculture Forest Service. pp 13.USA: ManagementRetaining 1250 red alder/ha to 6-8 years had no adverse effect onDouglas fir in Cascade Range.

array, M.D. and Leonard, P.C. 1990. Growth of trees and standstructure in mixed stands of Pacific silver fir and western hemlodk. USDept. of Agriculture Forest Service Research PaperPNW-RP-431. pp 12.USA: ManagementAn analysis of six hemlodk/silver fir stands. Hemlock (Tuga hetero-phylla) has faster initial height growth but silver fir (Abiesamabilis) after about 35 years has faster growth. Therefore fir shouldnot be discriminated against in early thinnings.

MUttiAh, S. 1965. A comparison of three repeated inventories of Sundapolamixed selection working circle and future management. Ceylon Forester7(1/2): 3-35.Sri Lanka: ManagementSWietenia macrqphylla mixed with Tectona grandis and Artocaryousintegrifolius. Age unknown. S.macrqphylla 59 to 84% of crop (by stemnumber), T. grandis 2 to 15% and A.integrifollus 8 to 19%. Volume 94 to155 NO/ha (dbh up to 58 am), but trees over 78 an felled 1955-1960.Profuse mahogany regeneration. Proposal to treat as selection forest toachieve an all age structure.

Miuttiah, S. 1991. Personal communication.Sri Lanka: ManagementSundapola plantations established circa 1901. The potential for con-version to uneven-aged (pure) plantation uas recognised in the early1950s. But Mahogany could not have been established without themixture. Probably inadvisable to go to pure plantation. Exploitationcarried out with extreme care.

Neil, P.E. 1990. Growing Sandalwood in Nepal - Potential silviculturalmethods and research priorities. In Proceedings of the Symposium onSandalwood in the Pacific, April 1990, Honolulu, Hawaii. US Departmentof Agriculture, Forest Service, General Technical Report PSW-122. pp72-75.

Nepal, India: ManagementA brief description of silvicultural management proposals.

Nelson, T.C. 1964-65. Growth models for stands of mixed species composi-tion. Proc. Soc. Amer. For. 1964, 1965, pp. 229-231.USA: YieldBased on a simplified theory, a growth model for mixed stands isproposed.

Ng, F.S.P. 1991 Personal communication.Malaysia: ManagementThe Kepong plantings were established as demonstration plots underAlbizia falcataria, which was removed. Dipterocarps were successful,but eucalyptus a failure. Understorey species have regenerated natural-

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the presence of trees (e .g . ravens and sheep on moorlands) . Diversity of structure (all ages) as important as diversity of species .

M.rlr, W. D. 1970 . The problem of maintaining site fertility with successive croppings . Australian Journal of Science 32 (8): 316-324 General: Soils Decline in productivity in second rotation crops appears to be confined to soils of low natural fertility.

ltIrray, M.D. and Miller, R.E. 1986. Early survival and growth of planted Douglas-fir with red alder in four mixed reg:irnes. Pacific North West Research Station, US Dept. of Agriculture Forest Service. pp 13. USA: Management Retaining 1250 red alderjha to 6-8 years had no adverse effect on Douglas fir in Cascade Range .

!t.Jrray, M.D. and Leonard, P.C. 1990. Growth of trees and stand structure in mixed stands of Pacific silver fir and western hemlock. US Dept . of Agriculture Forest Service Research Paper PNW-RP-431. pp 12. USA: Management An analysis of six hemlock/silver fir stands . Hemlock (Tsuga heterrr phylla) has faster initial height growth but silver fir (Abies amabilis) after about 35 years has faster growth . Therefore fir should not be discriminated against in early thinnings .

!t.Ittiah, S . 1965. A canparison of three repeated inventories of Sundapola mixed selection working circle and future management . Ceylon Forester 7(1/2) : 3-35 . Sri Lanka : Management SWietenia macIVphylla mixed with Tectona grandis and Art=arpus integrifolius. Age unknown. S .macrophylla 59 to 84% of crop (by stem number), T. grandis 2 to 15% and A.integrifolius 8 to 19% . Volume 94 to 155 ro3/ha (dbh up to 58 em), but trees over 78 em felled 1955-1960. Profuse mahogany regeneration . Proposal to treat as selection forest to achieve an all age structure .

!t.Ittiah, S . 1991. Personal carmunication . Sri Lanka: Management Sundapola plantations established circa 1901. The potential for con­version to uneven-aged (pure) plantation was recognised in the early 1950s . But Mahogany could not have been established without the mixture. Probably inadvisable to go to pure plantation. Exploitation carried out with extre.rre care.

Neil , P . E. 1990 . Growing Sandalwood in Nepal - Potential silvicultural methods and research priorities. In Proceedings of the Symposium on Sandalwood in the Pacific, April 1990, Honolulu, Hawaii. US Department of Agriculture , Forest Service, General Technical Report PSW- 122 . pp 72-75. Nepal , India: Management A brief description of silvicultural management proposals.

Nelson, T.C. 1964--65 . Growth !lKldels for stands of mixed species ccrnposi­tion. Proc. Soc . Amer. For. 1964, 1965, pp . 229-231. USA: Yield Based on a simplified theory, a growth !lKldel for mixed stands is proposed .

Mg, F.S.P. 1991 Personal carmunication . Malaysia: Management The Kepong plantings were established as derronstration plots under Albizia falcataria, which was rerroved . Di pterocaIpS were successful , but eucalyptus a failure. Understorey species have regenerated natural-

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ly. In 30 years a mixed forest had been created. After 60 years usedas a recreational area.

Ng, F.S.P, Zulkifly bin Haji Mokh-tar, Ahnad Abdul Ghani bin Abdul Aziz1982. Leucana leucocephala as a tall cover crop for sawlog plantations.In: Leucaena Research in the Asian-Pacific region, Singapore 1982, pp113-118. IDRC, Canada.Malaysia: Management, cover cropsLeucaena has been used as a tall cover crop together with Tectonagrandis and Araucaria hunsteinii. It shows promise in suppressingImperata, less so in suppressing Pueraria and Centrosema.

Nielsen, P. 1991. (Forest Reseach Branch, Queensland)Personal communication.

Nogueira, J.C.B. 1977. Reflorestamento heterogeneo can essenciasindigenas. Boletim Tecnico, Instituto Florestal, Sao Paulo 24:1-77Brazil: ManagementA, description of the reforestation of a amall area of degraded riparianforest. After 22 years a vigorous semi-deciduous tropical forest hadbeen developed.

Nordstrom, L. 1964. Ek och gran.(0ak and spruce). Skogen 21.Sweden: ManagementA silvicultural regime for regenerating oak in group mixture withspruce is presented. The aim of the regime is a pure stand of highquality oaks.

Nbvais, R.F. de and Poggiani, F. 1983. Eeposicao de folhas e nutrientesemplantacoes florestais puras e concoriadas de Pinus e Ldquidambar.(Leaf fall and nutrient return in pure and mixed plantations of Finusand Liquidambar.) IPEF No. 23: 57-59.Brazil: SoilsLeaf heterogeneity on the floor of the mixed stand appears to increaselitter decomposition and to improve nutrient cycling.

NWOboshi, L.C. 1983. Potential impacts of sane harvesting options onnutrient budgets of a Gmelina pulpwood plantation ecosystem in Nigeria.In: IUFRO Symposium on Forest Site and Continuous Productivity,Seattle, Washington, August 1982. General Technical Report, PacificNorthwest Forest and Range Experiment Station, US Dept. of AgricultureForest Service (1983), No. PNW-163.Nigeria: Soils. ManagementData on the nutrient status of a 10 year old plantation of GMelinaarborea. Soil and erosion data are also presented.

Odendaal, P.B. and Bigalke, R.C. 1979. Habitat selection by bushbudk in adisturbed environment. South African Forestry Journal 108: 39-41.South Africa: WildlifeFive animals radio tradked. Indigenous broadleaved forest met theirtotal requirements. Clearfelled areas preferred at night, and densePinus radiata and P.elliottii plantations at day. Lowest preference wasfor Eucalyptus ddversicolor plantations.

Okafor, J.C. 1977. Development of forest tree crops for food supplies inNigeria. Forest Ecology and Management 1 (3): 235-247.Nigeria: SocialThe importance of tree fruits is stressed. Their silvidulturalrequirements are unknown.

Oliver, C.D. 1980. Even-aged development of mixed-species stands Journalof Forestry 78: 201-203.North America: Management

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ly. In 30 years a mixed forest had been created. After 60 years used as a recreational area.

Ng, F. S. P, Zulkifly bin Haji Mokhtar, Ahnad Abdul Ghani bin Abdul Aziz 1982. I.eucana leucocephala as a tall cover crop for sawlog plantations. In: I.eucaena Research in the Asian-Pacific region, Singapore 1982, pp 113-118. IDRC, Canada. Malaysia: Management, cover crops I.eucaena has been used as a tall cover crop together with Tectona grandis and Araucaria htmSteinii. It sh=s pranise in suppressing Imperata, less so in suppressing Pueraria and Centrosema.

Nielsen, P. 1991. (Forest Reseach Branch, Queensland) Personal cartmlIlication.

~, J.C.B. 1977. Reflorestamento heterogeneo cam essencias indigenas. Boletjm Tecnico, Instituto Florestal, sao Paulo 24: 1-77. Brazil: Management A description of the reforestation of a small area of degraded riparian forest. After 22 years a vigorous semi-deciduous tropical forest had been developed.

Nordstroem, L. 1964. Ek och gran. (oak and spruce) . Skogen 21. SWeden: Management A silvicultural regjme for regenerating oak in group mixture with spruce is presented. The ajm of the regjme is a pure stand of high quality oaks.

NaIIais, R.F. de and Poggiani, F. 1983. Deposicao de folhas e nutrientes em plantacoes florestais puras e concoriadas de Pinus e Liquidambar. (Leaf fall and nutrient return in pure and mixed plantatiOns of Pinus and Liquidambar. ) IPEF No. 23: 57-59. Brazil: SOils Leaf heterogeneity on the floor of the mixed stand appears to increase litter decomposition and to improve nutrient cycling.

Nwoboshi, L.C. 1983. Potential impacts of sare harvesting options on nutrient budgets of a Gnelina pulp.YOOd plantation ecosystem in Nigeria. In: IUFRO SymposiLnn on Forest Site and Continuous Productivity, Seattle, Washington, August 1982. General Technical Report, Pacific Northwest Forest and Range Experjment Station, US Dept. of Agriculture Forest Service (1983), No. PNW-163. Nigeria: SOils. Management Data on the nutrient status of a 10 year old plantation of Gnelina arborea. SOil and erosion data are also presented.

Odendaal, P.B. and Bigal.ke, R.C. 1979. Habitat selection by tushbuck in a disturbed environment. SOuth African Forestry Journal 108: 39-41. SOuth Africa: Wildlife Five animals radio tracked. Indigenous broadleaved forest met their total requirements. Clearfelled areas prefe=ed at night, and dense Pinus radiata and P.elliottii plantatiOns at day. Lo.vest preference was for Eucalyptus diversicolor plantatiOns.

Okafor, J. C. 1977. Developnent of forest tree crops for food supplies in Nigeria. Forest Ecology and Management 1 (3): 235-247. Nigeria: 8=ial The importance of tree fruits is stressed. Their silvicultural requirements are unkno.-m.

Oliver, C.D. 1980. Even-aged developnent of mixed-species stands. Journal of Forestry 78: 201-203. North America: Management

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Stratified forests need not be unevenaged. Certain mixtures e.g.Douglas fir/western hemlockrmwhave higher basal area than pure standsof either species.

Palmer, J. R. 1986. Jari: Lessons for land managers in the tropics. Boiset Forêts des Tropiques 212 (2): 16-27.Brazil: ManagementSite preparation damaging to the soil. Lack of site matching forGMelina (only. 25% of area suitable).

Pandey, D. 1992. Assessment of tropical forest plantation resource. Departmentof Forest Survey, Swedish University of Agricultural Sciences(unpublished).

Paschke, M.14., Jeffrey, 0.D and David, M. B. 1989. Soil nitrogen mineralization in plantations of Júglans regia interplanted with actinorhizalElaea gnus umbellata or Alnus glutinosa. Plant and Soil 118: 33-42.USA: Soils. YieldExamination of mineralised N under 18 year old walnut planted pure andinterplanted 3:1 with autumn olive and alder. There was a marked in-crease in mineralised N under olive, less under alder. up to 18kg/ha/year = 13,5% of total N pool under olive and as law as 52kg/ha/year in control. Walnut growth correlated with N mineralisation.

Peace, T.R. 1957. Approach and perspective in forest pathology. Forestry30: 47-56.General: DiseaseA review of the problem. "Broad assumptions lead to falsesimplifications. We know regrettably little about health and disease intrees:"

Pedk, K.M. 1990. Habitat preferences of birds: the importance of diversityinwoodlands. In Ecology of Mixed Species Stands of Trees. BritishEcological Society and IUFRO Div 2.01 Symposium, Edinburgh.UK: WildlifeNumber of species (passerines) correlated with tree species richnessand diversity. Tree preferences change seasonally and were attributedto changes in food availability.

Perera, W.H. 1962. The development of forest plantations in Ceylon sincethe 17th century. Ceylon Forester 5 (3): 142-151.Sri Lanka: ManagementSWietenia Eacrophylla under 3 year old Artocarpus heterophyllus 1890onwards. Also S.Eacrophylla and Cedrela mexicana enrichment plantingand S.macrophylla under 2nd generation teak.

Perry, D.A. 1979. Variation between and within tree species. In Ecologyof Even-aged Plantations. Ford, E. D., Malcolm, D.C. andAtterson, J. (eds). pp 71-98.General: Ecology

Perry, D.A. and Maghembe, J. 1989. Ecosystem concepts and current trendsin forest management: time for reappraisal. Forest Ecology andManagement 26: 123-140.General: Environmental. EconomyCurrent economic criteria do not address a number of important factors,e.g. sustainability and diversity.

Perry, D.A., Bell, T. and Amaranthus, M.P. 1990. Mycorrhizal fungi inmixed-species forests and other tales of positive feedback, redundancyand stability. In Ecology of Mixed Species Stands of Trees. BritishEcological Society and IUFRO Div 2.01 Symposium, Edinburgh.USA: Soils

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stratified forests need not be unevenaged. Certain mixtures e.g. Douglas fir/western hemlock may have higher basal area than pure stands of either species.

Palmer, J.R. 1986. Jari: Lessons for land managers in the tropics. Bois et Fbrets des Tropiques 212 (2): 16-27. Brazil: Management Site preparation damaging to the soil. Lack of site matching for Gmelina (only. 25% of area suitable).

Pandey, D. 1992. Assessrrent of tropical forest plantation resource. Department of Fbrest Survey, Swedish University of Agricultural Sciences (unpublished) .

Paschke, M.W., Jeffrey, O.D and David, M.B. 1989. Soil nitrogen minerali zation in plantations of Juglans regia inteIplanted with actinorhizal Elaeagnus umbellata or Alnus glutinosa. Plant and Soil 118: 33-42. USA: Soils. Yield Examination of mineralised N under 18 year old walnut planted pure and inteIplanted 3:1 with autumn olive and alder. There was a marked in­crease in mineralised N under olive, less under alder. Up to 18 kg/ha/year = 13.5% of total N pool under olive and as 100 as 52 kg/ha/year in control. Walnut grooth correlated with N mineralisation.

Peace, T.R. 1957. Approach and perspective in forest pathology. Forestry 30: 47-56. General: Disease A review of the problem. "Broad assumptions lead to false simplifications. We knoo regrettably little about health and disease in trees:"

Peck, K.M. 1990. Habitat preferences of birds: the importance of diversity in woodlands. In Ecology of Mixed Species stands of Trees. British Ecological Society and IUFRO Div 2. 01 S~ium, Edinburgh. UK: Wildlife Number of species (passerines) correlated with tree species richness and diversity . Tree preferences change seasonally and were attributed to changes in food availability .

Perera, W.H. 1962. The developrent of forest plantations in Ceylon since the 17th century. Ceylon Forester 5 (3): 142-151. Sri Lanka: Management SWietenia macrophylla under 3 year old Art=azpus heterophyllus 1890 onwards. Also S.macrophylla and Cedrela mexicana enrichment planting and S.macrophylla under 2nd generation teQk.

Perry, D.A. 1979. Variation between and within tree species. In Ecology of Even-aged Plantations. Ford, E.D., Malcolm, D.C. and Atterson, J. (eds). pp 71-98. General: Ecology

Perry, D.A. and Hagheuile, J. 1989. Ecosystem concepts and current trends in forest management: time for reappraisal. Fbrest Ecology and Management 26: 123-140 . General: Environmental. Econany Current econanic criteria do not address a number of important factors, e.g. sustainability and diversity.

Perry, D.A., Bell, T. and Amarantirus, M.P. 1990. Mycorrhizal fungi in mixed-species forests and other tales of positive feedback, redundancy and stability. In Ecology of Mixed Species Stands of Trees. British Ecological Society and IUFRO Div 2.01 S~ium, Edinburgh. USA: Soils

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The effect of mycorrhizal fungi on competition between plants ofdifferent species show that they convert a negative interaction intoone that is either neutral or positive (increases yield). Theyphysically link trees with their hyphae, through which carbon and nut-rients probably pass.

Phillips, D.R. and AbercroMbie, J.A. 1987. Pine-hardwood mixtures - Anew concept in regeneration. Southern Journal of Applied Forestry. 11(4): 192-197.USA: ManagementA regime is proposed, where natural regeneration of hardwoods is re-tained together with pine seedlings.

Pierlot, R. 1955. Le reboisement en placeaux espac6s. Bulletin d'Infor-Elation de l'INEAC 4 (5): 325-338.Zaire: ManagementA regeneration system, planting in spaced dense groups, is presented.

Poole, B. 1989. Forest health issues in south-east Asia. New ZealandJournal of Forest Science 19 (2/3): 159-162Asia: Environmental, pests and diseasesA review of important insect pests in south-east Asia.

Poore, MLD., Burgess, P. F., Palmer, J. R., Reitenbergen, S. and Synnott,T. J. 1989. No Timber without Trees. Earthscan Publications Ltd. , LondonWCIH ODD. 252 pp.General: ManagementAn overview of mainly natural forest policies.

Prasad, K.G., Singh, S.B., Gupta, G.N. am d George, EL 1985. Studies inchanges in soil properties under different vegetations. Indian Forester111 (10): 794-7911.India: SoilsAfter 40 years organic carbon had decreased in the top 18 an of thesoil. Natural forest: mixed plantation: teak plantation1.7:-1.5:0.8%. P905 13:17:10 ppm. Total Mg 1.6:1.5:0.9 but exchangeableMg increased under teak. Soil considered less fertile under Teak.

Pryor, S.N. and Savill, P.S. 1986. Silvicultural systems for broadleavedwoodland in Britain. Oxford Forestry Institute (UK) Occasional Paper32

UK: ManagementGreater production from selection forests unproven, but claim forgreater value more sustainable.

Queensland 1990. Annual Report for 1989. Queensland Forest Department.Australia: ManagementIncludes a statement of areas of plantations by species.

Radkham, O. 1990. Mixtures, mosaics and clones: the distribution of treeswithin European woods. In: Ecology of Mixed Species Stands of Trees.British Ecological Society and IUFRO Div 2.01 Symposium, Edinburgh.Europe: EnvironmentalPure natural stands are often in extreme environments, Pinus mugo,cembra and Ainus viridis at high elevations, Eetula in the far north,CUpressus sempervirens on south-facing limestone in Crete, Quercuspetraea in the Atlantic climate of west Britain, Alnus glutinosa inpeaty valleys, alercus and fagus in browsed areas.

Radwan, M.A. and DeBell, D.S. 1988. Nutrient relations in coppiced blackcottonwood and red alder. Plant and Soil 106 (2): 171-177.USA: ManagementMixed culture of Pópulus trichocarpa and Alnus rubra appears pramisingbecause of the increased growth of the poplar.

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The effect of mycorrhizal fungi on canpetition between plants of different species stJa..l that they convert a negative interaction into one that is either neutral or positive (increases yield). They physically link trees with their hyphae, through which carJ::x:m and nut­rients probably pass .

Phillips, D.R. and AbercraIirl.e, J.A. 1987. Pine-hardwood mixtures - A new concept in regeneration. Southern Journal of Applied Forestry . 11 (4): 192-197. USA: Management A regime is proposed, where natural regeneration of hardwoods is re­tained together with pine seedlings.

Pierlot, R. 1955. Le reboisement en placeaux espaces . Bulletin d'Infor­mation de l'~C 4 (5): 325-338 . Zaire: Management A regeneration system, planting in spaced dense groups, is presented .

Poole, B. 1989. Forest health issues in south-east Asia . New Zealand Journal of Forest Science 19 (2/3): 159-162 Asia: Environmental, pests and diseases A review of important insect pests in south-east Asia.

Pcare, M.D., BIRgess, P. F ., Palmer, J. R., Reitenbergen, S . and Synnott, T.J. 1989. No Timber without Trees. Earthscan Publications Ltd., London WCLH ODD. 252 pp. General: Management An overview of mainly natural forest policies.

Prasad, K.G., Singh, S.B., Gupta, G.N. and George, M. 1985. Studies in changes in soil properties under different vegetations. Indian Forester 111 (10): 794-7911 . India: Soils After 40 years organic carbon had decreased in the top 18 an of the soil. Natural forest: mixed plantation : teak plantation 1 .7:-1 . 5 :0.8%. P~05 13 :17:10 ppm. Total Mg 1 .6:1.5 :0.9 but exchangeable Mg increased unaer teak . Soil considered less fertile under Teak.

Pryor, S . N. and Savill, P . S. 1986. Silvicultural systems for broadleaved woodland in Britain . OXford Forestry Institute (UK) Occasional Paper 32 . UK: Management Greater production fran selection forests unproven, but claim for greater value more sustainable .

~land 1990. Annual Report for 1989. Queensland Forest Department . Australia: Management Includes a statement of areas of plantations by species.

Rackham, O. 1990. Mixtures, mosaics and clones: the distribution of trees within European woods. In : Ecology of Mixed Species Stands of Trees. British Ecological Society and IUFRO Div 2 . 01 Symposium, Edinburgh. Europe: Environmental Pure natural stands are often in extreme environments, Pinus mugo, P. cembra and Alnus viridis at high elevations, Betula in the far north, CUpressus sanpervirens on south-facing limestone in Crete, Olercus petraea in the Atlantic climate of west Britain, Alnus glutmosa in peaty valleys, Olercus and Fagus in br~ed areas.

Radwan, M.A. and DeBell, D.S. 1988. Nutrient relations in coppiced black cottonwood and red alder . Plant and Soil 106 (2) : 171-177. USA: Management Mixed culture of Populus trichocarpa and Alnus rubra appears pranising because of the increased gro.-Tth of the poplar.

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Rai, Sal. 1990. Status and cultivation of Sandalwood in India. InProceedings of the Symposium on Sandalwood in the Pacific, April 1990,Honolulu,Hawaii. US Department of Agriculture, Forest Service, GeneralTechnical Report PSW-122. pp 66-71.India: Management, Ecology, Yields, MarketingA brief account of Sandalwood cultivation.

Ram Prasad 1988. Sal plantation on bauxite mined out site of MadhyaPradesh. Journal of Tropical Forestry 4 (1): 68-73.India: SoilsSane methods of revegetating a mined out site were tried. One of themethods was sal (Shorea robusta) mixed with Grevillea robusta, EUca-lyptus camaldulensis, Tbona ciliata and Finus kesiya.

Ran Prasad and Camire, C. 1988. Afforestation of dolomite mineoverburdens in Madhya Pradesh. Journal of Tropical Forestry 3 (2): 124-131.

India: Management. YieldAcacia auriculiformis, A. campylacantha, GMelina arborea, Eucalyptushybrid, andPongamiapinnata grown with bamboo had rather better heightand diameter growth and survival than when grown without. Albiziaprocera had slightly worse growth.

Ratcliffe, P.R. ami Petty, S.J. 1988. The management of commercial forestsfor wildlife. Nat. Environ. Res. Council. Inst. Terrestrial Ecology(U.K.) Symposium Proceedings: 17: 177-187.

Raunio, A.L. 1991. Personal Communication.Ethiopia: ManagementGrevillea robusta planted into a coppiced Eucalyptus grandis stand oflaw stocking - showing promise. Pinus radiata being planted as a 25%mixture with Pinuspatula or CUpressus lusitanica. Both line mixtures.Grevillea is not browsed by duiker.

