The-assessment-of-herbaceous-plant-cover-in-wetlands-as-an-indicator-of-function

EcologicalIndicators2(2002)287–293TheassessmentofherbaceousplantcoverinwetlandsasanindicatoroffunctionCharlesAndrewColeCenterforWatershedStewardship,ThePennsylvaniaStateUniversity,227EastCalderWay,UniversityPark,PA16801,USAAbstractIntheUnitedStates,wetlandsareoftencreated(ascomparedwithrestored)asmitigationfordamagedonetonaturalwetlandsbydevelopmentorotheractivities.Thereisincreasingconcernthatthesecreatedsitesdonotfunctionasdonaturalwetlands,evenafteraperiodofyears.Monitoringofthesecreatedwetlandsoftenconsistsofanassessmentofthepercentherbaceousplantcoverassomeindicatorofthefunctionalsuccessofthewetland.However,itisnotatallclearthatassessmentofherbaceouscovertranslatesintoanaccurateindicatorofwetlandfunction.InthispaperIreviewseveralfunctionscommonlyascribedtowetlandsandassessthereportedrelationshipofpercentherbaceouscovertothosefunctions(ifany).Ofsixfunctionsreviewed,onlyonehasaprobable(thoughindirect)positiverelationshipwiththepercentherbaceousplantcoveronasite.Moreusefulassessmentsofwetlandfunctionmightbemadewithotherstructuralindicators,suchasbasinmorphometry,treedensity,orbasalarea.©2002ElsevierScienceLtd.Allrightsreserved.Keywords:Function;Mitigation;Structure;Wetlands1.IntroductionIntheUnitedStates,wetlandsarefrequentlycreatedasmitigationfordamagedonetonaturalwetlands.TheNationalResearchCouncil(2001,p.13)defineswetlandcreationas“...theconversionofapersistentuplandorshallowwaterareaintoawetlandbyhumanactivity.”Wetlandrestoration,bycontrast,isdefinedas“thereturnofawetlandfromadisturbedoralteredconditionbyhumanactivitytoapreviouslyexistingcondition”(NRC,1992).Onceintheground,thepresumptionisthatcreatedwetlandsarethenassumedtobefunctionallyequiv-alenttonaturalwetlands.Assessingthatequivalencyisdifficult,atbest.IntheUnitedStateswetlandmit-igationisessentiallyalegalprocess(Section404oftheCleanWaterAct),withdetailsontheproposedE-mailaddress:cac13@psu.edu(C.A.Cole).mitigationspelledoutinapermitissuedbytheU.S.ArmyCorpsofEngineers(andsometimesbystateagenciesaswell).Mi