resultsseasonalwinds

ScienceinChinaSeriesE:TechnologicalSciences2009SCIENCEINCHINAPRESSSciChinaSerE-TechSci|Jul.
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7|1947-1957www.
scichina.
comtech.
scichina.
comDevelopmentofecohydrologicalassessmenttoolanditsapplicationLIUChangMing1,2,3,YANGShengTian2,WENZhiQun2,WANGXueLei2,WANGYuJuan2,LIQian2&SHENGHaoRan21InstitudeofWaterScience,BeijingNormalUniversity,Beijing100875,China;2StateKeyLaboratoryofRemoteSensingScience,BeijingKeyLaboratoryforRemoteSensingofEnvironmentandDigitalCities,SchoolofGeography,BeijingNormalUniversity,Beijing100875,China;3KeyLaboratoryofWaterResourcesandRelatedLandSurfaceProcesses,InstituteofGeographicalSciencesandNaturalRe-sources,ChineseAcademyofSciences,Beijing100101,ChinaThedevelopmentofHydro-InformaticModellingSystem(HIMS)providesanintegratedplatformforhydrologicalsimulation.
ToextendtheapplicationofHIMS,anecohydrologicalmodelingsystemnamedecohydrologicalassessmenttool(EcoHAT)hasbeendeveloped.
Integratingparameter-man-agementtools,RS(remotesensing)inversiontools,module-designtoolsandGISanalysistools,theEcoHATprovidesanintegratedtooltosimulateecohydrologicalprocessesonregionalscale,whichdevelopsanewmethodonsustainableuseofwater.
EcoHAThasbeenappliedtoseveralcasestudies,suchas,theYellowRiverBasin,theaciddepositionareainGuizhouprovinceandtheripariancatch-mentofGuantingreservoirinBeijing.
ResultsprovethatEcoHATcanefficientlysimulateandanalysistheecohydrologicalprocessesonregionalscaleandprovidetechnicalsupporttointegratedwaterresourcesmanagementonbasinscale.
EcoHAT,ecohydrology,distributedmodel,remotesensing1IntroductionWateristhemostimportantelementinecosystems.
Withincreasinglevelofhumanactivities,thetraditionalmanagementofwaterresourcesisuncapableofresolv-ingtheproblemsoffreshwatershortage,waterqualitydeterioration,declineinbiodiversifyandotherecologi-calproblems.
Therelationshipbetweenhydrologicalcycleandecosystems,thephysicalandchemicalmech-anismsoftheinteractionsbetweenhydrologicalandecologicalprocesses,andecologicallybeneficialandsustainableuseofwaterresourcesaretheimportantis-suesthatneedtoberesolved[1].
Ecohydrologyisthehotspotofmanyinternationalresearchprojects,suchastheinternationalgeosphere-biosphereprogramaspectsofthebiosphere(IGBP-BAHC)[2],theUNESCOinterna-tionalhydrologicalprogram(UNESCOIHP)[3]andsoon.
Alltheseprojectsregardecohydrologyasanimpor-tantresearchtopic.
Ecohydrologyresearchprovidesanewopenfieldforsustainableuseofwaterresources.
Therearemanyfactorswhichinfluencetheprocessesofecohydrology,andallofthemhaveobvioustemporalandspatialvariability.
WiththedevelopmentofRS,GISandcomputertechnology,computersimulationbecomesanimportantmethodtostudytheprocessesofecohy-drology.
UsingtheRStechnologyforaccesstospatialinformationandtheGISplatformtoestablishofre-gionalscaledistributedecohydrologicalmodelbecomesthenewdirectionofhydrologicalandwaterresourcesReceivedJuly28,2008;acceptedFebruary13,2009doi:10.
1007/s11431-009-0199-9Correspondingauthor(email:yangshengtian@bnu.
edu.
cn)SupportedbytheNationalKeyTechnologyR&DPrograminthe11thFive-yearPlanofChina(GrantNo.
2006BAB06B07),theNationalNaturalScienceFoundationofChina(GrantNo.
40671123),theNationalBasicResearchProgramofChina("973"Project)(GrantNos.
2005CB422207,G19990436),andtheNationalHi-TechRe-searchandDevelopmentProgramofChina("863"Project)(GrantNo.
2006AA12Z145)1948LIUChangMingetal.
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7|1947-1957research.
