Boreas2009pollenrecord朱诚教授有关大九湖泥炭孢粉研究论文

AdetailedpollenrecordofvegetationandclimatechangesinCentralChinaduringthepast16000yearsCHENGZHU,CHUNMEIMA,SHI-YONGYU,LINGYUTANG,WENQINGZHANGANDXUEFENGLUBOREASZhu,C.,Ma,C.,Yu,S.-Y.,Tang,L.,Zhang,W.&Lu,X.2009:AdetailedpollenrecordofvegetationandclimatechangesinCentralChinaduringthepast16000years.Boreas,10.1111/j.1502-3885.2009.00098.x.ISSN0300-9483.Detailedpollenanalyses,alongwithmagneticandloss-on-ignition(LOI)measurements,wereconductedona3mlongpeatsequencerecoveredfromtheDajiuhuBasin,theShennongjiaMountainsinCentralChina.TenAMS14CdatesprovideafirmagecontrolonthispollenrecordintermsofvegetationchangesgovernedessentiallybytheriseandfalloftheAsiansummermonsoonduringthepast16000years.Between16000and12700cal.yrBP,pollenassemblagesweredominatedbyconiferousandbroad-leavedtrees,indicatingamixedforestlandscapecorre-spondingtotheinitialestablishmentofthemonsoonalclimateaftertheLastGlaciation.Theprogressiveincreasesinpercentagesofevergreentreepollenafter12700cal.yrBPpointtoasteadyenhancementofthesummermon-soon,whichwasepisodicallyweakenedduringtheYoungerDryasstadial.From11000to6000cal.yrBP,valuesofconiferousanddeciduoustreepollendecreased,whileevergreenbroad-leavedtreepollenincreasedsub-stantially,implyingastrongerthannormalmonsoonalclimateconditioncorrespondingtotheHoloceneHyp-sithermalInterval.Agreatreductioninthevaluesofevergreentreepollenatabout4000cal.yrBPindicatesasuddenretreatofthesummermonsoonfromthisarea.ChengZhuandChunmeiMa,SchoolofGeographicandOceanographicSciences,NanjingUniversity,Nanjing210093,P.R.China;Shi-YongYu(correspondingauthor;e-mail:[e-mail])andXuefengLu,StateKeyLaboratoryofLoessandQuaternaryGeology,InstituteofEarthEnvironment,CAS,Xi’an710075,P.R.China;LingyuTang,NanjingInstituteofGeologyandPalaeontology,ChineseAcademyofSciences,Nanjing210008,P.R.China;WenqingZhang,InstituteofHydrogeologyandEngineeringGeologyTechniques,CGS,Baoding071051,P.R.China;received14thFebruary2008,accepted11thMay2008.ClimateconditionsinthevastareaofEastAsiaareregulatedessentiallybythemonsooncirculation,alarge-scaleatmosphericpressurecellgeneratedbythethermalcontrastbetweentheEurasianlandmassandthetropicaloceans(Zhang&Lin1992;Chao&Chen2001).Inwinter,dryandcoldnorthwesternwindsori-ginatingfromtheMongolianHighprevail;conversely,warmandwetair-massesfromthetropicalPacificdominatetheareainthesummermonths.Seasonalchangesinthislarge-scalewindpatternexertconsider-ableinfluenceonhydrologicalcyclingandthushumanlivelihoodinthearea.GiventhearchaeologicalfactthatthisareahasbeenextensivelycolonizedfromtheNeolithicAgeonward(Zhuetal.1997;Zhu2005),studyingpastclimatechangesmayprovideaframe-workwithinwhichtheriseandfallofhumanciviliza-tionduringtheHolocenecanbebetterunderstood.OurknowledgeofthehistoryoftheEastAsianmonsoonduringthepastglacial/interglacialcyclesismainlyfromloess-soilsequences(An2000)andcavespeleothem(Wangetal.2001).LittleisknownaboutpostglacialvariationsintheEastAsiansummermon-sooninshortertimescales.Specifically,wearenotsurewhetherthemillennial-scaleoscillatorypatternofsum-mermonsoonthatprevailedduringtheLastGlaciationcontinuedintotheHolocene.Moreover,regardingthetimingofpostglacialstrengtheningofthesummermonsoonontheEurasianlandmass,asynthesisofearlierpublishedrecordsrevealsatime-transgressiveordiachronouspattern,i.e.astrongerthannormalmon-soonalclimateoccurredearlierinNorthChinathaninSouthChina(Anetal.2000;Heetal.2004).Accordingtorecentlypublishedrecordswithhighresolutionsandfirmageconstraints(Wangetal.1999;Hongetal.2005;Yanchevaetal.2007),thishypothesisisnotconvincingiftheunderlyingforcingmechanismcomesfromthevariationinsummersolarinsolationtothelowlati-tudesthroughthechangingpositionoftheInnertropi-calconvergencezone(Fleitmannetal.2007).Reliablerecordsfromthisareaarethereforeimportantinvali-datingthishypothesis.Givenitsuniquegeographicallocation(Fig.1A),CentralChinaisakeyareaforourunderstandingthespatialvariabilityoftheAsiansummermonsoonsys-tem.Anabsolutely-datedcavespeleothemd18OrecordfromtheeasternShennongjiaMountains(Shaoetal.2006)givesonlyageneralpictureofchangesintheAsiansummermonsoonbetween10000and2000yearsago,andthehistoryofthesummermonsooninthisareabeyondthisperiodisunknown.Moreover,thespeleothemrecordneedstobetestedusingotherprox-ies.Ombrotrophicpeatlandsshowpromiseasanexcep-tionalarchiveofclimateandenvironmentalchangesinthisarea(Wang&Sun1989;Zhaoetal.2007).Here,wepresentanAMS14Cdated,high-resolutionpollenrecordfromapeatlandintheDajiuhuBasinonthewesternmarginoftheShennongjiaMountains,CentralChina,todocumentvegetationandclimatechangesinDOI10.1111/j.1502-3885.2009.00098.xr2009TheAuthors,Journalcompilationr2009TheBoreasCollegiumtheareaduringthepast16000years.Comparedtopreviousstudies(e.g.Liuetal.2001;Heetal.2003;Zhaoetal.2007),ourrecordmayprovidealongerperspectiveonthechangesintheEastAsiansummermonsoonsystemfollowingtheLastGlacialMaximum.StudyareaandsitedescriptionTheShennongjiaMountainsaresituatedonthetopo-graphicaltransitionfromtheTibetanPlateautothelowerYangtzefluvialanddeltaicplains.Controlledbythemonsoonalclim