2014Floodingtoleranceandhorizontalexpansionof

See discussions, stats, and author profiles for this publication at: tolerance and horizontal expansion ofwetland plants: Facilitation by floating mats?ARTICLE in AQUATIC BOTANY · JANUARY 2013Impact Factor: 1.61 · DOI: 10.1016/j.aquabot.2013.11.003CITATIONS8READS823 AUTHORS:Bert HiddingWitteveen+Bos16 PUBLICATIONS 205 CITATIONS SEE PROFILEJ. M. SarneelUmeå University29 PUBLICATIONS 185 CITATIONS SEE PROFILEElisabeth S BakkerNetherlands Institute of Ecology (NIOO-KN…60 PUBLICATIONS 1,236 CITATIONS SEE PROFILEAvailable from: Elisabeth S BakkerRetrieved on: 05 March 2016AquaticBotany113(2014)83–89ContentslistsavailableatScienceDirectAquaticBotanyjournalhomepage::Facilitationbyfloatingmats?BertHiddinga,∗,JudithM.Sarneela,b,ElisabethS.BakkeraaDepartmentofAquaticEcology,NetherlandsInstituteofEcology(NIOO-KNAW),POBox50,6700ABWageningen,TheNetherlandsbLandscapeEcologyGroup,DepartmentofEcologyandEnvironmentalSciences,UmeåUniversity,SE90187Umeå,SwedenarticleinfoArticlehistory:Received24April2013Receivedinrevisedform5November2013Accepted7November2013Availableonline6December2013Keywords:WaterlevelfluctuationsFacilitationFloatingmatsStratiotesaloidesRiparianvegetationHydroseresuccessionabstractWaterlevelfluctuations(WLF)canbeimportantdisturbancespromotingthediversityofriparianplantcommunities,butarecurrentlyabsentfrommanymanagedaquaticecosystems.AlackofWLFisthoughttoreduceplantdiversityandhamperhydroseresuccession.However,apositiveimpactofWLFonplantdiversitymaycruciallydependonnutrientavailabilityandthepresenceofapotentialecosystemengi-neer,thefloatingplantStratiotesaloides,thatmayprovidestructuralsupporttoriparianplants.Wetestedtheinteractiveeffectsof40cmflooding,presenceofS.aloidesandsedimentnutrientavailability(NandP)ongrowthandhorizontalexpansionofeightwetlandplantspeciesina10weekexperiment.Sevenoutofeightspeciesshowedasignificantelongationresponsetoflooding.Comparedtostagnantwaterlevels,floodingincombinationwithhighnutrientavailabilitydecreasedhorizontalexpansionintwoshortspeciesandincreaseditintwotallspecies,whereasfloodingdecreasedhorizontalexpansionintwoothershortspeciesunderbothnutrientlevels.Inthis10weekexperiment,weobservednoeffectofS.aloidesonthemeasuredplantparameters.Thisexperimentshowsshort-termnegativeeffectsoffloodingonmostoftheshortspecies.Onthelong-term,wehypothesizethatimprovementsinwaterqualityandseedlingrecruitmentduetodrawdownmayresultinnetpositiveeffectsofWLFintheriparianzone,butasthespeciesthatwererareinthefieldhappenedtobeshort,careshouldbetakentomaintainrarespecieswhenallowingmoreWLF.©2013ElsevierB.V.Allrightsreserved.1.IntroductionDisturbancesarethoughttopotentiallyenhancespeciesdiver-sityincommunitiesbecauseatamoderatelevelofdisturbancespecieswithdifferentresponsestosuchdisturbancesmaycoexist(Connell,1978;Roxburghetal.,2004).Recruitmentofsubordinatespeciescanbefacilitatedbydisturbances(BakkerandOlff,2003;Hiddingetal.,2010b)whiledominantscanpersist.Disturbancesmaybegeneratedbiotically,forinstancebydisease,bioturbationorherbivory,ortheymaybegeneratedabiotically,throughfire,droughtorflooding.In(semi-)aquatichabitatswaterlevelfluctu-ations(WLF)mayformsuchtypeofdisturbanceandthereforethediversityofwetlandvegetationmaybeenhancedthroughintra-annualvariationinwaterlevels(RiisandHawes,2002;VanGeestetal.,2005a;Janssonetal.,2005).Lackofwaterlevelfluctuationsmayundersomecircumstancespromotehypoxiaofthewatercol-umnandofthesediment(Bunchetal.,2010).Waterdrawdown∗Correspondingauthor.Presentaddress:LeibnizInstituteofFreshwaterEcologyandInlandFisheries,Müggelseedamm301,12587Berlin,Germany.Tel.:[phone].E-mailaddresses:[e-mail],[e-mail](B.Hidding).mayprovideoxygentothesedimentandpromotetheestablish-mentofsubmergedaquaticvegetation(VanGeestetal.,2007).Inaddition,thedisturbancedynamicsrelatedtoWLFmayfavorcoex-istencebetweencompetingwetlandspecies(Bonisetal.,1995;VanEcketal.,2004)andcreatewindowsofopportunityfortherecruit-mentfromseeds(CasanovaandBrock,2000).Thenaturalvariationinwaterlevel,whichoftenexhibitsaseasonalpatternwithlowwaterlevelsinsummerandhighwaterlevelinwintermaypro-motelake-wardexpansionoffringingvegetation,asestablishedfrompaleorecords(Korhola,1992).However,WLFmayhavenegativeconsequencesforwetlandplantdiversityaswell(ZoharyandOstrovsky,2011).Theflip-sideofpositivedrawdowneffectsisthepossibilityoffloodinginspringorsummer.Suchscenariocanbecommonwithexcessiveprecipi-tationinspringand/orwhenlakesareinfluencedbywaterlevelsinrivers(VanGeestetal.,2005b).Undersuchascenario,plantsmayexperienceCO2andO2shortage(e.g.MommerandVisser,2005;Perataetal.,2011)andachangedlightclimate,inparticularwhenthefloodingwateristurbid.Plantsgrowinginfrequentlyfloodedareashaveevolvedmechanismsoffloodingmitigationsuchasshootelongationorquiescence(Voeseneketal.,2006),whichulti-matelyaffectstheirdistributionalongfloodinggradients(Mommeretal.,2007)andsubsequentlycommuni