简介：Background:Couplingbiomassmodelswithnutrientconcentrationscanprovidesoundestimationsofcarbonandnutrientcontents,enablingtheimprovementofcarbonandnutrientbalanceinforestecosystems.Althoughnutrientconcentrationsareoftenassumedtobeconstantforsomespeciesandspecifictreecomponents,atleastinmaturestands,theconcentrationsusuallyvarywithage,siteindexandevenwithtreedensity.Themainobjectiveofthisstudywastoevaluatethesourcesofvariationinnutrientconcentrationsinbiomasscompartmentsusuallyremovedduringharvestingoperations,coveringarangeofspeciesandmanagementconditions:semi-naturalforest,conventionalforestplantationsandshortrotationforestry(SRF).Fivespecies(Betulapubescens,Quercusrobur,Eucalyptusglobulus,EucalyptusnitensandPopulusspp.)and14genotypeswereconsidered.Atotalof430treesweresampledin61plotstoobtain6biomasscomponents:leaves,twigs,thinbranches,thickbranches,barkandwood.AbovegroundleaflessbiomassWaspooledtogetherforpoplar.TheconcentrationsofC,N,K,P,Ca,Mg,S,Fe,Mn,Cu,ZnandBweremeasuredandtheto:[albiomassofeachsampledtreeandplotweredetermined.Thedatawereanalysedusingboostedregressiontreesandconventionaltechniques.Results:Themainsourcesofvariationinnutrientconcentrationswerebiomasscomponent>>genotype(species)≈age>treediameter.TheconcentrationsofCa,MgandKweremoststronglyaffectedbygenotypeandage.TheconcentrationsofP,K,Ca,Mg,SandCuinthewoodcomponentdecreasedwithage,whereasCconcentrationsincreased,withatrendtoreach50%intheoldertrees.IntheSRF,interamericanpoplarandP.trichocarpogenotypeswerecomparativelymoreefficientintermsofCaandKnutrientassimilationindex(NAI)(+65-85%)thaneucalypts,,mainlybecauseleaflessbiomasscanberemoved.Intheconventionaleucalyptplantations(rotation15years),debarkingthewoodatlogging(savingsof225%ofCaand254%ofMgforE.globulus)ortheuseofselectedgenotype

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