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DynamicsDynami

    Dynamics

May2008,Volume2,No.5(SerialNo.6)JournalofLifeSciences,ISSN1934-7391,USA

    ;Dynamicsoftreespeciesecologicalgroupsinloggedandunlogged ;tropicalforestsintheVenezuelanwesternplains

    ;RAMIREZ-ANGULoHirma.TORRESLEZAMAArmando

    ;(ResearchTeamBIODESUS,lnstitutodelnvestigacionesParaelDesarrolloForestal(1N

    DEFOR),FaculmddeCiencias

    ;ForestalesyAmbientales,UniversidaddeLosAndes,VfaLosChorrosdeMilla,Mdrida,Ve

    nezuela)

    ;Abstract:Thestudyoftreemortalityandrecruitment ;contributestotheunderstandingofforestdynamicsand,atthe ;sametime.suppliesabaselinetoevaluatetheimpactofhuman ;activities.Thestudysiteisamoistsemi.deciduousforest ;locatedintheCaparoForestReserve.Venezuela.Treedatawere ;obtainedfrompermanentplotsestablishedinunloggedand ;loggedstands.Successivemeasurementsweretakenduringa15 ;yrperiod.Treespeciesmortalityandrecruitmentwasanalyzed ;f0rindividualswithdiameteratbreastheight(d)10cm.The

    ;specieswereclassifiedaccordingtotheirshadetolerance(1owor ;intolerant.intermediateandhighortolerant)andthemaximum ;height(hmax)(small<15m,medium:15?30mandlarge>30m). ;Palmswereconsideredasaseparategroup.Intheunlogged ;stands307and274treeshawerefoundatthebeginningand

    ;finaltimeofthemonitoringperiod,respectively.Thesetrees ;wereclassifiedifito55and48species,respectively.Among ;thempredominatespeciesfromtheshadeintermediatetolerant ;andlargesizegroupandpalms.Similarly,intheloggedforest ;155and207treeshawerefound.whereas59and60tree

    ;specieswererecorded.Onlyfourspecieswerefoundwith>10 ;individualsha,themajorityofthesespeciesbelongtothe

    ;functionalgroupofshadeintolerantmediumsizespecies,which ;maybepartlyexplainedbyforestrecoveringafterselective ;logging.Intheunloggedstandsthemeanannu~rateoftree ;mortalityis2.61%andthehighestvaluesco~espondedtoshade ;intermediatetolerantandintolerantsmallsizespecies.Tree ;densitywasnotsignificantlycorrelatedtotreemortalityinboth ;forestconditions(1oggedandunlogged).Therecruitmentratein ;theunloggedforestwas1.33%.withthelowestvaluesobtained ;Acknowledgments:TheauthorwillthankJulioSerrano, ;PedroSalcedo,EmilioVilanova,JenniferPeruttiandJenny

    ;Rodr/guezfortheirvaluablefieldwork.Thisstudywas ;supportedbythe”ConsejodeDesarrolloCientffico,

    ;HumanisticovTecnol6gico.UniversidaddeLosAndes”

    ;(CDCHT-ULA).undertheProjectFO62406.01.B.

    ;Correspondingauthor:RarnffezAnguloHirma(1960),

    ;male.associateprofessor;researchfield:tropicalforest ;managementwithspecialemphasisonforestsdynamicsand ;modelling.

    ;forthesamegroupswithhighestmortality;whereasinthe ;loggedstandsreached2.58%.withthehighestvalueforthe ;shadetolerantsmallsizespecies,followedbyshade ;intermediatetolerantlargesizespecies.Asignificantdifference ;wasfoundbetweenforestconditionsfortreerecruitmentrates ;(H=0.0649).Incontrast,thecorrelationbetweentreemortality ;andrecruitmentwashigherforlogged(r=0.5988)thanunlogged ;stands(r=0.4904)butnotsignificant.

