UNIVERSITI PUTRA MALAYSIA

DEVELOPING THINNING AND PRUNING GUIDELINES FOR ACACIA MANGIUM PLANTATIONS IN PENINSULAR MALAYSIA USING TREE

GROWTH CHARACTERISTICS

BIMAL KESHARI PAUDYAL

FH 1990 8

DEVEWPING 'IHI.NNING AND PRUNlR7 GUIDELINES FCR ACACIA MANGIUM �TIOOS IN

PENINSUIAR MAIAYSIA USING TREE GR<Ml'H ClIARACl'ERISTICS

By

BIMAL KESHARI PAUDYAL

Thesis Su1::mitted in Partial Fulfilment of the Requirements for the Degree of Master of Science

in the Faculty of Forestry Uni versiti Pertanian Malaysia

July 1990

I am highly irrlebted to my najor supervisor Dr. Nik

Muhamad Maj id for his encooragenent and guidance throughout

the sbxly period am in corxluct.ing this research. I am

grateful to my co-supervisor, Mr. Rusli tJbhd. for his advice

and ocmrents. My appreciation � to Dr. Kamis Awang for his

suggestioos and to Dr. Sheikh Ali Abed for his valuable advice

in analysis of the results. I thank. Mr. Awang Noor Ab:lul Ghani

for his help in statistical analysis.

I wish to acknowledge the help given by MuzaImaI Johan,

Salim Ahmad, Ibrahim Etlham, and Zulkifly Ml. Zin during my

field \'m"k. 'l11anks are due to the Forestry Department,

Peninsular Malaysia and also to the Forestry Departments of

Selangor; Pahang and Negeri Sembilan for p:mnission to conduct

the sbrly in their respective forest plantatioos. I take this

opportunity to extend my sincere appreciatioo to Mr. SUhairni

Yussof, the Forest Officer in Kanasul Forest Reserve for his

help. I extend my thanks to Mr. Saad Nyan, Miss Marhayati

Mahat and Mrs. Ncar Azizawati Musa for helping me in cx:mruter

\'m"k. I wish to thank. all those whose names could not be

li�ted here rut who have helped me in one way or another.

ii

I \Olld like to express my sincere gratitude to The

TrililUvan University and Institute of Forestry, Nepal for

granting my stooy leave. I highly �te 'lbe Malaysian

Goverment for providing lIe scbJlarship and Universiti

Pertan.ian Malaysia for financial assistance to cooduct the

experinent.

I �d also like to express my love and thanks to my wife

and three children who have gi veIl me the encouragement and

strength during the oourse of my study in Malaysia. Finally, I

dedicate this thesis to my late parents.

iii

A�

LIST OF TABLES

LIST OF FIGURES

ABS'mAcr

ABSTRAK

I

II LI'I'ERA'lURE

TABLE OF a:N.l'ENl'S

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• • • • • • • • • •• • • •••••• • • • • • • • • • • • •

'Ihinning : Definition and Objective •• • • • • •

Thinning in Forest Management ••• • • • •• • • • • •

Page

ii

vii

x

xi

xiii

1

7

7

9

Aspects of Thinning ••••• • •••••••• • • • • • • • • • • • 11

Physiological Considerations

Mensurational Considerations

Silvicultural Considerations

•••• • • • • • • • • • •

•••••• • ••• • • • •

•••• • •••• • • • • •

11

15

27

Eoonamic Considerations ••• • •••••••••••••• • • • 37

Pruning in Forest Management ••••• • • • • • • • •

Aspects of Pruning •••••••••••••••••• • • • • •

• • • •• • • • •• • • • • Silvicultural Considerations

Econanic Considerations •••••• • • • • • • • •• • • • •

Acacia mangium Willd.

