耕作干扰下喀斯特土壤有机碳损失主要途径及其影响因素
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摘要
西南喀斯特生态系统原生土壤有机碳(SOC)含量较高,但在开垦后急剧损失,然而目前对SOC损失过程、途径和机制仍缺乏充分认知。本研究基于不同频率翻耕处理(分别隔6、4、2、1个月翻耕一次,以免耕为对照)的原位控制试验,以土壤团聚体为切入点,通过对土壤CO_2排放和可溶性有机碳(DOC)淋失通量进行为期一年的连续监测,探讨了SOC损失的主要途径及其影响因素。结果发现:翻耕导致表层(0～10 cm)土壤SOC和5～8 mm粒级团聚体显著降低;一年后,各翻耕处理平均损失15.4%～27.6%的SOC,土壤DOC淋失量仅占SOC损失量的0.05%～0.10%,而土壤以CO_2形式释放的碳占SOC损失总量的22.7%～35.5%,是土壤碳损失的重要途径之一;SOC损失量与Ca~(2+)、Mg~(2+)淋失总量均呈显著正相关,说明在岩溶作用下以HCO_3-形式淋失是SOC损失的另一重要途径;土壤CO_2排放速率与5～8 mm粒级团聚体含量呈显著负相关,说明翻耕干扰导致5～8 mm团聚体崩解、受团聚体保护的闭蓄态SOC释放后迅速矿化是喀斯特SOC损失的主要机制。
Soil organic carbon(SOC)content is relatively high in natural karst ecosystems of southwest China,but a substantial SOC loss would occur rapidly once cultivated.However,the pathways and underlying mechanisms responsible for SOC loss upon disturbance are still unknown.Based on an in-situ experiment with treatments of tillage at different frequencies(tilled every 6,4,2,and 1 month(s),no-till treatment as control),this study took soil aggregates as the key point and investigated the pathways and influencing factors of SOC loss via monitoring soil CO_2 fluxes and dissolved organic carbon(DOC)leaching fluxes for 1 year.Tillage managements significantly reduced the 5～8 mm aggregate content and SOC concentration.Approximately 15.4%～27.6%of SOC was lost from the surface soil(0～10cm)during this year.DOC loss via leaching contributed only 0.05%～0.10%of the total SOC loss,whereas CO_2-C loss accounted for about 22.7%～35.5%of total SOC loss,supporting that CO_2 emission was one of the important ways of Closs.Besides,SOC losses were significantly and positively correlated with both Ca~(2+)and Mg~(2+)losses via leaching,indicating that HCO_3~--C leaching induced by karstification was another important way of SOC loss.Soil CO_(2 )fluxes weresignificantly and negatively correlated with 5～8 mm aggregate contents,suggesting that the disruption of 5～8 mm aggregates induced by tillage led to the failure of SOC protection by aggregates,thereby accelerating SOC mineralization.This study revealed the mechanisms responsible for SOC loss induced by tillage in a calcareous soil of southwest China.
Soil organic carbon(SOC)content is relatively high in natural karst ecosystems of southwest China,but a substantial SOC loss would occur rapidly once cultivated.However,the pathways and underlying mechanisms responsible for SOC loss upon disturbance are still unknown.Based on an in-situ experiment with treatments of tillage at different frequencies(tilled every 6,4,2,and 1 month(s),no-till treatment as control),this study took soil aggregates as the key point and investigated the pathways and influencing factors of SOC loss via monitoring soil CO_2 fluxes and dissolved organic carbon(DOC)leaching fluxes for 1 year.Tillage managements significantly reduced the 5～8 mm aggregate content and SOC concentration.Approximately 15.4%～27.6%of SOC was lost from the surface soil(0～10cm)during this year.DOC loss via leaching contributed only 0.05%～0.10%of the total SOC loss,whereas CO_2-C loss accounted for about 22.7%～35.5%of total SOC loss,supporting that CO_2 emission was one of the important ways of Closs.Besides,SOC losses were significantly and positively correlated with both Ca~(2+)and Mg~(2+)losses via leaching,indicating that HCO_3~--C leaching induced by karstification was another important way of SOC loss.Soil CO_(2 )fluxes weresignificantly and negatively correlated with 5～8 mm aggregate contents,suggesting that the disruption of 5～8 mm aggregates induced by tillage led to the failure of SOC protection by aggregates,thereby accelerating SOC mineralization.This study revealed the mechanisms responsible for SOC loss induced by tillage in a calcareous soil of southwest China.
