植物營(yíng)養(yǎng)元素的土壤化學(xué)3-土壤中的C(上)

第二章土壤碳素循環(huán)及調(diào)控Chapter2CarboncyclesinSoilLowcarboneconomyGHGs=greenhousegasesIPCC=IntergovernmentalPanelonClimateChange

（政府間氣候變化專(zhuān)業(yè)委員會(huì)）“哥本哈根氣候會(huì)議”Fig.Deviationsfromrecentexponentialincreasesinfossilfuelburning(Bacastow&Keeling,1974)Theindustrialrevolution,whichstartedaround1750,drivenbycheapandeasyaccesstomodernenergythroughfossilfuelcombustion,ledtomassproductionofmodernamenitiesatlowcost.Indeedallavailedamenitiesbyindustrializedsocietiesarebasedonfossilfuelderivedenergy.Thus,themoderncivilizationcanbeappropriatelytermed“theCarbonCivilization”ortheC-Era(Lal,2007),ascomparedwiththehistorichydriccivilizations,whichthrivedinthevalleysofTigris,Euphrates,Nile,Indus,Huangetc.Indeed,theworldenergyconsumptionincreased40timesbetween1850and2005.TheatmosphericconcentrationofCO2hasincreasedfrom280ppmvsincethelate1700stoabout380ppmvin2006,ispresentlyincreasingattherateof1.8ppmvyr?1or0.47%yr?1(WMO,2006.)政府間氣候變化專(zhuān)門(mén)委員會(huì)(IPCC)第三次評(píng)估報(bào)告（2001）二十世紀(jì)全球平均氣溫上升0.60.2C;從1861年以來(lái)，二十世紀(jì)九十年代是最熱的10年，其中，1998年是最熱的一年;在過(guò)去的一千年中，二十世紀(jì)是最熱的一個(gè)世紀(jì);從1950年到1993年，陸地夜間日平均氣溫每10年升高約0.2C，白天升高約0.1C。海面氣溫升高約為陸地的一半.海平面上升；降水分布發(fā)生變化；沙漠化加??；自然災(zāi)害發(fā)生頻繁增加。全球變暖的后果?HumanpopulationSizeResourceuseHumanenterprisesAgricultureIndustryRecreationInternationalcommerceLandtransformation

