even aged silviculture in asia

7/25/2019 Even Aged Silviculture in Asia

1/6

on re-

)actson the residualor-

historicalecordsndre-

searchuggestshatncertainircumstances

shelterwoodystemsndheir ariantshat

provideothtructuralnd ge-classiver-

sity an e ppropriate.e ive xamplesf

suchystemsn ndia,ri anka,nd

Malaysia.

By Mark S.Ashton

and Charles M. Peters

henorestersirstontem-

lated he silviculture f

complexmoist tropical

forests,heir first mpulsewas o re-

placehechaos ith pureplantations,

a method heyhad earnedrom the

reforestationf treelessuropeanands

thathadbeen egradedycenturiesf

grazing nd farming. his approach

hasworkedairlywellunder avorable

siteconditionsn the moist ropics,

but only where natural orests ad

beenvirtuallyeliminated y human

useor sitepreparation.he opportu-

nity costs f such ands n Asia oday

seldomavor orestry.

In the 19thandearly 0thcentury,

tropical ilviculturerew ts first oots

in South Asia and to a lesser extent in

FrancophoneCentral Africa and

British West and East Africa. At the

same ime, North America was under-

going epeatedaves fforest xploita-

tion from east o west. n the 1850s the

Indian Forest Service was founded

under the direction of Sir Dietrich

Brandisn responseo overexploitation

of high-qualityimbers, articularly

teak. n hisclassic ork on initiating

forestryn British ndia, Brandis e-

scribedhepotentialirectionorsilvi-

culturalesearch,ncluding focus n

nontimberorest roducts,armand

village ubsistencerops, ndcommu-

nity orests,swellas hehigh-quality

timbers Brandis 897).

Although orestry ndsilviculture

researchtartedn regionshat were

largely xploitedor orest roductsy

colonialgovernments,he establish-

mentof a rudimentaryocalmanage-

ment and research infrastructure en-

sured ome mphasisn thedevelop-

mentof sustainableorestry ractice.

These institutions have lasted to this

day in many South and Southea

Asiancountries--along ith all the

administrative foibles of the time A

wealth f gray iteraturerom his e

search assince ccumulatedn jour

nals, esearchecords,nternaleport

andunpublished anuscripts.ve

thesitespecificityf muchof thisma

terial, herearenow argedifferenc

among egions nd countriesn the

tropicsegardingheecologicalndsfi

vicultural nowledgease or fores

management.orexample, ost rop

ical forest egionsn the Neotrop

and Central Africa have little or no m-

formationcomparedo SouthAs

(India and Sri Lanka)and partso

Southeastsia Malaysia).

Muchof this ilviculturalnowled

has been documented in a form that is

notwidely ccessible,orne utby the

lackof acknowledgmenthisworkre

ceivesrom ontemporaryesearchern

tropicalorestmanagement.oday or

esters and researchers envision most

Asianropicalorestsshaving alanc

uneven-agedtands,ndasbeingman

aged ccordingly,lmosto heexclusi

of anyotherapproach.nfortunate

manyof the mistakes adewith un

even-agedilviculturen tropical sa

the turn of the centuryWyatt-Smi

1963)have eenorgotten,ndasa re

suitarebeing epeated.hispaper t

temptso clarify ome f themore uc

cessfulttemptsteven-agedilvicultu

and theirvariations ith several g

classesdouble-cohort)n moistropic

forestsfAsia, rawingn examples

historicalwork relevant o current issue

in tropicalorest anagement.

SelectiveLogging

The term selective was first coined

to describehepartial utting f wes


2/6

ern North American orests uring

their irstperiods f exploitation,nd

before markets for lessvaluable timbers

had developedHawley 1935). The

term is also used to describe the various

policiesf selectivityhatextend ver

whole range of concerns or lack

thereof) boutong-term anagement

of thestand.n thepast30 years, se-

lective asbeen ntentionally sed n

Southeastsia o describeepeatedi-

ameter-limituttings t cyclicalnter-

vals, so-called polycyclic fellings

(Whitmore 1990). Planned intervals

between ntriesnto the forest ange

from 15 to 30 years, ased n the as-

sumption hat the removal f large

canopy rees utomaticallyeleasesx-

isting eedlingsndsaplingsf diftr-

ent sizesandby implication ifferent

ageclasses)o form balanced,ll-sized

stands Smith et al. 1997).

