21Climatewarmingleadstodivergentsuccessiono

Letters:XueGuo,JiajieFeng,ZhouShi.*e-mail:[e-mail];[e-mail]tionsrequireanunderstandingoftheeffectsofwarmingonecologicalcommunitiesandtheunderlyingmechanismsthatdrivethem1–3.However,littleisknownabouttheeffectsofclimatewarmingonthesuccessionofmicrobialcommunities4,5.Hereweexaminedthetemporalsuccessionofsoilmicrobesinalong-termclimatechangeexperimentatatall-grassprairieecosystem.Experimentalwarmingwasfoundtosignificantlyalterthecommunitystruc-tureofbacteriaandfungi.Bydeterminingthetime-decayrelationshipsandthepaireddifferencesofmicrobialcommu-nitiesunderwarmingandambientconditions,experimentalwarmingwasshowntoleadtoincreasinglydivergentsucces-sionofthesoilmicrobialcommunities,withpossiblyhigherimpactsonfungithanbacteria.Variationpartition-andnullmodel-basedanalysesindicatethatstochasticprocessesplayedlargerrolesthandeterministiconesinexplainingmicrobialcommunitytaxonomicandphylogeneticcomposi-tions.However,inwarmedsoils,therelativeimportanceofstochasticprocessesdecreasedovertime,indicatingapoten-tialdeterministicenvironmentalfilteringelicitedbywarming.Althoughsuccessionaltrajectoriesofmicrobialcommunitiesaredifficulttopredictunderfutureclimatechangescenarios,theircompositionandstructureareprojectedtobelessvari-ableduetowarming-drivenselection.Theaccelerationofglobalclimatewarming,aconsequenceofthebuild-upofatmosphericCO2andothergreenhousegasesduetofossilfuelcombustionandlandusechange,representsoneofthegreatestscientificandpolicyconcernsinthetwenty-firstcentury1.Asclimate,especiallytemperature,isaprimarydriverofbiologicalprocesses6,climatewarminghasimpactedterrestrialbiodiversityatallsystemlevels7,8,includingshiftingspecies’geographicalrange7,phenology8,distributionandabundance7,allofwhichcouldpoten-tiallyincreasetheriskofextinction9,alteringcommunitystructure10anddisruptingecologicalinteractionsandecosystemfunctioning11.Consequently,itisanticipatedthatclimatewarmingwillalterpat-ternsinspatialandtemporaldistributionsoforganisms12.However,despiteintensivestudiesexaminingtheresponsesofecologicalcom-munitiestoclimatewarming13,whetherandhowclimatewarmingaffectstemporalsuccessionofecologicalcommunities,particularlymicrobialcommunities,remainselusive.Asknowledgeofthetemporaldynamicsofecologicalcommuni-tiesiscriticalforpredictingtheresponsesofbiodiversity,ecosystemfunctionsandservicestoenvironmentalchange(forexample,cli-matewarming),ecologicalsuccessionhasalwaysbeenatthecoreofcommunityecology10,14.Stages,trajectoriesandmechanismsarecentraltopicsinsuccessionalstudies14.Thesuccessionofecologicalcommunitiescanbeconvergent,divergent,idiosyncraticorothercomplexformsinlinearornonlinearfashions14,15.Previousstud-iesshowedthatplantsuccessionsweredivergent16,convergent16–18orshowednosignificantchange17,andsometimesallpatternsappearedwithinthesamestudy18.Moreover,successionaldirectioncouldbedependentonbothspatialandtemporalscales16,19,ecosys-temcharacteristics19,typesofperturbation19,andfunctionaltraitsused20.However,onlyafewstudiesexaminedtemporalsuccessioninmicrobialcommunities,andthoseshowedconvergent21ordiver-gent19,22,23behaviours.Inthelastdecades,variousmanipulated,multifactorial,climatechange,fieldexperimentshavebeenestablished10,13,18,24,andofferuniqueopportunitiesforexaminingthetemporalsuccessionofter-restrialecosystemsinresponsetoclimatechangeacrossmultipleenvironmentalconditions.Therefore,inthisstudy,weexaminedthetemporalsuccessionofsoilmicrobialcommunitiesinresponsetoexperimentalwarminginanative,tall-grassprairieecosystemoftheUSGreatPlainsinCentralOklahoma(34°59ʹN,97°31ʹW)24.Thislong-termmultifactorclimatechangeexperimentwasestab-lishedin2009,andthewarmingtreatmentplotshavebeensub-jectedtocontinuous+3°Cwarmingbyinfraredradiators24.Inthisreport,weprimarilyfocusonthewarmingeffectsonmicrobialcommunitysuccessionbydetermining:whetherandhowwarmingwillaltertemporalsuccessionratesofthegrasslandsoilmicrobialcommunitiesacrossdifferentorganismalgroups(forexample,bac-teriaandfungi);whetherwarmingwillleadtodivergentorcon-vergentsuccessionofsoilmicrobialcommunities;andwhattherel