LandclearingForestryGrazingIntensificationBioticadditionsandlosses

InvasionHuntingFishingGlobalbiogeochemistry

CarbonNitrogenWaterSyntheticchemicalsOtherelementsClimatechange

EnhancedgreenhouseAerosolsLandcoverLossofbiologicaldiversity

ExtinctionofspeciesandpopulationsLossofecosystems改進(jìn)能源結(jié)構(gòu)提高能源效率植樹(shù)種草，增加生態(tài)系統(tǒng)對(duì)CO2的吸收如何減少溫室效應(yīng)氣體的排放?Csequestration(碳固定)CarbonsequestrationimpliesthenetremovalofCO2fromtheatmosphereintolong-livedpoolsofC,suchasterrestrialandgeologic.Inotherwords,itiscapturingandsecurelystoringCbybioticphotosynthesisandabioticinjectionintogeologicstrataoroceanprocesses.LalR.SoilSci.Soc.Am.J.2007,71:1425–1437Carbonsequestration1997年12月，面對(duì)環(huán)境惡化，氣候變暖，在日本京都舉行的聯(lián)合國(guó)氣候大會(huì)通過(guò)了《京都議定書(shū)》，目標(biāo)是在2008年至2012年間，將發(fā)達(dá)國(guó)家CO2等６種溫室氣體的排放量在1990年的基礎(chǔ)上平均削減5.2％。為了使議定書(shū)真正發(fā)揮作用，協(xié)議規(guī)定，只有在占1990年全球溫室氣體排放量55％以上的至少55個(gè)國(guó)家批準(zhǔn)后才能生效。京都議定書(shū)（Kyotoprotocol）Theindustrialemissionsofcarbon(C)inChinaareabout1Pgyr-1,secondonlytotheUnitedStatesestimatedat1.84Pgyr-1for2000.Becauseofthedifferencesinpopulation,however,thepercapitaemissionis0.08Tgper100000inhabitantsinChinacomparedwith0.55Tgper100000inhabitantsintheUnitedStates(NET,1998).Withitsrapidlyincreasingeconomy,however,ChinamaysurpasstheUnitedStatesastheworld’slargestemitterofCby2020.LalR.LandDegrad.Develop.13:469–478(2002)我國(guó)2001年的工業(yè)CO2排放為1Pg/yr，僅次于美國(guó)（1.84Pg/yr），預(yù)計(jì)在2005年會(huì)超過(guò)美國(guó),達(dá)到2Pg/yr，我國(guó)面臨著減排的巨大壓力。這是一個(gè)關(guān)系國(guó)家環(huán)境外交和農(nóng)業(yè)可持續(xù)發(fā)展的食物安全與環(huán)境安全保障的重大問(wèn)題。黃耀.第四紀(jì)研究.2006按照IPCC第2次評(píng)估報(bào)告提供的全球增溫潛勢(shì)數(shù)據(jù)計(jì)算,1994年中國(guó)溫室氣體總排放量為36.50×108tCO2當(dāng)量,其中CO2,CH4和N2O分別占73.1%,19.7%和7.2%。能源活動(dòng)是中國(guó)CO2排放的主要來(lái)源,占90.95%；農(nóng)業(yè)活動(dòng)和能源活動(dòng)是CH4排放的主要來(lái)源，分別占50.15%和27.33%；農(nóng)業(yè)活動(dòng)是N2O排放的主要來(lái)源,占92.4%。About20%oftheglobalemissionpresentlycomefromlandusechange(IPCC,2001)Agriculture’sContributiontoClimateChange–SternReviewAgriculture=14%ofglobalGHGsLanduse(deforestation)=18%ofglobalGHGsSource:SternReview:theEconomicsofClimateChangeAgriculture’sContributiontoClimateChange–SternReview38%38%13%11%Globalsourcesofnon-CO2emissionsfromtheagriculturesector(2000)Source:SternReview:theEconomicsofClimateChangeHillelD.2008Agricultureaccountsforasizableshareofnon-CO2emissions,includinganestimated47%ofCH4andasmuchas84%ofN2O.UKAgriculture-SomeKeyFactsOnly0.5%ofGDP(agri-foodsector7%)1.7%ofemployment(agri-food14%)Manages70%ofEngland’sland(80%ofruralland),withhugebenefitsforlandscape,biodiversityandaccessBut…contributes7%oftheUK’sGHGemissions(37%ofmethane,63%ofnitrousoxide)…andMajorityofnitrateemissionstowaterandammoniaemissionstoairJeremyEppel,DeputyDirector,Food&FarmingGroup,Defra全球氣候變化簡(jiǎn)史不同的聲音.“氣候變化問(wèn)題的非主流思考：事實(shí)與邏輯”,科學(xué)時(shí)報(bào),2009年8月11“哥本哈根鬧劇后的沉思”,科學(xué)時(shí)報(bào),2010-02-11氣候問(wèn)題的“郵件門(mén)”