Since he 1980s hese ystemsave

been outed n tropical siaasan eco-

logical arvestingegimehat, f prop-

erlydone, anhave low mpact n the

remainingrowing tock ndcanpro-

mote the foreststructure size-classis-

tribution)and dynamic hat manyof

these orests re perceivedo have

(Pinard et al. 1995; Pinard and Putz

1996; Primacket al. 1987a, b). These

systemslsohavegreatpoliticaland

commercialupporton public ands:

entriesntoa foresthatareguided ya

diameter-limit utting o extract he

largestrees enerateargenitial inan-

cialreturns Howardet al. 1996). n ad-

dition,highdiscountates avor re-

ductionn the ength f the elling ycle.

ularuneven-agedystems

(multiple-cohort)n parts

of Germany ndJapan t-

test (Smith et al. 1997).

Hature'$ Bookkeeping

The less omplexhestandmixture

the easiert is to recordmixturedy-

namics,s hesimplemixturesf rreg-

Thoughwidely ppliedn

the tropics,hereare ew

examplesof successful

selection regeneration

methodsor moist ropi- -:.

cal forests in Asia. Most ....

documentedxamples

have been indigenous

'tree arden ystemshat e

arehighlyaborntensive,_

.somuchso hat tending

isalmost t the ndividual '

treeevel.heseystems

representalmost com-

pleteanalogs f natural

self-thinningprocesses.

But because human val-

uesdrivetreespeciese-

lection, hese ystemsre

usually mployedn smallstandshat

havebeenownedand passed own

from individual to individual within

communitiesr families, longwith

considerablenowledgef thesystem

itself for example, adoch ndPeters

1993; Pelusoand Padoch 1996). The

most uccessfulneven-agedelection

systemsocumentedn Asiaareprac-

ticedby smallholderswho are more

concerned ith annual ields f non-

timber orest roductshanwith pro-

ducing reliable,ong-term upply f

sawlogs.

It is still too early o tell whether

thesesystems an be practical nd

commerciallyiable n a large cale.t

isunlikely hatcommercialnterprises

will beable o generatenough rofit

from imber lone, o heymust ry to

capture ufficient ervice alue rom

recreation, arbonsequestration,r

A community orest managedunder a single ree

selectionsystem tembawang) n West Kalimantan,

Indonesia.More than I O0 species er hectare are

managed n these tree garden systems.All trees

shown are valuable timber or nontimber resources.

water o gaineconomiceturns.

For largercommercial perations,

thecontinuous onitoring nd end-

ingof uneven-agedtandsanbeprob-

lematic. his primarily elateso un-

derstandinghediameter istributions

of the otalstand,he ndividualopu-

lations hat composet, and hesize-

specificates f growthof individual

trees. he shape f diameter istribu-

tionsof manv ainforestsn tropical

Asia have been characterized as a re-

verse (Whirmore 990). Likemany

other regions O'Hara 1998), re-

searchersn Asian ropicalorestsave

associatedhereversesize lass istri-

butionwithall age lasseseing epre-

sented quallywithin a stand.How-

ever, his s not necessarilyelated o

age-classistribution s s frequently

assumed, with the small individuals

being oung nd he arger nes ld.


3/6

B

Diameterat breastheight

A

B

C

Figure I. Static stratifica-

tion. Top:A profile of a

mature (more than I O0

yearsold) mixeddiptero-

carp stand,Sinharaja

Forest, Sri Lanka.

Below:A simplifieddiame-

ter distribution for the

species ominantscorre-

sponding o the profile.

The profile comprises

Shoreamegistophylla

(Acanopy and emergent

tree),

{;arcinia hermoni

(Bmsubcanopyree),

Humboltia laurifolia

(C-a small ree of the

understory),and

Agrostistachys ookeri

(D--groundstoryshrub).

The species isted corre-

spondapproximately n

growthhabit to northern

red oak, sassafras, ron-

wood, and witch hazel,

respectively.

Speciesithdifferent rowthateshat

occupy ifferent tratawithin he for-

est (groundstory,nderstory, ub-

canopy, anopy, mergent) anall be

thesame ge ndstillhave combined

diameterdistributionof a reverse .

This common henomenonasbeen

documentedn mixedmoist emperate

standshatareeven-agedOliverand

Larson1996; Smith et al. 1997).

