Chapter 4 Quantifying Greenhouse Gas Sources and Sinks in … · 2014-10-31 · Greenhouse Gas...

Authors:

StephenM.Ogle,ColoradoStateUniversity(LeadAuthor)PatrickHunt,USDAAgriculturalResearchServiceCarlTrettin,USDAForestService

Contents:

4 QuantifyingGreenhouseGasSourcesandSinksinManagedWetlandSystems................4‐34.1 Overview...........................................................................................................................................................4‐3

4.1.1 OverviewofManagementPracticesandResultingGHGEmissions...........4‐44.1.2 SystemBoundariesandTemporalScale................................................................4‐74.1.3 SummaryofSelectedMethods/ModelsandSourcesofData........................4‐74.1.4 OrganizationofChapter/Roadmap..........................................................................4‐8

4.2 ManagementandRestorationofWetlands........................................................................................4‐84.2.1 DescriptionofWetlandManagementPractices..................................................4‐84.2.2 Land‐UseChangetoWetlands..................................................................................4‐13

4.3 EstimationMethods...................................................................................................................................4‐144.3.1 BiomassCarboninWetlands....................................................................................4‐144.3.2 SoilC,N2O,andCH4inWetlands..............................................................................4‐17

4.4 ResearchGapsforWetlandManagement.........................................................................................4‐21Chapter4References.............................................................................................................................................4‐23

SuggestedChapterCitation:Ogle,S.M.,P.Hunt,C.Trettin,2014.Chapter4:QuantifyingGreenhouseGasSourcesandSinksinManagedWetlandSystems.InQuantifyingGreenhouseGasFluxesinAgricultureandForestry:MethodsforEntity‐ScaleInventory.TechnicalBulletinNumber1939.OfficeoftheChiefEconomist,U.S.DepartmentofAgriculture,Washington,DC.606pages.July2014.Eve,M.,D.Pape,M.Flugge,R.Steele,D.Man,M.Riley‐Gilbert,andS.Biggar,Eds.

USDAisanequalopportunityproviderandemployer.

Chapter 4

Quantifying Greenhouse Gas Sources and Sinks in Managed Wetland Systems

Chapter 4: Quantifying Greenhouse Gas Sources and Sinks in Managed Wetland Systems

4-2

Acronyms,ChemicalFormulae,andUnits

C CarbonCH4 MethaneCO2 CarbondioxideCO2‐eq CarbondioxideequivalentsDNDC Denitrification‐DecompositionEPA EnvironmentalProtectionAgencyFVS ForestVegetationSimulatorGHG Greenhousegasha HectareIPCC IntergovernmentalPanelonClimateChangeN NitrogenN2O NitrousoxideNOx Mono‐nitrogenoxidesNRCS USDANaturalResourcesConservationServiceP PhosphorousSOC SoilorganiccarbonTg TeragramsUSDA U.S.DepartmentofAgricultureUSDA‐ARS U.S.DepartmentofAgriculture, AgriculturalResearchService


4-3

4 QuantifyingGreenhouseGasSourcesandSinksinManagedWetlandSystems

Thischapterprovidesmethodologiesandguidanceforreportinggreenhousegas(GHG)emissionsandsinksattheentityscaleformanagedwetlandsystems.Morespecifically,itfocusesonmethodsformanagedpalustrinewetlands.1Section4.1providesanoverviewofwetlandsystemsandresultingGHGemissions,systemboundariesandtemporalscale,asummaryoftheselectedmethods/models,sourcesofdata,andaroadmapforthechapter.Section4.2presentsthevariousmanagementpracticesthatinfluenceGHGemissionsinwetlandsystemsandland‐usechangetowetlands.Section4.3providestheestimationmethodsforbiomasscarboninwetlandsandforsoilcarbon,N2O,andCH4emissionsandsinks.Finally,Section4.4includesadiscussionofresearchgapsinwetlandmanagement.

4.1 OverviewWetlandsoccuracrossmostlandforms,existingasnaturalunmanagedandmanagedlands,restoredlandsfollowingconversionfromanotheruse(typicallyagriculture),andasconstructedsystemsforwatertreatment,suchasanaerobiclagoons.AllwetlandssequestercarbonandareasourceofGHGs.Table4‐1providesadescriptionofthesourcesofemissionsorsinksandthegasesestimatedinthemethodology.

Table4‐1:OverviewofWetlandSystemsSourcesandAssociatedGreenhouseGases

SourceMethodforGHGEstimation Description

CO2 N2O CH4

Biomasscarbon

Provisionsforestimatingabovegroundbiomassforwetlandforestsandaboveandbelowgroundbiomassandcarbonareincludedforshrubandgrasswetlandsinthischapter.Abovegroundbiomassforforestedwetlandsandshrubandgrasswetlandsincludeslivevegetation,trees,shrubs,andgrasses,standingdeadwood(deadbiomass),anddowndeadorganicmatter—litterlayer(deadbiomass).

SoilC,N2O,andCH4inwetlands

Theproductionandconsumptionofcarbon inwetland‐dominatedlandscapesareimportantforestimatingthecontributionofGHGs,includingCO2,CH4,andN2Oemittedfromthoseareastotheatmosphere.ThegenerationandemissionofGHGsfromwetland‐dominatedlandscapesarecloselyrelatedtoinherentbiogeochemicalprocesses,whichalsoregulatethecarbonbalance(RoseandCrumpton,2006).However,thoseprocessesarehighlyinfluencedbythelanduse,vegetation,soilorganisms,chemicalandphysicalsoilproperties,geomorphology,andclimate(SmemoandYavitt,2006).

1Palustrinewetlandsincludenon‐tidalandtidalwetlandsthatareprimarilycomposedoftrees,shrubs,persistentemergent,emergentmosses,orlichens,wheresalinityduetoocean‐derivedsaltsisbelow0.5‰(partsperthousand).Palustrinewetlandsalsoincludethosewetlandslackingvegetationthathavethefollowingfourcharacteristics:(1)arelessthan20acres;(2)donothaveactivewave‐formedorbedrockshorelines;(3)haveamaximumwaterdepthoflessthan6.5ft.atlowwater;and(4)haveasalinityduetoocean‐derivedsaltslessthan0.5%(StedmanandDahl,2008).


4-4

4.1.1 OverviewofManagementPracticesandResultingGHGEmissions

ThischapterprovidesmethodsforestimatingcarbonstockchangesandCH4andN2Oemissionsfromnaturallyoccurringwetlands2andrestoredwetlandsonpreviouslyconvertedwetlandsites.Constructedwetlandsforwatertreatment,includingdetentionponds,areengineeredsystemsthatarebeyondthescopeconsideredherebecausetheyhavespecificdesigncriteriaforinfluentandeffluentloads.Inaddition,themethodsarerestrictedtoestimationofemissionsonpalustrinewetlandsthatareinfluencedbyavarietyofmanagementoptionssuchaswatertablemanagement,timber,orotherplantbiomassharvest,andwetlandsthataremanagedwithfertilizerapplications.ThemethodsarebasedonestablishedprinciplesandrepresentthebestavailablescienceforestimatingchangesincarbonstocksandGHGfluxesassociatedwithwetlandmanagementactivities.However,giventhewidediversityofwetlandstypesandthevarietyofmanagementregimes,thebasisforthemethodsprovidedinthissectionarenotaswell‐developedasothersectionsinthisguidance(i.e.,CroplandandGrazingLands,AnimalProduction,andForestryMethods).Table4‐2providesasummaryofthemethodsandtheircorrespondingsectionforthesourcesofemissionsestimatedinthisreport.

Table4‐2:OverviewofWetlandSystemsSources,Method,andSection

Section Source Method

4.3.1Biomasscarbon

MethodsforestimatingforestvegetationandshrubandgrasslandvegetationbiomasscarbonstocksuseacombinationoftheForestVegetationSimulator(FVS)modelandlookuptablesfordominantshrubandgrasslandvegetationtypesfoundinChapter3,Cropland,andGrazingLand.Ifthereisaland‐usechangetoagriculturaluse,methodsforcroplandherbaceousbiomassareprovidedinChapter3.

4.3.2SoilC,N2O,andCH4inwetlands

TheDenitrification‐Decomposition (DNDC) process‐basedbiogeochemicalmodelisthemethodusedforestimatingsoilC,N2O,andCH4emissionsfromwetlands.DNDCsimulatesthesoilcarbonandnitrogenbalanceandgeneratesemissionsofsoil‐bornetracegasesbysimulatingcarbonandnitrogendynamicsinnaturalandagriculturalecosystems(Lietal.,2000;Miehleetal.,2006;Stangetal.,2000)andforestedwetlands(Daietal.,2011;Zhangetal.,2002),usingplantgrowthestimatedasdescribedinSection4.3.1.

4.1.1.1 DescriptionofSector

TheNationalWetlandsInventorybroadlyclassifieswetlandsintofivemajorsystems:(1)marine,(2)estuarine,(3)riverine,(4)lacustrine,and(5)palustrine(Cowardinetal.,1979).Fourofthosesystems(marine,estuarine,riverine,andlacustrine)areopen‐waterbodiesandnotconsideredwithinthemethodsdescribedinthisguidance.Palustrinewetlandsencompassthewetlandtypesoccurringonthelandandarefurtherclassifiedbymajorvegetativelifeformandwetnessorfloodingregime.CommonpalustrinewetlandsareillustratedinFigure4‐1.Forexample,forestedwetlandsareoftenclassifiedaspalustrine—forested.Similarly,mostgrasswetlandsareclassifiedaspalustrine—emergent,reflectingemergentvegetation(e.g.,grassesandsedges).Wetlandsalsovarygreatlywithrespecttogroundwaterandsurfacewaterinteractionsthatdirectlyinfluence

2WetlandsaredefinedinChapter7,LandUseChange.Wetlandsthatareconvertedtoanon‐wetlandstatusshouldbeconsideredintheappropriatechapter(e.g.,CroplandandGrazingLands,AnimalProduction,andForestryMethods).


4-5

hydroperiod(i.e.,thelengthoftimeandportionoftheyearthewetlandholdswater),waterchemistry,andsoils(Cowardinetal.,1979;Winteretal.,1998).AllthesefactorsalongwithclimateandlandusedriversinfluencetheoverallcarbonbalanceandGHGfluxes.

Figure4‐1:PalustrineWetlandClassesBasedonVegetationandFloodingRegime

Source:Cowardinetal.(1979).

GrasslandandforestedwetlandsaresubjecttoawiderangeoflanduseandmanagementpracticesthatinfluencethecarbonbalanceandGHGflux(Faulkneretal.,2011;Gleasonetal.,2011).Forexample,forestedwetlandsmaybesubjecttosilviculturalprescriptionswithvaryingintensitiesofmanagementthroughthestandrotation;hence,thecarbonbalanceandGHGemissionsshouldbeevaluatedonarotationbasis,whichcouldrangefrom20tomorethan50years.Incontrast,grasswetlandsmaybegrazed,hayed,ordirectlycultivatedtoproduceaharvestablecommodityannually.WhileeachmanagementpracticemayinfluencecarbonsequestrationandGHGfluxes,theeffectisdependentonvegetation,soil,hydrology,climatologicalconditions,andthemanagementprescriptions.Thissectionfocusesonrestorationandmanagementpracticesassociatedwithpalustrinewetlandsthataretypicallyforestedorgrassland.

4.1.1.2 ResultingGHGEmissions

GHGemissionsfromwetlandsarelargelycontrolledbywatertabledepthanddurationaswellasclimateandnutrientavailability.Underaerobicsoilconditions,whicharecommoninmostuplandecosystems,organicmatterdecompositionreleasesCO2,andatmosphericCH4canbeoxidizedinthesurfacesoillayer(Trettinetal.,2006).Incontrast,theanaerobicsoilsthatcharacterizewetlandscanproduceCH4(dependingonthewatertableposition)inadditiontoemittingCO2.Accordingly,wetlandsareaninherentsourceofCH4,withgloballyestimatedemissionsof55to150teragrams(Tg)ofCH4peryear(Blainetal.,2006).

Toaccommodateentity‐scalereportingintheUnitedStatesforagriculturalandforestryoperations,Tier2and3methodsaddresspalustrinewetlandscontainingbothorganicandmineralhydricsoils.Thesewetlandsmaybeinfluencedbyagriculturalandforestrymanagement,andmethodsarecurrentlyavailableforbothtypesofmanagement.Thischapterprovidesmethodologiesforthefollowingwetlandsourcecategories:


4-6

1. Biomasscarboninforested,shrub,andgrasswetlands;2. Soilcarbonsinksinwetlands;and3. N2OandCH4emissionsinwetlands.

Biomasscarboncanchangesignificantlywithmanagementofwetlands,particularlyinforestedwetlands,changesfromforesttowetlandsdominatedbygrassesandshrubs,oropenwater.Inforestedwetlands,therecanalsobesignificantcarbonindeadwood,coarsewoodydebris,andfinelitter.Harvestingpracticeswillalsoinfluencethecarbonstocksinwetlandstotheextentthewoodiscollectedforproducts,fuel,orotherpurposes.

WetlandsarealsoasourceofsoilN2Oemissions,primarilybecauseofnitrogenrunofffromadjoininguplandsandleachingintogroundwaterfromagriculturalfieldsand/oranimalproductionfacilities.N2OemissionsfromwetlandsduetonitrogeninputsfromsurroundingfieldsoranimalproductionareconsideredindirectemissionsofN2O(deKleinetal.,2006).MethodologiesforestimatingindirectN2Oareprovidedintherespectivesourcechapter(i.e.,Chapter3,CroplandandGrazingLands,orChapter5,AnimalProduction).However,directN2Oemissionsoccurinwetlandsifmanagementpracticesincludenitrogenfertilization,hence,guidanceisprovidedforthissourceofemissions.