Reddell, P. 1990. Increasing productivity in plantings of Casuarina byinoculation with Frankia. In Advances in Casuarina Research andUtilization. Desert Development Center, American University in Cairo,Box 2511, Cairo, Egypt.Queensland, Zimbabwe: SoilsInoculation with Frankia can result in up to 100% increase in woodproduction in 4 year old trees of C.cunninghamiana. Omission of P fromnutrients applied can reduce growth by 75%.

Redden., P., RoSbrodk, P.A., Bowen, G.D. and Gwaze, D. 1988. Growthresponses in Casuarina cunninghamiana plantings to inoculation withFrankia. Plant and Soil 108: 79-86.Australia, Zimbabwe: SoilsOne Frankia strain increased height growth by 200% at age 14 months inZimbabwe. Wood production increases up to 150% at age 45 months werenoted in Queensland. Application of P increased wood production by upto 250% over control.

Reese, K.P. and Ratti, J.T. 1988. Edge effect: a concept under scrutiny.Trans. 53rd. North American Wildlife and Natural Resources Conference.pp 123 - 136.

Rehmani, A.R. 1989. The great Indian bustard. Final Report. Bombay NaturalHistory Society, India.

Rennie, P.J. 1962. Sane long-term effects of tree growth on soil produc-tivity. Commonwealth Forestry Review 41 (3): 209-213.UK: SoilsComparison of soils under 70 year old hardwood and conifer on Callunamoorland with impoverished soils. Conifers increased porosity in humuslayer more than hardwoods. Both impoverished mineral soils below 30 am,

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Rai, S.N. 1990 . Status and cultivation of Sandalwood in India . In Proceedings of the Syrrq:lOSium on Sandalwood in the Pacific, April 1990, Honolulu, Hawaii. US Depart:rrent of Agriculture, Forest Service, General Technical Report PSW-122. pp 66-71. India : Management, Ecology, Yields, Marketing A brief account of Sandalwood cultivation .

Ran Prasad 1988 . Sal plantation on bauxite mined out site of Madhya Pradesh . Journal of Tropical Forestry 4 (1): 68-73 . India: Soils Sane methods of revegetating a mined out site were tried. One of the methods was sal (Shorea robusta) mixed with Grevillea robusta, Euca­lyptus camaldulensis, Tbona ciliata and Pinus kesiya .

Ran Prasad and camire, C. 1988. Afforestation of dolanite mine overbrrdens in Madhya Pradesh . Journal of Tropical Forestry 3 (2): 124-131. India : Management. Yield Acacia auriculiformis, A . campylacantha, Gnelina arborea, Eucalyptus hybrid, and Pongamia pinnata grown with bamboo had rather better height and diameter grcMth and survival than when gr= without . Albizia procera had slightly worse grCMth.

Ratcl.i£fe, P.R. and Petty, S.J. 1988. The management of ccmnercial forests for wildlife . Nat. Environ . Res. Council . Inst. Terrestrial Ecology (U .K . ) Syrrq:lOSium Proceedings: 17: 177-187 .

Raunio, A. L. 1991. Personal Crnmunication. Ethiopia: Management Grevillea. robusta planted into a coppiced Eucalyptus grandis stand of 1= stocking - sha.'ing pranise. Pinus radiata being planted as a 25% mixture with Pinus patula or Cupressus lusitanica. Both line mixtures. Grevillea is not br=sed by duiker.

Reddell, P. 1990 . Increasing productivity in plantings of Gasuarina by inoculation with Frankia . In Advances in Gasuarina Research and Utilization. Desert DevelopIEIlt Center, American University in cairo, Box 2511, cairo, Egypt . QJ.eensland, Z.il!il:Jab,ve: Soils Inoculation with Frankia can result in up to 100% increase in wood production in 4 year old trees of C.CUIIDinghamiana. Qnission of P fran nutrients applied can reduce gra.'th by 75% .

Reddell, P., Rosbrook, P.A., Bowen, G. D. and Gwaze, D. 1988. Gra.'th responses in Gasuarina CUIIDinghamiana plantings to inoculation with Frankia. Plant and Soil 108: 79-86. Australia, Z.il!il:Jab,ve : Soils One Frankia strain increased height grCMth by 200% at age 14 months in Z.il!il:Jab,ve. Wood production increases up to 150% at age 45 months were noted in QJ.eensland. Application of P increased wood production by up to 250% over control .

Reese, K.P. and Ratti, J.T. 1988. Edge effect : a concept under scrutiny. Trans. 53rd . North American Wildlife and Natural Resources Conference . pp 123 - 136.

Rebnani., A.R. 1989 . The great Indian bustard . Final Report . Banbay Natural History SOciety, India .

Rennie, P.J. 1962. Sane long-term effects of tree grCMth on soil produc­tivity . Commonwealth Forestry Review 41 (3) : 209-213. UK: Soils Ccrnparison of soils under 70 year old hardwood and conifer on Calluna moorland with :impoverished soils . Conifers increased porosity in humus layer more than hardwocds. Both :impoverished mineral soils bel= 30 an,

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conifers more than hardwoods. ConifeLb reduced pH from 3.3 to 3.1,hardwoods increased pH to 3.5.

Ricibinson, J.B.D. 1967. The effect of exotic softwood crops on thechemical fertility of a tropical soil. East African Agricultural andForestry Journal 33: 175-189.Kenya: SoilsComparison of indigenous forest, first and second rotation conifer andhardwood plantation following conifer.

Robinson, Hosegood, P.H. and Dyson, W.G. 1966. Note on apreliminary study of the effects of an East African softwood crop onthe physical and chemical condition of a tropical soil. CommonwealthForestry Review 45 (4): 359-365Kenya: SoilsSoils examined under a 16 year old CUpressus lusitanica plantationStanding at 420/ha and a neighbouring secondary forest.

Robinson, R.K. 1973. Mycorrhizas and "second rotation decline" in Pinuspatula in Swaziland. South African Forestry Journal 84: 16-19Swaziland: SoilsA positive correlation between the mean number of mycorrhizal roots,the degree of infection and crop vigour in each of two rotations. Ladkof vigourmaybe a consequence of law biological activityas evinced bya build up of litter, absence of earthworms and ladk of mycorrhiza.

Rodgers, W.A. 1992. Managing forests for biodiversity in India: a review ofconcepts and practices. Manuscript. Wildlife Institute of India,Debra Dun. 75 pp.

Ryan, E.A. and Alexander, I.J. 1990. Mycorrhizal aspects of improvedSitka spruce growth in mixed stands. In: Ecology of Mixed SpeciesStands of Trees. British Ecological Society and IUFRO Div 2.01Symposium, Edinburgh.UK: SoilsEvidence given that Suillus variagatus, a mycorrhizal associate ofPinus sylvestris but not of Picea sitchensis, occurs in mixed planta-tions and may be able to degrade protein rapidly leaving 87% of theprotein degradation products in solution, which may be available foruptake by the Sitka spruce.

Ryan, P.A. 1985. Hbop pine second rotation growth and nutrition. Paperpresented to Second Rotation esyablishment: Problems, PossibleSolutions and Identification of Research Needs Conference. Topic 2.2.Gympie, Queensland.Australia: Yield. Management

Salwasser, H. 1985. Integrating wildlife into the managed forest. In: ASymposium on Forestry and Wildlife Management in Canada. ForestryChronicle, 146 - 149.

Salwasser, H. 1990. Sustainability as a conservation paradigm. Cons.Biology 4 (3): 213 - 215.

Samraj, P.,Chinnamani, S. and Haldorai, B. 1977. Natural versus man-madeforest in the Nilgiris with special reference to run-off, soil loss andproductivity. Indian Forester 103: 460-465.India: Soils. YieldRun-off under Eucalyptus globulus and Acacia mearnsii was less thanunder natural forest, but more than protected grass plots and Cytisusscgparius plots. Yields of eucalyptus and wattle Inixed, 700 stems/ha,482 m3/ha at age 10 as against 322 e for Eucalyptus, 2500 stems/ha, and125 nO for wattle, 1600 stems/ha, in pure plantations.

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conifers rrore than hardwoc:ds. Conifers reduced pH fran 3. 3 to 3. 1, hardwoc:ds increased pH to 3. 5 .

Hobinsan, J .B.D. 1967. The effect of exotic softwood crops on the chemical fertility of a tropical soil. East African Agricultural and Forestry Journal 33: 175-189. Kenya: Soils Crniparison of indigenous forest, first and second rotation conifer and hardwood plantation foll~ing conifer.

Hobinsan, J .B.D, Hosegood, P.H. and Dyson, W.G. 1966. Note on a preliminary study of the effects of an East African softwood crop on the physical and chemical condition of a tropical soil. Carm:lllwealth Forestry Review 45 (4): 359-365 Kenya: Soils Soils examined under a 16 year old CUpressus lusitanica plantation standing at 420/ha and a neighbouring secondary forest.

Hobinsan, R.K. 1973. Mycorrhizas and "second rotation decline" in Pinus patula in swaziland. South African Forestry Journal 84: 16-19 swaziland: Soils A positive correlation between the mean number of mycorrhizal roots, the degree of infection and crop vigour in each of two rotations. Lack of vigour may be a consequence of l~ biological activity as evinced by a build up of litter, absence of earthworms and lack of mycorrhiza.

Rodgers, W.A. 1992. Managing forests for biodiversity in India: a review of concepts and practices. Manuscript. Wildlife Institute of India, Dehra Dun. 75 pp.

Ryan, E.A. and Alexander, I.J. 1990. Mycorrhizal aspects of improved Sitka spruce gr~h in mixed stands . In: Ecology of Mixed Species Stands of Trees. British Ecological Society and IUFRO Div 2.01 Symposium, Edinburgh. UK: Soils Evidence given that Suillus variagatus, a mycorrhizal associate of Pinus sylvestris but not of Picea sitchensis, occurs in mixed planta­tions and may be able to degrade protein rapidly leaving 87% of the protein degradation products in solution, which may 'be available for uptake by the Sitka spruce.

Ryan, P.A. 1985. Hoop pine second rotation gr~h and nutrition. Paper presented to Second Rotation esyablishment: Problems, Possible Solutions and Identification of Research Needs Conference. Topic 2.2. Gyrrpie, ().leensland. Australia: Yield. Managerrent

Salwasser, H. 1985. Integrating wildlife into the managed forest. In: A Symposium on Forestry and Wildlife Managerrent in Canada. Forestry Chronicle, 146 - 149.

Salwasser, H. 1990. Sustainability as a conservation paradigm. Cons. Biology 4 (3): 213 ~ 215.

Sanraj, P.,Chinnamani., S. and Haldorai, B. 1977. Natural versus man-made forest in the Nilgiris with special reference to run-off, soil loss and productivity. Indian Forester 103: 460-465. India: Soils. Yield Run-off under Eucalyptus globulus and Acacia mearnsii was less than under natural forest, but rrore than protected grass plots and Cytisus scoparius plots. Yields of eucalyptus and wattle mixed, 700 stems/ha, 482 m3/ha at age 10 as against 322 m3 for Eucalyptus, 2500 stems/ha, and 125 m3 for wattle, 1600 stems/ha, in pure plantations.

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Sands, R. 1983. Physical changes to sandy soils planted to radiata pine.In: IUFRO Symposium on Forest Site and Continuous Productivity. p 146-152.

Australia: SoilsExamines the correlation between root growth and soil strength.Maintenance of soil organic matter is critical to productivity, both inincreasing field capacity, soil N and total CEC.

Savill, P.S. and EVans, J. 1986. Plantation silviculture in temperateregions with special reference to the British Isles. Clarendon Press,Oxford.Temperate region: TextbookDue to economic advantages, plantation forestry is dominated by pureevenaged plantations. Instances where mixtures may be suitable arediscussed.

Sdhlesinger, R.0 and William, R. D. 1984. Growth response of black walnutto interplanted trees. Forestry Ecology and Management 9 (3): 235-243.USA: YieldAt 13 years Elaea gnus, Robinia, Alnus glutinosa admixtures increasedblack walnut dbh at some locations (but not all). E. umbellata gave 56- 351% increase in 4 out of 5 locations in Illinois, Missouri andIndiana. All species resulted in a 100% increase on an upland site.

SChUbert, T.H. 1985. Preliminary results of Eucalyptus/legume mixtures inHawaii. Nitrogen Fixing Tree Research Reports 3: 65-66.Hawaii: YieldSummary of Eucalyptus/Albizia/Acacia mixtures reported by Debe 11 et al.Notes tests on proportions of each species used in mixture. In 50:50and 66:34 Ellca/yptus: Albizia mixtures, Eucalyptus dbh 6% to 15%greater than mixtures with higher proportions of Eucalyptus, but noinformation given on eucalyptus standing volumes.

Schutz, C.J. 1982. Mbnitoring the long-term effects of managementpractices on site productivity in South African forestry. South AfricanForestry Journal 120: 3-6.South Africa: Management, SoilsNo evidence of productivity decline attributable to managementpractices. There may eventuallybe problems of litter build up on poorsites under intensively managed stands.

Schutz, J.P. 1989. Zum problem in Aaschbestanden. Schweiz. Z. Forstwesen-140 (12): 1069-1083.Switzerland: YieldMixtures of spruce and beech are claimed tp grow better than purestands of either species.

Schutz, J.P. 1990. Die waldbaulichen Ateglichkeiten und Grenzen vonAaschbestockungen. (Silvicultural possibilities and limits of mixedforests.) IUFRO Wbrld Congress, Montreal.Switzerland: ManagementNatural trends towards diversity should be promoted.

Serrano, R.C., VIlLmmeva, T. R. and Sin, B. D. 1976. Surface run-off andsedimentation under Albizia falcataria, Anthocephalus chinensis andmixed secondary stands. Pterocarpus 2 (1): 35-46.Philippines: SoilsPure stands of A. falcataria gave by far the best protective cover.

ShainSky, L.J. and Radosevidh, S.R. 1988. Douglas fir and red alder com-petition in mixed and monoculture stands. Vegetation Competition andResponses. Proceedings 3rd Annual Vegetation Management Wbrkshop.Vancouver B.C., Canadian Forest Service. pp 2.North America: Environmental

111

Sands, R. 1983. Physical changes to sandy soils planted to radiata pine . In: IUFRO Syrrp:lSium on Forest Site and Continuous Productivity. p 146-152. Australia: Soils Examines the correlation between rcot growth and soil strength. Maintenance of soil organic matter is critical to productivity, both in increasing field capacity, soil N and total CEC .

Savill. , P.s. and Evans, J. 1986. Plantation silviculture in temperate regions with special reference to the British Isles. Clarendon Press, Oxford. Temperate region: Textbook Due to econanic advantages, plantation forestry is daninated by pure evenaged plantations. Instances where mixtures may be suitable are discussed.

Schlesinger, R.C and Williams, R.D. 1984. GrONtil response of black walnut to interplanted trees . Forestry Ecology and Management 9 (3): 235-243. USA : Yield At 13 years Elaeagnus, Robinia, Alnus glutinosa admixtures increased black walnut dbh at sane locations (but not all). E. umbellata gave 56 - 351% increase in4 out of 5 locations in IllinOiS, Missouri and Indiana. All species resulted in a 100% increase on an upland site .

Schubert, T. H. 1985. Preliminary results of Eucalyptus/legume mixtures in Hawaii . Nitrogen Fixing Tree Research Reports 3: 65-66. Hawaii : Yield Surrrnary of Eucalyptus/Albizia/Acacia mixtures reported by Debell et al. Notes tests on proportions of each species used in mixture . In 50:50 and 66:34 Eucalyptus: Albizia mixtures, Eucalyptus dbh 6% to 15% greater than mixtures with higher proportions of Eucalyptus, but no information given on eucalyptus standing volumes .

Sc1mtz, C.J. 1982. ~nitoring the long-tenn effects of management practices on site productivity in South African forestry . South African Forestry Journal 120: 3-6. South Africa: Management, Soils No evidence of productivity decline attributable to management practices. There may eventually be problems of litter build up on poor sites under intensively managed stands.

Sc1mtz, J.P. 1989. Zum problem in Mischbestanden. Schweiz. Z. Forstwesen · 140 (12): 1069-1083. SWitzerland: Yield Mixtures of spruce and beech are claimed to grow better than pure stands of either species .

Sc1mtz, J.P. 1990. Die waldbaulichen l>rJeglichkeiten lllld Grenzen von Mischbestockungen . (Silvicultural possibilities and limits of mixed forests.) IUFRO World Congress, ~treal. SWitzerland: Management Natural trends towards diversity should be promoted .

SezTano, R.C., Vi..l.l.amJeva, T.R. and Sims, B. D. 1976. Surface run-off and sed:imantation under Albizia falcataria, Anthocephalus chinensis and mixed secondary stands . Fterocarpus 2 (1) : 35- 46. Philippines: Soils Pure stands of A. falcataria gave by far the best protective cover.

Shainsky, L .J. and Radosevich, S.R. 1988. Douglas fir and red alder can­petition in mixed and monoculture stands. Vegetation Competition and Responses. Proceedings 3rd Armual Vegetation Management Workshop. Vancouver B. C., Canadian Forest Service. pp 2 . North America : Environmental

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Interactions of the two species planted at 1 to 16 trees/ne areexamined. Douglas fir at these densities reduced leaf area of alder asDouglas fir densities increased, but growth parameters of both specieswere primarily affected by alder densities.

Singh, A.K. and Totey, N.G. 1985. Physico-chemical properties of bhatasoils of Raipur (Madhya Pradesh) as affected by plantations ofdifferent species. Journal of Tropiral Forestry 1 (1): 61-69.India: SoilsPlantation soils are examined, Tectona grandis, EUcalyptus hybrid,EMblica officinalis and "miscellaneuos". CEC, exchangeable rations andorganic matter are higher under miscellaneous plantations, butstockings and growth are poor. The extent to which the soil effects canbe attributed to the tree cover is debatable.

Singh, A, K., Arun Prasad, Rhatri, P. K. am d Balvinder Singh 1987. Physico-Chemical properties of soils developed over gneissic rocks underdifferent forest covers in Nagri range of South Raipur (MadhyaPradesh). Journal of Tropical Forestry 3(1): 37-47.India: SoilsAn examination of four forest covers, teak, sal, miscellaneous withsal and miscellaneous without sal.

Singh, S.B., Nath, S., Pal, D.K. and Banerjee, S.K. 1985 Changes in soilproperties under different plantations of the Darjeeling forestDivision. Indian Forester 111 (2): 90-98.India: SoilsMixed vegetation reflected the best soil properties.

Singh, S.P. and Sharma, R.S. 1983. Permanent sample plots in stands ofmixed species. Indian Forester 109(7): 449-457.India: YieldsA high proportion of Trewia nudiflora, Tbcna ciliata and BOmbax ceibaresulted in larger volumes.

Siregar et al. 1986. Growth of SWietenia macrophylla and intercroppedLeucaenaleucocepha1a in the residual forest of Akdaleuca leucadendron.Leucaena Research Report 7: 82.Indonesia: YieldThe poor results may be due to allelopathy of Alaleuca leucadendron,drought stress or sulphur deficiency.

Smelyanetz, V.P., Lppatina, N.V. and Lomakin, M.D. 1981. Forestresistance to insect pests in relation to plant population patterns.Zeitschrift fuer angewandte Entomologie 92: (3): 217-244.USSR: Environmental, pests and diseasesIt is possible to use Pinus sylvestris as a diversionary plant withincultures of Pious pallasiana.

Smith, D.M. 1962. The practice of silviculture. John Wiley and Sons, 7thedition.Textbook: ManagementStratified mixtures should be used if intimate mixtures are to bemaintained in plantations. It is almost *possible to find species thatwill form single canopied mixtures.

Smith, I.W., Marks, G. C, Featherston, G. R. and Geary, P.W. 1989. Effectsof interplanted wattles on the establishment of eucalypts planted onforest sites affected by Phytophthora cinnamcni. Australian Forester 52(2): 74-81.Australia: Environmental, pests and diseases. YieldNo effects of the wattles on P. cinnamcni could be detected. Eucalyptsseemed to respond well in growth to the interplanted wattles.

112

Interactions of the two species planted at 1 to 16 trees/m" are examined. Douglas fir at these densities reduced leaf area of alder as Douglas fir densities increased, but grcMth parameters of both species were primarily affected by alder densities.

Singh, A.K. and 'l'otey, N.G. 1985. Physico-chemical properties of bhata soils of Raipur (Madhya Pradesh) as affected by p I ant a t ion s 0 f different species. Journal of Tropical Forestry 1 (1): 61-69. India : Soils Plantation soils are examined, Tectona grandis, Eucalyptus hybrid, Emblica officinalis and "miscellaneuos". CEC, exchangeable cations and organic matter are higher under miscellaneous plantations, but stockings and grCMth are poor . The extent to which the soil effects can be attributed to the tree cover is debatable.

Singh, A.K., AJ:un Prasad, Khatri, P.K. and BaJ.v:inder Singh 1987. Physico­chemical properties of soils developed over gneissic rocks under different forest covers in Nagri range of South Raipur (Madhya Pradesh). Journal of Tropical Forestry 3(1) : 37-47. India: Soils An examination of four forest covers, teak, sal, miscellaneous with sal and miscellaneous without sal.

Singh, S.B., Hath, S., Pal, D.K. and Banerjee, S.K. 1985 Changes in soil properties under different plantations of the Darjeeling forest Division. Indian Forester 111 (2): 90-98. India: Soils Mixed vegetation reflected the best soil properties.

Singh, S.P. and ShaJ:ma, R.S. 1983. Pennanent sample plots in stands of mixed species. Indian Forester 109(7): 449-457. India: Yields A high proportion of Trewia nudiflora, Toona ciliata and Bcrnl::ax ceiba resulted in larger volumes.

Siregar et al. 1986. GrCMth of SWietenia macrophylla and intercropped Leucaena leucocephala in the residual forest of Melaleuca leucadendron. I.eucaena Research Report 7: 82. Indonesia: Yield The poor results may be due to allelopathy of Melaleuca leucadendron, drought stress or sulphur deficiency.

5melyanetz, V.P., Iqlatina, N.V. and Lanakin, H. D. 1981. Forest resistance to insect pests in relation to plant population patterns. Zeitschrift fuer angewandte Entamologie 92: (3): 217-244. USSR: EnVironmental, pests and diseases It is possible to use Pinus sylvestris as a diversionary plant within cultures of Pinus pallasiana.

9Dith, D.H. 1962. The practice of silviculture. John Wiley and Sons, 7th edition. Textbook: Management Stratified mixtures should be used if intimate mixtures are to be maintained in plantations. It is alroost impossible to find species that will f onn single canopied mixtures.

9Dith, I.w., Marks, G.C, Featherston, G.R. and Geary, P.W. 1989. Effects of interplanted wattles on the establishment of eucalypts planted on forest sites affected by Phytophthora cinnamoni. Australian Forester 52 (2): 74-81. Australia: Environmental, pests and diseases. Yield No effects of the wattles on P. cinnarroni could be detected. Eucalypts seemed to respond well in grCMth to the interplanted wattles.

113

Soares, R.V. 1991. Ecological and economic consequences of forest fire:the Brazilian example. Theme 5.3, 10th World Forestry Congress, Paris,1991. Proceedings Vb1.2: 471-480.Brazil: Fire

Solomon Islands 1988a. Notes on the use of mixtures and nurse crops in theestablishment of plantations of high value spp. Forestry Note 30 7/88,Forest Department.

Solomon Islands 1988b. The status of Securine9a flexuosa MUell. Arg.Forest Research Note 46 14/88, Forest Department.Solomon Islands: ManagementSwietenia macrqphylla planted with Securinega flexuosa, S.samcana,Leucaena leucocephala, Trminalia calamansanai, Schleinitschia nova-guinensis, Glyricidia sepium to overcome hypsipylla shoot borer.Spacing 3x4m or 3x5m. S.flexuosa most promising.

Soule, /4.E. Ed. 1986. Conservation biology: science of scarcity anddiversity. Sinauer Associates, Sunderland, Mass. U.S.A.

Spears, J.S. 1985. Deforestation issues in developing countries. The casefor an accelerated investment program. Proceedings of the TwelfthCommonwealth Forestry Conference. pp 47-59.General: Economics

Sprent, J.I. 1985. Nitrogen fixation in arid environments. In: Plants forArid Lands. George Allen and Unwin, London.General: SoilsData on the nodulation ratio of N-fixing plants. Dry soils often highinNas nitrate. Deep rooted N-fixers (Frosqpis) may contribute to highnitrate levels through mineralisation of litter. Legumes require mois-ture and will not fix N under stress.