SWAT(soilandwaterassessmenttool),de-velopedbyUnitedStatesDepartmentofAgriculture(USDA)AgriculturalResearchService(ARS),isariverbasin/watershedmodel.
TheSWATmodelwasdevel-opedtopredicttheimpactsoflandmanagementprac-ticesonwater,sedimentandagriculturalchemicalyieldsinlargecomplexwatershedswithvaryingsoils,landuseandmanagementconditionsoverlongperiodsoftime[4].
SWIM(soilandwaterintegratedmodel),developedbyPotsdamInstituteforClimateImpactResearch,isusedtosimulateandpredictthehydrologicalcycle,vegeta-tiongrowth,migrationofnutrientsandpollutants,sedi-mentmovementecohydrologicalprocessesunderglobalclimatechangeandland-usechange[5].
EcohydrologystudiesinChinamainlyfocusonwaterandvegetationinteractionsinsoil-vegetation-atmosphere-transferofdroughtareas,wetlands,forestecosystemsatlocalscale.
Ecohydrologicalsimulationsystemwithintegratedeco-logicalandhydrologicalprocessesatregionalscalehasn'tbeendocumentedtodate[6―8].
TheInstituteofGeographicSciencesandNaturalResourcesResearch,theChineseAcademyofSciencesdevelopedtheHIMSsystem,whichhasdistributedhy-drologicalprocessessimulationfunction[1].
However,theHIMSincludesneitherthenutrientscomponentinthehydrologicalcycle,northeinteractionsbetweenthehydrologicalcycleandecosystems,inparticular,inter-actionsbetweenthehydrologicalcycleandvegetation.
Withthetechnologydevelopment,remotesensinghasbecomeanimportantdatasourceforhydrologicalmodel,whichcanprovidenotonlymoreinformationatlarge-scalebutalsomanyelementsofthehydrologicalcyclewhicharedifficulttoaccessbyconventionalmethods[9].
Therefore,toextendtheHIMS,makingfulluseofre-motesensingdatasources,couplingwiththephysicalandchemicalmechanismsoftheprocessofecohy-drologicalmodel,simulatinginteractionbetweenhy-drologicalcycle,nutrientcycleandplantgrowthinthesoil-plant-atmospherecontinuum(SPAC),theauthorsofthisarticledevelopedaregionalscaledistributedsimu-lationsystem,EcoHAT.
2GeneralprinciplesofEcoHATBasedonthemechanismofecohydrologicalprocessesinSPAC,theEcoHATintegratedtheprocessesofhy-drologicalcycle,nutrientscycleandplantgrowthinecosystems.
TheecohydrologicalprocessesdescribedinEcoHATareshowninFigure1.
Alltheseprocessesarebasedonecohydrologymodelsathomeandabroadwhichhavephysicalandchemicalmechanisms.
Tocali-bratetheparametersofthemodelsuitedforthestudyarea'snaturalparameters,thedatabaseofthelocaliza-tionmodelparameterswasestablished.
Throughre-gionalgridparametersinput,EcoHATisapixel-baseddistributedmodel.
EcoHATismainlycomposedofhydrologicalcycle,nutrientscycleandplantgrowth.
Hydrologicalcycleisthecorecomponentandalwaysconnectstotheothertwoparts.
ThroughcouplingwithHIMS,hydrologicalcycleofEcoHATincludescanopyinterception,infiltra-tion,rootswateruptake,soilmoisture,evapotranspira-tion,surfaceflow,lateralflow,recharge,base-flow,slopeflow,channelroutingandsoon.
Nutrientscycleincludesatmosphericdeposition,weathering,mineral,soilnitrification,denitrification,ammoniavolatilization,micro-organismsdecomposition;plantgrowthincludesNPP(netprimaryproduction)simulationanditsalloca-Figure1TheecohydrologicalprocessesdescribedinEcoHATsystem(thedashedlinesrepresenttheinteractionsbetweenprocesses).
LIUChangMingetal.
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7|1947-19571949tion,litterandnutrientsuptake.
Soilmoisture,whichisanimportantpartforconnectingwaterandmaterialcy-clesintheSPAC,influencesevapotranspiration,nutri-entscycleandplantgrowth[10].
Soilmoistureissimu-latedthroughsoilwaterequilibriummodelandisusedasinputparameterofevapotranspiration,nutrientscycleandplantgrowth.