引文
[1]Lal R.Soil carbon sequestration to mitigate climate change[J].Geoderma,2004,123(1/2):1-22.
[2]Gelaw A M,Singh B R,Lal R.Organic carbon and nitrogen associated with soil aggregates and particle sizes under different land uses in Tigray,Northern Ethiopia[J].Land Degradation&Development,2015,26(7):690-700.
[3]Debasish S,Kukal S S,Bawa S S.Soil organic carbon stock and fractions in relation to land use and soil depth in the degraded Shiwaliks hills of lower Himalayas[J].Land Degradation&Development,2014,25(5):407-416.
[4]Ziadat F M,Taimeh A Y.Effect of rainfall intensity,slope,land use and antecedent soil moisture on soil erosion in an arid environment[J].Land Degradation&Development,2013,24(6):582-590.
[5]Murty D,Kirschbaum M U F,Mcmurtrie,et al.Does conversion of forest to agricultural land change soil carbon and nitrogen?Areview of the literature[J].Global Change Biology,2002,8(2):105-123.
[6]傅伯杰,陈利顶,王军,等.土地利用结构与生态过程[J].第四纪研究,2003,23(3):247-255.Fu B J,Chen L D,Wang J,et al.Land use structure and ecological processes[J].Quaternary Sciences,2003,23(3):247-255.
[7]Blanco-Canqui H,Lal R.Mechanisms of carbon sequestration in soil aggregates[J].Critical Reviews in Plant Sciences,2004,23(6):481-504.
[8]Ashagrie Y,Zech W,Guggenberger G,et al.Soil aggregation,and total and particulate organic matter following conversion of native forests to continuous cultivation in Ethiopia[J].Soil&Tillage Research,2007,94(1):101-108.
[9]Schweizer S A,Fischer H,H?ring V,et al.Soil structure breakdown following land use change from forest to maize in Northwest Vietnam[J].Soil&Tillage Research,2017,166:10-17.
[10]袁道先.我国西南岩溶石山的环境地质问题[J].世界科技研究与发展,1997,19(5):41-43.Yuan D X.On the environmental and geologic problems of karst mountains and rocks in the south-west China[J].World Sci-Tech R&D,1997,19(5):41-43.
[11]蔡运龙.中国西南岩溶石山贫困地区的生态重建[J].地球科学进展,1996,11(6):84-88.Cai Y L.Preliminary reseach on ecological reconstruction in karst mountain proverty areas of southwest China[J].Advance in Earth Sciences,1996,11(6):84-88.
[12]刘丛强,郎赟超,李思亮,等.喀斯特生态系统生物地球化学过程与物质循环研究:重要性、现状与趋势[J].地学前缘,2009,16(6):1-12.Liu C Q,Lang Y C,Li S L,et al.Researches on biogeochemical processes and nutrient cycling in karstic ecological systems,southwest China:A review[J].Earth Science Frontiers,2009,16(6):1-12.
[13]Chen H S,Zhang W,Wang K L,et al.Soil organic carbon and total nitrogen as affected by land use types in karst and non-karst areas of northwest Guangxi,China[J].Journal of the Science of Food and Agriculture,2012,92(5):1086-1093.
[14]盛茂银,熊康宁,崔高仰,等.贵州喀斯特石漠化地区植物多样性与土壤理化性质[J].生态学报,2015,35(2):434-448.Sheng M Y,Xiong K N,Cui G Y,et al.Plant diversity and soil physical-chemical properties in karst rocky desertification ecosystem of Guizhou,China[J].Acta Ecologica Sinica,2015,35(2):434-448.
[15]龙健,李娟,汪境仁,等.典型喀斯特地区石漠化演变过程对土壤质量性状的影响[J].水土保持学报,2006,20(2):77-81.Long J,Li J,Wang J R,et al.Effects on soil quality properties in process of karst rocky desertification[J].Journal of Soil and Water Conservation,2006,20(2):77-81.
[16]刘方,王世杰,刘元生,等.喀斯特石漠化过程土壤质量变化及生态环境影响评价[J].生态学报,2005,25(3):639-644.Liu F,Wang S J,Liu Y S,et al.Changes of soil quality in the process of karst rocky desertification and evaluation of impact on ecological environment[J].Acta Ecologica Sinica,2005,25(3):639-644.