Squire, R.O. 1983. Review of second rotation silviculture of Finusradiata in southern Australia: Establishment and expectations. In:

IUFRO Symposium on Forest Site and Continuous Productivity, Seattle,Washington, August 1982. General Technical Report, Pacific NorthwestForest and Range EXperiment Station, US Dept. of Agriculture ForestService (1983), No. PNW-163.Australia: SoilsImproved performance of second rotation crops in recent years as-sociated with increased availability of water (mulching) and increasednutrients (fertiliser application, use of legumes and leaving loggingresidues). Nitrogen can promote increased water efficiency by itseffect on the stomata.

Statham, P. 1990. The Sandalwood industry in Australia: a history. InProceedings of the Symposium on Sandalwood in the Pacific, April 1990,Hbnolulu,Hawaii. US Department of Agriculture, Forest Service, GeneralTechnical Report PSW-122. p 26-38.Australia: exploitationA history of exploitation in Australia.

Steinbedk, K. ami Skinner, T.M. 1984. Growing short-rotation forests inthe southeastern USA. In: Bioenergy 84. Proceedings of conference June1984 Goteborg, Sweden. Vol II. Biomass Resources. ElsevierApplied Science Publishers.USA: SoilsMixtures of Platanus occidentalis and Liquidambar styTaciflua with N-fixers Alnus glutinosa and Robinia pseucloacacia. After 5 years noconsistent differential effects of tree species on soil nutrients, pHor organic matter. Ladk of soil N accretion probably caused by rapidgrowth of R.pseudbacacia and poor survival of A. glutinosa.

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Soares, R. V. 1991. Ecological and econanic consequences of forest fire : the Brazilian exartqJle. Theme 5.3, 10th World Forestry Congress, Paris, 1991. Proceedings Vol . 2: 471-480. Brazil: Fire

Solanan Islands 1988a. Notes on the use of mixtures and nurse crops in the establishment of plantations of high value spp . Forestry Note 30 7/88, Forest DepartIrent.

Solaron. Islands 1988b. The status of Securinega flexuosa Muell. Arg. Forest Research Note 46 14/88, Forest DepartIrent. Solaron Islands: Management SWietenia macrophylla planted with Securinega flexuosa, S .samoana, Leucaena leucocephala, Te:rminalia calamansanai, Schleinitschia novo­guinensis, Glyricidia sepium to overcare Hypsipylla shoot lx>rer. Spacing 3x4m or 3x5m. S.flexuosa IlDst pranising.

Soule, M.E. Ed. 1986. Conservation biology: science of scarcity and diversity. Sinauer Associates, Sunderland, Mass. U.S.A .

Spears, J . S. 1985 . Deforestation issues in developing countries. The case for an accelerated investment program. Proceedings of the 'lWelfth COiIoonwealth Forestry Conference. pp 47-59. General: Econanics

Sprent, J.I. 1985. Nitrogen fixation in arid envirornnents. In : Plants for Arid Lands. George Allen and Unwin, London . General: Soils Data on the nodulation ratio of N-fixing plants. Dry soils often high in N as nitrate. Deep rooted N-fixers (Prosopis) may contribJ.te to high nitrate levels through mineralisation of litter . Legumes require IlDis­ture and will not fix N under stress.

Squire, R.O. 1983. Review of second rotation silviculture of Pinus radiata in southern Australia : Establishment and expectations. In: IUFRO Symposium on Forest Site and Continuous Productivity, Seattle, Washington, August 1982. General Technical Report, Pacific Northwest Forest and Range Experiment Station, US Dept. of Agriculture Forest Service (1983), No . PNW-163 . Australia: Soils Improved perfonnance of second rotation crops in recent years as­sociated with increased availability of water (Imllching) and increased nutrients (fertiliser application, use of legurres and leaving logging residues). Nitrogen can prarote increased water efficiency by its effect on the stomata.

Statham, P . 1990. The Sandalwood industry in Australia: a history . In Proceedings of the Symposium on Sandalwood in the Pacific, April 1990, Honolulu, Hawaii. US DepartIrent of Agriculture, Forest Service, General Technical Report PSW-122. P 26-38. Australia: explOitation A history of explOitation in Australia .

steinbeck, K. and Skinner, T.M. 1984. Gr<Ming short-rotation forests in the southeastern USA. In: Bioenergy 84. Proceedings of conference June 1984 Gotelx>rg, SWeden. Vol II. Biomass Resources. Elsevier Applied Science Publishers. USA: Soils Mixtures of platanus occidentalis and Liqui~ styraciflua with N­fixers Alnus glutinosa and Robinia pseudoacacia. After 5 years no consistent differential effects of tree species on soil nutrients, pH or organic matter. Lack of soil N accretion probably caused by rapid grCMth of R.pseudoacacia and poor survival of A.glutinosa.

114

Streets, R.J. 1962. Exotic forest trees in the British Commonwealth.Clarendon Press, Oxford.General: Management

Styles, B.T. 1991. Personal communication.Sweet, G.B. and Burdon, R.D. 1983. The radiata pine monoculture: an

examination of the ideologies. New Zealand Journal of Forestry 28 (3):325-326.New Zealand: General

Tasmania Forestry Commission 1989. Forest Practices Code (draft).Forestry Commission, Tasmania. pp 89.Australia: ManagementA detailed code of practice for logging native forests.

Tham, A. 1988. Yield prediction after heavy thinning of birch in mixedstands of Nbrway spruce (Picea abies (L) Karst.) and birch (Betulapendula Roth and Eetula pubescer2s Ehrh.). Swedish University ofAgricultural Sciences, Department of Yield Research, Report 23.Sweden: Yield. ManagementThe highest total yield was found when spruce was mixed with a shelter-wood of 800 birch/ha. At higher densities spruce production was lowerthan in a pure spruce stand. A shelterwood of 500-600 birches/ha isrecommended. The shelterwood should be retained for 20-30 years.

Thomas, J.W. 1979. Wildlife habitats in managed forests, the Blue Mountainsof Oregon and Washington. Agric. Handbook No. 533. pp. 512. USDA:Forest Service.

Tisseverasinghe, A.E.K. and Satchithananthan, S. 1957. The management ofSundapola plantation. Ceylon Forester 3 (1): 82-93.Sri Lanka: Management. YieldA summary of data from a 50 year old mixed plantation of Artccarpusintegrifolius and SWietenia macrpphylla.

Tiwari, K.M. 1970. Interim results of intercropping miscellaneous specieswith main crop of taungya plantations to increase the productivity.Indian Forester 96 (9): 650-653.India: YieldMultipurpose species have been introduced in the interspaces of saltaungya lines. An additional yield of approx. 1 tonne/ha/yr wasobtained on a four-year rotation. Species used include Albiziaprocera,Eautinia variegata, Cassia fístula and Ougenia oojensis.

Tourney, J.W. 1947. Foundations of silviculture upon an ecological basis.John Wiley and Sons.General: TextbookA textbook with a detailed discussion about mixed stands.

Tu, M.Z. and Yao, W.H. 1984. Studies on the influences of soil pH bydifferent plant communities. Tropical and SUbtropical Forest Ecosystem,Ding HU Shan Forest Ecosystem Station, China 2: 110-113.China: SoilsA study of 26 plantations showed that a mixture of legumes and non-legumes increased pH. Ealbergia odorifera and Cassia siamea gave bestresults. Planting Calamus tetradactylus recommended to increase pH andprofits.

TUrner, J. 1983. Maintenance and improvement of forest productivity inAustralia. In: IUFRO Symposium on Forest Site and ContinuousProductivity, Seattle, Washington, August 1982. General TechnicalReport, Pacific Northwest Forest and Range Experiment Station, US Dept.of Agriculture Forest Service (1983), No. PNW-163.Australia: Soils. Management

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streets, R.J. 1962. Exotic forest trees in the British Commonwealth. Clarendon Press, OXford. General: Management

styles, B.T. 1991. Personal ccmnunication. SWeet, G.B. and Burden, R.D. 1983. The radiata pine Il'OIloculture: an

examination of the ideologies. New Zealand Journal of Forestry 28 (3): 325-326. New Zealand: General

Tasmania Forestry Camri ssion 1989. Forest Practices Code (draft) . Forestry Cammission, Tasmania . pp 89. Australia: Management A detailed code of practice for logging native forests.

ThaIn, A. 1988. Yield prediction after heavy thinning of birch in mixed stands of Norway spruce (Picea abies (L) Karst.) and birch (Betula pendula Roth and Betula pubescens Ehrh.). SWedish University of Agricultural Sciences, Department of Yield Research, Report 23. SWeden: Yield. Management The highest total yield was found when spruce was mixed with a shelter­wood of 800 birch/ha. At higher densities spruce production was ICMer than in a pure spruce stand . A shelterwood of 500-600 birches/ha is recommended. The shelterwood should be retained for 20-30 years.

11Ianas, J .W. 1979. Wildlife habitats in managed forests, the Blue M:Juntains of Oregon and washington. Agric. Handbook No. 533. pp. 512. USDA: Forest Service.

Tisseverasinghe, A.E.X. and Satchithananthan, S. 1957. The management of Sundapola plantation. Ceylon Forester 3 (1): 82-93. Sri Lanka: Management. Yield A sumnary of data fran a 50 year old mixed plantation of Artocarpus integrifolius and SWietenia ma.=phylla.

Tiwari, X.K. 1970. Interim results of intercropping miscellaneous species with main crop of taungya plantations to increase the productivity. Indian Forester 96 (9): 650-653. India: Yield MLlltipurpose species have been introduced in the interspaces of sal taungya lines. An additional yield of approx. 1 tonne/ha/yr was obtained on a four-year rotation. Species used include Albizia procera, Bauhinia variegata, Cassia fistula and Ougenia oojensis.

Tourney, J.W. 1947. Foundations of silviculture upon an ecological basis. John Wiley and Sons. General: Textbook A textbook with a detailed discussion about mixed stands.

'lU, K.Z. and Yao, W.H. 1984. Studies on the influences of soil pH by different plant ccmnunities. Tropical and Subtropical Forest Ecosystem, Ding Hu Shan Forest Ecosystem Station, China 2: 110-113. China: Soils A study of 26 plantatiOns showed that a mixture of legumes and non­legumes increased pH. Dalbergia odorifera and Cassia siamea gave best results. Planting calamus tetradactylus recommended to increase pH and profits.

Turner, J. 1983. Maintenance and improvement of forest productivity in Australia. In: IUFRO Symposium on Forest Site and Continuous Productivity, Seattle, Washington, August 1982. General Technical Report, Pacific Northwest Forest and Range Experiment Station, US Dept. of Agriculture Forest Service (1983), No. PNW-163. Australia: Soils. Management

115

DescribPs silvicultural activities (site preparation, weeding,fertiliser application) to enhance productivity. Major gains inproductivity are made in the establishment phase.

TUrvey, Attiwill, PJM., Cameron, J.N. and Smethurst, P.J. 1984.Growth of planted pine trees in response to variation in the densitiesof naturally regenerated acacias. Forest Ecology and Management (7):103-107.Australia: Soils. ManagementNo growth benefits to the pine could be detected. It is speculated thatacacia is not the most appropriate nitrogen fixer to be used.

Uhart, E. 1962. Les reboisement et le développement de Madagascar.(Reafforestation and development of Madagascar.) Bois et Forêts deTropiques No. 83: 15-29.Madagascar: ManagementA policy of reforestation in MadagascAr is discussed.

Un, C.R., Bing, J.Y. and YUng, N.Y. 1979. Study in mixed planting.Qparterly Journal of Chinese Forestry.China: ManagementTaiwan ja cryptomerioides and Faulownia taiwania in mixture.

Vélez, R. 1991. Uso del fuego en selvicultura. Paper, Theme 5.2, 10thWorld Forestry Congress, Paris, 1991. Proceedings V01.2: 461-470.General: Fire

Villamar, C.A. 1979. Silvipasture establishment for range type productionof water buffalo. Sylvatrop Phillipine Forest Research Journal 4 (1)pp17-21.Philippines: ManagementLeucaena leucocephala (1,360/ha, 82% survival) and GMelina arborea(202/ha, 52% survival) in Stylosanthes guyanensis and Themeda triandragrasslands.

Vink, A.T. 1970. Forestry in Suriname. Landbosbeheer, Suriname ForestService.Suriname: ManagementRather intensive systems of enrichment- and strip-planting aredescribed.

Voogd, C.N.A. de 1928. Over Aunstmatige menging van djati REt wildhout.(On artificial mixing of teak.) Tectona 21: 527-533. Noted in In-donesian Forestry Abstracts, PUDOC, Wageningen, 1982. Abstract 612.Indonesia: ManagementMixing advantages can be obtained by mixing with species growing justbelow the teak trees. Mixing species should stay green during the dryseason, be easy to grow and produce a marketable product.

VOron, P. 1979. The effect of industrial air pollution on the health offorest plantations in the Carpathian foothills. Lesovodstvo i Agrole-sameiioratsiya 53: 53-57.USSR: EnvironmentalIn a study of pollution effects mixed stands were more resistant thanpure.

Waage, J. 1990. Exploration of biological control agents of LeucaenaPsyllid in tropical America. F/FRED Coordinating Unit, Bangkok.pp 144-152.Central America: PestsDescribes the insect and its predators in the native range.

Watt, A. 1990. Insect pest population dynamics effects of tree speciesdiversity. In Ecology of Mixed Species Stands of Trees. BritishEcological Society and IUFRO Div 2.01 Symposium, Edinburgh.UK: Environmental, pests and diseases

115

Describes silvicultural activities (site preparation, weeding, fertiliser application) to enhance productivity. Major gains in productivity are made in the establishment phase.

Turvey, N.D., Attiwill, P.M., Cameron, J.N. and smethurst, P.J. 1984. GrcMth of planted pine trees in response to variation in the densities of naturally regenerated acacias. Forest Ecology and Management (7): 103-107. AUstralia: Soils. Management No grcMth benefits to the pine could be detected. It is speculated that acacia is not the IOClSt appropriate nitrogen fixer to be used.

Uhart, E. 1962. Ies reboisement et le developpEmeI1t de Madagascar. (Reafforestation and developrent of Madagascar.) Bois et Forets de Tropiques No. 83: 15-29. Madagascar: Management A policy of reforestation in Madagascar is discussed.

Un, C.R., Bing, J.Y. and Yung, N.Y. 1979. study in mixed planting. Quarterly Journal of Chinese Forestry. China: Management Tciiwania cryptanerioides and Paulownia taiwania in mixture.

Velez, R. 1991. Uso del fuego en sel vicul tura. Paper, Theme 5 .2, 10th World Forestry Congress, Paris, 1991. Proceedings Vol.2: 461-470. General: Fire

Vi11amar, C.A. 1979. Silvipasture establishment for range type production of water J::uffalo. Sylvatrop Phillipine Forest Research Journal 4 (1) pp 17-21 .. Philippines: Management Ieucaena leucocephala (1,360/ha, 82% survival) and Gnelina arl:xJrea (202/ha, 52% survival) in Stylosanthes guyanensis and Themeda triandra grasslands.

Vink, A.T. 1970. Forestry in Suriname. Landbosbeheer, Suriname Forest Service. Suriname: Management Rather intensive systems of enrichment- and strip-planting are described.

Voogd, C.N.A. de 1928. Over kunstmatige IIEllging van djati met wildhout. (On artificial mixing of teak.) Tectona 21: 527-533. Noted in In­donesian Forestry Abstracts, PUL'OC, Wageningen, 1982. Abstract 612. Indonesia: Management Mixing advantages can be obtained by mixing with species growing just below the teak trees. Mixing species should stay green during the dry season, be easy to grow and produce a marketable product.

VODOn, P. 1979. The effect of industrial air pollution on the health of forest plantations in the carpathian fcothills. Lesovodstvo i Agrole­sameiioratsiya 53: 53-57. USSR: Environmental In a study of pollution effects mixed stands were rrore resistant than pure.

waage, J. 1990. Exploration of biological control agents of Ieucaena Psyllid in tropical Arrerica. F/FRED Coordinating Unit, Bangkok. pp 144-152. Central Arrerica: Pests Describes the insect and its predators in the native range.

watt, A. 1990. Insect pest population dynamics effects of tree species diversity. In Ecology of Mixed Species Stands of Trees. British Ecological Society and IUFRO Di v 2.01 Symposium, Edinburgh. UK: Environmental, pests and diseases

116

Way, /4.J. 1977. Pest and disease status in mixed stands vs. monocultures;the relevance of ecosystem stability. In: The Origin of Pest, Parasite,Disease and Weed Problems. pp 127-138, Blackwell, Oxford.Environmental: Pests and diseasesIt is emphasized that diversity in itself is no guarantee against pestsand diseases. Diversity may decrease attacks through provisioncamouflage, barriers, hazards or alternative hosts.

Wrepf, W. 1955. Het begrip menging in djaticulturen. (Mixing in teakplantations.) Tectona 43: 290-294. Noted in Indonesian Forestry Abs-tracts, PUDOC, Wageningen, 1982. Abstract 596.Indonesia: ManagementThe aim of mixing should be a luxuriant undelyrowth. Use should be madeof the natural plant community.

Whitehead, D. 1981. An ecological overview of plantation forestry. NewZealand Journal of Forestry 26 (1): 14-19.New Zealand: Environmental, ecologyThe ecological hazards of plantation forestry are discussed. Sane ofthe criticism of plantation forestry found to be unjustified.

Whitehead, D. 1982. Ecological aspects of natural and plantation forests.Forestry Abstracts 143 (10): 615-624.New Zealand: Environmental, ecologyHigh diversity does not always result in high stability and produc-tivity. There are examples of pure stands with stable structures.

Whitmore, J.L. 1973. Myths regarding Hypsipyla and its host plants. In:First Symposium on Integrated Control of Hypsipyla. IICA-CTEI-Turrial-ba, Costa Rica.Environmental, Pests and diseasesQuantification studies are needed to learn whether, and if so how much,less shaded seedlings are attacked by Hypsipyla.

Whitmore, J.L. 1991. Personal communication.Whitmore, T.C. 1984. Tropical Rain Forests of the Far East (2nd ed.).

Oxford University Press (UK) pp 352.Far East: EcologyA text book of rain forest ecology.

Wilcox, B.A. 1982. lh situ conservation of genetic resources:determinants of minimum area requirements. In: World National ParksCongress, Bali 18 - 30. New Directions.

Wilde, S.A. 1964. Changes in soil productivity induced by pineplantations. Soil Science 97: 276-278USA: SoilsAnalysis of 156 Pinus Lanksiana, P. resinosa, P. strobus stands, 10-50years old. By far the best indicator of fertility status of reforestedsoil is the content of organic matter, strongly correlated with CEC andtotal N supply. After age 35-40 years, pine stands usually correct tem-porary soil deficiencies caused by logging, burning etc.

Will, G.M. 1964. Dry matter production and nutrient uptake by Pinv7radiate in New Zealand. Commonwealth Forestry Review 43: 57-70New Zealand: Soils. YieldRooting to 6 m in pumice soils. High growth rate attributable to highrainfall (1500 mm) and high solar energy. Annual increment of drymatter 20 tons/ha (Site Quality II) to 45 tons (Site Quality I).Maximum growth the first 10 years. Thereafter no fertilization isnecessary, decomposing litter and slash meet most of trees' demands.

Will, G.M. and Ballard, R. 1976. Radiata pine soil degrader or improver?New Zealand Journal of Forestry 21 (2): 248-252.New Zealand: Soils

116

way, M.J. 1977. Pest and disease status in mixed stands vs. rronocultures; the relevance of eoosystem stability. In : The Origin of Pest, Parasite, Disease and Weed Problems . pp 127-138, Blackwell, OXford. Environmental: Pests and diseases It is arphasized that diversity in itself is no guarantee against pests and diseases. Diversity nay decrease attacks through prevision carrouflage, barriers, hazards or alternative hosts.

Wepf, W. 1955. Het begrip menging in djaticulturen . (Mixing in teak plantations.) Tectona 43: 290-294. Noted in Indonesian Forestry Abs­tracts, PUIXlC, Wageningen, 1982 . Abstract 596. Indonesia: Management The aim of mixing should be a luxuriant undergrcMth. Use should be nade of the natural plant oomrnunity.

Whitehead, D. 1981. An ecological overview of plantation forestry. New Zealand Journal of Forestry 26 (1): 14-19. New Zealand: Envirernnental, ecology The ecological hazards of plantation forestry are discussed. Sane of the criticism of plantation forestry found to be unjustified.

Whitehead, D. 1982. Ecological aspects of natural and plantation forests. Forestry Abstracts 143 (10): 615-624. New Zealand: Envirernnental, ecology High diversity does not always result in high stability and produc­tivity . There are examples of pure stands with stable structures .

Whitmlre, J.L. 1973. Myths regarding Hypsipyla and its host plants. In: First Sympcsium on Integrated Control of Hypsipyla. IlCA-erEI -Turrial­ba, Costa Rica. Environmental, Pests and diseases Q,.lantification studies are needed to learn whether, and if so ho.T much, less shaded seedlings are attacked by Hypsipyla.

Whitmlre, J.L. 1991. Personal crnrnunication . Whitmlre, T.e. 1984. Tropical Rain Forests of the Far East (2nd ed.).

OXford University Press (UK) pp 352. Far East: Ecology A text book of rain forest ecology.

Wilcox, B.A. 1982. In situ conservation determinants of minimum area requirements. Congress, Bali 18 - 30. New Directions.

of genetiC resources: In: World National Parks

Wilde, S.A. 1964. Changes in soil productivity induced by pine plantatiOns. Soil Science 97: 276-278 USA: Soils Analysis of 156 Pinus banksiana, P. resinosa, P. strobus stands, 10-50 years old. By far the best indicator of fertility status of reforested soil is the content of organic natter, strongly co=elated with CEC and total N supply. After age 35-40 years, pine stands usually co=ect tem­porary soil deficiencies caused by logging, burning etc.

Will, G.M. 1964. Dry natter production and nutrient uptake by Pinus radiata in New Zealand. Ccmnonwealth Forestry Review 43: 57-70 New Zealand: Soils. Yield Rooting to 6 m in pumice soils. High gro.Tth rate attributable to high rainfall (1500 nrn) and high solar energy. Annual increment of dry natter 20 tons/ha (Site Q.Jality II) to 45 tons (Site Q.Jality I). Maximum gro.Tth the first 10 years. Thereafter no fertilization is necessary, decanposing litter and slash meet rrost of trees' demands.

Will, G.M. and Ballard, R. 1976. Radiata pine soil degrader or inprover? New Zealand Journal of Forestry 21 (2): 248-252. New Zealand: Soils

117

Where soil deterioration has been observed under pure coniferousforests, it has been caused by mismanagement and exploitation.This can be rectified by fertilizers.

Williamson, ML 1990. War and forests: South Vietnam. New Zealand Forestry:18-21.Viet Nam: ManagementDipterocarps (Dipterocarpus alatus and Hopea odorata) under a nursecrop of Acacia auriculifOrmis.

Wilson, E.O. (Ed). 1988. Biodiversity. National Academic Press,Washington, D.C. 521 pp.

Wilson, W.L. and Johns, A.D. 1982. Diversity and abundance of selectedanimal species in undisturbed forest, selectively logged forest andplantations in East Kalimantan, Indonesia. Biological Conservation 24:205-218.Indonesia: WildlifeSmall plantations (6 to 24 months old) of Pinus, EUcalyptus,Anthocephalus and Paraserianthes. Wildlife using plantations came infrom surrounding forest, few can survive in a monoculture.

Wilten, W. 1955. Aspects dé la sylviculture au NJ.4yumbé. Bull. Agric.Congo-Beige Vol 46 (2): 319-328.Zaire: Management, regenerationMethods of raising Temlnalia superte are explained.

WiMbush, S.H. 1945. The management of cypress plantations in Kenya.

Forest Department of Kenya, Pamphlet No. 11.Kenya: Management. Environmental, pests and diseasesBecause of the perceived hazards of pure cypress plantations, mixingcypress with broadleaves is recommended. Grevillea robusta is one ofthe species recommended. A regime is proposed.

Woinarsky, J.C.Z. 1979. Birds of a eucalyptus plantation and adjacentnatural forest. Australian Forester Vol. 42 (4): 243-247.Australia: WildlifeDiversity was compared between a plantation of Eucalyptus Lotryoidesand an adjacent natural forest of mixed Euralyptus dives species.Diversity was slightly higher in the natural forest.

Wbod, P.J. and Dawkins, H.C. 1971. Forest monocultures in the tropics -ecological anxieties. Mimeographed Report, Oxford Forestry InstituteLibrary. pp 3.Tropics: ManagementPlantation establishment is uncommon in polyspecific forests. Erosioncan be serious on sandy soils. Deep rooted plantations transpire morewater than grassland, but the effect of grazing, trampling or burningis more serious than the type of cover. Exclusion of large wild 1decauses overconcentration elsewhere.

