Dean, Christopher

Harper, R. J.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress A Scientific Framework for Forecasting Carbon Sequestration in Rangelands Christopher Dean Forest Products Commission, Australia R. J. Harper Forest Products Commission, Australia Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/21/8-1/10 The 21st International Grassland Congress / 8th International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. 瞯]878　　瞯　MultifunctionalGrasslandsinaChangingWorld　VolumeⅠ　Grasslands/Ran gelandsResourcesandEcolo gy———ClimateChangeandImpactonGrasslands/Ran gelandsAscientificframeworkforforecastingcarbonsequestrationinrangelandsCDeanandRJHarperForestProductsCommission,117GreatEasternHi ghway,Rivervale,WA6103,Australia,E‐mail:christopher.dean＠fpc.wa. gov.auIntroductionTheuncertainty(higherformorearidareas)oftheworthofrangelandsforcarbonsequestration(CS)canbedeterminedfromthevastrangeofexistingandseeminglyconflictingscientificworkbyidentifyingandassemblingthebasiccomponentstoformpragmaticandcomprehensiveCSforecasting.Forthelast５０,０００yearspeoplehaveburnedorclearedforestsandwoodlandstofavourlargeherbivores,andmorerecentlytoproducefood,lumber,urbanisation,paperandvehiclefuel.Theneteffectofaerobicallydecomposingwoodymatter(e.g.cellulose),whetherviadirectcombustion,burningoffossilfuelsoroxidationofsoilcarbonfollowingerosionis,inchemicalterms,thereaction:(n(C ６H１０O５))　＋　６nO２　６nCO２↑＋５nH２O＋energy.Vegetation‐basedCSprojectsaimtoameliorateourcarbon‐fluximbalanceusing１)thereverseoftheaboveequation(viaphotosynthesis),and２)storageofvegetationdecayproductsassoilcarbon.Also,existingforestsandwoodlandspersehaverecentlygainedmorerecognitionasidealcarbonstores.WeexaminethepotentialforCSinthe３.８４Mkm２occupiedbytherangelandgrazingindustryinAustralia—predominantlyshrublandandwoodland—i.e.agoodcandidateforlong‐termcarbonstorage.Landdegradation(e.g.severeerosion,woodythickening,andaccentuationofdroughteffects)hasfollowedoveruseandclearingbytheadvancinglivestockindustryforoveracentury.Italsocausesincreasedcarbonemissionsanddecreasedbiodiversity(e.g.WalkerandSteffen,１９９３),andanimalwelfarelegislationisinapplicable.GleesonandDalley(２００６)noticedgenerallyafocusonshort‐termproductivitygoals,oppositiontoenvironmentalconcerns,bureaucraticstagnationandpaltryadjustments.Theeconomicsofclimatechangemayprovideimpetusforchange,e.g.viatheKyotoProtocolwhichallowsforemissionstobeoffsetbytrading.MaterialsandmethodsThispaperrepresentsapreviewofascientificliteraturereviewplusexcerptsfromfieldwork,andanalysesofexistingandnewdatasetsincludingremotesensingandGISmethods—tobepublishedseparately.Theeventsconstitutingcarbonemissionandsequestrationcanbesimulatedusingsuperimposedsigmoidalcurves,commoninecologicalstudies.ProcessingtemporalLANDSATimageryforvegetativecoveryieldstheexpanseandmagnitudeofdegradation.ThedegradationGISlayercombinedwithlayersofbiomassandsoilcarbonpermitsassignmentofsigmoidalcurvesforeachpixelfromwhichregionalforecastsaretallied.Uncertaintiesinmeasurementarisefromunmeasuredhydrologicalcarbonandtheneedfor３Dbiomassdata(e.g.fromLIDARorradar).ResultsSomecriticalrequisitesforunequivocalresultswerefoundtobe:allowbetween３０and５００yrsinsemi‐aridandaridareasformeasurablechangesinC;useenvironmentallyandedaphicallypairedsites;accommodatehighspatialvariabilityinsoilorganiccarbon(SOC)—positivelycorrelatedwithwoodybiomass;recordshrub/treedeclineandforestryactivities;measureSOCtoatleastrootdepth—deeperincoarsersoilsanddryerareas;andnotably:percentagechangesincarbonstockselucidatephenomenaratherthancomparisonofabsolutevalues.EstimatedCemissionratesresultingfromcurrentmanagementare４to６０Mt‐C.yr‐１andforSOC:０.７％.yr‐１‐similarinmagnitudetothoseoverseas.EstimatesofCSforwoodythickeningareintheorderof０.４t‐C.ha‐１.yr‐１butitsextentremainsundetermined.Exclusionoflivestockcanincreasecarbonstocksseveralfoldindegradedareas,estimatesforCSupondestockingrangefrom４to２５Mt‐C.yr‐１.WeestimateCSat～１％.yr‐１,i.e.６Mt‐C.yr‐１,or～３００Mt‐Cover５０yrs.ThisvalueishalvediftheChicagoClimateExchangelimitofareaswithmorethan３５６mmrainfallisimposed.AnuncertainprognosisforCSarisessignificantlyfrom:１)invadingbuffelgrass(Cenchrusciliaris)whichcandehydrateshrubsandincreaseburning,２ )climatechangewithincreasedscarcityandintensityofrainfall—inducingmorefiresanderosion,and３) populationgrowth.ConclusionsThepotentialCSof～３００Mt‐Cupondestockingisnotlargecomparedwithourglobalcarbon‐fluximbalancebuttherearecorollarybenefitssuchashaltingthecurrentrangelandemissions.Uncertaintiesremainattwolevels:１ )precisionoftheCSvalues,and２)achievingtheCSbyachangeinmanagementparadigm.ReferencesGleeson,T.,andDalley,A.(２００６),�Land �.Themecommentary.Preparedforthe２００６AustraliaStateoftheEnvironmentCommittee,DepartmentofEnvironmentandHeritage,Canberra.＜http://www.deh.gov.au/soe/２００６/commentaries/land/index.html＞Walker,B.H.andSteffen,W.L.(１９９３)�RangelandsandGlobalChange",TheRangelandJournal,１５(１ ),９５‐１０３.1 

A Scientific Framework for Forecasting Carbon Sequestration in Rangelands

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A Scientific Framework for Forecasting Carbon Sequestration in Rangelands

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