4.1.1.3 RiskofReversals

Wetlandsinherentlyaccumulatecarboninthesoilsduetoanaerobicconditions,andtheyarenaturalsourcesofCO2andCH4totheatmosphere.Managementmayalterconditionsthataffectboththepoolsandfluxes.Forexample,accumulatedsoilcarboncanbereturnedtotheatmosphereifthewetlandisdrained(ArmentanoandMenges,1986).Incontrast,silviculturalwatermanagementinwetlandscanleadtohigherbiomassproduction,whichmaypartiallyoffsetincreasedsoilorganicmatteroxidation.Conversely,thesoilcarbonpoolinconvertedwetlandsistypicallylowerthantheunmanagedsoil,andrestoringwetlandconditionsmayincreasecarbonstorageovertimeifinherenthydricsoilconditionsaremaintainedwithconsistentorganicmatterinputs.

Reversalsofemissiontrendscanoccurifamanagerrevertstoapriorconditionoranearlierpractice.Forexample,anentitymaydecidetoreturnawetlandthathadbeendrainedandcroppedbacktoaforestedwetlandcondition.Anothercommonexamplewouldbeifarestoredforestedwetlandisrevertedbacktoagriculture.ThesereversalsdonotnegatethemitigationofCH4orN2Oemissionstotheatmospherethathadoccurredpreviously,totheextentthatwetlandrestorationorchangeinmanagementcanreduceorchangetheseemissions.Correspondingly,thestartingpointfromthereversionwilldeterminetheeffectoncarbonsequestrationandGHGflux.Forexample,inarestoredforestedwetland,reversionofthesitetocropproductionwouldreturncarbonsequesteredduringtherestorationperiodtotheatmosphereovertime.

Thereisatrade‐offinCH4andN2Oemissionswithmanagementofthewatertableposition.WetlandswithanaerobicsoilconditionsthatarepersistentnearthesurfaceforalongerperiodduringtheyearwilltendtohavehigherCH4emissionsandloweremissionsofN2O.N2Oemissionsaregreatlyreducedifsoilsaresaturatedbecausethereislittleinherentnitrification,anddenitrificationwillleadtoN2production(Davidsonetal.,2000).Forexample,restorationofwetlandswillnormallyleadtoahigherwatertableforalongerperiodoftheyear,andthuscontributetohigheremissionsofCH4butloweremissionsofN2O.Thesetrendscanbereversedifthewatertableisloweredthroughmanagementordrought,whichwilltendtoenhanceN2Oemissionsifthereisasourceofnitrate,whilereducingemissionsofCH4.Figure4‐2providesanillustrationofthecarboncycletypicallyfoundinwetlandforestandgrasslandwetlandsandrepresentsthescopeofthemethodspresentedinthisguidance.


4-7

Figure4‐2:CarbonCycleforForestandGrasslandWetlands

Source:TrettinandJurgensen(2003).

4.1.2 SystemBoundariesandTemporalScale

Systemboundariesaredefinedbythecoverage,extent,andresolutionoftheestimationmethods.ThelocationofthewetlandsmaybeapproximatedbyuseoftheNationalWetlandsInventory,3thelocationofhydricsoilsasconveyedbytheNRCSsoilsmap,orthroughdirectdelineationofwetlands.Thecoverageofthemethodscanbeusedtoestimateavarietyofemissionsources,includingemissionsassociatedwithbiomassC,litterC,andsoilscarbonstockchangesandCO2,CH4,andN2Ofluxesfromsoils.Systemboundariesarealsodefinedbytheextentandresolutionoftheestimationmethod.Themethodsprovidedforwetlandshaveaspatialextentthatwouldincludeallwetlandsintheentity’soperation,withestimationoccurringattheresolutionofanindividualwetland.EmissionsareestimatedonanannualbasisforasmanyyearsasneededforGHGemissionsreporting.

4.1.3 SummaryofSelectedMethods/ModelsandSourcesofData

TheIPCC(2006)hasdevelopedasystemofmethodologicaltiersforestimatingGHGemissions.Tier1representsthesimplestmethodsusingdefaultequationsandfactorsprovidedintheIPCCguidance.Tier2usesdefaultmethodsbutemissionfactorsthatarespecifictodifferentregions.Tier3utilizesaregion‐specificestimationmethod,suchasaprocess‐basedmodel.Highertiermethodsareexpectedtoreduceuncertaintiesintheemissionestimatesifthereissufficientinformationandtestingtodevelopthesemethods.Inthisguidance,biomass,litter,andsoilcarbonstockchanges,inadditiontosoilN2OandCH4emissions,areestimatedusingTier2and3methods.

Thedatarequiredtoapplythesemethodsrangefrombasicinformationonsoils,vegetation,weather,landuse,andmanagementhistorytodataonfertilizationratesordrainageconditions.Whilesomeofthesedataareoperation‐specificandmustbeprovidedbytheentity,otherdatacanbeobtainedfromnationaldatabases,suchasweatherdataandsoilcharacteristics.

3SeeNationalWetlandsInventoryhttp://www.fws.gov/wetlands/.


4-8

4.1.4 OrganizationofChapter/Roadmap

Thewetlandssectionofthisreportisorganizedintothreeprimarysections.Section4.2providesadescriptionofwetlandmanagementeffectsonGHGemissions,elaboratingonthescientificbasisforhowvariouspracticesinfluenceGHGemissions.Section4.3providesarationalefortheselectedmethod,adescriptionofthemethod,includingageneraldescription(withequationsandfactors),activitydatarequirements,ancillarydatarequirements,limitationsofthemethod,anduncertaintiesassociatedwiththeestimation.Asinglemethodisprovidedforeachsourcepresentedinthischapter(i.e.,biomasscarboninforested,shrub,andgrasswetlands;soilcarbonandCH4inwetlands;anddirectN2Oemissionsinwetlands).Asinglemethodwasselectedtoensureconsistencyinemissionestimationbyallreportingentities,andtheselectedmethodisconsideredthebestoptionamongpossibilitiesforentity‐scalereporting.Methodsmayberefinedinthefutureastheyarefurtherdeveloped.Thelastsectionprovidesasummaryofselectedresearchgaps.

4.2 ManagementandRestorationofWetlandsHowwetlandsaremanagedcanhaveasignificanteffectonGHGemissionsandsinks,whichareprimarilyinfluencedbythedegreeofwatersaturation,climate,andnutrientavailability.Inamajorityofwetlands,90percentofcarboningrossprimaryproductionisreturnedtotheatmospherethroughdecay,andtheremaining10percentaccumulatesinthebottomofthewaterbodyaccumulatingonpreviouslydepositedmaterials(Blainetal.,2006).ManagementofthewatertablewithinawetlandwillresultinbothlowerCH4emissionsduetodecreasedproductionandoxidationofCH4producedinthesubsoilandanincreaseinCO2emissionsduetoincreasedoxidationofsoilorganicmatter.N2Oemissionsfromwetlandsaretypicallylow,unlessananthropogenicsourceofnitrogenentersthewetland.Indrainedwetlands,N2Oemissionsarelargelycontrolledbythefertilityofthesoilandwatermanagementregime.Incontrast,restoredandconstructedwetlandsgeneratehigherlevelsofCH4andlowerlevelsofCO2becauseofthechangeinawatertabledepth(Blainetal.,2006).

4.2.1 DescriptionofWetlandManagementPractices

ThissectionprovidesadescriptionofmanagementpracticesinwetlandsthatinfluenceGHGemissions(CH4orN2O)orcarbonstocks.Individualsectionsdealwithforestedandgrasswetlandsthatcouldoccurinagriculturalandforestryoperations.Itisimportanttonotethatdrainageofwetlandsforcommodityproduction,suchasannualcrops,orforotherpurposesarenotconsideredwetlandsintheseguidelines.MethodsfordrainedwetlandscanbefoundinChapter3,CroplandsandGrazingLands,orChapter6,ForestLands,dependingonthelanduseafterdrainageofthewetland.

4.2.1.1 SilviculturalWaterTableManagement

Silviculturalwatermanagementsystemsareprincipallyusedtoregulatethewatertabledepthinordertoreducesoildisturbanceassociatedwithharvestingoperationsandalleviatestressfromsaturatedsoilconditionsonartificiallyregeneratedplantations.Thesilviculturalwatermanagementsystemshouldnoteliminatethewetlandconditionsofthesite.

SilviculturalwatermanagementsystemsaffectthecarbonbalanceandGHGemissionsfromthesite(Bridghametal.,2006).Typicallyorganicmatterdecompositionisenhancedwiththeimpositionofadrainagesystem,CH4emissionsarereduced,andN2Oemissionsmayincrease(Lietal.,2004).Carbonsequestrationinbiomassmaybeenhancedonsiteswithsilviculturaldrainagesystemsduetoincreasedtreeproductivity(MinkkinenandLaine,1998).


4-9

4.2.1.2 ForestHarvestingSystems

Therearetwogeneraltypesofsystemsusedtoharvesttreesfromforestedwetlands:partialcuttingandclearcutting.Apartialcutinvolvestheremovalofselectedtreesfromthestand.Thenumberoftreesremovedortheresidualdensityofthestandwilldependonthestandtype,species,intendedproduct(s),andstandage.Theamountoftreebiomassremovedduringthepartialcutmayalsovary;topsmaybeleftonsiteifonlylogsareremoved,ortheymaybeconcentratedinalandingifwhole‐treeharvestingisused.Withthelattersystem,thetopsmayalsobeutilizedandremovedfromthesite.Partialcuttingistypicallyusedinriparianzonesandsitesthataremanagedforsolidwoodproducts.Clearcuttingresultsintheremovalofalloverstorytreesfromthesite.ClearcuttingistypicallyusedonnaturalstandsoccurringinfloodplainsofthesoutheasterncoastalplainandlacustrineandoutwashplainsoftheupperMidwest.Clearcuttingisalsothetypicalsystememployedtoharvestconiferandhardwoodplantations.

Partialcuttingaffectsthecarbonbalanceofthesitebydirectremovalofbiomass;increasedbiomassontheforestfloor,whichisthensubjecttodecayprocesses;andincreasedgrowthoftheremainingtreesforseveralyears.Decompositionofdeadbiomasswithinthestandmaybeacceleratedtemporarilyduetothechangesinambientconditionsandtheaddedresiduefromtheharvest.

Clearcuttingaffectscarbonstocksofthesitebydirectlyremovingthebiomass;increasingamountsofbiomassaddedtotheforestfloor;alteringthecarbonsequestrationforseveralyears,dependingonthetypeofregeneration;andalteringtherateoforganicmatterdecompositionintheforestfloorandsoil(Lockabyetal.,1999).Clearcuttingaffectstheambientconditionsofthesitebecauseoftheremovaloftheoverstoryvegetation.Italsoaltersthewaterbalanceofthewetlandduetothereductioninevapotranspirationfollowingharvesting.Typically,asaresultoflowerevapotranspiration,thewatertablerises,andthesitewillexhibitlongerperiodsofsaturation.ThischangeinthewatertablepositionhasdirecteffectsontheproductionofCH4andN2Oandsubsequentfluxestotheatmosphere(Lietal.,2004).

4.2.1.3 ForestRegenerationSystems

Therearetwobasicforestregenerationsystems,characterizedas(a)naturalregeneration,and(b)artificialregeneration.Naturalregeneration,asthenameimplies,reliesuponregenerationofthetreesfromseedorsproutsthatareleftbyharvestedtrees.Naturalregenerationisusedinbothpartial‐cutandclear‐cutharvestsystems.Naturalregenerationwillleadtoeven‐agedstandsofshade‐intolerantorearlysuccessionalcommunities,typicallyinfloodplainsinthesoutheasternUnitedStatesandtheconiferousplainsoftheupperMidwest.

Artificialregenerationresultsfromplantingseedlingsonapreparedsite.Thesitepreparationpracticesmayinvolveremovaloftheharvestresiduebiomass,mechanicalscarificationand/ortheapplicationofherbicidetotemporarilyreduceweedcompetitionwithseedlings,andthecreationofplantingbeds.

TheeffectoftheforestregenerationsystemoncarbonstocksandtraceGHGemissionsdependsonthetypeofharvestingsystemthatwasused(Lockabyetal.,1999;Trettinetal.,1995).Thecombinationofpartialcuttingandnaturalregenerationhaslittleadditiveeffectbecausetheextentofregenerationistypicallyquitelowfollowingapartialcutthatremoveslessthanhalfofthebasalarea.Carbonstocksfollowingclear‐cutharvestingwithnaturalregenerationisaffectedbytherateofgrowthoftheregeneration,changesinambientconditions,andchangesinthesoilwaterregime.Thosefactorsalsoaffectartificialregenerationsystems;additionally,thetypeandextentofsitepreparationalsoaffectsthecarbonstocks.


