高原喀斯特土壤有机碳短期稳定的温度作用机制
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摘要
探明有机碳稳定的温度作用机制,是评估全球变化背景下土壤碳源/汇演变趋势的关键.应用土壤密度分组和酸水解技术,采用红外线辐射增温法,对比研究不同升温情景下高原喀斯特土壤及其物理和生化组分中有机碳密度的短期(4a)变化特征.升温情景包括不升温(对照)、对称升温(全年同步升温2.0℃)和非对称升温(冬春/夏秋季升温幅度为2.5℃/1.5℃、3.0℃/1.0℃、3.5℃/0.5℃和4.0℃/0℃,低度、中度、高度和极端非对称升温),其中中度非对称升温与该区域多年升温情景类似.结果表明,不同升温情景下表层(0~15 cm)土壤有机碳密度在1.95~2.02 kg·m-2之间,其差异不显著,且与对照(1.94 kg·m-2)差异不显著.升温处理间土壤轻组和重组碳密度、重组顽固性碳密度差异不显著,且与对照差异不显著.5个升温处理轻组顽固性碳平均密度是对照的1.18倍,其中对称升温、低度和中度非对称升温处理显著高于对照.轻组顽固性碳密度和轻组顽固性碳指数随升温的非对称性增加而降低,其中对称升温处理均显著高于中度、高度和极端非对称升温.亚表层(15~30 cm)土壤及其物理和生化组分中有机碳密度对短期升温均不敏感.研究揭示:短期内,升温提高了高原喀斯特土壤非保护组分中有机碳顽固性.基于对称升温情景并不一定会误估全球变暖对土壤有机碳数量和土壤碳物理保护能力的影响,但可能会高估表层土壤(0~15 cm)非保护组分有机碳顽固性.
Elucidating the mechanisms of warming-induced stability for soil organic C is one of the keys for evaluating the tendency of soil C sources/sinks in projected global warming models. Organic C densities in soil,and soil physical and biochemical fractions,under different warming scenarios in the Karst Plateau were investigated following a 4-yr continuous warming using infrared radiators,via density fractionation and acid hydrolysis. Six treatments were arranged: no warming( ambient temp,CK); symmetric warming( ambient + 2. 0℃ full year); and lowly,moderately,highly,and extremely asymmetric warming( ambient + 2. 5℃/1. 5℃,3. 0℃/1. 0℃,3. 5℃/0. 5℃,and 4. 0℃/0℃ in winter-spring/summer-autumn seasons,respectively; LAW,MAW,HAW,and EAW).The moderately asymmetric warming was highly similar to a multi-year warming scenario in the study region. The results showed there were no significant differences in soil organic C densities in the surface layer( 0-15 cm) among the warming treatments,with a range of 1. 95 kg·m-2 to 2. 02 kg·m-2,which is insignificantly different to the CK( 1. 94 kg·m-2). There were no significant differences in the C density of light and heavy fractions,and the recalcitrant heavy-fraction among the warming treatments,and between the warming and no warming treatments. The average recalcitrant C density of the light fraction in the warming treatments was 1. 18 times higher than the CK,with a significantly higher recalcitrant C density of the light fraction in the symmetric warming,and lowly and moderately asymmetric warming treatments,compared to that of the CK. The recalcitrant C density and recalcitrant C index of the light fraction showed a tendency to decrease as the asymmetry of warming increased under the five warming scenarios. Warming had negligible effects on the organic C density in soil,and soil physical and biochemical fractions in the subsurface layer( 15-30 cm). The results revealed that in the short-term,warming may increase the recalcitrance of non-protected C in the Karst Plateau soil. This is not necessarily an over-or underestimation of the effects of global warming on soil organic C density and the capacity of soil to protect C when subjected to symmetric warming,but may potentially overestimate the recalcitrance of organic C in the non-protected fraction of the surface layer( 0-15 cm).