General Description ••

iv

•••••••••••• • •• • • • • •

• •••••••••••••• • • • • •

42

43

43

46

48

48

III

Natural Distrirution am Habitat • • • • • • • •

RESFAR.<li � • • • • • • •• •• •• • • •• ••• •• • •• • • •

Experimental si tes • • • •• • • • • • • • • • • • • • • •

Setul Forest Reserve, Negeri Sembilan • • •

Rantau Panjang Forest Reserve, Batu Arang,

Page

51

53

53

53

SeLangor • • • • • • • • • • • • • • • • • • • • • • • • • • • •• • • • • • • 55

Kemasul Forest Reserve, Pahang . . . . . . . . . . . . 55

Experimental Layout • • • •••• • • • • • • • • • • • • • • • • 56

Growth M3asurements for Developing Thirming GUideline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Pruning Experiment • • • • ••• • • • • ••• • • • • • • • • • 58

Data Collection • • •• •• • •• • •• • • • • • • • • 59

statistical Analysis • • • •• • •• • •• • • • • • • • • •• 60

RESULTS AND DlsaJSSlOO • • • •• • • • •• • • • • • • • • • • 62

Growth M3asurements for Developing Thirming GUideline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Crown Diameter-DBH Approach. . . . . . . . . . . . . . . . . 62

Discussion • • • • • • •• • • • • • • • • •• • ••• •••••••• • •• • 80

Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Basal Area Increment Approach •• • • • • • • • • • • 86

Discussion • ••••• •• • •••••••••••• ••••• ••• • • •• • 92

Conclusion • • • • • • • • • • • • •• • • • • ••• • • • • • • • • • • • • • 93

Growth Parameters Approach • • • • • • • • • • • • • • • 94

M3an Height • • • • • • • •• • • • • • • • • ••••• • • • •• • • 94

Diameter • • • • • • • • • • • • • • • • • •• •• • • • • • •• • •• • • • • 102

v

stem Form ............. . ..................

Height to Live Crown ... . ..................

Crown Length and crown Ratio ..........

Basal Area Per Hectare ..................

Disc'Ussion .......................... . ......

Conclusion ............. . ................ . . .

Pruning Exp:riment ........................

Discussion ................. . ............ . . .

Conclusion • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Taper Assessment ..........................

Discussion • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Conclusion • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

v SUMMARY AND �ATIONS ...................

Thinning

Pruning

.... . ............................

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Recarmendations ......... . . . ...............

BIBLI(X;RAPHY · ..................................... .

APPENDIX · ..................................... .

VITA · .................................... '" .

vi

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Table

1

2

3

4

5

6

7

8

9

1 0

1 1

1 2

1 3

1 4

1 5

1 6

1 7

18

List of Tables

Calculated Crown Diameters , Crown Area and GSI in Relation to DBH, Setul • • • • • • •••••• • ••••••

Basal Area and Number of Trees in Relation to DBH, 8etul •• •• ••• • • •• • • • ••• • • • • • • • • • • • • • • •••

Calculated Crown Diameters , crown Area GSI in Relation to DBH, Rantau Panjang

and ..• ......

Basal Area and Number of Trees in Relation to DBH, Rantau Panjang • • • • • •• • • • • • • • • • • • • • • ••••

Calculated Crown Diameters , crown Area and GSI in Relation to DBH, Kemasul • •• • • • • •• ••• ••••

Basal Area and Number of Trees in Relation to DBH , Kemasul ••• • • • • • • • •• • • • • • • • • • • • • • • • • ••••

Basal Area Increment, 8etul . . . ...... . . . . . . . . . . .

Basal Area Increment, Rantau Panj ang •••••••••••

Basal Area Increment, Kemasul • • • • •••• • • • • ••••••

Mean Height, 8etul • •••• • • •• • • •• • • • • •• • • •• • • • ••• •

Mean Height, Rantau Panjang •• • • •• • • •• •••••••••••

Mean Height, Kemasul • • • •• • • •••••••••••••• •• • • • • •

Height Increment, Setul ••••••• •• • • •• • • • • •• • • • ••••

Height Increment, Rantau Panjang • • • • • •• • • •• •• • • • •

Height Increment , Kemasul • •••••••••• • • • • • • • • • • •• •

Mean Annual Increment Height MAl (m/annum) Between Sites

Mean Annual Increment Height MAl (m/annum) Within Sites

• • • • • • •• • • • • •••

••• •• • • • •••• • • • •

Mean Diameter , Setul • • • • •••••• ••••••• • • • ••••• •• •

vii

Page

69

70

70

71

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72

87

90

92

96

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97

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99

1 00

1 01

1 04

1 9

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

Mean Diameter, Rantau Panjang •••••• • • • •• • • • • • • • •

Mean Diameter, Kemasul ..........................

