植物營養(yǎng)元素的土壤化學(xué)3--土壤中的C(上)

1、第二章土壤碳素循環(huán)及調(diào)控第二章土壤碳素循環(huán)及調(diào)控Chapter 2 Carbon cycles in SoilLow carbon economyGHGs = greenhouse gasesIPCC= Intergovernmental Panel on Climate Change （政府間氣候變化專業(yè)委員會政府間氣候變化專業(yè)委員會）“哥本哈根氣候會議哥本哈根氣候會議”Fig. Deviations from recent exponential increases in fossil fuel burning(Bacastow & Keeling, 1974)The indust

2、rial revolution, which started around 1750, driven by cheap and easy access to modern energy through fossil fuel combustion, led to mass production of modern amenities at low cost. Indeed all availed amenities by industrialized societies are based on fossil fuel derived energy. Thus, the modern civi

3、lization can be appropriately termed “the Carbon Civilization” or the C-Era (Lal, 2007), as compared with the historic hydric civilizations, which thrived in the valleys of Tigris, Euphrates, Nile, Indus, Huang etc. Indeed, the world energy consumption increased 40 times between 1850 and 2005.The at

4、mospheric concentration of CO2 has increased from 280 ppmv since the late 1700s to about 380 ppmv in 2006, is presently increasing at the rate of 1.8 ppmv yr1 or 0.47% yr1 (WMO, 2006.)政府間氣候變化專門委員會政府間氣候變化專門委員會(IPCC)第三次第三次評估報告（評估報告（2001）q 二十世紀全球平均氣溫上升二十世紀全球平均氣溫上升0.60.6 0.20.2 C;C;q 從從18611861年以來，二十世紀九

5、十年代是最熱的年以來，二十世紀九十年代是最熱的1010年，其中，年，其中，19981998年是最熱的一年年是最熱的一年; ;q 在過去的一千年中，二十世紀是最熱的一個世紀在過去的一千年中，二十世紀是最熱的一個世紀; ;q 從從19501950年到年到19931993年，陸地夜間日平均氣溫每年，陸地夜間日平均氣溫每1010年升高約年升高約0.20.2 C C，白天升高約，白天升高約0.10.1 C C。海面氣溫升高約為陸地的一半。海面氣溫升高約為陸地的一半. .q海平面上升；q降水分布發(fā)生變化；q沙漠化加劇；q自然災(zāi)害發(fā)生頻繁增加。 全球變暖的后果?Human population Size R

6、esource useHuman enterprises Agriculture Industry Recreation International commerceLand transformation Land clearingForestryGrazing IntensificationBiotic additions and losses InvasionHuntingFishingGlobal biogeochemistry CarbonNitrogenWaterSynthetic chemicalsOther elementsClimate change Enhanced gree

7、nhouseAerosolsLand coverLoss of biological diversity Extinction of species and populationsLoss of ecosystemsq改進能源結(jié)構(gòu)q提高能源效率q植樹種草，增加生態(tài)系統(tǒng)對CO2的吸收如何減少溫室效應(yīng)氣體的排放?C sequestration (碳固定碳固定)Carbon sequestration implies the net removal of CO2 from the atmosphere into long-lived pools of C, such as terrestrial a

8、nd geologic. In other words, it is capturing and securely storing C by biotic photosynthesis and abiotic injection into geologic strata or ocean processes.Lal R. Soil Sci. Soc. Am. J. 2007, 71:14251437Carbon sequestration19971997年年1212月，面對環(huán)境惡化，氣候變暖，在日本京都舉行的聯(lián)月，面對環(huán)境惡化，氣候變暖，在日本京都舉行的聯(lián)合國氣候大會通過了合國氣候大會通過了京

9、都議定書京都議定書，目標是在，目標是在20082008年至年至20122012年間，將發(fā)達國家年間，將發(fā)達國家COCO2 2等種溫室氣體的排放量在等種溫室氣體的排放量在19901990年的基年的基礎(chǔ)上平均削減礎(chǔ)上平均削減5.25.2。為了使議定書真正發(fā)揮作用，協(xié)議規(guī)定，只有在占為了使議定書真正發(fā)揮作用，協(xié)議規(guī)定，只有在占19901990年全球年全球溫室氣體排放量溫室氣體排放量5555以上的至少以上的至少5555個國家批準后才能生效。個國家批準后才能生效。The industrial emissions of carbon (C) in China are about 1 Pg yr-1, se

