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WetlandvegetationofinlandAustralia

ForAustralianvegetation,ed.D.A.Keith,3rdedn.

JaneA.Catford1,2,3*,JaneRoberts4,SamanthaJ.Capon5,RayH.Froend6andSarasM.

Windecker1andMichaelM.Douglas7

1SchoolofBioSciences,TheUniversityofMelbourne,Vic3010

2FennerSchoolofEnvironment&Society,TheAustralianNationalUniversity,ACT

2601

3DepartmentofEcology,Evolution&Behavior,UniversityofMinnesota,StPaul,MN

55108,USA

4InstituteofAppliedEcology,UniversityofCanberra,ACT2617

5AustralianRiversInstitute,GriffithUniversity,Nathan,QLD4111

6SchoolofNaturalSciences,EdithCowanUniversity,Joondalup,WA6027

7SchoolofEarthandEnvironment,UniversityofWesternAustralia,Perth,WA6009,

*AddressfromJuly2016:CentreforBiologicalSciences,UniversityofSouthampton,

UniversityRoad,Southampton,SO171BJ,UK(emailJ.A.Catford@soton.ac.uk)

This is the final author-version (not type-set or copy-edited) of the following book chapter:

Catford, J.A., Roberts, J., Capon, S.J., Froend, R.H., *Windecker, S.M. & Douglas, M.M. (2017) Wetland vegetation of inland Australia. Australian Vegetation (ed. D.A. Keith). Cambridge University Press.p. 490-515. DOi: 10.1017/9781316339701

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Abstract

Wetlandsfedbyrainwater,surfaceflowsandgroundwateroccurthroughoutAustralia,even

inaridareas.Thischapterfocusesontemporarywetlandsandpermanentlywetsystems

thataredominatedbynon-woodymacrophytes,andusesninecasestudiesthatspan

Australiatoillustratetheirbiogeography,dynamicsandkeythreats.Thetypeand

distributionofwetlandvegetationreflectshydrology,climateandgeomorphology,fromthe

annuallyfloodedwetlandsofnorthernAustralia,tosalinelakesofaridandsemi-arid

Australia,togroundwater-dependentsystemsofthesouthwest,tobogsandfensoftheAlps

andTasmania.Wetlandplantshavedevelopedarangeofadaptationsandlifehistoriesto

toleratethedynamicwaterregimescharacteristicofAustralianwetlands,andcanbe

groupedintosevencategoriesthatreflecttheseadaptations.Waterbirdsandwatercan

connectspatiallyisolatedsystems,andseedbanksthatlastfordecadesallowspeciesto

dispersethroughtime.Waterregimeisastrongdriverofspeciescompositionand

abundance,thushydrologicalmodificationthroughwaterextraction,flowregulationor

reductionsinrainfallisasignificantthreattowetlandflora,andarguablytheprincipalthreat

forAustralianwetlandvegetation.Thedisplacementofnativemacrophytesbyexoticand

terrestrialspeciesisbothasymptomandcauseofecologicalchange,withexoticplants

oftenbeingbetteradaptedtomodifiedfloodingandfireregimes,livestockgrazingand

eutrophicationthannatives.Introducedlivestockandferalfaunaeat,trampleanduproot

nativeplants,anddegradetheirhabitat.Thesetypesofthreatsareexpectedtointensify,

increasingthechallengeforwetlandmanagementandpolicy.

Introduction

WetlandsareamongthemostvariableandproductiveofEarth’secosystems.Theyare

highlyvaluabletohumansandofcrucialimportanceforecosystemhealth.Beingatthe

interfaceoflandandwater,wetlandsarehomeandhosttonumeroustaxa,from

phytoplanktontomacroinvertebrates,tobirdsandmammals.Wetlandsoccurthroughout

Australia,varyingfrompermanentlywettoalmostpermanentlydry.Fedbyrainwater,

rivers,surfaceflowsandgroundwater,theboundariesofmanywetlandsshiftseasonally,or

inresponsetolongerclimaticcycles,asinundationvaries.Waterbirdsandwatercan

connectseeminglyisolatedsystems,allowingplantsandtheirpropagulestodispersewidely.

Thediversityofthesesystemsismirroredbythediversityoftheflorathatinhabitsthem.

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ThischapterexploresthetypesofwetlandsthatoccurinAustralia,usingcasestudiesto

illustratetheirbiogeographyanddynamics,andthekeydriversthatshapetheirvegetation.

OverhalfofAustralia’swetlandshavebeendestroyedsinceEuropeansettlement(Bennett

1997);weoutlinethemaindriversofthisloss,aswellassomemanagementandpolicy

initiativesdesignedtoarrestandameliorateit.Weprovideanoverviewofthemajorfactors

andprocessesaffectingwetlandvegetation,andgiveexamplesofwetlandplant

adaptations.

Wefocusontemporaryandpermanentwetlandsthataredominatedbynon-woody

macrophytes(orhydrophytes,i.e.plantsadaptedtolivinginwater,saturatedsoilorvery

moistsoil)andcanbecharacterisedbywaterregimesinvolvingperiodicorpermanent

inundationorwaterlogging.ThehighvariabilityofrainfallandrunoffinAustraliameansthat

someAustralianwetlandsmayonlyfloodonceeveryseveralyears,andpossiblylessoftenin

ephemeralaridzoneriversystems(Capon2003).Wetlandsfedbygroundwaterarebuffered

againstthisvariabilitybutbeingusuallyquitesmallandrelativelyfewaccountforonlya

smallpercentageofAustralia’swetland.Althoughmuchofthematerialdiscussedinthis

chaptercanapplytovegetationinflowingwaters,wefocusonvegetationoflentic(standing

orslowflowingwater)systems.

Driversofwetlandvegetation

Numerousabiotic,bioticandhumanfactorsaffecttheenvironmentalconditions,dispersal

opportunitiesandbioticinteractionsthatshapewetlandvegetation(Boultonetal.2014).

Theinfluenceoftheseinteractingfactorsdeterminesthebiogeographyandecologyof

wetlandvegetation(Fig.1).

Hydrologyisthekeyforcestructuringwetlandandriparianvegetation.Hydrologyrefersto

thedistributionandquantityofwaterinthelandscape.Hydrologyatthewetlandlevelis

characterisedbythewaterregime,whichencapsulatestheduration,frequency,magnitude,

timing(seasonality),rateofchange,andvariabilityofwettinganddrying.Wetlandsmay

experienceextremesinphysico-chemicalconditionsasaresultofchangingflooding

conditions.Becauseofdifferenthydrologicalconditionsassociatedwithwetlandbathymetry

(underwatertopography),wetlandvegetationtypicallyformszones(ormosaics)

demarcatedbysubtlechangesinwaterdepthorinundationduration(Fig.2).Thespecies

thatoccurineachzoneusuallyhavephysiological,morphologicalorlifehistoryadaptations

forthoseparticularhydrologicalandenvironmentalconditions(BrockandCasanova

1997).

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Wetlandhydrologyisintegrallylinkedwithgeomorphology(thephysicalformofthe

catchment,wetlandandassociatedwaterways)andhydraulics(flowdynamicsandvelocity),

andthesethreefactorsinteractcloselytoaffectotherkeydrivers.Togetherwithwater

quality(includingnutrientfluxes,sedimentloadsandioniccomposition)andsoiland

sedimentcharacteristics(lithology),thesefactorsdeterminethekeyenvironmental

conditionsaffectingwetlandvegetation(Fig.1).Plantsandanimalsmayaffecttheabiotic

characteristicsofasitebyalteringitsphysicalorchemicalcharacteristics.Forexample,

fallentreesaffecthydraulicsandchannelform,andcommoncarpdisturbthesediment,

uprootingplantsandincreasingturbidity.

Wetlandbiotamaytoleratechanginghydrologicalconditions,butmanycompletetheirlife

cyclesduringperiodsinwhichenvironmentalconditionsaresuitable.Theabilitytocolonise,

growandreproducequicklyduringsuchtimes,andpersistinadormantstatewhen

conditionsareunfavourable,isparticularlyimportantunderboom-and-bustconditions

(Bunnetal.2006).Dispersalintimeandspaceisthereforecrucialforspeciespersistence.

Plantscaneffectivelydispersethroughtimebystoringpropagules(ordiaspores:seeds,

sporesandvegetativefragmentsthatcandevelopintoanindividualplant)inseedbanksin

thesoil,litterandheldinplantcanopies.Indesertwetlandsthatmayonlybeinundateda

fewtimesacentury,seedsmustbeabletosurviveinterveningdryperiods,andgerminate

whenappropriatefloodingconditionsarise(Brocketal.2003).Liketerrestrialplants,

wetlandplantsdispersebyarangeofmechanism,includingvariousmeans,includingvia

wind,animalandself-propulsion,andmanyalsospreadclonallythroughaboveground

stolonsandbelowgroundrhizomes.However,alargefractionofwetlandplantsalsouse

waterasameansofdispersal(hydrochory),andsomemaybedispersedbyfruit-eatingfish

(ichtyochory;thoughthereappearstobenoevidenceofichtyochoryinAustralia:Jane

Roberts,pers.comm.2015)(CatfordandJansson2014).Water-bornedispersalenables

propagulestoreachsitesthatarehydrologicallyconnectedandlikelytohavesuitable

environmentalconditions.Hydrologicalconnectivityreferstopermanentandtemporary

connectionsamongwetlandsandother(mostlyaquatic)systems;itincludeslateral,

longitudinal(inthecasesofriverinewetlands)andvertical(surfacetogroundwater)

connections(Fig.1).

