day in many South and Southeast
platedthe silvicultureof Asiancountries--along
with all the
complexmoist tropical administrative foibles of the time A
forests,their firstimpulsewasto re- wealthof grayliterature
fromthisreplacethechaos
withpureplantations, search
hassinceaccumulated
in jouron rea methodtheyhad learnedfrom the nals,research
records,
internalreports,
)actson the residual
forreforestation
of treeless
European
lands andunpublished
manuscripts.
G•ven
thathadbeendegraded
bycenturies
of thesitespecificity
of muchof thismahistorical
records
andregrazingandfarming.This approach terial,therearenowlargedifferences
search
suggests
thatincertain
circumstances
hasworkedfairlywellunderfavorable amongregionsandcountries
in the
shelterwood
systems
andtheirvariants
that
siteconditions
in the moisttropics, tropicsregarding
theecological
andsfiprovide
both
structural
andage-class
diver- but only wherenaturalforestshad viculturalknowledge
basefor forest
sitycanbeappropriate.
Wegive
examples
of
beenvirtuallyeliminatedby human management.
Forexample,
mosttropsuch
systems
inIndia,
SriLanka,
and
useor sitepreparation.
The opportu- icalforestregionsin the Neotrop•cs
Malaysia.
nity costsof suchlandsin Asiatoday and Central Africa have little or no mseldomfavorforestry.
formationcomparedto SouthAs•a
In the19thandearly20thcentury, (India and Sri Lanka)and partsof
tropicalsilviculture
grewits firstroots Southeast
Asia(Malaysia).
By Mark S.Ashton
in South Asia and to a lesser extent in
and Charles M. Peters
Muchof thissilvicultural
knowledge
FrancophoneCentral Africa and has been documented in a form that is
British West and East Africa. At the
notwidelyaccessible,
borneoutby the
sametime, North Americawas under- lackof acknowledgment
thisworkregoingrepeated
waves
offorestexploita- ceives
fromcontemporary
researchers
on
tion from eastto west. In the 1850s the
tropical
forestmanagement.
Todayfor-
hen
foresters
first
contem-
Indian Forest Service was founded
under the direction of Sir Dietrich
esters and researchers envision most
Asiantropical
forests
ashaving
balanced
Brandis
in response
to overexploitationuneven-aged
stands,
andasbeingmanof high-qualitytimbers,particularly aged
accordingly,
almost
totheexclusion
teak.In hisclassic
workon initiating of anyotherapproach.
Unfortunately,
forestryin BritishIndia, Brandisde- manyof the mistakes
madewith unscribed
thepotential
direction
forsilvi- even-aged
silviculture
in tropical
As•aat
culturalresearch,
including
a focuson the turn of thecentury(Wyatt-Smith
nontimberforestproducts,
farmand 1963)havebeenforgotten,
andasa revillagesubsistence
crops,andcommu- suitarebeingrepeated.
Thispaperatnityforests,
aswellasthehigh-quality temptsto clarifysomeof themoresuctimbers(Brandis1897).
cessful
attempts
ateven-aged
silviculture,
Althoughforestryandsilviculture and theirvariations
with several
age
research
startedin regions
thatwere classes
(double-cohort)
in moisttropical
largelyexploited
forforestproducts
by forests
ofAsia,drawing
onexamples
of
colonialgovernments,
the establish- historicalwork relevantto current issues
mentof a rudimentary
localmanage- in tropical
forest
management.
ment and research infrastructure en-
suredsomeemphasis
on thedevelop- SelectiveLogging
The term "selective"was first coined
mentof sustainable
forestrypractice.
These institutions have lasted to this
to describe
thepartialcuttingof west14
November 1999
ern North Americanforestsduring ularuneven-aged
systems
theirfirstperiods
of exploitation,
and (multiple-cohort)
in parts
before markets for lessvaluable timbers
of GermanyandJapanathad developed(Hawley 1935). The test (Smith et al. 1997).
term is also used to describe the various
Thoughwidelyappliedin
policies
of selectivity
thatextendovera thetropics,therearefew
whole range of concerns(or lack examplesof successful
thereof)aboutlong-term
management selection regeneration
of thestand.In thepast30 years,"se- methodsfor moisttropi-:.,
lective"hasbeenintentionally
usedin cal forests in Asia. Most
Southeast
Asiato describe
repeated
di- documented
examples
ameter-limit
cuttings
at cyclical
inter- have been indigenous
vals, so-called polycyclicfellings '•tree
garden"
systems
thate
....
