#(!04%2
3OIL#ARBON!CCOUNTINGAND!SSUMPTIONSFOR&ORESTRYAND
&OREST2ELATED,AND5SE#HANGE
,INDA3(EATH53$!&OREST3ERVICE.ORTHEASTERN2ESEARCH3TATION
*AMES%3MITH53$!&OREST3ERVICE0ACIlC.ORTHWEST2ESEARCH3TATION
)NTRODUCTION
#OMPREHENSIVELARGESCALECARBONACCOUNTINGSYSTEMS
ARENEEDEDASNATIONSAGREETOWORKTOWARDREDUCINGTHEIR
GREENHOUSE GAS '(' EMISSIONS (OWEVER ADOPTING A
STANDARD ACCOUNTING SYSTEM IS DIFlCULT BECAUSE MULTIPLE
SCIENCE AND POLICY USES FOR SUCH A SYSTEM HELP FUEL THE
DEBATEABOUTTHENATUREOFANAPPROPRIATESYSTEM!CCOUNT
ING SYSTEMS MUST ADDRESS ALL MAJOR SOURCES AND SINKS OF
'('SORMOREPRAGMATICALLYFOCUSONSUBSETSOFIMPOR
TANTSOURCESANDSINKSANDFEATURETRANSPARENTFUNDAMEN
TALRULESTHATMAYBEADOPTEDEASILYBYALLNATIONS(ERE
WE REVIEW SOME ISSUES IN CARBON ACCOUNTING OF A MAJOR
'('SINKFORESTSOILSATANATIONALSCALE3PECIlCALLYWE
CONCENTRATEONHOWLANDUSECHANGEANDHARVESTINGAFFECT
FORESTSOILCARBONANDHOWTHOSEEFFECTSMAYBEDESCRIBED
CLEARLYINANACCOUNTINGSYSTEMTHATISEASYTOUSE
/RGANIC CARBON IN SOIL BELOW THE FOREST mOOR IS ONE
COMPONENT OF FOREST CARBON THAT IS PARTICULARLY CONTEN
TIOUS -EASURING SOIL CARBON IS TIMECONSUMING COSTLY
AND OPERATIONALLY DIFlCULT PARTLY BECAUSE VARIABILITY IN
SOILS TENDS TO BE HIGH REQUIRING MANY SAMPLES TO STA
TISTICALLY TEST RESULTS 2ELATIONSHIPS BETWEEN EASILY CHAR
ACTERIZEDABOVEGROUNDVEGETATIONANDBELOWGROUNDSOIL
CARBONMAYBEWEAKBECAUSESOILCARBONMAYHAVEBEEN
AFFECTEDBYPASTLANDUSELONGAFTERVISUALTRACESOFTHE
PREVIOUSUSEDISAPPEAR(OWEVERCARBONPOOLSIZEALONE
MAKESFORESTSOILSQUITEIMPORTANTDESPITETHEUNCERTAIN
TIES%)!53%0!3OILSOFTHEWORLDAREESTI
MATED TO CONTAIN TWICE THE AMOUNT OF CARBON AS IN THE
ATMOSPHEREORVEGETATION"OUWMAN
4HE ACCOUNTING FRAMEWORKS DESCRIBED IN THE GLOBAL
GUIDELINES FOR NATIONAL GREENHOUSE GAS INVENTORIES
RELEASED BY THE )NTERGOVERNMENTAL 0ANEL ON #LIMATE
#HANGE)0##/%#$)%!REVISEDININCREAS
INGLY DISCUSS SOIL CARBON THEREBY REmECTING THE IMPOR
TANCEOFACCOUNTINGFORCARBONINSOIL)NTHE5NITED3TATES
"IRDSEY AND (EATH PRESENTED FOREST CARBON ESTI
MATES INCLUDING SOIL CARBON IN A TECHNICAL DOCUMENT
*OYCE ACCOMPANYING A LARGER ASSESSMENT FRAME
WORK THE 53$! &OREST 3ERVICE ANALYSIS FOR THE &OREST
AND2ANGELAND2ENEWABLE2ESOURCES0LANNING!CT20!
!SSESSMENT 53$!&3 4HESE ACCOUNTING SYSTEMS
FEATURE TWO MAIN COMPONENTS INPUT MEASURES OR SAM
PLES TO CHARACTERIZE FORESTS AND A CORE OF ASSUMED RELA
TIONSHIPSTOESTIMATETHEAMOUNTOFCARBONINTHATFOREST
53$!&OREST3ERVICE'EN4ECH2EP2-23n'42n
#ARBONISGENERALLYDESCRIBEDASAFUNCTIONOFFORESTAGE
AREAVOLUMEORBIOMASS
)N THIS CHAPTER WE DISCUSS THE ACCOUNTING SYSTEM BY
"IRDSEYAND(EATHUSEDBYTHE20!ANDTHEACCOUNT
INGSYSTEMOFTHE)0##.ATIONAL'REENHOUSE'AS)NVEN
TORIES FOR SOIL CARBON IN THE FOREST SECTOR AND LAND
USECHANGESINVOLVINGFORESTS"ASICASSUMPTIONSARECOM
PAREDINLIGHTOFNEWSCIENTIlCSTUDIESONFORESTSOILCARBON
7EOUTLINEIMPORTANTCOMPONENTSINTHEACCOUNTINGFRAME
WORKS WITH AN EMPHASIS ON LAND USE CHANGE ACTIVITIES
SUCHASAFFORESTATIONDEFORESTATIONANDREFORESTATION7E
THENREVIEWRECENTSCIENTIlCDEVELOPMENTSTHATAFFECTSOIL
CARBONASSUMPTIONSUSEDTOCALCULATECARBONESTIMATES
&OREST#ARBON!CCOUNTING
7EUSETHEPHRASEhSOILCARBONvTOMEANSOILORGANIC
CARBONINHORIZONSBENEATHANDNOTINCLUDINGTHEFOREST
mOOR5SUALLYSOILBENEATHTHEFORESTmOORISCALLEDMIN
ERALSOIL3OMESOILSDEVELOPINGUNDERAWATERLOGGEDCON
DITION MAY CONTAIN A HIGH LEVEL OF ORGANIC MATTER AND
THESESOILSARECALLEDORGANICSOILSOR(ISTOSOLS4HUSWE
CANDIFFERENTIATEBETWEENSOILORGANICCARBONINMINERAL
SOILSANDSOILORGANICCARBONINORGANICSOILS3OMESOILS
ALSOCONTAINAGREATDEALOFCARBONININORGANICFORMSUCH
AS CARBONATES (OWEVER INORGANIC CARBON IS RELATIVELY
INERTANDTHEREFOREWEDONOTINCLUDEITINTHISSTUDY
#ARBONACCOUNTINGQUICKLYBECOMESCOMPLICATEDINPRAC
TICEBECAUSEWEAREMOSTINTERESTEDINCARBONmUXWHICH
MAY BE CALCULATED AS CHANGE IN SUCCESSIVE CARBON STOCKS
INVENTORIES!TTHESIMPLESTLEVELTWOVARIABLESARENEEDED