Conceptually,wospeciestratifica-

tion processesan contributeo the

creation f a reverse for even-aged

stands.he firstprocessncludeshose

long-livedpecieshatoccupyifferent

vertical strata within a mature forest

stand. We refer to this as static strat-

ification even hough he processc-

tually sdynamic)fig.1), withunder-

story peciesepresentingmaller nd

more numerous diameters than the

true canopyand emergentspecies.

Strong tatic tratificationould eex-

hibitedwhen reemixtures ith very

different growth habits grow inti-

mately ogether. temperatexample

wouldbe a mixture omprisingitch

hazel (understory hrub), ronwood

I 2 3

A

B

C

Diameterat breastheight

Figure . Dynamic tratification.Left:A photographic rofileof a 15-year-oldmixeddipterocarp tand n stemexclusion

phase, inharaja orest, ri Lanka.Thephotograph rovides snapshot f an earlyphase f standdevelopment ith the

pioneer/acaranga eltata (A) in the canopy,mid-seralShorea rapezifolia B) in the subcanopy,nd ate-seralShorea

megistophyllaC) in the understory. hespeciesistedare approximately quivalent n light tolerance o paperbirch,

northernred oak,and sugarmaple, espectively.peciesepresentative f truly below-canopyrowthhabits those hat

comprise he different static strata in a mature stand)are alsopresent n the understorydepicted n this photograph.

Iight:A simplifieddepictionof the hypotheticalchange n diameter distributions or the tree specieshat attain the

canopy t early,middle, nd ate phases f standdevelopment I-stem exclusion tageat I S years;2--stemexclusion

stageat about 45 years; ---understory nitiation stageat about 80 years).

16 November 1999


4/6

(understoryree), assafrassubcanopy

tree), ndoak canopyree).

The secondrocessnvolvespecies

of different developmental tatus

(Swaineand Whitmore 1988) that se-

quentiallygain dominance f the

canopy ith all speciesriginatingr

being eleasedogetherollowing n

initialdisturbance.temperatexam-

plewouldbewhere in cherry ttains

the canopyof the mixtureearly n

stand evelopment,ut itspositionn

the canopys usurpedirst by black

birchand henby redoak.We call his

processdynamic tratification_fig.

2). Bothstratificationrocessesccur

togetherver hecoursef stand evel-

opmentollowingnitiation, tem x-

clusion,understoryeinitiation,and

old-growth hases s described y

Oliver and Larson 1996).

The majorityof the canopy asal

area n Asian ropical orestss repre-

sented y ree pecieshatare elatively

shade-intolerantnd hatproducee-

riodic arpetsf advanceegeneration

at the orest roundstorysa result f

mast ruiting. he advanceegenera-

tionof some f these pecies aysur-

vivebeneathdosedorest anopyor

more han 15 years, ut mostsurvive

no more hanoneor two yearsLiew

andWong1973;Ashton t al. 1995).

In all caseshe egenerationnlysatis-

factorily stablishesfter eleaseroma

disturbance.

Shelterwoods or Regeneration

The shelterwoodethod f regen-

eration can be defined as a set of silvi-

culturalmanipulationspplied t the

scale of the stand and focused toward

establishing dvance regeneration

when bsentt the orest roundstory,

and hen eleasinghis egenerations

a single ohort nce t ispresent.

The use of various kinds of shelter-

woods s a silviculturalegeneration

method n Asiahas argely een g-

nored,mostly ecausef our concern

for what we think forest structure

shouldook ike.Selectivelyakinghe

largest, ost aluablerees--a esirable

practiceconomically--iserceiveds

compatibleithminimizingamageo

the remainingorest tructure. ow-

ever,maintainingorestproductivity

andensuring ontinued evelopment

over ime s far more mportanto the

issue of sustainable silviculture than is

appearance.xpanding ur apprecia-

tionof forest evelopmentroma single

canopyap o the evel f a standor i-

nancial ndmanagementurposesn-

evitablyuggestsheuse f shelterwood

regeneration ethods. he develop-

mentanduseof such ystemsn South

andSoutheastsiahasa longhistory

andprovidesstrongaseor heir u-

turedevelopmentndpromotion.

