Wetlandsystemnetworkanalysisforenvironmentalflowal

EcologicalModelling222(2011)3785–3794ContentslistsavailableatSciVerseScienceDirectEcologicalModellingjournalhomepage:flowallocationsintheBaiyangdianBasin,ChinaZhifengYang∗,XufengMaoStateKeyLaboratoryofWaterEnvironmentSimulation,SchoolofEnvironment,BeijingNormalUniversity,Beijing100875,ChinaarticleinfoArticlehistory:Received13May2011Receivedinrevisedform19September2011Accepted21September2011Keywords:EcologicalnetworkanalysisEnvironmentalflowallocationsFunctionalconditionWetlandsystemTheBaiyangdianBasinabstractManyindividualwetlandsarehydraulicallyinterconnectedandpresentaspecificnetworkstructure,whichactasalargewetlandsystem.Understandingtheenvironmentalflowallocationsforawetlandsystem,insteadofanindividualwetland,isimportantforsystems-levelwaterresourcesmanagementandecologicalprotection.Inthepresentstudy,ecologicalnetworkanalysiswasintroducedasapowerfulmethodfordevelopinginsightsintotheintegralfunctionalconditionoftheBaiyangdianwetlandsysteminnorthernChina.Weinvestigatedhow6networkfunctionalindicatorsreacttodifferentenvironmentalflowallocationsin16sequentialseasonsoffour-stageduringtheperiodof1959–1978.Biologicalpro-ductivityintheBaiyangdianLakewasusedtoverifythevalidityofthesefunctionalindicators.Adeviationindex(D),whichincorporatesinputascendency(A0),outputascendency(Ae)andinternalascendency(Ai),wasadoptedtoevaluatethereasonabilityofenvironmentalflowallocationsforthewetlandsys-tem.Resultsshowthatthefunctionalindicatorsofthewetlandsystemdeclinedcontinuouslyduringthestudyperiod.Theaveragedeviationindexincreasedfrom0.69to1.089,indicatingtheenvironmentalflowallocationsforthewetlandsystemwereincreasinglyinadequateandunreasonableinthestudyperiod.Onthebasisoftheaboveresults,anadjustmentcoefficientwasdevelopedtodirecttheenviron-mentalflowallocationsforthewetlandsystemwithinthebasin.Thepresentstudyprovidesanexampleofhowmanagementactionsarisingoutofnetworkanalysismightleadtoabetterunderstandingofawetlandsystemfunctioningandholisticenvironmentalflowassessment.©2011ElsevierB.V.Allrightsreserved.1.IntroductionEnvironmentalflow(EF)isthewaterleftinawetland1,orreleasedintoit,forthepurposeofecosystemmaintenance(Kingetal.,2002;Dysonetal.,2003;Faithetal.,2006).Maintainingcer-tainlevelsofEFfordifferentkindsofwetlands,suchasrivers,lakesandestuaries,isanimportantfactortoconsiderwhenundertakingecologicalrestorationandwaterresourcesmanagementofbasins(Yangetal.,2009).IncreasedawarenessoftheimportanceofEFhasresultedinagrowingworldwidedemandtoconserveorrestoretheecologicalhealthandfunctioningofwetlandsforthebenefitofpeopleandbiodiversity.Someofthemostchallengingquestions,however,relatetothequantityofwaterrequiredtosustainspecificlevelsofenvironmentalbenefits.Tosolvethesequestions,manyEFassessmentmethodshavebeenproposedinrecentyearsandhave∗Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](Z.Yang).1Toeliminateconfusion,wehaveadoptedtheRamsarConventiondefinitionofwetlands,i.e.,“areasofmarsh,fen,peatland,orwater,whethernaturalorartificial,permanentortemporary,withwaterthatisstaticorflowing,fresh,brackish,orsalt,includingmarinewaters,thedepthofwhichatlowtidedoesnotexceedsixmeters”.Thisdefinitionissuitableforthediscussionasitdealswithwetlandsfromabroadpointofview.beenreviewedbyseveralworkers(e.g.,Tharme,2003;AcremanandDunbar,2004).Sincethestudyofstructureandfunctioninvariouswetlandsisoftencombinedwithvariousotherobjectives,determinationofEFhasoftenfocusedonsingleaquaticsystemswithdesiredobjectives(Yangetal.,2009).Thevastmajorityofmethodologiesavailablegloballyhavefocusedexclusivelyonriverecosystems(Tharme,2003).However,wetlandsarenotisolatedspacesbutdynamic,complexhabitats(Amezagaetal.,2002).Therearemultiplewaysofconnectionsbetweenwetlands,suchaslongitudinal,lateralorver-ticalhydrologicalprocesses(PattenandMatis,1982).Especially,thematerialandenergydiffusionthroughwetlandchannelsiscriticalforthelong-termpreservationofthediversityoffishpopu-lationsandotherorganismsinwetlands(SauraandPascual-Hortal,2007;Chenetal.,2010;Er˝osetal.,2011).Manyindividualwetlandsarehydraulicallyinterconnectedandpresentaspecificnetworkstructure,whichactasalargewetlandsystem(WS)(Maoetal.,2010).Thecurrentwetlandmanagementpracticesinsomeregionsarecharacterizedbyconceptual,thematicandspatialdivisionsgen-eratedbythesamefragmentedworldviewbehindnon-sustainablegrowth(Amezagaetal.,2000).Quiteafewresearcheshaverevealedtheimportanceofsystemintegritythatincorporatescomplex,interrelatedmultiple-componentwetlandsinachievingeffectivewaterresources0304-3800/$–seefrontmatter©2011ElsevierB.V.Allrightsreserved.doi:10.1016/j.ecolmodel.2011.09.0133786Z.Yang,X.Mao/EcologicalModelling222(2011)3785–3794Fig.1.TheBaiyangdianbasinanditsgeographicallocationinChina.managementandecologicalrestoration(e.g.,TilleyandBrown,1998;CohenandBrown,2007;Yangetal.,2005,2009).Riverbasinshavebeenacknowledgedastheappropriateunitforinte-gratedEFstudyandwaterresourcesmanagement(DasGupta,2008).ResearchesintoEFallo