nzffa electronic handbook series · best practice with farm forestry timber species no. 3: redwoods...

NZFFA Electronic Handbook Series

Best Practice with Farm Forestry Timber Species

No. 3: REDWOODS

Ian Nicholas (Editor)

NZFFA Electronic Handbook Series

1

FOREWORD

In producing this publication, reasonable care has been taken to ensure that all statements represent the best informationavailable. However the contents are not intended to be a substitute for specific specialist advice on any matter and should

not be relied on for that purpose.

NZFFA and SCION and its employees shall not be liable on any ground for any loss, damage, or liability incurred as a director indirect result of any reliance by any person upon information contained or opinions expressed in this work.

DISCLAIMER

2

Following the success of the publication Blackwood - a handbook for growers and end users, several New Zealand FarmForestry Association (NZFFA) action groups expressed an interest in the production of handbooks for other tree species.

This publication is the third in a series designed to present up-to-date information about cypresses, eucalypts, redwoods andblackwood. Support for the project has been received from the MAF Sustainable Farming Fund with additional assistance fromNZFFA, Scion (FRST new species CO4X0304), Proseed NZ Ltd, Environment Bay of Plenty, Horizons Regional Council,

Rarefind Timbers, the Plantation Management Cooperative and relevant NZFFA action groups.

It was agreed that an electronic format would be the most appropriate method for publication. The advantage of this formatis the potential for relevant details to be updated as new research results come to hand. Management techniques for many tree

species are still being evaluated and recommendations are likely to be modified over the space of a few years.

These handbooks have been independently reviewed and are offered as a summary of the best available knowledge about treespecies and their suitability for forestry, shelter, and amenity planting. Information gathered from farm foresters and research

scientists has been collated and presented under specific topic headings for ease of reference.

Visit the NZ Farm Forestry Association website (www.nzffa.org.nz) for the mostup-to-date information available.

In 2002 Wade Cornell published “The New Zealand Redwood Growers Handbook” as part of a promotional tour for a seriesof workshops. This provides an excellent overview of redwood as seen by the author at that time. A comprehensive summaryof redwoods in New Zealand was also published by FRI in 1993 as No. 13 in its Bulletin No 124 series. Since these publicationsthere has been an increasing amount of activity at both the research and operational levels on redwood. This new handbookdoes not attempt to repeat these previous publications but endeavours to capture the new information for farm foresters and

place it in a form where it can be updated as required.

For ease of reading, the colloquial name of individual species has been used throughout the handbook in

preference to full scientific names:

Redwood = Sequoia sempervirens [D. Don] EndlGiant sequoia = Sequoiadendron giganteum (Lindley) J. Buchholz

Because most of the current forestry activities are based on redwood, this handbook concentrates on redwood, rather than giantsequoia.

Throughout the handbook text in boxes is used to highlight important information relevant to the chapter. At the end of eachchapter, key points are used to summarise the information, along with any suggested reading. A full reference list and glossary

are provided at the end of the handbook.

Grateful acknowledgement is given to the contributors who made this handbook possible, the reviewers for valuable additionalinput, Vivienne McLean and Margaret Richardson for editing contributions, Teresa McConchie for final formatting and Scionfor web site preparation. In particular the assistance of NZ Forestry Ltd in allowing the use of website material is also appreciated.

Comments on this handbook and suggestions for revision should be sent to the NZFFA Sequoia Group(see the NZFFA web site for contact details).

Ian Nicholas

4 Visit www.nzffa.org.nz for the most up-to-date information available.

CHAPTER 1 -

CHAPTER 2 -

CHAPTER 3 -

CHAPTER 4 -

CHAPTER 5 -

CHAPTER 6 -

CHAPTER 7 -

CHAPTER 8 -

CHAPTER 9 -

CHAPTER 10 -

CHAPTER 11 -

CHAPTER 12 -

CHAPTER 13 -

1

13

19

22

23

3

30

32

39

45

47

51

53

55

TABLE OF CONTENTS

INTRODUCTION

TIMBER PROPERTIES AND MARKET

SITE SELECTION

HEALTH

SEED SOURCE AND BREEDING

ESTABLISHMENT

PRUNING AND THINNING

GROWTH MODEL AND REGIME EXAMPLE

ECONOMIC ANALYSIS

UTILISATION

SUMMARY

REFERENCES AND WEB LINKS

GLOSSARY


CHAPTER 1 - INTRODUCTION

Key points

Redwood is of increasing interest to the New Zealand forest industry as a potential plantation tree.

There is a long history of planting in New Zealand with mixed success.

Redwood offers opportunity for export, especially in the Californian market.

Giant sequoia is less well known but also has several positive features, warranting more evaluation.

CHAPTER 2 - TIMBER PROPERTIES AND MARKET

Key Points

There is considerable tree-to-tree variation in redwood wood properties, in both density and durability.

Redwood has a strong market niche in California, which has moved from predominantly old crop to younger,second-growth logs.

New Zealand-grown redwood has an opportunity to market logs in California in addition to New Zealand.

Clones or seedlots with acceptable durability ratings will be a key to securing market acceptance in bothNew Zealand and California.

CHAPTER 3 - SITE SELECTION

Key Points

Redwood is very site sensitive.

Avoid severe out-of-season frost sites.

Avoid exposed locations.

Avoid windy coastal situations.

Redwood does best in moist valley bottom locations.

Giant sequoia can tolerate cold, dry sites, but can remain in prolonged check after planting.

CHAPTER 4 - HEALTH

Key Points

Redwood is generally a healthy species in New Zealand situations.

Dead branches and extensive bark injuries can offer entry points to borers.

Possums can cause some leader damage on young trees.

TABLE OF CONTENTS

Visit www.nzffa.org.nz for the most up-to-date information available. 5

CHAPTER 5 - SEED SOURCE AND BREEDING

Key Points

The Kuser collection is not a true range-wide provenance sample of seed sources.

The Kuser collection has provided material for a range of trials on 64 sites throughout New Zealand from 2002-2006.

Limited redwood provenance evaluation has been carried out, on one site, established in 1981.

Giant sequoia provenance trials were established on five sites in 1977-1978.

Progeny from the Long Mile Grove redwoods and Raincliff giant sequoia trees perform poorly compared with otherprovenance seedlots.

Future selections of redwood and giant sequoia should be based on a wide genetic base and take account of woodproperties.

CHAPTER 6 - ESTABLISHMENT

Key Points

Correct siting, robust seedlings and weed control will ensure successful establishment.

Redwood requires weed control for at least 18 months, and possibly fertiliser, to promote early growth.

Giant sequoia is a slow starter, and will often require prolonged weed control.

CHAPTER 7 - PRUNING AND THINNING

Key Points

Redwood requires pruning to produce clearwood.

Over-pruning can result in epicormic shoots.

Pruning in autumn reduces epicormic sprouting.

CHAPTER 8 - GROWTH MODEL AND REGIME EXAMPLE

Key Points

Well-sited redwood grows very well with high volume production figures.

A regime is suggested, with 800 stems/ha, up to 3 pruning lifts, one thinning to final crop stocking of 350 stems/hafor a rotation length of 35 years.

CHAPTER 9 - ECONOMIC ANALYSIS

Key Points

Analysis of redwood forestry in New Zealand shows a positive return (based on Californian prices), with an estimatedInternal Rate of Return (IRR) of 9.3%.

Seek professional input before making large investment in redwood forestry

Insufficient information is available to analyse giant sequoia forestry

TABLE OF CONTENTS


TABLE OF CONTENTS

CHAPTER 10 - UTILISATION

Key Points

New Zealand-grown redwood has been successfully utilised in New Zealand.

A sawing study currently in progress will extend knowledge on utilisation of managed redwood.

CHAPTER 11 - SUMMARY

Key Points

New Zealand redwood is a developing industry in New Zealand.

Experience suggests that redwood plantations can be well grown and utilised in New Zealand.

Little information exists to evaluate the potential of giant sequoia for plantation forestry.

As new information is obtained, key results will be updated through the Farm Forestry Association via this handbook.

CHAPTER 12 - REFERENCES AND WEB LINKS

CHAPTER 13 - GLOSSARY

7

CHAPTER 1 - INTRODUCTION

Visit www.nzffa.org.nz for the most up-to-date information available.

Ian Brown (NZFFA), Charlie Low and Ian Nicholas (Scion),Rob Webster (NZ Forestry)

The Redwoods

“Here, sown by the Creator’s handIn serried ranks, the Redwoods stand:No other clime is honored so,No other lands their glory know.

The greatest of Earth’s living forms,Tall conquerors that laugh at storms;Their challenge still unanswered rings,Through fifty centuries of kings.

The nations that with them were young,Rich empires, with their forts far-flung,Lie buried now - their splendour gone:But these proud monarchs still live on.

So shall they live, when ends our days,When our crude citadels decay;For brief the years allotted man,But infinite perennials’ span.

This is their temple, vaulted high,And here, we pause with reverent eye,With silent tongue and awestruck soul;For here we sense life’s proper goal:

To be like these, straight, true and fine,to make our world like theirs, a shrine;Sink down, Oh, traveller, on your knees,God stands before you in these trees.”

Joseph B Strauss

Redwood in California

Redwood has iconic status in California,similar to that of Kauri in New Zealand.Redwood is a long-lived tree that can liveover 2,000 years, and the reputation ofgiant sequoia being the largest trees inthe world enhances the redwood image.

The image of redwood is reflected in thepoem by engineer Joseph Strauss, whoalso designed the Golden Gate Bridge.


HISTORY IN NEW ZEALAND

Early Planting

By the mid-19th century, the plant hunters hadmoved into the American West, collecting seedsfrom the spectacular forests on the Pacificseaboard. Redwood seeds were among thoseof many forest tree species that were introducedto the young colony from the 1860s. They wereplanted in private estates and gardens, and bycivic authorities. The legacy of these earlyplantings is a scattering of trees of impressivesize. The early plantings were no doubt promptedby nostalgia for the familiar, the pursuit ofnovelty and prestige, and a need for shelter onexposed farm sites.