10、cond only to the United States estimated at 1.84 Pg yr-1 for 2000. Because of the differences in population, however, the per capita emission is 0.08 Tg per 100 000 inhabitants in China compared with 0.55 Tg per 100 000 inhabitants in the United States (NET, 1998). With its rapidly increasing econom

11、y, however, China may surpass the United States as the worlds largest emitter of C by 2020.Lal R. Land Degrad. Develop. 13: 469478 (2002)我國我國20012001年的工業(yè)年的工業(yè)COCO2 2排放為排放為1Pg/yr1Pg/yr，僅次于美國（，僅次于美國（1.84Pg/yr1.84Pg/yr），預(yù)計在），預(yù)計在20052005年會超過美國年會超過美國, ,達到達到2Pg/yr2Pg/yr，我國面臨著減排的巨大壓力。我國面臨著減排的巨大壓力。這是一個關(guān)系國家環(huán)境

12、外交和農(nóng)業(yè)可持續(xù)發(fā)展的食物安這是一個關(guān)系國家環(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題。全與環(huán)境安全保障的重大問題。黃耀黃耀. 第四紀研究第四紀研究. 2006按照按照IPCC第第2次評估報告提供的全球增溫潛勢數(shù)據(jù)計次評估報告提供的全球增溫潛勢數(shù)據(jù)計算算, 1994年中國溫室氣體總排放量為年中國溫室氣體總排放量為36.50108 t CO2當量當量,其中其中CO2 , CH4和和N2O分別占分別占73.1%, 19.7%和和7.2%。能源活動是中國能源活動是中國CO2排放的主要來源排放的主要來源,占占90.95%；農(nóng)；農(nóng)業(yè)活動和能源活動是業(yè)活動和能源活動是CH4排放的主要來源，

13、分別占排放的主要來源，分別占50.15%和和27.33%；農(nóng)業(yè)活動是；農(nóng)業(yè)活動是N2O排放的主要來源排放的主要來源,占占92.4%。About 20% of the global emission presently come from land use change (IPCC, 2001)Agricultures Contribution to Climate Change Stern ReviewAgriculture = 14% of global GHGs Land use (deforestation) = 18% of global GHGsSource: Stern Revie

14、w: the Economics of Climate ChangeAgricultures Contribution to Climate Change Stern Review38%38%13%11%Global sources of non-CO2 emissions from the agriculture sector (2000)Source: Stern Review: the Economics of Climate ChangeHillel D. 2008Agriculture accounts for a sizable share of non-CO2 emissions

15、, including an estimated 47% of CH4 and as much as 84% of N2O.UK Agriculture -Some Key Factsu Only 0.5% of GDP (agri-food sector 7%)u 1.7% of employment (agri-food 14%)u Manages 70% of Englands land (80% of rural land), with huge benefits for landscape, biodiversity and accessu But contributes 7% of

16、 the UKs GHG emissions (37% of methane, 63% of nitrous oxide)andu Majority of nitrate emissions to water and ammonia emissions to airJeremy Eppel, Deputy Director, Food & Farming Group, Defra全球氣候變化簡史全球氣候變化簡史不同的聲音.“氣候變化問題的非主流思考：事實與邏輯氣候變化問題的非主流思考：事實與邏輯”, ,科學(xué)時報科學(xué)時報,2009,2009年年8 8月月1111“哥本哈根鬧劇后的沉思哥本

17、哈根鬧劇后的沉思”, ,科學(xué)時報科學(xué)時報,2010-02-11,2010-02-11氣候問題的氣候問題的“郵件門郵件門” (2009(2009年年1111月月) ) 英國東英吉利大學(xué)氣候研究中心上千封電子郵件和英國東英吉利大學(xué)氣候研究中心上千封電子郵件和30003000多多份有關(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)家利用各國政府對氣候變化問題的關(guān)心，用一些不實數(shù)學(xué)家利用各國政府對氣候變化問題的關(guān)心，用一些不實數(shù)據(jù)制造氣候變暖的假象，營造恐慌心理，然后從政府或其據(jù)制造氣候變暖的假象，營造恐慌心理，然后從政府或其他機構(gòu)手中騙得了更多的科研