    ;Keywords:ecosystemdisturbance;recruitment;selective ;logging;treemortality;tropicalforest

    ;1.Introduction

    ;Thestudyoftreemortalityandrecruitment

    ;contributestotheunderstandingofforestdynamicsand, ;atthesametime,suppliesabaselinetoevaluatethe ;impactofhumanactivitiesonnaturalsystemst?. ;Speciescomposition,structureandforestdynamicscan ;bepartiallyexplainedbyprocessesthatgenerate ;mortalityandcreateconditionsthatshapesuccessional ;routesinaparticularway.Therefore,thehistoryofa ;foreststand,includingthetreemortalityprocessandits ;influenceonforestfunctioning,mustbestudiedin ;ordertounderstandvegetationdynamicsandbiomass ;turnoverrate2J.Muchofwhatisknownabouttropical

    ;forestdynamicscomefrompermanentplotsThese ;plotshavedifferentshapesandsizesandminimum ;diameterlimitsatbreastheight(d).Somestudies ;includepalms,lianasandshrubs,whereasothersonly ;considertreespecies.Severalcontributionssummarize ;theresultsoflongtermforestdynamicsinpermanent ;plots?”.

    ;Thesestudiesreportgreatvariabilityin

    ;specificmortality,recruitmentanddiametergrowth ;57

    ;Dynamicsoftreespeciesecologicalgroupsinlogg——

    ;e

    ;rateofspecies,whicharefrequentlyassociatedwith

    ;differencesinlifehistoryacrossacontinuumbetween ;earlyandlatesuccessionaltreesI”.

    ;Despiteallthis

    ;variability,thestudiesindicatethatchangesand ;fluctuationsinthestructureofmatureforestsfollowa ;patternforthetropicalzoneasawhole.Thereisa ;constancyofparameterssuchasdensity,basalareaand ;speciesnumber,fluctuatingwoundameanvaluealong ;time,whichismaintainedbytheexistenceofan ;adequatebalancebetweentreemortalityand ;recruitment[1.

    ;Inthemajorityofthelongtermstudiestree ;mortalityratehasbeenfoundtobeindependentfrom ;thediametersizeI?1.

    ;However.inforestswhere

    ;disturbancehavebeensevereduringthemonitoring ;periodahighermortalityratehasbeenobservedforthe

    .Thesedisturbancescancauseimportant ;largertrees6

    ;changesinmortalityandrecruitmentrates.Asimilar ;trendinahumandisturbedforestwasreportedin ;Malaysia[14I.

    ;Ontheotherhand,tropicalforestmanagement ;(TFM)hasbeencarriedoutstartingfromthepremise ;thattheseecosystemsareinadynamicsstate,where ;treefallsofmatureindividualsoccur.Nonetheless, ;usuallyotherelementsassociatedtologgingarenot ;considered.Thesefactorsinfluenceinsuchawaythat ;loggingdoesnotcloselyresembleforestdynamics ;causingseriousproblemsmanytimes.Oneofthemost ;importantfactorsinTFMistheforestrecoveryspeed ;inresponsetologging;thisresiliencewilldetermine ;ecosystemsustainability.Inthispaper,weanalyze ;mortalityandrecruitmentoftreespeciesfunctional ;groupsinloggedandunloggedforeststandsinahumid ;deciduousforestoftheVenezuelanwesternplains. ;2.Methodology

    ;2.1Studysite

    ;Thestudywascarriedoutontheresearchstation ;oftheCaparoForestReserve(CFR)intheVenezuelan ;westernplains(70~40’0”-71~02’00”E.

    ;58

    ;7.26’0O”7.36’00”N,ll0l40m.a.s.1.).’I’heclimateIS

    ;humidtropicalwithanannualmeanprecipitationof ;1750mm,airtemperatureof24.6.Candatmospheric

    ;humidityfrom59%(January)to89%(June)witha ;distinctdryseasonfromDecembertoMarcht15.

    ;Duetothemicroreliefandthedominanceof

    ;physiographycalunitinlowpositions,mostofthearea ;isinundatedduringtherainyseason.Theheightand ;durationofthesefloodingsisdeterminedbyrainfall ;intensity,physiographyandsoiltextureand

    . ;stratification[-

    ;Thevegetationshowsahighspatialvariability ;andvariesindegreeofdevelopmentfromlow(sabana ;andestero)toatallforestwhichreachesamaximumof ;35minheightl61.TheCaparoforestswereselectively ;loggedformahogany(Swieteniamacrophylla)and ;cedar(Cedrelaodorata)inthe1950st171;however,for ;thepurposeofthisstudywecallthemnotrecently ;loggedforestsorjust”unloggedforests”.