DBH Increment, Setul • • • • • • • • • • • •• • • • • •• • • • • • • • • • •

DBH Increment, Rantau Panjang •• • • • • • • • • • • • • • • • • • •

DBH Increment, Kemasul • • • • • • • • • • • • • • • • • • • ••• • • • • •

Mean Armual Increment DElI MAl (an/annum) Between Sites

Mean Armual Increment DBH MAl (an/annum) Within Sites

• • • •• • • • • • • • •• • • •

• •• • • •• • • •• • • • •• • • •

Diameter Distribution, Setul • • • • • • • • • •• •• ••• • ••• •

Diameter Distrihltion, Rantau Panjang • • • • • •• • • • • •

Diameter Distribution, Kemasul • • • • • • • • • • • • • • • • • • •

Crown Length and Crown Ratio, Setul • • • • • •• •• • • • •

Crown Length and Crown Ratio, Rantau Panjang . . . .

Crown Length and Crown Ratio, Kemasul ....•.. .- . . .

aa,sa.l .A:rea Per Hectare • • • • • • • • • • • • • • • • • • • • • • • • • • •

Pruning Treabnents, Setul • •• •• • • • • •• ••• • •• • • • • • •

Pruning Treabnents, Rantau Panjang •.............

Pruning Treabnents, Kemasul ....• ....• ...........

Taper Study, Setul •• • • ••••••••••••••••••• •••• •• •

Taper Study, Rantau Panjang • • • • • • • ••••• • •• •• • • •• •

Taper Study, Kemasul ..................... . ......

Taper Ratio, Setul • •• • •• • • • • • • •• • •••••••• • • •• • ••• •

Taper Ratio, Rantau Panjang • • • • • • •• • • • • • • •• ••• • • •

Taper Ratio, Kemasul • • • • • • • • •• ••••••• • • • •• • • • •• ••

viii

Page

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1 05

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1 09

1 1 0

1 22

1 22

1 22

1 25

1 33

1 34

1 35

1 40

1 41

1 42

1 42

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42 Physical and Chemical Properties of Soils ,

Page

Setul • • • • • • • • • • • • • • • • • • • • • • • • • • ••••••• • • • • • • • • • • • 1 70

43 Physical and Chemical Properties of Soils, Rantau Panjang • • • • • • • • • • •••• • ••••• • ••• • • • • •• • • • • • 1 71

44 Physical and Chemical Properties of Soils, Kemasul • • • • • • • • • • • • • • • • • • • • • • • • • • •• • •• • • • • • • • • • • • 1 72

45 Age - Plot Distribution On the Three Sites • • • • • • • • 1 73

ix

List of Figures

Figure

1 Map of Peninsular Malaysia Showing the

Page

Experimental Sites • • • • •• • • • • • • •• • • • • • • • • • • • • • • 54

2

3

4

5

7

8

9

1 0

11

Crown Diameter-DBH Relationship, Setul ••• ••••••

Crown Diameter-DBH Relationship, Rantau Panjang

Crown Diameter-DBH Relationship, Kemasul ••••••

Number of Trees Per Hectare at a Given Disengagement Level and DBH , Setul • • ••••••••••

Number of Trees Per Hectare at a Given Disengagement Level and DBH , Rantau Panjang •••

Number of Trees Per Hectare at a Given Disengagement Level and DBH, Kemasul •• •• • • • • • •

Growing Space Index (GSI ) , Setul • • •• •• • • • • • • ••

Growing Space Index , Rantau Panj ang •• • • • • • • • •

Growing Space Index , Kemasul • • • • • • • • • • • • • • • • •

Age-Basal Area Increment Relationship, Setul • • • •

66

67

68

73

74

75

77

78

79

88

1 2 Age-Basal Area Increment Relationship, Rantau Panjang 89

1 3

1 4

1 5

1 6

1 7

1 8

1 9

20

21

Age-Basal Area Increment Relationship, Kemasul •

Age-Height Relationship • • • • • • •• • • •• • • •• • • • • • • •

Age-DBH Relationship • • • •• • • • • •• • • •• • • • • • •• ••• •

Height-DBH Relationship •• • • • • • • • • • • •• • • • • , • • • • •

Height-HID Ratio Relationship ••• • • • • •• • • • • • •••

Age-HID Ratio Relationship • • • • ••• • • ••• • • • • • • • •

Age-Height to Live Crown Relationship •• •• • •• ••

Age-Crown Length Relationship • • • • •• •• • • • • • • • • •

Age-Basal Area Relationship ••• ••• • • • • • • • • • ••••

x

91

95

103

1 1 3

1 1 6

1 1 7

1 1 8

120

1 24

Abstract of thesis subnitted to the Senate of Universiti Pertanian Malaysia in {Brtial fulfilnelt of the requirements for the degree of Ma.ster of Science.

