简介：Background:Weexplorethefactorsaffectingtheoptimalplotdesign(sizeandtypeaswellasthesubsampletreeselectionstrategieswithinaplot)andtheirrelativeimportanceindefiningtheoptimalplotdesigninamultipurposeforestinventory.Thefactorsincludetimeusedtolayouttheplotandtomakethetreemeasurementswithintheplot,thebetween-plotvariationofeachofthevariablesofinterestinthearea,andthemeasurementandmodelerrorsforthedifferentvariables.Methods:WesimulatedifferentplottypesandsizesandsubsampletreeselectionstrategiesonmeasuredtestareasfromNorthLapland.Theplottypesusedarefixed-radius,concentricandrelascopeplots.Weselecttheoptimaltypeandsizefirstatplotlevelusingacost-plus-lossapproachandthenatclusterlevelbyminimizingtheweightedstandarderrorwithfixedbudget.Results:Asrelascopeplotsareveryefficientattheplotlevelforvolumeandbasalarea,andfixed-radiusplotsforstemsperha,theoptimalplottypestronglydependsontherelativeimportanceofthesevariables.Theconcentricplotseemstobeagoodcompromisebetweenthesetwoinmanycases.Thesubsampletreeselectionstrategywasmoreimportantinselectingoptimalplotthanmanyotherfactors.Inclusterlevel,themostimportantfactoristhetransfertimebetweenplots.Conclusions:Whiletheoptimalradiusofplotsandotherparametersweresensitivetothemeasurementtimesandothercostfactors,theconcentricplottypewasoptimalinalmostallstudiedcases.Subsampletreemeasurementstrategiesneedfurtherstudies,astheywereanimportantcostfactor.However,theirimportancetotheprecisionwasnotasclear.

简介：

简介：Background:Ecologistsareinterestedinassessingthespatialandtemporalvariationinecologicalsurveysrepeatedovertime.Thispapercomparesthe1985and2015surveysoftheBarroColoradoForestDynamicsplot(BCI),Panama,dividedinto1250(20m×20m)quadrats.Methods,spatialanalysis:TotalbetadiversitywasmeasuredasthetotalvarianceoftheHellinger-transformedcommunitydatathroughouttheBCIplot.Totalbetawaspartitionedintocontributionsofindividualsites(LCBDindices),whichweretestedforsignificanceandmapped.Results,spatialanalysis:LCBDindicesindicatedthesiteswithexceptionalcommunitycomposition.In1985,theyweremostlyfoundintheswamphabitat.Inthe2015survey,noneoftheswampquadratshadsignificantLCBDs.Whathappenedtothetreecommunityintheinterval?Methods,temporalanalysis:Thedissimilarityincommunitycompositionineachquadratwasmeasuredbetweentime1(1985)andtime2(2015).TemporalBetaIndices(TBI)werecomputedfromabundanceandpresence-absencedataandtestedforsignificance.TBIindicescanbedecomposedintoB=species(orabundances-per-species)lossesandC=species(orabundances-per-species)gains.B-Cplotswereproduced;theydisplayvisuallytherelativeimportanceofthelossandgaincomponents,throughtime,acrossthesites.Results,temporalanalysis:InBCI,quadratswithsignificantTBIindiceswerefoundintheswamparea,whichisshrinkinginimportanceduetochangestothelocalclimate.ApublishedhabitatclassificationdividedtheBCIforestplotintosixhabitatzones.GraphsoftheBandCcomponentswereproducedforeachhabitatgroup.Group4(theswamp)wasdominatedbyspecies(andabundances-per-species)gainswhereasthefiveotherhabitatgroupsweredominatedbylosses,somegroupsmorethanothers.Conclusions:WeidentifiedthespeciesthathadchangedthemostinabundancesintheswampbetweenT1andT2.Thisanalysissupportedthehypothesisthattheswampisdryingoutandisinvadedbyspeciesfr

简介：