简介：Thispaperstressesthenecessityofdefiningrangeofurbanforestandprovidesthebasisforreasonablydeterminingrangeofurbanforestandsomebasicprinciplestobefollowed.

简介：WeinvestigatedthecompositionofplantcommunitiestoquantifytheirrelationshipswithenvironmentalparametersintheChitralHindukushrangeofPakistan.WesampledtreevegetationusingthePointCenteredQuarter（PCQ）methodwhileunderstoryvegetationwassampledin1.5-mcircularquadrats.CedrusdeodaraisthenationalsymbolofPakistanandwasdominantinthesampledcommunities.Becauseenvironmentalvariablesdeterminevegetationtypes,weanalyzedandevaluatededaphicandtopographicfactors.DCA-Ordinationshowedthemajorgradientasanamalgamofelevation（p〈0.05）andslope（p〈0.01）asthetopographicfactorscorrelatedwithspeciesdistribution.SoilvariableswerethefactorsofenvironmentalsignificancealongDCAaxes.However,amongthesefactors,Mg2＋,K＋andN2＋contributednotmorethan0.054%0.20%and0.073%,respectively,tovariationalongthefirstordinationaxis.Weconcludethattheprincipalreasonforweakornocorrelationwithmanyedaphicvariableswastheanthropogenicdisturbanceofvegetation.Theunderstoryvegetationwascomposedofperennialherbsinmostcommunitiesandwasmostdenseunderthetreecanopy.Theunderstoryvegetationstronglyregulatestreeseedlinggrowthandregenerationpatterns.Werecommendfurtherstudyoftheunderstoryvegetationusingpermanentplotstoaiddevelopmentofforestregenerationstrategies.

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

简介：Background:Informationonforeststructure,growth,anddisturbancehistoryisessentialforeffectiveforestmanagementinadynamiclandscape.BecausemostofourresearchconcerningtheecologyandgrowthofThujaoccidentaliscomesfromsitesinnorthernportionsofitsrange,highlycontextualbioticandabioticfactorsthataffectthespeciesinmoresouthernlocalesmaynotbefullyaccountedfor.ThisresearchcharacterizedthestructuralattributesandgrowthdynamicsofThujaoccidentalisindisjunctforeststandssouthofitscontiguousrangemargin.Methods:TheThujaoccidentalisforestsexaminedinthisresearchwerelocatedinthecentralAppalachianMountains,USA,approximately440kmsouthofthecontiguousrangemarginofthespecies.ForeststructuralattributeswerecharacterizedintwoThujaoccidentalisforeststands,whicharerareintheregion.Tree-ringchronologieswereusedtoexaminetheinfluencesofdisturbanceandclimateonthegrowthofThujaoccidentalis.Results:Theforestscontainedatotalof13treespecieswithThujaoccidentaliscontributingsubstantiallytothebasalareaofthesites.Thujaoccidentalisstemswereabsentinthesmallestsizeclass,whilehardwoodspecieswereabundantinthesmallestclasses.Thujaoccidentalisstemsalsowereabsentfromthe<70yearsageclass.Bycontrast,Thujaoccidentalissnagswereabundantwithinstands.Growth-releaseeventsweredistributedacrossthedisturbancechronologyandgenerallyaffectedasmallnumberoftrees.TheThujaoccidentalistree-ringchronologypossessedaninterseriescorrelationof0.62andmeansensitivityof0.25.ThecorrelationbetweenmeantemperatureandThujaoccidentalisgrowthwasweakandvariable.Growthandmoisturevariablesweremorestronglycorrelated,andthisrelationshipwaspredominantlypositive.Conclusions:Structuralattributesindicatetheforestsareintheunderstoryreinitiationstageofforestdevelopment.SilviculturalmanipulationsmaybenecessarytopromoteThujaoccidentalisestablishment.Thesensi