He2015QRDajiuhu

PeatlandevolutionandassociatedenvironmentalchangesincentralChinaoverthepast40,000yearsYuxinHea,b,⁎,ChengZhaob,c,⁎⁎,ZhuoZhengd,ZhonghuiLiub,NingWangb,e,JieLid,RachidCheddadifaDepartmentofEarthSciences,ZhejiangUniversity,Hangzhou310027,ChinabDepartmentofEarthSciences,TheUniversityofHongKong,HongKong,ChinacStateKeyLaboratoryofLakeScienceandEnvironment,NanjingInstituteofGeographyandLimnology,ChineseAcademyofSciences,Nanjing210008,ChinadDepartmentofEarthSciences,SunYat-senUniversity,Guangzhou510275,ChinaeGuangzhouInstituteofGeochemistry,ChineseAcademyofSciences,Guangzhou510640,ChinafInstitutdesSciencesdel'EvolutiondeMontpellier,CNRS-UM2,Montpellier34095,FranceabstractarticleinfoArticlehistory:Received14November2014Availableonline26June2015Keywords:CentralChinan-AlkanesHopanesDajiuhupeatlandMarineIsotopeStages1–3CentralChinahasexperiencedstrongersummermonsoonduringwarmperiodssuchasMarineIsotopeStages(MIS)1and3,andweakersummermonsoonduringcoolperiodssuchasMIS2.TheevolutionhistoryofDajiuhusubalpinepeatlandincentralChinacanhelpinvestigatehowtheexpansionandshrinkageofpeatlandwereas-sociatedwithmonsoonalstrengthoverthelastglacial–interglacialcycle.Hereweapplybulkorganiccarbonandmolecularbiomarkers(hopaneandn-alkane)toreconstructtheevolutionhistoryfortheDajiuhupeatlandoverthepast40,000yr.Theresultsindicatefluctuationsbetweenlacustrineandpeat-likedepositionduringMIS3,steadylacustrinedepositionduringMIS2,andpeatlandinitiationandexpansionduringMIS1intheDajiuhupeatland.Therefore,attheglacial–interglacialscale,warmersummerandcoolerwinterconditionsininterglacialperiodsarecrucialtotriggerpeatdeposition,whereasreducedevaporationinglacialperiodinsteadofdecreasedmonsoonal-drivenprecipitationwouldhaveplayedapredominantroleintheregionaleffectivemoisturebal-ance.However,withintheHolocene(MIS1),monsoonalprecipitationchangesappeartobethemaincontrolleronmillennial-scalevariationsofwater-tableleveloftheDajiuhupeatland.©2015UniversityofWashington.PublishedbyElsevierInc.Allrightsreserved.IntroductionTheAsiansummermonsoonisanimportantatmosphericcirculationsystemmaintainingthelivingenvironmentontheAsiancontinent.ClimaticchangesthroughoutthelateQuaternaryintheEastAsiaarecharacterizedbyalternationsoftheAsiansummermonsoonstrength(An,2000).High-qualityδ18OrecordsfromcavestalagmitessuggestthatcentralChinahasexperiencedstrongersummermonsoonduringwarmperiodssuchasMarineIsotopeStages(MIS)1and3,andweakersummermonsoonduringcoolperiodssuchasMIS2(Wangetal.,2001,2008).However,knowledgeofclimaticvariationsandtheirrelationwithecosystemevolutionincentralChinaoverthelastinterglacial–glacialcycle(MIS1–3)remainsincomplete,owingtolimitedhigh-qualitypaleoclimaticrecordsavailableotherthanspeleothemδ18Orecords(Wangetal.,2001,2008;Herzschuh,2006).Peatlandservesasagoodarchiveforpaleoclimaticreconstruction,sinceexpansionandshrinkageofpeatlandrespondsensitivelytoclimaticchanges.Understandinghowpeatlanddevelopmentwasasso-ciatedwithpastclimaticconditionswouldprovideusefulinsightsintoprojectingfutureenvironmentalchanges.Mostpreviouspeatlandstud-ieshavefocusedontwomajorzones,highlatituderegions(50°–70°N)andtropicalregions(20°S–10°N;Zhaoetal.,2014).AbundantpeatlandsinnorthernandtropicalChina,suchasHani(Zhouetal.,2010),Hongyuan(Zhengetal.,2007)andDingnanbogs(Zhouetal.,2005;seelocationsinFig.1A)couldofferimportantinformationonpeatlandhistoriesinthemid-latituderegionoftheNorthernHemi-sphere(20°–50°N),connectingthetwomajorpeatlandregions.TheDajiuhupeatlandisawell-preservedsubalpinepeatlandinthewesternShennongjiaMountainsincentralChina(~30°N).Thickandcontinuouspeatdepositsallowforthereconstructionofpastenvironmentandcli-matechanges(Zhuetal.,2010).BecausethenearbySanbaoCavecon-tainshigh-qualitymonsoonalrecordsoverthelastglacial–interglacialcycle(Fig.1A,Wangetal.,2008),recordsfromtheDajiuhupeatlandwouldprovideagoodopportunitytodisentangletherelationbetweenthepeatlandecosystemevolutionandmonsoonalstrengthinthisregion.Recentdevelopmentsinorganicgeochemistryhaveintroducedmolecularbiomarkerstopaleoclimaticreconstruction(EglintonandQuaternaryResearch84(2015)255–261⁎Correspondenceto:Y.He,DepartmentofEarthSciences,ZhejiangUniversity,Hangzhou310027,China.⁎⁎Correspondenceto:C.Zhao,StateKeyLaboratoryofLakeScienceandEnvironment,NanjingInstituteofGeographyandLimnology,ChineseAcademyofSciences,Nanjing210008,China.E-mailaddresses:[e-mail](Y.He),[e-mail](C.Zhao).©2015UniversityofWashington.PublishedbyElsevierInc.Allrightsreserved.ContentslistsavailableatScienceDirectQuaternaryResearchjournalhomepage:ñedaandSchouten,2011).ManytypesofbiomarkershavebeenutilizedtoinferclimaticchangesintheDajiuhuregion,includingbranchedfattyalcohols(Huangetal.,2013a),hopanoids(Xieetal.,2013)andaromatictriterpenes(Huangetal.,2013b).However,noneofthesestudiesinvolven-alkanes,atraditionalbiomarkerforbothlacustrine(e.g.,Heetal.,2014)andpeatlandstudies(e.g.,Binghametal.,2010;Zhouetal.,2010).Asetofn-alk