WUelisch, G. von, Mbhs, H.J. and Gébarek, T. 1990. Competitive behaviourof clones of Picea abies in monoclonal mosaics vs. intimate clonalmixtures. Scandinavian Journal of Forest Research, 5(3): 397-402.Germany: YieldCompetitive effect of clones of different provenances growing mono-clonally or in mixture was examined. Competitive differences weredetected. Positive competitive reactions can raise yields, and reducerisks through genetic diversity.

Young, A. 1976. Tropical Soils and Soil Survey. Cambridge UniversityPress (UK).The tropics: SoilsA text book on tropical soils.

117

Where soil deterioration has been observed under pure coniferous forests, it has been caused by mismanagement and exploitation. This can be rectified by fertilizers .

Williamson, M. 1990. War and forests: South Vietnam. New Zealand Forestry: 18-21. Viet Narn: Management Dipterocarps (DipterocaIpus alatus and Hopea oiorata) under a nurse crop of Acacia auriculiformis.

Wilson, E.O. (Ed). 1988. Biodiversity. Nati onal Academic Press, Washington, D.C. 521 pp.

Wilson, W. L. and JaIms, A.D. 1982. Diversity and ab..mdance of selected animal species in undisturbed forest, selectively logged forest and plantatiOns in East Kalimantan, Indonesia. Biological Conservation 24: 205-218. Indonesia : Wildlife Snall plantations (6 to 24 rronths old) of Pinus, Eucalyptus, Gnelina, Anthocephalus and Paraserianthes . Wildlife using plantations a:rne in fran surrounding forest, few can survive in a rronoculture.

W:il.ten, W. 1955. Aspects de la sylviculture au Mayumbe. Bull. Agric. Congo-BeIge Vol 46 (2) : 319-328 . Zaire : Management, regeneration Methods of raiSing Teminalia superba. are explained.

Wj mb ISh, S.H. 1945. The management of cypress plantations in Kenya. Forest Department of Kenya, Panphlet No. 11. Kenya: Management . EnVironmental, pests and diseases Because of the perceived hazards of pure cypress plantations, mixing cypress with broadleaves is recammended. Grevillea robusta is one of the species recammended. A regime is proposed.

Woinarsky, J . C. Z. 1979. Birds of a eucalyptus plantation and adjacent natural forest. Australian Forester Vol. 42 (4) : 243-247 . Australia : Wildlife Diversity was canpared between a plantation of Eucalyptus botryoides and an adjacent natural forest of mixed Eucalyptus dives species. Diversity was slightly higher in the natural forest.

Wood, P.J. and Dawkins, H.C. 1971. Forest rronocultures in the tropics -ecological anxieties. Mimeographed Report, Oxford Forestry Institute Library. pp 3. Tropics : Management plantation establishment is uncarrnon in pol yspecific forests. Erosion can be serious on sandy soils . Deep rooted plantations transpire rrore water than grassland, but the effect of grazing, tranpling or burning is rrore serious than the type of cover. Excl usion of large wild life causes overconcentration elsewhere .

\rAlplisclt, G. von, !tJhs, H.J. and Gebarek, T. 1990. Crnlpetitive behaviour ,of clones of Picea abies in rronoclonal rrosaics vs. intimate clonal mixtures . Scandinavian Journal of Forest Research, 5(3): 397-402. Gennany: Yield Crnlpetitive effect of clones of different provenances growing rrono­clonally or in mixture was examined. Crnlpetitive differences were detected . Positive canpetitive reactions can raise yields, and reduce risks through genetic diversity.

Young, A. 1976. Tropical Soils and Soil Survey. Cambridge University Press (UK). The tropics: Soils A text book on tropical soils.

118

Zhai, Xia, Z.Y. and Cao, Y.Y. 1987. Element contents and theirannual and seasonal variations in the leaves of trees in PinustabulaefOrmis plantations. Scientia Silvae Sinicae 23(3): 286-298.China: SoilsLevels of N, P, K, Ca and Mg were 5% to 317% higher in Acer truncatumleaves than in the pine. It is concluded that the maple is a suitablespecies for growing in mixture with the pine.

Zhang Xian, XU Guang, Zhen Hong, Zhon XU and Zhon Chong. 1980. Repeatedplanting of Cunninghamia lanceo] ata and soil toxicity. In Ecologicalstudies on the artificial C.lanceolata forests. Institute of Forestryand Pedology. Academia Sineca.China: SoilsRepeatedplanting of C.lanceolata results in "soil sickness" attributedto "more intense activity on the oxidation of certain polyphenolcompounds containing methoxyl".

Zwaan, J.C. de. 1981. The silviculture of bladkwood (Acacia medancxylcn).South African Forestry Journal 121: 38-43.South Africa: ManagementA review of the performance and requirements of bladkwood. Mixture withPinus radiata being tried because that species was thought to be deeperrooting and more wind stable, but proved just as liable to wind throw.Blackwood/Eucalyptus (E.diversicolor and E. microcorys) mixtures alsounsuccessful, bladkwood suppressed.

Zwolinski, J.B. 1990. Intensive silviculture and yield stability in treeplantations: an ecological perspective. South African Forestry Journal155: 33-36.General: Environmental, ecologyPuts silviculture of plantations in an ecological setting andrecommends some ecologically sound practices.

118

Zhai, M.P., Xia, Z.Y. and Cao, Y.Y. 1987. Element contents and their amlUal and seasonal variations in the leaves of trees in Pinus tabulaefoLmis plantations. Scientia Silvae Sinicae 23(3): 286-298. China: Soils Levels of N, P, K, Ca and Mg were 5% to 317% higher in Acer tnmcatum leaves than in the pine. It is concluded that the maple is a suitable species for growing in mixture with the pine.

Zhang Xian, XU Guang, Zhen Hong, Zhon XU and Zhon ~. 1980. Repeated planting of CUnninghamia lanceolata and soil toxicity. In Ecological studies on the artificial C.lanceolata forests. Institute of Fbrestry and Pedology. Academia Sineca. China: Soils Repeated planting of C.lanceolata results in "soil sickness" attril:uted .to "rrore intense activity on the oxidation of certain polyphenol cClrqxlUnds containing methoxyl".

ZWaan, J.e. de. 1981. The silviculture of blackwood (Acacia melanoxylon). South African Forestry Journal 121: 38-43. South Africa: Management A review of the perforrrance and requirements of blackwood . Mixture with Pinus radiata being tried because that species was thought to be deeper rooting and rrore wind stable, rut proved just as liable to wind thrCM. Blackwood/Eucalyptus (E.diversicolor and E. microco.rys) mixtures also unsuccessful, blackwood suppressed.

ZWolinski, J.B. 1990. Intensive silviculture and yield stability in tree plantatiOns: an ecological perspective . South African Fbrestry Journal 155: 33-36. General: Environmental, ecology Puts silviculture of plantatiOns in an ecological setting and re~ds sare ecologically sound practices .

119

APPENDIX 2

SOILS

One of the major concerns expressed on the risk of creating monospecificplantations is that they canse a loss of fertility and soil degradation. It

is therefore worth considering in some detail the salient features of soilson which afforestation in the tropics and sub-tropics mostly takes place andthe interaction between tree crops and the soil.

Same characteristics of tropical soils.

The sites used for forest plantations in the tropics are, as elsewhere,often only available because they are unsuited to agriculture or have beenmade available for plantations after being degraded by poor agriculturalpractices. The soils tend to have certain common characteristics.

Ferralsols and Acrisols are the biggest soil groups in the tropicsaccounting between them for 37% of tropical soils. They are old soils, oftendeep, but intenselyweathered and therefore lacking in prirrary minerals whichprovide the reserves of nutrients needed for plant life. They are leached ofnutrients particularly on sites subject to high rainfall and are acidic whichadversely affects the capacity of the topsoil to hold nutrients in a formavailable for plant use. Nevertheless under undisturbed forest vegetationthese soils are capable of carrying a large volume of vegetation on the higherrainfall sites because the nutrient supply available in solution in thetopsoil is maintained by the rapid decomposition and mineralization of thelitter layer on the soil surface. Even in the drier phases of these soils(mionibo in Africa, c=rado in South America) where fires are frequent adequatefertility can be maintained if the organic matter content of the soils is notgrossly depleted.

Disturbance of these sites, whether for agriculture or by clearing forforest plantations, involves the risk of damaging the soil structure,.particularly if heavy machinery is used. Exposure of the soil and removal oforganic matter by, for example burning, both damages the soil structure andpromotes the loss of nutrients through leaching.

Arenosols and Regosols forma small proportion of tropical soils. Theyare coarse textured sandy soils having a low nutrient content and low waterretaining capability; as such they are of marginal use to agriculture and aretherefore often available for forest plantations.

Lithosols and the lithic (stony and shallow) phase of other soils arecommon in the tropics. These soils are frequently subject to agriculturalmismanagement on steep hillsides. Though seldom suitable for large scalecommercial forest plantations, forestry may be the most appropriate land useto rehabilitate them. Accumulation of organic matter promotes soil formation.

Nitosols, clayey red tropical soils, are more fertile than theferralsols and acrisols and are mostly under agricultural crops, but in thehighlands of East Africa many of the conifer plantations have been establishedon nitosols unsuited to agriculture by reason of steep slopes or highaltitudes and law temperatures. These soils are less prone to nutrientdeficiencies, but are liable to erosion if mismanaged.

119

APPENDIX 2

son.s

One of the major concerns expressed on the risk of creating Il'Onospecific plantations is that they cause a loss of fertility and soil degradation. It is therefore worth considering in sane detail the salient features of soils on which afforestation in the tropics and sub-tropics Il'Ostly takes place and the interaction between tree crops and the soil.

Sane characteristics of trqlical soils .

The sites used for forest plantations in the tropics are, as elsewhere, often only available because they are unsuited to agriculture or have been made available for plantations after being degraded by poor agricultural practices . The soils tend to have certain CCllIOCln characteristics.

Ferralsols and Acrisols are the biggest soil groups in the tropics accounting between them for 37% of tropical soils. They are old soils, often deep, rut intensely weathered and therefore lacking in primary minerals which provide the reserves of nutrients needed for plant life. They are leached of nutrients particularly on sites subject to high rainfall and are acidic which adversely affects the capacity of the topsoil to hold nutrients in a form available for plant use . Nevertheless under undisturbed forest vegetation these soils are capable of carrying a large volume of vegetation on the higher rainfall sites because the nutrient supply available in solution in the topsoil is maintained by the rapid decamposition and mineralization of the litter layer on the soil surface. Even in the drier phases of these soils (mianl:xJ in Africa, cerrado in South ArrErica) where fires are frequent adequate fertility can be maintained if the organic matter content of the soils is not grossly depleted.

Disturbance of these sites, whether for agriculture or by clearing for forest plantations , involves the risk of damaging the soil structure, · particularly if heavy machinery is used . Exposure of the soil and rerroval of organic matter by, for exarrple b..lrning, both damages the soil structure and promotes the loss of nutrients through leaching.

Arenosols and Regosols form a small proportion of tropical soils. They are coarse textured sandy soils having a lCM nutrient content and lCM water retaining capability; as such they are of marginal use to agriculture and are therefore often available for forest plantations .

Lithosols and the lithic (stony and shallCM) phase of other soils are camon in the tropics . These soils are frequently subject to agricultural mismanagement on steep hillsides. Though seldan suitable for large scale camercial forest plantations, forestry may be the Il'OSt appropriate land use to rehabilitate them . ACCUllU.llation of organic matter prcnotes soil formation .

Nitosols, clayey red tropical soils, are Il'Ore fertile than the ferralsols and acrisols and are Il'OStly under agricultural crops, rut in the highlands of East Africa many of the conifer plantations have been established on nitosols unsuited to agriculture by reason of steep slopes or high altitudes and lCM temperatures. These soils are less prone to nutrient deficiencies, rut are liable to erosion if mismanaged.

120

Vertisols are heavy, often bladk, cracking clays which develop wherethere is a long dry season, e.g. in the Deccan (India), Gezira (Sudan),Kanoplains (Kenya). Though tending to be rather low in nitrogen and l1 inexchangeable potassium and available phosphorus, they have a high cationexchange capacity and can be used successfully for agriculture. Because oftheir high clay content, however, they are difficult to work and may beavailable for establishing forestry plantations . Organic matter content tendsto be law.

Catbisols and Luvisols are relatively young, fertile soils that willmostly be reserved for agriculture.

Soil Nutrients

The sixteen chemical elements known to be essential forplant growth arecommonly considered in four categories (Young 1976)

Elements Oxygen, Hydrogen and Carbon supplied from air and water and notnormally considered as nutrients.

Available formPrimary nutrients Nitrogen N NE-14+ & NO3-

Phosphorus P raPotassium K

Secondary nutrients Calcium Ca 03.2+

Magnesium Mg Mg2+Sulphur S so 2-

4

Trace elements Iron Fe Fe Fe3+Boron B Various anionsZinc Zn ZeCopper Cu Cu2+

Manganese Mn MeMolybdenum Mo MOO42-Chlorine Cl Cl-

Source: Young (1976)

Nitrogen is the nutrient most frequently deficient in the tropics. Mbstsoil nitrogen is derived from the mineralization of organic matter. In theorganic form it is not available to plants and must be converted by fungi andbacteria to the mineral form in a 3-stage process; decomposition to ammonia(NH3), conversion of the ammonium cation (NH4) by nitrifying bacteria firstto nitrite (NO2-) then to nitrate (NO3) in which form it is mostly taken upby plants. In this form it is highly soluble and susceptible to leaching andtherefore a continuing supply is essential; the benefits of large doses ofartificial N fertilizer are mostly lost by leaching.

Nitrogen is introduced into the nutrient cycle by the working ofnitrogen fixing bacteria which are either free living Azotobacter (rare in thetropics)or sytbiotic Rhizobium on the roots of sane legumes and non-symbioticbacteria on a range of genera. Fixed ammonia in the subsoil can make somecontribution to the nitrogen economy and it has been estimated rainfall cancontribute up to 5 kg/ha/year (Ewell 1986)

Phosphorus is required by plants and is present in the soil in muchmailer quantities than nitrogen. Mbst of the P in the soil is held in a formunavailable to plants but is converted to the available form (the phosphate

120

Vertisols are heavy, often black, cracking clays which develop where there is a long dry season, e . g . in the Deccan (India), Gezira (Sudan), Kanoplains (Kenya). Though tending to be rather low in nitrogen and low in exchangeable potassium and available phosphorus, they have a high cation exchange capacity and can be used successfully for agriculture. Because of their high clay content, however, they are difficult to work and may be available for establishing forestry plantations. Organic matter content tends to be low.

Cambisols and Luvisols are relatively young, fertile soils that will mostly be reserved for agriculture.

Soil Nutrients

The sixteen chemical elements known to be essential for plant growth are CCIlIlIOrily considered in four categories (Young 1976)

Elements Oxygen, Hydrogen and Carbon supplied fran air and water and not normally considered as nutrients.

Available form Nitrogen N NH+&NO -

4 3 Phosphorus P ~4 Potassium K

Primary nutrients

Secondary nutrients Calcium Ca Ca2+ Magnesium Mg Mg'+ Sulphur S SO 2-

4

Trace elements Iron Fe Fe2+ Fe" Boron B Various anions Zinc Zn Zn2+ Copper eu eu2+ Manganese Mn Mn2+ Mol ytxienum Mo MoO 2-

Chlorine Cl cr 4

Source: Young (1976)

Nitrogen is the nutrient most frequently deficient in the tropiCS . Most soil nitrogen is derived fran the mineralization of organic matter. In the organic form it is not available to plants and must be converted by fungi and bacteria to the mineral form in a 3-stage process; deccmposition to ammonia (~), conversion of the ammonium cation (NH: ) by nitrifying bacteria first to nitrite (N0

2-) then to nitrate (N0

3- ) in which form it is mostly taken up

by plants. In this form it is highly soluble and susceptible to leaching and therefore a continuing supply is essential; the benefits of large doses of artificial N fertilizer are mostly lost by leaching.

Nitrogen is introduced into the nutrient cycle by the working of nitrogen fixing bacteria which are either free living Azotobacter (rare in the tropics) or symbiotic Rhizobium on the roots of sane legumes and non-symbiotic bacteria on a range of genera. Fixed ammonia in the subsoil can make sane contrib.ltion to the nitrogen econany and it has been estimated rainfall can contrib.lte up to 5 kgfha/year (Ewell 1986)

Phosphorus is required by plants and is present in the soil in much smaller quantities than nitrogen. Most of the P in the soil is held in a form unavailable to plants but is converted to the available form (the phosphate

121

anion) at a slaw rate. The rate at which P changes from the unavailable tothe available form is much slower than the rate at which healthy plantationsneed to take up the nutrient, therefore the recycling of P in the organicmatter is anessential contribution to the supply of this nutrient. A problemin many soils, especially acid soils, is the tendency for P to become fixedto clay particles. The rate of release is extremely slow and, though this isan advantage in that the P is available over a long period, it is unavailableat times of rapid uptake by a growing crop. But organic P is less readilyfixed than inorganic P and for this reason, among others, it is important tomaintain the organic content of the soil.

Potassium is present in the soil in larger quantities than P and is lessfrequently deficient. It is taken up by plants as the cation, is easilyleached and can be deficient in rainforest and sandy savanna soils.

Calcium and Magnesium are taken up as cations and therefore can bedeficient on strongly leached soils.

Sulphur is taken up as the anion and can be lost by leaching and byvolatilization during burning. It may be deficient in soils low in organicmatter.

Organic matter has a profound effect on the availability and presenceof nutrients in the topsoil solution. It also affects the structure andmoisture retaining capacity of soils. There is a complex interactioninvolving not only these nutrients (P deficiency inhibits N uptake etc; Caexcess can cause chlorosis by inhibiting the uptake of Fe) but also betweenthe organic content of soils, water availability and nutrients.

A Sail Nutrient Flow Model.

In discussing the interaction of crops and soils it is helpful to havea model of nutrient flows. Figure 1, constructed for conditions in the pineplantations at Usutu, Swaziland can be nsed as a general mcdel.

121

anion) at a slCM rate. The rate at which P changes fran the unavailable to the available fODll is much slower than the rate at which healthy plantations need to take up the nutrient, therefore the recycling of P in the organic matter is an essential contrib..Ition to the supply of this nutrient. A problem in many soils, especially acid soils, is the tendency for P to becane fixed to clay particles. The rate of release is extremely SlCM and, though this is an advantage in that the P is available over a long period, it is unavailable at times of rapid uptake by a grCMing crop. But organic P is less readily fixed than inorganic P and for this reason, arrong others, it is important to maintain the organic content of the soil.

Potassilnn is present in the soil in larger quantities than P and is less frequently deficient. It is taken up by plants as the cation, is easily leached and can be deficient in rainforest and sandy savanna soils.

Calcilnn and Magnesilnn are taken up as cations and therefore can be deficient on strongly leached soils.

Sulphur is taken up as the anion and can be lost by leaching and by volatilization during I::rn:ning. It may be deficient in soils lCM in organic matter.

OrganiC matter has a profound effect on the availability and presence of nutrients in the topsoil solution. It also affects the structure and rroisture retaining capacity of soils . There is a carplex interaction involving not only these nutrients (P deficiency inhibits N uptake etc; Ca excess can cause chlorosis by inhibiting the uptake of Fe) rut also between the organic Content of soils, water availability and nutrients.

A Soil Nutrient Flow It:)de1.

In discussing the interaction of crops and soils it is helpful to have a rrodel of nutrient flCMS. Figure 1, constructed for conditions in the pine plantatiOns at usutu, swaziland can be used as a general rrode!.

Figure 1 Nutrient Flaw Mbdel, Usutu, Swaziland.

Subsoilreadilyavailable

1Subsoilslowlyavailable

Harvest loss

A

Source: Morris (1986)

The forester is primarily interested in the biomass component (andusually specifically in the tree stem fraction of the biomass), but for agiven regime of temperature, rainfall and competition, the growth of thebiomass is dependent on the nutrient supply from the topsoil. At anyone timethe quantity of nutrients held in solution is not large in cornparison with thetotal soil nutrient reserves and the quantity of P, in particular, may besmall in comparison to the amount held in the living and dead biomass.

Table 1 Nutrients in the topsoil

available N&P and exchangeable K, Ca & MgN P K Ca

(Kg/ha)Usutu, Swaziland - pine

Source: Morris (1986)

122

Atmosphere

(burning)

N2 fixation

In top 1 m 1st rotation 3170 5 828 288 4562nd rotation 2789 7 842 279 342

Biomass 17 years 551 73 383 238 88

Litter 2nd rotation 2122 113 130 308 146

(litter)FOREST FLOOR

Stream TOPSOIL --> Topsoil >-

flow HICNASS readily availreserves

- Reserve *-----

Subsoil < Rain &TOPSOIL SOLUTIONSoln Filtering

122

Figure 1 Nutrient Flow Model, Usutu, SWaziland.

HaIvest loss Atrrosphere N2 fixation

(ru!ing) /

----~I=~~~I~--------~ ~i~ B~::r 1 1 rea~~!~il :- ::~! <E(;---> i ~ reserves

Subsoil """':+1----\-... I 'IDPSOIL SOLurION I { I Rain & Soln· ~ . . Filtering

Jubslil L -- -- -- -- -- -- -- -- --~ readily available

Liil slowly available

Source: M:l=is (1986)

The forester is primarily interested in the bianass ca!1pOnent (and usually specifically in the tree stern fraction of the bianass), rut for a given regine of temperature, rainfall and canpetition, the growth of the bianass is dependent on the nutrient supply fran the topsoil. At anyone tine the quantity of nutrients held in solution is not large in carparison with the total soil nutrient reserves and the quantity of P, in particular, may be small in carparison to the amount held in the living and dead bianass.

Table 1 Nutrients in the topsoil

available N&P and exchangeable K, Ca & Mg N P K Ca Mg

--------------- (Kg/ha) -------------­usutu, SWaziland - pine

In top 1 m 1st rotation 3170 2nd rotation 2789

Bianass 17 years 551

Litter 2nd rotation 2122

Source: M:l=is (1986)

5 7

73

113

828 842

383

130

288 279

238

308

456 342

88

146

In comparison to the nutrients held in the coMbined biomass and litterthe quantities of N and Ca available in the soil would appear to be adequate;the proportion of K and mg depends on the site and species bit the quantityof available P is very amall. These quantities and proportions will varybetween sites and between species, but it is to be inferred that the supplyof some nutrients in solution, notably P, can easily become limitingespeciallyat times of maximumgrowth in the developmentphase of plantations.The maintenance of available soil nutrients in the topsoil is critical tohealthy growth of plantations.

Inputs of nutrients arise from

Rainfall and the filtering effect of foliage. In Usutu this effect wasconsidered to be small, but a generalized figure for the tropics of 5-18 kg/ha/yr N and <1 kg/ha/yr P has been calculated (Ewel 1986).

Weathering of primary minerals and movement fram subsoil to topsoil.The quantities involved are hard to estimate and must vary with theavailability of primary minerals in the subsoil, but the rate ofreplacement will always he slaw. It is doubtful whether this source ofnutrients is adequate to replace the losses involved in short rotationforest plantations on highly weathered soils.

Nitrogen fixation. This is covered in more detail in a later sectionof this Appendix. On sane tropical sites as much as 58 kg/ha/yr N hasbeen recorded as being fixed. This process can make a majorcontribution to nitrogen availability.

Losses from the system occur through

Removal of logs at harvesting. This can be quite high, but can bereduced by leaving branches, twigs, bark and leaves in the plantation.

123

Nigeria - Gtzlelina artorea

In top 1 m 1215 2 12 347 57

Biomass 14.5 yrs 157 12 337 66 93

Litter 6 1 3 5 5

Source: Chijioke (1980)Nigeria - GMelina artorea

Soil Reserves 1725 54 - 3491 1508

Biomass 10 yrs 960 371 - 2425 614

Litter 30 1 - 48 11

Source: Nwoboshi (1983)

123

Nigeria - Gaelina arborea

In top 1 In 1215 2 12 347 57

Bianass 14 . 5 yrs 157 12 337 66 93

Litter 6 1 3 5 5

Source : Chijioke (1980) Nigeria - Gaelina arborea

Soil Reserves 1725 54 3491 1508

Bianass 10 yrs 960 371 2425 614

Litter 30 1 48 11

Source: Nworoshi (1983)

In carqJarison to the nutrients held in the canbined bianass and litter the quantities of Nand Ca available in the soil would appear to be adequate; the proportion of K and Mg depends on the site and species but the quantity of available P is very small . These quantities and proportions will vary between sites and between species, but it is to be inferred that the supply of sene nutrients in solution, notably P, can easily becare limiting especially at times of rnaxirnurn grCMth in the developnent phase of plantations . The maintenance of available soil nutrients in the topsoil is critical to healthy grCMth of plantations.