(2009年11月)英國(guó)東英吉利大學(xué)氣候研究中心上千封電子郵件和3000多份有關(guān)氣候變化的文件被曝光，這些文件顯示：這些氣象學(xué)家利用各國(guó)政府對(duì)氣候變化問(wèn)題的關(guān)心，用一些不實(shí)數(shù)據(jù)制造氣候變暖的假象，營(yíng)造恐慌心理，然后從政府或其他機(jī)構(gòu)手中騙得了更多的科研經(jīng)費(fèi)。氣候問(wèn)題的“冰川門(mén)”事件IPCC在2007年發(fā)布的第四次評(píng)估報(bào)告中寫(xiě)道“喜馬拉雅冰川的消融速度超過(guò)了世界其他地區(qū)的冰川，如果全球變暖的速度持續(xù)下去，喜馬拉雅冰川在2035年甚至更早前消失的可能性非常高”?？陀^(guān)對(duì)待IPCC的報(bào)告美國(guó)250余名科學(xué)家聯(lián)名上書(shū)呼吁不要指責(zé)IPCC荷蘭250余名科學(xué)家聯(lián)名問(wèn)題與對(duì)策:我國(guó)已成為全球最大的溫室效應(yīng)氣體排放國(guó)，面臨著減排的巨大壓力。丁仲禮,段曉男,葛全勝,張志強(qiáng).2050年大氣CO2濃度控制:各國(guó)排放權(quán)計(jì)算.中國(guó)科學(xué)，D輯，2009，39(8):1009-1027文章提出了“人均累計(jì)排放指標(biāo)”的概念，以體現(xiàn)“共同而有區(qū)別的責(zé)任”原則和公平正義準(zhǔn)則。設(shè)定2050年前將大氣CO2濃度控制在470ppmv的目標(biāo),以1900年為時(shí)間起點(diǎn),對(duì)各國(guó)過(guò)去(1900-2005年)人均累計(jì)排放量、應(yīng)得排放配額以及今后(2006-2050年)的排放配額做了逐年計(jì)算.全球碳循環(huán)概況土壤碳庫(kù)在全球碳循環(huán)中的作用土壤碳的不同組分及其特性土壤碳庫(kù)的調(diào)節(jié)TableDistributionofCinsomeofthemaincompartmentsintheearth(Delwiche)CompartmentAmountofC,×1012kgAtmosphere700Soilorganicmatter(to2mdepth)2500Landlifeforms480Marinehumus3000Oceanlifeforms50Dissolvedcarbonate-bicarbonateinoceans3840Coalandpetroleum1×104

Sediments6×107

StevensonFJ,1986(1)全球碳分布全球碳循環(huán)概況FigThecarboncycle(Numbersarestorageas1015gorfluxesas1015gperyear)Ecology,ManuelCM,2002為了維持全球碳平衡，其焦點(diǎn)不是各個(gè)庫(kù)的碳貯存總量，而是每年碳的去處和動(dòng)態(tài)變化問(wèn)題。“源”與“匯”

(sourceandsink)把釋放二氧化碳的庫(kù)稱(chēng)為“源”，吸收二氧化碳的庫(kù)稱(chēng)為“匯”。PaulEA,2007(2)全球碳循環(huán)

SoilOceanBiotaAtmosphereTerrestrialphotosynthesisRivertransportoforganicmatterandcarbonatesRespirationCarbonateinputCO2exchangeLitterandrootinputCalcificationMarinerespirationMarinephotosynthesisTheshort-termCcycle人為因素對(duì)碳循環(huán)的干擾作用(單位Pg/年）大氣土地海洋沉積物礦質(zhì)有機(jī)碳碳酸鹽地質(zhì)庫(kù)5.4礦質(zhì)燃料燃燒5.3水泥生產(chǎn)0.1土地利用變化1.7土地吸收1.9海洋吸收1.9PostWM,etal.,BioScience?2004，54(10)Fig.1.IllustrationofthemainstoresandflowsofCinacropland,showingthreepoolsofsoilCforsimplicity,thoughrecognizingthatsoilCspansacontinuumofforms.(Janzen,2006,SBB)2.土壤碳庫(kù)在全球碳轉(zhuǎn)化及循環(huán)中的地位LalR.Science,2004Theglobalsoilcarbon(C)poolof2500gigatons(Gt)includesabout1550Gtofsoilorganiccarbon(SOC)and950Gtofsoilinorganiccarbon(SIC).ThesoilCpoolis3.3timesthesizeoftheatmosphericpool(760Gt)and4.5timesthesizeofthebioticpool(560Gt).(1)土壤碳庫(kù)的意義AtmosphericCpool(760Pg)TerrestrialCpool2860PgSOC=1550Pg(to1mdepth)SIC=750PgBiota=560PgFigure1.Cycleof