DEVEr:Dp:m; 'l'HINN1m AND l"RtlNnG WIIELINES

Supervisor

Faculty

F(R N:ACIA MAN3IUM PIANl'ATIOOS m PENINSULAR MALAYSIA m:m; 'mEE

GRaflH C1IARACl'.mISTICS

By

BIMAL KESHARI PAUDYAL July 1990

: Associate Prof . Dr. Nik Muhamad Maj ide

: Forestry

Peninsular Malaysia is expected to face a tiIrlOOr deficit

before the end. of the century. '!he �tory Forest

Plantation Project now undertaken as a raoodial measure for

this imperrling crisis needs research in plantation management

p:u-ticularly on silvicultural practices such as thinning and

pruning. 'lhinning needs prinary attention in plantation

forestry if the management objective is sawlog production. The

present study focusses ma.inly on the determination of

reasonable age for first thinning in Acacia ma.ngium plantation

in Peninsular Malaysia. In addition to the preliminary thinning

study, pruning trials and evaluation of growth pattern of

Acacia ma.ngium in different aged stands and on different sites

were also conducted. 'lbree sites, that is, Kemasul in

xi

Pahang, Setul in Negeri Sembilan and Rantau Panjang in Selangor

were chosen for the study. '!he rea.sooable age for first

thinning was determined on the basis of basal area grCMth.

Preliminary thinning 9\1:1 del j ne was preparerl baserl on crown

d.iaIteter and diaIooter at breast height relationship. A

raOOaniserl canp1ete block design \'as used to ascertain pruning

treatment effects on d.iaIteter growth and also on tapering of

stem. Tapering of stem was determined by taking diameter

neasurements at different heights along the stem.

'!he results indicaterl that first thirming is to be

carrierl out at about 5 years of age. GrCMth parameters study

showed similar growth rattern 00 all three sites with higher

grCMth in Setul than the other two sites. r.Ihe pruning study

showed significant diameter loss by above 40 percent crown

renoval . A reduction of 1 an DBH in every 1 m in height was

found for taper study with all pruning treatnalts. r.Ihe study

has significant implications pertaining to the diaIooter size

and knot-free quality timber. Ibwever, as the experine1t

lasterl for only one year t further growth infannation over a

100ger pericxi naerls to b3 recorded far llDt"e cxncrete results.

xii

Abstrak tesis yang dikemukakan ke};Eda Senat Universiti Pertanian Malaysia sel::agai nanenuhi sebahagian daripada syarat­syarat untuk Ij azah Master Sains.

PEMBENlUKAN GARISPANOOAN � DAN

Penye1ia

Fakulti

PEMAtG<ASAN � N!Ar:JA MMG1JM DI SEMENANJUNG MALAYSIA MFNnJNAI<AN

CIRI 'lUMBEBARAN roI<OK

01eh

BIMAL I<PSWU PAUDYAL Julai 1990

: Prof. Madya Dr. Nik Muhamad Maj id

Perhutanan

Semenanjung Malaysia dijangka JreIlgalami kekurangan ba1ak

sebe1um akhir al:ad ini . Projek ladang hutan dija1ankan

sebagai tindakan yang rerkesan untuk JreIlgatasi krisis tersebut.

Wa1au bagairranapun kaj ian dalam pengurusan 1adang hutan

terutana dalarn as� si1vikultur seperti penjarangan dan

pernangkasan per1u dija1ankan. Penjarangan narer1ukan penekanan

di dalarn per1adangan hutan jika objektif pengurusan

adalah untuk penge1uaran papan gergaj i. Kaj ian yang telah

dijalankan kebanyakannya tertumpu dalam penentuan umur yang

yang dijangka sesuai bagi melakukan penjarangan yang pertama

untuk ladang Acacia mangium pada kawasan ladang yang rerbeza

umur dan rerbeza kawasan juga telah dijalankan. Tiga kawasan

xiii

yang telah dipilih untuk kaj ian ini ialah di Kemasul, Pahang;