(Whitmore 1990). Planned intervals
arehighly
laborintensive,
•_
betweenentriesinto the forestrange
from 15 to 30 years,basedon the assumptionthat the removalof large
canopytreesautomatically
releases
existingseedlings
andsaplings
of dift•rentsizes(andby implication
different
ageclasses)
to formbalanced,
all-sized
.somuchsothattending=
stands(Smith et al. 1997).
uesdrivetreespecies
se- shown are valuable timber or nontimber resources.
lection,thesesystems
are
usuallyemployed
in smallstandsthat waterto gaineconomicreturns.
havebeenownedand passed
down
For largercommercial
operations,
from individual to individual within
thecontinuous
monitoring
andtendcommunities
or families,alongwith ingof uneven-aged
stands
canbeprobconsiderable
knowledge
of thesystem lematic.This primarilyrelatesto unitself(forexample,
PadochandPeters derstanding
thediameter
distributions
1993; Pelusoand Padoch 1996). The
of thetotalstand,theindividual
popumostsuccessful
uneven-aged
selection lationsthatcompose
it, andthesizesystems
documented
in Asiaareprac- specificratesof growthof individual
ticedby smallholderswho are more trees.The shapeof diameterdistribuconcerned
with annualyieldsof non- tionsof manvrainforests
in tropical
timberforestproducts
thanwith pro- Asia have been characterized as a reducinga reliable,long-termsupplyof verseJ (Whirmore1990). Likemany
sawlogs.
other regions(O'Hara 1998), reIt is still too earlyto tell whether searchers
in Asiantropicalforests
have
thereverse
J sizeclass
distrithesesystems
can be practicaland associated
commercially
viableona largescale.It butionwithallageclasses
beingrepreisunlikelythatcommercial
enterprises sentedequallywithin a stand.Howwill beableto generate
enough
profit ever,thisis not necessarily
relatedto
fromtimberalone,sotheymusttry to age-class
distributionasis frequently
capturesufficientservicevaluefrom assumed, with the small individuals
recreation,carbonsequestration,
or beingyoungandthelargeronesold.
Sincethe 1980sthesesystems
have
beentoutedin tropicalAsiaasan ecological
harvesting
regime
that,if properlydone,canhavea lowimpactonthe
remaining
growing
stockandcanpromote the foreststructure(size-class
dis-
tribution)and dynamicthat manyof
theseforestsare perceivedto have
(Pinard et al. 1995; Pinard and Putz
1996; Primacket al. 1987a, b). These
systems
alsohavegreatpoliticaland
commercial
supporton publiclands:
entries
intoa forestthatareguided
bya
diameter-limit
cuttingto extractthe
largest
treesgenerate
largeinitialfinancialreturns(Howardet al. 1996). In ad-
dition,highdiscount
ratesfavora reduction
in thelength
of thefellingcycle.
Hature'$ Bookkeeping
The lesscomplex
thestandmixture
the easierit is to recordmixturedynamics,
asthesimple
mixtures
of irreg-
isalmostat theindividual•'
tree
level.
These
systems
•
representalmost com- A communityforest managedunder a singletree
pleteanalogsof natural selectionsystem(tembawang)in West Kalimantan,
self-thinningprocesses.Indonesia.More than I O0speciesper hectareare
But because human val-
managedin these"tree garden"systems.All trees
Journalof Forestry
A
B
Species
withdifferent
growthratesthat
occupydifferentstratawithintheforest (groundstory,
understory,subcanopy,canopy,
emergent)
canall be
thesameageandstillhavea combined
diameterdistributionof a reverseJ.
This commonphenomenon
hasbeen
documented
in mixedmoisttemperate
standsthatareeven-aged
(Oliverand
Figure I. Static stratification. Top:A profile of a
mature (more than I O0
yearsold) mixeddipterocarp stand,Sinharaja
Forest, Sri Lanka.
Below:A simplifieddiameter distribution
C
for the
Larson1996; Smith et al. 1997).
speciesdominantscorrespondingto the profile.
The profile comprises
Shoreamegistophylla
(A•canopy and emergent
tree),
{;arcinia
Conceptually,
twospecies
stratification processes
cancontributeto the
creationof a reverse
J for even-aged
stands.