By 1900, Government recognised the need forafforestation to substitute for declining native-timber resources, and a number of forestnurseries were established. Among tree species

redwood was a contender – the leadingcontenders included Corsican pine and larch,but certainly not radiata pine at the time.Extensive areas were planted in redwood inthe Rotorua district, but most failed to establishsatisfactorily. The reasons are likely to haveincluded poor site selection (too cold), poorsite preparation and lack of weed control, andan absence of suitable mycorrhizae. The treeswhich did survive and eventually form theLong Mile Redwood Grove, New Zealand’smost admired exotic forest stand, nearlysuccumbed to frosts. They struggled for severalyears until they were unexpectedly rescuedwhen subsequently interplanted in larch, whichgave them shelter.

Figure 1: The redwood grove, Whakarewarewa Forest, Rotorua

9Visit www.nzffa.org.nz for the most up-to-date information available.

Between 1920 and the 1940s furtherplantations were made by both governmentagencies and private companies, some run byentrepreneurs of dubious reputate. Except ina few small pockets, they all failed to getaway, again through ignorance of siterequirements and of establishment needs.

For some years after that time, redwoodlanguished in the planting figures, dogged bya reputation for being difficult to establish.There were also concerns about timber quality,when the local product was compared withthe timber still under harvest from the oldgrowth forests in California. There was nocorporate interest, and a lack of researchfunding. A number of farm foresters kept thefaith, establishing small plantations, more foramenity interest than in the hope of acommercial return. With attention to siteselection and weed control, most of thesehave thrived, and grown into impressivestands. One of the best of these stands is onthe Brann’s property in the Bay of Plenty.

The redwood revival

The recent renewal of interest in redwood canbe clearly dated to a Farm Forestry conferencein 1995. While the group sheltered under theBrann’s redwood stand, Bill Libby presenteda case for reconsidering the place of redwoodin New Zealand. As Professor of Forestry atthe University of California, Bill Libby hasstudied and researched redwood for manyyears, and had a deep knowledge of the NewZealand scene. From his observations of farmforestry plantations he was convinced thatwith proper site selection and managementredwood could be easily established and growwell in New Zealand, and expressed the viewthat our conditions are probably better suitedto growing redwood than anywhere else.Moreover, the quality of locally grown timberis likely to match that of the second growthcurrently harvested in California, and thereforelikely to attract a high price in a market wheredemand is high and supply is dwindling.

His comments fell on fertile ground, and whena decision was made in 1999 to form a special-interest group, the Sequoia Group within FarmForestry, there was an enthusiastic response.

We decided to start with a simple trial, inwhich members would be involved. As noresearch funding was available, it had to beself-funding. The aim of the trial was toexamine the growth of a set of clones acrossa range of New Zealand sites. In 1993, BillLibby had introduced some clonal materialfrom the Kuser collection in California. Theparent trees were unexceptional, but coveredthe main geographical zone occupied byredwood in California. A selection of cloneswere bulked up at the Fletcher Challengetissue culture laboratory at Te Teko, and madeavailable for the trial. Bill Libby provided aplanting plan. The participants bought thetrees at cost price, planted on their ownproperty, and carried out the silvicultural work.Preliminary results are reported on page 20.

In the absence of research funding, weassumed that this would be the first of a seriesof small scale trials that would be conductedthrough the Sequoia Group. However eventstook a new turn when the Americans arrived.

The big players get involved

In 2000, a group, comprising the owners andchief foresters of the Soper-Wheeler Company,arrived in New Zealand from California to lookat the potential for redwood establishment.Bill Libby was the catalyst, and much of theiritinerary was arranged by members of FarmForestry. They were impressed by our growthrates and timber quality, and keen to be freefrom the entanglement of regulations thatgovern forestry practice in California. Theyreturned, as the New Zealand RedwoodCompany, and have established plantationsin Canterbury, and near Hunterville in theNorth Island. They have an active researchprogram, which includes growth modellingand silvicultural trials. They have introducedseed-orchard and improved clonal materialfrom California, and have selected plus treesin New Zealand for propagation.

Significant plantations are being establishedby local growers, and will expand as newclonal and seed orchard stock becomesavailable. These will be selected for form andgrowth rate, and there is now growingacceptance that selection for wood properties


Figure 2: Giant sequoia, Mariposa grove

is equally important if we are to succeed inthe American market.

Rob Webster and his group, the New ZealandForestry Company, have been active inresearch and establishment.

Bill Libby maintains an active interest, andcontinues to provide support and advice.

Wade Cornell has played a major role inresearch and education, and has pursued adogged campaign promoting the quality ofthe species’ wood.

Redwood is a demanding species, and inNew Zealand we are privileged to have someof the world’s best sites for growing it. Redwoodforestry is on a roll, and has a momentumthat will result in substantial forests. Thesehave the potential to transform much of therural landscape, and provide a strong economicresource. The next challenge is to prepare forthe future markets. This requires us to capturethe genetic variability in redwood, and delivertimber of high and consistent quality.

Its timber has traditionally been regarded asinferior to that of coast redwood but is in factsimilar, and accepted in the Californianmarkets. Trials in California and New Zealandhave shown very respectable growth rates. Itis likely to be more widely planted in the SouthIsland.

Giant sequoia is highly tolerant of gale forcewinds, an advantage worth bearing in mindas we enter a period when extreme weatherevents wil l become more common.

Giant Sequoia

The world’s largest tree has a patchydistribution along the western flanks of theSierra Nevada Range in California. Notsurprisingly, it is well suited to the high countryof the South Island. Giant sequoia wasintroduced in about 1860, and has been plantedmainly as an ornamental species on largeSouth Island estates and parks. Limited trialswere planted on five South Island sites in1977.

M. L

ow, 1

990


Giant sequoia planted by Charles Haines at CampHill between Glenorchy and Paradise, Otago

Figure 3: Notable trees planted in New Zealand

Giant sequoia, Rotorua Boys’ High SchoolNotable tree, Waikato

Notable tree, Waikato

Visit www.nzffa.org.nz for the most up-to-date information available.12

Key Points

Suggested reading:

Redwood is of increasing interest to the New Zealand forest industry asa potential plantation tree.

There is a long history of planting in New Zealand, but with mixed success.

Redwood offers opportunities for export to the Californian market.

Giant sequoia is less well known but also has several positive featureswarranting further evaluation.

Brown 2007

Cornell 2002

Knowles and Miller 1993

Libby 1999

Mortimer and Mortimer 1984

NZ Tree Grower 27 (1) 2007

Poole 2007

Webster 2008

Weston 1957


CHAPTER 2 - TIMBER PROPERTIES and MARKETS

Mark Dean (Ernslaw One), Charlie Low, Russell McKinley and Dave Page (Scion),Rob Webster (NZ Forestry)

The redwood market in California has changeddrastically over the last thirty years. As moreold crop forest has been placed in reserves,increasing volumes of second generationforests are now being logged. There is littlesegregation of logs by grade from naturalforests other than by small end diameter. Mostclear grades come from large old growth logs,which are now in very short supply, with theresult that clear lumber grades have virtuallypriced themselves off the market. This meansthere is considerable potential for pruning inNew Zealand planted forests to produceclearwood. The dimension of logs producedfrom Californian second growth stands issimilar to those of radiata pine logs producedin New Zealand.

The following chart (Figure 4) shows thechange in markets for redwood lumber overthe past three decades. Although cyclical, theoverall trend in total production is relativelystatic. However, the volume available forexport sales or to eastern states of the USA

has steadily diminished. Now, virtually allutilisation is within California, with only smallamounts in other western States.

New Zealand has a small domestic market,mostly because of the lack of New Zealand-grown material rather than lack of demand.Trial shipments of New Zealand material havebeen well received in the Californian market.

New Zealand experience

Redwood timber imported from California hasa good (and well-deserved) reputation forexterior use and for high-quality joinery. Incontrast, New Zealand-grown redwood timberhas shown acceptable performance as exteriorcladding and interior sarking, but its lowdensity, low hardness, and low-to-moderatedurability restrict its range of uses. There hasalso been considerable tree-to-tree variationin some wood characteristics.

Figure 4: Destination of Redwood Lumber 1972 - 2002

0

200

400

600

800

1000

1200

Year

Volu

me

(thou

sand

boa

rd fe

et)

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

Outside 48 States

Eastern States

Rest of West

California


Table 1: Comparison of wood properties of New Zealand-grown redwood and radiata pine(from Knowles and Miller 1993)

* Mean values typifying 50 year old trees

# Mean values typifying 35 year old trees

Property

Density kg/m3

Shrinkage air-dry %

Modulus of rupture (MPa)

Modulus of elasticity (GPa)

Maximum crushing (MPa)

Hardness (kN)

Description

Basic

Air-dry

Green

Volume

Tangential

Radial

Longitudinal

Green

Dry

Green

Dry

Green

Dry

Green

Dry

Redwood*

335

380

910

4.8

3.2

1.5

0.02

56

63

6.4

6.6

24

36

1.8

1.9

Radiata pine#

420

500

955

7.0

4.7

2.2

0.10

40

90

5.8

9.0

16

38

2.5

4.2

Density

Variation in wood density among matureredwood trees is large. A tree evaluated atone New Zealand site was 256 kg/m3 whilethe mean of trees from three other sites were310, 356 and 385 kg/m3. Estimated wooddensity from increment cores of 92 trees fromnine seedlots at age 20 years in the Bay ofPlenty had a mean of 314 but tree-to-treevariation ranged from a minimum of 252kg/m3 to a maximum of 415 kg/m3. In thisassessment tree diameter had a larger bearingon density than seed source, with larger treeslower in density. More testing of differentredwood seedlots is required so selections forconsistent wood properties can be undertaken.

Durability

One of the main market strengths of redwoodis the natural durability of its heartwood (thesapwood is not durable). Trials have beenundertaken to assess the durability of NewZealand-grown redwood (Table 2). Tests byFRI in 1962 placed New Zealand-grownredwood in natural durability Class 3(moderately durable). A second test with woodfrom the same source, some 30 years later,indicated that redwood should be in Class 2(durable). However, with a further testing ofnew material, a third set of stakes was lessdurable than the first and supported the initialclassification of Class 3.