4-10

4.2.1.4 Fertilization

Fertilizationisusedprimarilyinforestedwetlands,suchastreeplantations,toenhancegrowth(Albaughetal.,2004).Grasswetlandsalsoreceivefertilizerasaresultofadjacentagriculturalactivities,andwhendryconditionspermit,aredirectlytilled,planted,andfertilized.Nitrogenisthemostcommonlyappliedfertilizer,andincreasednitrogeninputsareknowntoincreaseemissionsofN2O(Bedard‐Haughnetal.,2006;Davidsonetal.,2000;Gleasonetal.,2009;Merbachetal.,2002;PhillipsandBeeri,2008;ThorntonandValente,1996).NitrogenfertilizerswillalsoenhanceN2Oemissionsbothdirectlyonthesiteandindirectlyifnitrogenislostfromthesiteasnitrateingroundwaterorrunoff,aswellasvolatilizationofnitrogenasammoniaorNOx.TheindirectlosseswillcontributetoN2Oemissionsatothersites.

Theeffectoffertilizationoncarbonstocksisprincipallyrealizedthroughchangesintreegrowthrates.Theeffectwouldresultfromnitrogenfertilizers,butphosphorusmayalsobeappliedinthesoutheasternUnitedStates.

4.2.1.5 ConversiontoOpen‐WaterWetland

Theconversionofwetlandtoopenwateroccursprimarilyasaresultofbeaverimpoundmentsandtoalesserdegreeimproperlyinstalledroadsorotherartificialembankmentsthroughawetlandthatimpedesnaturaldrainage.Theconversiontoopenwatersignificantlyreducescarbonsequestrationthroughplantgrowth,becauseuptakeislimitedtosubmergedaquaticvegetation.ThehigherwatertableforalongerperiodoftheyearwillalsotendtoincreaseCH4flux.

4.2.1.6 ForestTypeChange

Changingamanagedforesttoacharacteristicnativeconditionisalsoconsideredaformofrestoration.TheeffectoftherestorationactivitiesonthecarbonstocksandCH4emissionsdependsontheextentofthehydrologicmodificationsthatwereemployedintheprevioussilviculturalsystem.Thetwomostcommonsituationsareasitethathasbeenmanagedforaparticularspeciesorproductwithouthydrologicmodification;theothercommonsituationiswherethesitehasbeenmanagedforplantationforestryandthehydrologyandvegetationhavebeenextensivelymodified.

4.2.1.7 WaterQualityManagement

Riparianzonesalongstreams,rivers,andlakesmaybemanagedtoprotectwaterqualitybymitigatingnonpointsourcepollution(Balestrinietal.,2011;Chaubeyetal.,2010).4Pollutantsareremovedbyphysicalfiltration,chemicaladsorption,plantuptake,andmicrobialtransformations(Abu‐Zreigetal.,2003;Borinetal.,2005).5However,riparianbuffersarelimitedintheiradsorptioncapacitiesforsomeconstituents,whichmaythenflowintowaterways.Thebufferzonesizeandconfigurationvariesaccordingtorunoffpatternsofthesite,phosphorus/nitrogeninputs,hydrologicconnectivity,organiccarbon,mineralcontent,andoxidative/reductivestate(Abu‐Zreigetal.,2003;Hoffmannetal.,2009;Novaketal.,2002;YoungandBriggs,2008).

Riparianbufferzonesarecomprisedofnativeandnon‐nativevegetationormayalsocontaincultivatedplantsinsomecases.Managementactivitiesofthenativevegetationbufferzonesaretypicallyconstrainedorlimitedtosmallremovals.Inthecaseofforestriparianbuffers,aselective‐4Additionalreferencesinclude(Choetal.,2010;Fliteetal.,2001;Hoffmannetal.,2009;Huntetal.,2004;Leeetal.,2004;Lowranceetal.,2007;Montreuiletal.,2010;PeterjohnandCorrell,1984;RanalliandMacalady,2010;Schoonoveretal.,2005;Tabacchietal.,1998;YoungandBriggs,2008).5Additionalreferencesinclude(Dillahaetal.,1989;Dillahaetal.,1988;Hoffmannetal.,2009;Jordanetal.,2003;Kellyetal.,2007;Novaketal.,2002;Vellidisetal.,2003;YoungandBriggs,2008).


4-11

harvestregimewouldbeusedthatinfluencesbothcarbonstocksandGHGemissions.Inmixedbuffers(i.e.,grassstripsfollowedbyforest),themanagementofthecultivatedbufferwouldlargelydeterminetheeffectofthepractice,whichwillbeanalogoustohaycultivation.Riparianzonesmaycontainamosaicofhydric(wetland)andnon‐hydricsoils;accordingly,thedistributionofsoiltypesisimportantforassessingtheeffectofthemanagementactivity.

Whereasriparianbuffersoccupylowlandscapepositionsandaretypicallywet,theyareoftenveryeffectiveinremovingnitrogenviadenitrification(Ambus,1991;Davisetal.,2008;Dodlaetal.,2008;Hilletal.,2000;Huntetal.,2007;Jordanetal.,1998;Roobroecketal.,2010;Smithetal.,2006;Stoneetal.,1998;Woodwardetal.,2009),whichleadstoindirectN2Oemissions(Jetten,2008).Denitrificationinriparianbuffersisoftenspatiallyunevenbecauseriparianbuffersvaryconsiderablyintheirsizeandlandscapepositionsaswellastheirsoil,vegetative,andhydrologicalconditions(Bowdenetal.,1992;BrulandandMacKenzie,2010;Fliteetal.,2001;Hilletal.,2000).StudieshavesuggestedthatN2Oemissionsinriparianzoneswerenotasignificant“pollution‐swappingphenomenon”(Dhondtetal.,2004;Kimetal.,2009a;Kimetal.,2009b).Significantemissionsarelikelytobelimitedtospatialandtemporalhotspots(Groffmanetal.,2000;Huntetal.,2007;Kimetal.,2009b).Moreover,someriparianwetlandsystemscanserveassinksfornitrogen(Roobroecketal.,2010).WhilemanyfactorsaffectthemicrobialproductionofN2O,oneofthemostdominatingfactorsisthecarbontonitrogenratio;largerratiosgenerallyhavelowN2Oemissionsbecausenitrogenisimmobilizedinthesoilorganicmatter(Huntetal.,2007;Klemedtssonetal.,2005).However,itisimportanttonotethatindirectN2Oemissionsareattributedtothesourceofthenitrogen,whichcanbeaneighboringfieldorlivestockfacility;sothemethodstoestimateindirectN2Oemissionsareprovidedinothersectionsofthisreport(i.e.,Chapter3,CroplandandGrazingLands,orChapter5,AnimalProduction).

RiparianbufferscanserveasbothsourcesandsinksofCH4(Hopfenspergeretal.,2009;Soosaaretal.,2011).TheirhydrologyandbiogeochemicalcharacteristicsexhibitsignificantinfluenceonthenetCH4emission.Thesecharacteristicsincludewatertableposition,temperature,oxidative/reductivepotential,andplantcommunitycompositions(Pennocketal.,2010;Whalen,2005).Moreover,N2Oemissionsfromdenitrificationcanbesignificantlyinfluencedbymethanotrophs(Costaetal.,2000;Knowles,2005;Modinetal.,2007;Osakaetal.,2008).

Similarbuffersexistforgrasswetlands,eitheraspartofaconservationprogramorasanaturallyoccurringareaaroundawetlandwheremoist‐soilconditionspreventtillage.Grassbuffersreducerunoffandinterceptsedimentsthatwouldaffectwaterqualitybyincreasingturbidityandinputsoffertilizersandagrichemicals.Moreover,plantingtheentirecatchmentwithgrasscanreduceCH4emissionsbydecreasingtheartificiallyhighwaterlevelsandextendedhydroperiodsthatoftenareassociatedwithcroplandsites(EulissJrandMushet,1996;Gleasonetal.,2009;vanderKampetal.,2003).

4.2.1.8 WetlandManagementforWaterfowl

Wetlandsmaybemanagedforwaterfowlhabitat.ActivitiesthatarespecifictowetlandwaterfowlmanagementhavedirectinfluencesoncarbonstocksandGHGemissions,includingregulationofthewaterregime,specificallydepthanddurationofinundation,aswellasplantingandcultivationofcropsforfoodandhabitat.Waterregimesimposedforwaterfowlmanagementmaybedifferentthanthenaturalwatertablecycleofthesite.Accordingly,changingthewatertablealterstheperiodsofsoilaerationandsaturationinfluencingratesofCH4andN2O,aswellascarbonstockchangesintimberstandsandotherwetlandvegetation.CultivatingcropsinwetlandsmanagedforwaterfowlwillalsoinfluencecarbonstocksandN2Oemissionsbasedonselectionofcropsand/orrotationpractice,tillage,liming,andnutrientmanagement.


4-12

4.2.1.9 ConstructedWetlandsforWastewaterTreatment,SedimentCapture,andDrainageWaterAbatement

Constructedwetlandsareengineeredsystemsforwastewatertreatment,captureofsediments,anddrainagewaterabatementinagriculturalandforestryoperations(Chenetal.,2011;Elgoodetal.,2010).Surface‐flowandsubsurfaceflowsystemsarethetwoprincipaltypesofconstructedwetlands(KadlecandKnight,1996).Theprincipaldifferencebetweenthesetwotypesofconstructedwetlandsisthewaterflowpath.Inthecaseofthesubsurfaceflowwetlands,allthewaterflowsarebeneaththesoilsurface;thesurface‐flowsystemshaveflowbothaboveandwithinthesoil.

Thesubsurfacewetlandstypicallyconsistofwetlandplantsgrowinginabedofhighlyporousmediasuchasgravelorwoodchipsthathaveawatertablefromonetotwometersabovethesoilsurfacewitharectangularshape.ThereislackofagreementabouttherelativeimpactofmicrobialandplantprocessesinthefunctionofsubsurfacewetlandsincludingGHGemissions.However,plantsandmicrobesaretypicallyinterdependentlyinvolvedintheprocessesthatcontributetoemissions(Faubertetal.,2010;Luetal.,2010;Piceketal.,2007;TannerandHeadley,2011;Wangetal.,2008;Zhuetal.,2007).WhilethemicrobialcommunitydrivesthebiogeochemicalprocessesthatspecificallyemitGHGs(Dodlaetal.,2008;Faulwetteretal.,2009;Huntetal.,2003;Tanneretal.,1997;Zhuetal.,2010),theplantcommunitymodifiestheenvironmentalconditionscontributingtoemissionrates,includingtransportingoxygenintothedepthofthewetlands,providingrootsurfacesforrhizospherereactions,andventinggasestotheatmosphere.Theplantprocessesaresignificantlyimpactedbyplantcommunitycompositionandweatherconditions(Steinetal.,2006;SteinandHook,2005;Tayloretal.,2010;Towleretal.,2004;Wangetal.,2008;Zhuetal.,2007).

SurfaceflowwetlandshaveamuchmoredirectexchangeofoxygenandGHGswiththeatmosphere.Theycanbevariableinshapeandaregenerallylessthan0.5metersindepth.Surfacewetlandsminimizecloggingproblems,buttheycanhaveasignificantlossoftreatmentasaresultofchannelflow.Theyaretypicallydesignedforeithercarbonornitrogenremoval(Steinetal.,2006;Steinetal.,2007;Stoneetal.,2002;Stoneetal.,2004),includingthepreventionofexcessiveammoniaemissions(Poachetal.,2004;Poachetal.,2002).

Constructedwetlandsaretypicallycreatedinuplandsettings(e.g.,non‐wetland);accordingly,thesiteassumesthesamebiogeochemicalprocessesthatareinherenttonaturalwetlands.CarbonstocksandGHGemissionsareaffectedbythetypeandquantityofeffluentbeingtreated,thetypeofvegetationinthewetlandcells,andmanagementofthehydrologicregimeswithinthecells.ThemanagementofCH4andN2OfromconstructedwetlandsissomewhatsimilartomanagingGHGemissionsfromwetlandricesystems(Feyetal.,1999;Freemanetal.,1997;Johanssonetal.,2003;Maltais‐Landryetal.,2009;Manderetal.,2005a;Manderetal.,2005b;Piceketal.,2007;Tanneretal.,1997;TeiterandMander,2005;Wuetal.,2009).Ofparticularimportanceisthemaintenanceofwetlandoxidative/reductivepotentialsthataresufficientlypositivetoavoidCH4production(InsamandWett,2008;SeoandDeLaune,2010;Tanneretal.,1997).Thisrequireshigherlevelsofoxygenandlowerlevelsofavailablecarbon.ThemanagementofN2Oemissionsiscomplicatedbythefactthatnitratesareoftenpresentinthewastewatersordrainagewaters,andsoGHGemissionscanbereducedintheconstructedwetlandsifN2gasisemittedinsteadofN2O.CompletedenitrificationtoN2gasrequireshighercarbon/nitrogenratios(Huntetal.,2007;Hwangetal.,2006;Klemedtssonetal.,2005).Thus,thereisanimportantbalancebetweensufficientcarbonforcompletedenitrificationandcopiouscarbonthatdriveswetlandsintothelowredoxconditionsassociatedwithCH4production.


4-13

Thissectionisincludedforcompleteness,butnomethodforconstructedwetlandsisprovidedinthissection.Section5.4.10inChapter5,AnimalAgriculture,providesaqualitativediscussionofestimatingemissionsfromliquidmanurestorageandtreatment‐constructedwetlands.However,Chapter5doesnotprovidemethodstoestimategreenhousegasemissionsfromconstructedwetlands.