Inputs of nutrients arise fram

Rainfall and the filtering effect of foliage. In Usutu this effect was considered to be small, but a generalized figure for the tropics of 5-18 kg/ha/yr N and <1 kg/ha/yr P has been calculated (Ewel 1986).

Weathering of primary minerals and IOC>vem=nt fram subsoil to topsoil. The quantities involved are hard to estimate and must vary with the availability of primary minerals in the subsoil, but the rate of replacem=nt will always be slow. It is doubtful whether this source of nutrients is adequate to replace the losses involved in short rotation forest plantations on highly weathered soils.

Nitrogen fixation . This is covered in IOC>re detail in a later section of this Appendix. On sene tropical sites as much as 58 kg/ha/yr N has been recorded as being fixed . This process can make a major contribution to nitrogen availability.

Losses fram the system oc= through

Rerroval of logs at harvesting . This can be quite high, but can be reduced by leaving branches, twigs, bark and leaves in the plantation.

Table 2 Nutrients lost at harvesting

Sources: (1) Mbrris (1986); (2) Chijioke

These figures show that quantitieslocality, bit it can be appreciated thatnutrients are involved.

Over a long rotation it is possible that much of the nutrients lostin harvesting can be replaced by nitrogen fixation and by weathering ofparent soil, bit a succession of short rotations will drain the nutrients.Phosphorus is accumulated in higher concentrations in the stems of youngpines, therefore short rotations are particularly likely to drain the Psupply.

Burning slash. This can occur at the time of initial clearing and ateach harvest. The quantities involved have been calculated at Usutu.The burning of slash provides an initial boost of some nutrients (P,K, Ca, Mg) in the form of ash, but N and S are volatilized and lost.Mbst of the nutrients released from the ash are lost through leachingbefore they can he utilized by young plants.

Table 3 Nutrients lost in burning - Usutu

Pinus patula 17 yrs

Source: Mbrris (1986)

124

Kg/haN

266 19 11

(1980); (3) NWoboshi (1983)

can vary with species andsignificant quantities of

Ca mg16 15

Leaching. Losses due to leaching under forest cover were consideredto he small in Usutu (Mbrris 1986), but they can be significant onsandy soils, and in high rainfall particularly during the clearingphase. The maintenance of vegetative cover including that arisingfrom the re-invasion of cleared sites by indigenous vegetation ishelpful in controlling leaching.

Run off can involve the loss not only of large volumes of soil, butalso of the available nutrients in the topsoil. In Trinidad this canamount to 153 tonnes/ha in a year which is equivalent to 1 cm oftopsoil (Bell 1973). In Usutu, however, loss of nutrients by erosionand run off was not considered to be serious.(Mbrris 1986)

Nutrient sinks. The nutrient cycle

-> soil solution -> Biomass -> Litter -> Soil solution

is of great importance. Given the generally slaw rate of replacement ofnutrients into the ecosystem, the potential for large losses from logging andclearing using fire and the varying rate of demand, depending on the season

Usutu pine 17 (1) 257 43 159 123 37

Nigeria Gmelina 6 (2) 182 38 136 108 51

Gmelina 14 (2) 138 11 169 155 52

Brazil pine 6 (2) 99 21 31 25 17

Nigeria Gmelina 10 (3) 754 282 2174 528

Yrs. N P K Ca mg(Kg/ha)

124

Table 2 Nutrients lost at harvesting

Yrs. N P K Ca Mg (Kg/ha)

Usutu pine 17 (1) 257 43 159 123 37 Nigeria Qrelina 6 (2) 182 38 136 108 51

Qrelina 14 (2) 138 11 169 155 52 Brazil pine 6 (2) 99 21 31 25 17 Nigeria Qrelina 10 (3) 754 282 2174 528

Sources: (1) Morris (1986); (2) Chijioke (1980); (3) Nwoboshi (1983)

These figures show that quantities can vary with species and locality, but it can be appreciated that significant quantities of nutrients are involved.

Over a long rotation it is possible that IIUlch of the nutrients lost in harvesting can be replaoed by nitrogen fixation and by weathering of parent soil, but a succession of short rotations will drain the nutrients. Phosphorus is accumulated in higher concentrations in the stems of young pines, therefore short rotations are particularly likely to drain the P supply.

Burning slash. This can oc= at the time of initial clearing and at each harvest. The quantities involved have been calculated at Usutu. The burning of slash provides an initial boost of sane nutrients (P, K, ca, Mg) in the form of ash, but N and S are volatilized and lost. Most of the nutrients released fram the ash are lost through leaching before they can be utilized by young plants.

Table 3 Nutrients lost in burning - Usutu

Pinus patula 17 yrs

Source: Morris (1986)

N 266

Kg/ha P K

19 11 ca 16

Mg 15

Leaching. Losses due to leaching under forest cover were considered to be srrall in Usutu (Morris 1986), but they can be significant on sandy soils, and in high rainfall particularly during the clearing phase. The maintenance of vegetative cover including that arising fram the re-invasion of cleared sites by indigenous vegetation is helpful in controlling leaching.

Run off can involve the loss not only of large volumes of soil, but also of the available nutrients in the topsoil. In Trinidad this can arrount to 153 tonnes/ha in a year which is equivalent to 1 am of topsoil (Bell 1973). In Usutu, however, loss of nutrients by erosion and run off was not considered to be serious. (Morris 1986)

Nutrient sinks. The nutrient cycle

-) Soil solution -) Biomass -) Litter -) Soil solution

is of great importance. Given the generally slow rate of replacement of nutrients into the ecosystem, the potential for large losses fram logging and clearing using fire and the varying rate of demand, depending on the season

Earthworms in temperate zones are probably the most intensivelyresearched of the soil fauna. Earthworms play an important role infragmenting leaf litter and incorporating it into the topsoil; the number andweight of earthworms in a stand of spruce in England has been increased by theadmixture of alder into the stand, and to an even greater extent by addingpine; the mineralization of N and P was also increased (Brown and Harrison1983). Earthworms are less common in the tropics and their role has beentaken over to a large extent by termites, which not only fragment the litterbut also mineralize the nutrients in the litter. Whereas earthworms cause avertical mixing of soils, termites create a lateral concentration of nutrientsinto termitaria and may as a result deplete the forest floor of organic matter(Young 1976; Trapnell in Chaffey 1978) . Other microfauna - millipedes, mites,beetles - generally fragment the litter which renders it into a form bettersuited to decomposition by microf lora. The activity of microfauna is stronglyinfluenced by leaf nutrients and chemicals such as phenols. The inclusioninto a pure stand of species with leaves favoured by microfauna will promotetheir activity, leading to faster litter breakdown and the more rapidincorporation of organic matter into the soil and thus the faster recyclingof nutrients. In Costa Rica in a plot which simulated a species richsuccessional mixture, 50% by weight of Cordia alliodora leaf litter (and 50%of elements other than nitrogen and sulphur) had decomposed within six weeks;in a pure plantation after fifteen weeks only 22% by weight and less than 50%of nutrients (except phosphorus and potassium) had decornposed (Babbar and Ewel1989).

Microf lora.

125

and the stage of development of the plantation, the buffering function oforganic matter in the topsoil is highly significant. If the nutrients areheld in the litter and become unavailable to the topsoil solution, thennutrient deficiencies will occur. In Usutu it was estimated that the weightof nutrients in the forest floor litter in a 17 year old plantation at 1150m altitude was N - 557, P - 30, K - 34, Ca - 81, Mg - 38 kg/ha, but that at1450mthese values were approximately doubled. The rate of litter productionwas similar at both altitudes and was roughly equivalent to the rate of litterbuildup at the higher altitude, indicating that there decomposition was veryslaw.

The role of biological factors.

Microfauna activity.

Bacteria are most beneficial in decomposing organic matter and areessential in the nitrogen cycle; fungi also have an effect. Antagonisms occurbetween microf lora and a change in the forest floor condition may shift themicrobiological equilibrium to favour organisms antagonistic to N fixingbacteria (Florence 1967). The conversion of short leaf pine/hardwood standsin south east USA to pure pine stands has lowered the pH which in turn mayhave inhibited the activity of bacteria and actinomycetes antagonistic toIhytophthora cinamoni, which ni is a problem in these stands. Fbmes annosusalso occurs and it is possible that it is favoured by the lower pH of pinelitter (Florence 1967). The symbiotic role of mycorrhizae in promoting theuptake of nutrients is well known; SUillus variagatus which occurs on Rimssilvestris but not on spruce can degrade protein very effectively leaving upto 87% in solution in the soil where it can be taken up by the spruce; thismay account for the enhanced growth of spruce when pine is introduced into thestand (Ryan and Alexander 1990). In Usutu the foLm and number of themycorrhizae on P.patula changed in second rotation crops which were in check;

125

and the stage of development of the plantation, the buffering function of organic matter in the topsoil is highly significant. If the nutrients are held in the litter and becane unavailable to the topsoil solution, then nutrient deficiencies will occur. In Usutu it was estimated that the weight of nutrients in the forest floor litter in a 17 year old plantation at 1150 m altitude was N - 557, P - 30, K - 34, Ca - 81, Mg - 38 kg/ha, but that at 1450 m these values were approximately doubled. The rate of litter production was similar at roth altitudes and was roughly equivalent to the rate of litter build up at the higher altitude, indicating that there decanposition was very slow.

The role of biological. factors.

Microfauna activity.

Earthwonns in terrperate zones are probably the most intensively researched of the soil fauna. Earthwonns play an :important role in fragmenting leaf litter and incorporating it into the topsoil; the number and weight of earthwonns in a stand of spruce in England has been increased by the admixture of alder into the stand, and to an even greater extent by adding pine; the mineralization of N and P was also increased (Brown and Harrison 1983) . Earthwonns are less ccmron in the tropics and their role has been taken over to a large extent by tennites, which not only fragment the litter but also mineralize the nutrients in the litter . Whereas earthwonns cause a vertical mixing of soils, tennites create a lateral concentration of nutrients into tennitaria and may as a result deplete the forest floor of organiC matter (Young 1976; . Trapnell in Chaffey 1978). Other microfauna - millipedes, mites, beetles - generally fragment the litter which renders it into a form better suited to decanposition by microflora. The activity of microfauna is strongly influenced by leaf nutrients and chemicals such as phenols . The inclusion into a pure stand of species with leaves favoured by microfauna will prarote their activity, leading to faster litter breakdown and the more rapid incorporation of organic matter into the soil and thus the faster recycling of nutrients. In Costa Rica in a plot which simulated a species rich successional mixture, 50% by weight of Cordia alliodora leaf litter (and 50% of elements other than nitrogen and sulphur) had decanposed within six weeks; in a pure plantation after fifteen weeks only 22% by weight and less than 50% of nutrients (except phosphorus and potassium) had decanposed (Babbar and Ewel 1989) .

Microflora .

Bacteria are most beneficial in decanposing organiC matter and are essential in the nitrogen cycle; fungi also have an effect. Antagonisms occur between microflora and a change in the forest floor condition may shift the microbiological equilibrium to favour organisms antagonistic to N fixing bacteria (Florence 1967). The conversion of short leaf pinejhardwocd stands in south east USA to pure pine stands has lowered the pH which in turn may have inhibited the activity of bacteria and actinamycetes antagonistic to Phytophthora cinaroclni, which now is a problem in these stands. Fcrnes annosus also occurs and it is possible that it is favoured by the lower pH of pine litter (Florence 1967) . The symbiotic role of mycorrhizae in praroting the uptake of nutrients is well known; Suillus variagatus which occurs on Pinus silvestris but not on spruce can degrade protein very effectively leaving up to 87% in solution in the soil where it can be taken up by the spruce; this may account for the enhanced grCMth of spruce when pine is introduced into the stand (Ryan and Alexander 1990). In Usutu the form and number of the mycorrhizae on P.patula changed in second rotation crops which were in check;

126

this change in the mycorrhizae and the growth check was attributed to theaccumulation of litter, which may have caused both a reduction of availablenutrients and an increase of toxins (Robinson 1973).

Nitrogen-fixation.

The effect of nitrogen-fixation has buen well documented in NorthAmerica (Binkley 1983,1984,1990; Binkley and Greene 1983; Hansen and Dawson1982; Friederich and Dawson 1984; Schlesinger and Williams 1984). The speciesinvolved have generally been alder (Alnusrubra, A.sinC2ata and A.glutir2asa)andautumn olive (Elaeagnus umbellata) acting on Douglas fir (PseudotsugaEenziesii), walnut (juglans nigra) and poplars. Beneficial effects haveoccurred when nitrogen has been in short supply, but where there has been anadequate supply of other nutrients to keep the nitrogen fixing species growinghealthily. Legumes require moisture and when under stress will not fixnitrogen (Sprent 1985), though it has been suggested that alder and Robiniapseudoacacia may release nitrogen in response to competition-induced stress(Dawson et al. 1983; Friederich and Dawson 1984). A close association isneeded of the nitrogen-fixer with the benefiting species and growth has beenshown to be correlated with quantities of N fixed in the topsoil (Paschke etal. 1989). But it has been suggested (Ewel 1986) that nitrogen-fixing speciesmostly use up the nitrogen they manufacture and only release it through theirlitter, and it has certainly been observed that leaf litter from A. glutinosaand E.umbellata used as a mulch enhanced the growth of poplars on prairiesoils (Carlson and Dawson 1984). The evidence on this point is confusing.There is also evidence that Picea sitchensis did not respond to increasednitrogen (585 kg/ha) made available by A.glutinosa (Malcolm et al. 1985).

On nitrogen-rich soils the presence of nitrogen-fixing plants can bedeleterious, because they compete for light, moisture and other nutrients.In Australia the introduction of acacias into stands of P.radiata andRelliottii on sandy podzols resulted in a depression in growth as a resultof increased competition, even though the soils were low in N (TUrvey et al.1984). On the other hand Daviesia mimosoides growing under natural alcalyptusdives and E.divesicolor on red kraznozem soils on exposed ridges wasconsideredto have had a beneficial effect on grawth despite the fact that theamimosoides had only 50% nodulation and was fixing only 4 to 7 kg of N perha per year (McColl and Edmonds 1983).

In Hawaii there is a well documented example of the benefit ofintroducing nitrogen-fixing species (Albizia falcataria and Arciamelanoxylon) into Eucalyptus saligna plantations on an abandoned sugar estate(DeBell et al. 1985, 1987, 1989). On a site receiving 5000 mm rain nitrogenwas increased in the topsoil and there was a significant and marked growth inthe eucalyptus, but on a dry site there was no benefit and on one site theAlbizia died. In the Niligiris in India there is a less reliable account ofAcacia menziesii having a beneficial effect when grown under Ebralyptusglobulus (Samraj et al. 1977). The introduction of leguminous trees,Erythrina, Gliricidia, Acacia auriculifonnis, A. orassiocazpa and A.polystachyainto eucalyptus plantations near Chittagong, Bangladesh has been proposed(Davidson 1986), but there is no record of any effects.

Nitrogen fixation is often associated with legumes, although nodulationis only sporadic in the Caesalpinioideaea (Sprent 1985), but in fact non-syMbiotic fixation of nitrogen (alder type nodules) has buen recorded asoccurringon nearly 200 species in 20 genera other than legumes; this included24 species of Casuarina which are probably the most significant species forthe tropics (Bond 1983). The quantities of nitrogen fixed vary considerably.

126

this change in the myco=hizae and the grcMth check was attrib..Jted to the accumulation of litter, which may have caused roth a reduction of available nutrients and an increase of toxins (Robinson 1973).

Nitrogen-fixation.

The effect of nitrogen-fixation has been well documented in North America (Binkley 1983,1984,1990; Binkley and Greene 1983; Hansen and Dawson 1982; Friederich and Dawson 1984; Schlesinger and Williams 1984). The species involved have generally been alder (Alnus rubra, A.sinilata and A.glutinasa)and autumn olive (Elaeagnus umbellata) acting on Douglas fir (Pseudotsuga IrellZiesii), walnut (Juglans nigra) and poplars. Beneficial effects have occu=ed when nitrogen has been in short supply, but where there has been an adequate supply of other nutrients to keep the nitrogen fixing species gr=ing healthily. Legumes require rroisture and when under stress will not fix nitrogen (Sprent 1985), though it has been suggested that alder and Robinia pseudoacacia may release nitrogen in response to canpetition-induced stress (Dawson et al. 1983; Friederich and Dawson 1984). A close association is needed of the nitrogen-fixer with the benefiting species and grCMth has been ShCMn to be correlated with quantities of N fixed in the topsoil (Paschke et al. 1989). But it has been suggested (Ewel 1986) that nitrogen-fixing species rrostly use up the nitrogen they manufacture and only release it through their litter, and it has certainly been observed that leaf litter fran A.glutinosa and E. umbellata used as a mulch enhanced the grCMth of poplars on prairie soils (carlson and Dawson 1984) . The evidence on this point is confusing. There is also evidence that Pioea sitcnensis did not respond to increased nitrogen (585 kg/ha) made available by A . glutinosa (Malcolm et al. 1985).

On nitrogen-rich soils the presence of nitrogen-fixing plants can be deleterious, because they canpete for light, rroisture and other nutrients . In Australia the introduction of acacias into stands of P .radiata and P.elliottii on sandy podzols resulted in a depression in gr=th as a result of increased canpetition, even though the soils were 1= in N (Turvey et al. 1984) . On the other hand Daviesia llliIocJsoides gr=ing under natural Eucalyptus dives and E.divesicolor on red kraznozem soils on eJqXlsed ridges was considered to have had a beneficial effect on grCMth despite the fact that the D.llliIocJsoides had only 50% nodulation and was fixing only 4 to 7 kg of N per ha per year (McColl and Edrronds 1983).

In Hawaii there is a well documented example of the benefit of introducing nitrogen-fixing species (Albizia falcataria and Acacia rrelanoxylon) into Eucalyptus saligna plantatiOns on an abandoned sugar estate (DeBell et al. 1985, 1987, 1989). On a site r eceiving 5000 nm rain nitrogen was increased in the topsoil and there was a significant and marked grCMth in the eucalyptus, but on a dry site there was no benefit and on one site the Albizia died . In the N;Lligiris in India there is a less reliable account of Acacia IrellZiesii having a beneficial effect when grCMn under Eucalyptus globulus (Sarnraj et al. 1977) . The introduction of leguminous trees, Erythrina, Gliricidia, Acacia auriculiformis, A. crassiocarpa and A. polystachya into eucalyptus plantations near Chittagong, Bangladesh has been proposed (Davidson 1986), but there is no record of any effects.

Nitrogen fixation is often associated with legumes, although nodulation is only sporadic in the caesalpinioideaea (Sprent 1985), but in fact non­symbiotic fixation of nitrogen (alder type nodules) has been recorded as occu=ing on nearly 200 species in 20 genera other than legumes; this included 24 species of Gasuarina which are probably the rrost significant species for the tropics (Bond 1983). The quantities of nitrogen fixed vary considerably.

127

Table 4 Amount of Nitrogen Fixed by Some Species

kg/ha/yrCasuarina eguisetifOlia in N.Africa 58 (Kormanik 1979)Elaeagnus umbellata 178 (Paschke et al. 1989)Acacia holosericea 6.4 (McColl et al. 1983)A,pulchella var glaberrima 2.2A.mearnsii .8

A.verniciflua 32 (TUrvey et al, 1984)

A_Uelopathy

The inhibition of the growth of one species by exudates from anotherspecies is comparatively rare, but juglone from walnuts has noted as havingthis effect (von Althen 1968) . In Indonesia there is an account of severalspecies including Leucaena leucocephala and SWietenia Eacrqphylla failing tothrive under Melaleuca leucadendron and allelopathy was considered a possiblecause. In Australia the inhibition of the germination of seedlings ofGrevillea robiista under old trees of the same species has been noted (Florenceand LaMb 1974)

Nutrient deficiencies

Depending on the soil type, climate, method of establishing the treecrop and the nature of the crop any of the nutrients could become deficient.It is likely that N, P, K and possibly Ca are most likely to be limiting inthe tropics (Lundgren 1980). The nutrients available in solution in the soilmaybe small in relation to the requirements of the biomass at any one time.N and P, in particular, are only slowly available from soil reserves,therefore the recycling of litter is an important source of these twonutrients. The requirements of the biomass and the drain on the nutrients insolution vary with the stage of development of the crop.

Taking Usutu pine plantations as an example:

At the start of each rotation the exposure of the litter following'harvesting results in rapid decomposition of organic matter and a flushof nutrients, but the rooting volume of the seedlings is small and theymay suffer from ladk of nutrients, particularly P and K; at the sametime available nutrients are being leached away.Up to the age of seven years, nutrient requirements to maintain biomassproduction increase rapidly and K may remain in short supply.Fron seven to twelve years of age, biomass production requirements arestill high but litter starts to build up and, if decomposition is slaw,nutrient cycling may be inefficient thus putting P under pressure.From twelve years of age onwards biomass requirements remain fairlyconstant but litter build up continues; N and P may become deficientand at higher altitudes possibly Ca also.

A mdxture of species may he useful (but not necessarily at Usutu):

at time of establishment another species used as an in-filler can makeuse of excess nutrients and help recycle them; this effect can beachieved by allowing weed growth or through the use of ground cover.in helping to decompose the needle mat under the pines from seven yearsonwards; a more open stand and the encouragement of a naturalunderstorey might achieve this.

127

Table 4 Alrount of Nitrogen Fixed by Sane Species

Casuarina equisetifolia in N.Africa Elaeagnus umbellata Acacia holosericea A. pulchella var glaberrima A.mearnsii A . veLTJiciflua

Allel.opathy

kg/ha/yr 58 (Kormanik 1979)

178 (Paschke et al . 1989) 6 . 4 (McColl et al. 1983) 2.2

.8 32 (Turvey et aI, 1984)

The inhibition of the grONth of one species by exudates fran another species is carparatively rare, but juglone fran walnuts has noted as having this effect (von Althen 1968). In Indonesia there is an account of several species including Leucaena leucocephala and SWietenia macrophylla failing to thrive under M21aleuca leucadendron and allelopathy was considered a possible cause. In Australia the inhibition of the gennination of seedlings of Grevillea robusta under old trees of the same species has been noted (Florence and Lamb 1974)

Nutrient deficiencies

Depending on the soil type, climate, method of establishing the tree crop and the nature of the crop any of the nutrients could becare deficient. It is likely thci.t N, P, K and possibly ca are rrost likely to be limiting in the tropics (Lundgren 1980) . The nutrients available in solution in the soil maybe small in relation to the requirements of the biomass at anyone time. N and P, in particular, are only slONly available fran soil reserves, therefore the recycling of litter is an important source of these two nutrients . The requirements of the bianass and the drain on the nutrients in solution vary with the stage of development of the crop.

Taking Usutu pine plantations as an example :

At the start of each rotation the exposure of the litter follONing "harvesting results in rapid decanposition of organic matter and a flush of nutrients, but the rcoting volume of the seedlings is small and they may suffer fran lack of nutrients, particularly P and K; at the same time available nutrients are being leached away. Up to the age of seven years, nutrient requirements to maintain biomass production increase rapidly and K may remain in short supply . Fran seven to twelve years of age, biomass production requirements are still high but litter starts to build up and, if decanposition is slON, nutrient cycling may be inefficient thus putting P under pressure. Fran twelve years of age onwards biomass requirements remain fairly constant but litter build up continues; N and P may becare deficient and at higher altitudes possibly ca also .

A mixture of species may be useful (but not necessarily at Usutu) :

at time of establishment another species used as an in-filler can make use of excess nutrients and help recycle them; this effect can be achieved by allONing weed grONth or through the use of ground cover . in helping to decanpose the needle mat under the pines fran seven years onwards; a rrore open stand and the encouragement of a natural understorey might achieve this .

128

A comparison has been made between indigenous forests and Gre1inaplantations in Nigeria and between indigenous forests and both pine andGMelina plantations in South America (Chijioke 1980). He was unable todemonstrate that monospecific plantations lead to a more rapid depletion ofsoil nutrient reserves than would mixtures having the same biomass production,the same rotation length and the same proportion of the crop removed inharvest. Despite the large quantities of N immobilized by anelina and pinesit was present in more than optimum levels in the soil and harvestingrepresented no threat to the future N status. K which was immobilized ingreater quantities, and possibly P, may become limiting.