Waterbirdsareeffectiveindispersingpropagulesoverlongdistancestohydrologically

disconnectedsystems.Suchlongdistancedispersalfacilitatesspecies-andpopulation-

mixingamongwetlands,andcontributestothewidegeographicdistributions,spanning

continentsandbeyond,ofmanywetlandplantspecies.Wetlandsthatareisolated,likesmall

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dischargespringsfedbygroundwater,offerfeweropportunitiesforlongdistancedispersal

andlevelsofendemismaresubsequentlyhigherthaninmoreconnectedsystems,like

floodplainwetlands.

Likeanyvegetation,wetlandvegetationisaffectedbyinteractionswithothertrophiclevels

andwithothertypesofvegetation.Terrestrialvegetationmaycompetewith(orfacilitate)

wetlandvegetationunderdrierconditions,andherbivoresmaymodifytheabundanceof

certainspecies.Asdiscussedbelow,humansaffectwetlandvegetationdirectlyand

indirectlybyalteringenvironmentalconditions,dispersalopportunitiesandbiotic

interactions.Owingtotheinterplayofsomanyfactors,thedynamicsofwetlandscanbe

quitediverse,yettherearecommonalitiesasthecasestudiesbelowillustrate.

Ecologyandfloristicsofwetlandplants

Adaptationsofwetlandplants

Wetlandplantshaveadaptedtospecificfloodinganddryingcycles,andthisisparticularly

evidentinregenerationanddispersal.

Germinationandrecruitmentdirectlyaffectsplantcommunitycomposition.Waterregimes

caninfluenceplantphenology(thetimingofperiodicevents,suchasfloweringandseedset)

byprovidingcuesforgerminationanddispersal,aswellassuitableconditionsforseedling

growth(PettitandFroend2001).Floodingcanbreakdormancybycausingasuddenincrease

insalinityafterdroughtinaridorsemi-aridsystems(Nielsenetal.2007).

Althoughnotallwetlandplantsdispersebywaterandhydrochorousspeciesrarelydisperse

exclusivelybywater,waterisimportantfordispersalintwomajorways–asavectorandas

atriggerfordispersal.Attributesofpropagulesthatfacilitatehydrochoryinclude:buoyancy;

corkyorspongytissueoflowdensity;waxy,cuticularizedepidermis;andsurfaceswith

furrows,pitsorhairsthatcanenhancefloatingability(CatfordandJansson2014).In

climateswithpredictableseasonalpatterns,someriparianplantstimethereleaseof

propagulestocoincidewithparticularphaseoftheriverhydrograph.Thisadaptation

increasesthelikelihoodthatpropaguleswillbetransportedanddepositedonrecently

floodedsoils,providingconditionsfavourableforgerminationandrecruitment.Ifthe

seasonalflowpatternsarechanged,forexamplebyriverregulation,nativeplantsmayno

longerreleasepropagulesatoptimaltimes.Thesummer-autumntimingofpeakflowsin

regulatedriversinVictoriacoincideswiththeseedreleaseofexoticspecies,whereasnative

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riparianspeciesreleaseseedsinwinter-springwhenflowswerehistoricallyattheirhighest

(Greetetal.2012).

Functionaltypesofwetlandplants

Macrophytescanbeclassified intogroupsbasedontheiradaptationsto,andtoleranceof,

flooding.Themost commonlyusedwetlandplant classification scheme inAustralia is that

developedbyBrockandCasanova(1997).Thishierarchicalschemeclassifieswetlandplant

species into three main groups, Submerged, Amphibious and Terrestrial (with seven

subgroups)basedon their lifehistoryandresponse to flooding (Table1).Casanova (2011)

updatedthescheme,butweprefertherelativesimplicityoftheoriginalone.

TheTerrestrialgroupcomprisestwosub-groups,Terrestrial-dryandTerrestrial-damp.

Terrestrial-dryareunabletotolerateflooding,sooccurabovethehighwatermark

(Terrestrialdryspecies,Table1,Fig.2b).Terrestrial-dampspeciesarefoundaround

wetlands,reflectingtheirneedfordampsoilandtheirtoleranceofinfrequentinundation

(seealsospeciesdescribedinChapterXXonFloodplainforestsandwoodlands).

PlantsintheAmphibiousgroupareeitherTolerators,plantsthattoleratefluctuationsin

waterlevel,orResponders,plantsthatrespondtothem.AmphibiousTolerator-emergent

areoftenthedominantandmostconspicuoustypeofwetlandvegetation(Fig.2b,c).These

speciesareabletotoleratefluctuationsinwaterlevelsbyensuringthatasufficientportion

(roughlytwothirdsoftheirabovegroundbiomass)isabovethewater,allowingfor

respiration.AmphibiousToleratorlowgrowingspeciesgenerallycontributearelativelysmall

fractiontotheplantbiomassinawetland.

TherearetwotypesofAmphibiousResponders:plasticandfloating(Fig.2a,d,e,f).Plastic

specieschangetheirmorphologyandform,andmayhaveheterophyllousleaves,which

differwhethersubmergedoremergent(e.g.Sagittariaplatyphylla,Fig.2f).Waterliliesarea

classicexampleoffloatingresponders,astheirlonginternodesorpetiolesallowleavesto

floattothesurfaceofthewaterevenifitsdepthfluctuates(Brock2003).Floating

respondersincludessomeofthesmallestwetlandplants(Spirodela,LemnaandWolffia

species;seeFig.2e)andinvasiveexoticplants(Fig.2d),includingEichhorniacrassipes(water

hyacinth)andSalviniamolesta(salvinia,seeChapterXXonInvasiveplantsandplant

pathogens).

Submergedplantsgrowbelowthesurfaceofthewaterandhaveadaptationsthatenable

themtogerminate,growandreproduceentirelyunderwater.Submergedplantscannot

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tolerateexposuretoair.AswellasangiospermslikeVallisneriaspecies,manyofthe

submergedtaxaarecharophytes(freshwatergreenalgae),e.g.CharaandNitellaspecies.

TrendsinAustralianwetlandvegetationscience

WetlandplantecologyandwetlandvegetationscienceinAustraliawereintheirinfancy

priortothe1970s,mirroringglobaltrends(Fig.3).EarlystudyofAustralianwetlandplants

wasprincipallyconcernedwithspeciesandhabitatdescriptions(includingtaxonomy),and

aquaticweedmanagementinirrigationchannels.

Themainemphasisonemergentmacrophytesinthe1970sand1980sreflectedscientific

andmanagementprioritiesatthattime.Emergentmacrophyteswererecognisedasdrivers

oflakeecologyandappealedtomanagementinterestsbecauseoftheiruseasa“green”

alternativetotreatingwastewaterinconstructedwetlands(Brix1987).Australianresearch,

onEleocharissphacelataandTyphadomingensisforexample,alsocontributedto

internationalinterestinmacrophyteadaptationstoanoxicandhypoxicsubstrates(e.g.

Sorrelletal.1997).

Researchonsalinityandwaterregimedominatedwetlandvegetationresearchfromthe

1990sonwards.Salinityexperimentsinthe1990sbuiltonresearchfromthe1970sand

1980sbyaskingmorecomplexquestions,suchasidentifyingtolerancesofmacrophytes

usingconcentrationgradientsingrowthtrials.Experimentsinthe2000sconsidered

interactionsbetweensalinityanddrying,exploredgeographicvariabilityandinterpreted

findingsintermsofbiodiversity(Goodmanetal.2011).

Investigationsintowaterregimeshaveprogressedfromassessingtheresponseoffew

speciestoasingle-hydrologicvariable(e.g.emergentmacrophytesalongadepthgradient,

ReaandGanf1994),tocomparingmultiplespecies,totheinteractionofthewholewater

regimewithsalinity,sedimentationorplantcommunitycomposition(e.g.Catfordetal.

2011).Inparallel,perspectivehasshiftedfromshort-termquestions(suchaswithin-year

patternsofgrowth,resourceallocationandreproduction)toestablishingtheroleofwater

regimethroughouttheplantlifecycleandoverlargespatialscales.Yearsofresearchhave

revealedthatwetlandplantsemploymanystrategiestocopewithvariablehydrology.More

recently,scientistshavebuiltonthebodyofknowledgeofalteredwaterregimestotest

theoreticalquestions,forexampleofinvasionbiology(Catfordetal.2011).