4.2.2 Land‐UseChangetoWetlands

Conversionoflandtowetlandsmayinvolverestoringagriculturallandintoafunctioningwetland.However,wetlandscanberestoredfrompreviouslydrainedforestorgrasslands,andthechangetendstovaryfordifferentregionsoftheUnitedStates.Wetlandscanalsobeconstructedinanylocationforwastewatertreatment.Theoriginalconversionofwetlandstoanotherusetypicallyinvolvesanalterationofthenaturalwetlandhydrology.Chapter7,LandUseChange,addressesthistypeofconversion.Restorationofwetlandsentailsreestablishmentoftherequisitehydrologytosupportforest,scrub‐shrub,sedge,oremergentwetlandplantcommunitiesandoccursinfloodplains,riparianzones,depressions,andslopesandvalleys.

4.2.2.1 ActivelyRestoringWetlands

TheeffectofrestoringbothforestedandgrasswetlandswillleadtocarbonsequestrationandCH4emissionsthatwouldbecharacteristicforthatwetlandtype.However,theextenttowhichcarbonsequestration,organicmatterturnover,andgasfluxesreturntoratestypicalforthewetlandtypedependsonmanyfactors,particularlythedegreeofalteration,timesincerestoration,hydrology,anddevelopmentofthevegetation.Ingeneral,restoredsiteswillbecarbonsinksduetosequestrationinthedevelopingbiomass(e.g.,foreststand)andsoils(EulissJretal.,2008).Soilcarbonisexpectedtoincreaseslowlyinforestedsettingsandsomewhatmorerapidlyingrasslandsites(Gleasonetal.,2009);however,theextentandratesofchangeareuncertain.ReestablishmentofthewetlandhydrologywillalsoaltertheCH4fluxfromtherestoredsitesincehydrologicmodificationsforotherlanduseswilltypicallyinvolvedrainageordiversions.RaisingthewatertableandincreasingtheperiodoftimethatthesoilsurfaceiscoveredwithwaterwillincreaseCH4production.However,manyrestoredgrasslandsitesarenotdirectlydrained,andreestablishmentofgrassesinthecatchmentcanshortenthehydroperiod(VanDerKampetal.,1999;Voldsethetal.,2007),thusreducingCH4production.

Conversionofscrub‐shrubwetlandstypicallyinvolvesdrainagetoanon‐wetlandstate,andtheimpositionofcultivationorotherpracticesdependingonthelanduse.Accordingly,therestorationofprior‐convertedscrub‐shrubwetlandstypicallyinvolvesreestablishmentofthenaturalwetlandhydrologyandselectiveplantingtoestablishnativevegetation.ThedevelopmentofthecharacteristicwetlandhydrologyistheprincipalfactoraffectingthecarbonstocksandGHGemissionsfromthesitefollowingconversion,butthetypeofvegetationandtimesinceestablishmentwillalsohavesomeinfluence.

4.2.2.2 CreatedWetlands

Createdwetlandsareengineeredintonon‐wetlandoruplandsites.Typicalexamplesincludemitigationsites,anaerobiclagoons(SeeSection5.4.10inChapter5,AnimalAgriculture)onlivestockoperations,andstormwaterdetentionbasins.TheprincipalactivityaffectingthecarbonstocksandGHGemissionsistheimpositionofahydrologicregimethatinduceshydricsoilpropertiesandsupportshydrophyticplants,inadditiontoclearingofthepreviousvegetationthatmayleadtoachangeinbiomasscarbonstocks.


4-14

4.2.2.3 PassiveRestorationofWetlands

Allowinganareatoregeneratethroughnaturalsuccessionisalsoconsideredaformofrestoration.TheeffectoftherestorationactivitiesonthecarbonstocksandCH4emissionsdependsonwhethertherewashydrologicremediationandthedegreeofvegetationchangeovertime.

4.3 EstimationMethodsSection4.3.1providesmethodsforestimatingliveanddeadbiomassinforested,shrub,andgrasslandwetlands.Section4.3.2providesmethodsforestimatingsoilC,N2O,andCH4emissionsfrommanagednaturallyoccurringwetlands.

4.3.1 BiomassCarboninWetlands

4.3.1.1 RationaleforSelectedMethod

Variousapproachesareusedforestimatingtreebiomasscarbon,butultimatelyeachreliesonallometricrelationshipsdevelopedfromacharacteristicsubsetoftrees.TheForestVegetationSimulator(FVS)hasbeenselectedasthemethodtoestimatetreebiomass.FVSismodel‐basedapproachthatisspecifictoU.S.conditionsandaTier3methodasdefinedbytheIPCC.ThesimulatoristhemostcompletemodelintheUnitedStatestoestimatetreebiomass.RegionalversionsofFVShavebeenrefinedbasedonlargedatabasesdevelopedfrommanyyearsofdatacollectiononforeststandsthroughouttheUnitedStates,therebyprovidingimprovedestimateswhilerequiringfewinputparametersfromtheuser.

BothIPCC(2006)andEPA(2011)considerherbaceousbiomasscarbonstockstobeephemeral,andrecognizethattherearenonetemissionstotheatmospherefollowinggrowthandsenescence.However,withrespecttochangesinlanduse(e.g.,foresttocropland),theIPCC(Lascoetal.,2006)recommendsthatgrazinglandbiomassbecountedintheyearthatlandconversionoccurs(Verchotetal.,2006).AccordingtotheIPCC,accountingfortheherbaceousbiomasscarbonstockduringchangesinlanduseisnecessarytoaccountfortheinfluenceofherbaceousplantsonCO2uptakefromtheatmosphereandstorageintheterrestrialbiosphere.ThemethodisconsideredaTier2methodasdefinedbytheIPCCbecauseitincorporatesfactorsthatarebasedonU.S.specificdata.

Themethodspresentedinthissectionarebasedonthefollowingdefinitions.

Livevegetationbiomass:Livevegetationincludestrees,shrubs,andgrasses.Thetreecarbonpoolincludesabovegroundandbelowgroundcarbonmassoflivetrees,asdefinedinSection6.2.3.1,andtheabovegroundbiomassoftheforestunderstoryisdefinedinSection6.2.3.2.Themethodstoestimatefull‐treeandabovegroundbiomassfortreesgreaterthanoneinchindiameteratbreastheightarebasedonthemodelsprovidedintheforestsection.

MethodforEstimatingLiveandDeadBiomassCarboninWetlands

MethodsforestimatingforestvegetationandshrubandgrasslandvegetationbiomasscarbonstocksuseacombinationoftheForestVegetationSimulatormodelandthebiomasscarbonstockchangesmethodinSection3.5.1ofChapter3,CroplandandGrazingLand.Ifthereisaland‐usechangetoagriculturaluse,methodsforcroplandherbaceousbiomassareprovidedinChapter3.

Thesemethodswerechosenbecausetheyofferthemostconsistentapproachwithinthecontextofthisreport.


4-15

Theforestunderstoryvegetationincludesallbiomassofundergrowthplantsinaforest,includingwoodyshrubsandtreeslessthanoneinchindiameteratbreastheight.

Standingdeadwood(deadbiomass):ThecarbonpoolofstandingdeadwoodinaforestedwetlandisdefinedandestimatedaccordingtothemethodsinSection6.2.3.3ofChapter6,Forestry.

Downdeadorganicmatter—litterlayer(deadbiomass):Downdeadorganicmatterincludesthelitterlayercomposedofsmallpiecesofdeadwood,branches,leaves,androotsinvariousstagesofdecay.Thislayeristypicallydesignatedastheorganiclayerofthesoil.Thispoolalsoincludeslogsinvariousstagesofdecaythatlieonthesoilsurface(e.g.,Section6.2.3.4,down‐deadwood,andSection6.2.3.5,forestfloororlitter).

4.3.1.2 DescriptionofMethod

Provisionsforestimatingabovegroundbiomassforwetlandforestsandaboveandbelowgroundbiomassandcarbonareincludedforshrubandgrasswetlandsinthissection.Sincethevegetativecoveronwetlandsmayvaryfromnaturalcommunitiestoagriculturalcrops,cross‐referencesaremadetoensurecongruitywithSection3.5.1ofChapter3,Croplands,andGrazingLands,andSection6.2.3ofChapter6,Forestry.

Forestvegetation:BiomasscarbonstocksareestimatedforforestsinwetlandsusingthemethodsdescribedinSection6.2.3ofChapter6,Forestry.TheapproachusestheFVS,whichisasystemofgrowthandyieldmodelsthatestimategrowthandyieldforU.S.forests.FVSisanindividualtreemodelandcanestimatebiomasscarbonstockchangefornearlyanytypeofforeststand.TheFireandFuelsExtensiontoFVScanbeusedtogeneratereportsofallliveanddeadbiomasscarbonpoolsinadditiontoharvestedwoodproducts.RegionalvariantsareavailableforFVSthatallowforregion‐specificfocusonspeciesandforestvegetationcommunities.Thedriverforproductivityistheavailabilityofsiteindexcurves,6andtheregionalvariantsincludemanywetlandtreespecies.RegionalvariantsofFVSmayalsoprovideprovisionsforrefiningthebasisforestimatingproductivitybyclassifyingtheareaofinterestintoecologicalunits,habitattype,orplantassociations.However,ifaspecies‐specificcurveisnotavailable,thenadefaultfunctionisusedtoestimatecarbonstockchanges.

Grasslandvegetation:Thechangeincarbonstockforgrasswetlandsisgenerallysmallunlesstherearedroughtconditionsortheareaisactivelymanaged.Incaseswherereportingisrequired,biomasscarbonstockchangescanbeestimatedfollowingalandusechangeusingthemethodinSection3.5.1ofChapter3,CroplandsandGrazingLands.Therearenomethodscurrentlyavailabletoestimatetheshrubcover.

4.3.1.3 ActivityData

Forestedwetlands:ThedataandrequirementsforestimatingthechangesincarbonstocksinwetlandforestsarethesameasthosedescribedforuplandforestsinSection6.2.3.

Grasslandvegetation:ThedataandrequirementsforestimatingthechangesincarbonstocksingrasslandvegetationarethesameasthosedescribedfortotalbiomasscarbonstockchangespresentedintheCroplands/GrazingLandsSections3.5.1.

6Siteindexisthemeasureofaforest’spotentialproductivity.Theheightofthedominantorco‐dominanttreesataspecifiedageinastandarecalculatedinanequationthatusesthetree’sheightandage.Siteindexequationsdifferbytreespeciesandregion.Siteindexcurvesareconstructedbyusingthetreeheightsatabaseageandanequationisderivedfromthecurvestoestimatethesiteindexwhenanindividualtree’sageisnotthesameasthebaseage(Hansonetal.,2002).


4-16

4.3.1.4 ModelOutput

Changeinabovegroundcarbonpoolsassociatedwithwetlandforestsareprovidedforlivevegetation,standingdeadbiomass,anddowndeadbiomass.Changeinlivebiomasscarbonisalsoprovidedforbelowgroundbiomass.Theunitsofreportingaremetrictonnesha‐1CO2‐eq.

4.3.1.5 LimitationsandUncertainty

Estimatesoftheforestbiomasscarbonpoolsinwetlandsareconstrainedbylimiteddataonproductivityresponsetomanagementandaresensitivetothewidearrayofcharacteristicvegetativecommunitiesandsoiltypes.AlthoughFVSisthemostinclusivemodelavailable,manyresultsforwetlandswillstillbebasedondefaultmodelfunctions,becausethereislimiteddataonthegrowthofspecificwetlandspeciesunderparticularmanagementregimes.Accordingly,theresultswillprovidearelativebasisfortrackingchangesovertimeinbiomasscarbon.Table4‐3summarizesadditionallimitationsinthecurrentapproach.

Table4‐3:KeyLimitationstoEstimatingBiomassCarbonPoolsinForestWetlandVegetation

Consideration Limitation

Ratioforbelowgroundbiomass

Aratioisused toestimatebelowgroundbiomassinuplandandwetlandforestsbasedonabovegroundbiomass.Whileacommonratiowillprovideabasisforestimatingrelativechange,itwilllikelyoverorunderestimateactualstocksinmanywetlands.

Responsetomanagementorclimaticconditions

Wetlandvegetationisknowntorespondtomanagementpractices,soil, andclimaticconditions.ThoserelationshipsarenotnecessarilyreflectedinFVSbecausethereisinsufficientbasisforgeneralizedassessmentpurposes.Forexample,inresponsetodynamicwater‐levelfluctuationsduringwetanddrycycles,wetlandsoftenexhibitmajorintraandinterannualshiftsinvegetativestructure,rangingfromopenwatertoemergentherbaceousvegetation.Correspondingly,thealteredsiteconditionsunderthemanagementregimeandthegeneticqualityoftheplantedtreesmayexhibitresponsesthatarenotcapturedbytheexistingallometricrelationshipsinFVS.

ThisshrubandgrasslandmethodisbasedontheassumptionsfoundinChapter3,CroplandandGrazingLand.Essentially,themethodassumesthathalfofthecropbiomassatharvestorpeakforage/shrubbiomassprovidesanaccurateestimateofthemeanannualcarbonstock.Thisassumptionwarrantsfurtherstudy,andthemethodmayneedtoberefinedinthefuture.

Majorsourcesofuncertaintyincludebelowgroundbiomass,vegetationresponsetomanagement,andhydrologicregime(e.g.,seasonalhydroperiod).Uncertaintyinherbaceouscarbonstockchangeswillresultfromlackofprecisionincroporforageyields,residue‐yieldratios,root‐shootratios,andcarbonandcarbonfractions,aswellastheuncertaintiesassociatedwithestimatingthebiomasscarbonstocksfortheotherlanduses.

Measurement,sampling,andregression/modelingerrorsareallpartoftheestimationprocessinFVS.Somesimilarmeasureoftherepresentativenessofselectedforestinventoryandanalysisplotstotheentities’forestsisneeded.Uncertaintiesaboutcarbonconversionfactorsarealsosignificantinsomecases.


