1981中国陆地生态系统碳通量的年际变化英文图文.docx

1981中国陆地生态系统碳通量的年际变化英文图文.docx

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1981中国陆地生态系统碳通量的年际变化英文图文

1981_2000年中国陆地生态系统碳通量的年际变化_英文__图文

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植　物　学　报　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

ActaBotanicaSinica　2003,45（5）:

552-560http:

//www.chineseplantscience.

com

InterannualVariationinTerrestrialEcosystem

CarbonFluxesinChinafrom1981to1998

CAOMing-Kui1,2,TAOBo1,LIKe-Rang1,SHAOXue-Mei1,StephenDPRIENCE2

（1.InstituteofGeographicSciencesandNaturalResourcesResearch,TheChineseAcademyofSciences,Beijing100101,China;

2.DepartmentofGeography,MarylandUniversity,CollegePark,Maryland,20742,USA）

Abstract:

　AdynamicbiogeochemicalmodelwasusedtoestimatetheresponsesofChina’sterrestrialnetpri2maryproductivity（NPP）,soilheterotrophicrespiration（HR）andnetecosystemproductivity（NEP）tochangesinclimateandatmosphericCO2from1981to1998.ResultsshowthatChina’stotalNPPvariedbe2tween2.89and3.37GtC/aandhadanincreasingtrendby0.32%peryear,HRvariedbetween2.89and3.21GtC/aandgrewby0.40%peryear,AnnualNEPvariedbetween-0.32and0.25GtCbuthadnostatisticallysignificantinterannualtrend.ThepositivemeanNEPindicatesthatChina’sterrestrialecosystemsweretakingupcarbonwithatotalcarbonsequestrationof1.22GtCduringtheanalysisperiod.TheterrestrialNEPinChinarelatedtoclimateandatmosphericCO2increasesaccountedforabout10%oftheworld’stotalandwassimilartotheleveloftheUnitedStatesinthesameperiod.ThemeanannualNEPfortheanalysispe2riodwasneartozeroformostoftheregionsinChina,butsignificantlypositiveNEPoccurredinNortheastChinaPlain,thesoutheasternXizang（Tibet）andHuang-Huai-HaiPlain,andnegativeNEPoccurredintheDaHingganMountains,XiaoHingganMountains,LoessPlateauandYunnan-GuizhouPlateau.China’scli2mateatthetimewaswarmanddryrelativetootherperiods,sotheestimatedNlowerthantheaveragelevel.China’sterrestrialNEPmayincreaseifistocontinuetode2creaseifthepresentwarminganddryingtrendsustains.Keywords:

　China;netprimaryproductivity（HR）;netecosystem

productivity（NEP;　　Actingasaosphericcarbon,terrestrialseasonalandinter2annualvariationsandthelong-termchangingtrendinatmosphericCO2concentration.SincetheIndustrialRevolution,terrestrialecosystemshaveabsorbedabout20%ofCO2releasedfromfossilfuelburningandland-usechanges,andtheuptakehaveincreasedsubstantiallyinthepastdecades（Bolinetal,2000;Prenticeetal,2001）.Despiteextensiveandintensivestudiesinthelastdecades,themagnitude,spatio-temporalvariation,andunderlyingmechanismsoftheterrestrialcarbonsinkre2mainuncertainbecauseofthehighheterogeneity,tempo2ralvariability,andmechanisticcomplexityintheprocess2esandfactorscontrollingecosystemcarboncycle.TheseuncertaintiesarelimitingourabilitytopredictthefutureatmosphericCO2concentrationandclimatechange,andaffectpolicy-makingformitigatethegreenhouseeffect.Asacountrywiththethirdlargestlandarea,Chinahasdi2verseclimateandecologicalzonesthatincludealmostalltypesintheworld,andsomeofwhichareunique.There2fore,quantificationoftheresponsesofChina’sterrestrialecosystemcarbonfluxestoclimatechangeisofgreatsig2nificancetoestimatingtheglobalterrestrialcarbonsink.Inthelastdecade,greatprogresshasbeenmadeinthestudyofChina’sterrestrialecosystemproductivityandcarbonstorage（ZhouandZhang,1996;Fangetal,1996;2001）.Ithasbeenestimatedthatthecarbonstor2ageinChina’svegetationisabout6GtC,soilcarbonstorageis92-186GtC,totalnetprimanyproductivity（NPP）is2-3GtC（ZhouandZhang,1996;Fangetal,1996;2001）,annualcarbonuptakebyforestis0.02-0.05GtC,andagriculturalsoilmaytakeup0.14GtC/a.However,fewstudieshavebeenconductedtoquantifytheinterannualvariationsandchangingtrendinChina’sterrestrialecosystemcarbonfluxes.Process-basedecosystemmodelsdescribemechanisticprocessesofecosystemcarboncycleandtheirdynamicresponsestochangesinenvironmentalconditions,andhavebeenwidelyusedinidentifyingandquantifyingtheterrestrialcarbonsink（Melilloetal,1993;CaoandWoodward,1998a;Crameretal,2001）.Modernecosystemmodelsaredevelopedbasedonextensivelytestedeco-physiologi2calmechanisms,andhavebeenusedextensivelyinglobalchangestudies.Asthesemodelsaredrivenwithactualchangesinenvironmentalconditionsandecosystempattern（suchasvegetationdistributionandcomposition）,theycanrealisticallycapturethespatio-temporalpatterninter2restrialcarbonfluxes.Moreimportantly,ecosystemmod2elingisanessentialtooltoprojectthefuturechangesinecosystemcarbonfluxes.Inthisstudy,weestimatedthedynamicresponsesofChina’sterrestrialecosystemcarbonfluxestochangesinclimateandatmosphericCO2during