Overall, New Zealand-grown redwood hasshown quite variable durability. Even thoughstakes from 80-year old trees appear to bemore durable on average than the other setstested, the first failures occurred in that groupafter only 2-3 years. Based on the tests doneso far, redwood could show durability variationin situations of moderately high decay hazardor in exposed situations where a long servicelife is required e.g. exposed exterior structuralsituations.

The reasons for the high variability are notclear although this is not unusual in specieswith a Class 3 durability classification.

In a Californian study it was found that decayresistance also varied amongst trees and alsowithin the heartwood of individual trees. Itwas found that decay resistance decreasedfrom outer to inner heartwood.

Table 2: Summary of New Zealand durability tests

* ex 150 mm rusticatedN/A: Not avai lable

3

2

2

2

2

3

3

Class

50

80

80

35

35

N/A

N/A

Approx age ofmaterial (yrs)

Rotorua

Rotorua

Waitarere

Rotorua

Waitarere

Rotorua

Devonport

Locationtested

18-19 mm stakes

20 x 20 mm stakes

20 x 20 mm stakes

20 x 20 mm stakes

20 x 20 mm stakes

Weatherboards*

Weatherboards*

Tested material

1962

1988/1989

1988/1989

2001

2001

1987

1987

Date testsestablished

In low decay hazard situations such asweatherboards, New Zealand-grown redwoodshould meet the requirements of NZS3602:2003 (NZ Standard for Timber andWood-Based Products for Use in Building).The service life of uncoated boards is likelyto be limited by erosion and distortion butcould be improved with well-maintained surfacecoatings.

A series of new tests established in 2007 with70 and 40-year-old South Island material iscurrently being evaluated using above-groundlap-joint samples and in-ground stakes. Thesewill provide more information on redwooddurability. Laboratory testing of redwood cloneshas also identified clonal variation in durability.

Use in Decking

Some New Zealand-grown redwood is too softfor exposed decking. Its low strength meansthat it would need to be either supported byjoists at closer spacing or be thicker thanradiata pine decking. Surface erosion ondecking is likely to be worse than on uncoatedweatherboards and would produce a veryrough surface on lower density boards withinfive years. Its variable durability would alsomake it marginal for use as decking becausea few failures in less than 15 years (theminimum requirement in NZS 3602) could beexpected in exposed situations and in areaswhere there is a higher decay hazard e.g.poorly ventilated or constantly damp areas.

Giant sequoia has a reputation of producingsimilar timber to redwood, although it is


reported to be brittle and requires differentdrying schedules. Commercial production inCalifornia is very small compared to redwoodproduction. New Zealand-grown giant sequoiahas not been fully evaluated.

The US residential deck market is large, 6.5 millionnew decks are constructed each year, with growth of8.1% per year (1991-1999). Redwood was used in12% of US residential decks in 1987 and 11.1% ofdecks in 1998 . The small decline in market share waspossibly due to the higher price for redwood, reducingdemand. Using the approximate average size ofconstructed decks gives an estimate of the demand forredwood deck material in the US. This equates toapproximately 3.6 million m3/yr. As an indication, thisdemand is approximately 80% of New Zealand’s totalsawn wood production in 2003. These figures areindicative only, as a greater proportion of decks in thewestern US use redwood, compared with the rest ofthe US. Also, decks in the south-western US tend tobe larger on average than elsewhere.

Figure 5: Redwood markets in USA

Delivered Log Values - Mendocino County, California

$0.00

$100.00

$200.00

$300.00

$400.00

$500.00

$600.00

$700.00

NZ$

/cub

ic m

etre

RW Avg

RW 6-16"

RW 17'+

RW Old Growth

Douglas-fir

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

The US decking market

Log Prices

Cal

iforn

ia R

edw

ood

Ass

ocia

tion

web

site

.


Most redwood logs exported from New Zealandhave been marketed to Asian countries, suchas Korea and Taiwan. Sources in this market

Figure 7:Weatherboardson building,CoromandelPeninsula

Figure 6:Debarkedredwood logs atthe Palco sawmillat Scotia,Humboldt County.

have suggested that they would purchase allthe lumber New Zealand could produce andmatch US prices.

Rob

Web

ster

Nic

k K

ent


Key Points

Suggested reading:

There is considerable between tree variation in redwood wood properties,in both density and durability.

Redwood has a strong market niche in California, which has moved frompredominantly old crop to younger second crop logs.

New Zealand growers have an opportunity to market redwood logs inCalifornia as well as locally.

Clones or seedlots with acceptable durability ratings will be a key tomarket acceptance in both New Zealand and California.

Bier and Britton 1999

Clark and Scheffer 1983

Clifton 1994

Cornell 2002

Cown 2008

Di Maio 1997


Nicholas and Garner 2007

Webb 2007


CHAPTER 3 - SITE SELECTION

Ian Brown (NZFFA), Charlie Low (Scion), Ruth McConnochie (Nelson),Ian Nicholas (Scion), Rob Webster (NZ Forestry)

Assessment of the performance of redwoodon a wide range of New Zealand sites overthe last ten years has shown that the specieshas a wider range of site tolerances thanpreviously thought. However, redwoodperforms best on soils of moderate to highfertility in areas with reasonable year-roundrainfall. Avoid planting redwood on terracedsites where deep sediment deposits can leadto anaerobic conditions unfavourable toredwood growth. Redwood is intolerant ofstrong prevailing winds, but is surprisinglyresistant to toppling and breakage fromperiodic storms. (Note that despite its commonname coast redwood, derived from its naturalrange being close to the coast, redwood isnot tolerant of salt-laden coastal winds!).

In its natural habitat, redwood grows fromsea level to 900 metres altitude but prefersaltitudes lower than 750 m. It prefers mildclimates, although in many parts of its naturalrange it experiences winter snow and frostsof up to –10ºC. The presence of wellperforming stands near Winton, Southland;North Canterbury; and Hamurana Springs.Whakarewarewa and Waiotapu near Rotorua,attest to the species’ ability to do well in somecold sites in New Zealand. However, it isvulnerable to out-of-season frosts, perhapsthe reason for the much publicised earlyestablishment failure of various stands in theCentral North Island during the 1920s and1930s.


This left 27 sets of data for analysis. Preliminary results are presented below. This shows a hugevariation in growth with over 4 m difference between the best and poorest-performing sites. Considerablevariation also occurred between plantings within regions. In Northland alone there was nearly 4 mdifference between the best and worst site. The mean of the 19 North Island sites was 2.53 m, whilethe mean of the eight South Island sites was 1.5 m.

While the trial layout was the same and the clones were repeated on each site, it is difficult to interpretthe main reasons for the difference in growth performances, as individual owners managed sitepreparation and weed control in different ways. Differences are likely to be at least in part due tomicrosite differences in both soil and site. More time and soil sampling is needed to determine this.

0

50

100

150

200

250

300

350

400

450

500

Trial location

Mea

n he

ight

(cm

)

Waik

ato

Northl

and

Povert

y Bay

Waik

ato

Bay of

Plen

ty

King C

ountr

y

Corom

ande

l

Canter

bury

Waik

ato

Manaw

atu

Tara

naki

Bay of

Plen

ty

Bay of

Plen

ty

Nelson

Hawke

s Bay

Northl

andOtag

o

Tara

naki

Manaw

atu

Wes

tland

Wair

arap

a

Hawke

s Bay

South

Canter

bury

Southl

and

Canter

bury

Northl

and

Canter

bury

Figure 8: Average trial height at age 4 years

Sequoia Action Group Research Packs

During the winter of 2002, the Sequoia ActionGroup, of the New Zealand Farm ForestryAssociation, arranged for individuals to plantsmall plots with up to eight representatives ofeight clones of redwood on a range of sitesthroughout New Zealand. The trial was designedby Prof. Bill Libby. Spacing was 5 m x 5 m, andplants were in groups of four identical clones.

The trials were assessed by farm foresters in2006. In all 34 replies from the 53 sites werereturned (64%), seven sites were abandoned,three failed because of frost, two because ofsoil erosion and or slips, and one had problemswith chemical control.


Key Points

Suggested reading:

Redwood is very site sensitive

Avoid severe out of season frost sites

Avoid exposed locations

Avoid coastal situations

Redwood does best in moist valley bottom locations

Giant sequoia can tolerate cold dry sites as a specimen tree, but itssite requirements as a plantation crop remain unclear.


Snowdon 2003

Webster 2008

Marden 1993

Giant sequoia has not hadthe plantation history ofredwood to help guide sitingrecommendations. Howeverthe successful plantings inparks around the country, inparticular, in cold and dryinland South Island locations,supports the impression thatgiant sequoia can toleratecolder and drier conditionsthan redwood, although astudy of trees survivingdroughts in the early 1990sidentified giant sequoiaas susceptible to drought.


CHAPTER 4 - HEALTH

Key Points

John Bain and Ian Nicholas (Scion)

Redwood and giant sequoia have a justifiedreputation for being healthy species, withno major insect or disease problems.

There has been some anecdotal evidence thatpruning can allow entry of a native longhornborer or huhu beetles, Prionoplus reticularis,whose tunnels severely down-grade the valueof the sawn timber. Attack from these insectsis only in the heartwood, with entry gainedthrough dead branch stubs and/or stemdamage which exposes heartwood. Theincidence of attack is unknown, but expectedto be sporadic rather than constant. Thisproblem has been more commonly reportedfrom warmer areas (Northland, Bay of Plenty)but the extent of this risk has not beenobjectively quantified.

The New Zealand drywood termite, Kaoltermesbrouni, are secondary colonisers, obtainingentry to the dry heartwood through the boreholes of other insects. Dead branch stubs/barkencased knots provide access past the sapwood

band for the lovers of the dryer heartwood.Significant damage to the heartwood can resultfrom the termite colony and associatedinfection and rot. Stand management whichminimises dead branches could be expectedto reduce the risk of such attack.

Growing tips of redwood have suffered someleaf-roller damage, but this has not been ofmajor concern.

A canker fungus, Botryosphaeria has beenreported to cause minor damage on bothredwood and giant sequoia. It has beenreported that seedlings in nurseries can haveproblems with botrytis. Cypress canker hasbeen recorded on giant sequoia, but its impactis unknown.