TOCALCULATENETCARBONmUXINFORESTSAREAANDTOTALCARBON
PERAREA-ULTIPLYINGAREAANDCARBONPERAREAYIELDSTOTAL
CARBONINVENTORYSTOREDINFORESTS.ETCARBONmUXISTHEN
ESTIMATEDBYTHEDIFFERENCEINTOTALCARBONESTIMATEDATTWO
CONSECUTIVE TIMES DIVIDED BY THE LENGTH OF TIME BETWEEN
INVENTORIES (OWEVER THERE ARE A NUMBER OF METHODS TO
MODEL CARBON INVENTORY AND mUX 4HE METHODS VARY BY
DATAREQUIREMENTSSYSTEMDElNITIONBOUNDARYCONDITIONS
ANDEVENIDENTITYOFCARBONPOOLS4HETWOMETHODSWEDIS
CUSSFOCUSPRINCIPALLYONESTIMATINGSTOCKSOFCARBONAND
mUXISSIMPLYTHEANNUALDIFFERENCEINSTOCKS
$ATA AND INFORMATION ISSUES MAKE FOREST CARBON AC
COUNTING PARTICULARLY DIFlCULT )DEALLY A COMPREHENSIVE
(EATHAND3MITH
3OIL#ARBON!CCOUNTINGAND!SSUMPTIONSFOR&ORESTRYAND&OREST2ELATED,AND5SE#HANGE
ACCOUNTINGSYSTEMWOULDPROVIDETHEBESTESTIMATESFOR
'('EMISSIONSASSOCIATEDWITHFORESTS!COMPREHENSIVE
SYSTEMWOULDINCLUDETHESECOMPONENTSATTHEBEGINNING
OFEACHYEARLIVINGANDDEADTREEBIOMASSCARBONCARBON
INSEEDLINGSUNDERSTORYFORESTmOORROOTANDSOILCARBON
.ONATIONMEASURESALLTHESECOMPONENTSALTHOUGHSOME
NATIONSDOMEASUREMANYITEMSSTRONGLYRELATEDTOTHESE
COMPONENTS &URTHER SCIENTISTS DO NOT AGREE ON GEN
ERALIZED ASSUMPTIONS THAT MAY BE USED AS A WAY TO
CONVERT MEASURED DATA SUCH AS AREA AND VOLUMES TO
CARBON 7ITHOUT SCIENTIlC CONSENSUS ON ASSUMPTIONS
SOMENATIONSMAYPREFERTOEXCLUDEINCOMPLETEINFORMA
TIONWHILEOTHERNATIONSMAYHAVEADEQUATEINFORMATION
.O MATTER HOW DETAILED THE INFORMATION THE GOAL IS TO
DEVELOPESTIMATESOFTHEAREAOFFORESTANDCARBONPERUNIT
AREA
4HECOMPARISONOFTHETWOACCOUNTINGMETHODSDOES
NOTINCLUDEAQUANTITATIVEESTIMATEFORMEDUSINGTHE)0##
METHOD!SUMMARYOF53CARBONTOTALSFROMPREVIOUS
ESTIMATES IS INCLUDED HERE TO PROVIDE SOME PERSPECTIVE
ONTHEMAGNITUDESINVOLVED&ORESTSINTHECONTERMINOUS
5NITED 3TATES WERE ESTIMATED TO CONTAIN ABOUT BIL
LIONMETRICTONSOFCARBONINSEQUESTERINGMIL
LIONMETRICTONSPERYEARINSOILSANDFORESTmOORAND
MILLIONMETRICTONSPERYEARINLIVEVEGETATIONSEETABLE
"IRDSEYAND(EATH4HESERESULTSINCLUDEDESTI
MATESOFFORESTSOFVERYLOWPRODUCTIVITYWHICHTENDTO
BE LOCATED IN ARID OR MOUNTAINOUS REGIONS AND ARE FOR
THEMOSTPARTNOTMANAGEDCOMMERCIALLYFORTIMBER0RO
DUCTIVEFORESTLANDAVAILABLEFORHARVESTISCALLEDTIMBER
LAND#ARBONESTIMATESINFORTIMBERLANDINCLUDING
TIMBERLANDIN!LASKAAREBILLIONMETRICTONSSEQUES
TERINGMILLIONMETRICTONSPERYEARINSOILSANDFOREST
mOOR AND MILLION METRIC TONS PER YEAR IN LIVE VEGE
TATION SEE TABLE "IRDSEY AND (EATH 4HE TWO
TABLESARENOTSTRICTLYCOMPARABLEBECAUSEOFDElNITIONAL
CHANGESOVERTIME&ORINSTANCETHECARBONESTIMATESON
TIMBERLAND DURING THE PERIOD n ARE NOTICEABLY
AFFECTED BY #ONGRESSIONAL DESIGNATION OF SOME TIMBER
LANDAS7ILDERNESSˆANEXAMPLEOFHOWLANDUSECHANGE
CANAFFECTAPPARENTCARBONBUDGETS
3OIL#ARBON!CCOUNTING3YSTEMS
&OR&ORESTAND,AND5SE#HANGE
! COMPARISON OF TWO CARBON ACCOUNTING METHODS
DESIGNED FOR NATIONALLEVEL TOTALS CAN USEFULLY ILLUSTRATE
SOMEOFTHELINKSAMONGTHESTATEOFSCIENTIlCUNDERSTAND
ING MODEL ASSUMPTIONS AND ASSESSMENT PRIORITIES 4HE
lRSTMETHODWASDEVELOPEDTOESTIMATETOTALCARBONINVEN
TORY OF 53 FORESTS WITH EMPHASIS ON CHANGE IN STORAGE
BROUGHTABOUTBYGROWTHANDMANAGEMENTACTIVITIES4HE
SECONDMETHODISFROMANINTERNATIONALEFFORTDESIGNEDTO
BEGENERALLYAPPLICABLE)TISFOCUSEDONDETERMININGFOREST
'('EMISSIONSINDUCEDBYHUMANACTIVITIES
4HETWOMETHODSARENOTSIMPLYALTERNATEAPPROACHES
TO ESTIMATING THE SAME VALUES BUT THERE ARE SOME PAR
ALLELSINASSUMPTIONSANDGOALS#OMPARISONSAREESSEN
TIALLYQUALITATIVEOVERVIEWSOFTHECONCEPTUALORGANIZATION
OF THE TWO METHODS 7E EMPHASIZE ASSUMPTIONS AND
APPROACHESTOMODELINGLANDUSECHANGEESPECIALLYAFFOR
ESTATION DEFORESTATION AND REFORESTATION !LTHOUGH THE
FOCUSOFOURSTUDYISONSOILORGANICCARBONWEALSODIS
CUSSCARBONINOTHERCOMPONENTSOFFORESTSBECAUSEOFTEN
THESOILCARBONINFORMATIONINEXTRICABLYDEPENDSONOTHER
FORESTCOMPONENTS
#ARBON%STIMATES5SEDBYTHE20!
