15Nitrogenrichmicrobialproductsprovidenewor

AcceptedArticleThisarticlehasbeenacceptedforpublicationandundergonefullpeerreviewbuthasnotbeenthroughthecopyediting,typesetting,paginationandproofreadingprocess,whichmayleadtodifferencesbetweenthisversionandtheVersionofRecord.Pleasecitethisarticleasdoi:10.1111/gcb.14009Thisarticleisprotectedbycopyright.Allrightsreserved.DR.PETERMARTINKOPITTKE(OrcidID:0000-0003-4948-1880)Articletype:PrimaryResearchArticlesNitrogen-richmicrobialproductsprovideneworgano-mineralinteractionsforthestabilizationofsoilorganicmatterRunninghead:StabilizationofsoilorganicmatterPeterM.Kopittke1,*,MariaC.Hernandez-Soriano1,RamC.Dalal1,DamienFinn1,NealW.Menzies1,CarmenHoeschen2,CarstenW.Mueller21TheUniversityofQueensland,SchoolofAgricultureandFoodSciences,St.Lucia,Queensland,4072,Australia2TechnischeUniversitätMünchen,LehrstuhlfürBodenkunde,D-85350Freising,Germany*Email:[e-mail],Phone:[phone],Fax:[e-mail],[e-mail],[e-mail],[e-mail],[e-mail],[e-mail],[e-mail]:Nano-scalesecondaryionmassspectrometry(NanoSIMS);organo-mineralinteractions;stableisotopes;soilcarboncycling;soilcarbonstorageAcceptedArticleThisarticleisprotectedbycopyright.Allrightsreserved.Typeofpaper:PrimaryresearcharticleAbstractUnderstandingthecyclingofCandNinsoilsisimportantformaintainingsoilfertilitywhilealsodecreasinggreenhousegasemissions,butmuchremainsunknownabouthoworganicmatter(OM)isstabilizedinsoils.Weusednano-scalesecondaryionmassspectrometry(NanoSIMS)toinvestigatechangesinCandNinaVertisolandanAlfisolincubatedfor365dwith13Cand15Npulselabelledlucerne(MedicagosativaL.)inordertodiscriminatenewinputsofOMfromtheexistingsoilOM.WefoundthatalmostallOMwithinthefreestablemicroaggregatesofthesoilwasassociatedwithmineralparticles,emphasizingtheimportanceoforgano-mineralinteractionsforthestabilizationofC.Ofparticularimportance,itwasalsofoundthat15N-richmicrobialproductsoriginatingfromdecompositionoftensorbeddirectlytomineralsurfacesnotpreviouslyassociatedwithOM.Thus,wehaveshownthatN-richmicrobialproductspreferentiallyattachtodistinctareasofmineralsurfacescomparedtoC-dominatedmoieties,demonstratingtheabilityofsoilstostoreadditionalOMinnewlyformedorgano-mineralassociationsonpreviouslyOM-freemineralsurfaces.Furthermore,differencesin15NenrichmentwereobservedbetweentheVertisolandAlfisolpresumablyduetodifferencesinmineralogy(smectite-dominatedcomparedtokaolinite-dominated),demonstratingtheimportanceofmineralogyinregulatingthesorptionofmicrobialproducts.Overall,ourfindingshaveimportantimplicationsforthefundamentalunderstandingofOMcyclinginsoils,includingtheimmobilizationandstorageofN-richcompoundsderivedfrommicrobialdecompositionandsubsequentNmineralizationtosustainplantgrowth.AcceptedArticleThisarticleisprotectedbycopyright.Allrightsreserved.IntroductionReducinglossofsoilorganiccarbon(OC)stocksisessentialformaintainingsoilfertility(forfood,fiber,andfuelproduction)whilstalsodecreasingemissionsofgreenhousegases.Asaresult,themarkeddeclineofsoilOCstocksworldwideandassociatedsoildegradation(Donetal.,2011,Kopittkeetal.,2017)isofinterestnotonlyinregardtofoodsecurity,butalsobecausetheconcomitantreleaseofcarbondioxideisanimportantcontributortoclimatechange(Schmidtetal.,2011).However,inordertodevelopappropriatestrategiestoincreasesoilorganicmatter(OM),wefirstrequireabetterunderstandingoftheprocessesinfluencingthedynamicsofOMinsoil.OfparticularinterestarethemechanismsthatcontrolstabilizationofOMinsoil(Lehmann&Kleber,2015).ThemajorityofOMenteringsoilsisrecognizableplantlitter,butmostismineralizedwithinmonthsofitsaddition(Kerréetal.,2016).AcomparativelysmallportionofthisaddedC,however,maybestabilizedwithinthesoilforhundredsofyears,orlonger.Traditionally,ithasbeenassumedthatthreemainfactorsdeterminethestabilityofOMinsoils(Sollinsetal.,1996),being(i)thechemicalcomplexity(i.e.recalcitrance)ofthecompoundsandtheirresistancetomicrobialdegradation(Schmidtetal.,2011),(ii)theformationoforgano-mineralinteractions(Lützowetal.,2006,Kleberetal.,2007),and(iii)physical(spatial)inaccessibilityoftheoccludedOCtomicrobialcommunities(Ekschmittetal.,2008,Dungaitetal.,2012,Solomonetal.,2012).Althoughconsiderableuncertaintyremains,itseemsincreasinglylikelythatthefirstofthesethreefactorsisnotsupported(Kleberetal.,2011,Schmidtetal.,2011,Dungaitetal.,2012,Lehmann&Kleber,2015).Inthepresentstudywefocusoncharacterizingorgano-mineralassociations(i.e.thesecondofthethreefactors).IdentificationoftheseunderlyingfactorsinfluencingthedistributionandturnoverofCfollowingtheadditionofnewinputstosoilwouldadvanceourabilitytopredictchangesinCstocksacrossvaryingsoils.AcceptedArticleThisarticleisprotectedbycopyright.Allrightsreserved.StableisotopeanalysesarewidelyusedtoidentifydifferentsourcesofCinsoil(Kerréetal.,2016).Withthecomparativelyrecentuseofnano-scalesecondaryionmassspectrometry(NanoSIMS)inthefieldofsoilscience,itisnowpossibletomapisotopesacrosssoilparticlesatalateralresolutionofca.100nm(Re