Possums can create damage to leaders insome locations and it is prudent to controlpopulations if establishing redwood plantations.Cattle can also cause bark damage in youngstands.

Redwood is generally a healthy species inNew Zealand situations.

Dead branches can offer entry points toborers.

Possums can cause some leader damageon young trees.

Cornell, 2002


Suggested reading:


CHAPTER 5 - SEED SOURCE and BREEDING

Charlie Low (Scion), Ruth McConnochie (Nelson), Harry Saunders (NZ Forestry)and Toby Stovold (Scion)

The natural distribution of redwood in bothlatitude and altitude offers the opportunity toselect seed sources that could do well in NewZealand but very little formal breeding hasbeen undertaken in New Zealand to date.There has been more emphasis on usingexisting collections as a starting point ratherthan developing a broad genetic base for long-term tree improvement programmes. However,the ability to grow redwood as cuttings allowsgrowers to reproduce elite material. Thisprovides opportunities for selection and clonalpropagation of elite material. Those plantingforests should ensure they have the bestgenetic material available that has a proventrack record in New Zealand.

Provenance Trial

The first full test of redwood seedlots was atrial established in Rotoehu Forest in 1981.This compared nine seedlots - eight from thenatural range and one from the RedwoodGrove at Rotorua. The poorest performer wasthe Redwood Grove source.

Kuser clonal provenance trials inNew Zealand

Background

These trials derive their name from ProfessorJohn Kuser, a long-time redwood scholar ofRutgers University, who in 1983 initiated acollection of seedlings from 98 different standsin locations throughout the natural range ofredwood to evaluate provenance variation inthis species.

Redwood provenance trial

The 1981 Rotoehu trial was assessed fordiameter and stem form in January 2001.

There were noticeable differences in treesize across the site with trees on the lowerslopes being larger than those on the higherground. Stem diameter of the individual treeswas extremely variable and this tended toobscure any differences between seedlots.

However the measurements suggested thatseedlots from the Korbel area of Californiaperformed well for growth and that theWhakarewarewa Long Mile seedlot was theslowest growing. If past damage caused bypossums is discounted then most seedlotshad acceptable stem form.

The trial was planted at 950 trees per hectareand had an effective stocking rate of around660 trees per hectare. The overall averagediameter on this site at age 20 years fromplanting was 320 mm compared with 280mm for the Whakarewarewa seedlot. A fewof the largest trees in the trial were over 600mm in diameter.

Source: Vincent 2001

The intention was to compare the impactof various environmental conditions onthe relative performance of materialfrom throughout the natural range ofredwood at a number of sites. This wouldprovide information as to the best part of thenatural range for selecting plant material.


Note that this was not a provenance trial inthe traditional sense, in that the collectionfocused on just two random seedlings fromeach part of the range.

The reason for using vegetative propagationrather than seed was the difficulty of collectingseed from all populations because redwoodhas relatively few good seed crop years inCalifornia. The collection comprised of 198genotypes, mostly young seedlings butoccasionally cuttings from sprouts or olderseedlings. During 1984 Dr Kuser delivered allhis plants to the Simpson Timber Companynursery at Korbel for rooting. The Korbel stoolbeds were replicated at the University ofCalifornia (Berkeley) Russell Reservationresearch facility, and a Californian Division ofForestry site at Jackson State Forest. Thelatter site was not maintained and only thetwo sites now exist in California. Replicatestool beds now exist in France and Spain.

New Zealand Trials

Recent redwood trials in New Zealand beganback in 1990. Bill Libby was working at thethen Fletcher Challenge facility at Te Teko inthe Bay of Plenty, and encouraged theimportation and evaluation of some of theKuser collection. Fletcher Challenge Forestsestablished a small number of tissue-culturedplants in a few trials in the late 1990s. Anumber of the clones from the aboveimportations have been used in two series ofclonal trials established by the NZ FarmForestry Association on sites provided bymembers throughout the country. These trialsprovide an opportunity to compare sitesthroughout New Zealand.

A number of other clones were imported at alater date. Wade Cornell of Diversified Forestsimported more clones from the RussellReservation site in late 2000 along with otherselections from redwood’s natural range.

Sequoia Action Group research packs(2002)

During the winter of 2002 the Sequoia ActionGroup of the New Zealand Farm Forestry

Association established small trial plantingsof 64 trees (up to eight representatives ofeight clones ) on 53 sites throughout thecountry (see Chapter 3).

Kuser Trial Establishment (2003-2006)

During 2001, the Soper-Wheeler Companywith their then New Zealand subsidiary “JPS”,now The New Zealand Redwood Company(NZRC), imported to New Zealand 182 clonesof the original 198 in the Kuser collection. JimRydelius, the Manager of NZRC at the time,was involved in the initial selection andpropagation of the Kuser Clones and in theSimpson Redwood breeding programmeundertaken during his time with the SimpsonTimber Company at Korbel, California.

Stool beds were established at the SouthernWoods Nursery in Canterbury. The Kuser cloneswere multiplied by cuttings and in 2003; 174clones were established in clonal trials at threeNew Zealand sites. A further eight trials wereestablished in 2004-2006 with 136-160 cloneson each site. The objectives of these trialswere to establish long term field tests thatwould quantify variation in growth, form andwood properties. To help to achieve this, trialsites have been distributed throughoutNew Zealand so that site variability in termsof altitude, latitude, soils type and climate willallow the evaluation of the clones for site xgenotype interaction. Sites range from 40 mabove sea level to 595 m. Each trial site hasbeen planted with 8 replicates of each cloneset out in six blocks of 36 trees at 3 m x 3 mspacing. Seedlings of a single seedlot areincluded as a control. The trial design,establishment and monitoring has beencoordinated by Scion-Genetics and NZ ForestryLtd.

Giant sequoia trials

In the early 1970s, Lauren Fins, as a PhDstudent of Bill Libby’s at University of California,Berkeley, undertook a seed collection of upto 50 trees in each of 34 of the scatterednatural stands. Most of the seed was extractedfrom cones harvested by squirrels. The studywas quite extensive, looking for differences


in seed and isozymes at the individual-treeand provenance levels. When the study wascompleted much seed had been used, butthere was enough to make up 16 seedlotscomprising seed from at least five trees pergrove (or provenance), which was sent to NewZealand.

This seed was sown in a glasshouse at Rangioranursery in December 1975 and seedlings werepricked out into PB3 containers. The seedlingswere planted out on three sites, Hanmer(Canterbury), Craigieburn, (Canterbury), andBeaumont, (Otago), in winter 1977 andcuttings were planted on a further two sitesin 1978, Rai Valley (Nelson), and Kakahu,(South Canterbury). A further planting of 112unidentified cuttings was planted out adjacentto the seedling trial at Beaumont, the bestplanting site chosen.

The trial stocking is unusual, with the giantsequoia planted at 6 m x 5 m, then interplantedwith larch to provide a spacing for the mixedstand of 3 m x 2.5 m. The initial standcomposition featured larch (Larix decidua), at1,000 stems/ha and giant sequoia at 333stems/ha. The nurse species planted atCraigieburn was birch (Betula verrucosa),rather than larch.

The giant sequoia were fertilised and releasedwith Caragard, to control weeds. The spraydamaged a number of trees at Kakahu. Halfof the larch were removed at Hanmer andBeaumont in 1986. Early growth was painfullyslow, in spite of the fertilising and releasingfrom weeds.

The Rai Valley site was assessed in 1981,when the cuttings were then aged three years.All other sites were assessed in 1983, whenthe seedlings at Hanmer, Beaumont andCraigieburn were six years old and the cuttingsat Kakahu were five years old.

Best provenances reached only two metres inheight at the best site, Beaumont, six yearsafter planting. Average height at the othersites was around one metre, although survivalat all sites planted with seedlings was high at90-100%. Survival of cuttings planted atBeaumont was 98%, while Kakahu rangedfrom 29 to 92% and Rai Valley from 50 to100%. Possible explanations for the lower

survivals of cuttings are that Kakahu and RaiValley were harder sites and the spray damageat Kakahu.

The Beaumont trial was measured in 1987,1989 and 2002. The rate of height growthimproved considerably at Beaumont after age6, with the trees trebling their height to aroundsix metres by age 12. Height growth for eachseedlot was graphed against time for theBeaumont data (Figure 9) and the slope ofthe line becomes much steeper after age six.One seedlot shows slightly faster height growthbetween ages 10 and 12 but for most the rateof growth is constant from age 6 to age 12.

The 1978-planted cuttings appeared to begrowing at least as well as the seedlings atthis site, with the 30 cm difference in heightin 1983 roughly equal to one year of earlyheight growth for the seedlings, planted ayear earlier. Form assessment showed thatmalformation is negligible at this site, withthree trees being forked and four treespossessing ramicorn branches. The largesttree at age 12 was 9.5 m in height and 330mm in diameter and had grown 2.7 m inheight in two years.

The New Zealand seedlot from Raincliff wasnotable for its poor performance relativeto the Californian seedlots. This is very differentfrom the usual story in New Zealand coniferplantations, in which the neighbourhoodinbreeding of natural stands is typicallybroken down, and some natural andsilvicultural selection can occur for adaptationto local conditions, to produce more vigorousseed than natural stands in the country oforigin. The poor performance is most likelydue to deleterious effects of inbreeding, andcaution must always be taken when collectingfrom sources of unknown origin. At age 25the best seedlot was over 17 m tall and thepoorest 13.5 m tall. Most of the seedlots hadsimilar heights to each other at age 25 years,but progeny from the New Zealand Raincliffstand was significantly shorter.

The best tree from each seedlot had scionmaterial taken in 1989 and the resultant graftsare growing at Proseed’s Amberley SeedOrchard since 1990.