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Received:

2002204225　Accepted:

2003201208

SupportedbytheMajorScientificProgramofKnowledgeInnovationProjectoftheInstituteofGeographicSciencesandNaturalResourcesResearch,TheChineseAcademyofSciences（CXIOG-E01-02-04）;theUSNationalAeronauticsandSpaceAdministration（NASA）UndertheContractNAG5932.

CAOMing-Kuietal:

InterannualVariationinTerrestrialEcosystemCarbonFluxesinChinafrom1981to1998　553

theperiod1981-1998usingtheCarbonExchangeintheVegetation-Soil-AtmosphereSystem（CEVSA）model（CaoandWoodward,1998a;1998b）.Withthesimula2tionresults,weanalyzedthespatialdistribution,interan2nualvariations,andchangingtrendofChina’sterrestrialcarbonfluxesandtheircorrelationswithclimatevariability.

Ab=min{Wc,Wj,Wp}（1-0.5Po/τPc）-Rd

（1）whereWcrepresentstheefficiencyofphotosyntheticen2

1　Methodology

1.1　CEVSAmodel

Terrestrialecosystemcarboncycleoccursthroughtheprocessesofphotosynthesis,autotrophicrespiration,litterproduction,andheterotrophicrespiration（HR）thatarecontrolledbytheeco-physiologicalcharacteristicsofbiomes（e.g.photosyntheticpathway,leafformandphe2nology）andbyenvironmentalconditions（e.g.radiation,temperature,waterandnutrient）.Tocouplethesebiolog2icalandenvironmentalcontrolsoverecosystemcarbonfluxes,CEVSA（CaoandWoodward,1998a;1998b）in2cludesthreemodules（Fig.1）:

thebiophysicalmodulecalculatesthetransferofradiation,water,andheattode2terminecanopyconductance,evapotranspirationandsoilmoisture;theplantgrowthmoduledescribesphotosynthe2sis,autotrophicrespiration,carbonallocationamongplantorgans,leafareaindex（LAI）andlitter;biogeochemicalmodulesimulatesthedecompositionoforganicoutputsinsoils.ofthemodelaregiveninCaoandW（）andWoodwardetal（1995）.Thekeyprocessesinthemodelarede2scribedinthefollowingsections.

Fig.1.　AschematicrepresentationofCarbonExchangeintheVegetation-Soil-AtmosphereSystem（CEVSA）thatwasusedinthisstudytoestimateinterannualvariationsinterrestrialecosystemcar2bonfluxesandstocks.

GPP,grossprimaryproductivity;LAI,leafareaindex;NEP,netecosystemproductivity;NPP,netprimaryproductivity.

1.1.1　PlantphotosynthesisandNPP　Plantphoto2synthesisdependsontheCO2utilizationefficiencyofpho2tosyntheticbiochemicalprocessesandCO2supplybydif2fusionthroughstomataintoleafintercellularspaces.TherateofplantCO2assimilationimpliedbybiochemicalpro2cesses（Ab）is（Collzetal,1991）

zymesystem,specificallythecarboxylatingenzymeRubis2co,andisrelatedwithfoliarnitrogencontent.Wjisthelimitationofelectrontransporttophotosynthesisasafunc2tionofincidentphotosyntheticallyactiveradiation（PAR）.Wpisthelimitationoftriosephosphateutiliza2tiontophotosynthesis,representingthecapacityoftheleaftoutilizeorexporttheproductofphotosynthesis.PoandPcaretheinternalpartialpressureofO2andCO2re2spectively.τisafactordependingupontemperature.Rdistherateofrespirationinlightduetoprocessesotherthanphotorespiration.

StomatalconductancecontrolsthediffusionofCO2

fromtheatmosphereintotheintercellularairspacesandthusCO2supplysforphotosynthesis.TherateofplantCO2assimilationimpliedbythestomatalconductancetoCO2（Ad）is（Harleyetal,1992）

（2）　　　Ad=gs（Pa-Pc）/160

（3）　　gs=（go（T）+g1（T）ARh/Pa）kg（ws）

wheregsisstomatal,andPaisthepartial2.thestomatalconduc22iszeroatthelightcom2,glisanempiricalsensitivitycoeffi2theactualrateofplantCO2assimilation.Rhisrelativehumidityoftheairsurroundingtheleaf.Tisabsolutetemperature.kg（ws）describestheresponseofstomatalconductancetosoilwatercontent（ws）.