32ForestSoilBacteriaDiversityInvolvementin

ForestSoilBacteria:Diversity,InvolvementinEcosystemProcesses,andResponsetoGlobalChangeSalvadorLladó,RubénLópez-Mondéjar,PetrBaldrianLaboratoryofEnvironmentalMicrobiology,InstituteofMicrobiologyoftheCAS,Vestec,CzechRepublicSUMMARY........................................................................................1INTRODUCTION..................................................................................2BACTERIALCOMMUNITIESINFORESTECOSYSTEMS......................................4BacterialCommunitiesonPlantLitterandDeadwood.....................................4BacteriainForestSoils........................................................................7RhizosphereBacterialCommunities..........................................................8BACTERIALINVOLVEMENTINECOSYSTEMPROCESSES....................................9RoleofBacteriaintheCarbonCycle.........................................................9RoleofBacteriainNitrogenandPhosphorusCycles......................................12EFFECTSOFGLOBALCHANGEONBACTERIALCOMMUNITIESINFORESTECOSYSTEMS..............................................................................13CarbonDioxide...............................................................................14GlobalWarming..............................................................................14NitrogenDeposition.........................................................................17CONCLUSIONS..................................................................................18ACKNOWLEDGMENTS.........................................................................19REFERENCES.....................................................................................19AUTHORBIOS...................................................................................27SUMMARYTheecologyofforestsoilsisanimportantfieldofresearchduetotheroleofforestsascarbonsinks.Consequently,asignificantamountofinfor-mationhasbeenaccumulatedconcerningtheirecology,especiallyfortemperateandborealforests.Althoughmoststudieshavefocusedonfungi,forestsoilbac-teriaalsoplayimportantrolesinthisenvironment.Inforestsoils,bacteriain-habitmultiplehabitatswithspecificproperties,includingbulksoil,rhizosphere,litter,anddeadwoodhabitats,wheretheircommunitiesareshapedbynutrientavailabilityandbioticinteractions.Bacteriacontributetoarangeofessentialsoilprocessesinvolvedinthecyclingofcarbon,nitrogen,andphosphorus.Theytakepartinthedecompositionofdeadplantbiomassandarehighlyimportantforthedecompositionofdeadfungalmycelia.Inrhizospheresofforesttrees,bacte-riainteractwithplantrootsandmycorrhizalfungiascommensalistsormycor-rhizahelpers.Bacteriaalsomediatemultiplecriticalstepsinthenitrogencycle,includingNfixation.Bacterialcommunitiesinforestsoilsrespondtotheeffectsofglobalchange,suchasclimatewarming,increasedlevelsofcarbondioxide,oranthropogenicnitrogendeposition.Thisresponse,however,oftenreflectsthespecificitiesofeachstudiedforestecosystem,anditisstillimpossibletofullyin-corporatebacteriaintopredictivemodels.Theunderstandingofbacterialecol-ogyinforestsoilshasadvanceddramaticallyinrecentyears,butitisstillincom-plete.Theexactextentofthecontributionofbacteriatoforestecosystemprocesseswillberecognizedonlyinthefuture,whentheactivitiesofallsoilcommunitymembersarestudiedsimultaneously.KEYWORDSbacteria,decomposition,ecosystemprocesses,forestecology,globalchange,litter,nutrientcycling,soilPublished12April2017CitationLladóS,López-MondéjarR,BaldrianP.2017.Forestsoilbacteria:diversity,involvementinecosystemprocesses,andresponsetoglobalchange.MicrobiolMolBiolRev81:e00063-16.©2017AmericanSocietyforMicrobiology.AllRightsReserved.AddresscorrespondencetoPetrBaldrian,baldrian@biomed.cas.cz.S.L.andR.L.-M.contributedequallytothisarticle.REVIEWcrossmJune2017Volume81Issue2e00063-16mmbr.asm.org1MicrobiologyandMolecularBiologyReviewsonApril12,2017byguest(1).ForestecosystemsarefoundinmostofEarth’sbiomesandharboralargeproportionoftheglobaldiversity.Forexample,temperateandborealforestsoccupymostofthelandsurfaceoftheNorthernHemisphereandcontain46%ofalltreesonEarth—0.66and0.74trillion,respectively(2).Duetotheirglobalextension,theprocessesoccurringinthesetwobiomesareofglobalimportance,andanunderstand-ingofthecompositionandfunctionoftheirmicrobiomesisthusessential(Fig.1).Foreststypicallyrepresentimportantcarbon(C)sinkswithlargeamountsofrecal-citrantorganicmatterintheirsoils,especiallythetemperateforestsoils,whichreceivetonsoflitterperhectareyearly(3).Thepresenceoflargetreesdistinguishesforestsfromgrasslands,wetlands,andagriculturalareasinmultipleways(4).Treesrepresentamultitudeofhabitats,suchasthephyllosphereorrhizosphere,buttheyalsosub-stantiallyaffecttheremainingpartsoftheecosystem.Thisismainlybecause,asthedominantprimaryproducers,theysupplythebulkoftheCthaten