!SSESSMENT
4HECARBONACCOUNTINGMETHODOF"IRDSEYAND(EATH
WASUSEDFORTHE20!ASSESSMENTANDINCLUDED
COMPREHENSIVEESTIMATESFORCARBONINALLCOMPONENTSOF
53 FORESTS 4HESE WERE DEVELOPED SPECIlCALLY FOR 53
FORESTLAND AND DESIGNED TO UTILIZE THE EXTENSIVE BASE OF
FORESTINFORMATIONINTHISCOUNTRY7ElRSTDISCUSSSOME
BASIC ASSUMPTIONS OF THE METHOD AND WE THEN DISCUSS
ACCOUNTINGFOREFFECTSOFCHANGESINLANDUSE
4HE ESTIMATES WERE BASED ON FOREST INVENTORIES CON
DUCTEDBYTHE53$!&OREST3ERVICE&OREST)NVENTORYAND
!NALYSIS0ROGRAM(ANSENETAL7OUDENBERGAND
&ARRENKOPF 4HE INVENTORY SURVEY AND ASSOCIATED
SAMPLINGERRORSAREDESIGNEDFORMEASURINGTOTALTIMBER
VOLUME OVER AN AGGREGATED FOREST AREA &OREST AREAS ARE
ESTIMATEDBECAUSETHEYARENEEDEDTOCALCULATEVOLUMES
BUTTHEDESIGNOFTHESURVEYDOESNOTREQUIREDESIGNATING
SAMPLINGERRORSFORAREAORSOILCARBON!SARESULTFOREST
INVENTORY DATA PROVIDE GOOD ABOVETHESTUMP INFORMA
TIONYETAREALSOUSEFULFORDERIVINGBELOWGROUNDINFOR
MATIONCALCULATEDASASSUMEDFUNCTIONSOFCOLLECTEDDATA
4HEINVENTORYDOESNOTDIRECTLYMEASURESOILCARBON
4HECARBONMODELISBASEDONAGGREGATIONSOFFORESTS
WITHIN EACH OF NINE REGIONS OF THE 5NITED 3TATES %ACH
AGGREGATION IS CALLED A MANAGEMENT UNIT &OREST TYPE
OWNERSHIP AND SOMETIMES PRODUCTIVITY AND PREVIOUS
LAND USE DELINEATE EACH MANAGEMENT UNIT 4HE FOREST
INVENTORYFOREACHMANAGEMENTUNITINCLUDESNUMBEROF
HECTARES AND AVERAGE VOLUME BY AGE CLASS 3OIL CARBON
PERHECTAREISESTIMATEDFORMANAGEMENTUNITSACCORDING
TO EMPIRICAL RELATIONSHIPS SPECIlC TO MANAGEMENT UNIT
CHARACTERISTICS"IRDSEY0LANTINGAAND"IRDSEY
3IMILAR ESTIMATION PROCEDURES ARE ALSO ESTABLISHED FOR
OTHERFORESTCARBONPOOLSINCLUDINGCARBONINTREES.ET
ANNUALSOILCARBONmUXISCALCULATEDBYMULTIPLYINGHECT
ARES OF FOREST BY CARBON PER HECTARE IN EACH OF TWO CON
53$!&OREST3ERVICE'EN4ECH2EP2-23n'42n
3OIL#ARBON!CCOUNTINGAND!SSUMPTIONSFOR&ORESTRYAND&OREST2ELATED,AND5SE#HANGE
SECUTIVEINVENTORIESANDDIVIDINGTHEDIFFERENCEBYLENGTH
OFTHEPERIOD
4HENUMBEROFHECTARESOFFORESTINVENTORYMAYCHANGE
ASLANDUSECHANGESBETWEENFORESTANDNONFORESTVEGE
TATION3UCHAREACHANGEINmUENCESONmUXAREALLOWEDIN
THISMETHODTOPROVIDEANACCURATEACCOUNTINGOFCARBON
INTHEFORESTSECTOR)FLANDWASTRANSFERREDINTOTHEAGRI
CULTURALSECTORFROMTHEFORESTSECTORTHENITISASSUMEDTHE
ADDITIONALHECTARESAREACCOUNTEDFORINAGRICULTURE4HIS
APPARENT LOSS OF FOREST SOIL CARBON TO THE ATMOSPHERE IS
REALLYONLYATRANSFERTOADIFFERENTSECTOR3IMILARLYIFFOR
ESTEDAREAINCREASEDDURINGTHEINTERVALTHISACCOUNTING
METHOD PRODUCES AN EFFECT OF ADDITIONAL CARBON SEQUES
TRATIONFROMTHEATMOSPHERE)NTHEANDPRIORINVEN
TORY ESTIMATES AREAS ARE BASED ON HISTORICAL ESTIMATES
FROMFORESTINVENTORIESINTHEPROJECTEDYEARSAREASARE
BASEDONLANDUSEPROJECTIONS!LIGETALUSEDINTHE
20!4IMBER!SSESSMENT(AYNESETAL
(EATHAND3MITH
&IGUREˆ'ENERALIZEDTRAJECTORYOFFORESTMINERALSOILORGANIC
CARBON FOLLOWING CLEARCUT HARVEST!DAPTED FROM -OORE ET AL
20!!CCOUNTING3YSTEMAND,AND5SE
#HANGE
!SSUMPTIONS ABOUT THE DYNAMICS OF SOIL CARBON OVER
TIME ARE DISCUSSED IN 0LANTINGA AND "IRDSEY AND
"IRDSEYTHESEINCLUDEEFFECTSOFBOTHPREVIOUSLAND
USEANDHARVESTING)NITIALSOILCARBONESTIMATESFORFORESTS
DEVELOPINGONCROPLANDANDPASTUREnTHATISTHELANDUSEIS
CHANGINGFROMCROPLANDORPASTURETOFORESTnWEREDERIVED
