Download - Even Aged Silviculture in Asia
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7/25/2019 Even Aged Silviculture in Asia
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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
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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.
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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
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(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
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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
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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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