Elucidating the mechanisms of warming-induced stability for soil organic C is one of the keys for evaluating the tendency of soil C sources/sinks in projected global warming models. Organic C densities in soil,and soil physical and biochemical fractions,under different warming scenarios in the Karst Plateau were investigated following a 4-yr continuous warming using infrared radiators,via density fractionation and acid hydrolysis. Six treatments were arranged: no warming( ambient temp,CK); symmetric warming( ambient + 2. 0℃ full year); and lowly,moderately,highly,and extremely asymmetric warming( ambient + 2. 5℃/1. 5℃,3. 0℃/1. 0℃,3. 5℃/0. 5℃,and 4. 0℃/0℃ in winter-spring/summer-autumn seasons,respectively; LAW,MAW,HAW,and EAW).The moderately asymmetric warming was highly similar to a multi-year warming scenario in the study region. The results showed there were no significant differences in soil organic C densities in the surface layer( 0-15 cm) among the warming treatments,with a range of 1. 95 kg·m-2 to 2. 02 kg·m-2,which is insignificantly different to the CK( 1. 94 kg·m-2). There were no significant differences in the C density of light and heavy fractions,and the recalcitrant heavy-fraction among the warming treatments,and between the warming and no warming treatments. The average recalcitrant C density of the light fraction in the warming treatments was 1. 18 times higher than the CK,with a significantly higher recalcitrant C density of the light fraction in the symmetric warming,and lowly and moderately asymmetric warming treatments,compared to that of the CK. The recalcitrant C density and recalcitrant C index of the light fraction showed a tendency to decrease as the asymmetry of warming increased under the five warming scenarios. Warming had negligible effects on the organic C density in soil,and soil physical and biochemical fractions in the subsurface layer( 15-30 cm). The results revealed that in the short-term,warming may increase the recalcitrance of non-protected C in the Karst Plateau soil. This is not necessarily an over-or underestimation of the effects of global warming on soil organic C density and the capacity of soil to protect C when subjected to symmetric warming,but may potentially overestimate the recalcitrance of organic C in the non-protected fraction of the surface layer( 0-15 cm).
引文
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[26]Tan Z,Lal R,Owens L,et al.Distribution of light and heavy fractions of soil organic carbon as related to land use and tillage practice[J].Soil and Tillage Research,2007,92(1-2):53-59.
[27]Co0teaux M M,Bottner P,Anderson J M,et al.Decomposition of13C-labelled standard plant material in a latitudinal transect of European coniferous forests:Differential impact of climate on the decomposition of soil organic matter compartments[J].Biogeochemistry,2001,54(2):147-170.
[28]Marin-Spiotta E,Silver W L,Swanston C W,et al.Soil organic matter dynamics during 80 years of reforestation of tropical pastures[J].Global Change Biology,2009,15(6):1584-1597.
[29]宋飘,张乃莉,马克平,等.全球气候变暖对凋落物分解的影响[J].生态学报,2014,34(6):1327-1339.Song P,Zhang N L,Ma K P,et al.Impacts of global warming on litter decomposition[J].Acta Ecologica Sinica,2014,34(6):1327-1339.
[30]Lehmann J,Kleber M.The contentious nature of soil organic matter[J].Nature,2015,528(7580):60-68.
[31]Wang G,Wang C Y,Wang W Y,et al.Capacity of soil to protect organic carbon and biochemical characteristics of density fractions in Ziwulin Haplic Greyxems soil[J].Chinese Science Bulletin,2005,50(1):27-32.
[32]胡乐宁,苏以荣,何寻阳,等.西南喀斯特石灰土中钙的形态与含量及其对土壤有机碳的影响[J].中国农业科学,2012,45(10):1946-1953.Hu L N,Su Y R,He X Y,et al.The speciation and content of Calcium in karst soils,and its effects on soil organic carbon in karst region of Southwest China[J].Scientia Agricultura Sinica,2012,45(10):1946-1953.
[2]Easterling D R,Horton B,Jones P D,et al.Maximum and minimum temperature trends for the globe[J].Science,1997,277(5324):364-367.