Atthesametime,vegetationimpactssoilmoistureandnutrientscyclethroughecohydrologi-calprocessessuchasevapotranspiration,nutrientsup-takeandlitter.
Thesub-modulesandmainequationsofEcoHATarelistedinTable1.
3ConstructionofEcoHAT3.
1FrameworkofEcoHATEcoHATsystemintegratesparametersmanagementtools,RSparametersinversiontools,modeldesigningtoolsandGISanalysistools,whichcanbeemployedasabasicscientifictoolforintegratedwaterresourcesmanagementonbasinlevel.
TheframeworkofEcoHATsystemisshowninFigure2.
Figure2TheframeworkofEcoHAT.
3.
1FounctiondevelpmentofEcoHATInordertoovercomethedifficultiesinparametersmanagement,landsurfaceparametersaccess,ecohy-drologicalprocessessimulation,distributedmodelgrid-basedcomputing,andresultsanalysisandvisualization,EcoHATwasdesignedtoprovidethefollowingfunc-tions.
(i)Parametersmanagement.
Ecohydrologicalproc-essesinvolvemanyparametersandvariousdatatypes,suchastext,vectordataandgriddata,andEcoHATusesfilesystemtomanagethem.
EcoHATstoresalloftheinputparametersinonefolder.
Filenamesandfor-matsareinlinewiththenameandstructureofthemodel.
EcoHATreadsthecorrespondingparametersautomati-callyduringsimulations.
(ii)Landsurfaceparametersinversionbyremotesensingdata.
Remotesensingisanimportantsourceofdata,soEcoHATintegratedlandsurfaceparametersremotesensingretrievingalgorithm,includingavarietyofvegetationindex,surfacealbedo,landsurfacetem-perature,leafareaindex,soilmoisture,soiltemperature,solarradiation,andotherlandsurfaceparameters.
Theremotesensingretrievedparametersprovideaspatialdatasourceforecohydrologicalprocessessimulation.
(iii)Ecohydrologicalprocessessimulation.
EcoHATintegratedvariousecohydrologicalprocessmodels,in-cludinganumberofhydrologicalprocesses,aslistedinTable1andFigure2.
Modulargraphicuserinterfacewasdesignedtoenableuserstoselectdifferentmethodsandinputparametersforsimulation.
Usingafolderpathtospecifytheinputs,EcoHATreadsallmodelparame-tersrequiredforsimulation.
Inthecalculationprocess,thegriddatatiledcomputationtechnologysolvestheproblemsofslowgridcomputationandmemoryinade-quacyfordistributedmodelsimulation.
(iv)Ecologicalprocesssimulationonregionalscale.
Basedonecohydrologicalprocesssimulationandmodulargraphicuserinterface,ecohydrologicalprocessmodelsarecustomizedtoecologicalprocesssimulationatregionalscale.
(v)GISanalysistools.
EcoHATdevelopedaGISsystemanalysistoolwhichcandirectlyimportthere-sultsofthesimulationmodelforvisualization,statisticsandmapping,facilitatinganalysisofthesimulationre-sults.
3.
1TechniquedevelopmentofEcoHATEcoHATisdevelopedbyIDL(InteractiveDataLan-guage).
IDLisanidealprogramminglanguagetode-velopvisualizationanalysis,withtheadvantagesofrapiddevelopmentandhighspeedinmatrixcomputa-tion.
BasedtheIDLplatformintheWindowsoperatingsystemandusingobject-orientedprogrammingmethods,eachbasicfunctionandecohydrologicalprocessarein-tegrated.
TheideaofEcoHATtechnologydevelopmentisthesameasthatofHIMS,thatis,themodularinter-facedevelopmentandintegration,thegriddatatiledcomputationtechnologyandimagepyramidtechnology.
TheinterfaceofEcoHATisshowninFigure3.
1950LIUChangMingetal.