    ;2.2Datacollection

    ;TreedatawereobminedfromtwogroupsofNots ;establishedbytheInstitutodeInvestigacionesparael ;DesarrolloForestal(INDEFOR).Inthe1989.1990 ;period,plots1000minlengthand10minwidth(1ha) ;wereestablishedintwoforestconditions:areaslogged ;in1985andunloggedareas.Asystematicdesignwas ;usedtosamplethearea.In1991,athirdgroupof ;squareplots(0.25ha)wasrandomlyestablishedinthe ;unloggedarea.

    ;Foreachplotisknowntheforestcondition

    ;(1ogged,unlogged)andforeachtreewehavethe ;followingdata:totalandboleheightforthefirst ;measurement,bolequality,positioninthecanopyfor ;thefirstmeasurement,andeachoneofthe

    ;circumferencevaluesatbreastheightofthesoccessivc ;measurements.

    ;2.3Calculationoftreemortalityand

    ;recruitmentannualrates

    ;Treemortalityannualratewascalculatedby ;meansofthefollowingalgebraicmodel5J=

    ;.

    ;D

    ;....

    ;y...

    ;n

    ;....

    ;a

;...

    ;m

    ;.....

    ;i

    ;..

    ;c

    ;...

    ;s

    ;...

    ;m=l(Nl/No)”×100(1)

    ;Where:

    ;m:mortalityannualrate;

    ;No:numberofindividualsintheinitialsample; ;N1:numberofindividualsinthefinalsample; ;t:observationtimeinyears.

    ;Treerecruitmentwasconsideredasthenumberof ;individualsthatreachedtheminimumDBHOf10cm ;betweenmeasurements.Recruitmentrateswere ;calculatedwiththefollowingequationll8:

    ;R={[(No+r)/No]”t_1)×100(2)

    ;Where:

    ;risthenumberofrecruitedindividuals.excluding ;deaths,betweencensuses.

    ;Half-life(to5)oftreecommunities,definedasthe ;timerequiredfor50%ofthestemstodieassuminga ;constantmortalityprobability【】wereestimatedas:

    ;to,5=(Ln0,5)/Ln(1m)(3)

    ;Wheremistheannualmortalityrate.

    ;2.4Statisticalanalysis

    ;Wecalculatedcorrelationsamongnumberof ;individualsintheinitialyear(Ni),numberofdead ;individualsintheinitialsampleduringthemonitoring ;period(Mf)andthenumberofrecruitedindividuals ;fromtheinitialsample,intheperiodfortheclassof10 ;cmd(Rf).Analysesofmortalityandrecruitmentrates ;wereperformedusingthenonparametric

    ;Kruskal—Wallis’testandcorrelationanalysisusingR

    ;language.

    ;Toanalyzetheeffectoftemporalvariationson ;forestdynamics,wecalculatedmortalityand ;recruitmentratesforthreeperiods:P1=19901995,

    ;P2=1995--2000andP3=2000??2006inloggedforest; ;P1=19911996,P2=19962001andP3=20012006in

    ;unloggedforest.

;3.Results

    ;3.1Totalandplottreedensityandspecies

    ;number

    ;Totalnumberoftrees,withd>l0cm,attheinitial ;andfinalyearsofmonitoringintheunloggedforest

    .respectively’ ;were307treesha.and274treesha

    ;Accordingly55and48specieswerefound.Among ;thempredominateAttaleabutyracea,Coccoloba ;padiformis,Spondiasrnombin,Fissicalyxfendleri, ;Zanthoxylumculantrillo,Pouteriareticulata,Pachira ;quinata,SyagrussanconaandTerminaliaamazonia ;withmorethan10treesha.Mostofthesespecies

    ;belongtothelargesize(hmax>30m)intermediate ;tolerantspecies(Table11.

    ;Table1Initialandfinaltreedensity(treesha’)for

    ;functionalgroupsattheexperimentalunit

    ;oftheCaparoForestReserve,Venezuela

    ;Intheloggedforestwe

    ;207treeshaattheinitial

    ;found155treeshaand

    ;andfinalyearsofthe

    ;monitoringperiod,respectively.Similarly,59and60 ;specieswerefoundintheseyears;amongthem ;predominateAttaleabutyracea,Ochromapyramidale, ;CecropiapeltataandPouteriareticulatawithmore ;than10treesha-.Themajorityofthesespeciesbelong ;tothemediumsizepioneerspecies,reflectingforest ;recoveryafterselectivelogging.