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Australiahasmadeasignificantcontributiontowetlandecologythroughseedbankstudies.

Initiallyseedbankstudiesweredescriptive,andintentoncharacterisingseeddensityand

speciesrichness,understandingspatialandtemporalvariability,andestablishingtheroleof

hydrologyasadriverofthisvariability.Theyhavesincebecomeapowerfultoolallowing

comparisonamongwetlands,evaluationofantecedentconditions,scenariotesting,impact

assessment,andameansofestablishingrecoverypotentialandresilience.Oneoutcomeof

seedbankresearchinAustralialedtothedevelopmentofamacrophyteclassificationsystem

(BrockandCasanova1997).

Consistentwithglobaltrendsandterrestrialplantecology,wetlandsciencehasseen

growingemphasisoncharacterisingspeciesbasedontheirmorphology,responsesto

environmentalstimuli(e.g.flooding)andeffectsonecosystemfunctionandservices

(CatfordandJansson2014).Thisshiftismotivatedbythegreatergeneralisationthattrait-

basedclassificationscanoffertoecologyandmanagement:understandingplantresponses

andeffectsbasedonspeciescharacteristicsratherthanspeciesidentityallowsfindings

gatheredinonestudyandoneregiontobeappliedelsewhere.

Thefocusonsalinityandwaterregimehasnecessarilyresultedinfewerstudiesdedicatedto

otherenvironmentalfactors:forexample,effectsoffireandtemperatureonwetland

vegetationarepoorlyunderstoodoutsideofalpineandsub-alpineareas.Theshort-term

effectsofnativeherbivores(mainlywaterbirdssuchasblackswansandmagpiegeese),

exoticlivestock(cattle,horses,pigs)andexoticbenthivorousfish(commoncarp)onwetland

vegetationandseedbanksmaybelocallyknown,butthecumulativeanddifferentiallong-

termeffectsofbiotaonfloristiccompositionandstructureneedfurtherstudy.Plant-plant

interactions,factorsmaintainingdominanceorfacilitatinginvasion,andthenurseryeffects

ofstructurallydominantspecies(Jamesetal.2015),havebeeninvestigatedonlyrarely,and

consequentlytheirimportanceinstructuringwetlandplantcommunitiesislikely

underappreciated.

Casestudiesofwetlandtypes

WetlandsarefoundthroughoutAustralia,withtheirtypeanddistributionreflectingtheir

hydrology,climate(particularlyrainfallandevaporation)andtopographicandmorphological

features(Fig.1,Brock2003).NorthernAustraliahaswetsummers,southerncoastalpartsof

Australiathataretemperatehavewetwinters,andthearidandsemi-aridinterior,which

makesuptwothirdsofthecontinent,hashighlyunpredictablerainfall.Iffedbyrainfall,

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surfacerunofforriverflows,wetlandhydrologyreflectstheseclimaticpatterns.Floodingis

highlypredictableandseasonalinthetropics,whereasthesalineandepisodicwetlandsthat

dominatearidandsemi-aridregionscanbecharacterisedbytheir(wet)boomand(dry)bust

cycles.Seasonalorintermittentwetlandsaremorecommonnearthecoast,andwetlands

thataremorepersistentoftenoccurwhererainfallexceeds1000mmannually(Boultonet

al.2014;Brock2003).Incontrasttowetlandsfedbysurfacewater,manygroundwater-fed

systemsnaturallyhaveapermanentsupplyofwater.Springsfedbygroundwatercan

seeminglyoccurinunlikelyplaces,providingrareoasesinthemiddleofthedesert,buttheir

distributionreflectsthelocationofcracksandfissuresintheaquitardsthatconfine

groundwaterorwheresedimentsthatformtheaquiferprojectabovetheground(Fensham

andFairfax2003).Wetlandsfloodedbyriversarenecessarilyfoundalongriverchannels.The

distributionofwetlandsischangingassurfaceandgroundwaterisusedandregulatedby

humans,asclimaticpatternschange,andaswetlandsareinfilledandtheircatchments

modified.Theninecasestudiespresentedbelowillustratesomeofthisdiversity.

Floodplainwetlandsofthewet-drytropics

OneofthemoststrikingfeaturesofnorthernAustraliaistheextensiveareasoffloodplain

associatedwithmanyofitslargeriversystems(Fig.4a).Wheninflood,thewholeexpanseof

ariverfloodplaincanbeinundated;wetlandsarenotjustrestrictedtolowerelevationareas

ofthefloodplain.Inthelowerrainfallregions,suchastheGulfofCarpentariaandthe

Kimberley,floodplainsmayonlybeinundatedforafewweeksayearandcontainveryfew

vascularplants.Incontrast,wetlandsinthehigherrainfallregionsmaybeinundatedforup

tohalfoftheyearandsupportexpansiveareasofaquaticmacrophytes,grassesandsedges

(Pettitetal.2011).Theselattersystemshavebeenthefocusofmuchofthepastresearch

ontropicalfloodplainwetlands,particularlyintheAlligatorRiversRegioninKakaduNational

Park(Finlayson2005).Formedonly1,500–6,000yearsago,thesetropicalfloodplainsare

relativelyrecentgeomorphologicalfeaturesandcontainaflorathatiscommontomany

othertropicalregionsoftheworldwithlessthan25%oftheplantspeciesendemicto

northernAustralia(Cowieetal.2000).

Thepronouncedseasonalityoftherainfall,andassociatedpatternsofannualfloodingand

drying,istheprimarydriverofvegetationdynamicsintheregion.Localvariationin

vegetationcommunitycompositionreflectsmicrotopographyandlocaldifferencesin

inundation(Finlayson2005).Thepredictabilityofthetimingandmagnitudeoffloodsthat

drivewetlandplantdynamicsispositivelycorrelatedwithfishspeciesrichness,bird

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populationstabilityandriparianforestproductioninbothAustralianandSouthAmerican

floodplains(Jardineetal.2015).AfewspeciesdominatelargeareasofAustraliantropical

floodplains;forexample,Oryzaspecies(wildrice),Eleocharisspecies(spike-rush),

Hymenachneacutigluma(nativehymenachne),Pseudoraphisspinescens(watercouch)and

waterlilies(NymphaeaspeciesandNymphoidesspecies)(Finlayson2005).Althoughthese

systemsarerelativelylowinplantspeciesrichnesscomparedwiththesurroundingsavanna

landscape,theyarehot-spotsofprimaryproductionandsupportanabundanceoffauna,

particularlyfishandwaterbirds(Finlaysonetal.2006).RecentresearchonAustralia’s

tropicalriverecosystemshashighlightedtheimportanceofprimaryproductioninfloodplain

wetlands,particularlybyepiphyticalgae,forsupportingaquaticecosystemsofthe

floodplain,mainriverchannelandestuary(Jardineetal.2012).

Incontrasttomanyfloodplainsystemsinmorepopulatedregions,thehydrologyof

Australia’stropicalfloodplainsremainslargelyintact.However,theyhavebeenlistedasone

ofAustralia’stenmostvulnerablehabitatsduetoexoticplantinvasions,whichtransform

thestructureandfunctionofthesesystemsandtheriskofsealevelrise(Lauranceetal.

2011).InvasiveperennialgrassessuchasUrochloamutica(paragrass,Fig.4d)and

Hymenachneamplexicaulis(olivehymenachne)wereintroducedforcattlegrazingandhave

sincespreadlongdistancesassistedbyfloodsandwaterbirdsandnowcoverincreasingly

largeareasofsomefloodplains,includingthoseinKakaduNationalPark(Setterfieldetal.

2013).AlthoughsuccessfullymanagedinKakadu,theSouthAmericanwoodyshrubMimosa

pigra(Mimosa),isaseriousweedonseveralfloodplainsintheNorthernTerritory

(Setterfieldetal.2013).Theirlowelevation(mostare<2mabovesealevel)makesthese

coastalfloodplainshighlysusceptibletosea-levelrise(Catfordetal.2013),whichhas

alreadytransformedareasoffreshwaterwetlandtosalineswamp,includingmorethan

17,000haontheMaryRiverintheNorthernTerritory(MulrennanandWoodroffe1998).

Desertfloodplainwetlandsinaridandsemi-aridAustralia

DesertfloodplainsoccurthroughoutinlandAustraliabutareparticularlywell-developedin

theChannelCountryoftheeasternLakeEyreBasinand,toaslightlylesserextent,inthe

lowlandsofthewesternMurray-DarlingBasin(Caponetal.2016).Characterisedby

extremelylowtopographicgradientswithmeanannualrainfallbelow250mm,these

easterndesertfloodplainstypicallyencompasscomplexchannelnetworksthatdistribute

floodwatersovervastareasduringperiodsofhighriverflows.Incontrast,theephemeral

floodplainsofAustralia’scentralandwesterndesertsareusuallyassociatedwithpoorly

defineddrainagesystemsandaretypicallyinundatedbyflashyoverlandflows.Ineither

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case,thedefiningcharacteristicofdesertfloodplainsistheirhighlyvariableand

unpredictablepatternsofwettinganddrying,whichhaveanoverridinginfluenceonthe

compositionandstructureoftheirvegetation(Capon2005).