4-17

4.3.2 SoilC,N2O,andCH4inWetlands

4.3.2.1 RationaleofMethod

Theproductionandconsumptionofcarboninwetland‐dominatedlandscapesareimportantforestimatingthecontributionofGHGs,includingCO2,CH4,andN2Oemittedfromthoseareastotheatmosphere.ThegenerationandemissionofGHGsfromwetland‐dominatedlandscapesarecloselyrelatedtoinherentbiogeochemicalprocessesthatalsoregulatethecarbonbalance(RoseandCrumpton,2006).However,thoseprocessesarehighlyinfluencedbythelanduse,vegetation,soilorganisms,chemicalandphysicalsoilproperties,geomorphology,andclimate(SmemoandYavitt,2006).

Giventhiscomplexity,aprocess‐basedmodelingapproachisdesirablebecausetheseapproachestypicallyaccountformoreofthevariabilitythansimpleremissionfactormethods(IPCC,2006).However,fewprocess‐basedmodelshavebeentestedsufficientlytobeusedforoperationalreportingofGHGemissions.OneofthemorewidelytestedmodelsforestimatingGHGfluxesfromwetlandsistheDNDCmodel.DNDCisaprocess‐basedbiogeochemicalmodelthatisusedtopredictplantgrowthandproduction,carbonandnitrogenbalance,andgenerationandemissionofsoil‐bornetracegasesbymeansofsimulatingcarbonandnitrogendynamicsinnaturalandagriculturalecosystems(Lietal.,2000;Miehleetal.,2006;Stangetal.,2000)andforestedwetlands(Zhangetal.,2002).Themodelisdesignedtoexplicitlyconsideranaerobicbiogeochemicalprocesses,whicharefundamentaltoaddressingsoilcarbondynamicsandtraceGHGdynamicsinwetlands(Trettinetal.,2001).Itintegratesdecomposition,nitrification–denitrification,photosynthesis,andhydro‐thermalbalancewithintheecosystem.Thesecomponentsaremainlydrivenbyenvironmentalfactors,includingclimate,soil,vegetation,andmanagementpractices.

DNDChasbeentestedandusedforestimatingGHGemissionsfromforestedecosystemsinawiderangeofclimaticregions,includingboreal,temperate,subtropical,andtropical(Kesiketal.,2006;Kieseetal.,2005;Kurbatovaetal.,2008;Lietal.,2004;Stangetal.,2000;Zhangetal.,2002),andsimilarlyforgrasslandsandcultivatedwetlands(Giltrapetal.,2010;Rafiqueetal.,2011).

4.3.2.2 DescriptionofMethod

Themethodconsistsofusingtheprocess‐basedmodel—DNDC—toestimatethechangesinsoilorganiccarbon(SOC)stocks,CH4,andN2Oemissions,basedonthestandingbiomassandplantgrowththatareprovidedbythevegetationmethodoutlinedabove(Section4.3.1),wetlandcharacteristics,andtheplannedmanagementactivities.ThemodelsimulatesSOCstocks,CH4,andN2Oemissionsatthebeginningofthereportingperiodbasedonanassessmentofinitialconditionsatthesite;thenthemodelsimulatesthereportingperiodbasedonthecurrent/recentmanagementactivityandanychangesinthewetlandconditions.Thisinformationcharacterizesthephysicalandchemicalsoilpropertiesthatinturninteractwiththeclimaticregime,managementpractices,and

MethodforEstimatingSoilC,N2OandCH4 inWetlands

TheDNDCprocess‐basedbiogeochemicalmodelisthemethodusedforestimatingsoilC,N2O,andCH4emissionsfromwetlands.

DNDCpredictssoilcarbonandnitrogenbalanceandgenerationandemissionofsoil‐bornetracegasesbysimulatingcarbonandnitrogendynamicsinnaturalandagriculturalecosystems(Lietal.,2000;Miehleetal.,2006;Stangetal.,2000)andforestedwetlands(Daietal.,2011;Zhangetal.,2002),usingplantgrowthestimatedasdescribedinSection4.3.1.


4-18

thevegetationresponse.Thereportedemissionsforthelandparcelmustreflectthetotalfortheentirelandarea.Accordingly,theper‐unitareaemissionratesfromDNDCareexpandedbasedonthetotalwetlandareaforthelandparceltoestimatetotalemissions.

Equation4‐1isusedtoestimateSOCstockchangesfromaparceloflandinawetland:

Equation4‐2isusedtoestimateCH4emissionsfromaparceloflandinawetland:

N2OemissionsareestimatedforalandparcelinawetlandusingEquation4‐3:

Equation4‐1:ChangeinSoilOrganicCarbon StocksforWetlands

ΔCSoil=(SOCt‐SOCt‐1)xAxCO2MW

Where:

ΔCSoil =Annualchangeinmineralsoilorganiccarbonstock(metrictonsCO2‐eqyear‐1)

SOCt =Soilorganiccarbonstockattheendoftheyear(metrictonsCha‐1)

SOCt‐1 =Soilorganiccarbonstockatthebeginningoftheyear(metrictonsCha‐1)

A =Areaofparcel(ha)

CO2MW =RatioofmolecularweightofCO2toC=44/12(metrictonsCO2(metrictonsC)‐1)

Equation4‐2:MethaneEmissionsfromWetlands

CH4=ERxAxCH4MWxCH4GWP

Where:

CH4 =TotalCH4emissionsfromthelandparcel(metrictonsCO2‐eqyear‐1)

ER =Emissionrateonaperunitwetlandarea(metrictonsCH4ha‐1year‐1)

A =Area(ha)

CO2MW =RatioofmolecularweightofCH4toC=16/12(metrictonsCH4(metrictonsC)‐1)

CH4GWP =GlobalwarmingpotentialofCH4

Equation4‐3:NitrousOxideEmissionsfromWetlands

N2O=ERxAxCO2MWxCH4GWP

Where:

N2O =TotalN2Oemissionsfromthelandparcel(metrictonsCO2‐eqyear‐1)

ER =Emissionrateonaperunitlandarea(metrictonsN2Oha‐1year‐1)

A =Area(ha)

CO2MW =RatioofmolecularweightofN2OtoN=44/28

(metrictonsN2O(metrictonsN2O‐N)‐1)

CH4GWP =GlobalwarmingpotentialofN2O


4-19

ToestimatetheSOCstockchanges,CH4,andN2Oemissions,DNDCrequiresaconsiderableamountofinformationtocharacterizetheplantproduction(Section4.3.1),wetlandcharacteristics,andmanagementactivities.TheinitialstepinapplyingthemethodistoparameterizeDNDCusingthebaselinesoilconditions,alongwiththecorrespondingforestorgrasslandconditions.Forexample,ifaforestplantationistobeharvestedandregeneratedduringthereportingperiod,theinitialconditionsshouldreflectthepre‐harvestconditions.Basedontheinitialconditions,themodelsimulatesbaselinefluxesandtheSOCstockpriortothereportingperiodfortheentity.Subsequently,theentityspecifiesthetypeofmanagementactivity(s)changesthatoccurredduringthereportingperiod(ifanyoccurred).Provisionsareavailabletohavemultiplemanagementactivitiesonasingletractifthereweremixedactivities.Climaticfactors,especiallyprecipitation,canaffectcarbonturnoverandwetlandconditions.Consequently,weatherdataareakeyinputtoDNDC,andwillbeprovidedfromaclimatologicaldataset.

ThesimulationoutputattheendofeachyearisusedtoestimatechangeinSOCstocksandthetotalamountofCH4andN2Oemissionsfortheyear.AnnualchangesinSOCcanbeestimatedbasedonthedifferencebetweenyears,andthetotalchangeinemissionscanbeestimatedbycombiningthechangesinSOCpoolswiththeannualCH4andN2Oflux.

4.3.2.3 ActivityData

ActivitydatafortheapplicationofDNDCaresummarizedinTable4‐4.Vegetationmanagementinformationaffectstheamountoforganicmatterthatisavailablefordecompositionprocesses.Watermanagementinformationconveyshowthedrainagesystemaffectsthesoilwatertabledynamicascomparedtoanundrainedcondition.Thesoiltillageinformationisusedtoconveywhenthesurfacesoilisdisturbedoritselevationchangedbecauseoftheassociatedeffectsondecomposition.ThefertilizationinformationisneededbecausetheadditionofnitrogengreatlyaffectsdecompositionandN2Oproduction.Inaddition,landusehistoryinfluencestheamountofsoilorganiccarbon.Ifanentityiscomposedofdifferentwetlandtypes,itisrecommendedthatseparateestimatesbepreparedbecausethecarbonturnoverrateandGHGemissionscanvarywidelydependingonhydricsoilpropertiesandthetypeofvegetation.

Table4‐4:ActivityDataforApplicationofDNDC

Category ManagementPractice Data

Vegetationmanagement

Grazingormanagementeventsshouldbeincludedtocapturetheinfluenceoncarboninputtosoilsandsubsequenteffectsonthesoilcarbonstocks.

Harvesting:date,harvest,orcutfraction Understorythinningorchopping:date,

choppedfraction Prescribedfire:date,proportionofforest

floor,andunderstoryconsumed Treeplanting:date,species,density

Watermanagementregime

Watertableresponsetothedrainagesystem,dailydata.

Drainagesystem:date,controlledwatertableelevation

Soilmanagement

Applicationofsoilamendmentsorsitepreparationpracticesfortreeplanting. Typeofsitepreparation

Fertilizationpractices

ApplicationsofmineralororganicnitrogenfertilizerswillbeneededtosimulatetheeffectonN2Oemissions.

Fertilizationfrequency,date,applicationrate(N,Pkgha‐1)

Landusehistory

Summaryoflandusepracticesoverthepast5years.Forassessingifprioruseaffectsparameterization.Thetimesinceachangeinlandmanagementpracticeforassessingeffectsondecomposition.

Fertilizationregimes,drainageregimes,cropping,orforestmanagementhistory


4-20

4.3.2.4 AncillaryData

TheDNDCmodelrequiresrelativelydetailedinformationaboutthesite(Table4‐5).Whiledefaultvaluesareavailableformostparameters,someentity‐specificdataareneededtoproducereasonableestimates.Mostoftherequiredsoilsinputdataareavailablefromthenationalsoilsdatabase.7Similarly,climatedataareavailablefromtheNationalClimateDataCenter.8

Table4‐5:InputInformationNeededfortheApplicationofDNDC

Category Data

ClimateDailymaximumandminimumtemperature,dailyrainfall; nitrogendepositioninrainfall,orusedefaultvalue.

Vegetation StandingbiomassandbiomassanddetritalinputsprovidedinSection4.3.1;belowgroundbiomassestimatedbasedonabovegroundbiomass.

Soil

Hydraulicparametersandphysicalandchemicalcomponents, includingthickness;layers;hydraulicconductivity;porosity;fieldcapacity;wiltingpoint;carboncontent;pH;organicmatterfractions;contentofstone,sand,silt,andclay;andbulkdensityformajorsoillayers.

Hydrology WatertablebelowsurfaceasdailyinputorstartingpositionandDNDCcanestimateGHGemissionsandsinksusingempiricalfunctions.

4.3.2.5 ModelOutput

ModeloutputincludesannualestimatesofCH4,N2Oemissions,andchangesinsoilorganiccarbonstocks.TheunitsofreportingaremetrictonsCO2‐eqha‐1.

4.3.2.6 LimitationsandUncertainty

Themodelstoestimatecarbonsequestrationinvegetationarerobustwithrespecttospeciesandcommunitycomposition.However,uncertaintiesmaybehigherthanforuplandsbecauseoflimitedbackgroundinformation.ThemeritoftherecommendedapproachisthatitensuresconsistencyforestimatingchangesinthevegetativecarbonpoolamonglandtypesandusesbyusingcommonmethodsasdescribedinSection4.3.1.However,thisapproachcomplicatestheapplicationofDNDCforestimatingchangesinsoilcarbonpoolsandfluxesbecauseitcontainsprovisionsforsequesteringcarbonincrops,grasslands,andforestvegetation.Accordingly,DNDCwouldhavetoundergosubstantialrevisionstoaccommodatethevegetativecomponentasaninputvariablebecausethevegetationgrowthfunctionsareintegralwiththeconsiderationofhydrologicprocesses(especiallyevapotranspiration)andbiogeochemicalprocesses.TheDNDCmodelcouldbeusedasastand‐alonetoolforwetlands,butunfortunately,theproductionorcarbonsequestrationfunctionshavenotbeenvalidatedformanyofthewetlandplantcommunities.

Theavailabilityofwatertabledataisessentialtomodelingthecarboncycleinwetlandsoils.Sincethelackofsite‐specificwatertabledataforasufficientperiodislikelyaconstraintformostentities,anapproachincorporatingahydrologicmoduleorlook‐uptableisneeded.Hydrologicmodelsthatprovideinformationonwatertabledynamicsareinherentlycomplex,buttheycanbeeffective(Dai.etal.,2010).Accordingly,thedevelopmentofcharacteristicwatertableconditionsforarangeofclimatologicalandsoilsettingswouldbeaviableapproachthatcanalsoincorporatewatermanagementeffects(e.g.,Skaggsetal.,2011).

7SeeNationalCooperativeSoilSurveySoilCharacterizationdatahttp://soils.usda.gov/survey/nscd/.8SeeNOAANationalClimaticDataCenterhttp://www.ncdc.noaa.gov/.