Figure 9: Seedlot mean height and diameter at Beaumont, 1983, 1987, 1989 and 2002

Figure 10: Beaumont Trial at age 27 years

Diameter growth over time at BeaumontD

iam

eter

(cm

)

60

50

40

30

20

10

0

0 10 20 30Age

Height growth over time at Beaumont

Hei

ght (

m)

181716151413121110

9876543210

0 10 20 30Age


Once giant sequoias are fully established, froma slow start their growth rate improvesconsiderably. Height growth in excess of onemetre per year can be attained, along withdiameter growth of over 25 mm per year ontrees over 10 years old, on good sites. TheBeaumont site, benefiting from extra waternutrients by being at the foot of a slope, witha deep river terrace soil, is evidently an idealsite for this species.

Figure 11: Giant sequoia atHanmer, aged 25 years

The trial at Hanmer was assessed in 2002,when tree heights had improved from anaverage of 1.4 metres at age six years toaround 12 m at age 25. The largest tree was18 m tall and 700 mm in diameter. Provenancemeans from the 2002 assessment are shownin Figure 12. An average-sized tree of300 mm diameter and 14.6 m in height fromthe North Calaveras provenance is shown inthe photo below.

from a single tree, so that all seed would beselfed, therefore highly inbred. Whatever thecase, no further seed should be collected fromthis stand. Regrettably, there have been anumber of seed collections from Raincliff overthe years, and this may explain some of thefailures of this species in New Zealand.

At Hanmer, only two trees had kinked stems,which appeared to have been caused by weedcompetition. Only one tree was forked.Branching was fine, with no branches largerthan 2 cm. The 25-year-old trees could bepruned with light secateurs.

The Hanmer trial had more seedlots testedthan Beaumont. The best-performing seedlotat Beaumont was not the best at Hanmer, butprogeny from the Raincliff stand averaged thepoorest on both sites. Inbreeding depressionis a very plausible explanation for fhe poorperformance of the Raincliff seedlot. Theseedlot register reveals that there were onlyfour trees in the parent “stand”. All fourtrees could well have come from a singleseed parent, so the seed would result frombrother/sister mating. Conceivably, all fourtrees could have grown from cuttings taken

Vegetative propagation of giant sequoia

Difficulties in obtaining seed, poor seedgermination, and some high levels of inbreeding,make vegetative propagation of known superiorgenetic sources an attractive option for thespecies. Rangiora nurserymen found the specieseasy to propagate from 18-month-old seedlingsand it is a species which can produce coppicegrowth when felled. Ideally, plants should begrown from outcrossed seed produced in theAmberley orchard and multiplied vegetatively,or cuttings harvested from the coppice ofsuperior mature trees. Care must be taken toavoid maturation of select material.


Figure 12: Mean provenance height for Hanmer and Beaumontsites at age 25 years

0

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Cedar

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rse B

asin

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ff NZ

Seed source

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s (m

)

HanmerBeaumont

Key Points


The Kuser collection, while representing a geographic spread, is nota true provenance-wide selection of seed sources.

The Kuser collection has provided material for a range of trials on64 sites throughout New Zealand from 2002-2006

Limited redwood provenance evaluation has been carried out on onesite, established in 1981.

Giant sequoia provenance trials were established on five sites in1977-1978.

Progeny from the Long Mile Grove redwoods and Raincliff giantsequoia trees perform poorly compared with other provenanceseedlots.

Future selections of redwood and giant sequoia should be based ona wide genetic base and with regard to wood properties.

There has been no breeding for redwood in New Zealand, but thereis potential for significant improvement of redwood performance forboth growth and wood properties.

Fins and Libby 1982


Libby 1993

Saunders and McConnochie 2007

Vincent 2001

Suggested reading:


CHAPTER 6 - ESTABLISHMENT

Ian Nicholas (Scion) and Simon Rapley (NZRC)

To create a successful plantation redwoodmust be well sited, robust planting stock usedand key establishment measures taken. Apartfrom one trial, little published research hasbeen conducted on establishment techniquesin New Zealand. However with over 1,000 haestablished in the last few years, plenty ofoperational experience is accumulating.

The key to successful establishment is weedcontrol, especially over the first two growingseasons after planting. Fertiliser may also berequired, depending on location.

A standard establishment regime could be:

Pre-planting spray ( Roundup or Gallant)

Planting 800 stems/ha. A seedling clonalrow by row planting pattern is suggestedto provide thinning options to favour eitherrow in the future.

Fertilisation (if required)

Release immediately after planting to controlweed germination if required

A second release at 18 months (or earlierif required). Generally no chemical should

be sprayed over the top of seedlings, buta shield can be used in combination witha single fan nozzle.

Alternately, establish 500 stems/ha of eliteclones (that have been formally tested) toachieve a final crop of up to 400 stems/ha.Elite clones selected for fine branching andstem form (among other characteristics) donot need higher initial stocking to controlbranch size or encourage form. Becauseredwoods coppice vigorously once felled,thinning must be delayed to prevent thecoppice competing with the final crop. Delayingthinning to control coppice is likely to suppressthe growth of the crop trees.

An establishment trial in the East Coast regionshowed that the best growth was achieved byapplying a combination of fertiliser and weedcontrol. Of the two treatments on that sitefertiliser was the most important (Table 3).

Table 3: Growth of Coast Redwood, initial 3 years (from Bowles, 1980)

Fertiliser, grass controlled

No fertiliser, grass controlled

No fertiliser, no weed control

Mean height increment (cm)

1st year

42

30

14

2nd year

67

49

24

3rd year

89

75

58

Treatment

68

49

31

End 3rd yeardiameter (mm) at

ground level


Although they grow to a magnificent size, and can make very high current stem-volumeincrement, giant sequoia is slow to become fully established, and will require excellent weedcontrol to hasten the process.

Key Points

Suggested reading:

Correct siting, robust seedlings and weed control will ensure successfulestablishment.

Redwood requires weed control for at least 18 months and possiblyfertiliser to promote early growth.

Giant sequoia is a slow starter and will require prolonged weed control.

Bowles, 1980

Cornell, 2002


CHAPTER 7 -PRUNING and THINNING

Mark Dean (Ernslaw One), Mark Kimberley (Scion), Paul Silcock (Scion)and Rob Webster (NZ Forestry)

Introduction

Redwood has proved to grow well in NewZealand when correct siting and establishmentpractices are attended to. With mean annualincrements in excess of 30 m3/ha/year ongood quality sites (warm, sheltered and withregular rainfall e.g Taranaki or Bay of Plenty),growth rates can equal or better those ofradiata pine. Redwood is more shade tolerantthan most conifer species so will survive invery low light situations. However it doesrequire full sunlight to grow rapidly. Perhapsbecause of these attributes redwood readily

Figure 13: 29 year old untended redwood, East Coast

grows from coppice and stump or root sprouts.These physiological attributes potentially allowsome innovative regimes not commonlypracticed with more light demanding coniferspecies.

Redwood enjoys a strong market demand inUSA (Chapter 2), where restricted access tonatural stands enhances the potential for anexport market to develop for New Zealand-grown redwood. However, the Redwood lumbermarket differs from the radiata pine modelwe are used to. In California, clear heartgrades attract a large premium over those


Current Issues

While New Zealand growth rates allow forrotation lengths of around 35 years, carefulattention will need to be paid to designingregimes that will capture most of the potentialvalue with such rotations. The target will beto achieve large pruned butt logs with upperunpruned logs with green or moribundbranches less than 50 mm diameter. Althoughthere have been several hundred hectares ofredwood grown and harvested in New Zealand,most have not been intensively managed sothe effect of various pruning, thinning andinitial/final crop stocking combinations hasnot yet been quantified.

with sapwood content and unpruned ‘tightknot’ grades, which in turn are more valuedthan timber with bark-encased knots. Thisgrade and price differential, based on branchcondition as well as size, provide an importantdistinction from the radiata pine lumbermarket, which most New Zealand forestgrowers are used to, and will provide somechallenges in managing redwood silviculture.

However, over the past few years Scion, withassistance from NZ Forestry Ltd, The NZRedwood Company and the PlantationManagement Cooperative, has initiated anumber of silviculture trials to study some ofthese interactions. A series of final cropstocking trials have been installed in existingstands located in the Central North Island,East Coast, Hawkes Bay and Otago. Withinfour or five years there will be sufficient datato formulate a thinning-response function toaugment the basic growth functionsimplemented in the NZ Forestry/NZ RedwoodCompany growth model. This will allowmanagers to predict the outcome of variousthinning and final crop stocking regimes interms of tree growth.

Given the high value of clearwood and thepremium for heartwood over sapwoodcombined with the uniform wood propertiesfrom pith to bark, pruning to achieve theseclasses of end-product is certainly a favouredoption. It may be worth pruning redwoods to

a small DOS as has been done with cypressesin some instances.

Operationally speaking, pruning redwood isnot difficult. The wood is relatively soft andbranches in plantation grown trees aregenerally small and well-spaced. Althoughredwood bark is thick and fibrous on maturetrees, young trees have bark that is easilydamaged so care must be taken to not damagethe bark and cambium around branch collarswhen pruning.

Two pruning trials, at Tutira and Gisborne,have been installed by the PlantationManagement Cooperative in partnership withThe New Zealand Redwood Company. Althoughstill in progress, interim results indicate thatboth stocking and pruning severity affect treegrowth.

Of much greater interest is the impact ofpruning severity on the incidence of epicormicshoots. These originate from buds in thecambium and are stimulated by thecombination of stress induced by removingthe green crown (live branches) and light onthe stem. When early severe pruningtreatments are applied the stems can beclothed with epicormic shoots which negatesthe pruning effort. However, by delayingpruning until the bark is thicker, pruning inautumn and leaving more green crown, muchof this problem may be avoided.

Figure 14: Epicormic shoots sprouting from thebranch collar and cambium of a young pruned tree.


Another silvicultural challenge is to maintainlive or only recentl dead branches in the lowerunpruned logs, typically from 6-15 metresheight on mature stems. Currently ourunderstanding of crown height recession withincreasing stocking and age is fairly basic.There is a need to better quantify this andalso to understand the time delay betweenbranches dying and the formation of bark-encased ‘loose knots’. As for managing redwoodstands to minimise the incidence of bark-encased knots in sawlogs, there are a numberof possible strategies which, to the authors’knowledge, have yet to be tried. For example,regimes involving multiple thinnings or possiblyultra high pruning may serve the desired goal.

