Huang2011GeochemJLipidsinleavesandroots

365GeochemicalJournal,Vol.45,pp.365to373,2011*Correspondingauthor(e-mail:[e-mail])Copyright©2011byTheGeochemicalSocietyofJapan.al.,2004,2010;Jansenetal.,2006;Kuhnetal.,2010;Mendez-Millanetal.,2010).Inordertoacclimatizetothespecificconditionsofpeatlands(waterlogged,nutri-entpoorandpartlyanoxicandacidic),plantsdevelopshallowbutflourishingrootsystems(RydinandJeglum,2006),whichcancontributehighamountoflipidstopeatdeposits.Todate,onlyPancostetal.(2002)notedtheroot-derivedlipidsfrompeat-formingplants.Anumberofstudieshavereportedthelipidcomposi-tionsofpeatlandplantcommunities(Fickenetal.,1998;Nottetal.,2000;Pancostetal.,2002;Nicholsetal.,2006).ThesecommunitiesweredistributedinEuropeandNorthAmerica,whiletheresultsinotherregionswerenotavailableintheliteraturetothebestofourknowl-edge.Inaddition,exceptforthepeatmoss(Sphagnumspecies)shrubsareabundantintheabovebogs.Incon-trast,theDajiuhuPeatlandischaracterizedbySphagnumpalustreandvariousherbaceousplants.Itis,therefore,worthassessingthelipidcompositionoftheplantcom-munityinsuchanherbpeatland.Then-alkanedistribu-tionsofseveralmossspecies(S.palustre,Aulacomniumpalustre,PolytrichumcommuneandHypnumrevolutum)fromtheareahavebeenpreviouslyreportedbyHuangetal.(2010).ComparisonoffreelipidcompositionsbetweenrootsandleavesofplantsintheDajiuhuPeatland,centralChinaXIANYUHUANG,1CANFAWANG,2JINXIANGZHANG,1GUIDOL.B.WIESENBERG,3ZHIQIZHANG4andSHUCHENGXIE2*1StateKeyLaboratoryofGeologicalProcessesandMineralResources,ChinaUniversityofGeosciences,Wuhan430074,China2KeyLaboratoryofBiogeologyandEnvironmentalGeology,MinistryofEducation,ChinaUniversityofGeosciences,Wuhan430074,China3DepartmentofAgroecosystemResearch,UniversityofBayreuth,Bayreuth95440,Germany4AdministrationofDajiuhuNationalWetlandParkofShennongjia,Shennongjia442417,China(ReceivedNovember16,2010;AcceptedApril30,2011)ThemainaimofthisstudywastoassessthefreelipidcompositionofplantcommunityinaChinesepeatland.TwelveplantspeciesfromtheDajiuhuPeatlandwereanalyzedforthecompositionsofn-alkanes,n-fattyalcoholsandsterolsinleavesandroots.Thelipidcompositionsaresignificantlydifferentbetweenrootandleafformostplants.Insomecases,therootsyieldmorelongchainn-alkanesandn-alkanolsthantheleavesofthecorrespondingplant.Thelongchainn-alkanesoftherootsinhalfoftheplantspeciesarecharacterizedbyahigherCmax(homologuewiththemaximumconcen-tration)relativetotheleaves.Theroot-derivedsterolsandsteroidalketonesmaybeimportantsourcesforcorrespondingcompoundswithinthepeat.Becauseofthedifferentlipidcompositionsofrootsandleaves,moreattentionshouldbepaidtoroot-derivedlipidsforinvestigationsofthelipidcompositionandtheirsourceassessmentinsoilsandterrestrialsediments,whereroot-derivedorganicmattercanbeanimportantsource.Thecontributionofroot-derivedlipidsmaybeespeciallyimportantinpeatlands,whereacidicand/oranoxicconditionsinthesubsoillimitthedegradationoforganicmatterandthecontributionofleaflitter.Keywords:plantroots,n-alkanes,n-alkanols,peatland,steroidalketonesINTRODUCTIONThefreeandboundlipids(n-alkanes,n-fattyalcoholsandsteroids)contributeagreatpartoforganicmatterpreservedinsoilsandsediments,andthesecanbeusedasbiomarkersfortheirsourceplantsandtheassociatedenvironmentalconditions(e.g.,Rieleyetal.,1991;MeyersandIshiwatari,1993;Schwarketal.,2002;Xieetal.,2004;WiesenbergandSchwark,2006;Huangetal.,2008).Toeffectivelyinterprettheoriginofthelipidsinsoilsandsediments,itiscrucialtoinvestigatehowandwherelipidsaredistributedinmodernplants.How-ever,moststudieshavefocusedonleafwaxes(e.g.,Rieleyetal.,1991;Fickenetal.,1998,2000;Schwarketal.,2002;Bietal.,2005;Jansenetal.,2006;Rommerskirchenetal.,2006;Cuietal.,2008;Griceetal.,2008;Huangetal.,2011).Therehavebeenfewerreportsofroot-derivedlipidsandtheirsignificanceforsedimentaryorganicmat-ter(Ottoetal.,1994;Pancostetal.,2002;Wiesenberget366X.Huangetal.Inthisstudy,wecomparedthefreelipiddistributionsinrootsandleavesofplantspeciescollectedfromtheDajiuhuPeatland.TheaimofthisstudywastoevaluatethecompositionofrootlipidsrelativetoleaflipidsintheplantcommunityofthispeatlandincentralChina.MATERIALSANDMETHODSSamplingTheDajiuhuPeatlandinShenongjiaForestryRegion,HubeiProvince,China,hasdevelopedinasub-alpineclosedbasin(over1700mabovesealevel)andextendsoveranareaofabout16km2.Thepeatsedimentsreachathicknessofmorethan2m.ThepHofthemodernsurficialpeatisca.4–5,andthewatertableisnormally10–50cmbelowthesurficialhorizons(Huangetal.,2010).ThelocalclimateisdominatedbytheEastAsianmonsoon,withameanannualrainfallof1560mmandameantem-peratureof7.2°C.Withinthepeatland,Sphagnumpalustreisthedominantcoverplant,togetherwithherbaceousplantssuchasCarexspp.,JuncuseffususandEuphorbiaesula.ThetwelvemostabundantplantspecieswerecollectedforrootandleaflipidanalysisfromtheDajiuhuPeatlandinJune,2009.Forthesamplestoberepresentative,overtenindividualplantswerecollectedforeachspecies.AlltheplantsareherbsexceptthefernDryopterissp.ExtractionandfractionationPlantsampleswerecarefullywashedwithdeionizedwater,dividedintorootsandleaves,andthencutintosmallpiecesusingscissors.Theleafandrootpar