Desertfloodplainwetlandsencompassthewholefloodplainandarenotrestrictedto

depressionswithinthefloodplain.Theysupportadiverserangeofshortgrass,sedgeand

forbassociationsthatshiftincompositionandstructurebothtemporally,inresponseto

wettinganddrying,andspatiallyinrelationtofloodhistory(Capon2005).Plantspecies

inhabitingtheseenvironmentstendtobewidelydistributed,manyhavingcosmopolitan

distributionsextendingbeyondthearidzone(Boxetal.2008).Commonfamilies

representedincludeAsteraceae,Amaranthaceae,Chenopodiaceae,Cyperaceae,

Euphorbiaceae,Fabaceae,Goodeniaceae,Malvaceae,Nyctaginaceae,Poaceaeand

Polygonaceae.Manyspeciesmaintainlarge,persistentsoilseedbanks,whichenableplants

toavoidunfavourableconditions(e.g.drought)andre-establishwhensuitableconditions

arise,typicallyfollowingthedrawdownoffloodwaters(Capon2007).Inthearidzone,

woodyvegetationismostlylimitedtowatercoursesandtheirbanksoralongflood

strandlines.Furthertotheeasthowever,largeareasofsemi-aridfloodplainwoodlandsalso

occur(seeChapterXXXonFloodplainforests).Low-lyingswampyareasalsofrequently

supportwetlandshrublands(e.g.ofDumaflorulenta,Chenopodiumauricomum).

Waterresourcedevelopment,ofbothsurfaceandgroundwaters,probablyrepresentthe

greatestthreattoAustralia’sdesertfloodplains,governedastheyarebyhydrology.Land

useispredominantlylivestockgrazing.Althoughovergrazingmayhavesignificanteffectson

vegetationduringdryperiods(e.g.severevegetationcoverreduction,soilcompaction),

cattlehavelimitedaccesstovegetationwhenitisatitsmostproductiveanddiverse(i.e.

followingflooding)duetosurfaceinstability.Recentintensificationofminingexploration

andextractionalsoposeathreattodesertfloodplainvegetationasaresultofinfrastructure

development,wateruseandthedisposalofexcessgroundwater.Climatechangehasthe

potentialtofurtherinfluencevegetation,especiallywherewaterregimesarealtered.

Inlandsalinelakes

Salinelakesandwetlands,includinglakes,claypansandrain-filleddepressions,areamajor

featureofinlandAustralia,accountingforover80%oftotalwetlandareaonthecontinent

(TimmsandBoulton2001,alsoseeChapterXXonChenopodshrublandsandsaltlakes).

Additionally,manyfreshwaterlakesbecomesalineastheydry.Mostsalinelakesoccurin

WesternAustraliaandSouthAustralia(e.g.LakeEyre)buttherearealsomanyintheeastern

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mainlandstates.Mostareephemeralortemporary,butsomewetlands,especiallyin

southernAustralia,canbeseasonalorpermanent.Salinelakesalsovaryinwaveactionand

turbidity(TimmsandBoulton2001).

Vegetationcompositioninsalinelakesisdrivenbysalinity,waterregimeandturbidity

(Porteretal.2007).Speciesrichnesstypicallydeclineswithincreasingsalinityandisusually

greaterintemporary,ratherthanpermanent,lakes.However,onlyafewalgaland

angiospermspeciesarecapableofpersistingunderbothhighlevelsofsalinityandwidely

fluctuatingwaterlevels.Nevertheless,evenhighlysalinelakescansupportveryproductive

submergedvegetation(Brock1994).Rapidgrowthofsubmergedplantscanoccurunder

conditionsoflowturbiditywhensalinitiesarebelow~60gL-1(TimmsandBoulton2001).

Charophytes(e.g.NitellaspeciesandLamprothamniumspecies)aretypicallywell

representedandaquaticforbsareusuallydominatedbyspeciesofRuppiaandLepilaena.

Lakesareoftenfringedbysalt-tolerantsamphires(e.g.Halosarciaspecies,Tecticornia

species),succulents(e.g.Gunniopsisspecies)andsedges(e.g.Cyperusspecies).Forbsand

grassesmaycolonizesomeephemeralandtemporarysalinelakesduringdryperiods,but

somelakeswillformsaltcrustswhendryandremainfreeofvegetation(Porteretal.2007).

Threatstoinlandsalinelakesincludedrylandsalinization,whichhasbeenawidespread

resultofalteredhydrology(fromwaterextractionandriverregulation)andvegetation

clearinginsouthernAustralia,particularlysouth-westWesternAustralia(Halseetal.2003).

Drylandsalinity,alongwithadryingclimate,hasthepotentialtosignificantlyalterthe

salinityandwaterregimesofinlandsalinelakesinmuchofAustralia’ssouth.Increased

nutrientloadsinrunofffromsurroundingfarmsmayalsoposeathreat(Timms2005).

Extractionofmaterialsfromsalinelakes,aswellasfurtherchangestohydrologyresulting

frommininginfrastructureandwaterresourcedevelopment,arealsolikelytohave

significanteffects(Timms2005).

GroundwaterdependentspringsoftheGreatArtesianBasin

Springwetlandsarepermanentwetlandsfedbygroundwaterfromunderlyingaquifers.

SpringwetlandsoccurthroughoutAustraliabutareparticularlydistinctiveinarid

environmentswhere,asinothercountries,theyareoneofthefewsourcesofpermanent

water(Fig.4b,FenshamandFairfax2003).Springwetlandscanoccurinareaswhere

sedimentsthatformtheaquiferprojectabovetheground(outcropsprings).Theseinclude

springsinaquiferrechargeareaswhereratesofrainfall-derivedinflowexceedthroughflow

andwherewater-bearingsedimentsareclosetothegroundsurface,whichoftenoccursat

13

theedgesofanaquifer.Groundwaterfeedingoutcropspringscanhaveshortresidence

times(i.e.waterhasnotbeenintheaquiferforlong),sothesetypesofspringsmaybe

ephemeral.Dischargespringsoccurwherewaterflowsupwardsthroughconfiningbeds

(aquitard)viafaultsorconduitsintheoverlyingsediments(FenshamandFairfax2003).

Dischargespringsmaysustainsmallpermanentwetlandsbecausegroundwaterfeeding

thesesystemshasalongresidencetimeintheaquiferandthusshowsminimalfluctuations

inflowrates.

TheGreatArtesianBasinisanaquifersystemthatunderlies22%ofnorth-easternAustralia,

extendingoverpartsofQueensland,NSW,SAandNT(Powelletal.2015).Waterpercolates

throughthesandstoneaquifergenerallyinasouth-westerlydirection,withsandstoneintake

bedslocatedmainlyalongtheeasternmargininnorthQueensland(Powelletal.2015).

SpringsintheGreatArtesianBasinareoftenreferredtoasmoundsprings,butonlyasmall

fractionofspringwetlandshavevisiblemoundsassociatedwiththem.Moundsmaybe

formedbyupwellingofsubsoilintheartesianwater,fromvegetation-derivedpeat

accumulation,fromtheexpansionofsurfaceclaysandfromaccretionofaeoliansandor

calciumcarbonate(FenshamandFairfax2003).UnlikespringwetlandsinaridareasofWA

andNT,whicharethoughttohavegreaterconnectivity,thespringwetlandsoftheGreat

ArtesianBasinhavehighlevelsendemisminbothfloraandfaunaandarethusofhigh

conservationvalue.Of325nativevascularplantsrecordedintheGreatArtesianBasinspring

wetlands,atleasteightappeartobeendemic,withpresumablylittleopportunityfor

dispersaloutsideoftheseisolated,andenvironmentallyuniquesystems.Theseinclude

Myriophyllumartesum,Eriocauloncarsoniiandrelatedsubspecies,andSporoboluspamelae,

alongwithdescribedspeciesfromthefamiliesPoaceae,CyperaceaeandScrophulariaceae.

Atleast30exoticplantspecieshavealsobeenrecordedinthesewetlands(Fenshamand

Price2004).

SpringwetlandsintheGreatArtesianBasinareseverelythreatenedbygroundwater

extractionandaquiferdrawdown.Between1880and1990s,waterlevelsweredrawndown

byasmuchas100minpartsofQueensland.Asaresult,89%ofspring-groupshavebecome

inactivethroughoutmuchofQueenslandoverthelastcentury(FenshamandFairfax2003).