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7|1947-1957Table1MainequationsinEcoHATProcessIlluminationMainequationTheoryCanopyinterceptionSimulatecanopyinterceptionvAcvcdvccmin(,,)IdPIWIKdLAI==HIMS[1]InfiltrationSimulateincreaseofsoilmoistureinsoilafterprecipitation1111,0,(other)iiiiiiiPDPDD==>∑∑Redistributionofsoilmoisture[11]EvapotranspirationSimulateevapotranspirationoflandsurfacecoveredwithvegetationpc0aspETKETETKET==FAOrecommendmethodRootswateruptakeSimulatewaterabsorbedbyrootsofvegetationroot,sprroot1expzzSKTzβDeJongwaterabsorptionfunction[12],SWAT[4]SoilmoistureSimulatesoilmoisturedailychangesindifferentlayersbasedonwaterbalanceequationPrecipitation:1arootjjjjjSWSWDES+Noprecipitation:1arootjjjjSWSWES+=Soilmoistureequilibriummodel[13―15],SWAT[4]SurfaceflowWaterbalanceforsurfaceflow,wheresurfaceflowequalsthedifferencebetweenprecipitationandinfiltration1d1iiiQPD==∑HIMS[1]LateralflowLateralflowisassumedtobeinproportiontoinfiltration1lam1(/)iiiQLSWSWD==∑HIMS[1]RechargeEmpiricalequationtoestimaterechargetogroundwater1cm1(/)iiliRECRSWSWDQ=∑HIMS[1]Base-flowBase-flowcoefficientmethodbbs()QKGWREC=+HIMS[1]SlopeflowDynamicsmethodslxyVmSh=HIMS[1]ChannelroutingMuskingummodelout,21in,22in,13out,1QCQCQCQ=++HIMS[1]SoildenitrificationSimulatetransformationofnitratenitrogenintonitrogenapNsTpHDDffff=6omp41410536512DCα=Simplifieddenitrificationmodel[16―20]SoilnitrificationandammoniavolatilizationSimulatetheactualrateofnitrificationandtransformationofammoniumintoammonianit/vol4nitvolNNH(1exp())ηηSWAT[4,21]MineralSimulatetransformationoflitterintosoilbase-exchangeableionsdecffd(1e)dkLLtδ=FORNBM[22,23]Base-exchangeableionsexchangeSimulatesoilcolloidadsorptionofbase-exchangeableionsinthesoilsolutionandtheconcentrationofbase-exchangeableionsexchange{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}{}3222AlCaAl/CaCa/Na22233NaCa2++MgKMg/NaK/Na2+2+NaNa2+22+2HHH/CaH/Mg22++CaMg++HHH/KH/Na++KNaCaNaCaAlNaNa==MgKCaMg==HHKNa==HHEESSEEEESSEEEESSEEEESSEE++++==MAGIC[24]VegetationNPPSimulatenetprimaryproductivityofvegetation123a()()()GPPAPARfTffNUNPPGPPRεβ=****=Lightproductivitymodel,FORSVA[23,25]NPPallocationSimulateNPPallocatedtoleafs,branchesandrootsleafLAleafdddNPPRttε=wattleleafrddddddNPPNPPNPPKttt=FORNBM[26]NutritionabsoiptionSimulatesoilbase-exchangeableionsabsorbedbyplantsuptakeavaildemmin(,)XXX=FORSVA[23,25],FORNBM[26](i)Modularinterfacemodeldevelopment.
WithintheEcoHATframework,eachecohydrologicprocesscorre-spondstoamoduledefinedasaclassintheprogram-minglanguage.
Eachclasshasitsownmethodsandproperties,wheremethodsrepresentdifferentmodelingapproachesofacertainecohydrologicalprocessandLIUChangMingetal.
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7|1947-19571951propertiesdefinethevariablesineachapproachasinput,outputorparameters.
Throughthecreationofclasses,anymoduleofecohydrologicprocesscanbecalledtocustomizedifferentecohydrologicalprocesses.
(ii)Griddatatiledcomputationtechnologyandimagepyramidtechnology.
Fortheproblemofsimulatingandvisualizatingalargeareawithhighresolutionremotesensingdata,griddatatiledcomputationtechnologyandimagepyramidtechnologyweredeveloped[27].
Griddatatiledcomputationtechnologydividedthewholegriddataofcomputingmodelintosmallblocks,whichareusedasasmallinputintothemodel.
Aftercomputingasmallblock,itsavestheresultstothedisk,andthengoesontoprocessthenextblock.
Throughthegriddatatiledcomputationtechnology,theproblemofslowgridcomputationindistributedmodelissolved.
Rasterpyramidofalargeareawithhighresolutionremotesensingdataiscreatedbyimagepyramidtechnology.