18、經(jīng)費。他機構(gòu)手中騙得了更多的科研經(jīng)費。氣候問題的氣候問題的“冰川門冰川門”事件事件IPCCIPCC在在20072007年發(fā)布的第四次評估報告中寫道年發(fā)布的第四次評估報告中寫道 “喜馬拉雅喜馬拉雅冰川的消融速度超過了世界其他地區(qū)的冰川，如果全球變冰川的消融速度超過了世界其他地區(qū)的冰川，如果全球變暖的速度持續(xù)下去，喜馬拉雅冰川在暖的速度持續(xù)下去，喜馬拉雅冰川在20352035年甚至更早前消年甚至更早前消失的可能性非常高失的可能性非常高”?？陀^對待客觀對待IPCCIPCC的報告的報告美國美國250250余名科學(xué)家聯(lián)名上書呼吁不要指責(zé)余名科學(xué)家聯(lián)名上書呼吁不要指責(zé)IPCCIPCC荷蘭荷蘭250250余

19、名科學(xué)家聯(lián)名余名科學(xué)家聯(lián)名問題與對策:我國已成為全球最大的溫室效應(yīng)氣體排放國，面臨著減我國已成為全球最大的溫室效應(yīng)氣體排放國，面臨著減排的巨大壓力。排的巨大壓力。丁仲禮丁仲禮, , 段曉男段曉男, , 葛全勝葛全勝, , 張志強張志強. 2050. 2050年大氣年大氣COCO2 2濃度濃度控制控制: : 各國排放權(quán)計算各國排放權(quán)計算. .中國科學(xué)，中國科學(xué)，D D輯，輯，20092009，39(8):1009-102739(8):1009-1027文章提出了文章提出了“人均累計排放指標人均累計排放指標”的概念，以體現(xiàn)的概念，以體現(xiàn)“共同而有區(qū)別共同而有區(qū)別的責(zé)任的責(zé)任”原則和公平正義準則。設(shè)

20、定原則和公平正義準則。設(shè)定20502050年前將大氣年前將大氣COCO2 2濃度控制在濃度控制在470 ppmv470 ppmv的目標的目標, , 以以19001900年為時間起點年為時間起點, , 對各國過去對各國過去(1900-2005(1900-2005年年) )人均累計排放量、應(yīng)得排放配額以及今后人均累計排放量、應(yīng)得排放配額以及今后(2006-2050(2006-2050年年) )的排放配額的排放配額做了逐年計算做了逐年計算. .1.全球碳循環(huán)概況2.土壤碳庫在全球碳循環(huán)中的作用3.土壤碳的不同組分及其特性4.土壤碳庫的調(diào)節(jié)Table Distribution of C in some

21、 of the main compartments in the earth (Delwiche)CompartmentAmount of C, 1012 kgAtmosphere700Soil organic matter (to 2 m depth)2500Land life forms480Marine humus3000Ocean life forms50Dissolved carbonate-bicarbonate in oceans3840Coal and petroleum1 104 Sediments6 107 Stevenson FJ, 1986(1)全球碳分布全球碳分布1.

22、全球碳循環(huán)概況全球碳循環(huán)概況Fig The carbon cycle (Numbers are storage as 1015 g or fluxes as 1015 g per year)Ecology, Manuel CM, 2002 為了維持全球碳平衡，其焦點不是各個庫的碳貯為了維持全球碳平衡，其焦點不是各個庫的碳貯存總量，而是每年碳的去處和動態(tài)變化問題。存總量，而是每年碳的去處和動態(tài)變化問題?！霸丛础迸c與“匯匯” (source and sink)把釋放二氧化碳的庫稱為把釋放二氧化碳的庫稱為“源源”，吸收二氧化碳的庫稱為，吸收二氧化碳的庫稱為“匯匯”。Paul EA, 2007(2)全