[17]张伟,陈洪松,苏以荣,等.不同作物和施肥方式对新垦石灰土土壤肥力的影响[J].土壤通报,2013,44(4):925-930.Zhang W,Chen H S,Su Y R,et al.Effects of reclamation and fertilization on calcareous soil fertility in the initial period of cultivation[J].Chinese Journal of Soil Science,2013,44(4):925-930.
[18]张信宝,王世杰,曹建华,等.西南喀斯特山地水土流失特点及有关石漠化的几个科学问题[J].中国岩溶,2010,29(3):274-279.Zhang X B,Wang S J,Cao J H,et al.Characteristics of water loss and soil erosion and some scientific problems on karst rocky desertification in Southwest China karst area[J].Carsologica Sinica,2010,29(3):274-279.
[19]陈洪松,王克林.西南喀斯特山区土壤水分研究[J].农业现代化研究,2008,29(6):734-738.Chen H S,Wang K L.Soil water research in karst mountain areas of Southwest China[J].Research of agricultural modernization,2008,29(6):734-738.
[20]Tang X L,Liu S G,Zhou G Y,et al.Soil-atmospheric exchange of CO2,CH4,and N2O in three subtropical forest ecosystems in southern China[J].Global Change Biology,2006,12(3):546-560.
[21]刘光崧.土壤理化分析与剖面描述[M].北京:中国标准出版社,1996.Liu G S.Soil Physical and Chemical Analysis and Description of Soil Profiles[M].Beijing:Standards Press of China,1996
[22]Kalbitz K,Solinger S,Park J H,et al.Controls on the dynamics of dissolved organic matter in soils:A review[J].Soil Science,2000,165(4):277-304.
[23]Kaiser K,Guggenberger G.Storm flow flushing in a structured soil changes the composition of dissolved organic matter leached into the subsoil[J].Geoderma,2005,127(3/4):177-187.
[24]Pires L F,Borges J A R,Rosa J A,et al.Soil structure changes induced by tillage systems[J].Soil&Tillage Research,2017,165:66-79.
[25]Usowicz B,Lipiec J,Usowicz J B,et al.Effects of aggregate size on soil thermal conductivity:Comparison of measured and modelpredicted data[J].International of Heat and Mass Transfer,2013,57(2):536-541.
[26]D a v i d s o n E A,A c k e r m a n I L.C h a n g e s i n s o i l c a r b o n inventories following cultivation of previously untilled soils[J].Biogeochemistry,1993,20(3):161-193.
[27]Detwiler R P.Land use change and the global carbon cycle:The role of tropical soils[J].Biogeochemistry,1986,2(1):67-93.
[28]Pan G X,Tao Y X,Shun Y H,et al.Some features of carbon cycles in karst system and the implication for epikarstificationan example of Yaji karst experimental site in Guilin,China[J].The Journal of Chinese Geography,1997,7(3):48-57.
[29]何师意,徐胜友,张美良.岩溶土壤中CO2浓度、水化学观测及其与岩溶作用关系[J].中国岩溶,1997,16(4):39-44.He S Y,Xu S Y,Zhang M L.Observation on soil CO2concentration,hydrochemistry,and their relationship with karst processes[J].Carsologica Sinica,1997,16(4):39-44.
[30]Dunjo G,Pardini G,Gispert M.Land use change effects on abandoned terraced soils in a Mediterranean catchment,NESpain[J].Catena,2003,52(1):23-37.
[31]Cerda A.Aggregate stability against water forces under different climates on agriculture land and scrubland in southern Bolivia[J].Soil&Tillage Research,2000,57(3):159-166.
[32]李阳兵,谢德体,魏朝富.岩溶生态系统土壤及表生植被某些特性变异与石漠化的相关性[J].土壤学报,2004,41(2):196-202.Li Y B,Xie D T,Wei C F.Correlation between rock desertification a n d v a r i a t i o n s o f s o i l a n d s u r f a c e v e g e t a t i o n i n k a r s t eco-system[J].Acta Pedologica Sinica,2004,41(2):196-202.