4-21

Tidalfreshwaterforestedwetlands,whichoccurtoalimitedextentalongtheAtlantic,Gulf,andPacificcoasts,areaspecialcase.Thetidalinfluenceonwatertabledynamicscanmakecharacterizingthewatertableregimeofsuchsitesmoredifficult.ForDNDCtosimulatethecarbondynamicswouldrequiredetaileddataondailywatertabledynamics,andsuchdetaileddataareunavailable.

WhiletheeffectsofthevariousmanagementregimesonsoilcarbonpoolsandGHGfluxeshavenotbeenwidelystudied,thisismoreofaconsiderationwithrespecttouncertaintiesintheestimatesasopposedtoalimitationtoitsapplication.TheDNDCframeworkisrobustbecauseitisaprocess‐basedmodelthathasbeenvalidatedinawidevarietyofwetlandtypesandsoils.However,ithasnotbeenextensivelytestedonHistosolsorpeatsoils,especiallywithrespecttochangesinsoilcarbonstocks.ThemodelwasvalidatedsuccessfullyforestimatingCH4frommicotopographicpositionsinapeatland(Zhangetal.,2002),butadditionalworkisneededtobetteraddressthewidearrayofmanagedHistosolsthatexistacrossthecountry.

Similarly,thismethodisnotapplicabletoconstructedwetlands,impoundments,orshallowreservoirsystemsthathaveextendedperiodsofponding;thosesiteswouldtendtohavedynamicsmoresimilartoalakeorpondasopposedtoaterrestrialecosystem.

Withrespecttotheforestmodel,accuracyoftheestimatesisdependentonapplicabilityoftheavailablesiteindexcurves.Whilethegeneralcurvesareavailableforallspecies,theymaynotaccuratelyrepresentthesiteortheentity’smanagementregime.ProvisionsareincludedwithinFVSforcustomizingthetreesiteindexcurves,whichcouldbeimportantforanentityespeciallyifgenetically‐improvedplantingstockandfertilizationregimesareemployed.

Detritalorganicmatteristhesourcefordecompositionprocesses.Theeffectofvegetationonwetlandcarbondynamicsispromulgatedthroughtheamountoforganicmatterandthewaterregime(e.g.,evapotranspiration).Accordingly,theaccuracyofthevegetationproductivityandturnoverwillaffecttheestimatesofthesoilcarbonpoolsandGHGflux.

WatertablepositionisthemostcriticalfactoraffectingCH4andN2Ofluxfromthewetlandsoil(Trettinetal.,2006).Accordingly,considerationstoimprovethatestimateasdiscussedinSection4.3.2willimprovetheestimatesofGHGemissionsfromthesoil.Thereareotheruncertaintiesintheactivityandancillarydata,aswellasmodelstructurethatcancreatebiasandimprecisionintheresultingestimates.Wetlandstypicallyexistinamosaicwithuplandforests,grasslands,andcultivatedlands.Accordingly,theaccuracyofpartitioningtheentityintoupland(agriculture,forest)andwetlandswillaffecttheaccuracyoftheestimates.

4.4 ResearchGapsforWetlandManagementWetlandmanagement,anditsinfluenceonGHGemissions,isnotaswellstudiedassomeoftheothermanagementpracticesinthisreport,suchastillageincroplandsorforestharvestingpracticesinuplands.ThereisthepotentialforimprovingtheestimationofGHGemissionsassociatedwithdifferentmanagementpracticesinthefutureiftherearemonitoringactivitiesandstudiestofillinformationgaps.Aselectnumberofinformationneedsandresearchgapsareidentifiedhere.

The2013Supplementtothe2006IntergovernmentalPanelonClimateChange(IPCC)Guidelinesprovidenewguidanceforestimatingemissionsfromdrainedinlandorganicsoils,rewettedorganicsoils,coastalwetlands,inlandwetlandmineralsoils,andconstructedwetlandsforwastewatertreatment(Blainetal.,2013).Thesenewlydevelopedguidelineswillbecomparedtothetechnicalmethodsprovidedinthisreport.


4-22

Watertablepositionistheprincipalfactoraffectingcarbondynamicsinwetlands;unfortunatelythereisalackoflong‐termdata,whichisneededtocharacterizethewatertableresponsetoamanagementregimeandtoprovideabasisforvalidatingassessmenttools.EstablishmentofanetworkofwatertablemonitoringsiteswithinselectedUSDAForestServiceexperimentalforestsandrangesandUSDA‐AgriculturalResearchService(ARS)experimentstationscouldprovidethecontinuityinmeasurementsandlinkageswithcommonmanagementpracticestorepresentthemajorsoilandclimaticconditionintheUnitedStates.

Improvingmodelingcapabilitiesthatintegratesurroundingareaswiththewetlandsthatreceivesurfaceandsubsurfacedrainagewaterswillallowformodelingtheflowsofnutrientsandorganicmatterintowetlandsandsubsequentlossestootherwetlandsbeyondtheentity’soperation.Thistypeofassessmentframeworkisusedinseveralestablishedspatially‐explicithydrologicmodels;theneedistointegratethebiogeochemistry.Linkedmodelscanbeusedatpresent;butdevelopmentofafunctionally‐integratedsystemisneededtosupportbroad‐basedapplications.

Thereisaneed,generally,forimprovedinformationonbiomassproductionandallocationinmanagedwetlands.ThesedatacouldbeobtainedthroughacoordinatedmonitoringprogramemployingUSDA‐ForestServiceexperimentalforestsandranges,USDA‐ARSexperimentstations,andU.S.DepartmentoftheInteriorwildliferefugestomonitorproductionofkeyspeciesorvegetationtypesinassociationwithcommonmanagementprescriptions.Thereisalsoneedformoredetailedmechanisticresearchtoprovideinformationonenergy,water,andGHGdynamicsonselectedmanagedsites;thisinformationiscriticalforvalidatingprocess‐basedmodels.

Field‐basedstudiesareneededtodevelopmorecompletedatabasesthatprovideancillarydataforGHGestimation,particularityCH4emissionsforDNDCorsimilarprocess‐basedmodels,ratherthanrelyingonentityinput,whichwilllikelybechallenging.Akeyattributeofthisworkshouldbetheconsiderationoftheinherentspatialandtemporalvariabilitywithinasite.

FurtherquantificationofthecontrollingandthresholdparametersandassociateduncertaintywithinDNDCorsimilarprocess‐basedmodelstoestimatetracegasemissionsiswarranted.ThisworkcouldalsosuggestapathtowardsdevelopmentofanassessmenttoolthatwasnotreliantonawidearrayofparameterstoeffectivelysimulatetheGHGdynamicsofthesite.

AmorerobustandextensivedatabaseonGHGemissionsfromfreshwatertidal(salinity<0.5‰)palustrinewetlandsisneededtomorefullyunderstandthedriversofemissions,inadditiontoprovidingamorecompletedatasetforparameterizationandevaluationofprocess‐basedmodels.

Studiesonindividualsitesandmeta‐analysesofexistingdataareneededtofullyevaluatethenetGHGfluxforCH4,N2O,andsoilcarbon.MoststudiesonlyconsideroneoftheGHGsandmaymasksomeofthedifferencesinfluxesamongtheGHGsassociatedwithamanagementactivity.

ConstructedwetlandsarediscussedqualitativelyinSection5.4.10ofChapter5,AnimalProductionSystemsforLiquidManureStorageandTreatmentinConstructedWetlands.Moreresearchisneededinthisareatoaccuratelyestimateemissionsfromconstructedwetlands.

ThislistisnotexhaustivebutisintendedtoprovidesomedirectionforimprovingtheestimationmethodsforGHGemissionfromwetlands.


4-23

Chapter4References

Abu‐Zreig,M.,R.P.Rudra,H.R.Whiteley,M.N.Lalonde,etal.2003.PhosphorusRemovalinVegetatedFilterStrips.J.Environ.Qual.,32(2):613‐619.

Albaugh,T.J.,H.L.Allen,P.M.Dougherty,andK.H.Johnsen.2004.Long‐termgrowthresponsesofloblollypinetooptimalnutrientandwaterresourceavailability.ForestEcologyandManagement,192(3‐A):19.

Ambus,L.P.1991.Comparisonofdenitrificationintworipariansoils.SoilScienceSocietyofAmericaJournal,55(994‐997).

Armentano,T.V.,andE.S.Menges.1986.Patternsofchangeinthecarbonbalanceoforganicsoil‐wetlandsofthetemperatezone.JournalofEcology,74:755‐774.

Balestrini,R.,C.Arese,C.A.Delconte,A.Lotti,etal.2011.NitrogenremovalinsubsurfacewaterbynarrowbufferstripsintheintensivefarminglandscapeofthePoRiverwatershed,Italy.EcologicalEngineering,37:148‐157.

Bedard‐Haughn,A.,A.L.Matson,andD.J.Pennock.2006.Landuseeffectsongrossnitrogenmineralization,nitrification,andN2Oemissionsinephemeralwetlands.SoilBiologyandBiochemistry,38(12):3398‐3406.

Blain,D.,C.Row,J.Alm,K.Byrne,etal.2006IPCCGuidelinesforNationalGreenhouseGasInventories.Retrievedfromhttp://www.ipcc‐nggip.iges.or.jp/public/2006gl/pdf/4_Volume4/V4_07_Ch7_Wetlands.pdf.

Blain,D.,R.Boer,S.Eggleston,S.Gonzalez,etal.2013.2013Supplementtothe2006IntergovernmentalPanelonClimateChangeGuidelinesforNationalGreenhouseGasInventories:Wetlands.http://www.ipcc‐nggip.iges.or.jp/home/docs/wetlands/Wetlands_Supplement_precopyedit.pdf.

Borin,M.,M.Vianello,F.Morari,andG.Zanin.2005.EffectivenessofbufferstripsinremovingpollutantsinrunofffromacultivatedfieldinNorth‐EastItaly.Agriculture,Ecosystems&Environment,105(1‐2):101‐114.

Bowden,W.,W.McDowell,C.Asbury,andA.Finley.1992.Ripariannitrogendynamicsintwogeomorphologicallydistincttropicalrainforestwatersheds:nitrousoxidefluxes.Biogeochemistry,18(2):77‐99.

Bridgham,S.,J.Megonigal,J.Keller,N.Bliss,etal.2006.ThecarbonbalanceofNorthAmericanwetlands.Wetlands,26(4):889‐916.

Bruland,G.L.,andR.A.MacKenzie.2010.NitrogenSourceTrackingwithδ15NContentofCoastalWetlandPlantsinHawaii.JournalofEnvironmentalQuality,39:409‐419.

Chaubey,I.,L.Chiang,M.W.Gitau,andS.Mohamed.2010.Effectivenessofbestmanagementpracticesinimprovingwaterqualityinapasture‐dominatedwatershed.JournalofSoilandWaterConservation,65(6):424‐437.

Chen,G.Q.,L.Shao,Z.M.Chen,Z.Li,etal.2011.Low‐carbonassessmentforecologicalwastewatertreatmentbyaconstructedwetlandinBeijing.EcologicalEngineering,37(4):622‐628.

Cho,J.,G.Vellidis,D.D.Bosch,R.Lowrance,etal.2010.WaterqualityeffectsofsimulatedconservationpracticescenariosintheLittleRiverExperimentalwatershed.JournalofSoilandWaterConservation,65(6):463‐473.

Costa,C.,C.Dijkema,M.Friedrich,P.Garcia‐Encina,etal.2000.Denitrificationwithmethaneaselectrondonorinoxygen‐limitedbioreactors.AppliedMicrobiologyandBiotechnology,53(6):754‐762.

Cowardin,L.M.,V.Carter,F.C.Golet,andE.T.LaRoe.1979.ClassificationofwetlandsanddeepwaterhabitatsoftheUnitedStates.(FWS/OBS‐79/31).

Dai,Z.,C.Trettin,C.Li,H.Li,etal.2011.EffectofassessmentscaleonspatialandtemporalvariationsinCH4,C02,andN20fluxesinaforestedwetland.Water,Air,andSoilPollution1‐13.


4-24

Dai.,Z.,C.Trettin,G.Sun,D.Amatya,etal.2010.Bi‐CriteriaevaluationoftheMIKESHEmodelforaforestedwatershedontheSouthCarolinacoastalplain.Hydrol.EarthSyst.Sci.,14:1033‐1046.

Davidson,E.A.,M.Keller,H.E.Erickson,L.V.Verchot,etal.2000.TestingaConceptualModelofSoilEmissionsofNitrousandNitricOxides.BioScience,50(8):667‐680.

Davis,J.H.,S.M.Griffith,W.R.Horwath,J.J.Steiner,etal.2008.Denitrificationandnitrateconsumptioninanherbaceousriparianareaandperennialryegrassseedcroppingsystem.SoilScienceSocietyofAmericaJournal,72:1299‐1310.

deKlein,C.,R.S.A.Novoa,S.Ogle,K.A.Smith,etal.2006.Chapter11:N2Oemissionsfrommanagedsoil,andCO2emissionsfromlimeandureaapplication.In2006IPCCguidelinesfornationalgreenhousegasinventories,Vol.4:Agriculture,forestryandotherlanduse,S.Eggleston,L.Buendia,K.Miwa,T.NgaraandK.Tanabe(eds.).Kanagawa,Japan:IGES.

Dhondt,K.,P.Boeckx,G.Hofman,andO.VanCleemput.2004.Temporalandspatialpatternsofdenitrificationenzymeactivityandnitrousoxidefluxesinthreeadjacentvegetatedriparianbufferzones.BiologyandFertilityofSoils,40(4):243‐251.