There have recently been sales of small logs(down to 20 cm SED) which can be sawn forutility uses. This may make it possible to carryout production thinning on some sites.Alternatively, pruning dead branches tofacilitate higher recovery of more valuable‘tight knot’ grades of lumber may be warranted.

As stated earlier, log quality is of paramountimportance in order to maximise the returnsfrom redwood. To date very little is understoodabout the timber grade and hence valuerecovery from various log types arising fromregime options. The sawing study currentlybeing carried out by Scion and Interpine withfunding through FIDA and the redwood themewithin Future Forests Research Ltd shouldsignificantly improve baseline knowledge andprovide for realistic economic analyses toattract investors and set fair market valuesfor logs.

Silvicultural research

In recent years Scion, with industry support,has established more than 60 permanentsample plots in stands throughout NewZealand. In response to interest from clients(The New Zealand Redwood Company, NZForestry Ltd), Scion has collected retrospectivegrowth data and developed a preliminary NewZealand Redwood Growth Model to predictyield. It is intended that as more data becomeavailable the model will be improved andmortality, pruning and thinning responsefunctions will be added.

Figure 16: Insect attack, possibly pin hole boreron an 8 year old pruned redwood. This attack

may have been aborted once through the bark.

Figure 15: Left unmanaged epicormic shootscan quickly undo the pruning investment. Theepicormic growth on the lower portion of these

trees is just 12 months old.

With funding from the Plantation ManagementCooperative a series of trials designed toquantify growth response to final crop stockingand to investigate the effects of pruningseverity and timing on growth and log qualityhas been installed (Table 4).


Table 4: Replicated silviculture response trials.

Plant year

1982

1986

1978

1998

Trial type

Final crop stocking

Final crop stocking

Final crop stocking

Pruning, final crop stocking

Date Installed

July 2004

August 2004

April 2004

Dec 2003

Location

Waiotapu (CNI)

Otago Coast (Otago)

Mangatu (East Coast)

Tutira (Hawkes Bay)

Case Study: Waiotapu Redwood Final Crop Stocking Trial

Coppice growth two years after thinning

Redwood is among the few conifers capable of producing true epicormic shoots (‘sprouts’). Sproutsarise from dormant buds found along stems and, branches, and among burl tissues at the base ofthe tree/root collar, and can therefore coppice from stumps. Buds can be released from dormancywhen sources of inhibiting hormones are eliminated and environmental conditions are favourable. Two opposing processes affect the vigour of a sprout clump: the decline in carbohydrate andmineral-nutrient reserves in the stump, and the accumulation of reserves by the sprout clump. Thesprout-clump vigour is therefore a function of both the reserves at the time of cutting and the lightenvironment following cutting.

The initial 2-year measurement of coppice growth in this trial provided data on the frequency,recruitment and vigour of sprout growth on thinned redwood stumps under three final-crop stockings.Over time this data will be useful in evaluating silvicultural regimes where coppicing may be desired(continuous-cover forestry) or not (when thinning to a final crop). The stand was planted in 1982with an initial stocking of 1200 stems/ha. It was thinned in 2004 to four stockings: 350, 500, 650and 1000 stems/ha.

A simple survey carried out in spring of 2005 and 2006 measuring number and height of coppiceat each thinning stump shows the effect of light on coppice incidence and vigour. Figure 17 showsa higher incidence of stumps coppicing in the lower final crop stocking whereas Figure 18 showsa much higher number of shoots per stump occurring in the 500 stems/ha treatment.


Figure 17: Incidence of coppicing stumps across three different final crop stockingthinning treatments in Waiotapu forest in 2005 and 2006

Figure 18: Vigour of stump coppice as shown by number of shoots perstump across three different final crop stocking thinning treatments in

Waiotapu forest in 2005 and 2006

Incidence of coppice across treatments

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

350 500 650

Stems/ha

% S

tum

ps to

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pice

2005

2006

Shoots per stump across treatments

0.00

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20.00

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40.00

50.00

60.00

350 500 650

Stems/ha

Num

bers

of s

hoot

s pe

r stu

mp

2005

2006


Case Study: Epicormic Shoots

Although there is considerable interest in growing and intensively managing redwood in New Zealand,little is understood about how it responds to the intensive silviculture commonly practiced with radiatapine in this country.

One such response is that of epicormic shoots developing up the length of the trunk after pruning.The shoots arise from buds that otherwise remain suppressed by the concentrations of auxin andcarbohydrates in the phloem. Rapid changes in the light levels, temperature, nutrients or moisture canalso induce a similar response.

Epicormic shoots are not true branches and do not have a knot that goes right back to the pith like anormal branch. If removed within the first season they may not cause any serious loss in clearwoodrecovery. However if left growing, they could cause serious downgrade to the target pruned clearwood.

In 2004 a replicated randomised block design pruning trial for redwood was installed at Tutira inHawkes Bay. Silviculture treatments covered a range of three pruning intensities and three stockinglevels. In the Wairengaokuri step- out trial, two replicates of one treatment have been established,with half the trees in each plot being pruned in spring and the other half pruned in autumn to test ifseason of pruning has any impact on development of epicormic shoots.

An assessment of epicormic response across the different treatments was carried out in November2005 and December 2006, 22 and 35 months after pruning.

At the two trial sites intensive pruning resulted in sufficient numbers of epicormic shoots of significantsize as to severely compromise clearwood yield. The incidence and size of epicormic shoots provedto be dependent on the severity and season of the pruning treatment. Most (and the largest) epicormicshoots appear on those stems pruned in spring, with the most severe treatment (5.5cm calliper), onthe portion of the stem exposed to the most sunlight (1.2 m).

The effect of season on shoot numbers reduces over time, with no difference between spring andautumn two years after pruning. However those shoots that remain are significantly larger on the stemspruned in spring. Therefore it may be advantageous to delay pruning until the trees have thicker barkand a greater degree of canopy closure and retain a number of follower stems to provide shade to thestem. Scheduling more lifts of less severity during the autumn months should reduce epicormicincidence and size.

Key Points

Redwood requires pruning to produce clearwood

Overpruning can result in epicormic shoots

Pruning in autumn reduces epicormic shootdevelopment

Dean, 2007


Suggested reading:


CHAPTER 8 - GROWTH MODEL and REGIME EXAMPLE

Ian Nicholas, Paul Silcock (Scion),and Rob Webster (NZ Forestry)

The increasing popularity of redwood forestryin New Zealand means an escalating need forpredicting growth and yield, to provide greaterconfidence for those investing in redwood.First-generation models have been developed.

NZ Forestry in association with the NewZealand Redwood Company has beeninstrumental in initiating the development ofa Redwood Growth Model and new volumeand taper equations for redwood in NewZealand. The growth model predicts basalarea (BA) and mean top height (MTH) forredwood grown in New Zealand. The modelwas developed using data from stem analysis(felling trees, cutting into discs andreconstructing growth by growth-ring analysis)of trees from eight stands supplemented withdata from 32 PSPs (Permanent Sample Plots).Most of the PSPs have only recently beenestablished and they therefore only providean estimate of yield at a single point in time.Stem-analysis data were therefore used tocharacterise growth trajectories and determineappropriate model equation forms, while thePSP data were used to calibrate this model toactual-plot measurement data representativeof the species and covering a reasonable rangeof New Zealand sites.

The Site Index for New Zealand redwood isdefined as MTH at age 40 years. Basal areaproductivity is based on a “400 Index” measure(BA40/400) defined as BA at DBH at age 40years and a stocking of 400 stems/ha. Themodels, along with a stem volume function,have been implemented in a Microsoft Excelspreadsheet-based application.

Performance within New Zealand

The New Zealand Redwood Growth Model hasbeen derived from stands established withgenetically unimproved seed. Hence predictionsfor stands now being established from importedseed orchard material or select clones arelikely to be under-predicted.

Table 5 presents data from a number of siteswithin New Zealand. The table presentsestimated site index and BA40/400 for eachsite and growth model predictions at age 35years for the specified targets of final cropstocking.


Figure 19: Site Index of cross section of New Zealand stands

Table 5: Growth model estimations in growth of selected stands.

47

43

49

40

40

39

35

40

36

29

35

32

37

39

Site Indexm@ 40

yrs

450

400

350

350

350

325

350

325

325

350

325

325

300

348

Targetstockingstems/ha

73.5

71.4

59.5

64.9

64

59.6

62.3

57.2

55.2

62.3

55.2

57.7

53.9

61

PredictedDBHcm

184.2

154.6

93.9

115.8

112.8

87.5

103.2

80.8

75.2

103.2

75.2

82

66.1

103

PredictedBA

m2/ha

1871

1445

975

1036

1008

754

808

712

604

682

590

598

542

894

PredictedVolumem3/ha

Bay of Plenty

East Coast

Hawkes Bay

Taranaki

East Coast

Taranaki

Rotorua

King Country

Taranaki

Wellington

Wanganui

Otago Coast

Reporoa

Mean

Location

53

41

28

30

29

22

23

20

17

19

17

17

15

26

PredictedMAI volm3/ha/yr

213

202

132

154

150

128

145

118

110

145

110

120

101

141

BAm2/ha

It is clear from these estimations of yield that redwood on good sites is capable of at leastmatching the average yield of radiata pine on many sites.

0

10

20

30

40

50

60

Hawke

s Bay

Bay of

Plen

ty

East C

oast

Tara

naki

East C

oast

King C

ountr

y

Tara

naki

Repor

oa

Tara

naki

Rotoru

a

Wan

ganu

i

Otago C

oast

Well

ington

Region

Site

inde

x, h

t at a

ge 4

0 yr

s (m

)


Rotorua’s Long Mile Redwood Grove in Whakarewarewa Forest

In Whakarewarewa Forest planting began in 1899. With 170 tree species planted,it was one of the first large experimental forests to help guide the afforestation ofNew Zealand. The most famous remnant of these early plantings is the RedwoodGrove.

The stand when planted in 1901 originally covered 32 ha. Apart from scatteredtrees surrounding the grove the area is now about 6 ha. A feature of the stand isthe many mature tree ferns and other native flora present throughout the Grove.