FROMREGRESSIONEQUATIONSFORSOILORGANICCARBONIN"URKE
ETAL2EGIONALESTIMATESWEREBASEDONMEANANNUAL
TEMPERATUREANDMEANANNUALPRECIPITATIONFOREACHOFTHE
REGIONS ASSUMING PERCENT CLAY AND SILT WERE EQUAL TO PERCENTANDPERCENT"IRDSEYDEVELOPEDACOM
PARABLEREGRESSIONEQUATIONFORFORESTLANDWITHTHERESULTS
EQUALTOSOILORGANICCARBONOFMATUREFORESTSWHICHWAS
ASSUMEDTOOCCURATAGEINTHE3OUTHANDATAGEIN
OTHERREGIONS7ITHTHESETHREEBASESOILCARBONESTIMATES
THATISFORESTORIGINATINGONCROPLANDPASTUREORFOREST
LAND DEVELOPED BY REGION THE DYNAMICS OF SOIL CARBON
WITH FOREST GROWTH WERE FUNCTIONS OF PREVIOUS LAND USE
ANDTIME&ORESTSREGENERATEDONPASTUREWEREASSUMEDTO
STARTATFORESTSTANDAGEWITHSOILCARBONCHARACTERISTIC
OFPASTUREANDTHENINCREASELINEARLYASFORESTSAGEDTOTHE
AMOUNTOFSOILCARBONFOUNDINMATUREFORESTSTANDSOFTHAT
REGION3OILCARBONOFFORESTSREGENERATEDONCROPLANDWAS
ESTIMATEDSIMILARLY!FTERCLEARCUTHARVESTATFORESTSTAND
AGESOILCARBONISASSUMEDTOEQUALTHECALCULATEDBASE
CARBONESTIMATEDECLINEUPTOPERCENT7OODWELLETAL
0ASTORAND0OSTOVERAnYEARPERIODFOL
LOWINGHARVESTANDACCUMULATEGRADUALLYTOABASEFOREST
CARBONBYMATURITYAPPROXIMATELYYEARS4HESEQUALI
TATIVETRENDSINSOILCARBONAREILLUSTRATEDINlGURESAND
FORACLEARCUTWITHREFORESTATIONANDHARVESTWITHANON
FORESTINTERVALBEFOREREGENERATIONRESPECTIVELY
53$!&OREST3ERVICE'EN4ECH2EP2-23n'42n
&IGUREˆ'ENERALIZEDTRAJECTORYOFFORESTMINERALSOILORGANIC
CARBONAFTERCLEARINGCULTIVATIONANDFORESTREGENERATIONFOLLOW
INGABANDONMENT!DAPTEDFROM-OOREETAL
-ANAGEMENT UNITS ARE NOT PARTITIONED INTO AREAS OF
PREVIOUSLANDUSESOWECANNOTSIMPLYADOPTSOILCARBON
ESTIMATESFORFORESTSORIGINATINGONCROPLANDPASTUREOR
FORESTLAND 7E CURRENTLY HAVE ONLY GENERAL ESTIMATES OF
PREVIOUS LAND USE OVER AN AGGREGATED AREA 4HEREFORE
WEIGHTEDAVERAGESOFSOILCARBONWERECALCULATEDBASED
ON PERCENTAGES OF PREVIOUS LAND USE ON WHICH CURRENT
FOREST WERE REGENERATED 4HESE PERCENTAGES WERE ESTI
MATEDUSINGVARIOUS53$!&OREST3ERVICEINVENTORYSTA
TISTICS COUPLED WITH ASSUMPTIONS ABOUT MANAGEMENT
OWNERSHIP AND REGIONAL INmUENCES "IRDSEY PERSONAL
COMMUNICATION )T WAS THE WEIGHTED SOIL CARBON EQUA
TIONSTHATWEREUSEDINTHEANALYSIS
4HEEFFECTOFTHEWEIGHTINGPROCEDUREISILLUSTRATEDIN
lGURE WHICH SHOWS THE SOIL CARBON TRAJECTORIES FOR
PLANTED PINE ON PRODUCTIVE SITES OF DIFFERENT PREVIOUS
(EATHAND3MITH
3OIL#ARBON!CCOUNTINGAND!SSUMPTIONSFOR&ORESTRYAND&OREST2ELATED,AND5SE#HANGE
A RELATIONSHIP BETWEEN FOREST MERCHANTABLE VOLUME AND
SOIL CARBON (OWEVER RELATIONSHIPS WITH FOREST AGE ARE
USEDFORSTANDSLESSTHANYEARSOFAGEWHENMERCHANT
ABLEVOLUMESAREZEROORCLOSETOZERO6OLUMEISTHOUGHT
TO MORE ACCURATELY REmECT THE LEVEL OF SOIL CARBON WHEN
CHARACTERIZINGOLDERSTANDS0LANTINGAAND"IRDSEY
"IRDSEYAND(EATH
4HE)0##-ETHODOF%STIMATING#ARBON
&IGURE ˆ3OIL ORGANIC CARBON M BY FOREST STAND AGE
FOR PLANTED PINE ON HIGH PRODUCTIVITY SITES IN THE SOUTHEASTERN
5NITED 3TATES BASED ON OLD ASSUMPTIONS4HE ESTIMATES ARE
WEIGHTEDAVERAGESBASEDONPERCENTAGESOFFORESTINPREVIOUS
NONFORESTLANDUSE4HISISBUTONEEXAMPLESETOFEQUATIONS
AVAILABLEFOREACHCOMBINATIONOFREGIONFORESTTYPEANDOWNER
SHIP3OURCE0ERSONALCOMMUNICATION$ATAFROM2ICHARD
"IRDSEY0ROGRAM-ANAGER53$!&OREST3ERVICE.ORTHEASTERN
2ESEARCH3TATION2ADNOR0!