Dillaha,T.A.,J.H.Sherrard,D.Lee,S.Mostaghimi,etal.1988.Evaluationofvegetativefilterstripsasabestmanagementpracticeforfeedlots.JournaloftheWaterPollutionControlFederation,60:1231‐1238.

Dillaha,T.A.,R.B.Reneau,S.Mostaghimi,andD.Lee.1989.Vegetativefilterstripsforagriculturalnonpointsourcepollutioncontrol.TransactionsoftheAmericanSocietyofAgriculturalEngineers,32:513‐519.

Dodla,S.K.,J.J.Wang,R.D.DeLaune,andR.L.Cook.2008.Denitrificationpotentialanditsrelationtoorganiccarbonqualityinthreecoastalwetlandsoils.ScienceoftheTotalEnvironment,407(1):471‐480.

Elgood,Z.,W.D.Robertson,S.L.Schiff,andR.Elgood.2010.Nitrateremovalandgreenhousegasproductioninastream‐beddenitrifyingbioreactor.EcologicalEngineering,36(11):1575‐1580.

EulissJr,N.H.,andD.M.Mushet.1996.Water‐levelfluctuationinwetlandsasafunctionoflandscapeconditionintheprairiepotholeregion.Wetlands,16:587–593.

EulissJr,N.H.,L.M.Smith,D.A.Wilcox,andB.A.Browne.2008.LinkingEcosystemProcesseswithWetlandManagementGoals:ChartingaCourseforaSustainableFuture.Wetlands,28(3):553‐562.

Faubert,P.,P.Tiiva,Å.Rinnan,S.Räty,etal.2010.Effectofvegetationremovalandwatertabledrawdownonthenon‐methanebiogenicvolatileorganiccompoundemissionsinborealpeatlandmicrocosms.AtmosphericEnvironment,44(35):4432‐4439.

Faulkner,S.,W.Barrow,B.Keeland,S.Walls,etal.2011.EffectsofconservationpracticesonwetlandecosystemservicesintheMississippiAlluvialValley.EcologicalApplications,21(sp1):S31‐S48.

Faulwetter,J.L.,V.Gagnon,C.Sundberg,F.Chazarenc,etal.2009.Microbialprocessesinfluencingperformanceoftreatmentwetlands:Areview.EcologicalEngineering,35(6):987‐1004.

Fey,A.,G.Benckiser,andJ.C.G.Ottow.1999.Emissionsofnitrousoxidefromaconstructedwetlandusingagroundfilterandmacrophytesinwaste‐waterpurificationofadairyfarm.BiologyandFertilityofSoils,29(4):354‐359.

Flite,O.P.,R.D.Shannon,R.R.Schnabel,andR.R.Parizek.2001.NitrateRemovalinaRiparianWetlandoftheAppalachianValleyandRidgePhysiographicProvince.J.Environ.Qual.,30(1):254‐261.

Freeman,C.,M.A.Lock,S.Hughes,B.Reynolds,etal.1997.Nitrousoxideemissionsandtheuseofwetlandsforwaterqualityamelioration.EnvironmentalScienceandTechnology,31(8):2438‐2440.


4-25

Giltrap,D.,C.Li,andS.Saggar.2010.DNDC:Aprocess‐basedmodelforgreenhousegasfluxesfromagriculturalsoils.Agriculture,EcosystemsandEnvironment,136:292‐300.

Gleason,R.A.,B.A.Tangen,B.A.Browne,andN.H.EulissJr.2009.GreenhousegasfluxfromcroplandandrestoredwetlandsinthePrairiePotholeRegion.SoilBiologyandBiochemistry,41(12):2501‐2507.

Gleason,R.A.,N.H.Euliss,B.A.Tangen,M.K.Laubhan,etal.2011.USDAconservationprogramandpracticeeffectsonwetlandecosystemservicesinthePrairiePotholeRegion.EcologicalApplications,21(sp1):S65‐S81.

Groffman,P.M.,A.J.Gold,andK.Addy.2000.Nitrousoxideproductioninriparianzonesanditsimportancetonationalemissioninventories.Chemosphere:GlobalChangeScience,2(3):291‐299.

Hanson,E.J.,D.L.Azuma,andB.A.Hiserote.2002.SiteIndexEquationsandMeanAnnualIncrementEquationsforPacificNorthwestResearchStationForestInventoryandAnalysisInventories,1985‐2001.Portland,OR:U.S.DepartmentofAgriculture,ForestService,PacificNorthwestResearchStation.http://www.fs.fed.us/pnw/pubs/pnw_rn533.pdf.

Hill,A.R.,K.J.Devito,S.Campagnolo,andK.Sanmugadas.2000.Subsurfacedenitrificationinaforestriparianzone:Interactionsbetweenhydrologyandsuppliesofnitrateandorganiccarbon.Biogeochemistry,51(2):193‐223.

Hoffmann,C.C.,C.Kjaergaard,J.Uusi‐Kamppa,H.C.BruunHansen,etal.2009.Phosphorusretentioninriparianbuffers:Reviewoftheirefficiency.J.Environ.Qual.,38:1942‐1955.

Hopfensperger,K.N.,C.M.Gault,andP.M.Groffman.2009.Influenceofplantcommunitiesandsoilpropertiesontracegasfluxesinripariannorthernhardwoodforests.ForestEcologyandManagement,258(9):2076‐2082.

Hunt,P.G.,T.A.Matheny,andA.A.Szogi.2003.Denitrificationinconstructedwetlandsusedfortreatmentofswinewastewater.JournalofEnvironmentalQuality,32(2):727‐735.

Hunt,P.G.,T.A.Matheny,andK.C.Stone.2004.Denitrificationinacoastalplainriparianzonecontiguoustoaheavilyloadedswinewastewatersprayfield.JournalofEnvironmentalQuality,33:2367‐2374.

Hunt,P.G.,T.A.Matheny,andK.S.Ro.2007.Nitrousoxideaccumulationinsoilsfromriparianbuffersofacoastalplainwatershedcarbon/nitrogenratiocontrol.JEnvironQual,36(5):1368‐1376.

Hwang,S.,K.Jang,H.Jang,J.Song,etal.2006.FactorsAffectingNitrousOxideProduction:AComparisonofBiologicalNitrogenRemovalProcesseswithPartialandCompleteNitrification.Biodegradation,17(1):19‐29.

Insam,H.,andB.Wett.2008.ControlofGHGemissionatthemicrobialcommunitylevel.WasteManagement,28(4):699‐706.

IPCC.2006.2006IntergovernmentalPanelonClimateChangeNationalGreenhouseGasInventoryGuidelines.Hayama,Japan:IGES.

Jetten,M.S.M.2008.Themicrobialnitrogencycle.EnvironmentalMicrobiology,10:2903‐2909.Johansson,A.E.,Å.KasimirKlemedtsson,L.Klemedtsson,andB.H.Svensson.2003.Nitrousoxide

exchangeswiththeatmosphereofaconstructedwetlandtreatingwastewater:Parametersandimplicationsforemissionfactors.Tellus,SeriesB:ChemicalandPhysicalMeteorology,55(3):737‐750.

Jordan,T.E.,D.E.Weller,andD.L.Correll.1998.Denitrificationinsurfacesoilsofariparianforest:Effectsofwater,nitrateandsucroseadditions.SoilBiologyandBiochemistry,30(7):833‐843.

Jordan,T.E.,D.F.Whigham,K.H.Hofmockel,andM.A.Pittek.2003.Nutrientandsedimentremovalbyarestoredwetlandreceivingagriculturalrunoff.JEnvironQual,32(4):1534‐1547.

Kadlec,R.H.,andR.L.Knight.1996.TreatmentWetlands.BocaRation,FL:LewisPublishers.


4-26

Kelly,J.M.,J.L.Kovar,R.Sokolowsky,andT.B.Moorman.2007.Phosphorusuptakeduringfouryearsbydifferentvegetativecovertypesinariparianbuffer.NutrientCyclinginAgroecosystems,78:239‐251.

Kesik,M.,N.Brüggemann,R.Forkel,R.Kiese,etal.2006.FuturescenariosofN2OandNOemissionsfromEuropeanforestsoils.J.Geophys.Res.,111:2018‐2022.

Kiese,R.,C.Li,D.W.Hilbert,H.Papen,etal.2005.RegionalapplicationofPnET‐DNDCforestimatingtheN2OsourcetrengthoftropicrainforestsintheWetTropicsofAustralia.GlobalChangeBiology,11:128‐144.

Kim,D.G.,T.M.Isenhart,T.B.Parkin,R.C.Schultz,etal.2009a.Nitrateanddissolvednitrousoxideingroundwaterwithincroppedfieldsandriparianbuffers.BiogeosciencesDiscuss.,6(1):651‐685.

Kim,D.G.,T.M.Isenhart,T.B.Parkin,R.C.Schultz,etal.2009b.Nitrousoxideemissionsfromriparianforestbuffers,warm‐seasonandcool‐seasongrassfilters,andcropfields.BiogeosciencesDiscuss.,6(1):607‐650.

Klemedtsson,L.,K.VonArnold,P.Weslien,andP.Gundersen.2005.SoilCNratioasascalarparametertopredictnitrousoxideemissions.GlobalChangeBiology,11(7):1142‐1147.

Knowles,R.2005.Denitrifiersassociatedwithmethanotrophsandtheirpotentialimpactonthenitrogencycle.EcologicalEngineering,24(5):441‐446.

Kurbatova,J.,C.Li,A.Varlagin,X.Xiao,etal.2008.ModelingcarbondynamicsintwoadjacentspruceforestswithdifferentsoilconditionsinRussia.Biogeosciences,5:969‐980.

Lasco,R.D.,S.Ogle,J.Raison,L.Verchot,etal.2006.Chapter5:Cropland.In2006IPCCGuidelinesforNationalGreenhouseGasInventories,S.Eggleston,L.Buendia,K.Miwa,T.NgaraandK.Tanabe(eds.).Japan:IGES,IPCCNationalGreenhouseGasInventoriesProgram.

Lee,P.,C.Smyth,andS.Boutin.2004.QuantitativereviewofriparianbufferwidthguidelinesfromCanadaandtheUnitedStates.JournalofEnvironmentalManagement,70(2):165‐180.

Li,C.,J.Aber,F.Stange,K.Butterbach‐Bahl,etal.2000.Aprocess‐orientedmodelofN2OandNOemissionsfromforestsoils:1.ModeldevelopmentJ.Geophys.Res.,105(D4):4369–4384.

Li,C.,J.Cui,G.Sun,andC.Trettin.2004.ModelingImpactsofManagementonCarbonSequestrationandTraceGasEmissionsinForestedWetlandEcosystems.EnvironmentalManagement,33:S176‐S186.

Lockaby,B.G.,C.Trettin,andS.Shoenholtz.1999.Effectsofsilviculturalactivitiesonwetlandbiogeochemistry.JEnvironQual,28:1687‐1698.

Lowrance,R.,J.M.Sheridan,R.G.Williams,D.D.Bosch,etal.2007.Waterqualityandhydrologyinfarm‐scalecoastalplainwatersheds:Effectsofagriculture,impoundments,andriparianzones.JournalofSoilandWaterConservation,62(2):65‐76.

Lu,S.Y.,P.Y.Zhang,andW.H.Cui.2010.Impactofplantharvestingonnitrogenandphosphorusremovalinconstructedwetlandstreatingagriculturalregionwastewater.InternationalJournalofEnvironmentandPollution,43(4):339‐353.

Maltais‐Landry,G.,R.Maranger,J.Brisson,andF.Chazarenc.2009.Greenhousegasproductionandefficiencyofplantedandartificiallyaeratedconstructedwetlands.EnvironmentalPollution,157(3):748‐754.

Mander,U.,K.Lohmus,S.Teiter,K.Nurk,etal.2005a.Gaseousfluxesfromsubsurfaceflowconstructedwetlandsforwastewatertreatment.JournalofEnvironmentalScienceandHealth‐PartAToxic/HazardousSubstancesandEnvironmentalEngineering,40(6‐7):1215‐1226.

Mander,U.,S.Teiter,andJ.Augustin.2005b.Emissionofgreenhousegasesfromconstructedwetlandsforwastewatertreatmentandfromriparianbufferzones.WaterScienceandTechnology,52(10‐11):167‐176.

Merbach,W.,T.Kalettka,C.Rudat,andJ.Augustin.2002.TracegasemissionsfromriparianareasofsmalleutrophicinlandwatersinNortheastGermany.InWetlandsinCentralEurope‐Soil


4-27

Organisms,SoilEcologicalProcessesandTraceGasEmissions,G.Broll,W.MerbachandE.‐M.Pfeiffer(eds.).Berlin,Germany:Springer‐Verlag.

Miehle,P.,S.J.Livesley,P.M.Feikema,C.Li,etal.2006.AssessingproductivityandcarbonsequestrationcapabilityofEucalyptusglobulusplantationsusingtheprocessmodelForest‐DNDC:Calibrationandvalidation.EcologicalModelling,192:83‐94.

Minkkinen,K.,andJ.Laine.1998.Long‐termeffectofforestdrainageonthepeatcarbonstoresofpinemiresinFinland.CanadianJournalofForestResearch,28(9):1267‐1275.

Modin,O.,K.Fukushi,andK.Yamamoto.2007.Denitrificationwithmethaneasexternalcarbonsource.WaterResearch,41(12):2726‐2738.