WhensimulatedresultsarevisualizedinEcoHAT,thevisualizationdataaccessedfromtherasterpyramidisonlythedataaccordingtothescaleandscope,avoidingrepeatedtime-consumingre-samplingtoreducethememoryusageandimprovingprocessingspeedofsimulationinthelargeregionalgriddatawithhigh-resolutionremotesensingdata.
4ApplicationandverificationFundedbytheNationalKeyBasicResearchDevelop-mentProgramofChina,NationalKeyTechnologyR&DPrograminthe11thFive-yearPlanofChinaandothertasks,EcoHAThasbeenappliedtoandverifiedbysometypicalareas,includingtheYellowRiverbasin,theaciddepositionareainGuizhouprovinceandriparianzoneofGuantingreservoirinBeijing.
4.
1ApplicationtomonitorecologywateruseofvegetationinatypicalareaoftheYellowRiverbasinTheregulationsofSanmenxiareservoiroftheYellowRiveraffectthehydrologicalsituationoftheWeiheRiver,andarelikelytoendangertheecologicalbalancealreadyformedinSanmenxiaReservoirarea.
Therefore,itisveryimportanttomonitorecologicalwaterusebyvegetationintheSanmenxiareservoirarea.
TheSan-menxiareservoirareaislocatedintheregionof110°21′42″E―112°01′21″E,33°31′24″N―35°05′48″N,withanareaof3754km2.
Theareaislocatedinthemid-latitudeinlandarea,withawarmtemperatecontinentalmonsoonclimate.
Themeanannualrainfallis574mm,andtemporaldistributionofprecipitationisuneven.
Thewaterresourcesintheareaarescarce.
Usingtheinte-gratedrainfallinfiltration,root-wateruptake,soilmois-tureandevapotranspirationsub-modelsofEcoHAT,theecologicalwateruseofvegetationwassimulated.
Theinputparametersincludedlandsurfaceparametersandmeteorologicalparameters.
Themeteorologicalparame-tersincludedrainfall,airpressure,relativehumidity,temperature,windspeed,solarradiationandtemperature;thelandsurfaceparametersincludedvegetationindex,leafareaindex,surfaceemissivity,albedo,surfacetem-peratureandvegetationcoverage.
UsingtheremotesensinginversiontoolsofEcoHAT,landsurfacepa-rameterswereretrievedfromtheLandsatTM5.
Withcombinationofunsupervisedclassificationmethodandvisualinterpretationmethod,thelandcoverofthestudyareawasclassifiedintofivecategories,includingforest,grassland,shrubs,farmland(limitedtorain-fedagricul-ture)andbaresoil.
Theatmosphericpressure,windspeed,temperature,relativehumidityandothermete-orologicalparametersofthemeteorologicalsitewereinterpolatedintogridmapbyGISusingthespatialresolutionofLandsatTM5.
TheecologicalwateruseofvegetationinSanmenxiareservoirareawasobtainedandtheresultwasshowninFigure4.
InordertoverifytheaccuracyofEcoHAT,thelargeaperturescintillometerobservationofJingChuanMete-orologicalObservatorywasusedinthestudyarea.
Ac-cordingtotheenergybalance,dailyaverageofsensibleheatfluxwasusedtocomputethedailyevapotranspira-tion,whichisequivalenttotheecologicalwateruseofvegetation.
WithDMC-1remotesensingdataobtainedinthesameperiodoftheobservationpoint,EcoHATwasusedtosimulateecologicalwateruseofvegetation.
Therelationofobservationsandsimulationswasana-lyzed(Figure5),anditwasshownthattheobservationsandsimulationresultshadastrongcorrelation(R=0.
9)andtheaveragerelativeerrorwasonly9.
4percent.
TheanalysisverifiedtheeffectivenessofEcoHATinsimu-latingvegetationecologicalwaterconsumption.
4.
2ApplicationtoanalysisoftheeffectofaciddepositiononvegetationgrowthinGuizhouprovinceGuizhouisseriouslyaffectedbyaciddeposition.
Analysisoftheeffectsofaciddepositiononvegetationgrowthisofgreatsignificance.
Thestudyareaislocatedintheregion106°34′25″E―107°30′12″E,25°53′45″N―26°45′28″N,1952LIUChangMingetal.
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Figure4EcologywateruseofvegetationintheSanmenxiareservoirarea(units:mm).
