简介：Background:Inthecontextofecosystemmanagement,thepresentstudyaimstocomparethenaturalandthepresent-dayforestedlandscapesofalargeterritoryinQuebec(Canada).Usingcontemporaryandlong-termfirecycles,eachnaturalforestlandscapeisdefinedaccordingtothevariabilityofitsstructureandcomposition,andcomparedtothepresent-daylandscape.Thisanalysiswasconductedtoaddressthequestionofwhetherhumanactivitieshavemovedtheseecosystemsoutsidetherangeofnaturallandscapevariability.Methods:Thestudyencompassedaforestedareaof17.5000km^2dividedinto14landscapes.Usingaframeworkthatintegratesfirecycles,agestructureandforestdynamics,wecharacterizedtheforestcompositionandagestructuresthatresultedfromthreehistoricalfirecycles(110,140,and180years)representativeoftheborealforestof.easternCanada.Themodelednaturallandscapeswerecomparedwithpresent-daylandscapesinregardtotheproportionofold-growthforests(landscapelevel)andtheproportionoflate-successionalforeststands(landscapelevelandpotentialvegetationtype).Results:Fourlandscapes(39%)remainwithintheirnaturalrangeofvariability.Incontrast,ninelandscapes(54%)showalargegapbetweennaturalandpresent-daylandscapes.Theseninearelocatedinthesouthernportionofthestudyarea,andaremainlyassociatedwithAbies-BetulavegetationwherehumanactivitieshavecontributedtoastrongincreaseintheproportionofPopulustremuloidesstands(early-successionalstages)andadecreaseofoldgrowthforeststands(morethan100yearsold).Asinglelandscape(7%),substantiallychangedfromitspotentialnaturalstate,isacandidateforadaptive-basedmanagement.Conclusion:Comparisonofcorrespondingnatural(referenceconditions)andpresent-daylandscapesshowedthattenlandscapesreflectinganimportantshiftinforestcompositionandagestructurecouldbeconsideredbeyondtherangeoftheirnaturalvariability.Thedescriptionofalandscape'snaturalvariabili

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