Setul, Negeri Sembilan; dan Rantau Panjang, Selangor . Umur

yang sesuai untuk penj arangan pertama telah didapati berasaskan

kepada tumbesaran ladang tersebut. Garispanduan penj arangan

telah dibuat berdasarkan kepada perkaitan di antara diameter

perepang dan diameter p:>kok pada prras dada. Kaedah rekabentuk

blok rawak penuh telah diguna di dalam kaj ian kesan rawatan

penBrlgkasan terhadap tumbesaran diameter dan juga pe.ngukuran

terhadap bentuk batang. Bentuk batang ditentukan dengan

rrengambil ukuran diameter pada ketinggian yang berbeza di

sepanjang batang {X)kok.

Keputusan kaj ian nendapati pmj arangan pertama. hendaklah

dibuat apabila {X)kok berumur 5 tahun. Kaj ian prrameter

tumbesaran nenunjukkan b:m.tuk tumbesaran yang sarna p:1da ketiga

kawasan kaj ian dengan kawasan Setul rnenunj ukkan kadar

tumbesaran yang tertinggi . Kaj ian penBrlgkasan memberi kesan

yang signifikan terhadap pe.ngurangan diameter batang setelah

lebih darip:1da 40 peratus pemangkasan silara dij alankan.

Pengurangan 1 ern diameter p:1da p:1ras dada pada setiap 1 meter

ketinggian telah didap:1ti dalam kaj ian b:m.tuk batang dengan

rawatan pernangkasan yang sarna . Kaj ian nenunj ukkan kesan yang

signifikan terhadap perkaitan antara saiz diameter dan

kualiti batang daripada kesan pemangkasan. Walau bagairPanapm

kaj ian yang hanya setahun tidak nencukupi dan maklunat

xiv

tumbesaran p3da jangkamasa yang lebih pmjang diperlukan untuk

nenberikan kepltusan yang lebih tep:lt.

xv

Plantation forestry in the tropics evolved as a result

of deforestation. The rate of tropical deforestation

has been estircated at 6 . 2 to 25 million hectares a.IU1ually

(Sedjo and Clawson, 1 983; Nambiar, 1 984; Wong, 1 984) .

Evans ( 1 986 ) gave an estircate of 1 1 . 3 million hectares/year,

representing about one percent of the total area of the

tropical forests. According to Spears ( 1 979) , the reIllClining

tropical forest will disappear in 60 to 80 years. Pandey

( 1 983 ) estimated that during the five year period. ( 1 976-80 ) ,

plantations were established in the tropics at rate of 0 . 9

million hectares/year, nearly 1 3 tines less than the rate of

deforestation.

Malaysia is a tropical country and is a federation of 1 3

states located at the heart of southeastern end of Continental

Asia. It cx:mprises Peninsular Malaysia, Sabah am Sarawak.

Peninsular Malaysia has an area of 1 3. 2 million hectares , Sa.b3.h

7. 6 million hectares , and Sarawak 1 2. 4 million hectares

(Salleh, 1 983 ) • Forest covers an area of about 6 . 1 million

hectares in Peninsular Malaysia, 4 . 66 million hectares in

Sabah, and 9 . 42 million hectares in Sarawak, giving a total of

20. 1 8 million hectares for the entire oountry (Leng, 1 987 ) .

1

2

Malaysia is by far the major supplier of tropical logs to

Japan, South Korea and Taiwan. For tropical sawn timber,

Malaysia remains the leading supplier to roost of the European

Econanic Carmunity (EEC) countries and Australia (Baharuddin,

1986) • The export of sawlogs and total timber products during

the period of January-April, 1988 aIOOl.Ulted to 5,966,864 and

7,658,914 cubic metres, respectively. The value for total

timber product export was MR$2,066,660,350 thus contributing a

considerable revenue to the national econany (Malaysian Timber

Industry Board, 1988).

