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LETTERSoilmicrobialcommunitiesdrivetheresistanceofecosystemmultifunctionalitytoglobalchangeindrylandsacrosstheglobeManuelDelgado-Baquerizo,1,2*DavidJ.Eldridge,3VictoriaOchoa,2BeatrizGozalo,2BrajeshK.Singh4,5andFernandoT.Maestre2AbstractTherelationshipbetweensoilmicrobialcommunitiesandtheresistanceofmultipleecosystemfunctionslinkedtoC,NandPcycling(multifunctionalityresistance)toglobalchangehasneverbeenassessedgloballyinnaturalecosystems.Wecollectedsoilsfrom59drylandecosystemsworldwidetoinvestigatetheimportanceofmicrobialcommunitiesaspredictorofmultifunctional-ityresistancetoclimatechangeandnitrogenfertilisation.Multifunctionalityhadalowerresis-tancetowetting–dryingcyclesthantowarmingorNdeposition.Multifunctionalityresistancewasregulatedbychangesinmicrobialcomposition(relativeabundanceofphylotypes)butnotbyrich-ness,totalabundanceoffungiandbacteriaorthefungal:bacterialratio.OurresultssuggestthatpositiveeffectsofparticularmicrobialtaxaonmultifunctionalityresistancecouldpotentiallybecontrolledbyalteringsoilpH.Together,ourworkdemonstratesstronglinksbetweenmicrobialcommunitycompositionandmultifunctionalityresistanceindrylandsoilsfromsixcontinents,andprovidesinsightsintotheimportanceofmicrobialcommunitycompositionforbufferingeffectsofglobalchangeindrylandsworldwide.KeywordsBacteria,carbon,fungi,multifunctionality,nitrogen,phosphorus,resistance.EcologyLetters(2017)20:1295–1305INTRODUCTIONSoilmicrobesarethemostabundantanddiverseorganismsonEarth(Fierer&Jackson2006;Locey&Lennon2016).Recentexperimentsandobservationalstudieshaveshowedthat,consistentwithreportedobservationsforplantcommu-nities(Cardinaleetal.2011;Maestreetal.2012;Soliveresetal.2016),soilmicrobialdiversityplaysanimportantroleinmaintainingmultipleecosystemfunctionssimultaneously(i.e.multifunctionality)interrestrialecosystems(Philippotetal.2013;Waggetal.2014;Delgado-Baquerizoetal.2016).Thesefunctionsinclude,butarenotlimitedto,litterdecomposition,nutrientcycling,primaryproductionandtheregulationofgreenhouseemissions(Philippotetal.2013;Waggetal.2014;Delgado-Baquerizoetal.2016;Liuetal.2017).Conversely,theroleofmicrobialcommunitiesinregulatingtheresistanceofmultifunctionality(multifunctionalityresistancehereafter)toglobalenvironmentalchangedriversremainslargelyunex-ploredandpoorlyunderstood(Orwinetal.2006;DeVriesetal.2012;deVries&Shade2013).Identifyingthemajormicrobialdrivers(composition,diversityorabundance)ofmultifunctionalityresistanceiscrucialfordevelopingsustain-ableecosystemmanagementandconservationpolicies.Suchknowledgewillhelpinprioritisingfutureprotectionofmicro-bialattributesinvolvedinmultifunctionalityresistance,withimplicationstoreduceimpactsfromclimatechangeandland-useintensificationonterrestrialecosystems.Existingknowledge,basedmostlyontheresultsofsmall-scalecontrolledexperiments,suggeststhatparticularsoilmicrobialattributes(e.g.fungal:bacterialratio)mightregu-latetheresistanceofparticularecosystemfunctions(e.g.soilrespirationorNmineralisation)toglobalchangedriverssuchaslanduseintensificationanddrought(Orwinetal.2006;Downing&Leibold2010;DeVriesetal.2012;deVries&Shade2013).However,welackdirectempiricalevidencetoidentifyhowmultiplemicrobialattributes,includingtheabun-dance,richnessandcompositionofsoilbacteriaandfungi,regulatetheresponseofmultifunctionalitytoglobalchangedrivers,particularlyattheglobalscale.Microbialattributessuchasabundance,richnessandcommunitycompositioncouldplayimportantrolesindrivingmultifunctionalityresis-tancetoglobalchange(MRGChereafter),astheyconstituteimportantregulatorsofmicrobialgrowth,microbialinterac-tionsandkeyfunctionalattributesbelongingtoparticulartaxa(e.g.nitrification).Furthermore,littleisknownabouthowchangesinthecompositionofmicrobialcommunities1CooperativeInstituteforResearchinEnvironmentalSciences,UniversityofColorado,Boulder,CO80309,USA2DepartamentodeBiologıa,Geologıa,FısicayQuımicaInorganica,EscuelaSuperiordeCienciasExperimentalesyTecnologıa,UniversidadReyJuanCarlos,c/Tulipans/n28933,Mostoles,Spain3CentreforEcosystemScience,SchoolofBiological,EarthandEnvironmentalSciences,UniversityofNewSouthWales,Sydney,NSW2052,Australia4HawkesburyInstitutefortheEnvironment,WesternSydneyUniversity,Penrith2751,NSW,Australia5GlobalCentreforLandBasedInnovation,UniversityofWesternSydney,BuildingL9,LockedBag1797,PenrithSouth,NSW2751,Australia*Correspondence:E-mail:m.delgadobaquerizo@gmail.com©2017JohnWiley&SonsLtd/CNRSEcologyLetters,(2017)20:1295–1305doi:10.1111/ele.12826acrosssuchscales(e.g.dissimilarityacrosssites;b-diversity)affectMRGC,particularlyindrylands.Theseecosystemsalreadycover~45%ofEarth’slandmass(Pravalie2016),andareexpectedtoincreasebyupto23%bytheendofthe21stcenturyduetoforecastedincreasesinaridityunderclimatechange(Huangetal.2016).AchievingabetterunderstandingofhowdrylandsoilmicrobesdriveMRGCisparticularlyimportantbecause:(1)microbialcommunitiesarehighlyaffectedbychangesinaridity(Maestreetal.2015),(2)dry-landsareoverrepresentedindevelopingcountries(Huangetal.2016)and(3)38%oftheglobalpopulationishighlyreliantonth