Thedischargespringsaremostaffectedbygroundwaterextractionand87%ofspringsinthe

dischargeareahavebecomepartlyorcompletelyinactiveduetogroundwaterdrawdown,as

opposedtoonly8%intherechargearea.Ofthespringsthatarestillactive,26%havebeen

severelydegradedthroughwetlandexcavation,whichisintendedtoincreaseaccessfor

livestock.Otherthreatsincludeexoticspeciesusedforpondedpasture(e.g.Hymenachne

14

amplexicaulis,Urochloamutica,Echinochloapolystachya),livestocktrampling,exotic

animals(e.g.pigrooting)andfire(FenshamandFairfax2003).Toprotecttheremaining

springwetlands,nomoreboresshouldbedevelopednearsprings,boresclosetosprings

shouldbecapped,andspringexcavationanduseofexoticpondedpastureshouldbe

prohibited(FenshamandFairfax2003).Greaterprotectionofspringwetlands,especiallyin

dischargeareas,throughthereservesystemwouldbevaluable.

Freshwaterwetlandsoncoastalfloodplainsofsouth-easternAustralia

CoastalfreshwaterwetlandsoccuraroundthecoastofAustraliaonsandyloamsoilsof

waterloggedorperiodicallyinundatedalluvialflats.Primarilyfedbyrivers,coastal

freshwaterwetlandsaresimilarinvegetationstructuretoinlandfloodplainwetlands,but

tendtobelocatedatelevationslessthan20mabovesea-level,havesandiersoils,higher

rainfall,andperiodicsalinewaterinput(Whiteheadetal.1990).RefertoChapterXXfor

Halophyticvegetation,includingcoastalmangrovesandsaltmarshes.

Vegetationcommunitiesincoastalfloodplainwetlandsarelargelydeterminedbyfrequency,

durationanddepthofinundation,butarebeingincreasinglyaffectedbyhumanactivities

thatincludelivestockgrazing,catchmentlandclearingandpollution(Pressey&Middleton

1982).Freshwaterwetlandsincoastalplainstypicallyhavelowcoverofwoodyspecies,

thoughwilloccasionallyhavescatteredtrees(e.g.Casuarinaglauca,Melaleucaericifolia)

thatarecommoninneighbouringswampfloodplainforests(deJong2000).Wetlandsthat

aredrymostofthetimearetypicallydominatedbydensegrassland,sedgeland,orrushland

under0.5mtall.CommonspeciesincludePaspalumdistichum,Leersiahexandra,

Pseudoraphisspinescens,andCarexappressa.Wetlandswithmoreregularcyclesof

inundationanddryingmaysupporttalleremergentspecies,suchasBolboschoenusspecies

andSchoenoplectusspeciesupto1mtall.CommonherbsintheseareasincludeHydrocharis

dubia,Philydrumlanuginosum,Ludwigiapeploides,Marsileamutica,andMyriophyllum

species.Aswaterlevelsbecomedeeperormorepermanent,thesesystemsbegintodevelop

morefloatingvegetationsuchasAzollaspecies,Lemnaspecies,Hydrillaverticillata,

Ceratophyllumdemersum,Nymphoidesindica,Otteliaovalifolia,andPotamogetonspecies.

Landdevelopmentisaparticularthreatforfreshwaterwetlandsalongthecoastbecauseof

thehighvalueoftheland,andbecausehighorganicmatterinthesedimentsoffreshwater

wetlandsmakethemidealforagriculturaldevelopment,includingexoticpasture.KooWee

RupSwamp,historicallylocatedalongthecoastbetweenMelbourneandGippsland,was

onceoneofthelargestfreshwaterwetlandsinVictoria.Extendingover40,000hectares,this

15

swampwasdrainedforagriculturein1876,destroyingdensestandsofswamppaperbark

(Melaleucaspecies)andgiantbulrush(Typhaspecies)(YugovicandMitchell2006).Coastal

wetlandsfilteroverlandflow,improvingwaterqualitybeforeitenterstheocean.The

degradationandlossofwetlandscanresultinincreasedsedimentandnutrient

concentrationsinrunoff,whichmayleadtoalgalblooms,increasedturbidity,andthe

degradationofmarineecosystems(Johnsonetal.1999).Coastalwetlandsarethemselves

threatenedbyeutrophication,especiallybynitrogenandphosphorusthatoriginatesfrom

urbanandagriculturalareas,whichresultsinthedisplacementofnativespeciesbyexotic

species.

Incoastalareas,wheremostofthepopulationresides,manywetlandswereeither

‘reclaimed’,viadrainageorinfilling,orregulatedbycontrolstructures(e.g.barrages)to

permiturbanandagriculturaldevelopment.Thisledtothefragmentation,degradationand

lossofalargeproportionofAustraliancoastalwetlands,whichcontinuetobeverypoorly

researchedecosystems.Insouth-westernWesternAustralia,around70%ofcoastal

wetlandsareestimatedtohavebeenlostsinceEuropeansettlement(Davisetal.2015).In

manycoastalregions,wetlanddrainageandlandusechangehavealsoledtotheexposure

ofunderlyingsulfidicsediments(i.e.acidsulfatesoils)withawiderangeofdetrimental

outcomesincludingdiminishedplantgrowth(Whiteetal.1997).

BillabongsandlakesofthesouthernMurray-DarlingBasinfloodplain

ThefloodplainsoftheMurray,MurrumbidgeeandGoulburnRiversareinsetwithtwomajor

typesofwetlandsthatdifferingeomorphology–billabongsandlakes(seeChapterXXon

Floodplainforeststhatdescribesthedrierpartsfloodplains).Thesefill,drawdownanddryin

responsetoriverinundation,whichvariesacrossthefloodplainresultinginamosaicof

waterregimes,rangingfromnearpermanenttoepisodic.

Billabongsareformerriverchannels,typicallysmall(surfacearea<10ha),mostlyclay-

based,andveryabundant,numberingthousandsperfloodplain.Thoughbillabongsmaybe

referredtoasoxbowlakes,billabongscantakemanyshapesandforms,andoftensimply

featureasdepressionsinthefloodplain(Fig.4c).Thediversityofwetlandplantswithina

billabongisstronglyinfluencedbywetlandform:deeperwetlandshavelittoralvegetation

ontheirslopesandsubmergedherblandontheirbedwhenflooded,whereasshallower

wetlandsmayhavesedgelandthroughout.Floodplainlakesaredeflationbasinswithaclay

orsandlunetteononemargin,typicallylarge(surfacearea100-600ha),andaregilgai,clay

orsand-based(ifnotin-filledbysediment):theynumbertenstohundredsperriversystem

16

(Pressey1986).Theircompactroundshapeanduniformfloorresultinlowenvironmental

heterogeneity,soindividuallakestypicallyhaveasingledominantvegetationtype.

Themosaicofwaterregimesoccurringacrossafloodplainmeansfloodplainwetlandsmay

carryacompletespectrumofgrowthforms,suchasriverredgum(Eucalyptus

camaldulensis)woodland,lignum(Dumaflorulenta)orchenopodshrubland,sedgeland,

varioustypesofgrassland,andvarioustypesofaquaticherbland,andthenumberofspecies

iscorrespondinglylarge.ThespeciespoolisamixofAustralianfamiliesandspecies

(MyrtaceaeandChenopodiaceaefortreesandshrubs),cosmopolitanorwidely-distributed

species(e.g.Phragmitesaustralis,Potamogetoncrispus),Australianaquaticandamphibious

representativesofcosmopolitanorwidely-distributedfamilies(Cyperaceae,Poaceae,

Typhaceae,Juncaceae,Juncaginaceae,Haloragaceae,Ranunculaceae,Elatinaceae,

Polygonaceae),andafewspecieswithrestricteddistributions(e.g.Amphibromusfluitans,

Myriophyllumporcatum).Althoughthespeciescompositionoffloodplainwetlandsishighly

variable,wetlandswithsimilarwaterregimeshavefunctionallysimilarplantcommunities

(Casanova2011).

Overthelast200years,floodplainsofthesouthernMurray-DarlingBasinhavebeen

dramaticallyalteredthroughvegetationclearing,cultivation,livestockgrazing,sediment

fluxes,alteredwaterquality,riverregulation,salinizationandacidification.Thewidespread

declineofsubmergedmacrophytesandhighabundanceandrichnessofexoticspecies

exemplifythis(Catfordetal.2011).Riverregulationisamajor(butnotsole)factor

determiningtheabundanceofexoticspecies.Inbillabongs,20-40%ofspeciesmaybeexotic,

andmostoftheseareshort-livedterrestrialspeciessuchaspasturegrassesoragricultural

weeds.Theirpresenceisalegacyofpastagriculturalenterprises(Luntetal.2012)buttheir

abundanceisboostedbythegenerallydrierconditionsthatriverregulationimposes.These

conditionshavethedualeffectofdisadvantagingthealreadyestablishednativeamphibious

speciesandofprovidingconditionssuitableforexoticterrestrialspecies,butnotnative

terrestrialspecies(Catfordetal.2011).Regulationdisruptsthematchbetweennative

speciesphenologyandfloods,andseasonalflowinversion(highflowsinsummer)favours

thedispersalandestablishmentofexoticspeciesgenerally(Greetetal.2012)thusriver

regulationexacerbatesthethreatofinvasiveexoticssuchasamphibiousNymphaea

mexicanaandSagittariaplatyphylla(Fig.4d&f).