23、球碳循環(huán)全球碳循環(huán) SoilOceanBiotaAtmosphereTerrestrial photosynthesisRiver transport of organic matter and carbonatesRespirationCarbonate inputCO2 exchangeLitter and root inputCalcificationMarine respirationMarine photosynthesisThe short-term C cycle人為因素對碳循環(huán)的干擾作用人為因素對碳循環(huán)的干擾作用(單位單位Pg/年）年）大氣大氣土地土地海洋海洋沉積物沉積物礦質(zhì)有

24、礦質(zhì)有機碳機碳碳酸鹽碳酸鹽地質(zhì)庫地質(zhì)庫5.4礦質(zhì)燃料燃燒礦質(zhì)燃料燃燒 5.35.3水泥生產(chǎn)水泥生產(chǎn)0.1土地利用變化土地利用變化1.7土地吸收土地吸收1.9海洋吸收海洋吸收1.9Post WM, et al., BioScience 2004，54(10)Fig. 1. Illustration of the main stores and flows of C in a cropland, showing three pools of soil C for simplicity, though recognizing that soil C spans a continuum of form

25、s. (Janzen, 2006, SBB)2. 土壤碳庫在全球碳轉(zhuǎn)化及循環(huán)中的地位土壤碳庫在全球碳轉(zhuǎn)化及循環(huán)中的地位Lal R. Science, 2004The global soil carbon (C) pool of 2500 gigatons (Gt) includes about 1550 Gt of soil organic carbon (SOC) and 950 Gt of soil inorganic carbon (SIC). The soil C pool is 3.3 times the size of the atmospheric pool (760 Gt) a

26、nd 4.5 times the size of the biotic pool (560Gt).(1) 土壤碳庫的意義土壤碳庫的意義Atmospheric C pool (760 Pg)Terrestrial C pool 2860 Pg SOC=1550 Pg (to 1 m depth) SIC=750 Pg Biota=560 PgFigure 1. Cycle of C in terrestrial ecosystem and the atmosphere. PhotosynthesisPlant and soil respirationLal R. Science. 2004, 3

27、04土壤碳庫的穩(wěn)定、增長或釋放與大氣庫的變化土壤碳庫的穩(wěn)定、增長或釋放與大氣庫的變化有重要的關(guān)系，土壤能否增加碳儲存是關(guān)乎陸有重要的關(guān)系，土壤能否增加碳儲存是關(guān)乎陸地生態(tài)系統(tǒng)凈碳匯飽和問題的重要理論基礎(chǔ)，地生態(tài)系統(tǒng)凈碳匯飽和問題的重要理論基礎(chǔ)，這一問題已成為土壤與全球變化研究的重點和這一問題已成為土壤與全球變化研究的重點和熱點科學(xué)問題。熱點科學(xué)問題。Sequestration of C in soils is often seen as a win-win proposition; it not only removes excess CO2 from the air, but also im

28、proves soils by augmenting organic matter, an energy and nutrient source for biota.Lal R. Soil Sci. Soc. Am. J. 2007, 71:14251437Lal R. Soil Sci. Soc. Am. J. 2007, 71:14251437土壤的土壤的“C sinks”、“C sequestration”、“C storage”、“C stabilization”及及“C storing capacity”(2) 土壤碳貯量土壤碳貯量 (C storage)土壤碳貯量的計算？土壤碳貯量

29、的計算？土壤碳貯量土壤碳貯量= =土壤容重土壤容重土壤有機碳含量土壤有機碳含量土壤體積土壤體積Soil organic carbon=1550 PgSoil inorganic carbon=750 PgYu, D., et al., Regional patterns of soil organic carbon stocks in China. Journal of Environmental Management (2006),Yu, D., et al., Regional patterns of soil organic carbon stocks in China. Journal

30、 of Environmental Management (2006),Soils in China cover an area of 9.281106km2 in total, with a total SOC stock of 89.14 Pg (1 Pg =1015 g) and a mean SOC density of 96.0 t C/ha.中國是世界上平均土壤碳密度較低的國家。中國是世界上平均土壤碳密度較低的國家。全球全土碳密度平均為全球全土碳密度平均為121 t/hm121 t/hm2 2，我國全土平均，我國全土平均有機碳密度的報道值介于有機碳密度的報道值介于8080105 t