    ;Ingeneral,treedensityintheunloggedforest ;decreased10.75%,whereasincrementswereonly ;observedforthelargetolerantspeciesgroup(1.63%), ;palms(1.3%),largeintermediatetolerant(0.98%)and ;smallpioneers(0.16%).Onthecontrary,forthelogged ;forestwefoundanoverallincrement0f33.66%withthe ;highestvariationforthe1argeintermediatetolerant ;59

    ;Dynamicsoftreespeciesecologicalgroupsinloggedandunloggedtropicalforestsintheve

    nezuelanwesternplains

    ;speciesgroup(8.25%)andmediumintermediatetolerant ;(6.47%)andmediumpioneers(6.80%)(Fig.1). ;togged盛嚣

    ;?

    ;4.

    ;2.

;.

    ;IamMP?下

    ;mdlan翻伊-.

    ;Fig.1Observedinitialandfinaltreedensityforecological ;groupsinloggedandunloggedstands

    ;attheexperimentalunitoftheCaparo

    ;ForestReserve,Venezuela

    ;Notes:IG,Largeintermediatetolerantspecies(h>30rn): ;IM,Mediumintermediatetolerantspecies(b=153Om);IP,

    ;Smalltolerantspecies(h>l5m);PM,Mediumpioneers;PP, ;Smallpioneers;TG,Largetolerantspecies;TM,Medium ;tolerantspecies;TP.Smal1tolerantspecies. ;Highlysignificantdifferenceswerefoundfortree ;densitybetweenloggedandunloggedstandsfF= ;14.507,P=0.0008l)andamongplots(F=12.063, ;P=9.636eO6):whereassignificantdifferences ;werefoundbetweenyears(F=3.0478,P=O.02772). ;3.2Mortalityandrecruitment

    ;3.2.1Unloggedforest

    ;Treemortalityofinitialindividualsduringthe ;monitoringperiodwas31.92%(27.51deadtreesha ;yr1withanannua1rateof2.61%.Thehalf-lifeoftree ;communitieswouldbeonly26.21yr.Similarly.tree ;recruitmentratewasI.33%(Table21.

    ;Mostofthemortality(52%)duringthisperiodis ;concentratedinsevenspecies:Coccolobapadiformis ;(9.28%),Trichiliamaynasiana(8.25%),Attalea ;butyracea(8-25%),Trlariscaracasana(8.25%), ;1rigaoerstediana(7.22%),Zanthoxylumculantrillo ;(5.15%)andCecropiapeltata(5.15%).Thehighest ;proportion(53.61%1iscontributedbylargetolerant ;species(20.62%)followedbymediumpioneers ;species(16.49%),andmediumintermediatetolerant ;species(16.49%1.

    ;Table2Treemortalityandrecruitmentatthe ;ExperimentalUnitoftheCaparoForestReserve, ;Venezuela

    ;Similarly,mostoftherecruitment(5O.8%)is ;contributedbyAttaleabutyracea(10.77%),Syagrus ;sancona(1o.77%),Coccolobapadiformis(9.223%), ;Zanthoxylumculantrillo(7.69%),Brosimum ;alicastrum(6.15%)andProtiumcrenatum(6.15%). ;Regardingthefunctionalgroups,thehighest ;proportion(56.92%)iscontributedbypalms(21.54%),

    ;followedbylargetolerantspecies(18.46%)and ;reediumintermediatetolerantspeciesf16.92%). ;Neithermortality(H=3.4286,2d.f.,P=0.1801) ;norrecruitmentannualrates(H=3.7143,2d.f., ;P=0.1561)weresignificantlydifferentbetweenyears. ;Likewise,forthefunctionalgroups(Figure2)neither ;mortality(H=12.0625,8d.f,P=0.1484)nor ;recruitmentrates(H=9.0467,8d.f.,P=0.3384)were ;significantlydifferent.