[3]Lal R.Soil carbon sequestration impacts on global climate change and food security[J].Science,2004,304(5677):1623-1627.
[4]苏宏新,李广起.模拟蒙古栎林生态系统碳收支对非对称性升温的响应[J].科学通报,2012,57(17):1544-1552.Su H X,Li G Q.Simulating the response of the Quercus mongolica forest ecosystem carbon budget to asymmetric warming[J].Chinese Science Bulletin,2012,57(17):1544-1552.
[5]Luo Y Q,Wan S Q,Hui D F,et al.Acclimatization of soil respiration to warming in a tall grass prairie[J].Nature,2001,413(6856):622-625.
[6]Leirós M C,Trasar-Cepeda C,Seoane S,et al.Dependence of mineralization of soil organic matter on temperature and moisture[J].Soil Biology and Biochemistry,1999,31(3):327-335.
[7]Trumbore S E,Chadwick O A,Amundson R.Rapid exchange between soil carbon and atmospheric carbon dioxide driven by temperature change[J].Science,1996,272(5260):393-396.
[8]IPCC.Climate Change 2014:Impacts,Adaptation,and Vulnerability.Part A:Global and Sectoral Aspects.Contribution of Working GroupⅡto the Fifth Assessment Report of the Intergovernmental Panel on Climate Change[M].Cambridge,UK,New York,NY,USA:Cambridge University Press,2014.
[9]潘根兴,周萍,李恋卿,等.固碳土壤学的核心科学问题与研究进展[J].土壤学报,2007,44(2):327-337.Pan G X,Zhou P,Li L Q,et al.Core issues and research progresses of soil science of C sequestration[J].Acta Pedologica Sinica,2007,44(2):327-337.
[10]郑建萌,任菊章,张万诚.云南近百年来温度雨量的变化特征分析[J].灾害学,2010,25(3):24-31.Zheng J M,Ren J Z,Zhang W C.Analysis on variation characteristics of temperature and rainfall in Yunnan in the last100 years[J].Journal of Catastrophology,2010,25(3):24-31.
[11]Li Z X,He Y Q,Theakstone W H,et al.Altitude dependency of trends of daily climate extremes in southwestern China,1961-2008[J].Journal of Geographical Sciences,2012,22(3):416-430.
[12]陈智,尹华军,卫云燕,等.夜间增温和施氮对川西亚高山针叶林土壤有效氮和微生物特性的短期影响[J].植物生态学报,2010,34(11):1254-1264.Chen Z,Yin H J,Wei Y Y,et al.Short-term effects of night warming and nitrogen addition on soil available nitrogen and microbial properties in subalpine coniferous forest,Western Sichuan,China[J].Chinese Journal of Plant Ecology,2010,34(11):1254-1264.
[13]Shaw M R,Zavaleta E S,Chiariello N R,et al.Grassland responses to global environmental changes suppressed by elevated CO2[J].Science,2014,298(5600):1987-1990.
[14]Janzen H H,Campbell C A,Brandt S A.Light-fraction organic matter in soils from long-term crop rotations[J].Soil Science Society of America Journal,1992,56(6):1799-1806.
[15]Rovira P,Vallejo V R.Labile and recalcitrant pools of carbon and nitrogen in organic matter decomposing at different depths in soil:an acid hydrolysis approach[J].Geoderma,2002,107(1-2):109-141.
[16]唐国勇,李昆,孙永玉,等.干热河谷不同利用方式下土壤活性有机碳含量及其分配特征[J].环境科学,2010,31(5):1365-1371.Tang G Y,Li K,Sun Y Y,et al.Soil labile organic carbon contents and their allocation characteristics under different land uses at dry-hot valley[J].Environmental Science,2010,31(5):1365-1371.
[17]吴金水,林启美,黄巧云,等.土壤微生物生物量测定方法及其应用[M].北京:气象出版社,2006.