The Grove has been formally dedicated as a memorial to those who lost their livesin the two World Wars.

Apart from being Rotorua’s most popular walking and running track the RedwoodGrove has also been used for many unique activities ranging from wedding partyphotos, dawn church services (NZ Forest Service reunion), orchestral music (FRI50-year jubilee) to the resting place of the ashes of Mr Bob Burstall (the father ofnotable trees in New Zealand).

The Grove is recognised as a historic tree site by the Royal NZ Institute of Horticulture,and is protected under the Rotorua District Scheme.


Since 1948, a 0.4 ha sample plot has been measured regularly (see measurements below).

Table 6: Growth measurements from Redwood Grove Permanent Sample plot

Ageyrs

54

57

65

68

71

78

82

86

90

95

99

100

MTDcm

97

100

107.1

109.6

111.3

115.3

117.8

120.4

123.5

126.2

128.3

128.8

MTHm

41.8

45.9

48.3

49.2

51.8

52.5

55.1

57.4

57.9

60.1

59.7

59.4

Volumem3/ha

879

1014.8

1214.2

1291.3

1397.5

1524.3

1658.3

1795.5

1890.8

2048.7

2103.0

2109.0

BAm2/ha

85.1

90.7

104.4

109.4

113.2

122.4

127.9

133.8

140.8

147.3

152.6

153.5

MTDin

31.8

32.8

35.1

36.0

36.5

37.8

38.6

39.5

40.5

41.4

42.1

42.3

MTHft

137.1

150.6

158.5

161.4

169.9

172.2

180.8

188.3

190.0

197.2

195.9

194.9

Volumeft/ac

2883.9

3329.4

3983.6

4236.5

4585.0

5001.0

5440.6

5890.7

6203.4

6721.5

6899.6

6919.3

BAft2/acre

370.7

395.1

454.8

476.5

493.1

533.2

557.1

582.8

613.3

641.6

664.7

668.6


Height growth in forest stands is measuredby Site Index (the expected height of treesat a given age). For redwoods in the UnitedStates, the Site Index is quoted as expectedheight in feet at 100 years. Measurements

Figure 20:American SiteIndices withRedwood Grovedata highlighted

Suggested Regimes

Regimes for redwood are in their infancy, with many theories as to the best options. Thefollowing reflects the current thinking on potential regimes (Table 7). This can be expectedto change as more data and experience is gained. (Check for updates via this electronichandbook).

Table 7: Suggested regime for redwood sawlogs

Operation

Pre-plant weed control

Establish 800 stems/ha

Release

Prune 420 stems/ha 0-2.5m

Prune 385 stems/ha 2.5-4.5

Prune 350 stems/ha 4.5-6.5 m

Thin 800-350

Clearfell

Age (yrs)

0

0-1

6

7.5

9

11

35

Comment

Alternate rows of clones and seedlings

Fertilise if required

Calliper prune to 12 cm diam in August



August

Target DBH 60 cm or greater

Prune in 2 or 3 lifts (depending on site productivity) with a 12 cm calliper to 6 metres inautumn. This should result in a DOS of 12-15 cm and will reduce the incidence of epicormicshoots. Timing of thinning will depend on the incidence of epicormic shoots in the crop, exposureand green crown condition.

0

50

100

150

200

250

300

20 30 40 50 60 70 80 90 100

Age (Years)

Site

Inde

x (f

t)

120140160180Rotorua200220240

from the Redwood Grove show that the standhas a Site Index of 200 feet. This is double thelowest Site Index used in US site tables of 100feet, but less than the two best Site Indicesused of 240 and 220 feet.

Comparison with growth in the United States


Key Points

Suggested reading:

Well sited redwood grows very well with high volume production figures.

A regime is suggested, with 800 stems/ha, up to 3 pruning lifts, onethinning to final crop of 350 stems/ha for a rotation length of 35 years

Berrill and O’Hara 2007

Dean 2007


Nicholas 2007

Tombleson 2004


CHAPTER 9 - ECONOMIC ANALYSES

Ian Nicholas, Paul Silcock (Scion),and Rob Webster (NZ Forestry)

The economics of growing redwoods areuncertain because of many unknown figuresin costings (Table 8), yields and returns. Asmore data are gathered and models becomemore refined, confidence in economicpredictions will increase.

In a recent comparison of alternative speciesit has been estimated, based on certainassumptions, that redwood plantations couldreturn an IRR of 10.5%. This was higher thanany of the other species assessed (radiatapine, Douglas-fir, eucalypts and blackwood).However it was stressed that this requiredgood growing sites, and assumed thatdurability issues would not impinge on themarket price. The redwood prices used in this

study were based on Californian prices costedback to New Zealand dollars.

The average MAI of 13 sites based on growthmodel predictions gives a mean volume MAI of26 m3/ha/yr with a range of 15-53 m3/ha/yr.Based on the mean volume MAI of 26 m3/ha/yrand a rotation length of 35 years, this representsa total volume of 910 m3/ha. Assuming that95% is recoverable logs a total of 865 m3/haof recoverable logs is used in these assumptions.

It is estimated that 39% is pruned material,34% large diameter unpruned and that27% is smaller diameter unpruned logs.

Table 8: Costs and operations used for base case analysis

Operation

Land cost

Land prep

Tree stocks

Planting

Fertilising

Releasing

Releasing

First prune

Second prune

Third prune

Thin

Annual costs

Stand age

-

0

0

0

0

0

1

6

8

10

10

Cost($/ha)

0

648

1360

320

252

240

250

800

840

780

380

60

Management fee (15% of costs) Roading, log and load ($50/m3 )


The revenue is based on figures quoted byPiers Maclaren who used a New Zealand valueof $184/m3 at mill door. This was derived fromcalculations by Wade Cornell working backfrom Californian prices at the time (2003) toa stumpage value back in New Zealand of$144/m3. This was converted back to a milldoor value of $184/m3.

This provides a base case with an IRR of 9.3%(not including land costs). If land costs of$4,000/ha are included, IRR drops to 6.7%.

If plant costs are halved to $720, IRR increasesto 8.9%. Using Cornell’s stumpage of $144across all log grades gives an IRR of 9.2%.

N.B. As the figures used in this analysis areof a general nature only, more detailed sitespecific analysis evaluated by professionaladvisers should be used on a case by casebasis before investing in redwood forestry.

Key Points

Suggested reading:

Analysis of redwood forestry shows a positive return (based onCalifornian prices), with an estimated IRR of 9.3%.

Seek professional input before any large investment in redwood forestry.

Insufficient information is available to analyse giant sequoia forestry.

Maclaren, 2005


CHAPTER10 - UTILISATION

Ian Nicholas (Scion) and Rob Webster (NZ Forestry)

Both New Zealand-grown redwood andimported timber is being utilised in NewZealand, predominantly for weatherboards.Minimal problems have been reported by thosesawing redwoods and the sawing of large treesfrom the Scion campus (for example) wasconducted without any major problems.

New Zealand-grown redwood has performedwell in most situations but weathering of earlywood has been an issue in some exposedsituations. The recently completed sawingstudy of a tended 38 year old stand fromMangatu will provide a wealth of data onconversion rates and timber grades from amanaged redwood plantation. The issue ofheartwood percentage and reliable durabilitywill be the key aspects of successful utilisationof future redwood plantations.


Redwood Pole House

NZ grown redwood weatherboard

Redwood cladding, Hawkes’ Bay

Interior feature wall in games room

Siding on house at Hahei,Coromandel Peninsula

Utilisation of Redwoods, New Zealand

Rob

Web

ster

Nic

k K

ent

Har

ry S

aund

es


Utilisation of Redwoods, USA

House, Fort Bragg

New House, Tahoe

Fencing products

DeckingGazebo

49

Rob

Web

ster

Rob

Web

ster

Cal

iforn

ia R

edw

ood

Ass

ocia

tion

web

site

.


Key Points

New Zealand grown redwood has been successfully utilised in New Zealand.

A sawing study will extend knowledge on utilisationof managed redwood.

Tombleson 2007

Suggested reading:

Home at LakeTahoe, USA

Rob

Web

ster


Ian Nicholas (Scion)

Interest in redwoods for commercial plantationshas been revived in New Zealand. This hasdeveloped for two main reasons, theperformance of second-growth redwood onthe Californian market which is lower qualitythan old-growth-timber, and recent overseasinvestment in New Zealand redwood forestry.Furthermore, the formation of a Sequoia ActionGroup within the NZFFA has seen a focus onredwood by farm forestry members andspecialist consultants. Also, a Redwood Grouphas been formed under the Diverse Speciessub-theme within The Future Forests ResearchLtd. These factors have combined to producea redwood forest resurgence, creating interestand activity within the New Zealand forestindustry. The move from amenity tree toplantation tree has generated researchactivities to provide confidence to thoseestablishing redwood plantations. Informationgained on siting and management will helpensure plantations are successfully establishedand well managed. Economic assessments,based on a range of assumptions, suggestthat redwood plantations can be grownprofitably. However, the variation in wood

properties, especially durability, must beovercome to produce a product that meetsthe expectations of both New Zealand andCalifornian markets.

Apart from some provenance trials, very littleinformation is available for giant sequoia,despite it having potential for forestry on siteswhere traditional forest species are less wellsuited.

Growing redwoods is still a small portion ofthe New Zealand forestry scene. Furtherinvestment is required to know and growimproved stock, understand wood durabilityin New Zealand-grown timber.

However it appears redwood can perform verycompetitively with main-stream forestry speciesif it is sited and grown competitively.

As more information becomes availableon redwood forestry topics this electronichandbook will be updated to provide themost up to date relevant information forthose interested in redwood plantations.

CHAPTER 11 - SUMMARY

Key Points

Suggested reading:


Growing redwood is a developing industry in New Zealand.

Experience suggests that redwood plantations can be well grown andutilised in New Zealand.

Little information exists to evaluate the potential of giant sequoia forplantation forestry.

As new information is obtained, key results will be updated throughthe NZ Farm Forestry Association via this handbook.

Nicholas et al. 2007

Tree Grower 2007


CHAPTER 12 - REFERENCES and WEB LINKS

Berrill, J.-P. and Ohara, K.L. 2007: Redwood in California,An overview of silvicultural systems. New ZealandTree Grower 27 (1), February, 2007.

