学科分类
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2 个结果
  • 简介:Forestgrowthismainlycurrentlymonitoredusingin-situmeasurementsinnortheastofChina.Toeffectivelymonitorforestgrowthdisturbanceatlargescale,weattemptedtouseremotesensingtechnique,particularly,timeseriesMODISdatafrom2004to2006.Theannualtimeseriesof8-dayenhancedvegetationindex(EVI)datasetwasgeneratedandsmoothedusingaSavitzky-Golayfilter.TheEVItrajectoryduringgrowthseasonwassimulatedusingalogisticmodel.Fromthesimulatedtrajectory,theEVIareaofgrowthseasonandannualEVIentropywerecalculated.Thesetwofactorswerecombinedtomapthedisturbanceregionsofforestgrowth.Finally,thedisturbanceregionswereverifiedusingasetofrandomsamples.Theresultindicatesthatthedisturbancepointshavedistinctivelyhigherentropyandlowerpeak.SomeofthesepointsalsoshowabruptEVIdeclineduringthemidseasonofthepeakphasesordoublepeaks.Thisapproachisdemonstratedtobefeasiblefordisturbancemonitoringofforestgrowth.

  • 标签: time series MODIS EVI growth SEASON
  • 简介:Theannualseriesofδ13CweremeasuredintreeringsofthreeCryptomeriafortuneidisks(CF-1,CF-2,andCF-3)collectedfromWestTianmuMountain,ZhejiangProvince,China,accordingtocross-datingtreeringages.Therewasnoobviousdecreasingtrendoftheδ13CannualtimeseriesofCF-2before1835.However,from1835to1982thethreetreeringδ13Cannualseriesexhibitedsimilardecreasingtrendsthatweresignificantly(P≤0.001)correlated.Thedistributioncharacteristicsofascatterdiagrambetweenestimatedδ13CseriesofCF-2frommodelingandtheatmosphericCO2concentrationextractedfromtheLawDomeicecorefrom1840to1978wereanalyzedandacurvilinearregressionequationforreconstructingatmosphericCO2concentrationwasestablishedwithR2=0.98.Also,atestofindependentsamplesindicatedthatbetween1685and1839thereconstructedatmosphericCO2concentrationusingtheδ13CseriesofCF-2hadacloserelationshipwiththeLawDomeandSipleicecores,withastandarddeviationof1.98.ThegeneralincreasingtrendofthereconstructedatmosphericCO2concentrationcloselyreflectedthelong-termvariationofatmosphericCO2concentrationrecordedbothbeforeandaftertheIndustrialRevolution.Between1685and1840theevaluatedatmosphericCO2concentrationwasstable,butafter1840itexhibitedarapidincrease.Givenalongerδ13Cannualtimeseriesoftreerings,itwasfeasibletorebuildarepresentativetimeseriestodescribetheatmosphericCO2concentrationforanearlierperiodandforyearsthatwerenotintheicecorerecord.

  • 标签: 大气CO2浓度 温室效应 全球变暖 气候