31、/hm105 t/hm2 2，均遠遠，均遠遠低于世界平均值。低于世界平均值。表表 中國和歐洲表層土壤有機碳密度比較中國和歐洲表層土壤有機碳密度比較(tC/ha)土地利用歐洲中國土地總計70.852.0耕地53.037.0潘根興，趙其國潘根興，趙其國. .地球科學(xué)進展地球科學(xué)進展. 2005. 2005不同土地利用方式對土壤剖面碳貯量的影響不同土地利用方式對土壤剖面碳貯量的影響Table Land-use effects on density of organic carbon (kg/m2) in 416 soil profiles of eastern China (adapted from

32、 Cai,1995)HorizonNatural vegetationFuel forestUpland fieldsPaddy fieldsA5.402.171.312.40B6.582.680.921.44C2.271.671.642.94Total14.256.523.876.78Land Degradation & Development, 2002, 13:469-478u植物體組成及分解轉(zhuǎn)化特性植物體組成及分解轉(zhuǎn)化特性u土壤有機碳的組分及特性土壤有機碳的組分及特性u土壤有機碳穩(wěn)定性的機理土壤有機碳穩(wěn)定性的機理3.3.土壤碳的不同組分及其特性土壤碳的不同組分及其特性Plant

33、 litter as the principle source of soil organic matter formationPlants are the main source of carbon to soils through tissue residues or via root exudates and symbiotic fungi.陳興麗等陳興麗等表1黃土高原幾種植物殘體的化學(xué)成分植物殘體有機碳CTOC (gkg-1) 全氮NTotal N (gkg-1) C/NRatios 木質(zhì)素(%) 喬木A榆樹422.5825.36 16.66 25.20 B小葉楊414.449.02

34、45.9730.89 C刺槐437.73 14.9229.33 27.78灌木D檸條466.85 30.95 15.08 29.59E沙棘464.70 29.7115.64 27.14 F山桃458.53 28.29 16.2125.76 草本G長芒草499.46 9.86 50.6727.54 H白羊草432.69 6.6165.4928.61I沙打旺427.93 27.0115.84 24.10J紫花苜蓿464.9832.78 14.1924.47 (C6H10O5)n+nH2O nC6H12O6C6H12O6 +6O2 6CO2+6H2O+能量 在通氣不良的情況下，可形成中間產(chǎn)物有機酸（

35、丁酸）和甲烷、氫氣C6H12O6 CH3CH2CH2COOH+2H2+2CO2+能量4H2+CO2 CH4+2H2O 碳水化合物的礦化碳水化合物的礦化有機物質(zhì)的礦化有機物質(zhì)的礦化腐殖物質(zhì)形成的生物學(xué)示意圖腐殖物質(zhì)形成的生物學(xué)示意圖 植物殘體 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 類木質(zhì)素 醌 醌 腐殖物質(zhì) 1234First stage:Stevenson FJ, 1986Stages in the microbial decompositionDecay of easily degradable substances. Partial conversion to CO2

36、and body tissueSecond stage:Third stage:Fourth and successive stage:Cellulose and other carbohydrates utilized with further weight reduction. Formation of new body tissue. Part of previous biomass mineralized. Further decrease in cellulose. Initiation of lignin decomposition. Further decrease in bio

37、mass. Further cycling. For plant residues, about one-third of the carbon will remain in the soil at the end of the growing season. 陳興麗等陳興麗等圖圖1 1 黃土高原不同植物殘體碳的礦化率黃土高原不同植物殘體碳的礦化率C/NA A榆樹榆樹16.66 B B小葉楊小葉楊45.97C C刺槐刺槐29.33 D D檸條檸條15.08 E E沙棘沙棘15.64 F F山桃山桃16.21G G長芒草長芒草50.67H H白羊草白羊草65.49I I沙打旺沙打旺15.84 J

38、 J紫花苜蓿紫花苜蓿14.19Fig. Influence of leaf toughness and nitrogen content on decomposition (Gallardo & Merino, 1993)Nitrogen most often controls the rate of organic matter decomposition. (C/N ratio)圖1 土壤植物生態(tài)系統(tǒng)中的碳、氮素轉(zhuǎn)化過程示意圖 不同不同C/NC/N比的植比的植物殘體等物殘體等土壤微生物量部分穩(wěn)定的有機氮 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