In Kenya measurements were made to compare soils under second and thirdrotation conifer crops and under indigenous forest (Robinson 1967; Robinsonet al. 1966). The results were not conclusive, but only a slight decrease innutrient availability could be detected in cypress and pine plantations andthere were indications that the drop in nutrient availability occurred duringthe establishment phase of each rotation as a result of cultivation under thetaungya system, while fertility increased in the period the trees were on theground. On one site bulk density decreased and pH increased under theplantations, indicating a general improvement in soil conditions.

128

A canparison has been made between indigenous forests and Grlelina plantations in Nigeria and between indigenous forests and both pine and Grlelina plantations in South America (Chijioke 1980). He was unable to demonstrate that monospecific plantations lead to a more rapid depletion of soil nutrient reserves than would mixtures having the same bianass production, the same rotation length and the same proportion of the crop removed in harvest. Despite the large quantities of N ilrrnobilized by Grlelina and pines it was present in more than optimum levels in the soil and harvesting represented no threat to the future N status. K which was ilrrnobilized in greater quantities, and possibly P, may beCOT¥::! limiting.

In Kenya measurements were made to canpare soils under se=nd and third rotation =nifer crops and under indigenous forest (Robinson 1967; Robinson et al. 1966). The results were not =nclusive, but only a slight decrease in nutrient availability could be detected in cypress and pine plantations and there were indications that the drop in nutrient availability oc=ed during the establishment phase of each rotation as a result of cultivation under the taungya system, while fertility increased in the period the trees were on the ground . On one site bulk density decreased and pH increased under the plantatiOns, indicating a general improvement in soil =nditions.

129

APPENDIX 3

SPECIES MIXTURES

This is a collection of most of the mixtures that were found in theliterature. Where possible sane indication has been given on the success ofthe mixture. Most of the mixtures listed are in fact experimental. Thefollowing mixtures are thought to have been used as general forestry practice.

QueenslandAraucaria cunning-hat-I-di Pinesbut practice discontinued

VietnamEucalyptus tereticornis over Acacia auriculifOrmismore than 10,000 ha thought to have been established, but noinformation available to date on success.

KenyaCypress Grevillea robustaPractice discontinued by mid 1950s

TogoEUcalyptus torelliana ET.tereticornisconsidered a success.

Sri LankaSWietenia Eacrophylla Tectona grandis

Artocarpus integrifoliushighly successful at Sundapola

The use of nurse species to shade mahoganies is standard practice inmany tropical countries. In West Africa the practice has been abandoned infrancophone countries, but is still continued in Nigeria.Indonesia

Teak Leucaena leucocephala used as a nurse toestablish the teak

Nio seriously affected by Betergpsylla cubana

MAIN SPECIES SECONDARY (Nurse) SOURCEAUSTRALIA - Queensland

Araucaria cunninghaudi Pinus elliottii Nielsen 1991planting hoop pine under slash pine resulted in better growth(increased nitrogen uptake).

Rtaeda, P.Icatula

A.bidWillii P.elliottii Nielsen 1991- Victoria

Flindersia brayleyana Araucaria cunninghamiiF.brayleyana able to recover and make a crop when released.

E.sieberi with Acacia longifOliaE.totryoides & E.sideroxylon

beneficial effect on height growth of Eucalyptus

Pinus radiataorPinus elliottii

Smith et al 1989 also

Acacia spp. Turvey et al 1984

129

APPENDIX 3

This is a collection of most of the mixtures that were found in the literature. Where possible sane indication has been given on the success of the mixture . M:Jst of the mixtures listed are in fact experimental . The folloo-ing mixtures are thought to have been used as general forestry practice.

QJeensland AIaucaria cunninghamii Pines rut practice discontinued

Vietnam Eucalyptus teretico=is over Acacia auriculiformis more than 10 , 000 ha thought to have been established, rut no information available to date on success.

Kenya

Togo

cypress Practice discontinued by mid

Eucalyptus torelliana considered a success .

Sri Lanka

Grevillea robusta 1950s

E. teretico=is

SWietenia macrophy lla Tectona grandis Artocarpus integrifolius

highly successful at Sundapola

The use of nurse species to shade rrehoganies is standard practice in many tropical countries. In West Africa the practice has been abandoned in francophone countries, rut is still continued in Nigeria. Indonesia

Teak Leucaena leucocephala used as a nurse to establish the teak

Noo- seriously affected by Heteropsylla cul:Ena

MAIN SPEX:IES SEX:XElARY (Nurse) AIlS',rRALIA - ()leensland

Araucaria cunninghamii Pinus elliottii planting hoop pine under slash pine resulted (increased nitrogen uptake) .

P. taeda, P .patula

Nielsen 1991 in better grOO"th

A . bidwillii P . elliottii Nielsen 1991

Araucaria cunninghamii - Victoria

Flindersia brayleyana F.brayleyana able to recover and make a crop when released .

E.sieberi with Acacia longifolia SDith et al1989 also E.botryoides & E.sideraxylon

beneficial effect on height grOO"th of Eucalyptus

Pinus radiata or Pinus elliottii

Acacia spp. TUrVeyetall984

The effects of naturally regenerated acacias were investigated. Nopositive effects were detected.

BA1GLADES1-1

Calamus spp

EUcalyptus urpphylla

Piptadenia macrocarpaAstronium urundeuvaAbqinia polymorphaCblubrina rufaTabebuia impetiginosa

Dalbergia sissooExperiment established in 1967

EUcalyptus camaldulensisExperiment established in 1980.

BURUNDI

EUcalyptus grandis Acacia el ata

Experiment established in 1987. Poor survival for A. elata.

CAMEROON

130

Leucaena leucocephala Nbraes de Jesus 1989

Garrido & Poggiani 1979

Pinus caribaea v. hondurensis Liquidawbar styraciflua Novais & Poggiani SLeaf heterogeneity appears to increase litter decomposition and nutrientcycling.

BUREUNA FASO

. Treatments have favoured D. sissoo.

Rhaya senegalensisExperiment established

Azadirachta indicaRhaya senegalensisExperiment established in 1983.

in 1986.Dalbergia sissoo

Ealbergia sissoo

Cirrr 1991

Citf 1991

Clkl 1991

CTFr 1991

cTrT 1991

Entandrpphragma cylindricum Pinus elliottii Citi 1991If Aansonia altissima

Experiment established in 1975. In 1977 P. elliottii was replaced by M.altissima. Growth was slow and survival high for E. cylindricum.

Shorea robusta Davidson 1986Pinus oocarpa

Eucalyptus tereticornis C1TU 1991

GMelina arborea Citi 1991

Rhaya senegalensis Eucalyptus camaldulensisExperiment established in 1983. Low survival for Rhaya.

Pinus elliottii Entandrpphragma cylindricumExperiment established in 1975. 90% Finus.

130

The effects of naturally regenerated acacias were investigated. No positive effects were detected.

Calamus spp Shorea roJ:;usta Pinus oocaJ1l'l

Davidson 1986

Eucalyptus urophylla Leucaena leucocephala M:lraes de Jesus 1989

Piptadenia macrocarpa Astronium UIUlJdeuva M?qinia polYIlVLpha Colubrina =fa TabeOOia impetiginosa

Garrido & Poggiani 1979

Pinus caribaea v. hondurensis Liquidamb3r styraciflua Novais & Poggiani • leaf heterogeneity appears to increase litter dec::c:rrposition and nutrient cycling.

Dalbergia sissoo Eucalyptus tereticornis CTFl' 1991 Experiment established in 1967. Treatments have favoured D. sissoo.

Eucalyptus camaldulensis Gnelina arborea Experiment established in 1980.

BURUNDI

Eucalyptus grandis Acacia elata Experiment established in 1987. Poor survival for A . elata.

Khaya senegalensis Dalbergia sissoo Experiment established in 1986.

Azadirachta indica Dalbergia sissoo Khaya senegalensis Experiment established in 1983.

Khaya senegalensis Eucalyptus camaldulensis Experiment established in 1983 . li:M survival for Khaya.

Pinus elliottii Entandrophragma cylindricum Experiment established in 1975. 90% Pinus.

CTFl' 1991

CTFl' 1991

CTFl' 1991

CTFl' 1991

CTFl' 1991

CTFl' 1991

Entandrophragma cylindricum Pinus elliottii CTFl' 1991 /I Mansonia al tissima

Experiment established in 1975. In 1977 P. elliottii was replaced by M. altissirna. GrCMth was sla.v and survival high for E. cylindricum.

CHINA

Elicalyptus exserta

CCINGO

Acacia auriculifOrmis EUcalyptus tereticornisExperiment established in 1984.

Araucaria hunsteinii pini 7S caribaea Clkl 1991Experiment established in 1980. Constant height differences recorded.

Entandrophragma angolense Letestua durissima CLE1 1991Acacia auriculifOrmisExperiment established in 1982 Good condition but poor growth for A.auriculifOrmis.

Tectona grandis Terminalia superbaExperiment established in 1988. Individual mixture.

COTE D'IVOIRE

Aucoumea klaineana Tarrietia utilisRhaya ivorensisTieghemella heckeliiExperiment established in 1964. T. utilis is the nurse crop. T.well. Fast growth for T. heckelii on sands has been noted.

GMelina arborea Acacia auriculifOrmisExperiment established in 1985. Insect attacks have

GMelina artoreaKhaya ivorensisChlorqphora spp.Mansonia altissima

arborea were established in 1961, the others in

Ttiplochiton scleroxylon

The experiments with GMelina1928.

Terminalia ivorensisExperiment established in 1977.

Khaya grandifOliclaEhaya ivorensisKhaya senegalensisExperiments established in 1977senegalensis did poorly.

Aucoumea klaineanaRhaya ivorensisExperiment established in 1965.

Triplochitcn scleroxylcnExperiment established in 1961.

Terminalia ivorensisExperiment established in 1981.

131

with Acacia auriculiformis Barnes 1991

Cedrela odoratafr

ff

. Cedrela is the nurse and

Tarrietia utilis

K.ivorensis is promising; A.klaineana not.

Tectona grandis C1Y1 1991

been severe.

CTE1 1991

crier. 1991

CTFT 1991

utilis grows

Likl 1991

crrr 1991

Llbi 1991

grows fastest. K.

CTFT 1991

Cedrela odorata liki 1991C. odorata suppresses T. ivorensis.

Terminalia superta (Alf 1991The mixture is promising.

131

CHINA

Eucalyptus exserta with Acacia auriculiformis Barnes 1991

Acacia auriculiformis Eucalyptus tereti=mis CTFl' 1991 Exper:irnent established in 1984.

Araucaria hunsteinii Pinus caribaea CTFl' 1991 Exper:irnent established in 1980. Constant height differences recorded .

Letestua durissima CTFl' 1991 Entandrophragma angolense Acacia auriculiformis Exper:irnent established in auriculiformis.

1982. Good condition but poor gro.rr.h for A .

Tectona grandis Terminalia superba CTFl' 1991 Exper:irnent established in 1988 . Individual mixture.

COTE D' IVOIRE

Au=umea klaineana Tarrietia utilis CTFl' 1991 Khaya ivorensis /I

Tieghcmella heckelii /I

Exper:irnent established in 1964. T. utilis is the nurse crop . T. utilis grows well. Fast grCMth for T. heckelii on sands has been noted .

Gnelina arborea Acacia auriculiformis CTFl' 1991 Exper:irnent established in 1985. Insect attacks have been severe.

Triplochi ton scleroxylon /I

/I

/I

Gnelina arborea Khaya ivorensis Chlorophora spp. Mmsonia al tissima

CTFl' 1991

The exper:irnents with 1928 .

Gnelina arborea were established in 1961, the others in

Terminalia ivorensis Cedrela odorata CTFl' 1991 Experiment established in 1977. C. odorata suppresses T. ivorensis.

Khaya grandifoliola Cedrela odorata CTFl' 1991 Khaya ivorensis /I

/I Khaya senegalensis Exper:irnents established in senegalensis did poorly.

1977. Cedrela is the nurse and grows fastest. K.

Au=umea klaineana Tarrietia uti lis CTFl' 1991 /I Khaya ivorensis

Exper:irnent established in 1965 . K. ivorensis is pranising; A.klaineana not.

Triplochiton scleroxylon Tectona grandis CTFl' 1991 Exper:irnent established in 1961 .

Terminalia ivorensis Terminalia superba CTFl' 1991 Exper:irnent established in 1981. The mixture is pranising.

Terminalia ivorensisExperiment establishedpoison girdled forest.of Cedrela.

¡(haya senegalensisExperiment established

Terminalia ivorensisExperiment establishedforest.

Terminalia ivorensisExperiment established1982. 252 T. ivorensis

Cedrela odorataExperiment established in 1976C. odarata was co-dominant.

132

Cedrela odorata (Atli 1991in 1965. Individual mixture with low density under aThe low density has adverse effects on the stem form

Terminalia ivorensis Ciki 1991in 1965. 64 tree/hectare were planted.

Entandrophragma utile cit.'. 1991in 1965. 41 trees/hectare planted in a poison girdled

Terminalia super-La CTFT 1991in 1977. Line mixture. Selectively thinned in 1980 andand 160 T. superta planted per hectare.

Rhaya ivorensis Tarrietia utilisExperiment established in 1963. A promising mixture.

Triplochiton scleroxylon Terminalia superbaExperiment established in 1963.

¡(haya ivorensis Tarrietia utilis¡(haya anthothecaExperiment established in 1981.

Acacia auriculiformis Acacia mangiumExperiment established in 1985.

Acacia auriculiformis Cocos nuciferaAcacia HongiumCasuarina eguisetifoliaExperiment established in 1985. Two lines of each specieslines of C. nucifera. Best growth has been recorded for A.

FIJI

Cedrela odorata

Tectona grandis

Leucaena leucocephala

SWietenia Eacrophylla

GMelina arborea Clkl 1991. Line mixture. After four years

cirr 1991

Lin.' 1991

CTrf 1991

mer 1991

Clkl 1991

separated by twoauriculiformis.

Streets 1962

Streets 1962

Cedrela odorata Terminalia ivorensis Liki 1991Experiment established in 1965. Individual mixture

Triplochiton scleroxylon Rhaya ivorensis LITT 1991Experiment established in 1964. Individual mixture.

Tieghemella spp. Triplochiton scleroxylon CIT1 199111 Khaya ivorensis

Experiment established in 1964. Individual mixture with ¡(haya or Tieghemella.

132

TeIIIZinalia ivorensis Cedrela odorata CTFr 1991 Experiment established in 1965. Individual mixture with law density under a poison girdled forest . The l aw density has adverse effects on the stem form of Cedrela.

Khaya senegalensis TeIIIZinalia ivorensis CTFr 1991 Experiment established in 1965. 64 tree/hectare were planted .

TeIIIZinalia i vorensis Entandrophragma. utile Experiment established in 1965. 41 trees/hectare planted forest .

CTFr 1991 in a poison girdled

TeIIIZinalia ivorensis TeIIIZinalia superba. CTFr 1991 Experiment established in 1977. Line mixture. Selectively thinned in 1980 and 1982. 252 T. ivorensis and 160 T. superba. planted per hectare .

Cedrela odorata TeIIIZinalia ivorensis CTFr 1991 Experiment established in 1965. Individual mixture

Triplochiton scleroxylon Khaya ivorensis CTFr 1991 Experiment established in 1964 . Individual mixture.

Tieghemella spp. Triplochiton scleroxylon CTFr 1991 " Khaya ivorensis

Experiment established in 1964 . Individual mixture with Khaya or Tieghemella .

Cedrela odorata Grlelina arlxJrea CTFr 1991 Experiment established in 1976 . Line mixture. After four years C. odorata was co-daninant.

Khaya ivorensis Tarrietia utilis Experiment established in 1963 . A pranising mixture.

Triplochi ton scleroxy lon TeIIIZinalia superba. Experiment established in 1963.

Khaya i vorensis Khaya anthotheca Experiment established in 1981.

Tarrietia utilis "

CTFr 1991

CTFr 1991

CTFr 1991

Acacia auriculifozmis Acacia mangium CTFr 1991 Experiment established in 1985.

Acacia auriculifozmis Cocos nucifera CTFr 1991 Acacia mangium casuarina equisetifolia Experiment established iri 1985. Two lines of each species separated by two lines of C. nucifera . Best growth has been recorded for A. auriculifozmis.

FIJI

Cedrela odorata Leucaena leucocephala streets 1962

Tectona grandis SWietenia macrvphylla streets 1962

FRENCH GUYANA

Carapa procera GMelina arborea (LEr 1991or Neopoffetia spp.SWietenia macrophyllaorSWieteniamahoganiExperiment established in 1978. 10% Carapa or mixed species notattadked by I*Tiosi.pyl/a. Poor growth for SWietenia.

HAWAII

ucalyptus grandis) (Albizia falcatariaucalyptus saligna) (Acacia melanoxylcn

A.melanoxylon not so successful as A.falcataria

INDIA

Tectona grandis falhergia larifolia Indian Forestff Téphrosia candida Service 1934ff Cajanusff Leucaena glaucaft SWietenia Aacrqphylla

Cedrela toonaIF

"B'amboo species"Iterocarpus marsqpiumArtocarpus hirsuta

Téphrosia is an underwood species that seems ef f icient if introduced in thethird year. Underplanting of S. macrqphylla in 37 year old plantations had notyielded promising results, and the same experience was obtained with Cedrelatoona. D. latifolia shows more promise when sown at the same stake as teakthan when mixed in strips.

Termlnalia rhyriocarpa Lagerstroemia flos-reginae Indian ForestEnded in pure crops of the faster growing T. ayriocarpa. Service 1934

Lagerstroemia flos-reginae Itksua férrea Indian ForestMore promising than the corribination above. AL ferrea, Service 1934a shade bearer is the underwood species.

Daibergia sissoo Eucalyptus spp., Monis nigra Indian ForestAn irrigated plantation in Punjab. Great losses of AL nigra Service 1934due to frost.

Tectona grandis

133

DeBell et al 1985

Arelccanna bambuscides Indian ForestCephalostachyumpergracile Service 1934GMelina arboreaAylia dolabriformisAcacia catechuEalLergia sissoo, Acacia catechuEalLergia latifoliaIterocarpus marsupiumIterocarpus dahibergioidesArtocarpus hiLsutaSWietenia macrqphyllaEambusa Luida

ca.rapa procera or SWietenia macrophylla or SWietenia mahogani

133

Gnelina arborea Neopanetia spp.

CTFT 1991

Experiment established in 1978 . 10% Garapa or SWietenia mixed with species not attacked by Hypsipyla. Poor grCMth for SWietenia.

HilWAII

Eucalyptus grandis) Eucalyptus saligna)

A.rrelanoxylon not

INDIA

Tectona grandis " " " " " " "

(Albizia falcataria DeBell et al 1985 (Acacia rrelanoxylon

so successful as A . falcataria

DalJJergia larifolia Tephrvsia candida Cajanus Leucaena glauca SWietenia macrophylla Cedrela toona "Bamboo species" pterocarpus marsupium

Indian Forest Service 1934

" Artocarpus hirsuta Tephrvsia is an underwood species that seems efficient if introduced in the third year . Underplanting of S. macrophylla in 37 year old plantatiOns had not yielded pranising results, and the same experience was obtained with Cedrela toona. D. latifolia sheM.> more pranise when SCMn at the same stake as teak than when mixed in strips.

Terminalia myriocarpa Lagerstroemia flos-reginae Indian Forest Ended in pure crops of the faster grcMing T. myriocarpa. Service 1934

Lagerstroemia flos-reginae Mesua ferrea Indian Forest Service 1934 MJre pranising than the canbination above. M. ferrea,

a shade bearer is the underwood species.

Dalbergia sissoo An irrigated plantation due to frost .

Tectona grandis " " " " " " " " " " "

Eucalyptus spp., MJrus nigra Indian Forest in Punjab. Great losses of M. nigra Service 1934

Melocanna b3mbusoides Cephalostachyum pergracile Gnelina arborea Xylia dolabriformis Acacia catechu

Indian Forest Service 1934

DalJJergia sissoo, Acacia catechu DalJJergia latifolia pterocarpus marsupium pterocarpus dahlJJergioides Artocarpus hirsuta . SWietenia macrophylla Bambusa tulda

134

Mixtures of AL bambusoides and Teak seem to have been successful fromthe economic point of view in the Chittagong Hill Tract. This may also be truefor mixtures with C. pergracile. For T. grandis and G. artorea there arereports of both species suppressing each other. Fram the insect attack pointof view the mixture is undesirable. X. dolabriformis is usually outgrown bythe teak. Mixtures with A. catechu tend to separate into pure groups. Intimatemixture of T. grandis, A. catechu and D. sissoo has been tried. This has ledto a mixture of T. grancZis and D. sissoo, which is reported to have done well,though there are also reports of the opposite. Mixture with D. latifOlia havenot been successful, mainly due to browsing. Experiences of mixing with P.marsupium are discouraging. There are reports of mixture with A. hirsuta beingsilviculturally successful. From the economic point of view the mixture isregarded as questionable. Reports regarding mixture with P. dahlbergioidesindicate that one species is likely to suppress the other. Mixed crops withS. macrophylla are regarded as failures, S. Eacrophylla being suppressed ongood soils and vice versa. Mixtures with B. tulda have led to suppression ofthe teak.

Banbax malabricurn Acacia catechu Indian ForestThis seems to he a worthwhile mixture from the economic Service 1934point of view.

Dipterocarpus turbina tus GMelina arborea Indian FbrestG. artorea was to serve as a nurse crop. The GMelina must Service 1934be thinned before they reach saleable size. Silviculturally,this mixture has not been a failure. Alternate strip mixturesare reported to have been successful.

Dipterocarpus turbina tus Tephrosia cand ida

T. candida is to be the nurse crop. The mixture isreported to have been more successful than that withGMelina artorea.

Indian ForestService 1934

Acacia auriculifOrmis ) Ram Prasad & CamireA.campylacantha 1988GMelina artorea BambooHybrid EucalyptusIbngamia pinnata

all showed rather better growth with bamboo.Albizia procera showed rather worse growth with bamboo.

Cinamomum zeylanicum Tectona grandis Streets 1962

Lalbergia sissoo in mixture with various indigenous species. Streets 1962

Eucalyptus globulus Acacia mearnsii Samraj et al 1977

Shorea robusta Grevillea pteridifolia Ram Prasad 1988Eucalyptus camaldulensisTacna ciliataPinus kesiya

SWietenia macrophylla Tectona grandis Streets 1962tried between 1879 & 1896, but abandoned because of hypsipylaand deer damage.

134

Mixtures of M. bambusoides and Teak seem to have been successful fran the econanic point of view in the Chittagong Hill Tract. This may also be true for mixtures with C. pergracile. For T. grandis and G. arborea there are reports of roth species suppressing each other. Fran the insect attack point of view the mixture is undesirable. x. dolabriformis is usually outgrCMn by the teak. Mixtures with A. catechu tend to separate into pure groups. Intimate mixture of T . grandis, A. catechu and D. sissoo has been tried. This has led to a mixture of T. grandis and D. sissoo, which is reported to have done well, though there are also reports of the opposite. Mixture with D. latifolia have not been successful, mainly due to browsing. Experiences of mixing with P. marsupium are discouraging. There are reports of mixture with A. hirsuta being silviculturally successful. Fran the econanic point of view the mixture is regarded as questionable. Reports regarding mixture with P. dahlbergioides indicate that one species is likely to suppress the other. Mixed crops with S. macrophylla are regarded as failures, S. macrophylla being suppressed on good soils and vice versa. Mixtures with B. tulda have led to suppression of the teak.

Bcrnbax malabricum Acacia catechu This seems to be a worthwhile mixture fran the econanic point of view.

Indian Forest SeI:vi.ce 1934

Dipterocarpus turbinatus Gnelina arborea Indian Forest G. arborea was to serve as a nurse crop. The Gnelina lffilSt SeI:vi.ce 1934 be thinned before they reach saleable size. Silviculturally, this mixture has not been a failure. Alternate strip mixtures are reported to have been successful.

Dipterocarpus turbinatus Tephrosia candida T. candida is to be the nurse crop. The mixture is reported to have been more successful than that with Gnelina arborea.

Indian Forest SeI:vi.ce 1934

Acacia auriculiformis A. canpy lacantha Gnelina arborea Hybrid Eucalyptus

) ) ) )

RiD Prasad & camire 1988

Pongamia pinnata ) all showed rather better growth with bamboo.

Albizia procera showed rather worse grCMth with bamboo.

Cinarranum zeylanicum Tectona grandis Streets 1962

Dalbergia sissoo in mixture with various indigenous species. Streets 1962

EUcalyptus globulus

Shorea rol:x1sta

SWietenia macrophy lla tried between 1879 and deer damage.