Submergedmacrophyteabundanceanddiversityhasbeenadverselyaffectedbyi)increased

sedimentfluxfromerodeduplands,whichhasincreasedturbidityandreducedphoticdepth;

ii)exoticcommoncarp(Cyprinuscarpio)thatcandislodgemacrophytesthroughtheir

17

benthivorousfeedingstrategy,astrategynotusedbynativefish;andiii)theprolonged

MilleniumDroughtintheearly21stcentury.Tolerancetosuchpressuresrequirescapacityto

growunderlowlight,bulkyrhizomesandrelativelylong-livedseed(6-9years)thatcanaid

recolonisation(Brock2011).Onlytherobustperennial,Vallisneriaaustralis,isknownto

havethesecharacteristics.

BogsandfensoftheAustralianAlpsandTasmania

TheAlpineSphagnumBogsandAssociatedFensecologicalcommunitypredominantlyoccurs

intheAustralianAlpBioregion,whichspans375kmfromMountBawBawinVictoriato

southernNewSouthWalesandthewesternmarginofAustralianCapitalTerritory.These

communitiesarealsofoundinTasmania,andtypicallyoccurabovethetreelineinalpine,

subalpine,andmontaneenvironments.Thereisnostrictaltituderequirement,however,

sincelocalclimaticconditionscanenablethesecommunitiestoflourishatloweraltitudes

andbelowtheclimatictreeline.Alpinebogsandfensshelterendangeredplants,suchasthe

BogongEyebright(Euphrasiaeichleri),andaregenerallylessthan1hectareinsize

contributingtotheirprotectionundertheEnvironmentalProtectionandBiodiversity

ConservationActof1999.Forabroaderdescriptionofalpinevegetation,seeChapterXX.

Alpinebogsandfensarebothpeatlandecosystems.Peatisterrestrialsoilcomposedofat

least20%organicmatter,whichisatleast30cmdeep.Peatlandsoccurinareaswithhigher

waterinflowthanoutflow,orwherethereisalargesupplyofgroundwater.Waterlogged

soilproducesreduced,anaerobicconditionsthatinhibitactivityofmicrobialdecomposers,

allowingcarbon-richundecomposedplantremainstoaccumulate.Accumulationofplant

detritusintopeatcanproducesmalldams,whichfurthermodifyhydrologyinfavourof

continuingpeatformation.Dynamicgrowthofpeatlandscanproduceamosaicof

heterogeneoushabitatthatsupportsarangeofvegetationcommunities(Camill,1999).

Althoughalpinebogsandfensarebothcharacterisedbypresenceofpeatsoils,andoften

co-occurinthelandscape,theydifferinnutrientlevelsandthevegetationcommunitiesthey

support.Fensareprimarilyfedbysurfaceflowandgroundwater,whichisnutrientrich,and

supportsedgecommunitiesdominatedbyspeciessuchasCarexgaudichaudiana.Sphagnum

mossesaregenerallyabsentfromtheseareasastheyareoutcompetedbyplantsthatare

betterabletoexploithighnutrientenvironments.Bogs,incontrast,haveverylownutrient

levelsbecausetheymostlyrelyonrainwater(thoughstreamscanrunthrough“valley

bogs”).BogsoilsaregenerallymoreacidicandsupportsphagnummossessuchasSphagnum

18

cristatumandSphagnumnovozelandicumandsclerophyllousshrubsupto1mtallsuchas

Bossiaeafoliosa,Epacrisglacialis,andGrevilleaaustralis.

Alpinebogsandfensfaceanumberofthreatsrelatedtotheirrestrictedgeographicalextent

andsmallpatchsize.Therearemorethan11,000bogsandfensthroughouttheAustralian

AlpBioregion,thehighaltitudeareasofsouth-easternAustralia’sGreatDividingRange.

Theirsmallsizeandpatchydistributionmakethemdifficulttoprotectagainsttrampling

fromlivestockandferalanimals(e.g.horses,deer,pigs).Exoticungulates(e.g.cattle,sheep,

horses,pigs)tramplebogandfenvegetationandalsocreateincisionsinpeatsoilthatresult

inwetlanddrainage.

Presenceofwaterisvitalforthepersistenceofhydrophyticbogandfenvegetation,andso

threatsthatimpactwatersupplyorpeatstructuralintegrityendangertheselargelyendemic

communities(Wahrenetal.1999).Climatechangeispredictedtoincreaseoccurrenceand

severityofdroughtandfire,whichdamagepeat.Firescandestroycarbon-richpeat,

changingthephysicalstructureofbogandfensoilsandinhibitingtheirabilitytocaptureand

storewater.Modelspredictthatalpinebogsandfensaroundtheworldareamongthe

ecosystemsmostthreatenedbyclimatechange(Schuuretal.,2008).

Groundwaterdependentwetlandsofthesouthwest

Characteristicsoffreshwaterwetlandvegetationcommunitiesinsouth-westernAustralia

arelargelydeterminedbywetlandwatersource,sedimenttypeanddurationofinundation

(DEC2012).Thereisahighnumberofpermanentlyandseasonallyinundated,shallow(<3

m)wetlandsintheregionforwhichgroundwateristhedominantsourceofwater,either

fromlocalandregionalsuperficialgroundwaterorfromperchedgroundwaterheldbyan

impedingsedimentlayerthatisrechargeddirectlybyrainfall.

Despitehavingahot,dryMediterraneansummer,thesouthwestishometoflorathat

representstheworldcentrefordiversityinanumberofwetland-associatedplantfamilies

(e.g.Droseraceae,Restionaceae,Juncaginaceae,CentrolepidaceaeandHydatellaceae).The

vegetationcommunitiesincludearangeofendemicwetlandgenera(e.g.Reedia,

Cephalotus,Tribonanthes,Epiblema,Schoenolaena,Cosmelia,Euchilopsis,Acidonia,

Homalospermum,PericalymmaandTaxandria)andhighlevelsoflocalandregional

endemism.ThesouthernSwanCoastalPlainalonehasapproximately445wetland-

associatedplanttaxa,74%ofwhichareendemictoWesternAustraliaand3%endemicto

thesouthernSwanCoastalPlain(DEC2012).

19

ThedominantgrowthformsinSwanCoastalPlainwetlandsappeartoreflecttheseasonally

dryMediterraneanclimate.Thefloraisrichinshrubs,butherbsandsedgesmakeup77%of

taxa(Fig.4e).Although78%ofspeciesareperennial,22%oftheseregrowtheir

abovegroundbiomassfromundergroundstorageorganseachyear(DEC2012)–alikely

adaptationtoseasonaldroughtanddisturbancesuchasfire.

Seasonallywaterloggedwetlandsaretypicallymaintainedviaperchedgroundwaterand

havethegreatestdiversity(DEC2012).Thisfloristicdiversityreflectsspatialandtemporal

patternsinwaterlogging(e.g.duration),sedimentstratigraphy(e.g.distributionoforganic

fraction)andcompositionofimpedinglayer(e.g.ironstone,calcreteorgranite).These

systemsaredryinsummer,withtheplantdiversitynotbecomingapparentuntillatewinter

andspringwhenthesedgelandsandherblandsregrowfromtheirundergroundstorages.

Theytypicallysupportamosaicofvegetationunits,especiallywoodlands(dominatedby

EucalyptusrudisandMelaleucaspecies),shrublands(dominatedbyadiversesuiteofspecies

ofMyrtaceaee.g.Calothamnuslateralis,Melaleucateretifolia,M.viminea,Astarteaspecies,

Pericalymmaellipticum,Kunzeaspecies,Hypocalymmaangustifolium,andsome

Proteaceae),sedgelands,herblandsandrarelygrasslands.

Seasonallywaterloggedandperchedgroundwaterdependentwetlandswereonceextensive

inthesouthwest,particularlyontheSwanCoastalPlain,butduetolanddevelopmentand

hydrologicalchanges,manyarenowonlyrepresentedbyremnantportions(DEC2012).

GroundwaterlevelsontheSwanCoastalPlainhavebeendecliningsincethe1970sdueto

changesinclimate,landuseandgroundwaterextraction.Declininggroundwaterlevelshave

affectedvegetationingroundwater-dependentwetlandsinanumberofways,including:

reducedsurfacewaterlevelsandinsomecasesdryingandlossofwetlandhabitat;peat

fires;declininghealthanddeathofsomegroundwater-dependentvegetation;changesin

flowfromsprings/seeps;andacidificationofgroundwaterandwetlands(Sommerand

Froend2014).Withchanginghydrologicalconditions,manypermanent/semi-permanent

wetlandsaredevelopingvegetationcharacteristicsofseasonallywaterloggedwetlands,

whilstformerlywaterloggedareasarebeingencroachedbydrylandspecies.Longerperiods

ofexposed,drysedimentshavealsoleadtoincreaseddamagefromillegalvehicleaccess

anddisturbanceofsedimentsurfaces.Thewaterloggedfringesofmorepermanentwetlands

havealsobeenextensivelyreclaimedaswaterlevelsgraduallyfallandurbanisation

encroaches.