Cin

terrestrialecosystemandtheatmosphere.PhotosynthesisPlantandsoilrespirationLalR.Science.2004,304土壤碳庫(kù)的穩(wěn)定、增長(zhǎng)或釋放與大氣庫(kù)的變化有重要的關(guān)系，土壤能否增加碳儲(chǔ)存是關(guān)乎陸地生態(tài)系統(tǒng)凈碳匯飽和問(wèn)題的重要理論基礎(chǔ)，這一問(wèn)題已成為土壤與全球變化研究的重點(diǎn)和熱點(diǎn)科學(xué)問(wèn)題。SequestrationofCinsoils

isoftenseenasa‘win-win’proposition;itnotonlyremovesexcessCO2fromtheair,butalsoimprovessoilsbyaugmentingorganicmatter,anenergyandnutrientsourceforbiota.LalR.SoilSci.Soc.Am.J.2007,71:1425–1437LalR.SoilSci.Soc.Am.J.2007,71:1425–1437土壤的“Csinks”、“Csequestration”、“Cstorage”、“Cstabilization”及“Cstoringcapacity”(2)土壤碳貯量(Cstorage)土壤碳貯量的計(jì)算？土壤碳貯量=土壤容重×土壤有機(jī)碳含量×土壤體積Soilorganiccarbon=1550PgSoilinorganiccarbon=750PgYu,D.,etal.,RegionalpatternsofsoilorganiccarbonstocksinChina.JournalofEnvironmentalManagement(2006),Yu,D.,etal.,RegionalpatternsofsoilorganiccarbonstocksinChina.JournalofEnvironmentalManagement(2006),SoilsinChinacoveranareaof9.281×106km2intotal,withatotalSOCstockof89.14Pg(1Pg=1015g)andameanSOCdensityof96.0tC/ha.中國(guó)是世界上平均土壤碳密度較低的國(guó)家。全球全土碳密度平均為121t/hm2，我國(guó)全土平均有機(jī)碳密度的報(bào)道值介于80～105t/hm2，均遠(yuǎn)遠(yuǎn)低于世界平均值。表中國(guó)和歐洲表層土壤有機(jī)碳密度比較(tC/ha)土地利用歐洲中國(guó)土地總計(jì)70.852.0耕地53.037.0潘根興，趙其國(guó).地球科學(xué)進(jìn)展.2005不同土地利用方式對(duì)土壤剖面碳貯量的影響TableLand-useeffectsondensityoforganiccarbon(kg/m2)in416soilprofilesofeasternChina(adaptedfromCai,1995)HorizonNaturalvegetationFuelforestUplandfieldsPaddyfieldsA5.402.171.312.40B6.582.680.921.44C2.271.671.642.94Total14.256.523.876.78LandDegradation&Development,2002,13:469-478植物體組成及分解轉(zhuǎn)化特性土壤有機(jī)碳的組分及特性土壤有機(jī)碳穩(wěn)定性的機(jī)理3.土壤碳的不同組分及其特性PlantlitterastheprinciplesourceofsoilorganicmatterformationPlantsarethemainsourceofcarbontosoilsthroughtissueresiduesorviarootexudatesandsymbioticfungi.陳興麗等表1黃土高原幾種植物殘?bào)w的化學(xué)成分植物殘?bào)w有機(jī)碳CTOC(g·kg-1)全氮NTotalN(g·kg-1)C/NRatios木質(zhì)素(%)喬木A榆樹(shù)422.5825.3616.6625.20B小葉楊414.449.0245.9730.89C刺槐437.7314.9229.3327.78灌木D檸條466.8530.9515.0829.59E沙棘464.7029.7115.6427.14F山桃458.5328.2916.2125.76草本G長(zhǎng)芒草499.469.8650.6727.54H白羊草432.696.6165.4928.61I沙打旺427.9327.0115.8424.10J紫花苜蓿464.9832.7814.1924.47(C6H10O5)n+nH2OnC6H12O6C6H12O6+6O26CO2+6H2O+能量在通氣不良的情況下，可形成中間產(chǎn)物有機(jī)酸（丁酸）和甲烷、氫氣C6H12O6CH3CH2CH2COOH+2H2+2CO2+能量4H2+CO2CH4+2H2O碳水化合物的礦化有機(jī)物質(zhì)的礦化腐殖物質(zhì)形成的生物學(xué)示意圖