The firstprocess
includes
those
long-lived
species
thatoccupy
different
vertical strata within a mature forest
stand. We refer to this as "static" strat-
hermoni
(Bmsubcanopy
tree),
Humboltia
laurifolia
ification(eventhoughtheprocess
actuallyisdynamic)(fig.1), withunderstoryspecies
representing
smallerand
(C-•a smalltree of the
understory),and
Agrostistachysbookeri
(D--groundstoryshrub).
The specieslisted correspondapproximatelyin
growthhabit to northern
B
more numerous
red oak, sassafras,iron-
respectively.
I
than the
true canopyand emergentspecies.
Strong
static
stratification
wouldbeexhibitedwhentreemixtureswith very
differentgrowth habits grow intimatelytogether.
A temperate
example
wouldbea mixturecomprising
witch
hazel (understoryshrub),ironwood
wood, and witch hazel,
Diameterat breastheight
diameters
2
3
A
B
C
Diameterat breastheight
Figure2. Dynamicstratification.Left:A photographicprofileof a 15-year-oldmixeddipterocarpstandin stemexclusion
phase,SinharajaForest,SriLanka.Thephotographprovidesa snapshotof an earlyphaseof standdevelopment
with the
pioneer/•acarangapeltata (A) in the canopy,mid-seralShoreatrapezifolia(B) in the subcanopy,
and late-seralShorea
megistophylla
(C) in the understory.
Thespecieslistedare approximatelyequivalentin light toleranceto paperbirch,
northernred oak,and sugarmaple,respectively.
Speciesrepresentative
of truly below-canopy
growthhabits(thosethat
comprisethe different"static"strata in a mature stand)are alsopresentin the understorydepictedin this photograph.
I•ight:A simplifieddepictionof the hypotheticalchangein diameterdistributionsfor the tree speciesthat attain the
canopyat early,middle,and late phasesof standdevelopment( I-•stem exclusion
stageat I Syears;2--stemexclusion
stageat about 45 years;3---understoryinitiation stageat about 80 years).
16
November 1999
(understory
tree),sassafras
(subcanopyovertimeisfarmoreimportantto the
issue of sustainable silviculture than is
tree),andoak(canopy
tree).
The second
process
involves
species appearance.
Expandingour appreciadevelopment
froma single
of different developmental
status tionof forest
(Swaineand Whitmore 1988) that se- canopy
gaptothelevelofa stand
forfiquentiallygain dominanceof the nancialandmanagement
purposes
incanopy
withall species
originating
or evitably
suggests
theuseof shelterwood
beingreleased
togetherfollowingan regeneration
methods.
The developinitialdisturbance.
A temperate
exam- mentanduseof suchsystems
in South
plewouldbewherepin cherryattains andSoutheast
Asiahasa longhistory
the canopyof the mixtureearlyin andprovides
a strong
casefortheirfustanddevelopment,
but itspositionin turedevelopment
andpromotion.
the canopyis usurpedfirst by black
As with any silviculturalsystem,
birchandthenbyredoak.Wecallthis there are constraints to the use ofshelThis methodcanonly be
process
"dynamic"
stratification
(_fig. terwoods.
2). Bothstratification
processes
occur practiced
successfully
in standswith
together
overthecourse
ofstanddevel- highmerchantable
volumes
ofvaluable
opmentfollowing
initiation,stemex- timber(> 40 m3perhectare)
thathave
clusion,understoryreinitiation,and diversifiedmarkets,which enablessilold-growthphasesas described
by vicultural treatments to be done at a A one-cut shelterwood that released
Oliver and Larson(1996).
profit.Shelterwoods
aremostsuitable advancedregenerationof dipterocarp
The majorityof the canopybasal for ensuringthe establishment
and trees in lowlandmixeddipterocarp
The
areain Asiantropicalforests
is repre- thenrelease
of advance
regeneration
in forestat SungelMenyala,Mala¾sia.
sented
bytreespecies
thatarerelatively foreststhat havecanopydominants advancedregenerationwaswellestabshade-intolerant
andthatproduce
pe- thatmast,andthusrequiresubstantial lished,allowingthe overstoryto be reriodiccarpets
of advance
regenerationincreases
in light for regeneration movedin one cutting operation.When
at theforestgroundstory
asa resultof growth.Examples
of simplesystems, this photographwastaken the released
mastfruiting.The advance
regenera- whereadvance
regeneration
exists
be- advancedregenerationhad createda
tionof someof thesespecies
maysur- forefinalcanopy
removal,
aretheone- new even-agedstand that wasnow 30
suchas the Malay yearsold and wasin the stemexclusion
vivebeneath
a dosedforestcanopy
for cut shelterwoods
morethan 15 years,but mostsurvive UniformSystemfor Shorea
leprosula stage(Oliverand Larson1996).