    ;Thecorrelationanalysisshowedthatthenumber ;oftreesrecordedin1991(unloggedforest)isnot ;correlatedwiththenumberofdeadindividualsinthe ;monitoringperiod(r=0.2034,P=0.3152).Neitherwas ;significantthecorrelationbetweenrecruitedtreesin ;eachoneoftheplots(r=0.35,P=0.2472).Correlation ;鬻一一

    ;

    ;ii

    ;.

    ;D

    ;.....

    ;y

    ;betweentreemortalityandrecruitmentwasnot ;significantfr=0.2357;P=0.2997)either. ;LIMISlPALMMPSPLTMTST

    ;UM1sIPALMMPSPLTMTST

    ;Fig.2Treemortalityandrecruitmentratesforecological ;groupsinunloggedstandsatthe

    ;ExperimentalUnitoftheCaparo

    ;ForestReserve,Venezuela

    ;Likewise,thecorrelationanalysisshowedthatthe ;numberofindividualspresentintheplotsin1990was ;notcorrelatedwiththenumberofdeadindividualsin ;theperiod(r=0.1327;P=0.3505),whereasasignificant ;correlationwasfoundforthenumberofrecruited ;individualsineachoneofthespeciesfr=0.9484; ;P=0.0173).Incontrast,thecorrelationbetweentree ;mortalityandrecruitmentwasnotsignificantfI__ ;0.3982;P=0.2262).

    ;3.2.2Loggedforest

    ;Mortalityduringthemonitoringperiodofthe ;initiallyrecordedtreeswas35.04%andtheannualrate ;was2.67%(Table2).Similarly,treerecruitmentwas ;50.22%andannualrate2.58%.Moreover.ninespecies

    ;contributeto50.00%Oftherecordedmortalitydudng ;themonitoringperiod.Theyare:Attaleabutyracea ;(10.00%),Ochromapyramidale(8.57%),Guazuma ;ulmifolia(7.14%),Pouteriareticulate(7.14%),Luehea ;seemannii(6.19%),Couroupitaguianensis(3.81%), ;Ingaoerstediana(3.81%)andBrosimumalicastrum ;(3.33%).Thefunctionalgroupswiththehighest ;mortalityrate(58.57ofthetota1)aremedium ;intermediatetolerantspecies(22.38%),largetolerant ;(19.5%)andmediumpioneers(16.7%).

    ;Thetreespecieswiththehighestrecruitment ;valuesareAttaleabutyracea(9.57%),Ochroma ;pyramidale(7.66%),Pouteriareticulate(6.94%), ;Cecropiapelmm(5.98%),Sapiumstylare(4.78%), ;Terminaliaamazonia(4.31%),1ngaoerstediana ;(3.83%),Banarasp.,(3.59%)andGuazumaulmifolia ;(3.59%)amountingto50.2%ofthetota1.This ;recruitmentisconcentratedintheecologicalgroupsof ;mediumintermediatetolerantspecies(20.81%), ;mediumpioneerspecies(18.42%)andlargetolerant ;species(17.94%).

    ;Treemortalityrateintheloggedforestwas ;slightlyhigherthanrecruitment(2.58%yr). ;Regardingfunctionalgroups(Fig.31significant ;differenceswerefoundfor’mortalityrates(H=I5.6405,

    ;8d.f.,P=0.0478),butnotforrecruitmentrates(H= ;12.3831,8d.f.,P=0.1249).

    ;

    ;MSIPALMMPSPLTMTST

    ;LIMISlPALMMPSPLTMTST

    ;Fig.3Treemortalityandrecruitmentratesforecological ;groupsinloggedstandsattheExperimental ;UnitoftheCaparoForestReserve,Venezuela ;Treemortalityratesvaryamongperiodsforthe ;loggedforest,increasinginthesecondperiodand ;startingtodecreaseforthefinalmonitoringperiod, ;morethan20yearsafterlogging.Inthe19952000

    ;periodtreerecruitmentwaslowerthanmortality.In ;contrast,intheunloggedforestwefoundthattree ;recruitmentrateislowerthanmortalityinallthe ;periods,withthehigherdifferencereportedforthelast ;period(Fig.4).Neithermortalityrates(H=1.1556,2 ;d.f.,P=0.5611)notrecruitmen?

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