[18]唐国勇,李昆,孙永玉,等.干热河谷林地燥红土固碳特征及“新固定”碳表观稳定性[J].环境科学,2012,33(2):551-557.Tang G Y,Li K,Sun Y Y,et al.Characteristics of carbon sequestration and apparent stability of new sequestered carbon in forested torrid red soil at dry-hot valley[J].Environmental Science,2012,33(2):551-557.
[19]Trumbore S E.Potential responses of soil organic carbon to global environmental change[J].Proceedings of the National Academy of Sciences of the United States of America,1997,94(16):8284-8291.
[20]唐国勇,童成立,苏以荣,等.含水量对14C标记秸秆和土壤原有有机碳矿化的影响[J].中国农业科学,2006,39(3):538-543.Tang G Y,Tong C L,Su Y R,et al.Effects of soil moisture content on the mineralization of added14C-labbelled straw and native soil organic carbon in upland soil[J].Scientia Agricultura Sinica,2006,39(3):538-543.
[21]Inglima I,Alberti G,Bertolini T,et al.Precipitation pulses enhance respiration of Mediterranean ecosystems:the balance between organic and inorganic components of increased soil CO2efflux[J].Global Change Biology,2009,15(5):1289-1301.
[22]Wick B,Tiessen H.Organic matter turnover in light fraction and whole soil under Silvopastoral land use in semiarid Northeast Brazil[J].Rangeland Ecology&Management,2008,61(3):275-283.
[23]Wang W Y,Wang Q J,Lu Z Y.Soil organic carbon and nitrogen content of density fractions and effect of meadow degradation to soil carbon and nitrogen of fractions in alpine Kobresia meadow[J].Science in China Series D:Earch Sciences,2009,52(5):660-668.
[24]Christensen B T.Physical fractionation of soil and organic matter in primary particle size and density separates[A].In:Stewart B A(Eds.).Advances in Soil Science[M].New York:Springer,1992.
[25]Tang G Y,Li K.Tree species controls on soil carbon sequestration and carbon stability following 20 years of afforestation in a valley-type savanna[J].Forest Ecology and Management,2013,291:13-19.
[26]Tan Z,Lal R,Owens L,et al.Distribution of light and heavy fractions of soil organic carbon as related to land use and tillage practice[J].Soil and Tillage Research,2007,92(1-2):53-59.
[27]Co0teaux M M,Bottner P,Anderson J M,et al.Decomposition of13C-labelled standard plant material in a latitudinal transect of European coniferous forests:Differential impact of climate on the decomposition of soil organic matter compartments[J].Biogeochemistry,2001,54(2):147-170.
[28]Marin-Spiotta E,Silver W L,Swanston C W,et al.Soil organic matter dynamics during 80 years of reforestation of tropical pastures[J].Global Change Biology,2009,15(6):1584-1597.
[29]宋飘,张乃莉,马克平,等.全球气候变暖对凋落物分解的影响[J].生态学报,2014,34(6):1327-1339.Song P,Zhang N L,Ma K P,et al.Impacts of global warming on litter decomposition[J].Acta Ecologica Sinica,2014,34(6):1327-1339.
[30]Lehmann J,Kleber M.The contentious nature of soil organic matter[J].Nature,2015,528(7580):60-68.
[31]Wang G,Wang C Y,Wang W Y,et al.Capacity of soil to protect organic carbon and biochemical characteristics of density fractions in Ziwulin Haplic Greyxems soil[J].Chinese Science Bulletin,2005,50(1):27-32.
[32]胡乐宁,苏以荣,何寻阳,等.西南喀斯特石灰土中钙的形态与含量及其对土壤有机碳的影响[J].中国农业科学,2012,45(10):1946-1953.Hu L N,Su Y R,He X Y,et al.The speciation and content of Calcium in karst soils,and its effects on soil organic carbon in karst region of Southwest China[J].Scientia Agricultura Sinica,2012,45(10):1946-1953.