As with any silvicultural ystem,

there are constraints to the use ofshel-

terwoods. his methodcan only be

practiceduccessfullyn stands ith

highmerchantableolumesf valuable

timber > 40 m3perhectare)hathave

diversifiedmarkets,which enablessil-

vicultural treatments to be done at a

profit.Shelterwoodsremostsuitable

for ensuringhe establishmentnd

then eleasef advanceegenerationn

forestshat havecanopydominants

thatmast, nd hus equire ubstantial

increasesn light for regeneration

growth.Examplesf simple ystems,

where dvanceegenerationxists e-

fore inalcanopyemoval,re heone-

cut shelterwoodsuchas the Malay

UniformSystemor Shoreaeprosula

and DryobalanopsromaticaWyatt-

Smith1963); hesystemdoptedor

Dipterocarpuseylanicustandsn low-

land southwest Sri Lanka (Holmes

1957);and heoverstoryemoval ys-

temadoptedormoist al orestsS. o-

busta) n Uttar Pradesh,ndia (Joshi

1980).Thesesystemsavebeensuc-

cessfuln large artbecauseheseor-

est ypes redominated y oneor two

light-demandingimberspecieshat

regenerate rolifically.Such forest

types reusuallyestrictedo the flat

lands nd erraceslong ivers, nd o

coastal lowlands of the Asian moist

tropics. heseands realso hemost

susceptibleo clearanceoragriculture

becauseheirsoils re ertile ndeasy

to work.

The inadequateepresentationf

advance egenerationn the more

fioristicallyomplex plandsf tropi-

cal Asia ed to developmentf more

classical shelterwoods and their vari-

ants, ndaway romone-cut ystems.

Classical helterwoodsurposefully

ensurestablishmentf advanceegen-

A one-cut shelterwood that released

advanced egeneration f dipterocarp

trees n lowlandmixeddipterocarp

forestat SungelMenyala,Malasia.he

advanced egenerationwaswell estab-

lished, llowing he overstoryo be re-

moved n one cutting operation. When

this photographwas aken the released

advanced egenerationhad createda

new even-aged tand that wasnow 30

yearsold and was n the stemexclusion

stage Oliverand Larson1996).

eration before overstory removal

through variety f preparatorynd

establishment treatments to the forest

stand.Both uniform and irregular

shelterwoodystemsavebeendevel-

oped or theAndamansChengappa

1944), Western Ghats (Kadambi

1954),andcurrentlyn southwestri

Lanka Ashtonet al. 1993). For Chen-

gappa'systemn theAndamans,he

understorysgraduallyifted n a series

of preparatoryndestablishmentut-

tings hat allowadvanceegeneration

to first stablishnd hengrow o pole

sizes efore anopy verstoryemoval.

For heWestern hat orestsf Coorg,

the partial emoval f the overhead

canopy nd he completeemoval f

the understorys necessaryo secure

regeneration,fterwhich heremoval

of theremaininganopyreessneces-

sary.n southwestriLankahedegree

of ntensityf canopyemovalhanges

with topographicosition. uch ys-

temscater o morevaried anges f

species hade olerance, nd to the

Journal f Forestry 17


5/6

Thisphotograph rom a Sri LankanForestReservellustrates he nature of the

ridge-valley opographyof uplanddipterocarp orests n Southand Southeast

Asia. n this instance he whole slopehasbeenregeneratedwith an irregular

shelterwood.The numberof reserves etained n the overstory ncreases ith

stands hat progress pslope rom valley o ridge.Thiswasdone o accommodate

the regeneration f more shade-tolerantdipterocarpspecies n the ridge as

compared o thosespeciesn the valley.Thevalleystandcan be considered n

overstory emoval;he midslope nd ridgestandshaveapproximately 5 percent

and 50 percent, espectively,f the basal rearemaining s reserves. hesubcanopy

of all the standshasbeen emoved.The released egeneration s now I 5 yearsold.

The reservesn the two-cohort standsof the midslopeand ridge are intended o

be removed at the end of the next rotation.

changesn siteproductivityndspecies

compositionssociatedith the topo-

graphicomplexityf upland ills.

Integrity Equals ncome

By definition helterwoodsreate

large-scaleisturbancendsimplifyhe

age-classistributionndstructuref a

stand. Observations of shelterwood aes-

thetics fter ecenteleasenlyaccentu-

atepeople'sislikeor such ystems.t

is mportanto pointout,however,hat

shelterwoodsrovide moreuniform

crown anopy nvironmenthat acili-

tates elf-thinningndmoveshestand

through he stem-exclusionhasea

critical eriodorspeciesorting) ith-

out esidualamageausedyperiodic

intrusionsrom electiveogging.elec-

tive ogginganpromoteignificantn-

vironmentalamage,articularlyhen

economicustificationsremade o re-

duce elling ycles ndhencencrease

repeatedncursionsnto thestand hat

disruptstanddevelopment.reated

stands n shelterwood ystems re

thereforeess usceptibleo theoppor-

tunistic inegrowth ndchronic up-

pressionof regenerationrom in-

growth f older ge lasses,hich ro-

vides normousdvantagesn allowing

canopy orting f complexmixtures

over brief, lbeit nsighdy,eriod f

early tand evelopment.