植物殘?bào)w

在微生物作用下轉(zhuǎn)化

糖

多酚

氨基化合物

木質(zhì)素分解產(chǎn)物

類(lèi)木質(zhì)素

醌

醌

腐殖物質(zhì)

1234Firststage:StevensonFJ,1986StagesinthemicrobialdecompositionDecayofeasilydegradablesubstances.PartialconversiontoCO2andbodytissueSecondstage:Thirdstage:Fourthandsuccessivestage:Celluloseandothercarbohydratesutilizedwithfurtherweightreduction.Formationofnewbodytissue.Partofpreviousbiomassmineralized.Furtherdecreaseincellulose.Initiationoflignindecomposition.Furtherdecreaseinbiomass.Furthercycling.Forplantresidues,aboutone-thirdofthecarbonwillremaininthesoilattheendofthegrowingseason.陳興麗等圖1黃土高原不同植物殘?bào)w碳的礦化率C/NA榆樹(shù)16.66B小葉楊45.97C刺槐29.33D檸條15.08E沙棘15.64F山桃16.21G長(zhǎng)芒草50.67H白羊草65.49I沙打旺15.84J紫花苜蓿14.19Fig.Influenceofleaftoughnessandnitrogencontentondecomposition(Gallardo&Merino,1993)Nitrogenmostoftencontrolstherateoforganicmatterdecomposition.(C/Nratio)圖1土壤植物生態(tài)系統(tǒng)中的碳、氮素轉(zhuǎn)化過(guò)程示意圖不同C/N比的植物殘?bào)w等土壤微生物量部分穩(wěn)定的有機(jī)氮