Acacia mearnsii Samraj et al 1977

Grevillea pteridifolia EUcalyptus camaldulensis Toona ciliata Pinus kesiya

RiD Prasad 1988

Tectona grandis Streets 1962 & 1896, but abandoned because of Hypsipyla

Pinus spp.

IfIf

If

The broadleavesestablished toused.

CUpressus spp.orCasuarina spp.

135

Tectona grandis Leucaena glaucaPositive effects are mentioned.

Tectona grandis Schleichera oleosaRecommendation for establishment of mixed teak forests.

Tectona grand's Leucaena glaucaAntidesma buniusterocarpus indiensis

Schoutenia ova taCinnamomum inersGluta renghasEugenia subglaucaSWietenia macrophyllaalbergia latifolia

Investigation of underplanting. L. glauca is found suitable for this.D. latifolia may be even better suited.

Altingia excelsa Castanopsis tungurrestCastanopsis javaniraRodocarpuq imbricata

Recommendations for establishment of non-teak plantations

Swietenia macrophylla Tectona grandis

Plyrica javaniraWenlandia rufescensWenlandia junghunianaPittosporum ferrugine

Streets 1962

Lahiri 1987

Bhatia & Kapoor 1984

Pittospermium mcnticolum Alphen de Veer 1950bSchima walichiiTarema incertaEugenia spp.QUercus spp.Leucosyke spp.

were recommended to forrn an understorey in conifer plantationssupport a pulpmill. More than one mixing species should he

Bakhoven 1930

in the mountains.

Becking 1928

necking 1928

Deventer 1913

Eidmann 1932

Harencarspel 1908

- MalabarSWietenia macrophylla Tectcna grandis Streets 1962

planted under 30 to 40 year old T.grandis at the final thinning.

Terminalia arjuna with Casuarina equisetifblia

- N.BengalAylia dolobriformis Tectona grandisalso Schima wallichii

Chukrasia tahularisblichaelia champa ca

Leucaena leucocephala Acacia niloticaPositive effects of the mixture were detected.

INDONESIA

135

- Malabar SWietenia macropbylla Tectona grandis streets 1962

planted under 30 to 40 year old T. grandis at the final thinning.

Tenninalia arjuna with

- N·BeDJal Xylia dolobrifozmis also schima wallichii

Chukrasia taJ::ularis Michaelia champaca

casuarina equisetifolia streets 1962

Tectona grandis Lahiri 1987

Leucaena leucocephala Acacia nilotica Positive effects of the mixture were detected .

Bhatia & Kapoor 1984

Pinus spp. "

Pittospezmium roonticolum Alphen de Veer 1950b Schima walichii

" "

Tarema incerta Eugenia spp.

" Olercus spp. " Leu=syke spp.

The broadleaves were reccmnended to fo:r:m an understorey in conifer plantations established to support a pUlpmill. More than one mixing species should be used.

Altingia excelsa " "

Reccmnendations

castano psis tungurrest castano psis javanica Podocarpus Mibricata

for establishment of non-teak plantations

SWietenia macropbylla Tectona grandis

Tectona grandis Leucaena glauca Positive effects are mentioned.

Tectona grandis Schleichera oleosa Reccmnendation for establishment of mixed teak forests.

Tectona grandis " " "

Leucaena glauca Antidesma bunius Fterocarpus indiensis Schoutenia ovata

" CinnaIoclnum iners " Gluta renghas " Eugenia subglauca " SWietenia macropbylla " Dalbergia latifolia

Bakhaven 1930

in the rrountains.

Becking1928

Becking 1928

Deventer 1913

Eicinann 1932

Investigation of underplanting. L . glauca is found suitable for this . D. latifolia may be even better suited.

Cupressus spp. or casuarina spp.

Myrica javanica Harencarspel. 1908 Wenlandia rufescens Wenlandia jungbuniana Pittosporum ferrugine

Glochidion variumAlbizia falcataria

Individual mixtures with either apressus or Casuarina species. Group mixingwith species that will not grow tall is preferred to individual mixing.

Tectona grandis Leucaena glaucaMixing is favourable only under special circumstances.

San talum album Leucaena glauca Kramer 1925Once the S. album roots reached the Leucaena, they developed well.

Tectona grandis Leucaena glaunaIf fires are avoided, mixtures develop vigorously.Natural mixing is easier and better than artificial.Diospyros celebica Tectona grandis

SWietenia macrqphylla )

Aleurites moluccanaSpathodea campanul ata )

Lagerstroemia speci osa )

Lurio zibenthinusArtocarpus heterqphyllus)Leucaena leucocephala )

KENYA

alpressus lusitanica Etatcya (?goetzenii)

Tectona grandis

NEPAL

Schima wallichii Pinus roxburghii Gilmour et al 1990and other indigenonR broadleaved trees by natural regeneration.

136

Pklaleuca leucodendron

All failures ?M. leucodendron allelopathy

in tall secondary forest

GMelina artorea

Albizia falcataria

Pterocarpus macrocarpus

Hart 1930b

KUnst 1918

Alrasjid 1985

Siregar et al 1986

Streets 1962

Grevillea robusta Graham 1949competes on equal terms to age 15, but has to be thinned heavilyberause of spreading crown causing butt sweep in the Cypress.

MALAYSIA (West)

Flindersia brayleyana

Swie tenia macrqphylla

Swietenia macrophylla

TeakAraucaria hunsteiniiShows some promise for controlling IMperata on more fertile sites.

MYAMIAR

Streets 1962

Streets 1962

Streets 1962

Leucaena leL7cephala Ng et al 1982

Streets 1962

136

Glochidion varil11ll Albizia falcataria

Individual mixtures with either CUpressus or Gasuarina species . Group mixing with species that will not grow tall is preferred to individual mixing.

Tectona grandis Leucaena glauca Hart 1930b Mixing is favourable only under special circumstances .

Santall11ll all:x1m Leucaena glauca Kramer 1925 Once the S. all:x1m roots reached the Leucaena, they developed well.

'I'ectona grandis Leucaena glauca Kunst 1918 If fires are avoided, mixtures develop vigorously. Natural mixing is easier and better than artificial. Diospyros celebica Tectona grandis Alrasjid 1985

SWietenia macrophylla ) Siregar et al. 1986 Aleurites JOOluccana ) Spathodea carrpanulata ) LagerstroEmia speciosa) Melaleuca leucodendron Durio zibenthinus ) Artocarpus heterophyllus) Leucaena leucocephala )

All failures ?M. leucodendron allelopathy

CUpressus lusitanica Lt1nb9ya (? goetzenii) streets 1962

Grevillea robusta Graham 1949 carrpetes on equal tenns to age 15, but has to be thinned heavily because of spreading cra-m causing butt sweep in the Cypress .

IWAYSIA (West)

Flindersia brayleyana in tall secondary forest streets 1962

SWietenia macrophylla Grrelina arrorea Streets 1962

SWietenia macrophylla Albizia falcataria streets 1962

Teak Leucaena leucocephala Ng et al. 1982 Araucaria hunsteinii "" Shows same promise for controlling Lmperata on more fertile sites .

Tectona grandis pter=a.rpus macrocazpus streets 1962

NEPAL

Schima wallichii Pinus roxburghii Gi11lP.lr et al. 1990 and other indigenous broadleaved trees by natural regeneration .

NEW CALEDONIA

Agathis lanceolata

fl

Experiment establishedgrows well.

Agathis,moorei Acacia mangium CiEl 1991Albizia falcatariaCasuarina equisetifoliaLeucaena leucocephala

Experiment established in 1981. The high mortality and poor growth of A.moored is thought to be due to the soil.

santalum austrocaledonicum Pinus caribaea eTtT 199171 Azillatrum gummiferum

Araucaria excel sea11 Araucaria luxurians

Leucaena leucocephalaLalbergia sissooAlbizia falr!atariaAcacia auriculiformisKhaya senegalensisTipuana tipuAcacia spirorbisAlbizia lebheckCasuarina equisetifoliaCasuarina deplancheanaCasuarina strictaAgathis ova ta

Experiment established in 1980. Good results were achieved with Albiziafalcataria, Rhaya senegalensis, Acacia spirorbis, Albizia lebbeck andCasuarina spp. Poor results with Pinus caribaea and Araucaria spp.

Agathis lanceolata AlbiziaExperiment established in 1986.

137

Acacia mearnsii Lai 1990Albizia falcatariaHerb plantsBroadleavecl trees

in 1978. In the shade of Albizia or Acacia, Agathis

Araucaria subulata Albizia falcatariaExperiment established in 1986.

NIGER

falcataria Cal. 1991

Clki 1991

Acacia tortilis C11-1 1991Acacia niloticaEalanites aegyptiacaAnogeissus leiocarpusLaltergia sissooExperiment established in 1984. 8 plots of 25 trees, 5 of each species,randomly planted.

NIGERIA

Azidarachta indica Crotolaria striata MacGregor 19344 months ht growth cut by nearly 50% in mixture from 4.04m to 2.4m

137

Agathis lanceolata Acacia ~ii CTFT 1990 " Albizia falcataria " Herb plants " Broadleaved trees

Experiment established in grows well.

1978 . In the shade of Albizia or Acacia, Agathis

Agathis moorei Acacia mangium CTFT 1991 " Albizia falcataria " Casuarina equisetifolia " Leucaena leucocephala

Experiment established in 1981 . The high mortality and poor grcMth of A . moorei is thought to be due to the soil.

Santalum austrocaledonicum " "

Pinus caribaea Arillastrum gurrrniferum Araucaria excelsea

" Araucaria luxurians " Leucaena leucocephala " Dalbergia sissoo " Albizia falcataria " Acacia auriculiformis " Khaya senegalensis " Tipuana tipu " Acacia spirorbis " Albizia lebbeck " Casuarina equisetifolia " Casuarina deplancheana " Casuarina stricta " Agathis ovata

CTFT 1991

Experiment established in 1980. Good results were achieved with Albizia falcataria, Khaya senegalensis, Acacia spirorbis, Albizia lebbeck and Casuarina spp. Poor results with Pinus caribaea and Araucaria spp.

Agathis lanceolata Albizia falcataria CTFT 1991 Experiment established in 1986.

Araucaria subulata Albizia falcataria CTFT 1991 Experiment established in 1986.

NIGER

Acacia tortilis CTFT 1991 Acacia nilotica Balanites aegyptiaca Anogeissus leiocarpus Dalbergia sissoo Experiment established in 1984 . 8 plots of 25 trees, 5 of each species, randcrnly planted.

NIGERIA

Azidarachta indica Crotolaria striata MacGregor 1934 4 months ht gra-lth cut by nearly 50% in mixture fran 4 . 04m to 2.4m

Chlorqphcra excelsa

Erythrqphleum ivorenseNot a success.

138

Teak MacGregor 1934

Cola cordifolia Teak Marparegor 1934suppressed, but healthy & 80% survival; introduced to modify adverseeffect on the soil.

SWietenia macrqphylla Securinega flexuosa1988 experiment - promising.

Nauclea diderrichii Henry 1960

Khaya grandifoliola Teak Madaregor 1934At age 20 well above teak (21 m) - a good mixture.

K.gTandifoliola Triplochiton scleroxylon MacGregor 1934overtopped by T.scleroxylon which will have to be thinned.

K.senegalensis Dalbergia sissoo MacGregor 1934fungal attack on D.sissoo

K.senegalensis Teak MacGregor 1934heavy borer damage in the Khaya.

Lophira alata Teak Henry 1960Not a success.

Mnscnia altissima Crotolaria striata MacGregor 1934

Mitragyna ciliata in any mixture only a success in law Henry 1960lying areas.Tctcna grandis with Cassia siamea Streets 1962

PHILIPPINES

Tectona grandis Leucaena leucocephala Granert & Cadampog 1980SWietenia macrophylla L. leucocephala

SENEGAL

Eucalyptusvcamaldulensis Acacia hclosericea UM. 1991Albizia lebbekAnacardium occidentaleAzadirachta indicaCassia siameaCasuarina equisetifoliaPros opis chilensis

Experiment established in 1979. The only coMbination with normal growth isthat between E. camaldulensis and A. indica.

SOLCKIN ISLANDS

Solomon Islands 1988b

Leucaena leucccephalaform of S. macTophylla thought to be superior, but L.leucocephala proneto attacks from Phellinus noxius and lieteropsylla cubana.

138

Chlorophora excelsa Teak

COla =rdifolia Teak suppressed, rut healthy & 80% effect on the soil.

~1934

~1934 survival; introduced to m::xlify adverse

Erythrophleum i vorense Not a success.

Nauclea diderrichii Hemy 1960

Kbaya grandifoliola Teak ~ 1934 At age 20 well above teak (21 m) - a good mixture.

K.grandifoliola Triplochiton scleroxylon ~ 1934 overtopped by T.scleroxylon which will have to be thinned.

K.senegalensis Dalbergia sissoo fimgal attack on D.sissoo

K.senegalensis Teak heavy borer damage in the Kbaya.

Lophira alata Teak Not a success.

~onia altissima Crotolaria striata

Mitragyna ciliata in any mixture only a success in low lying areas. Tectona grandis with cassia siamea

~1934

~1934

Hemy 1960

~1934

Hemy 1960

streets 1962

Tectona grandis SWietenia macrophylla

I.eucaena leu=phala Granert & Cadanpng 1980 L.leu=phala

EUcalyptus camaldulensis " " "

Acacia holosericea Albizia lebbek Anacardium occidentale Azadirachta indica

" cassia siamea " casuarina equisetifolia " Prosopis chilensis

CTFl' 1991

Experiment established in 1979. The only combination with normal growth is that between E. camaldulensis and A. indica.

SWietenia macrophylla Securinega flexuosa Solanon Islands 1988b 1988 experiment - promising .

I.eucaena leu=phala form of S. macrophylla thought to be superior, rut L.leu=phala prone to attacks fran Phellinus noxius and Heteropsylla cuhma.

139

Terminalia calamansanaiT.calamansanai has too spreading and vigorous a crown.The following are not recorded as having buen tried but were consideredunsuitable - crowns too spreading - Paraserianthes falcataria,Anthocephalus chinensis

SRI LANKA

SWietenia macrqphylla Artocarpus integrifolius Streets 1962

SWietenia macrqphylla Tectona grandisArtocarpus integrifolius

TAIWAN

Taiwania cryptomerioidesFaulownia taiwania in mixture

MITZANIA

Cinamcmum camphora Ju_niperus procera

TRINIDAD

Tectona grandis Copaifera officinalis Bell 1973Cedrela mexicanaCbrdia alliodora

all of which tended to be shaded out by the teakli.yronima caribaeaTabebuia serratifOlia.5. rsonima spicata

Terminalia obovatanatural regeneration normally slashed in cultural operations.

UGANDA

Chlorqphora excelsa Eucalyptus Dawkins 1949satisfactory when C.excelsa near drains (malarial control sites).

Cassia siameatoo much root competition.

Vernonia amygdalinaDoes not shade out grass; no economic value.

.harungana madagasnariensisdrought sensitive.

Igarkhamia platycalyxpoor at shading out grass, but economically useful.

The following were considered to be failures for unspecifiedreasons Artocarpus sp

Canarium schweinfurthii )

Ceara rubberClausena anisataCassia bicapsularis

MUttiah 1965

Un et al 1979

Streets 1962

139

TeIminalia calaITBIJSanai T.calaITBIJSanai has too spreading and vigorous a crown. The following are not recorded as having been tried but were considered unsuitable - crowns too spreading - Paraserianthes falcataria, Anthocephalus chinensis

SRI LANKA

SWietenia macrophylla

SWietenia macrophylla

Taiwania cryptarnerioides Paulownia taiwania

Cinamcmum carrphora

Artocarpus integrifolius

Tectona grandis Artocarpus integrifolius

in mixture

Juniperus procera

streets 1962

folIttiah 1965

Un et al 1979

Streets 1962

Tectona grandis Copaifera officinalis Bell 1973 Cedrela mexicana Cordia allicxiora

all of which tended to be shaded out by the teak Hyronima caribaea Tabebuia serratifolia Byrsonima spicata TeIminalia obovata

natural regeneration nonnally slashed in cultural operations.

Chlorophora excelsa Eucalyptus Dawkins 1949 satisfactory when C.excelsa near drains (malarial control sites).

Cassia siamea too much root oompetition.

Vemonia amygdalina Does not shade out grass; no econanic value.

Harungana madagascariensis drought sensitive.

Markhamia platycalyx poor at shading out grass, rut econanically useful.

The following were considered to be failures for unspeCified reasons Artocarpus sp )

Canarium schweinfurthii ) Ceara rubber ) Clausena anisata ) Cassia bicapsularis )

Chlorqphora excelsa

Rhaya grandifoliolahas worked well on

Chlorophora excelsa

140

Euphorbia tirucalliFicus sppTbona seriataT.ciliata

Ihyllanthus discoideus

GMelina al-torea"better" sites

Eucalyptus

1986

1986

1986

1986

1986

1986

1988-1989

1988-1989

1988-1989

1988-1989

1988-1989

1988-1989

1988-1989

Streets 1962

Mixtures recorded, apart from the data bank, during a visit to Nogentsur Miarne, in 1991.

Mixture PeriodCountry

Acacia auriculifon7u:s/ BeninEucalyptus camaldulensis

Acacia auriculiformis/ BeninLeucaena leucocephala

Eucalyptus tereticornis/ BeninEucalyptus torreliana

Eucalyptus tereticornis/ BeninEucalyptus camaldulensis

EUcalyptus tereticornis/ BeninLeucaena leucccephala

Acacia auriculiformis/ BeninEucalyptus torreliana

Tectona grandis/ BeninAcacia maconochieana

Tectona grandis/ BeninAcacia tenuissima

Tectona grandis/ BeninAcacia tumida

Tectona grandis/ BeninAnogeissi LC leiocarpus

Tectona grandis/ BeninAzadiracta indica

Tectona grandis/ BeninCedrela odorata

Tectona grandis/ BeninChlorophora excelsa

Chlorophora excelsa &

140

EUphorbia tirucalli ) Ficus spp ) Ta?na serrata ) T.ciliata )

Phyllanthus discoideus &

Khaya grandifoliola GlElina arborea has worked well on "better" sites

Chlorophora excelsa Eucalyptus Streets 1962

Mixtures recorded, apart fran the data bank, during a visit to CI'FT, Nogent sur Marne, in 1991.

Mixture COtmtry Period

Acacia auriculiformis/ Benin 1986 EUcalyptus camaldulensis

Acacia auriculiformis/ Benin 1986 Leucaena leucocephala

EUcalyptus tereticornis/ Benin 1986 EUcalyptus torreliana

EUcalyptus tereticornis/ Benin 1986 EUcalyptus camaldulensis

EUcalyptus tereticornis/ Benin 1986 Leucaena leucocephala

Acacia auriculiformis/ Benin 1986 Eucalyptus to=eliana

Tectona grandis/ Benin 1988-1989 Acacia maconochieana

Tectona grandis/ Benin 1988-1989 Acacia tenuissima

Tectona grandis/ Benin 1988-1989 Acacia tumida

Tectona grandis/ Benin 1988-1989 Anogeissus leiocarpus

Tectona grandis/ Benin 1988-1989 Azadiracta indica

Tectona grandis/ Benin 1988-1989 Cedrela odorata

Tectona grandis/ Benin 1988-1989 Chlorophora excelsa

141

Tectona grandis/ Benin 1988-1989

Khaya grandifolia

Tectona grandis/ Benin 1988-1989Rhaya senegalensis

Tectona grandis/ Benin 1988-1989Tbrminalia ivorensis

Tectona grandis/ Benin 1988-1989Terminalia superba

Rhaya senegalensis/ Benin 1988-1989hbloptelea grandis

Rhayagrandifolia/ Benin 1988-1989hblqptelea grandis

Diospyrosmespiliformis/ Benin 1988-1989GMelina artorea

Chlorqphora excelsa/ Benin 1988-1989Afzelia africana

Afzelia africana/ Benin 1988-1989Acacia amliceps

Pinuspatula/ BurundiCallitris spp.

Khaya senegalensis/ Cameroon 1984-1986

Lalbergia sissoo

Acacia senegalensis/ Cameroon 1987

Khaya senegalensis/Azadirachta indica

Schizolobium parahybun/ Ecuador 1977

Cbrdia alliodora

Tarrieta utilis/ Cate d'Ivoire 1926-1960

Rhaya ivorensis

Triplochytcn scleroxylon/ Cate d'Ivoire 1961-1964Rhaya ivorensis

Triplochytcn scleroxylon/ Cate d'Ivoire 1961-1964Tieghemilla heckelii

Triplochyton scleroxylon/ Cate d'Ivoire 1961-1964GMelina spp.

Triplochytcn scleroxylon/ Cate d'Ivoire 1961-1964Terminalia superta

Triplcchyton scleroxylon/ Cate d'Ivoire 1961-1964Tectona grandis

141

Tectona grandis/ Benin 1988-1989 Khaya grandifolia

Tectona grandis/ Benin 1988- 1989 Khaya senegalensis

Tectona grandis/ Benin 1988-1989 Terminalia i vorensis

Tectona grandis/ Benin 1988-1989 Terminalia superba

Khaya senegalensis/ Benin 1988-1989 Holoptelea grandis

Khaya grandifolia/ Benin 1988-1989 Holoptelea grandis

Diospyros mespilifonnis/ Benin 1988-1989 GrElina arborea

Chlorophora excelsa/ Benin 1988-1989 Afzelia africana

Afzelia africana/ . Benin 1988-1989 Acacia amliceps

Pinus patula/ Burundi Callitris spp.

Khaya senegalensis/ cameroon 1984-1986 Dalbergia sissoo

Acacia senegalensis/ cameroon 1987 Khaya senegalensis/ Azadirachta indica

Schizolobium parahybum/ Ecuador 1977 Cordia alliodora

Tarrieta utilis/ cOte d' Ivoire 1926-1960 Khaya ivorensis

Triplochyton scleroxy lon/ cOte d' Ivoire 1961-1964 Khaya ivorensis

Triplochyton scleroxylon/ cOte d' Ivoire 1961-1964 Tieghemilla heckelii

Triplochyton scleroxylon/ cOte d' Ivoire 1961-1964 GrElina spp.

Triplochyton scleroxylon/ cOte d' Ivoire 1961-1964 Terminalia superba

Triplochyton scleroxylon/ cOte d' Ivoire 1961-1964 Tectona grandis

Acacia mar2gium/Acacia auriculifonnis

Terminalia superba/Tenninalia ivorensis

Terminalia superba/Teutona grandis

Eucalyptus carnaldulensis/Indigafera teya.nannii

EUcalyptus carnaldulensis/Cassia siamea

EUcalyptus camaldulensis/Acacia cyanophylla

Eucalyptus microtheca/Indigoféra tey5mannii

Eucalyptus robusta/Acacia mangiurn

Lophira alata/Swietenia macrophylla

Lqphira alata/Teutona grandis

Tectona grandis/Lophira alata

Teutona grandis/Nauclea diderrichii

Tectona grandi.s/Lovoa trichilioides

Tectona grandis/Swietenia ma crophyl 1 a

Erythrophleun ivorense/Nauclea diderrichii

Nauclea diderrichii/Khaya ivorensis

NaUclea cLiderrichii/Lovoa trichilioides

Nauclea diderric,hii/Entar2drophragna angolense

Nauclea di derrichii/Entandrophragma cyllndricum

142

Cae d'Ivoire 1985-1988

Cate d'Ivoire 1985-1989

Cate d'Ivoire 1985-1989

Madagascar 1951-

Madagascar 1951 -

Madagascar 1951 -

Madagascar 1951-

Madagascar 1988

Nigeria 1918-1939

Nigeria 1918-1939

Nigeria 1949-1960

Nigeria 1949-1960

Nigeria 1949-1960

Nigeria 1949-1960

Nigeria 1949-1960

Nigeria 1949-1960

Nigeria 1949-1960

Nigeria 1949-1960

Nigeria 1949-1960

142

Acacia mangium/ cote d'Ivoire 1985-1988 Acacia auriculifonnis

TeIminalia superb3./ cote d'Ivoire 1985-1989 TeIminalia ivorensis

TeIminalia superb3./ cote d' Ivoire 1985-1989 Tectona grandis

EUcalyptus camaldulensis/ Madagascar 1951-Indigofera teysmannii

EUcalyptus camaldulensis/ Madagascar 1951-cassia siarrea

EUcalyptus camaldulensis/ Madagascar 1951-Acacia cy.anophylla

EUcalyptus mi=theca/ Madagascar 1951-Indigofera teysmannii

EUcalyptus robusta/ Madagascar 1988 Acacia mangium

Lophira alata/ Nigeria 1918-1939 SWietenia macrophylla

Lophira alata/ Nigeria 1918-1939 Tectona grandis

Tectona grandis/ Nigeria 1949-1960 Lophira alata

TectOlla grandis/ Nigeria 1949-1960 Nauclea diderrichii

TectOlla grandis/ Nigeria 1949-1960 LoV03 trichilioides

Tectona grandis/ Nigeria 1949-1960 SWietenia macrophy lla

Erythrophleum ivorense/ Nigeria 1949-1960 Nauclea diderrichii

Nauclea diderrichii/ Nigeria 1949-1960 Khaya ivorensis

Naticlea diderrichii/ Nigeria 1949-1960 LoV03 trichilioides

Nauclea diderrichii/ Nigeria 1949-1960 Entandrophragma angolense

Nauclea diderrichii/ Nigeria 1949-1960 Entandrophragma cy lindricum

Lovoa trichilioides/ NigeriaKhaya ivorensis

Acacia melanoxylon/ RwandaPinus radiata

Eucalyptus camaldulensis Senegal(nicrotheca)/Prosqpis juliflora

Eucalyptus camaldulensis Senegal(microtheca)/Acacia holoserica

143

Tectona grandis/ Togo 1910Cassia siamea

lb.ctona grandis/ Togo 1910Albizzia zygia

Tectona grandis/ Togo 1910Elythrophleum guinensii

Acacia mangiun/ Togo 1982-1988Eucalyptus tereticornis

Acacia auricliformis/ Togo 1982-1988Eucalyptus torreliana

Eucalyptus tereticornis/ Togo 1988Eucalyptus torreliana

Eucalyptus saligna/ Uganda 1918-1930Markhamda platycalyx

EUcalyptus robusta/ Uganda 1960-1965Grevillea robusta

EUcalyptus robusta/ Uganda 1960-1965CUpressus lusitanica

EUcalyptus robusta/ Uganda 1960-1965EUcalyptus spp.