Facilitatinghe eleasef specificge

classesanpermit hecapturef other

resources,such as nontimber forest

products,hat maturesequentiallys

partof thedevelopmentf thesetands.

Forexample,n SriLankawehave een

exploringhecultivationf cardamom

(Elletaria nsal), fastgrowing erb

whoseruit canbe harvestedor spice

during he irst iveyears ftercanopy

removal; attan (Calamus hwaitesii),

climbingalm hatascendsith hede-

veloping anopy n stem exclusion

phasend anbeharvestedor urniture

andbasketryfter15 years: ndkitul

(Caryota rens), subcanopyalmof

18 November 1999

the oresthatcanbe appedorsyrup

afterabout 0 years.Whencombined,

thesenontimber orestproducts an

double the income from a stand man-

aged n a shelterwoodystemhat s

primarilymanagedor timberalone

(Ashtonet al. 1999).

Conclusion

In the right circumstances,ven-

aged ilvicultureanmakebiological

and economic sense.All too often sil-

viculturistsnd ecologistsaveslav-

ishly mitatedhescalesf disturbance

that natureuses, ven hough hese

maybe ogisticallympossibleo repli-

categiven hekindof machinerynd

economieshatwe have oday. fresh

perspectivendbetter nsights bout

stand ynamicsn tropicalorestsften

lead o more conomicalndbiologi-

cally ompatibleilviculturalystems.

This perspectiveill becomencreas-

ingly mportantn futuremanagement

scenarios hen tropical orests re

mostly restricted o uplands,with

landshataremarginalor agriculture

andplantationrops, here osts ill

be minimized, ndmultiple alues f

productstimber,uel,nontimberor-

estproducts)ndserviceswater,ecre-

ation)must egarneredrom hesame

forest stand to make the whole forest

economicallyiable.

Some of the environmental services

(such swater) arneredromupland

forests ightappearo be ncompati-

ble with the useof shelterwoodys-

tems. his apparent ontradictione-

serves ome larification.We empha-

size he mportancef careful nalysis

in trade-offs between one-time severe

incursions,ollowed y roadand rail

abandonment roads are a major

source f erosion), scomparedo re-

peated ut less everencursionshat

rely on a permanent nd expansive

road and trail network.

Severalessons upportmanage-

mentof tropicalorest tandsn even-

agedmixtures.orexample,henotion

thatdifferent peciesanbe reated s

if theywere f different ge assesim-

ply does ot fit thewaymixed tands

developecausef interspecificiffer-

encesn rates f heightgrowth.Pre-

tendinghat the ow-value peciesn

the subcanopy re young growing


6/6

Carota urens

A--kitul palm

Calamus eylanicus

B--climbingpalm

Elletaria ensal

C---understory erb

cardamom

stockmay educe osts, ut t does ot

truly release dvance egeneration.

This phenomenonings amiliar o

forestersn North America,wheresim-

ilar essonsere earned bout pecies

mixturesn the temperate ixedoak

forestsof the east Oliver and Larson

1996; Smith et al. 1997; Miller and

Kochenderfer 998; O'Hara 1998).

Theshelterwoodrinciplefrelying

on advanceegenerationnsureshat

thestand lways asplantsn placeo

ward ffusurpationyexplosionsf n-

vasive ioneer pecieshatcanexclude

regenerationf timber peciesfter hey

have been eliminated. In the end, it is

easier ndcheapero ridealongwith

the endenciesf natural tand ynam-

ics n which hevaluableanopyree

speciesontinueo triumph.

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Mark S. Ashton e-mail:mark. shton@

yale. du) sagociateroj$ssorfsilvicul-

ture, choolfForestryndEnvironmen-

talStudies,ale niversi{y,ewHaven,

CT 06511; CharlesM. Peterss research

scientist,nstitute fEconomicotany,

New IOrk Botanical Garden, Bronx,

New IOrk.

Journal f Forestry 19

even aged silviculture in asia

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