Figure5Therelationofobservationsandsimulationsofvegetationecologicalwaterconsumption.
withanarea6850km2.
Themeanannualtemperatureis14.
7℃.
Theaverageannualrainfallis1159mm.
Theregion'smainsoiltypeisyellowloamsoil.
Theareaiscoveredwithbroad-leavedforestandconiferousforest.
Themainspeciesarepine,fir,pear,blacklocust,oaks,chestnut.
Aftertheaciddeposition,H+exchangebase-exchangeableionsareadsorbedbysoilcolloidal,lead-ingtotheleachingofN,P,Ca,Mg,K,andothernutri-ents.
Asaresult,thegrowthofvegetationishindered.
EcoHATcanbeusedtosimulatetheeffectsofacidrainonvegetationgrowthinGuizhouprovince.
EcoHAT'ssoilmoisture,atmosphericdeposition,weathering,mineralization,vegetationabsorbedandvegetationNPPmodelswereintegratedinthisapplica-tion.
ThemaininputparameterswerethepHvalueofprecipitation,theconcentrationsofN,P,Ca,MgandKLIUChangMingetal.
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7|1947-19571953ionsinsoilandrainfall,stresscoefficientsofN,P,Ca,MgandKfordifferentvegetations,vegetationtypemap,andleafareaindex.
RSinversiontoolsofEcoHATwereusedtoretrievevegetationtypemapandleafareaindexfromtheLandsatTM5image,andtherestofthepa-rameterswereobtainedthroughindoormeasurements.
Firstly,thehydrologicalcyclemoduleswereusedtosimulatesoilmoisture,whichwastheinputofnutrientscycleandplantgrowth;secondly,thenutrientscyclewasusedtosimulatesoilnutrientscontentunderaciddeposition;andthirdly,vegetationNPPunderthestressofthesoilmoistureandnutrientsinthesoilweresimu-lated.
ModelswereruntosimulatethevegetationNPPinthestudyareaonamonthlybasis,andvegetationNPPofawholeyearwasobtainedaftercumulatingallmonths(seeFigure6).
Comparingthesimulationresultswiththemeasureddata,theaveragerelativeerrorofdifferenttypesofvegetationswasonly8.
5percent.
Inordertosimulatethevegetationgrowthunderdif-ferentconditionsofaciddepositionandtotakeintoac-countthatthestudyareaofprecipitationpHvaluewas4.
8,thepHvalueofrainfallwasreducedby1(pH=3.
8).
TherelativechangesofvegetationNPPaccordingtodifferentaciddepositionconditionswereshowninFigure7.
Itcanbeseenthatacidrainhadasignificantimpactonvegetationgrowthinthestudyarea.
4.
3ApplicationtoanalysisoftheeffectofNremovalinripariancatchmentofGuantingreservoirinBei-jingGuantingreservoirwashistoricallyoneofthetwomostimportantwatersourcesforBeijing.
TheripariancatchmentisthelastbufferzonepreventingNPSP(non-pointsourcepollution)fromuplands.
Thereservoirislocatedin115°30′E―116°E,40°N―40°30′N,withanaverageareaof670km2.
Theclimateinthisregioniscontinental,withseasonalwindsandtheaverageannualprecipitationis406mm,mostofwhichoccursinJulyandAugust.
Theannualaveragetemperaturerangesfrom2to8℃.
Theriparianzoneisspecialontheloca-tion,whichisauniqueterrestrialaquaticecotonebe-tweenthedrylandandwaters,andthemechanismoftheecosystemandecologicalfunctionsaredifferenttothoseofterrestrialecosystemsoraquaticecosystems.
TheFigure6VegetationNPPinstudyarea.
1954LIUChangMingetal.
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7|1947-1957Figure7TherelativechangesofvegetationNPPaccordingtodifferentaciddepositionconditions.
majorfunctionofriparianbufferzoneisnutrientreten-tion,suchastheemissionofnitrogenousgasbysoilchemicalprocessandnutritionuptakebyvegetation.
Inboththetwoprocesses,soilwaterisanindispensableelement,foritisthereactantofsoilchemicalreactionandthemediaofnutrientsabsorptionbyplants.
ThesimulationofnitrogenremovalprocessinEco-HATincludessoilnitrification,denitrification,ammoniavolatilizationandplantgrowth.
