简介：Background:Dependingontreeandsitecharacteristicscrownbiomassaccountsforasignificantportionofthetotalabovegroundbiomassinthetree.Crownbiomassestimationisusefulfordifferentpurposesincludingevaluatingtheeconomicfeasibilityofcrownutilizationforenergyproductionorforestproducts,fuelloadassessmentsandfiremanagementstrategies,andwildfiremodeling.However,crownbiomassisdifficulttopredictbecauseofthevariabilitywithinandamongspeciesandsites.Thustheallometricequationsusedforpredictingcrownbiomassshouldbebasedondatacollectedwithpreciseandunbiasedsamplingstrategies.Inthisstudy,weevaluatetheperformancedifferentsamplingstrategiestoestimatecrownbiomassandtoevaluatetheeffectofsamplesizeinestimatingcrownbiomass.Methods:Usingdatacollectedfrom20destructivelysampledtrees,weevaluated11differentsamplingstrategiesusingsixevaluationstatistics:bias,relativebias,rootmeansquareerror(RMSE),relativeRMSE,amountofbiomasssampled,andrelativebiomasssampled.Wealsoevaluatedtheperformanceoftheselectedsamplingstrategieswhendifferentnumbersofbranches(3,6,9,and12)areselectedfromeachtree.Treespecificloglinearmodelwithbranchdiameterandbranchlengthascovariateswasusedtoobtainindividualbranchbiomass.Results:Comparedtoallothermethodsstratifiedsamplingwithprobabilityproportionaltosizeestimationtechniqueproducedbetterresultswhenthreeorsixbranchespertreeweresampled.However,thesystematicsamplingwithratioestimationtechniquewasthebestwhenatleastninebranchespertreeweresampled.Underthestratifiedsamplingstrategy,selectingunequalnumberofbranchesperstratumproducedapproximatelysimilarresultstosimplerandomsampling,butitfurtherdecreasedRMSEwheninformationonbranchdiameterisusedinthedesignandestimationphases.Conclusions:UseofauxiliaryinformationindesignorestimationphasereducestheRMSEproducedbyasamplingstrategy.Howe

简介：Addressingclimatechangehasbecomeacommonissuearoundtheworldinthe21stcenturyandequallyanimportantmissioninChineseforestry.UnderstandingthedevelopmentofmonitoringandassessmentofforestbiomassandcarbonstorageinChinaisimportantforpromotingtheevaluationofforestcarbonsequestrationcapacityofChina.Theauthorconductsasystematicanalysisofdomesticpublicationsaddressing'monitoringandassessmentofforestbiomassandcarbonstorage'inordertounderstandthedevelopmenttrends,describesthebriefhistorythroughthreestages,andgivesthesituationofnewdevelopment.Towardstheendofthe20thcentury,alargenumberofpapersonbiomassandproductivityofthemajorforesttypesinChinahadbeenpublished,coveringtheexplorationandeffortsofmorethan20years,whileinvestigationsintoassessmentofforestcarbonstoragehadbarelybegun.Basedonthedataofthe7thand8thNationalForestInventories,forestbiomassandcarbonstorageoftheentirecountrywereassessedusingindividualtreebiomassmodelsandcarbonconversionfactorsofmajortreespecies,bothpreviouslypublishedandnewlydeveloped.Accompanyingtheimplementationofthe8thNationalForestInventory,aprogramofindividualtreebiomassmodelingformajortreespeciesinChinawascarriedoutsimultaneously.Bymeansofthematicresearchonclassificationofmodelingpopulations,aswellasproceduresforcollectingsamplesandmethodologyforbiomassmodeling,twotechnicalregulationsonsamplecollectionandmodelconstructionwerepublishedasministerialstandardsforapplication.Requestsforapprovalofindividualtreebiomassmodelsandcarbonaccountingparametersofmajortreespecieshavebeenissuedforapprovalasministerialstandards.Withtheimprovementofbiomassmodelsandcarbonaccountingparameters,thematicassessmentofforestbiomassandcarbonstoragewillbegraduallychangedintoageneralmonitoringofforestbiomassandcarbonstorage,inordertorealizetheirdynamicmoni