The scenario is probably going to change. Peninsular

Malaysia is expected to experience a shortage in timber supply

to neet dcmestic consumption by mid 1990's. Freezaillah (1982)

indicated that with the current trend of forest exploitation

and the rising demand of forest products, Peninsular Malaysia

is going to face timber deficit well before the turn of the

century. With increasing p:>pulation and standard of living, the

gap between demand and production of timber is expected to

widen to about 2.55 million cubic metres (in round log

eqivalent) by the year 2001 (Yong, 1984). A similar situation

applies to sabah. According to Yusuf (1985) annual production

is expected to decline between 3.6 and 4.6 million cubic metres

by 1990, fran 11.9 million cubic metres during the 1975-1980

period. As of 1987, timber production in Malaysia was 29.5

cubic-rnetres: 12.2 cubic netres in Sarawak, 9.4 cubic metres

3

in Sabah and, 7.9 cubic netres in Peninsular Malaysia (Leng,

1987) • '!his oould l:.e increased to 73 . 3 cubic netres if all

productive indigenous forests were converted to plantations of

fast-growing species (Yusuf , 1982) • HcMever , this is an

estimate and it does not imply that all indigenous forests

should l:.e converted to plantations as the indigenous forests

are capable of producing higher quality timber which is

generally not the case with the fast-growing plantations.

It is apparent that the rising demand and declining

production pattern of timber , even for danestic consumption

purposes , has thrown Malaysia into a paradoxial situation of

becaning an importer fran a fOsition of leading prcxlucer of

tropical hardwoods . One of the solutions seems to l:.e the

establishment of fast-growing forest plantations. The increase

in demand for forest products , low producti vi ty and poor

regeneration of natural forests are sane of the reasons for

large-scale forest plantation establishment in Malaysia

(Sheikh, 1982) • Large-scale plantation forestry started in

1974 after investigations by the Forestry Department and

UNDP/FAO on the feasibility of establishing long-fibred

coniferous plantation species for danestic pulp and paper

supply (Nik and Karnaruzaman, 1986) • Instead of pilp and paper

mill establishment, a new fOlicy was adopted to incorporate a

project to canpensate the shortfall l:.etween projected supply

and demand of wood for danestic consumption purposes. Thus , the

4

Ccmpensatory Forest Plantatien Project (CFPP) is the recently

urrlertaken project with the cbjective to produce nulti-p..1qOSe

logs for sawn timber, veneer am plywood in addition to

pulp;«XXl.

'Ihls project involves the establishment of about 1 88,200

hectares of fast-qrowing hard.\«xxl plantation species within 1 5

years in Peninsular Malaysia am is expected to incur a

developrent cost of MR$406.52 million (Yoo.g, 1 984) . '!he

rationale behind this project is to grow timber species 00.

short rotation of about 1 5 years to yield general utility

timber with growth rate of about 1 7. 6 cubic rcetres per hectare

per year. SUch plantations are expected to prcxluce a net yield

of 1 4.1 cubic rcetres per hectare per year or 21 1 .7 cubic rcetres

en a rotation of 1 5 years. 'Ihls project was officially launche1

at the ern of 1 982.

For Peninsular Malaysia these plantations have 1::een

establishe1 at Setul in Negeri Sanbilan, Ulu Sedili in Johore,

Kemasul in Pahang am Rantau Panjang Forest Reserve in

Selanger. '!he plantation targets for the Fourth ( 1 981 -85 ) ,

Fifth ( 1 986-90 ) am Sixth ( 1 991 -95 ) Malaysian Plans are

8 , 000 ,74 , 000 and 1 06,200 hectares, tespect! vely. By mid-1 989 ,

about 40; 000 ha have been established. '!he three najor fast­

growing species plante1 are Qrelina arborea Rex. (Yemane),

Acacia mangium Willd. am Paraserianthes falca.taria (BaW).

'Ihese three species are especially chosen because of their

5

faster growth rate and adaptability to p:x::>r soil oonditions and

adverse si tes . Acacia mangium seems to be the Irost pranising

arrong these three species .

If the plantation project is for obtaining multi-purpose

logs for sawn timber, veneer, plywood and pul�, thinning

and pruning seem to be an essential p:rrt of forest management.

'Ihus, management strategy has to be directed towards proper and

timely silvicultural treatments . In this oontext, thinning and

pruning play very important roles in management decision.

However, field guidelines for thinning in Acacia mangium

plantation in Malaysia are not available (National Research

Council, 1983; Johari and Yuan, 1986). The canpensatory Forest

Plantation Project dictates that thinning is to be carried out

at year 8. This is j ust an interim guideline which is not b:ised

on any research findings. Similar case applies to pruning.