20

Artificialwetlands

Artificialwetlandsarewaterbodiesthatarewhollyorlargelyanthropogenicinorigin,in

contrasttonaturalwetlandsthathavebeenformedsolelybyhydrologicaland/or

geomorphicprocessesovertime.Theyaretypicallyusedforstockwatering(farmdams,

bore-fedwetlands),waterstorage(irrigationwaterstorages,weirpools,uplandreservoirs,

lowlandstorages),amenity(urbanlakesandponds,Fig.4f),watertreatment(wastewater

treatmentponds,pondsandmeadowsaspartofwater-sensitiveurbandesign)or

production(ricefields).Artificialwetlandsdifferfromnaturalwetlandsinbeingyounger,

andhavingdifferingcombinationsofsize,shapeandwaterregime:reservoirsandweirpools

areconsiderablydeeper;storagesandamenitylakesarepermanent;weirpoolsandamenity

lakeshavestablewaterlevels;ricefieldsprovideshallowclearwaterinspring-summerina

semi-aridregion.

Awetlandassemblagedevelops(orisplanted)thatisdominatedbynativespecies(Dugdale

etal.2009)butdistinctfromitsregionalequivalents(Badman1999).Riverinestoragesand

amenitylakesarenotableexceptionstonativedominance;theseareoftendominatedby

floatingorsubmergedmacrophytes,includinghighlyinvasiveexoticspecieslikeEgeria

densa,CabombacarolinianaandNymphaeamexicana(Fig.2d,Dugdaleetal.2009).

Characteristicsofartificialwetlandsthatmayconstrainvegetationassemblagesfrom

developingare:highturbidity,whichexcludessubmergedplants;waterdeeperthan1.5m

withsteepverticalbanks,whichprecludesthedevelopmentofalittoralzone;permanent

waterorextremefluctuationswhichprecludesuccessfulestablishmentandpersistence

(Casanovaetal.1997).

Hydrologicalconnectivityisvariable.Afewfarmdamsandallbore-fedwetlandsare

hydrologicallyisolated,andtheirplantassemblageshavedevelopedindependentlyof

hydrochory.Some,notablymeadowsinurbancontexts,areonlyintermittentlyconnected.

ThecontinuoushydrologicalconnectivityofriverinestoragessuchasLakeMulwalaonthe

RiverMurraymeansacontinualthreatofdownstreamdistributionofvegetativefragments

ofundesirablespecies.Althoughutilitarianinintent,artificialwetlandsmaydevelop

ecologicalvalueashabitatforfauna,suchaswaterbirds:anexampleistheRamsar-listed

WesternTreatmentPlantatWerribee,Victoria.

Summary

Theninecasestudiespresentedillustratecommonalityintheforcesthatstructurewetland

vegetationacrossAustralia,aswellastheprocessesthatthreatenthem(Fig.1).Theprimacy

21

ofhydrologyandwetlandwaterregimesfordeterminingthedistributionandcharacteristics

ofwetlandvegetationisparticularlyapparent.Itisthevariationineachofthesestructuring

forces,andinteractionsamongthem,thatgivetheplantcommunitiesofindividualwetlands

theirowncharacter.

Threats

Practicallyallwetlandsystems,withthenotableexceptionoftropicalfloodplainwetlands

andsomesprings,arethreatenedbychangesinwatersupplyandwaterregimes.Such

changesarecausedbytheextractionandregulationofsurfaceandgroundwater,with

modificationofsurfacewaterbeingparticularlypronouncedinsoutheasternAustraliaand

groundwaterextractionaffectingwetlandsincentralandwesternAustralia.Dependingon

thesysteminquestion,thechiefthreatmayinvolveanincreaseinwaterpersistence(i.e.for

wetlandsthatarenaturallyephemeralorintermittent)oradecrease(i.e.forwetlandsthat

arenaturallyalwayswet,likebogs,fensandsomesprings).Increasedwaterpersistence(e.g.

arounddamsandweirpools)canleadtotreedeathandshiftstowardsspeciesfavouredby

stablewaterlevels,e.g.Typhaspecies(Blanchetal.2000),whereasreductionsinflooding

canleadtowetlandlossorresultinnativemacrophytesbeingreplacedbywoodyspecies

(Bren1992)andexoticterrestrialherbs(Catfordetal.2014).Climatechangealsothreatens

wetlandhydrology,asillustratedinalpinebogsthreatenedbydecliningrainfallandrunoff,

andincoastalsystemsatriskofsaltwaterintrusionsfromrisingsealevels.Overall,climate

changehasthecapacitytoreducenativewetlandplantdiversity,promoteexoticinvasions,

acceleratewetlandfragmentationandhomogenisewetlandecosystemsatlocaland

landscapescales(Caponetal.2013).

ExoticspeciesarethreatsthroughoutAustralia,andarebothasymptom(e.g.inresponseto

flowregulationalongtheRiverMurray,seeCaseStudies)andacauseofchangesinnative

flora(e.g.exoticpasturesthatoutcompetenativevegetation,FenshamandFairfax2003).

Fifteenofthe32WeedsofNationalSignificanceinvaderiparianoraquaticsystemsandwere

intentionallyintroduced(seeChapterXXonInvasiveplants).Pondedpastureandother

exoticpasturescontinuetobeplanted,andnewvarietiesthatwilllikelyincreasetheir

invasionsuccesscontinuetobedeveloped(Driscolletal.2014).Exoticanimalsalsothreaten

nativeplantsdirectlythroughgrazing,tramplinganduprooting(e.g.ungulates,carp)and

indirectlythroughsoilcompactionorincreasedgullyerosion,forexample.Changesinthe

landuseofwetlands(e.g.livestockaccesstoalpineandMurray-DarlingBasinwetlands)and

theircatchmentsforagriculture,urbanisationandincreasinglymininghaveledto

22

sedimentation,pollutionandeutrophication,salinization,acidification,changestohydrology

andconnectivityamongwetlands.

Managementandpolicy

Policyrelatingtowetlandvegetation

Thefirstnationalpolicyonwetlandmanagementwasreleasedin1997(TheWetlandsPolicy

oftheCommonwealthGovernmentofAustralia).Whilstallstatesandterritorieshave

legislationtoprotecttheenvironmentandconservenaturalresources(e.g.environment

protection,landuseplanning,protectedareas,waterandvegetationmanagement),state-

levelpoliciesrarelyaddresswetlandsandwetlandvegetationdirectly.In2013,theNational

WetlandsPolicyforAustraliawasinitiatedandisdesignedtoimprovealignmentof

AustralianGovernment,state/territoryandcommunityactionandinvestment,andprovide

consistencyindecision-makingacrossgovernmentagencies(WetlandCareAustralia2013).

Whoisresponsibleforthemanagementofwetlandvegetation?

ThemanagementofwetlandsandassociatedvegetationinAustraliaisprimarilythe

responsibilityoflandownersandlandmanagers.Individualstatesorterritorieshavethe

legislativeandpolicyresponsibilityfornaturalresourcemanagement(Finlay-Jones1997).

TheAustralianGovernmentadministerstheRamsarConventiononWetlandsof

InternationalImportancebyprovidingnationalwetlandpolicy,leadershipanddirection.It

alsoimplementstheEnvironmentProtectionandBiodiversityConservationAct1999(EPBC

Act),anddevelopsprogramstoimprovethemanagementofwetlands.TheEPBCAct

specifiesthatanyactivitieswithinoroutsidedesignatedRamsarwetlandsthatarelikelyto

haveasignificantimpactontheecologicalcharacteroflistedwetland,includingthe

vegetation,mustbeapproved.Managersmayalsoneedapprovalfromtherelevantagencies

understatelegislationforactivitiespotentiallyimpactingRamsarlistedandnon-Ramsar

listedwetlands.Indigenousmanagementofwetlandvegetationcontinuesinmuchofthe

countryandhasbeenrevivedinsomeplacesasaresultofnativetitle.

Managementapproaches

Likeallplantcommunities,wetlandvegetationisshapedbythecompositionoftheregional

speciespool,localdispersal,environmentalconditionsandinteractionswithotherbiota(Fig.

1,CatfordandJansson2014).Alterationtoanyoneofthesefourelementsthroughe.g.

exoticspeciesintroduction,reducedconnectivityamongwetlandsandflowregulationcan

alterwetlandvegetation.Effectivemanagementrequiresacomprehensiveunderstandingof

23

thefactorsandprocessesthatinfluencewetlandvegetationsothatthechiefthreatsto

wetlandvegetationcanbeidentifiedandtargeted(Fig.1).