no morethanoneor twoyears(Liew and Dryobalanops
aromatica
(WyattandWong1973;Ashtonet al. 1995). Smith1963);thesystem
adoptedfor eration before overstory removal
In allcases
theregeneration
onlysatis- Dipterocarpus
and
zeylanicus
stands
in low- througha varietyof preparatory
factorily
establishes
afterrelease
froma land southwest Sri Lanka (Holmes establishment treatments to the forest
disturbance.
1957);andtheoverstory
removalsys- stand.Both uniform and irregular
temadopted
formoistsalforests
(S.ro- shelterwood
systems
havebeendevelbusta)in Uttar Pradesh,India (Joshi opedfor theAndamans
Shelterwoodsfor Regeneration
(Chengappa
havebeensuc- 1944), Western Ghats (Kadambi
Theshelterwood
method
of regen- 1980).Thesesystems
eration can be defined as a set of silviSri
cessful
in largepartbecause
thesefor- 1954),andcurrentlyin southwest
culturalmanipulations
appliedat the esttypesaredominated
by oneor two Lanka(Ashtonet al. 1993). For Chenscale of the stand and focused toward
light-demanding
timberspecies
that gappa's
system
in theAndamans,
the
establishingadvance regeneration regenerateprolifically.Such forest understory
isgradually
liftedin a series
whenabsent
at theforestgroundstory,typesareusuallyrestricted
to the flat of preparatory
andestablishment
cutandthenreleasing
thisregeneration
as landsandterraces
alongrivers,andto tingsthatallowadvance
regeneration
coastal lowlands of the Asian moist
a singlecohortonceit ispresent.
to firstestablish
andthengrowto pole
The use of various kinds of sheltertropics.
Theselandsarealsothemost sizes
beforecanopy
overstory
removal.
woodsas a silvicultural
regeneration susceptible
to clearance
foragriculture FortheWestern
Ghatforests
of Coorg,
methodin Asiahaslargelybeenig- because
theirsoilsarefertileandeasy the partialremovalof the overhead
nored,mostlybecause
of ourconcern to work.
canopyandthe complete
removalof
for what we think forest structure
The inadequate
representation
of the understory
is necessary
to secure
should
looklike.Selectively
takingthe advanceregeneration
in the more regeneration,
afterwhichtheremoval
largest,
mostvaluable
trees--adesirable fioristically
complex
uplands
of tropi- of theremaining
canopy
treesisnecespractice
economically--is
perceived
as calAsialed to development
of more sary.
In southwest
SriLankathedegree
compatible
withminimizing
damage
to classical shelterwoods and their variof intensity
of canopy
removal
changes
the remaining
foreststructure.
How- ants,andawayfromone-cutsystems. with topographic
position.Suchsysever,maintainingforestproductivity Classicalshelterwoods
purposefully temscaterto morevariedrangesof
andensuring
continued
development ensure
establishment
ofadvance
regen- speciesshadetolerance,and to the
Journalof Forestry 17
theforestthatcanbetapped
forsyrup
afterabout20 years.
Whencombined,
thesenontimberforestproductscan
double the income from a stand man-
agedin a shelterwood
systemthatis
primarilymanaged
for timberalone
(Ashtonet al. 1999).
Conclusion
In the right circumstances,
evenagedsilviculture
canmakebiological
and economic sense.All too often sil-
viculturists
and ecologists
haveslavishlyimitatedthescales
of disturbance
that natureuses,eventhoughthese
maybelogistically
impossible
to replicategiventhekindof machinery
and
economies
thatwehavetoday.A fresh
perspective
andbetterinsightsabout
standdynamics
in tropical
forests
often
Thisphotographfrom a Sri LankanForestReserveillustratesthe natureof the
leadto moreeconomical
andbiologiridge-valleytopographyof uplanddipterocarpforestsin Southand Southeast
callycompatible
silvicultural
systems.