39、作物吸收CO2等釋放土壤中氮、碳協(xié)調(diào)是關(guān)鍵！土壤中氮、碳協(xié)調(diào)是關(guān)鍵！有機物施入土壤的去向（1年后）：有機殘體有機殘體（100100）COCO2 2（60-80%60-80%）土壤生物體土壤生物體（3-8%3-8%）非腐殖物質(zhì)非腐殖物質(zhì)（多糖、有機酸等）（多糖、有機酸等）（3-8%3-8%）腐殖物質(zhì)腐殖物質(zhì)（10-30%10-30%）腐殖質(zhì)Soils in our Environment.1995Table The decomposition of the different components in the mixture of residues from pine and oakOrigi

40、nal litterPortion of whole(%)Percentage lost by decomposition by:1st year2nd year5th year10th yearSugars1599100-Cellulose2090100-Hemicelluloses157592100-Lignins40507497100Waxes525437795Phenols510204370Whole litter matters55.179.687.198.2Stevenson FJ. Cycles of Soil. 1986, pp-31Table Carbon retained

41、from 14C-labeled plant material applied to field soilsLocationTypeCarbon retained (%)RefereceRothmasted, EnglandRyegrass tops and rootApproximately 33% of first year irrespective of soil type or plant materialJenkinsonWest GermanyWheat straw and chaff31% after first year for fallow and cropped soilI

42、AEAAustriaMaize47% after first year when applied in August and 33% when applied in OctoberIAEASaskatchewan, CanadaWheat straw35-45% after first growing seasonShields and PaulColorado, USABlue grama a. herbage b. Roots43-46% after 412 days63-74% after 412 daysNyhanNigeriaRyegrass20% after first year

43、and 14% after two years.Jenkonson & Ayanaba通氣性狀況對土壤有機質(zhì)含量的影響通氣淹水土壤黏粒含量對有機質(zhì)含量的影響水分狀況對植物體分解的影響Fig Decomposition of Fraxinus leaves at wetter and drier sites (Gallardo & Merino, 1993)Science, 1997, 277:504-509Paul EA, 2007Soluble in polar solventsNon-hydrolyzable/soluble in polar solventsHydroly

44、zableSoil organic matter (SOM)Not recalcitrantCelluloseHemicellulosesProteinsRecalcitrantCutinsSuberinsHighly-recalcitrantLigninsTanninsCutansSuberansComponents of SOM?土壤腐殖物質(zhì)土壤腐殖物質(zhì)腐殖物質(zhì)分組腐殖物質(zhì)分組- - - - -胡敏素胡敏素殘渣殘渣胡敏酸胡敏酸褐色沉淀褐色沉淀富里酸富里酸黃色溶液黃色溶液酸化酸化溶液溶液- - - - -HClHCl土壤樣品土壤樣品 NaOHNaOH浸提浸提表表 土壤有機碳的不同組分及特性土

45、壤有機碳的不同組分及特性土壤有機碳土壤有機碳組分組分占土壤占土壤碳比例碳比例（%）周轉(zhuǎn)時間周轉(zhuǎn)時間舉舉 例例微生物量碳微生物量碳2-8幾個月幾個月-幾年幾年土壤微生物量碳及微生物土壤微生物量碳及微生物代謝產(chǎn)物代謝產(chǎn)物周轉(zhuǎn)慢的碳周轉(zhuǎn)慢的碳40-5520-50年年穩(wěn)定的微生物代謝產(chǎn)物，穩(wěn)定的微生物代謝產(chǎn)物，難分解的植物殘體難分解的植物殘體惰性碳惰性碳40-50400-2000年年土壤腐殖質(zhì)土壤腐殖質(zhì)Labile poolStabilized poolParticulate organic matter (POM)Microbial biomass CSoluble CPotential miner

46、alizable CHumic substancesThe labile fraction consists of material in transition between fresh plant residues and stabilized organic matterParticulate organic matter can be separated from soils by two distinct methods resulting in two different terms: light fraction (LF) organic matter and sand-size

47、d fraction (SSF) organic matter.float on heavy liquids of densities typically between 1.5 and 2.0 g/cm3. (NaI, 1.7 g/cm3) LF organic matterSSF organic matterdefined as organic matter associated with sand-sized organic matter (20 m diameter for European and 53 m diameter for American particle size cl