LAND USE IN THE SOUTHEASTERN 5NITED 3TATES /NE OF THE
TRAJECTORIESILLUSTRATESHOWSOILCARBONPERHECTAREWOULD
ACCRUE BY AGE FOR FORESTLAND THAT HAD BEEN CLEARCUT AND
REPLANTED 4HE SECOND TRAJECTORY REPRESENTS SOIL CARBON
PER HECTARE FOR FOREST GROWING ON LAND THAT WAS PREVI
OUSLY CROPLAND (OWEVER NEITHER OF THESE TRAJECTORIES
ACCURATELYREPRESENTSTHEAGGREGATESOILCARBONTRAJECTORY
FOR A MIXTURE OF PREVIOUS LAND USES /N FOREST INDUSTRY
LANDSFOREXAMPLEPERCENTOFTHEFORESTLANDWASPRE
VIOUSLY FOREST WHILE PERCENT WAS CROPLAND 4HE SOIL
CARBONTRAJECTORYISANAVERAGEOFTHECARBONONCLEARCUT
FORESTSANDCARBONONCROPLANDWEIGHTEDBYPERCENTAGE
OF LAND IN EACH USE 4HIS AVERAGE TRAJECTORY IS LABELED
h&ORESTINDUSTRYv4HETRAJECTORYFORh/THERPRIVATEvOWN
ERSHIPISBASEDONTHEESTIMATETHATPERCENTWASPREVI
OUSLYINCROPLANDANDPERCENTWASPREVIOUSLYFORESTED
3OILCARBONTRAJECTORIESOFOTHERFORESTTYPESANDREGIONS
WERECALCULATEDUSINGTHESAMEWEIGHTINGPROCEDURE
0REVIOUS LAND USE HEAVILY INmUENCES SOIL CARBON AS
ILLUSTRATEDINlGURE)NTHISEXAMPLESOILCARBONPER
HECTAREATAGERANGESFROM-G#PERHAONCROPLAND
TO -G # PER HA ON A CLEARCUT !FTER ABOUT YEARS
OFFORESTDEVELOPMENTSOILCARBONISABOUT-G#PER
HAREGARDLESSOFPREVIOUSLANDUSE!GEISOFTENDIFlCULTTO
DETERMINEINNATURALLYREGENERATEDFORESTSANDFORESTLAND
ISOFTENNOTFULLYOCCUPIEDBYTREES!LTHOUGHTHISlGURE
ILLUSTRATES A RELATIONSHIP BETWEEN SOIL CARBON AND FOREST
AGETHEACCOUNTINGMETHODUSEDBY20!OFTENEMPLOYS
/NE OF THE OBJECTIVES OF THE )0##/%#$)%! 0RO
GRAMMEON.ATIONAL'REENHOUSE'AS)NVENTORIES)0##
/%#$)%!WASTODEVELOPADEFAULTMETHOD
OLOGYWITHTHECONCURRENCEOFTHEINTERNATIONALSCIENTIlC
COMMUNITYWHICHNATIONSCOULDFOLLOWORUSEASGUIDE
LINESTOREPORT'('EMISSIONSANDSINKS!GOALWASTOBE
BOTHEXTENSIVEANDSIMPLE4HISWOULDPRODUCEAMETH
ODOLOGYAPPROPRIATEFORUSEBYANYNATIONYETESTIMATES
COULDBEDETERMINEDEVENWITHLIMITEDDATA.ATIONSARE
STRONGLY ENCOURAGED TO USE LOCAL INFORMATION IF DOING
SO WOULD INCREASE ACCURACY OF ESTIMATES 7E REVIEW
THE METHODOLOGY OF THE ,AND 5SE #HANGE AND &ORESTRY
,5#&SECTIONOFTHEGUIDELINES)0##/%#$)%!
BY lRST DISCUSSING SOME BASIC ASSUMPTIONS 7E THEN
ADDRESS SOME ISSUES OF ACCOUNTING FOR CARBON UNDER
CHANGESINLANDUSE
#LASSIlCATION OF LAND AND ACTIVITIES ON THAT LAND ARE
IMPORTANT lRST STEPS IN THE )0## GUIDELINES !REAS OF
FORESTS THAT ARE CURRENTLY NOT SIGNIlCANTLY DISTURBED BY
HUMANSAREEXCLUDEDFROMCALCULATIONS4HATISAREASOF
LAND WHICH FEATURE A CARBON mUX OF APPROXIMATELY ZERO
AREIGNOREDFORCARBONACCOUNTINGPURPOSES4HEDISTINC
TIONBETWEENFORESTRYANDOTHERAGRICULTURALACTIVITIESALSO
DISTINGUISHESHOWCARBONISCOUNTED4HE,5#&SECTION
OF THE GUIDELINES INCLUDES LAND USE CHANGE AND CARBON
EMISSIONSFROMAGRICULTURALACTIVITIES4HEREISASEPARATE
EXTENSIVE SECTION ON AGRICULTURE HOWEVER IT FOCUSES ON
NITROUSOXIDEEMISSIONSFROMAGRICULTURALSOILSEMISSIONS
FROM AGRICULTURAL BURNING INCLUDING PRESCRIBED BURNING
OF SAVANNAS AND METHANE AND NITROUS OXIDE EMISSIONS
FROMDOMESTICLIVESTOCK0RESCRIBEDBURNINGOFSAVANNAS
ISHANDLEDINTHEAGRICULTURESECTIONYETBURNINGOFSAVAN
NASFORTHEPURPOSEOFCHANGINGLANDUSEISHANDLEDINTHE
,5#&SECTION
4HE)0##GUIDELINESCATEGORIZEFORESTLANDASTROPICAL
TEMPERATEORBOREAL7EREVIEWTHEOVERALLMETHODOLOGY
!T THE THIRD #ONFERENCE OF THE 0ARTIES IN +YOTO *APAN THE
0ARTIESAGREEDTOCOUNTFORESTCARBONFROMAFFORESTATIONDEFOR
ESTATIONANDREFORESTATIONSINCE(OWEVERDElNITIONSFOR
THESE THREE TERMS ARE STILL UNDER DISCUSSION SO WE REVIEW THE
CURRENTPUBLISHEDGUIDELINES
53$!&OREST3ERVICE'EN4ECH2EP2-23n'42n
3OIL#ARBON!CCOUNTINGAND!SSUMPTIONSFOR&ORESTRYAND&OREST2ELATED,AND5SE#HANGE
(EATHAND3MITH
4ABLEˆ(EADINGSOFMAJORCATEGORIESFORCHANGESINFORESTANDOTHERWOODYBIOMASSABOVEGROUNDCARBONSTOCKSSUGGESTEDBY
)0##FORCALCULATINGNATIONALGREENHOUSEINVENTORIES
,ATITUDE
4EMPERATE
"OREAL
4ROPICAL
7OODYBIOMASSSTOCKS 0LANTATIONS
#OMMERCIAL
/THER
.$
0LANTATIONS
/THERFORESTS
/THER
#HANGESINHARVESTING
#ONVERSIONABANDONMENT
$OUGLASlR
,OBLOLLYPINE
%VERGREEN
$ECIDUOUS
3PECIlEDBYUSER
#ONIFEROUS
"ROADLEAF
'RASSLANDS
.$
!CACIASPP
%UCALYPTUSSPP
4ECTONAGRANDIS
0INUSSPP
0INUSCARIBAEA
-IXEDHARDWOODS
-IXEDFASTGROWINGHARDWOOD
-OIST
3EASONAL
3PECIlEDBYUSER
3PECIlEDBYUSER
-IXED
"ROADLEAFCONIFEROUS
#ONIFEROUS
&ORESTTUNDRA
'RASSLANDSTUNDRA
7ETVERYMOIST
-OISTSHORTDRYSEASON
-OISTLONGDRYSEASON
$RY
-ONTANEMOIST
-ONTANEDRY
4ROPICAL3AVANNAGRASSLAND
.$.ODEFAULTSPECIlED
3OURCE)0##/%#$)%!