Theinputdataincludemeteorologicaldata,soildataandremotesensingdata.
LandsatTM5imagedatawereusedtoinverselandsur-faceparameters,andSPOT5imagedatawereusedtointerprettheinformationoflandcover,soiltypeandvegetationtype.
Firstly,landsurfaceparameters,suchasleafareaindex,surfaceemissivity,vegetationcoveragerate,surfacenetradiationsoiltemperatureandothers,wereinversedfromLandsatTM5datausingRSinver-siontoolsofEcoHAT.
Secondly,hydrologicalcyclemodulewasusedtoestimateevapotranspirationandsoilmoisture.
Thirdly,thenutrientscyclemodule,includingsoildenitrification,nitrificationandammoniavolatiliza-tionprocesses,wasusedtoestimatetheloadofnitrogenremovalbysoilchemicalprocessesinriparian.
Finally,plantgrowthmodulewasusedtoestimatethenitrogenremovalloadbyplantuptake.
TheperiodofsimulationwasfromMarchtoSeptember,2007,withmonthlytimestep.
Thespatialdistributionofnitrogenremovalinri-pariancatchmentisshowninFigure8.
Figure8ThespatialdistributionofnitrogenremovalinripariancatchmentfromMarchtoSeptember(units:kg).
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7|1947-19571955Toverifythemodel'saccuracy,afieldexperimentintheriparianwascarriedoutsimultaneouslyinGuishuiheRiverbasin(YanqingSoilandWaterConservationSta-tion)ofGuantingReservoirarea[28].
Basedontheresultsoftheexperiment,themassbalancemethodwasusedtotestthesimulatedresults.
Theequationisasfollows:s0snpsrsl,TNTNTNTNTN1)whereTNsoistheoriginalTN(totalnitrogen)contentinthesoil(gN·m2);TNsnistheresidualTNcontentinthesoilafteronemonth(gN·m2);TNpistheNcontentbyplantuptake(gN·m2);TNsristhetotalgaseousNre-movalload(gN·m2)permonth;TNslistheTNcontentbyleachinginthesoillayer(gN·m2).
Theexperimentwascarriedoutatahalfclosedtrialsystem,whichcutofftheconnectiontothegroundwater,sotheNleachingwassupposedtobezero(TNsl=0).
Accordingtoeq.
(1),theamountofthenitrogenremovalbysoilchemicalprocessequaledthedifferencebetweentheamountsofTNdecrementinthissystemanduptakebyplants.
Figure9depictsthecorrelationanalysisofobservedandsimulatedvaluestothegaseousnitrogenemissionloads.
Thecorrelationcoefficientwasgreaterthan0.
7,hencethemodelcouldproducesoundresults.
Figure9CorrelationanalysisofsimulatedsoilNremovalloadbysoilchemicalprocessandtheloadscalculatedinthefieldexperiment.
5ConclusionanddiscussionTheapplicationsofEcoHATintypicalareas,includingtheYellowRiverbasin,theacidraindepositionareasinGuizhouprovinceandtheripariancatchmenttotheres-ervoirinBeijing,showthatEcoHATsystemcanbeusedtosimulateandestimateecohydrologicalprocessesonregionalscale.
EcoHATsystemhasthesoftwarecopy-right(2008SR06938)now.
Comparingwithotherhy-drologicmodelingsystemsathomeandabroad,Eco-HAThasthefollowingcharacteristics.
(i)EcoHATintegrateshydrologicalcycleprocesses,nutrientscycleprocessesandplantgrowthprocesses,andtakesaccountofnutrientscycleandvegetationgrowthintohydrologicalcycle,whichcancomprehen-sivelysimulatetheregionalecohydrologicalprocessesbasedonthephysicalandchemicalmechanisms.
(ii)EcoHATcoupleswithRSmodelstoinverselandsurfaceparameters,providingaspatialdatasourceforecohydrologicalprocessessimulation.
(iii)EcoHAT,coupledwithindependentlydevelopedGISanalysistools,cananalyzeandvisualizethesimu-latedresults.
Griddatatiledcomputationandimagepyramidtechnologiescansolvetheproblemoflowgridcomputationspeedandimprovetheefficiencyofdis-tributedmodel.
AlthoughEcoHATworksefficiently,itstillneedstobeimprovedvastlyincertainaspects,suchastheeco-hydrologicalprocessesbetweenpixelgridsandimpactsofhumanactivitiesontheeco-hydrologicalprocess.