穩(wěn)定的腐殖質(zhì)態(tài)氮NH3,NO3-NH3,NO3-腐殖化作用施用肥料作物吸收CO2等釋放土壤中氮、碳協(xié)調(diào)是關(guān)鍵！有機(jī)物施入土壤的去向（1年后）：有機(jī)殘?bào)w（100）CO2（60-80%）土壤生物體（3-8%）非腐殖物質(zhì)（多糖、有機(jī)酸等）（3-8%）腐殖物質(zhì)（10-30%）腐殖質(zhì)SoilsinourEnvironment.1995TableThedecompositionofthedifferentcomponentsinthemixtureofresiduesfrompineandoakOriginallitterPortionofwhole(%)Percentagelostbydecompositionby:1styear2ndyear5thyear10thyearSugars1599100--Cellulose2090100--Hemicelluloses157592100-Lignins40507497100Waxes525437795Phenols510204370Wholelittermatters55.179.687.198.2StevensonFJ.CyclesofSoil.1986,pp-31TableCarbonretainedfrom14C-labeledplantmaterialappliedtofieldsoilsLocationTypeCarbonretained(%)RefereceRothmasted,EnglandRyegrasstopsandrootApproximately33%offirstyearirrespectiveofsoiltypeorplantmaterialJenkinsonWestGermanyWheatstrawandchaff31%afterfirstyearforfallowandcroppedsoilIAEAAustriaMaize47%afterfirstyearwhenappliedinAugustand33%whenappliedinOctoberIAEASaskatchewan,CanadaWheatstraw35-45%afterfirstgrowingseasonShieldsandPaulColorado,USABluegramaa.herbageb.Roots43-46%after412days63-74%after412daysNyhanNigeriaRyegrass20%afterfirstyearand14%aftertwoyears.Jenkonson&Ayanaba通氣性狀況對(duì)土壤有機(jī)質(zhì)含量的影響通氣淹水土壤黏粒含量對(duì)有機(jī)質(zhì)含量的影響水分狀況對(duì)植物體分解的影響FigDecompositionofFraxinusleavesatwetteranddriersites(Gallardo&Merino,1993)Science,1997,277:504-509PaulEA,2007SolubleinpolarsolventsNon-hydrolyzable/solubleinpolarsolventsHydrolyzableSoilorganicmatter(SOM)NotrecalcitrantCelluloseHemicellulosesProteinsRecalcitrantCutinsSuberinsHighly-recalcitrantLigninsTanninsCutansSuberansComponentsofSOM?土壤腐殖物質(zhì)腐殖物質(zhì)分組----胡敏素殘?jiān)羲岷稚恋砀焕锼狳S色溶液酸化溶液----HCl土壤樣品NaOH浸提表土壤有機(jī)碳的不同組分及特性土壤有機(jī)碳組分占土壤碳比例（%）周轉(zhuǎn)時(shí)間舉例微生物量碳2-8幾個(gè)月-幾年土壤微生物量碳及微生物代謝產(chǎn)物周轉(zhuǎn)慢的碳40-5520-50年穩(wěn)定的微生物代謝產(chǎn)物，難分解的植物殘?bào)w惰性碳40-50400-2000年土壤腐殖質(zhì)LabilepoolStabilizedpoolParticulateorganicmatter(POM)MicrobialbiomassCSolubleCPotentialmineralizableCHumicsubstancesThelabilefractionconsistsofmaterialintransitionbetweenfreshplantresiduesandstabilizedorganicmatterParticulateorganicmattercanbeseparatedfromsoilsbytwodistinctmethodsresultingintwodifferentterms:lightfraction(LF)organicmatterandsand-sizedfraction(SSF)organicmatter.floatonheavyliquidsofdensitiestypicallybetween1.5and2.0g/cm3.(NaI,1.7g/cm3)LForganicmatterSSForganicmatterdefinedasorganicmatterassociatedwithsand-sizedorganicmatter(>20μmdiameterforEuropeanand>53μmdiameterforAmericanparticlesizeclassificationsystems).Itisisolatedbysievingadispersedsoil.HaynesRJ.AdvancesinAgronomy,2005MicrobialbiomassFigSchematicdiagramshowingtherelationshipbetweenvariousorganicmatterfractionsSolubleorganicmatterParticulateorganicmatterExtractableorganicmatterRootturnoverCropresiduesPotentiallymineralizableorganicmatterAdsorbedorganicmatterHumicmaterialTableTypicalquantitiesofdifferentorganicmatterfractionsinsoilsOrganicfractionTypicalquantitiesTotalorganicCandNOrganicC=7-60gC/kgParticulateorganicmatterLF=2-18%oforganicC,1-16%oftotalNSSF=20-45%oforganicC,13-40%oftotalNMicrobialbiomass1-5%oforganicCand1-6%oftotalNSolubleorganicmatterAbout0.05-0.40%oforganicCandNExtractableorganicCandNVariableamountoforganicC(1-40%)dependingontheextractantPotentiallymineralizableCandNAbout1-5%oforganicCandtotalNHaynesRJ.AdvancesinAgronomy,2005Meanresidencetime(MRT)ofsoilorganicmatterThetermmeanresidencetimehasbeenusedtoexpresstheresultsof14Cmeasurementsfortheaverageageofmodernhumus.14CdatingmethodStevensonFJ.CyclesofSoil.1986,pp-31Theformularelatingtoageto14CactivityiswhereAisthenumberofradioactivenucleiremainingaftertimeintervalt,A0isthenumberofradioactivenucleipresentatzerotime,tistimeoragesincezerotime,andt1/2isthehalf-lifeofradioactivenuclide.TableMeanresidencetime(MRT)fordifferentorganicmatterfractionsofaChernozemicblacksoilStevensonFJ.CyclesofSoil.1986,pp-31ComponentMRT,yearsUnfractionatedsoil870±50Acidextractofsoil325±60Fulvicacid495±60Humicacidtotalsample1235±60acidhydrolysate25±50nonhydrolyzable1400±60Humintotalsample1140±50acidhydrolysate465±50nonhydrolyzable1230±60RecentanalyticalandexperimentaladvanceshavedemonstratedthatmolecularstructurealonedoesnotcontrolSOMstability:infact,environmentalandbiologicalcontrolspredominate.StevensonFJ.CyclesofSoil.1986,pp-31Wearguethatthepersistenceoforganicmatterinsoilislargelyduetocomplexinteractionsbetweenorganicmatteranditsenvironment,suchastheinterdependenceofcompoundchemistry,reactivemineralsurfaces,climate,wateravailability,soilacidity,soilredoxstateandthepresenceofpotentialdegradersintheimmediatemicroenvironment.SchmidtMW,etal.2011.Persistenceofsoilorganicmatterasanecosystemproperty.NATURE,478:49-56InorganicCinsoil(SIC)Intheformofcalciumandmagnesiumcarbonates,estimatedtototalsome695to748billiontons,presentmainlyinthesoilsofsemiaridandaridareas.Thoughnotnearlyaslabileasorganiccarbon,SICcanbesolubilizedbyacidandissubjecttoleaching.Somecarbondioxidealsodissolvesingroundwater,andmaybereleasedtotheatmospherebyeffervescenceas,forexample,whengroundwaterispumpedupandusedforirrigation(DanielHill.SoilintheEnvironment,2008).塿土剖面有機(jī)碳及無(wú)機(jī)碳含量圖加入碳酸鈣及碳酸鎂對(duì)土壤培養(yǎng)過(guò)程中CO2釋放的影響（董燕婕，2010）碳酸鈣碳酸鎂CO2emissionfromsoilOrganicCpoolinsoilInorganicCpoolinsoilBioticabiotic×Sterilizer:HgCl2UsingsolidHgCl2asasterilizertosterilizetheCO2productionfrombioticprocess.Fig5aEffectofCaCO3andHgCl2additionsonCO2emissionfromsoilpH=7.4pH=7.9ForMgCO3Fig5bTheeffectofMgCO3andHgCl2additionsonsoilCO2emissionHowcanwedifferentiatethecontributionofinorganiccarbonandorganiccarbontoCO2release?Fig.1.IllustrationofthemainstoresandflowsofCinacropland,showingthreepoolsofsoilCforsimplicity,thoughrecognizingthatsoilCspansacontinuumofforms.(Janzen,2006,SBB)4.土壤碳庫(kù)的調(diào)節(jié)Soilorganiccarboncontentisafunctionofthebalancebetweentherateoforganicmatterinputtothesoil(duetonetprimaryproductivityofactivevegetation)andtherateoforganicmatterdecay.Theratesoftheseprocessesdifferinspaceandtime,aswellasintheirsensitivitiestovaryingtemperatureandmoistureregimesresultingfrommanagementandclimatechanges.Cinsoil=f(climate,topography,vegetationandorganisms,parentmaterial,ageortime)Theamountoforganicmatterinsoildependsontheinputoforganicmaterial,itsrateofdecomposition,therateatwhichexistingsoilorganicmatterismineralized,soiltexture,andclimate.HaynesRJ.AdvancesinAgronomy,2005LabileCFigAschematicdiagramoftheCcycleinagriculturalsoilsStabilizedCPlantCCO2HarvestedCLitterdecompositionDecompositionNetprimaryproductionAtmosphericCpool(760Pg)TerrestrialCpool2860PgSOC=1550PgSIC=750PgBiota=560PgFigure1.AnthropogenicactivitiesaffectingCemissionfromtheterrestrialtotheatmosphericpool.ThedirectionofthearrowindicatesthefluxofCfromonepooltoanother.Photosynthesisandplant/soilrespirationarenaturalactivities.AllothersareanthropogenicactivitiesthatcauseemissionofCO2andothergasesfromtheterrestrialecosystemtotheatmosphere.Themagnitudeofemissioncausedbyallanthropogenicactivitiesisnotknown.(Lal.NutrientCyclinginAgroecosystems70:103–116,2004.)PhotosynthesisPlantandsoilrespirationAnthropogenicactivitiesDeforestation(1.6±0.8Pg)ConversionofnaturalintoagriculturalecosystemsBiomassburningSoiltillageDrainageofwetlandSoilerosion(1.1PgCy-1)CultivationoforganicsoilGlobalterrestrialecosystemsabsorbedcarbonatarateof1–4Pg/yrduringthe1980sand1990s,offsetting10–60percentofthefossil-fuelemissions.ShilongPiao,JingyunFang,etal.2009.ThecarbonbalanceofterrestrialecosystemsinChina.Nature,458:1009-1014.潘根興.氣候變化研究進(jìn)展