BUTWEFOCUSONTEMPERATEFORESTSBECAUSETHEYCONSTITUTE
THEMAJORITYOF53FORESTLANDS!BOVEGROUNDANDBELOW
GROUNDCARBONPOOLSAREESTIMATEDSEPARATELY4EMPORAL
RESPONSES TO PERTURBATIONS DIFFER FOR TWO SYSTEMS SEV
ERAL DECADES MAY BE NEEDED FOR SOIL CARBON TO RESPOND
TO CHANGE AND STABILIZE WHILE ONLY A FEW YEARS MAY BE
ADEQUATETODESCRIBERESPONSESOFABOVEGROUNDBIOMASS
TOTHESAMECHANGES
4HE DEFAULT APPROACH FOR ESTIMATING ABOVEGROUND
CARBONINVENTORIESFEATURESBIOMASSTABULATEDBYTHECAT
EGORIESOFFORESTANDOTHERWOODYBIOMASSSTOCKSFOREST
ANDGRASSLANDCONVERSIONANDABANDONMENTOFMANAGED
LANDS%ACHOFTHESECATEGORIESISFURTHERDIVIDEDBYVEG
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!CCOUNTING FOR TOTAL LAND AREA IS IMPORTANT BECAUSE
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SOILMUCHMOREDIFlCULTANDMAYHAVECONTRIBUTEDTOTHE
nCMLAYERINCREASINGINSOILCARBONEIGHTYEARSAFTER
HARVEST(UNTINGTONAND2YAN4HEAPPARENTEFFECT
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DIRECTLYAFUNCTIONOFSOILDISTURBANCEATTHETIMEOFHAR
VEST !NOTHER POSSIBLE REASON IS THAT THE USE OF CHRO
NOSEQUENCESINSOMESTUDIESMAYINADVERTENTLYINCLUDE
UNKNOWNSITESPECIlCEFFECTS
3OIL CARBON DYNAMICS QUALITATIVELY SIMILAR TO THOSE
FOUND AT (UBBARD "ROOK HAVE ALSO BEEN IDENTIlED IN
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BINEDSAMPLINGATMOSTLYTHEnCMSOILDEPTHn
SAMPLESATTHREETOlVEPERMANENTSAMPLINGLOCATIONSAT
SEVERALWATERSHEDSATTHREEDEPTHSWITHMODELEDINFOR
MATIONATMOSTLYTHEnCMDEPTH4HEYSTUDIEDSOIL
CARBON DYNAMICS AFTER HARVEST OF A YEAROLD LOBLOLLY
PINE FOREST ON AN ERODED PREVIOUSLY CULTIVATED SITE IN
THE 0IEDMONT OF THE SOUTHEASTERN 5NITED 3TATES 4HEY
FOUNDANINCREASINGSOILCARBONTRENDAFTERHARVESTWHICH
QUICKLY DECREASED BELOW PREHARVEST CARBON BUT BY YEARSAFTERHARVESTITHADINCREASEDABOVEPREHARVESTSOIL
CARBONLEVELS4HISISILLUSTRATEDINlGUREWHICHSOME
WHATRESEMBLESTHEOLDERACCEPTEDTHEORYOFSOILCARBON
DYNAMICS SHOWN IN lGURE (OWEVER SOME OF THEIR
INFORMATIONINTHEnCMHORIZONWASESTIMATEDNOT
MEASURED
0ENNOCKANDVAN+ESSELCONDUCTEDASTUDYON
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SIX ASPENWHITE SPRUCE STANDS IN CENTRAL 3ASKATCHEWAN
#ANADA4HEYSAMPLEDFROMTOCM2ESULTSSHOWED
ASIGNIlCANTPINCREASEOFPERCENTINSOILCARBON
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PARED TO MATURE FORESTS (OWEVER ONE CAUTION IN INTER
PRETINGTHERESULTSISTHATTHEYDIDNOTSEPARATETHEFOREST
mOOR FROM THE MINERAL SOIL SURFACE ON CLEARCUT SITES THAT
HADBEENPREPAREDFORTREEPLANTING4HESURFACELAYERWAS
MISSING OR VERY THIN ON THESE SITES AND IT WAS FELT THAT
MEASURING THE FOREST mOOR SEPARATELY WOULD HAVE INTRO
DUCEDMOREERRORTHANMEASURINGITWITHTHEMINERALSOIL
&IGUREˆ4RENDOFSOILORGANICCARBONAFTERPREHARVESTLOW
INTENSITY BURNS AND CLEARCUT HARVEST OF A YEAROLD LOBLOLLY
PINESTANDONERODEDSOILFOLLOWING6AN,EARETAL
3AMPLINGFROMACHRONOSEQUENCESUGGESTSANINCREASE
INSOILCARBONWITHREFORESTATIONEVENWHERETHETRANSI
TORY INCREASE IMMEDIATELY AFTER HARVEST DID NOT APPEAR
5SINGACHRONOSEQUENCE%NTRYAND%MMINGHAM
FOUND AN INCREASE IN SOIL CARBON IN THE TOP CM OF
$OUGLASlRSTANDSOFINCREASINGAGE4HESTANDSWERECAT
EGORIZEDASYOUNGGROWTHABOUTYEARSOLDSECOND
GROWTH ABOUT YEARS OLD AND OLDGROWTH FROM TO YEARS OLD 3OIL CARBON ALMOST DOUBLED BETWEEN
YOUNGGROWTH AND SECONDGROWTH BUT THE INCREASE WAS
NOT SIGNIlCANT AT P 3OIL CARBON OF THE OLD GROWTH
WASALMOSTTHREETIMESTHATOFYOUNGGROWTHANDITWAS
SIGNIlCANTLYGREATERPTHANBOTHYOUNGERGROUPS
3TRONGSTUDIEDlVECUTTINGTREATMENTSWITHTHREE
REPLICATIONSEACHINNORTHERNHARDWOODSINNORTHEASTERN