With this mckground and lack of sound scientific

information on silvicultural operations of these plantations,

rreasurements of p:rrameters for developing thinning guidelines

and pruning trials were oonducted in three states, that is,

Pahang, Selangor and Negeri Sembilan in Peninsular Malaysia.

The rrain obj ecti ve of this study is to determine the

reasonable age for first thinning in Acacia mangium plantation.

6

The specific objectives of the sttdy are:

i. To prep:lre a preliminary thinning guideline for

Acacia nangium plantatioo in Peninsular Malaysia

based on the growth characteristics of the stands.

ii. To det.el:m1.m growth performance of Acacia mangium

urder different pruning treatments.

Growth nvaasurenents for developing thinning guideline aIX1

pruning experimant started in April aIX1 July, 1 987 ,

respectively. The field investigation lasted far ale year.

ClIAPI'ER 2

LITERA'lURE REVIE.W

In plantation forestry of the tropics, relatively little

is known alxnlt thinning practice and regimes. This is nainly

because of rapid expansion of plantation progranmes in this

region and insufficient time to gain adequate experience. The

information available is scanty for mahy of the species now

widely planted in this region, especially in the lowland

tropics. For tropical pines , substantial information is

available but not so for the hardwoods. Thus, a najor portion

of this literature review focuses on thinning relating to

temperate conifers. However , every effort has been nade to

incorporate thirming WJrks on tropical plantations, especially

the fast-growing hardWClOds that are relevant to the present

study. Yet, because of the few work done and even less

reported, and the unavailability of the reported ones,

information about thirming in tropical hardwood plantations is

virtually non-existent in Malaysia.

Thinning: Definition am Objective

Thinning is a process which artificially reduces the

ntnnber of trees growing in a stand. It can be defined as

7

8

a felling operation made in a starrl at any time between

establishnent am the initiaticn of a :regeneration cutting or

clearfelling in which the trees raooved are the same species as

the trees favourErl (Winters, 1 977) • Several reasons are to be

accountErl for carrying out thinning as a tending oI;'&'ation.

Silvicu1turally, the primary objective of thinning is to reduce

the number of trees growing on a site so that those renaining

have m:re growing space far crown &veloptent with less root

CXl:II)?etition thus creating a favourable envi.rament for stern

diaIreter increroont (Baker, 1 934; Matthews, 1 963; Day, 1 966 ;

James, 1 979 and Evans, 1 982) .

In specifying nanagenent objectives, generally �

different approaches are considerErl: either to maximize total

volune production in a starn or to maximize growth of

individual trees, far example, for sawn timber (Sldth, 1 962;

Evans, 1 982 ) • As forest crops are thirmed roth to produce an

intennediate financial yield and to stimulate growth of

remaining trees (Matthews, 1 963 ; Ford, 1 984) a canpranise has

to be made and a stand is thinned without causing significant

loss :in total yield. Such a thinning I as awliErl in Qleenslarrl,

Australia is tennErl as marginal intensity thinning based on

the concept of limiting msal area. Limiting l:B.sal area ( 30 sq.

m./ba for Pinus carib3.ea) is the mininnJn starrl basal area that

will still yield maximum basal area incre.naent with no loss in

total yield. 'lbinning at marginal intensity aims to maintain

9

this minimum stand ba.sal area (Bradley, 1963; Evans, 1982 ) •

However, the minimum stand ba.sal area required to be left after

thinning depends on site conditions and growth of the species.

particularly for the production of sawlogs with certain

diameter size objectives, the concept of maxirrrum volume

production has to re discarded in favour of individual tree

growth. 'Ib achieve maxirrrum growth of individual trees , ba.sal

area should be kept relow the residual area required by

narginal intensity thinning.

'1hlnning in Forest Manageuent

Forest management has incorp::lrated thinning for a long

time and thinning decision is ba.sed on management objectives.

'!binning policy, however, has always been guided by

sil vicul ture and economics although the ba.sis of thinning to

change physiological phenarena such as providing better

environment for root and crown developnent has the major role

to play. Economics plays a vital role especially in oamrnercial

thinnings. In many cases, stands are oot thinned or thinning is

delayed due to econanic reasons although silviculturally stands

should have reen thinned. Evans ( 1 982 ) stated that the

increasing cost of thinning has pranpted many forest managers

not to do any thinning. However , if the primary objective is

to produce sawlogs ,

the value thinning

that is , where size of the stem detennines

is then econanically justified.