ThreatstowetlandvegetationalongtheRiverMurrayincludecattlegrazing,eutrophication,

drought,humanactivitiesaroundtownsandfarms,andflowregulation.Ofthese,flow

regulationwasfoundtobeprimarilyresponsibleforanobserveddeclineinnative

vegetation,andparticularlynativeamphibiousvegetation(Catfordetal.2014).Byaltering

historicalwaterregimes,andreducingfloodmagnitudeinparticular,flowregulationinhibits

nativeplantsthatarepoorlyadaptedtothemodifiedfloodingregimes.Withless

competitionfromnativeplants,exoticplantspecies(mostofwhichareterrestrial)have

increasedinabundance.Environmentalflowscanreducesomeofthesenegativeeffects,but

itisrarelypossibletoprovidethefullspectrumofneedsforwetlandplants,andalsoservice

otherwetlandneeds.Forexample,environmentalflowsarecommonlyusedtoextendthe

durationofnaturalfloodeventsbecauseflooddurationiscrucialforfishspawningand

waterbirdbreeding,butextendeddurationintosummermonthsfavourscompetitive

emergentmacrophytessuchasTyphaorJuncusingensandcanleadtoperverseoutcomes

(Box1).

Onceathreatisidentified,variedapproachescanbeusedtoameliorateit.Forexample,for

systemswithaninsufficientsupplyofpropagules,seedscanbesowndirectlyorhydrological

connectivitycanbere-establishedamongwetlandstofacilitatedispersal.Whenvarious

managementoptionsareavailableandthemosteffectiveoneunknown,modellingcanaid

decision-makingbypredictingthelikelyresponseofvegetationcommunitiestodifferent

managementactions.Basedonecologicalunderstandingandempiricaldata,astateand

transitionmodelhasbeendevelopedfortheRamsar-listedMacquarieMarshestomodel

effectsoffloodfrequency,distancetoriverandfirefrequencyonvegetationdynamics(Bino

etal.2015).

Modellingisavaluabletoolforanticipatingecologicalresponsestomanagementactions,

butcanalsobeusedtoanticipateeffectsofenvironmentalconditionsnotpreviously

experienced(Catfordetal.2013).Novelecosystemsthatarisefromglobalenvironmental

changeandexoticspeciesinvasionspresentnewchallengesforenvironmentalpolicyand

management.Incaseswheremaintenanceorrestorationofhistoricalvegetationis

unrealistic,wetlandmanagersmayinsteadfocusonthemaintenanceofkeyecosystem

servicesorfunctions(e.g.waterfiltering,carbonsequestration,floodattenuation).This

couldinvolvefacilitatingtheestablishmentofsalt-tolerantspeciesforwetlandsaffectedby

secondary(human-induced)salinization(Simetal.2006).

24

Conclusion

Wetlandsandwetlandvegetationareofcriticalecological,social,culturalandeconomic

value,exemplifiedbytheirlikelyroleasrefugiaandsteppingstonesfordispersalina

changingclimate(Caponetal.2013).OverhalfofAustralia’swetlandshavebeenlostinthe

last200years(Bennett1997).Thoseremainingareseverelydegradedyettheyarefacing

increasingthreatfromrisingwaterdemand,landusechange,mining,climatechange,

agriculturaldevelopmentinnewregions,risingsealevelsandassociatedsaltwaterintrusion,

andtheintroductionandspreadofinvasivespecies.Expansionofirrigatedagriculturein

northernAustraliawouldincreasepressureonfreshwaterecosystemsinthenorth(Douglas

etal.2011)andcontinuedextractionofgroundwaterwillexacerbatewetlanddegradationin

centralandwesternAustralia.Wetlandvegetationisresilientbyitsverynaturewithplant

physiologicalandlifehistoryadaptationstocopewithahighlyvariableenvironment.

However,theycanonlywithstandsomuch.Toincreaseprotectionofwetlandecosystems,

greaterinclusioninthenationalreservesystemisrequiredandincreasedpolicyinitiatives

thatprotectthemandthewateronwhichtheyrely.Thelossanddegradationofwetland

ecosystemsthroughouttheGreatArtesianandMurray-DarlingBasinsprovidesobering

lessonsforotherpartsofthecountry.

Acknowledgments

WethankDavidKeithforinvitingustowritethischapter,PatrickDriverfortheideaand

informationforBox1,andMargaretBrockandGregKeigheryforfeedbackonthechapter

plan,andMargaretBrockandananonymousreviewerforcommentsonachapterdraft.JAC

andSWacknowledgefinancialsupportfromtheARCCentreofExcellenceforEnvironmental

Decisions.

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Displayitems

Table1Hierarchicalclassificationschemeusedtocategorisewetlandspeciesbasedontheirresponsetowaterregime.ClassificationwasdevisedbyBrockandCasanova(1997)basedonfieldandgerminationtrials.

Box1Perverseoutcomesofenvironmentalwaterydelivery.

Figure1Keyabiotic,bioticandhumanfactorsthatshapethebiogeographyandecologyofwetlandvegetationinAustralia.Arrowsindicatemajorcausalrelationships(e.g.climateaffectshydrology;lithologyaffectgeomorphology;hydrology,geomorphologyandhydraulicscollectivelyaffectwaterqualityandhydrologicalconnectivity).Feedbacks(notshowntoavoidclutter)occuramongandwithintheabioticandbioticdrivers,betweenvegetationandabioticdrivers(e.g.vegetationcanmodifyhydraulics,waterquality,microclimates)andbetweenexternalfactors(e.g.bushfires,landusepractices)andtheabioticandbioticcomponentsofwetlands.Humansaffectwetlandvegetationdirectlyandindirectlybyalteringenvironmentalconditions,dispersalopportunitiesandbioticinteractions.

Figure2RangeofcommonAustralianwetlandplantspecieshighlightingthediversityofwetlandplantgrowthforms:a)Ludwigiapeploidessubsp.montevidensisandMyriophyllumspecies;b)outer,darkerbandofEleocharisacutaandinnerbandofPseudoraphisspinescensillustratecharacteristiczonesofwetlandvegetation;c)Typhaorientalis;d)exoticNymphaeamexicana,JerrabomberraWetlands,ACT;e)floatingAzollapinnatawithsubmergedexoticEgeriadensa,EustonLakes,NSW;f)emergentformofexoticSagittariaplatyphyllawithaninsetshowingitssubmergedform,whichisjuststartingtoboltintotheemergentform.Photocredits:JaneCatford(a,b,c,f:alltakeninRiverMurraywetlandsinVictoriaandNSW);JaneRoberts(d,e).

Figure3a)NumberofpublicationsinISIWebofScienceonwetlandvegetationgloballyandforthetencountrieswiththegreatestnumberofpublications[greybarsaretotalpublications–notethedisjointedy-axis;blackbarsarepublicationswithappliedangle;%indicatespercentageoftotalstudiesthathaveanappliedangle];yearoffirstpublicationpercountry,followedbyyearoffirstappliedpublicationinparentheses:global1900(1968),USA1900(1981),Canada1928(1983),China1991(1995),Germany1980(1991),England1973(1975),Australia1974(1990),Spain1985(1992),France1972(1990),Netherlands1973(1984),Sweden1972(1992);b)NumberofpublicationsoverfiveyearperiodsfocusingonwetlandvegetationinAustralia[greylineindicatestotalpublications(<16perfiveyearintervaluntil1991-1995period);blacklineindicatespublicationwithappliedangle(0before1990);numberof2015publicationsassumedtobethesameas2014].SearchtermsonWebofScience(15October2015):[TOPIC:((Wetland*ORBog*ORMarsh*ORSwamp*ORFen*ORMire*ORRiparian*ORLake*ORLittoral*ORSpring*)AND(VegetationORFloraORFloristic*ORPlant*ORMacrophyt*ORHydrophyt*));RESEARCHAREAS:(ENVIRONMENTALSCIENCESECOLOGYORPLANTSCIENCESORMARINEFRESHWATERBIOLOGYORWATERRESOURCESORPHYSICALGEOGRAPHYORBIODIVERSITYCONSERVATION);Timespan:Allyears.;Searchlanguage=Auto]plus[TOPIC:((manag*ORrestor*ORrehabilitat*ORappliedORpolicyORpolicies))]plus[Country:Australia].

31

Figure4:Examplesofwetlandecosystemtypes:a)tropicalcoastalfloodplain,NT;b)springwetlandincentralAustralia;c)floodplainwetlandoftheRiverMurray,Victoria;d)monocultureofexoticUrochloamutica(paragrass)inKakadu,NT;e)groundwaterdependentwetlandinsouthwestWA;andf)constructedstormwatertreatmentwetlandinCanberra,ACT.Photocredits:MichaelDouglas(a,d);JaneCatford(b,d,f);RayFroend(e).