EUcalyptus robusta/ Uganda 1960-1965Tbona ciliata

1949-1960

1983

1910

1910

Eucalyptus spp./ SenegalGmelina a_rborea

Tectona grandis/ TogoLeucaeana glauca

Tectona grandis/ TogoMaya senegalensis

143

Iovoa trichilioides/ Nigeria 1949-1960 Khaya ivorensis

Acacia melanoxylon/ Rwanda Pinus radiata

Eucalyptus camaldulensis Senegal {microtheca}/ Prosopis juliflora

Eucalyptus camaldulensis Senegal {microtheca}/ Acacia holoserica

Eucalyptus spp./ Senegal 1983 GJElina aroorea

Tectona grandis/ Togo 1910 Leucaeana glauca

Tectona grandis/ Togo 1910 Khaya senegalensis

Tectona grandis/ Togo 1910 Cassia siamea

Tectona grandis/ Togo 1910 Albizzia zygia

Tectona grandis/ Togo 1910 Erythrophleum guinensii

Acacia mangium/ Togo 1982-1988 Eucalyptus tereti=rnis

Acacia auriclifoIInis/ Togo 1982-1988 Eucalyptus torreliana

Eucalyptus tereti=rnis/ Togo 1988 Eucalyptus torreliana

Eucalyptus saligna/ Uganda 1918-1930 Markhamia platy calyx

Eucalyptus rol:xIsta/ Uganda 1960-1965 Grevillea rol:xIsta

Eucalyptus rol:xIsta/ Uganda 1960-1965 Cupressus lusitanica

Eucalyptus robusta/ Uganda 1960-1965 Eucalyptus spp.

Eucalyptus rol:xIsta/ Uganda 1960-1965 1bona ciliata

144

Aucoumea klair2eana/ Zaire 1942-1943

Cassia siamea

harongapaniculata/ Zaire Before 1953SMithia Lequaerti

harongapaniculata/ Zaire Before 1953Dodonea viscosa

harongapaniculata/ Zaire Before 1953Sestania spp.

Eucalyptus spp./ Zaire Before 1953Bridelia ferruginea

Eucalyptus spp./ Zaire Before 1953Bridelia micrantha

SMithiabequaerti/ Zaire Before 1953Bridelia ferruginea

Smithia bequaerti/ Zaire Before 1953Sakersia laurentii

SMithiabequaerti/ Zaire Before 1953Myrica salicifolia

Smithiabequaerti/ Zaire Before 1953Lacnqpylis spp.

SMithia tequaerti/ Zaire Before 1953

Trana spp.

SMithia tequaerti/ Zaire Before 1953

Afailchantia spp.

Dodonea spp./ Zaire Before 1953Bridelia spp.

Dodonea spp./ Zaire Before 1953Trema

Dodonea spp./ Zaire Before 1953Haronga spp.

Aarkhamia lutea/ Zaire Before 1953

SMithia spp.

Aarkhamia lutea/ Zaire Before 1953

Dodonea spp.

144

Aucoumea klaineanal Zaire 1942-1943 Cassia siamea

Haronga paniculatal Zaire Before 1953 Snithia bequaerti

Haronga paniculatal Zaire Before 1953 Dcx10nea viscosa

Haronga paniculatal Zaire Before 1953 Sesi:Enia spp.

Eucalyptus spp./ Zaire Before 1953 Bridelia ferruginea

Eucalyptus spp./ Zaire Before 1953 Bridelia micrantha

Sni thia bequaertil Zaire Before 1953 Bridelia ferruginea

Snithia bequaertil Zaire Before 1953 Sakersia laurentii

Snithia bequaertil Zaire Before 1953 MYrica salicifolia

Sni thia bequaertil Zaire Before 1953 Lacnopylis spp.

Sni thia bequaertil Zaire Before 1953 Trana spp.

Snithia bequaertil Zaire Before 1953 Markhamia spp.

D::Jdonea spp. I Zaire Before 1953 Bridelia spp.

D::Jdonea spp. I Zaire Before 1953 Trana

D::Jdonea spp. I Zaire Before 1953 Haronga spp.

Markhamia luteal Zaire Before 1953 Snithia spp.

Markhamia luteal Zaire Before 1953 D::Jdonea spp.

145

APPENDIX 4SANDALWOOD

Mmblers of the family Santalaceae are root hemi-parasites and, thoughthey have been recorded as parasitising grasses and may on occasion existwlthout the benefit of a host, they are almost always associated with othertrees and shrubs. Mixed planting has therefore been found to he essential inthe establishment and management of sandalwood.

The genus Santalum occurs over a wide geographic area.Australia (1) S.spicatum, S.acuminatum,from Cape York to Victoria and S.lanceolatum, S.murrayanum,through to West Australia S.obtusifolium. (4)New Guinea (1) S.macgregoriNew Caledonia & Vanuatu (1) S.austrocaledcnicumFiji (1) S.yasiTonga (4) S.yasiHawaii (3) S.elipticum, S.freycinetianum

S.haleakalae, S.paniculatumTahiti, Marquesas, Henderson Island S.insulareAustral Islands, Cm& Islands,Society Islands (4)East Indonesia (1)(now almost S.albumentirely confined to West Timor)India (2) (primarily on the S.alhumDeccan plateau of Karnataka & TamilNadu, but found throughout India)Juan Fernandez (4) S.fernandezianum (extinct)

McKinnell (1990)Rai (1990)Hirano (1990)Applegate et al (1990)

The highest grade logs are used for carving and S.album produces thehighest quality logs, because it is close grained and has a high oil content;prices up to US$ 9,400 per ton can be obtained in India. Lower grade logs goto the incense market at a price varying from US$ 2,000 to US$ 5,000 per ton,though roots and butts of S.spicatum and S.album, which have a higher oilcontent, may fetch up to US$ 7,000 per ton. Australia supplies most of theworld incense market through Hong Kong and Taiwan. Wood chips and powderedwood command prices of around US$ 2,300 per ton. Sandalwood oil is chieflyproduced in India, where 1 ton of S.album heartwood can produce 60 kg of oil,the export price of which starts at US$ 1,500 per kg. The market for oil isprimarily for perfumeries in France and New York (Applegate et al. 1990).

Yields of heartwood oil vary with the species (MtKinnell 1990).5 - 7% S.album and S.yasi3 - 6% S.austrocaledonicum

2% S.spicatum

S.album has a wood density of 930 - 950 kg/e.

The yield of oil from sane species such as S.acuminatum andS.lanceolatum found in Australia are so low that oil is not usually distilledfrom these species (MtKinnell 1990).

145

APPENDIX 4

Members of the family Santalaceae are root hemi-parasites and, though they have been recorded as parasitising grasses and may on occasion exist without the benefit of a host, they are almost always associated with other trees and shrubs. Mixed planting has therefore been found to be essential in the establishment and management of sandalwood.

The genus Santalum occurs Australia (1)

over a wide geographic area.

fran cape York to Victoria and through to West Australia New Gli.nea (1) New Caledonia & Vanuatu (1) Fiji (1) Tonga (4)

S.spicatum, S.acuminatum, S . lanceolatum, S.murrayanum, S .abtusifolium. (4) S .macgregori S. austrocaledonicum

S.yasi S.yasi

Hawaii (3) S. elipticum, S. freycinetianum S.haleakalae, S.paniculatum

Tahiti, Marquesas, Henderson Island S.insulare Austral Islands, Cook Islands, Society Islands (4) East Imonesia (1) (no.v almost entirely confined to West Tirror) India (2) (primarily on the Deccan plateau of Karnataka & Tamil Nadu, but found throughout India) Juan Fernandez (4)

(1) McKinnell (1990) (2) Rai (1990) (3) Hirano (1990) (4) Applegate et al (1990)

S.album

S .album

S . femandezianum (extinct)

The highest grade logs are used for carving and S.album produces the highest quality logs, because it is close grained and has a high oil content; prices up to US$ 9,400 per ton can be obtained in India. Lc::Mer grade logs go to the incense market at a price varying fran US$ 2.,000 to US$ 5,000 per ton, though roots and butts of S.spicatum and S.album, which have a higher oil content, may fetch up to US$ 7, 000 per ton. Australia supplies most of the world incense market through Hong Kong and Taiwan. wood chips and pcu:lered wood ccmrand prices of around US$ 2,300 per ton. Sandalwood oil is chiefly produced in India, where 1 ton of S .album heartwood can produce 60 kg of oil, the export price of which starts at US$ 1,500 per kg. The market for oil is primarily for perfumeries in France and New York (ApPlegate et al. 1990).

Yields 5 - 7% 3 - 6%

of heartwood oil vary with the S . album and S. yasi

species (McKinnell1990).

2% S . austrocaledonicum S.spicatum

S. album has a wood density of 930 - 950 kg/m3•

The yield of oil fran sane species such as S .acuminatum and S.lanceolatum found in Australia are so lo.v that oil is not usually distilled fran these species (McKinnell1990).

146

S.album is the most valuable species. It has been exploited for manycenturies in India, West Timor, SuMba and Flores in Indonesia and it is nowbeing introduced into many countries (e. g. Hawaii (Hirano 1990) , Java and Bali(Applegate et al 1990), West Australia (McKinnell 1990)). It has beensuggested that S album is an introduced tree in India, but that theory hasbeen rejected on the grounds that the tree is so deeply involved in Indianliterature, ethos and culture (Rai 1990).

There are records of sandalwood use in India 4,000 years ago (Rai 1990)and 1,500 years ago in Hawaii (Merlin and Ravenswaay 1990), but exploitationincrPaed immensely wlth the exploration of the Pacific by the West in the18th century. By about 1870 there was virtually none left on many of thePacific Islands and only recently have measures been introduced to regulateexploitation of sandalwood in order to conserve it. Although the stocking ofS.spicatum in West Australia is la w (2/ha) the area over which it grows is solarge that, despite largely unregulated cutting in the last century and thebeginningof the 20th century, large volumes are still available. The historyof sandalwood exploitation in Western Australia (Statham 1990) gives a goodidea of the fluctuations of the trade. Exports of S.spicatum started in 1843and rose as high as 9,600 tons in sane years at the end of the 19th andbeginning of the 20th century. From the early 1920s, when up to 14,300 tonsa year were exported, exports fell to about 1,000 tons a year in the late1930s. During the Second World War exports rPased, but have now built up toabout 1,800 tons a year with an export value of A4 11.5 million in 1989.Exploitation is now carefully regulated, but nevertheless it has beenestimated that natural stocks will only last about another sixty years(MtKinnell 1990). Currently about half the sandalwood harvest is dead wood,but the practice of exploiting the whole tree, including the butt and roots,which have the highest oil content, continues (McKinnell 1990). As recentlyas 1954 a Forests Department report stated that the results generally fromexperimental work did not warrant any attempt to gro sandalwood on a largescale (Statham 1990), but nevertheless "pullers" were encouraged to replacetrees with sandalwood nuts. More recently the Sandalwood Research Institutehas been investigating the possibility of introducing S.album which it isexpected will have a rotation of 30 years as against 60 to 80 years forS.spicatum; these trials are promising (AcKinnell 1990).

Santalum spp. can grow on a wide range of soils, in temperatures of 0°Cto 40°C and rainfall from 500 mm to 3,000 mm (Neil 1990). In India it isconsidered to be a tree of dry deciduous forests and when a site becomes mesicsandalwood retreats to drier sites, but sandalwood is fire tender (Rai 1990).In Queensland it has been noted that it occurs in open woodlands, but tendsto be more common on the outer edge of scrubs of Itkqaleuca aCacioides andExcoecariaparvifolia (guttapercha) around drainage lines. On these sites,at the interface of the Macacioidés scrUb and the open woodland, the grassis sparse and hot fires which are common in the densely grassed open woodlanddo not occur (Applegate et al 1990b). In Western Australia it grows on sitesreceiving little rain and regeneration appears to be dependent on a successionof wet years.

Sandalwood is a root hemiparasite that is known to parasitise at least300 species of plants, ranging from grasses to trees; it has also been knownto parasitise other sandalwood trees (Rai 1990). It attaches itself to itshost by haustoria and appears to obtain N, P and basic amino-acids from thehost while obtaining Ca and K from the soil (Neil 1990). No reference wasfound to its effect on the host, but it does not appear to be debilitating.In fact the host tree has to be carefully chosen not to be so vigorous as tosuppress the sandalwood.

146

S. album is the most valuable species. It has been exploited for many centuries in India, West Tirror, Surnl:a and Flores in Indonesia and it is nON' being introduced into many countries (e. g. Hawaii (Hirano 1990), Java and Bali (Applegate et al 1990), West Australia (McKinnell 1990)) . It has been suggested that S.album is an introduced tree in India, rot that theory has been rejected on the grounds that the tree is so deeply involved in Indian literature, ethos and culture (Rai 1990) .

There are records of sandalwood use in India 4,000 years ago (Rai 1990) and 1,500 years ago in Hawaii (Merlin and Ravenswaay 1990), rot exploitation increased immensely with the exploration of the Pacific by the West in the 18th century. By about 1870 there was virtually none left on many of the Pacific Islands and only recently have measures been introduced to regulate exploitation of sandalwood in order to conserve it . Although the stocking of S.spicatum in West Australia is ION' (2/ha) the area over which it gr= is so large that, despite largely unregulated cutting in the last century and the beginning of the 20th century, large volumes are still available . The history of sandalwood exploitation in Western Australia (statham 1990) gives a good idea of the fluctuations of the trade. Exports of S. spicatum started in 1843 and rose as high as 9,600 tons in sane years at the end of the 19th and beginning of the 20th century. Fran the early 1920s, when up to 14,300 tons a year were exported, exports fell to about 1,000 tons a year in the late 1930s. During the Second World War exports ceased, rot have nON'roilt up to about 1,800 tons a year with an export value of A$ 11.5 million in 1989. Exploitation is nON' carefully regulated, rot nevertheless it has been estimated that natural stocks will only last about another sixty years (McKinnell 1990) . currently about half the sandalwood harvest is dead wood, rot the practice of exploiting the whole tree, including the rott and roots, which have the highest oil content, continues (McKinnell 1990). As recently as 1954 a Forests Department report stated that the results generally fran experilrental work did not warrant any attempt to grON' sandalwood on a large scale (statham 1990), rot nevertheless "pullers" were encouraged to replace trees with sandalwood nuts . M:>re recently the Sandalwood Research Institute has been investigating the possibility of introducing S.album which it is expected will have a rotation of 30 years as against 60 to 80 years for S.spicatum; these trials are pranising (McKinnell 1990) .

Santalum spp . can grON' on a wide range of soils, in temperatures of O°C to 40°C and rainfall fran 500 rrm to 3,000 rrm (Neil 1990). In India it is considered to be a tree of dry deciduous forests and when a site becanes mesic sandalwood retreats to drier sites, rot sandalwood is fire tender (Rai 1990). In Q..Ieensland it has been noted that it occurs in open woodlands, rot tends to be more common on the outer edge of scrubs of Melaleuca aeacioides and Excoecaria parvifolia (gutta percha) around drainage lines . On these sites, at the interface of the M.acacioides scrub and the open woodland, the grass is sparse and hot fires which are common in the densely grassed open woodland do not oc= (Applegate et al 1990b). In Western Australia it gr= on sites receiving little rain and regeneration appears to be dependent on a succession of wet years.

Sandalwood is a root hemiparasite that is kn= to parasitise at least 300 species of plants, ranging fran grasses to trees; it has also been kn= to paras:Ltise other sandalwood trees (Rai 1990) . It attaches itself to its host by haustoria and appears to obtain N, P and basic amino-acids fran the host while obtaining ca and K fran the soil (Neil 1990) . No reference was found to its effect on the host, rot it does not appear to be debilitating. In fact the host tree has to be carefully chosen not to be so vigorous as to suppress the sandalwood.

147

When sandalwood is raised in nurseries the seedling should he allowedto attach itself to host and this is achieved by raising the sandalwood andhost in the same pot (Neil 1990, Rai 1990) . But in Western Australia thistechnique is considered to be only a research tool and the risk of rupturingthe sandalwood-host connection in planting out is too high for commercialplanting; for commercial planting direct seeding is advocated, but only withthe expectation of getting 1% of the seed through to a tree (MCKinnell 1990) .In India a hollowed bamboo is used for direct seeding into thickets (Rai1990) . Despite the observation from West Australia several countries havefound that a dual host system produces the best results when raisingsandahaood artificially. At the nursery stage a primary host is used and thisshould be a low growing, short-lived shrUb; Cajanus cajan in India (Rai 1990) ,Sestonia grandiflora, Breynia cerrua, Amaranthus spp. , Atdr_icago spp . andtomato, Calotrqpis, Capsicum in Timor (Neil 1990; MCKinnell 1990),

Alternanthera sessilis in Vanuatu (Bule and Daruhl 1990) , Gastrolobiummicrocarpum and Acacia pulchella in Western Australia wheat belt and Atriplexrhagodioides, Cratystylis subspinescens and Mariana polysterygia in the aridzone (McKinnell 1990) . M.polysterygia is considered a particularly good hostbecause it is thorny and gives protection against browsing to which sandalwoodis particularly susceptible. On planting the sandalwood into the f ield theseedling should be established near a perennial secondary host; this isusually achieved by planting the sandalwood and primary host in alternate rowswith a secondary host at two to three metre spacing (Rai 1990) . Secondaryspecies recommended include Albizia spp. , Acacias (particularly A.nilotica)and other legumes such as Eauhinia biloto, Caltergia sissoo also Terminaliaspp. in India (Neil 1990) ; Casuarina equisetifolia, Itngamia pinnata, Mediaazedarach, Wrightia tinctoria and Cassia siamea (Rai 1990) , but Cassia fistulaand Acacia auriculiformis are considered indifferent hosts (Ananthia et al1988); A1bizia falcataria, A. lebbek, Acacia spirorbis, Ealtergia spp.,Casuarina spp. and RToya senegalensis are recommended in New Caledonia, butPiDUS oariboea and Araucaria spp. gave poor results (cze2 1991 ) ; Araciaacuminata and A.aneura give good results in Western Australia (MtKinnell1990) .

147

When sandalwoo:l. is raised in nurseries the seedling should be allowed to attach itself to host and this is achieved by raising the sandalwoo:l. and host in the same pot (Neil 1990, Rai 1990) . But in Western Australia this technique is CilllSidered to be only a research tool and the risk of rupturing the sandalwoo:l.-host connection in planting out is too high for ccmrercial planting; for ccmrercial planting direct seeding is advocated, but only with the expectation of getting 1% of the seed through to a tree (McKinnell 1990). In India a hollowed bamI:xx:> is used for direct seeding into thickets (Rai 1990). Despite the observation from West Australia several countries have found that a dual host system produces the best results when raising sandalwoo:l. artificially. At the nursery stage a primary host is used and this should be a lCM grCMing, short-lived shrub; Cajanus cajan in India (Rai 1990), Sesbania grandiflora, Breynia cerrua, Amaranthus spp., Medicago spp. and tomato, Calotropis, Capsicum in TiIror (Neil 1990; McKinnell 1990) , Altemanthera sessilis in Vanuatu (Bule and Daruhl 1990), Gastrolobium microcazpum and Acacia pulchella in Western Australia wheat belt and Atriplex rhagodioides, Cratystylis su1;spinescens and Mariana polysterygia in the arid zone (McKinnell 1990). M.polysterygia is considered a particularly good host because it is thorny and gives protection against brCMSing to which sandalwoo:l. is particularly susceptible . . On planting the sandalwoo:l. into the field the seedling should be established near a perennial secondary host; this is usually achieved by planting the sandalwoo:l. and primary host in alternate rCMS with a secondary host at two to three metre spacing (Rai 1990). Secondary species recarrrended include Albizia spp., Acacias (particularly A .nilotica) and other legumes such as Bauhinia biloba, Dalbergia sissoo also Terminalia spp. in India (Neil 1990); Casuarina equisetifolia, Pongamia pinnata, M2lia azedarach, Wrightia tinctoria and Cassia siamea (Rai 1990), but Cassia fistula and Acacia auriculiformis are considered indifferent hosts (Ananthia et al 1988); Albizia falcataria, A.lebbek, Acacia spirorbis, Dalbergia spp., Casuarina spp. and Khaya senegalensis are recarrrended in New Caledonia, but Pinus caribaea and Araucaria spp. gave poor results (CI'FT 1991); Acacia acuminata and A.aneura give good results in Western Australia (McKinnell 1990) .

148

1. Coppice regrowth of pure Eucalyptus globulus on stumps planted in1863. No undergrowth despite open stand. Tamil Nadu, India. CSIRO

2. Acacia mearnsii (wattle) in Kenya. Industrial plantation for tannin,charcoal, poles and fuelwood. Close spacing, little undergrowth. CSIRO

148

1. Coppice regrCMth of pure Eucalyptus globulus on sturrps planted in 1863. No undergr<Mth despite open stand. Tamil Nadu, India. CSIRO

2. Acacia mearnsii (wattle) in Kenya. Industrial plantation for tannin, charcoal, poles and fuelwoocl.. Cl ose spacing, little undergr<Mth. CSIRO

4. Pure Terminalia superm (8 years). Although fairly closely grown, the under­gro.-lth has developed. Tene, cote d' Ivoire . Cl'FT

149

3. Mixture of Tarrieta utilis and Khaya sp. (25 years) at Yapo, cote d' Ivoire . Cl'FT

6. Pure Pinus caribaea (22 years) . Regular thinning has allowed the development of a dense undergrowth . Yapo, c6te d' Ivoire . Cl'Fr

150

5 . Pure Maesopsis eminii (19 years) . A vigorous understorey has developed beneath this lightly­crcMrled and open grown stand. Anguededou, c6te d'Ivoire . Cl'Fr

151

7. A young mixture of teak and Terminalia superta (3 years).Tene, Cate d'Ivoire. czez

8. Pure teak (c. 12 years), Navagotha, Sri Lanka. No undergrowth;the fallen leaves are fuel for fires in dry weather. F. Ng

151

7 . A young mixture of teak and Tenninalia superb3. (3 years). Tene, cote d' Ivoire . CI'FT

8. Pure teak (c. 12 years), Navagotha, Sri Lanka. No undergrCMth; the fallen leaves are fuel for fires in dry weather. F. Ng

152

9. Mixture of Teak,SWietenia macrqphylla andArtccarpus heterqphyllus(c. 80 years).

Sundapola, Sri Lanka. F. Ng

10. Mahogany regeneration, which will tend to dominate the speciescomposition of this mixed plantation. Sundapola, Sri Lanka. F.Ng

152

9. Mixture of Teak, SWietenia macrophy lla and Artocarpus heterophyllus (c. 80 years). Sundapola, Sri Lanka. F. Ng

10 . Mahogany regeneration, which will tend to daninate the species canposition of this mixed plantation. Sundapola, Sri Lanka. F.Ng