48、assification systems). It is isolated by sieving a dispersed soil.Haynes RJ. Advances in Agronomy, 2005Microbial biomassFig Schematic diagram showing the relationship between various organic matter fractionsSoluble organic matterParticulate organic matterExtractable organic matterRoot turnoverCrop r

49、esiduesPotentially mineralizable organic matterAdsorbed organic matterHumic materialTable Typical quantities of different organic matter fractions in soilsOrganic fractionTypical quantitiesTotal organic C and NOrganic C = 7-60 gC/kgParticulate organic matterLF=2-18% of organic C, 1-16% of total NSSF

50、=20-45% of organic C, 13-40% of total NMicrobial biomass1-5% of organic C and 1-6% of total NSoluble organic matterAbout 0.05-0.40% of organic C and NExtractable organic C and NVariable amount of organic C (1-40%) depending on the extractantPotentially mineralizable C and NAbout 1-5% of organic C an

51、d total NHaynes RJ. Advances in Agronomy, 2005Mean residence time (MRT) of soil organic matterThe term mean residence time has been used to express the results of 14C measurements for the average age of modern humus.14C dating methodStevenson FJ. Cycles of Soil. 1986, pp-31The formula relating to ag

52、e to 14C activity is01 / 2lo g 2lo glo gAAttwhere A is the number of radioactive nuclei remaining after time interval t, A0 is the number of radioactive nuclei present at zero time, t is time or age since zero time, and t1/2 is the half-life of radioactive nuclide. Table Mean residence time (MRT) fo

53、r different organic matter fractions of a Chernozemic black soilStevenson FJ. Cycles of Soil. 1986, pp-31ComponentMRT, yearsUnfractionated soil87050Acid extract of soil32560Fulvic acid49560Humic acid total sample123560 acid hydrolysate2550 nonhydrolyzable140060Humin total sample114050 acid hydrolysa

54、te46550 nonhydrolyzable123060Recent analytical and experimental advances have demonstrated that molecular structure alone does not control SOM stability: in fact, environmental and biological controls predominate.Stevenson FJ. Cycles of Soil. 1986, pp-31We argue that the persistence of organic matte

55、r in soil is largely due to complex interactions between organic matter and its environment, such as the interdependence of compound chemistry, reactive mineral surfaces, climate, water availability, soil acidity, soil redox state and the presence of potential degraders in the immediate microenviron

56、ment.Schmidt MW, et al. 2011. Persistence of soil organic matter as anecosystem property. NATURE, 478: 49-56Inorganic C in soil (SIC)In the form of calcium and magnesium carbonates, estimated to total some 695 to 748 billion tons, present mainly in the soils of semiarid and arid areas.Though not nea

57、rly as labile as organic carbon, SIC can be solubilized by acid and is subject to leaching. Some carbon dioxide also dissolves in groundwater, and may be released to the atmosphere by effervescence as, for example, when groundwater is pumped up and used for irrigation (Daniel Hill. Soil in the Envir

58、onment, 2008).塿土剖面有機碳及無機碳含量塿土剖面有機碳及無機碳含量圖 加入碳酸鈣及碳酸鎂對土壤培養(yǎng)過程中CO2釋放的影響 （董燕婕，2010）碳酸鈣碳酸鎂CO2 emission from soilOrganic C pool in soilInorganic C pool in soilBioticabioticSterilizer: HgCl2 Using solid HgCl2 as a sterilizer to sterilize the CO2 production from biotic process.Fig 5a Effect of CaCO3 and HgCl

59、2 additions on CO2 emission from soilpH= 7.4pH=7.9For MgCO3Fig 5b The effect of MgCO3 and HgCl2 additions on soil CO2 emissionHow can we differentiate the contribution of inorganic carbon and organic carbon to CO2 release?Fig. 1. Illustration of the main stores and flows of C in a cropland, showing

60、three pools of soil C for simplicity, though recognizing that soil C spans a continuum of forms. (Janzen, 2006, SBB)4. 土壤碳庫的調(diào)節(jié)土壤碳庫的調(diào)節(jié)Soil organic carbon content is a function of the balance between the rate of organic matter input to the soil (due to net primary productivity of active vegetation) and the rate of organic