Asia.In this instancethe wholeslopehasbeenregeneratedwith an irregular
This perspective
will becomeincreasshelterwood.The numberof reservesretainedin the overstoryincreaseswith
inglyimportant
in futuremanagement
standsthat progress
upslopefrom valleyto ridge.Thiswasdoneto accommodate scenarios
when tropicalforestsare
the regenerationof moreshade-tolerantdipterocarpspecieson the ridgeas
mostly restrictedto uplands,with
comparedto thosespeciesin the valley.Thevalleystandcanbe consideredan
landsthataremarginal
for agriculture
overstoryremoval;the midslopeandridgestandshaveapproximately25 percent
andplantation
crops,
wherecosts
will
and50 percent,respectively,
of the basalarearemainingasreserves.Thesubcanopy be minimized,andmultiplevalues
of
of all the standshasbeenremoved.The releasedregenerationis now I 5 yearsold.
products
(timber,fuel,nontimber
forThe reservesin the two-cohortstandsof the midslopeand ridgeare intendedto
estproducts)
andservices
(water,recrebe removed at the end of the next rotation.
ation)mustbegarnered
fromthesame
forest stand to make the whole forest
viable.
changes
in siteproductivity
andspecies standsin shelterwoodsystemsare economically
Some of the environmental services
composition
associated
with thetopo- therefore
lesssusceptible
to theopporfromupland
graphic
complexity
of uplandhills.
tunisticvinegrowthandchronicsup- (suchaswater)garnered
pressionof regeneration
from in- forests
mightappearto beincompatiIntegrity EqualsIncome
sysgrowthof olderageclasses,
whichpro- ble with the useof shelterwood
By definitionshelterwoods
createa videsenormous
deadvantages
in allowing tems.This apparentcontradiction
someclarification.
We emphalarge-scale
disturbance
andsimplify
the canopysortingof complexmixtures serves
of carefulanalysis
age-class
distribution
andstructure
ofa overa brief,albeitunsighdy,
periodof sizetheimportance
stand. Observations of shelterwood aesin trade-offs between one-time severe
earlystanddevelopment.
thetics
afterrecentrelease
onlyaccentufollowedby roadandtrail
Facilitating
therelease
of specific
age incursions,
atepeople's
dislikefor suchsystems.
It classes
canpermitthecapture
of other abandonment(roads are a major
to reisimportant
topointout,however,
that resources,such as nontimber forest sourceof erosion),ascompared
shelterwoods
providea moreuniform products,that maturesequentially
as peatedbut lesssevere
incursions
that
crowncanopyenvironment
thatfacili- partofthedevelopment
ofthese
stands. rely on a permanentand expansive
in SriLankawehavebeen road and trail network.
tatesself-thinning
andmoves
thestand Forexample,
throughthe stem-exclusion
phase(a exploring
thecultivation
of cardamom Severallessons
supportmanagein evencritical
periodforspecies
sorting)
with- (Elletariaensal),a fastgrowingherb mentof tropicalforeststands
for spice agedmixtures.
outresidual
damage
caused
byperiodic whosefruit canbeharvested
Forexample,
thenotion
canbetreatedas
intrusions
fromselective
logging.
Selec- duringthefirstfiveyearsaftercanopy thatdifferentspecies
tivelogging
canpromote
significant
en- removal;rattan (Calamusthwaitesii),a if theywereof different
agedasses
simvironmental
damage,
particularly
when climbing
palmthatascends
withthede- plydoesnotfit thewaymixedstands
economic
justifications
aremadeto re- velopingcanopyin stemexclusion develop
because
of interspecific
differducefellingcycles
andhenceincrease phase
andcanbeharvested
forfurniture encesin ratesof heightgrowth.Prerepeated
incursions
intothestandthat andbasketry
after15 years:andkitul tendingthatthelow-value
species
in
disruptstanddevelopment.
Treated (Caryota
urens),
a subcanopy
palmof the subcanopyare young growing
18
November 1999
Car•ota urens
A--kitul palm
Calamuszeylanicus
B--climbingpalm
Elletaria
ensal
C---understoryherb
cardamom
121-36.Oxford,
UK:Oxford
University
Press.
D. 1897.Indianj•restry.
London:
Empire
stockmayreducecosts,
butit doesnot BRANDIS,
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PINARD,
M.A.,andEE.PUTZ.
1996.Retaining
forest
truly releaseadvanceregeneration. CHENGAP?^,
B.S. 1944.The Andamanforests
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278-95.
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oftimberspecies
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