Montreuil,O.,P.Merot,andP.Marmonier.2010.Estimationofnitrateremovalbyriparianwetlandsandstreamsinagriculturalcatchments:effectofdischargeandstreamorder.FreshwaterBiology,55(11):2305‐2318.

Novak,J.M.,P.G.Hunt,K.C.Stone,D.W.Watts,etal.2002.RiparianzoneimpactonphosphorusmovementtoaCoastalPlainblackwaterstream.JournalofSoilandWaterConservation,57(3):127‐133.

Osaka,T.,Y.Ebie,S.Tsuneda,andY.Inamori.2008.Identificationofthebacterialcommunityinvolvedinmethane‐dependentdenitrificationinactivatedsludgeusingDNAstable‐isotopeprobing.FEMSMicrobiologyEcology,64(3):494‐506.

Pennock,D.,T.Yates,A.Bedard‐Haughn,K.Phipps,etal.2010.LandscapecontrolsonN2OandCH4emissionsfromfreshwatermineralsoilwetlandsoftheCanadianPrairiePotholeregion.Geoderma,155(3‐4):308‐319.

Peterjohn,W.T.,andD.L.Correll.1984.NutrientDynamicsinanAgriculturalWatershed:ObservationsontheRoleofaRiparianForest.Ecology,65(5):1466‐1475.

Phillips,R.,andO.Beeri.2008.Theroleofhydropedologicvegetationzonesingreenhousegasemissionsforagriculturalwetlandlandscapes.CATENA,72(3):386‐394.

Picek,T.,H.Čížková,andJ.Dušek.2007.Greenhousegasemissionsfromaconstructedwetland‐Plantsasimportantsourcesofcarbon.EcologicalEngineering,31(2):98‐106.

Poach,M.E.,P.G.Hunt,E.J.Sadler,T.A.Matheny,etal.2002.Ammoniavolatilizationfromconstructedwetlandsthattreatswinewastewater.TransactionsoftheAmericanSocietyofAgriculturalEngineers,45(3):619‐627.

Poach,M.E.,P.G.Hunt,G.B.Reddy,K.C.Stone,etal.2004.Ammoniavolatilizationfrommarsh‐pond‐marshconstructedwetlandstreatingswinewastewater.JournalofEnvironmentalQuality,33(3):844‐851.

Rafique,R.,D.Henessy,andG.Kiely.2011.Evaluatingmanagementeffectsonnitrousoxideemissionsfromgrasslandsusingtheprocess‐basedDeNitrificationDeComposition(DNDC)model.Atmospheric,Environment,45:6029‐6039.

Ranalli,A.J.,andD.L.Macalady.2010.Theimportanceoftheriparianzoneandin‐streamprocessesinnitrateattenuationinundisturbedandagriculturalwatersheds‐Areviewofthescientificliterature.JournalofHydrology,389(3‐4):406‐415.

Roobroeck,D.,K.Butterbach‐Bahl,N.Brüggemann,andP.Boeckx.2010.Dinitrogenandnitrousoxideexchangesfromanundrainedmonolithfen:short‐termresponsesfollowingnitrateaddition.EuropeanJournalofSoilScience,61(5):662‐670.

Rose,C.,andW.G.Crumpton.2006.SpatialPatternsinDisssolvedOxygenandMethaneConcentrationsinaPrairiePotholeWetlandinIowa,USA.Wetlands,26:1020‐1025.

Schoonover,J.,K.Williard,J.Zaczek,J.Mangun,etal.2005.NutrientAttenuationinAgriculturalSurfaceRunoffbyRiparianBufferZonesinSouthernIllinois,USA.AgroforestrySystems,64(2):169‐180.

Seo,D.C.,andR.D.DeLaune.2010.Fungalandbacterialmediateddenitrificationinwetlands:Influenceofsedimentredoxcondition.WaterResearch,44(8):2441‐2450.


4-28

Skaggs,R.W.,B.D.Phillips,G.M.Chescheir,andC.C.Trettin.2011.Effectofminordrainageonhydrologyofforestedwetlands.TransactionsoftheASABE,54(6):2139‐2149.

Smemo,K.A.,andJ.B.Yavitt.2006.AMulti‐yearPerspectiveonMethaneCyclinginaShallowPeatFeninCentralNewYorkState,USA.Wetlands,26:20‐29.

Smith,T.A.,D.L.Osmond,andJ.W.Gilliam.2006.Riparianbufferwidthandnitrateremovalinalagoon‐effluentirrigatedagriculturalarea.JournalofSoilandWaterConservation,61(5):273‐281.

Soosaar,K.,U.Mander,M.Maddison,A.Kanal,etal.2011.Dynamicsofgaseousnitrogenandcarbonfluxesinriparianalderforests.EcologicalEngineering,37:40‐53.

Stang,F.,K.Butterbach‐Bahl,andH.Papen.2000.Aprocess‐orientedmodelofN2OandNOemissionsfromforestsoils.2.Sensitivityanalysisandvalidation.J.Geophys.Res.,105:4385‐4398.

Stedman,S.,andT.E.Dahl.2008.StatusandtrendsofwetlandsinthecoastalwatershedsoftheEasternUnitedStates1998to2004:NationalOceanicandAtmosphericAdministration,NationalMarineFisheriesServiceandU.S.DepartmentoftheInterior,FishandWildlifeService.

Stein,O.R.,andP.B.Hook.2005.Temperature,plants,andoxygen:Howdoesseasonaffectconstructedwetlandperformance?JournalofEnvironmentalScienceandHealth‐PartAToxic/HazardousSubstancesandEnvironmentalEngineering,40(6‐7):1331‐1342.

Stein,O.R.,J.A.Biederman,P.B.Hook,andW.C.Allen.2006.Plantspeciesandtemperatureeffectsonthek‐C*first‐ordermodelforCODremovalinbatch‐loadedSSFwetlands.EcologicalEngineering,26(2):100‐112.

Stein,O.R.,B.W.Towler,P.B.Hook,andJ.A.Biederman.2007.Onfittingthek‐C*firstordermodeltobatchloadedsub‐surfacetreatmentwetlands.WaterScienceandTechnology,56(3):93‐99.

Stone,K.C.,P.G.Hunt,F.J.Humenik,andM.H.Johnson.1998.Impactofswinewasteapplicationongroundandstreamwaterqualityinaneasterncoastalplainwatershed.TransactionsoftheAmericanSocietyofAgriculturalEngineers,41:1665‐1670.

Stone,K.C.,P.G.Hunt,A.A.Szogi,F.J.Humenik,etal.2002.Constructedwetlanddesignandperformanceforswinelagoonwastewatertreatment.TransactionsoftheAmericanSocietyofAgriculturalEngineers,45(3):723‐730.

Stone,K.C.,M.E.Poach,P.G.Hunt,andG.B.Reddy.2004.Marsh‐pond‐marshconstructedwetlanddesignanalysisforswinelagoonwastewatertreatment.EcologicalEngineering,23(2):127‐133.

Tabacchi,E.,D.L.Correll,R.Hauer,G.Pinay,etal.1998.Development,maintenanceandroleofriparianvegetationintheriverlandscape.FreshwaterBiology,40(3):497‐516.

Tanner,C.C.,D.D.Adams,andM.T.Downes.1997.Methaneemissionsfromconstructedwetlandstreatingagriculturalwastewaters.JournalofEnvironmentalQuality,26(4):1056‐1062.

Tanner,C.C.,andT.R.Headley.2011.Componentsoffloatingemergentmacrophytetreatmentwetlandsinfluencingremovalofstormwaterpollutants.EcologicalEngineering,37(3):474‐486.

Taylor,C.R.,P.B.Hook,O.R.Stein,andC.A.Zabinski.2010.Seasonaleffectsof19plantspeciesonCODremovalinsubsurfacetreatmentwetlandmicrocosms.EcologicalEngineering.

Teiter,S.,andU.Mander.2005.EmissionofN2O,N2,CH4,andCO2fromconstructedwetlandsforwastewatertreatmentandfromriparianbufferzones.EcologicalEngineering,25(5):528‐541.

Thornton,F.C.,andR.J.Valente.1996.Soilemissionsofnitricoxideandnitrousoxidefromno‐tillcorn.SoilScienceSocietyofAmericaJournal,60:1127‐1133.

Towler,B.W.,J.E.Cahoon,andO.R.Stein.2004.Evapotranspirationcropcoefficientsforcattailandbulrush.JournalofHydrologicEngineering,9(3):235‐239.


4-29

Trettin,C.,M.F.Jurgensen,M.R.Gale,andJ.W.McLaughlin.1995.Soilcarboninnorthernforestedwetlands:impactsofsilviculturalpractices.InCarbonFormsandFunctions,W.W.McFeeandJ.M.Kelly(eds.).Madison,WI:SoilScienceSocietyofAmerica.

Trettin,C.C.,B.Song,M.F.Jurgensen,andC.Li.2001.Existingsoilcarbonmodelsdonotapplytoforestedwetlands,Gen.Tech.Rep.SRS‐46.Asheville,NC:U.S.DepartmentofAgriculture,ForestService,SouthernResearchStation.

Trettin,C.C.,andM.F.Jurgensen.2003.Carboncyclinginwetlandforestsoils.InThepotentialofU.S.forestsoilstosequestercarbonandmitigatethegreenhouseeffect,J.M.Kimble,L.S.Heath,R.A.BirdseyandR.Lal(eds.).BocaRaton,FL:CRCPressLLC.

Trettin,C.C.,R.Laiho,K.Minkkinnen,andJ.Laine.2006.Influenceofclimatechangefactorsoncarbondynamicsinnorthernforestedpeatlands.CanadianJournalofSoilScience,86:269‐280.

U.S.EPA.2011.InventoryofU.S.GreenhouseGasEmissionsandSinks:1990‐2009.Washington,D.C.:U.S.EnvironmentalProtectionAgency.http://epa.gov/climatechange/emissions/usinventoryreport.html.

VanDerKamp,G.,W.J.Stolte,andR.G.Clark.1999.Dryingoutofsmallprairiewetlandsafterconversionoftheircatchmentsfromcultivationtopermanentbromegrass.HydrologicalSciencesJournal,44(3):387‐397.

vanderKamp,G.,M.Hayashi,andD.Gallén.2003.ComparingthehydrologyofgrassedandcultivatedcatchmentsinthesemiaridCanadianprairies.HydrologicalProcesses,17:559‐575.

Vellidis,G.,R.Lowrance,P.Gay,andR.K.Hubbard.2003.Nutrienttransportinarestoredriparianwetland.JEnvironQual,32(2):711‐726.

Verchot,L.,T.Krug,R.D.Lasco,S.Ogle,etal.2006.Chapter5:Grassland.In2006IPCCGuidelinesforNationalGreenhouseGasInventories,S.Eggleston,L.Buendia,K.Miwa,T.NgaraandD.L.Tanaka(eds.).Japan:IGES.

Voldseth,R.A.,W.C.Johnson,T.Gilmanov,G.R.Guntenspergen,etal.2007.Modelestimationofland‐useeffectsonwaterlevelsofnorthernprairiewetlands.EcolAppl,17(2):527‐540.

Wang,Y.,R.Inamori,H.Kong,K.Xu,etal.2008.Influenceofplantspeciesandwastewaterstrengthonconstructedwetlandmethaneemissionsandassociatedmicrobialpopulations.EcologicalEngineering,32(1):22‐29.

Whalen,S.C.2005.BiogeochemistryofMethaneExchangebetweenNaturalWetlandsandtheAtmosphere.EnvironmentalEngineeringScience,22(1):73‐94.

Winter,T.C.,J.W.Harvey,andO.L.Franke.1998.Groundwaterandsurfacewater:asingleresource:U.S.GeologicalSurvey.

Woodward,K.B.,C.S.Fellows,C.L.Conway,andH.M.Hunter.2009.Nitrateremoval,denitrificationandnitrousoxideproductionintheriparianzoneofanephemeralstream.SoilBiologyandBiochemistry,41(4):671‐680.

Wu,J.,J.Zhang,W.L.Jia,H.J.Xie,etal.2009.Nitrousoxidefluxesofconstructedwetlandstotreatsewagewastewater.HuanjingKexue/EnvironmentalScience,30(11):3146‐3151.

Young,E.O.,andR.D.Briggs.2008.Phosphorusconcentrationsinsoilandsubsurfacewater:afieldstudyamongcroplandandriparianbuffers.JEnvironQual,37(1):69‐78.

Zhang,Y.,C.Li,C.C.Trettin,andG.Sun.2002.Anintegratedmodelofsoil,hydrologyandvegetationforcarbondynamicsinwetlandecosystems.GlobalBiogeochemicalCycles,16:1‐17.

Zhu,G.,M.S.M.Jetten,P.Kuschk,K.F.Ettwig,etal.2010.Potentialrolesofanaerobicammoniumandmethaneoxidationinthenitrogencycleofwetlandecosystems.AppliedMicrobiologyandBiotechnology,86(4):1043‐1055.

Zhu,N.,P.An,B.Krishnakumar,L.Zhao,etal.2007.Effectofplantharvestonmethaneemissionfromtwoconstructedwetlandsdesignedforthetreatmentofwastewater.JournalofEnvironmentalManagement,85(4):936‐943.


4-30

Thispageisintentionallyleftblank.

Chapter 4 Quantifying Greenhouse Gas Sources and Sinks in … · 2014-10-31 · Greenhouse Gas...

Documents

Transcript of Chapter 4 Quantifying Greenhouse Gas Sources and Sinks in … · 2014-10-31 · Greenhouse Gas...