Background:Theimportanceofstructurallyperseforestsfortheconservationofbiopersityandprovisionofawiderangeofecosystemserviceshasbeenwidelyrecognised.However,toolstoquantifystructuralpersityofforestsinanobjectiveandquantitativewayacrossmanyforesttypesandsitesarestillneeded,forexampletosupportbiopersitymonitoring.Theexistingapproachestoquantifyforeststructuralpersityarebasedonsmallgeographicalregionsorsingleforesttypes,typicallyusingonlysmalldatasets.Results:HerewedevelopedanindexofstructuralpersitybasedonNationalForestInventory(NFI)dataofBadenWurttemberg,Germany,astatewith1.3millionhaofperseforesttypesindifferentownerships.Basedonaliteraturereview,11aspectsofstructuralpersitywereidentifiedaprioriascruciallyimportanttodescribestructuralpersity.Aninitialcomprehensivelistof52variablesderivedfromNationalForestInventory(NFI)datarelatedtostructuralpersitywasreducedbyapplyingfiveselectioncriteriatoarriveatonevariableforeachaspectofstructuralpersity.Thesevariablescomprise1)quadraticmeandiameteratbreastheight(DBH),2)standarddeviationofDBH,3)standarddeviationofstandheight,4)numberofdecayclasses,5)bark-persityindex,6)treeswithDBH>40cm,7)persityoffloweringandfructification,8)averagemeandiameterofdowneddeadwood,9)meanDBHofstandingdeadwood,10)treespeciesrichnessand11)treespeciesrichnessintheregenerationlayer.Thesevariableswerecombinedintoasimple,additiveindextoquantifythelevelofstructuralpersity,whichassumesvaluesbetween0and1.Weappliedthisindexinanexemplarywaytobroadforestcategoriesandownershipstoassessitsfeasibilitytoanalysestructuralpersityinlarge-scaleforestinventories.Conclusions:Theforeststructureindexpresentedherecanbederivedinasimilarwayfromstandardinventoryvariablesformostotherlarge-scaleforestin