Bier, H. (revised by Britton R.A.J.) 1999: Strengthproperties of small clear specimens of New Zealand-grown timbers. FRI Bulletin No 41.

Bowles, G. P. 1980: Establishing Redwood (Sequoiasempervirens). New Zealand Tree GrowerNovember, 1980.

Brown, I. 2007: Redwoods-an overview. New ZealandTree Grower 27 (1), February, 2007.

Burdon, R. D. 1975: Is coast redwood an answer to theMangatu problem? New Zealand Journal ofForestry 20 148-52.

Clifton, N.C. 1994: New Zealand timbers (revised).GP Books.

Cornell, W. 2002: The New Zealand Redwood Growershandbook. Diversified Forests.

Cown, D. 2008: Redwood in New Zealand – an end userperspective. New Zealand Journal of ForestryFebruary 2008 Vol.52, No. 4.

Clark, J. W., and Scheffer, T., 1983. Natural decayresistance of the heartwood of coast redwoodSequoia sempervirens (D.Don) Endl. ForestProducts Journal, Vol. 33, no 5. Pp. 15-20.

References / Bibliography

Dean, M. 2007: Coast redwood silviculture in New Zealand. New Zealand Tree Grower 27 (1),

February, 2007.

Di Maio, M. 1997. Softwood sawn timber trade in thePacific Rim: the position of NZ grown cypress.MSc dissertation University of Waikato.

Fins, L.and Libby, W. J. 1982: Population variation inSequoiadendron: Seed and seedling studies,vegetative propagation and isozyme variation.Silvae Genetica 31, 4 (1982).

Hay, A. E., Nicholas, I. D. and Shelbourne, C.J. A. 2005:Plantation Forestry Species: Alternatives to RadiataPine. In: Colley, M. (ed). NZIF Forestry Handbook,New Zealand Institute of Forestry, pp. 83-86.

Knowles, F. B., and Miller, J. T., 1993: Introduced foresttrees in New Zealand: Recognition, role, and seedsource. No.13 The redwoods. FRI Bulletin No.124.

Libby, W. 1993: Redwood - an addition to exotic forestry?New Zealand Forestry 38 (3) 3 -7.

Libby, W. 1999: Redwoods in Taranaki? New ZealandTree Grower, May 1999.

Maclaren, P. 2005: Realistic alternatives to radiata pinein New Zealand – a critical review. New ZealandJournal of Forestry, May 2005 3-10.

53


www.nzffa.org.nz

www.nzfor.co.nz

www.maf.govt.nz/sff

www.maf.govt.nz

www.scionresearch.com

Weblinks

Marden, M. 1993: The tolerance of Sequoia sempervirensto sedimentation, East Coast region, New Zealand.New Zealand Forestry 38 (3) November 1993,22 - 24.

Mortimer, J. & Mortimer, B. 1984: Trees for the NewZealand countryside: a planter's guide. Silverfish,Auckland.

Nicholas, I. 2007: Rotorua Redwoods. New Zealand TreeGrower 28(1), February 2007.

Nicholas, I.; Silcock, P. and Gea, L. 2007: RedwoodResearch - the way ahead. New Zealand TreeGrower 28(1), February 2007.

Nicholas, I. and Garner, S. 2007: A survey of alternativespecies markets. New Zealand Journal of ForestryMay 2007. pp. 10-13.

Poole, B. 2007: An overview of alternative speciesplantations in New Zealand. New Zealand TreeGrower 28 (4), November 2007 3 - 4.

Saunders, H. and McConnochie, R. 2007: Kuser clonalprovenance trials in New Zealand. New ZealandTree Grower 28 (1), February 2007.

Snowdon, K.D. 2003: Taupo Land Use Study, TaupoLTDC, 2003.

Tombleson, J. 2004: Redwood Memorial grove reaches100 years. New Zealand Tree Grower, February,2004.

Tombleson, J. 2007. Harvesting and marketing somepruned redwood giants. New Zealand Tree Grower28 (1), February 2007.

NZ Tree Grower, 2007. Special Feature on Redwoods,New Zealand Tree Grower 28 (1), February, 2007.

Webb, J. 2007: Redwood markets in California.New Zealand Tree Grower 28 (1), February, 2007.

Webster, R. 2008: Performance of coast redwood inNew Zealand. New Zealand Tree Grower 29 (2),May, 2008.

Weston, G, 1957: Forest Trees of New Zealand NZ ForestService Bulletin No. 13.

Vincent, G. 2001: Coast Redwood - results from a 20-year trial. New Zealand Tree Grower May 2001.

www.rarefind.co.nz

www.proseed.co.nz

www.ebop.govt.nz

www.horizons.govt.nz

www.ffr.co.nz

Visit www.nzffa.org.nz for the most up-to-date information available. 55

CHAPTER 13 - GLOSSARY

Appearance grade: Grades of timber for finishing andother uses determined basically from theappearance of the better face and edge, usuallyclearwood.

Bare-rooted planting stock: Plants (seedlings, cuttingsor other) grown in open nursery beds rather thancontainers and lifted and planted with much of thesoil gone from their roots.

Basal Area: The cross sectional area of all tree stems ina stand, measured at breast height and usuallyexpressed per hectare of land.

Basic Density: The average density of the wood at 0%moisture content

Breeding: Intensive selection and subsequent mating oftop selections to achieve cumulative genetic gainover time.

Breeding population: The population in which breederscarry out intensive selection and geneticrecombination. It comprises the selections that areinter-mated and their resulting offspring. It requiresa broader genetic base than the seed production(orchard) population.

Cambium: A layer of rapidly growing cells between thebark and the wood, from which new wood andbark develop.

Clearwood: A length of timber which is free of knotsdue to branch removal, usually achieved bypruning.

Clearfell or Clearcut: Harvesting of trees in whichessentially all trees are removed in one operation.

Clone: A group of genetically identical plants, whichhave been vegetatively propagated from a singleindividual.

DBH: Diameter at breast height of tree stems, at 1.4 min New Zealand.

Family: A group of individuals directly related by descentfrom a common ancestor.

Followers: Unpruned trees left in the stand with prunedtrees at the time of thinning.

Hardness: A property of timber that enables it to resistindentation.

Heartwood: The inner, nonliving part of a tree stem.Natural chemicals are often deposited in theheartwood, making it more durable and darker incolour than sapwood.

IRR (Internal Rate of Return): The discount rate thatequates the various costs and benefits anticipatedin future years of forestry (or other) operations.

Knots: A cross section of a branch that is imbedded intimber. The knots can either be live knots (branchwas living when the tree was cut) or dead knots(from a dead branch) which often fall out.

MAI (Mean Annual Increment): The total incrementof a stand up to a given age, divided by that age.Includes thinnings as well as standing crop.

Mean (arithmetic mean): The average value for a set ofobservations, obtained by dividing the sum of allobservations by the total number of observations.

MoE (modulus of elasticity): A measure of stiffness insawn timber.

MoR (modulus of rupture): A measure of bendingstrength in sawn timber.

Mouldings: High grade timber, usually clearwood, sawnfor specific end uses e.g. skirting.

MTD: (Mean Top Diameter): The average diameter ofthe largest 100 stems/ha in a stand.

MTH (Mean Top Height): The average height of thelargest 100 stems/ha in a stand.

Native population (syn. native provenance): A group ofnaturally growing trees found at a particulargeographic location within the native range of thespecies.

Pith: The central core of a stem and roots, inside the firstannual growth layer of wood

Progeny trial: Evaluation of parents by comparing theperformance of their offspring, properly in areplicated field layout.


Propagation: Multiplication of plants. Can be either viasexual reproduction (seed production) or via asexualmeans (vegetative propagation).

Provenance: The ultimate geographic origin of seed,pollen, or trees.

Provenance test: A replicated field trial comparing theperformance of trees grown from seed collectedfrom different parts of a species’ geographic range.

PSP plots (Permanent Sample Plots): permanent plotsthat have been set up throughout the plantationestate, to provide growth information for thenational database on the plantation resource.

Resistance: The relative ability to repel or endure pestsor other damaging influences. It may vary in degreefrom immunity, in which the attack or influenceis completely without effect to absolutesusceptibility, which may result in death.

Sapwood: The outer layers of a tree trunk, which representliving cells and conduct water up the tree, boundedby the cambium on the outside and heartwood inthe inside. Generally lighter in colour thanheartwood, and non-durable.

Sarking: Internal roof panelling.

Sawlog: A log that meets standards for diameter, lengthand defect, which is intended for sawing.

SED: The small-end diameter of a sawlog.

Seedlot: A collection of seeds, usually of known source.

Seed orchard: A plantation of selected trees, establishedand managed primarily for the early and abundantproduction of genetically improved seed. The seedorchard is isolated to reduce pollination fromoutside sources, and trees with undesirablecharacteristics are removed, based on ongoingevaluations.

Seed stands: A well-grown stand of trees, with goodgrowth and form, selected and managed forabundant seed production.

Seed stratification: A treatment given to seed to breakdormancy and improve germination, which usuallyinvolves a moist chilling.

Shelterbelt: A strip of trees established to shelter farm-or horticultural land from prevailing winds.

Site index: A measure of forest site quality expressed asthe average height (actual or potential) in a specificstand of trees, at a specific age (40 years forredwood in New Zealand, 100 years for redwoodin the USA).

Standing volume: The total volume of harvestable treesin a stand.

Stocking: The number of trees in a given area of a stand.

Tissue culture: (syn. micropropagation) Growing plantletsfrom small pieces of plant material on artificialmedia in a sterile, laboratory environment.

Tree improvement: Often equated with tree breeding, itincludes species choice and provenance selection,but may also refer to breeding in combination withcultural practices, particularly propagation.

Veneer: A thin sheet of attractive wood, used to coverwood of lesser value.

Vegetative propagation: (syn. vegetative multiplication)Multiplication of plants via asexual means, i.e.without sexual reproduction. Includes tissue culture,rooted cuttings, and grafting.

Virulence: The ability of an organism to cause disease.

56

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