7ISCONSINUSINGACHRONOSEQUENCEPRETREATMENTVALUES
WERE NOT KNOWN FOR EACH TREATMENT 4HE FORESTS WERE
LOGGEDINTHEEARLYSANDWEREGENERALLYEVENAGED
4HESTUDYWASINITIATEDINANDHASBEENCONTINUING
FORYEARS4HETREATMENTSINCLUDEDREPLICATIONSOFCON
TROLDIAMETERLIMITCUTANDTHREELEVELSOFINDIVIDUALTREE
SELECTION .O TREES WERE CUT IN THE CONTROL ALL TREES CMANDLARGERWERECUTININTHEDIAMETERLIMITCUT
AND HEAVY MEDIUM AND LIGHT INDIVIDUAL TREE SELECTION
WASPERFORMEDINAND4HEREWAS
NO STATISTICAL DIFFERENCE P IN SOIL CARBON IN THE
nCMHORIZONBUTTHEREWASASIGNIlCANTDIFFERENCEIN
THE n CM DEPTH AND THERE WAS A TREND OF INCREASING
SOILCARBONASBASALAREAINCREASED4HISIMPLIESTHATSOIL
CARBON MAY DECREASE WITH INCREASING HARVEST INTENSITY
5NFORTUNATELYBECAUSETHISSTUDYUSESACHRONOSEQUENCE
ITMAYBETHATTHESOILCARBONDIFFERENCESBETWEENTREAT
MENTSAREDUETOINITIALSITEDIFFERENCESNOTTOHARVESTING
INTENSITY
53$!&OREST3ERVICE'EN4ECH2EP2-23n'42n
3OIL#ARBON!CCOUNTINGAND!SSUMPTIONSFOR&ORESTRYAND&OREST2ELATED,AND5SE#HANGE
/THER STUDIES WERE REVIEWED BUT MAY BE OF LIMITED
USEFULNESS7EREWORKEDTHEDATAIN&RAZER-C#OLLAND
0OWERSANDFOUNDSOILCARBONINCREASEDPERCENT
BYlVEYEARSAFTERCLEARCUTTINGANDDECREASEDPERCENT
BYYEARSAFTERCLEARCUTTINGUNDERREGENERATIONRELATIVE
TOANUNCUTAREA(OWEVERTHEREWERENOREPLICATIONSAND
THEREFORENOSTATISTICSANDTHEYSAMPLEDONLYTOADEPTH
OFCM/LSSONETALSTUDIEDSOILCARBONIN3COTS
PINE AND .ORWAY SPRUCE AT FOUR SITES IN 3WEDEN 4HEY
EXAMINED THE TOP n CM SOME n YEARS FOLLOWING
HARVEST AND BULK DENSITY WAS ASSUMED TO REMAIN CON
STANT IN THEIR CALCULATION OF TOTAL SOIL CARBON 4HE THREE
TYPESOFHARVESTSSTUDIEDWERECONVENTIONALSTEMHARVEST
RESIDUES LEFT ON SITE HARVESTING ALL ABOVEGROUND TREE
PARTSEXCEPTNEEDLESANDWHOLETREEHARVESTINGNORESI
DUESLEFTONSITE)FWEASSUMEHARVESTINGDIDNOTIMPACT
BULK DENSITY SOIL CARBON INCREASED FAIRLY CONSISTENTLY IN
THE n CM LAYER BY ABOUT -G # PER HA NOT STATISTI
CALLY SIGNIlCANT AT P ON EACH SITE 4HERE WERE NO
SIGNIlCANTTRENDSOFHARVESTINTENSITYOVERALLSITESHOW
EVERDISTURBANCEFROMHARVESTINGWASCAREFULLYAVOIDED
/PERATORS TRIED TO AVOID SOIL COMPACTION AND MIXING OF
SOILLAYERS"LACKAND(ARDENSTUDIEDTHEEFFECTOF
CLEARCUTTINGINAMIXEDCONIFERSTANDIN#ALIFORNIA4HEY
SAMPLEDSOILINTHEnCMLAYERINSTANDSOFSIXDIFFER
ENTAGESBUTFOUNDNOSTRONGLYCONSISTENTTREND4HEYDID
NOTETHEYOUNGERSTANDSnYEARSOLDINGENERALCON
TAINEDMORESOILCARBONTHANTHEOLDGROWTHSTAND4HEY
CONCLUDEDTHATOTHERFACTORSBESIDESHARVESTINGCONFOUND
RESULTS7EALSOREVIEWEDOTHERSTUDIESBUTWEDECIDED
NOTTOINCLUDETHEMBECAUSETHEYINCLUDEDONLYPERCENT
CARBON OR WERE LIMITED IN DURATION OR IN DEPTH FOR
INSTANCE+NOEPPAND3WANK
!FFORESTATIONAND$EFORESTATION
7E REVIEW AFFORESTATION AND DEFORESTATION STUDIES
TOGETHER BECAUSE SOILS IN 53 FORESTS ARE GENERALLY
ACCEPTEDTOLOSESOILCARBONWHENCLEAREDANDCULTIVATED
ANDTHENACCUMULATESOILCARBONAFTERTHELANDISREVEG
ETATED WITH FOREST &OREST SOIL EVENTUALLY ACCUMULATES
CARBON TO A MAXIMUM LEVEL REGARDLESS OF PREVIOUS
LAND USE UNLESS SEVERE EROSION HAS OCCURRED 3IMILARLY
EXPECTED DECREASES IN SOIL CARBON PARTLY DEPEND ON USE
AFTER DEFORESTATION SUCH AS ANNUAL CROPS PASTURE LAND
OR URBAN DEVELOPMENT &OR EXAMPLE AS MENTIONED PRE
VIOUSLY $AVIDSON AND !CKERMAN CONCLUDE SOIL
CARBONDECREASESREGIONALLYBYPERCENTRANGINGFROM
TOPERCENTINTHEENTIRESOILCOLUMNWHENFORESTSARE
CLEAREDANDTHELANDCULTIVATED
4HEPERCENTLOSSISGENERALLYACCEPTEDASTHEMAG
NITUDEOFSOILCARBONCHANGEFORDEFORESTATIONANDCULTI
VATION HOWEVER THE LENGTH OF TIME OVER WHICH THE LOSS
TAKESPLACEISSTILLBEINGDEBATED(OWLONGDOESITTAKETO
53$!&OREST3ERVICE'EN4ECH2EP2-23n'42n