WithfurtherdevelopmentandcouplingwithHIMS,theEcoHATcanservefortheintegratedwaterresourcesmanagementinthefuture.
NomenclatureIvA,canopyinterception(mm);dc,vegetationcoveragedegree,reflectingthespatialdistributionofvegetation;P,rainfall(mm);Iv,canopyinterceptioncapability(mm);Wcd,watershortageforthecanopy(mm);Kc,canopyinterceptioncoefficient,relatedtovegeta-tiontypes;LAI,thevegetation'sleafareaindex;D,increaseofsoilmoisturecausedbyirrigationorrainfall(mm);ETp,potentialevapotranspiration(mm);ET0,potentialevapotranspirationoflandsurfacecov-eredwithvegetation(mm);ETa,actualevaporation(mm);Ks,stresscoefficientofsoilmoisture;Sroot,z,rootswateruptakeatZdepth(mm);Tp,potentialtranspirationofvegetation(mm);βr,effectivewaterdistributioncoefficient;1956LIUChangMingetal.
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7|1947-1957Zroot,z,thedepthofroots(mm);SWj,soilmoistureofjlayer(mm);Ea,actualevaporationbetweenthetreesonsoilsur-face(mm);La,coefficientofsub-surfacerunoff;SWm,maximumsoilstoragecapacity(mm);Rc,coefficientofrechargeintothegroundwater;Kb,coefficientofbaseflow;GWs,groundwaterstorage-volume(mm);Vs,averagewaterflowvelocityintheslopesection(m·s1);m,averageroughnessoftheslope;Sl,hydraulicgradientforthehillsideslope;hhydraulicradius(m);x,y,indexes;Qin,1,Qin,2,flowintoriveratthebeginningandendofatimestep(m3·s1);Qout,1,Qout,2,flowoutofriveratthebeginningandendofatimestep(m3·s1);C1,C2,C3,parameters;Da,theactualrateofdenitrification(gN·m2·d1);Dp,thepotentialrateofdenitrification(gN·m2·d1);fN,non-dimensionalsoilnitrateattenuationfunction;fsnon-dimensionalattenuationfunctionofsoilmois-ture;fT,non-dimensionalattenuationfunctionofsoiltem-perature;fPH,non-dimensionalattenuationfunctionofsoilpH;αom,decayratesofsoilorganicmatter;C,contentofcarboninthesoil(gC·g1);Nnit/vol,totalamountofNnitrificationandammoniavolatileinthesoil(gN·m2);NH4,totalamountofammoniuminthesoil(mol·m2);ηnit,factoroftheammoniumnitrification;ηvol,factoroftheammoniumvolatile;Ldec,decompositionrate(mol·m2);Lff,amountoflitter(gC·m2);Kδ,factoroftemperatureandhumidity;{Ca2+},{Na+},{K+},{Mg2+},{H+},{Al3+},activityofionsinsoilwater(mol·m2);ECa,EMg,ENa,EK,EH,EAl,percentagesofsoilbase-exchangeableionsinsoil;Al/CaCa/NaMg/NaK/NaH/CaH/MgH/KSSSSSSSSH/Na,exchangefactors;GPP,totalprimaryproductivity(gC·m2);Ra,plantrespiration(gC·m2);ε,solarenergyconversionrate(gC·MJ1);APAR,absorbedphotosyntheticalactiveradiation(MJ·m2);f1(T),functionoftemperatureimpactsonphotosyn-thesis;f2(β),functionofsoilmoistureimpactsonphotosyn-thesis,canbecalculatedbyKs,stresscoefficientofsoilmoisture;f3(NU),functionofnutritionimpactsonphotosynthe-sis;NPP,netprimaryproductivity(gC·m2);NPPLeaf,NPPofleafs(gC·m2);Rleaf,biomasstheofleatinunitarea(1m2)(g);εLA,leafareaincreasedmonthly(m2);NPPwattle,NPPallocatedtobranches(g);Kr,coefficientofallocation;Xuptake,soilbase-ex-changeableionsabsorbedbyplants(gC·m2);Xavail,soilbase-exchangeableionsthatplantscanmakeuseof(gC·m2);Xdem,plants'demandsofsoilbase-exchangeableions(gC·m2).
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