[33]Curtin D,Beare M H,Scott C L,et al.Mineralization of soil carbon and nitrogen following physical disturbance:A laboratory assessment[J].Soil Science Society of America Journal,2014,78(3):925-935.
[34]魏亚伟,苏以荣,陈香碧,等.人为干扰对喀斯特土壤团聚体及其有机碳稳定性的影响[J].应用生态学报,2011,22(4):971-978.Wei Y W,Su Y R,Chen X B,et al.Effects of human disturbance on soil aggregates content and their organic C stability in karst regions[J].Chinese Journal of Applied Ecology,2011,22(4):971-978.
[35]Bimüller C,Kreyling O,K?lbl A,et al.Carbon and nitrogen mineralization in hierarchically structured aggregates of different size[J].Soil&Tillage Research,2016,160:23-33.
[36]Fornara D A,Steinbeiss S,Mcnamara N P,et al.Increases in soil organic carbon sequestration can reduce the global warming potential of long-term liming to permanent grassland[J].Global Change Biology,2011,17(5):1925-1934.
[37]Briedis C,SáJ C D M,Caires E F,et al.Soil organic matter pools and carbon-protection mechanisms in aggregate classes influenced by surface liming in a no-till system[J].Geoderma,2012,170:80-88.
[38]Fernández-Ugalde O,Virto I,BarréP,et al.Mechanisms of macroaggregate stabilisation by carbonates:Implications for organic matter protection in semi-arid calcareous soils[J].Soil Research,2014,52(2):180-192.
[2]Gelaw A M,Singh B R,Lal R.Organic carbon and nitrogen associated with soil aggregates and particle sizes under different land uses in Tigray,Northern Ethiopia[J].Land Degradation&Development,2015,26(7):690-700.
[3]Debasish S,Kukal S S,Bawa S S.Soil organic carbon stock and fractions in relation to land use and soil depth in the degraded Shiwaliks hills of lower Himalayas[J].Land Degradation&Development,2014,25(5):407-416.
[4]Ziadat F M,Taimeh A Y.Effect of rainfall intensity,slope,land use and antecedent soil moisture on soil erosion in an arid environment[J].Land Degradation&Development,2013,24(6):582-590.
[5]Murty D,Kirschbaum M U F,Mcmurtrie,et al.Does conversion of forest to agricultural land change soil carbon and nitrogen?Areview of the literature[J].Global Change Biology,2002,8(2):105-123.
[6]傅伯杰,陈利顶,王军,等.土地利用结构与生态过程[J].第四纪研究,2003,23(3):247-255.Fu B J,Chen L D,Wang J,et al.Land use structure and ecological processes[J].Quaternary Sciences,2003,23(3):247-255.
[7]Blanco-Canqui H,Lal R.Mechanisms of carbon sequestration in soil aggregates[J].Critical Reviews in Plant Sciences,2004,23(6):481-504.
[8]Ashagrie Y,Zech W,Guggenberger G,et al.Soil aggregation,and total and particulate organic matter following conversion of native forests to continuous cultivation in Ethiopia[J].Soil&Tillage Research,2007,94(1):101-108.
[9]Schweizer S A,Fischer H,H?ring V,et al.Soil structure breakdown following land use change from forest to maize in Northwest Vietnam[J].Soil&Tillage Research,2017,166:10-17.
[10]袁道先.我国西南岩溶石山的环境地质问题[J].世界科技研究与发展,1997,19(5):41-43.Yuan D X.On the environmental and geologic problems of karst mountains and rocks in the south-west China[J].World Sci-Tech R&D,1997,19(5):41-43.
[11]蔡运龙.中国西南岩溶石山贫困地区的生态重建[J].地球科学进展,1996,11(6):84-88.Cai Y L.Preliminary reseach on ecological reconstruction in karst mountain proverty areas of southwest China[J].Advance in Earth Sciences,1996,11(6):84-88.
[12]刘丛强,郎赟超,李思亮,等.喀斯特生态系统生物地球化学过程与物质循环研究:重要性、现状与趋势[J].地学前缘,2009,16(6):1-12.Liu C Q,Lang Y C,Li S L,et al.Researches on biogeochemical processes and nutrient cycling in karstic ecological systems,southwest China:A review[J].Earth Science Frontiers,2009,16(6):1-12.