(EATHAND3MITH
&IGUREˆ5PPERANDLOWERRANGEOFDYNAMICSOFSOILCARBON
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REACCUMULATESOILCARBONTOITShMAXIMUMvLEVEL(UN
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PERCENTOVERAPERIODOFYEARS4HISPERCENTAGEIS
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SITE3CHIFFMANAND*OHNSONESTIMATEDABOUT
-G#PERHAPERYEARABOUTnPERCENTACCUMULATED
ONERODEDSOILSIN6IRGINIA%RODEDSOILSPRESENTASPECIAL
PROBLEMFORACCOUNTINGBECAUSEERODEDSOILCARBONMAY
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4RENDSOF3OIL#ARBONIN#URRENT,ITERATURE
"ASEDONTHISPRELIMINARYREVIEWSOILCARBONDYNAM
ICS FOLLOWING HARVEST APPEAR TO DEPEND ON THE AMOUNT
OF DISTURBANCE CAUSED BY LOGGING OPERATIONS 4HE DIS
TURBANCEASSOCIATEDWITHSOMECOMMERCIALHARVESTSMAY
CAUSESOILCARBONTOINCREASEINITIALLYINTHElRSTFEWYEARS
(EATHAND3MITH
3OIL#ARBON!CCOUNTINGAND!SSUMPTIONSFOR&ORESTRYAND&OREST2ELATED,AND5SE#HANGE
BY n PERCENT THEN DECLINE TO BELOW INITIAL VALUES BY
n PERCENT BY n YEARS AFTER HARVEST AND EVENTU
ALLYINCREASEAGAIN3OMESTUDIESSHOWEDCHANGESINSOIL
CARBON BELOW THE n CM DEPTH INDICATING THAT EXPER
IMENTAL SOIL STUDIES SHOULD SAMPLE LOWER SOIL DEPTHS
3EVERELYERODEDSOILSALSOCREATEADDITIONALPROBLEMSCON
CERNING DEPTH BECAUSE MUCH OF THE ORIGINAL SOIL MAY
BE ERODED 2ESULTS COMPARED AT APPARENTLY EQUIVALENT
DEPTHS IN ERODED AND NONERODED SOILS MAY BE DIFlCULT
TOINTERPRET/THERASPECTSOFSAMPLINGDESIGNSIDENTIlED
ASPOTENTIALPROBLEMSINCLUDEINITIALSITEDIFFERENCESINTHE
USEOFCHRONOSEQUENCESUSEOFPERCENTCARBONASAPROXY
FOR TOTAL CARBON AND THE NEED FOR APPROPRIATE SAMPLE
SIZETOPRODUCESIGNIlCANTRESULTS3OILCARBONFOLLOWING
DEFORESTATIONANDCULTIVATIONDECLINESABOUTPERCENTIN
THEENTIRESOILCOLUMNWITHINYEARSOFCULTIVATION3OIL
CARBON INCREASES GRADUALLY FOLLOWING AFFORESTATION WITH
GOOD STOCKING INCREASING BY PERCENT AT A RATE MORE
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3UMMARY
7EREVIEWEDTWOACCOUNTINGSYSTEMSONEDEVELOPED
BY THE )0## AND THE OTHER FROM THE 20!
ASSESSMENT"IRDSEYAND(EATH"OTHSYSTEMSBASE
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ANDAREA"OTHMETHODSRECOGNIZETHEIMPORTANCEOFPRE
VIOUSLANDUSE4HE)0##DEFAULTSYSTEMEXPLICITLYCOUNTS
SOIL CARBON LOSS WHEN FORESTS ARE CLEARED AND CULTIVATED
BUTDOESNOTINCLUDETHEACCUMULATIONOFSOILCARBONDUE
TOAFFORESTATIONALTHOUGHSOILCARBONINCREASESDUETODIF
FERINGAGRICULTURALTILLAGEPRACTICESAREINCLUDED"IRDSEY
AND(EATHEXPLICITLYACCOUNTFORTHEACCUMULATION
OF SOIL CARBON DUE TO AFFORESTATION BUT DO NOT EXPLICITLY
COUNT SOIL LOSS AFTER DEFORESTATION 4HIS IS BECAUSE THE
20!ANALYSISFOCUSEDONLYONCARBONINTHEFORESTSECTOR
$EFORESTED AREAS WERE ASSUMED COUNTED IN THE AGRICUL
TURALORURBANSECTORNOTFORESTSANDOVERTHELASTn
YEARSMORELANDHASBECOMEAFFORESTEDTHANDEFORESTED
2ECENTSCIENTIlCSTUDIESINDICATETHATHARVESTINGMAY
INmUENCESOILCARBONANINITIALSLIGHTINCREASEFOLLOWEDBY
ADECREASEANDlNALLYANINCREASE7ESPECULATETHATSOIL
CARBONWILLEVENTUALLYRETURNTOPREHARVESTLEVELS4HIS
CORRESPONDSTOTHEPATTERNINTHESOILCARBONASSUMPTIONS
IN THE 20!ANALYSIS 4HE MAGNITUDE OF THE EFFECT SEEMS
TO DEPEND ON THE LEVEL AND TYPE OF DISTURBANCE FROM
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AGEMENT SUCH AS THE 5NITED 3TATES SHOULD GIVE FURTHER
CONSIDERATION TO THE OVERALL LEVEL OF DISTURBANCE IN HAR
VESTING OPERATIONS AND REVISE SOIL CARBON ASSUMPTIONS
ACCORDINGLY 3OIL CARBON DECREASES FOR n YEARS FOL
LOWING DEFORESTATION AND CULTIVATION AND THEN REMAINS
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