[13]Chen H S,Zhang W,Wang K L,et al.Soil organic carbon and total nitrogen as affected by land use types in karst and non-karst areas of northwest Guangxi,China[J].Journal of the Science of Food and Agriculture,2012,92(5):1086-1093.
[14]盛茂银,熊康宁,崔高仰,等.贵州喀斯特石漠化地区植物多样性与土壤理化性质[J].生态学报,2015,35(2):434-448.Sheng M Y,Xiong K N,Cui G Y,et al.Plant diversity and soil physical-chemical properties in karst rocky desertification ecosystem of Guizhou,China[J].Acta Ecologica Sinica,2015,35(2):434-448.
[15]龙健,李娟,汪境仁,等.典型喀斯特地区石漠化演变过程对土壤质量性状的影响[J].水土保持学报,2006,20(2):77-81.Long J,Li J,Wang J R,et al.Effects on soil quality properties in process of karst rocky desertification[J].Journal of Soil and Water Conservation,2006,20(2):77-81.
[16]刘方,王世杰,刘元生,等.喀斯特石漠化过程土壤质量变化及生态环境影响评价[J].生态学报,2005,25(3):639-644.Liu F,Wang S J,Liu Y S,et al.Changes of soil quality in the process of karst rocky desertification and evaluation of impact on ecological environment[J].Acta Ecologica Sinica,2005,25(3):639-644.
[17]张伟,陈洪松,苏以荣,等.不同作物和施肥方式对新垦石灰土土壤肥力的影响[J].土壤通报,2013,44(4):925-930.Zhang W,Chen H S,Su Y R,et al.Effects of reclamation and fertilization on calcareous soil fertility in the initial period of cultivation[J].Chinese Journal of Soil Science,2013,44(4):925-930.
[18]张信宝,王世杰,曹建华,等.西南喀斯特山地水土流失特点及有关石漠化的几个科学问题[J].中国岩溶,2010,29(3):274-279.Zhang X B,Wang S J,Cao J H,et al.Characteristics of water loss and soil erosion and some scientific problems on karst rocky desertification in Southwest China karst area[J].Carsologica Sinica,2010,29(3):274-279.
[19]陈洪松,王克林.西南喀斯特山区土壤水分研究[J].农业现代化研究,2008,29(6):734-738.Chen H S,Wang K L.Soil water research in karst mountain areas of Southwest China[J].Research of agricultural modernization,2008,29(6):734-738.
[20]Tang X L,Liu S G,Zhou G Y,et al.Soil-atmospheric exchange of CO2,CH4,and N2O in three subtropical forest ecosystems in southern China[J].Global Change Biology,2006,12(3):546-560.
[21]刘光崧.土壤理化分析与剖面描述[M].北京:中国标准出版社,1996.Liu G S.Soil Physical and Chemical Analysis and Description of Soil Profiles[M].Beijing:Standards Press of China,1996
[22]Kalbitz K,Solinger S,Park J H,et al.Controls on the dynamics of dissolved organic matter in soils:A review[J].Soil Science,2000,165(4):277-304.
[23]Kaiser K,Guggenberger G.Storm flow flushing in a structured soil changes the composition of dissolved organic matter leached into the subsoil[J].Geoderma,2005,127(3/4):177-187.
[24]Pires L F,Borges J A R,Rosa J A,et al.Soil structure changes induced by tillage systems[J].Soil&Tillage Research,2017,165:66-79.
[25]Usowicz B,Lipiec J,Usowicz J B,et al.Effects of aggregate size on soil thermal conductivity:Comparison of measured and modelpredicted data[J].International of Heat and Mass Transfer,2013,57(2):536-541.
[26]D a v i d s o n E A,A c k e r m a n I L.C h a n g e s i n s o i l c a r b o n inventories following cultivation of previously untilled soils[J].Biogeochemistry,1993,20(3):161-193.
[27]Detwiler R P.Land use change and the global carbon cycle:The role of tropical soils[J].Biogeochemistry,1986,2(1):67-93.
[28]Pan G X,Tao Y X,Shun Y H,et al.Some features of carbon cycles in karst system and the implication for epikarstificationan example of Yaji karst experimental site in Guilin,China[J].The Journal of Chinese Geography,1997,7(3):48-57.
[29]何师意,徐胜友,张美良.岩溶土壤中CO2浓度、水化学观测及其与岩溶作用关系[J].中国岩溶,1997,16(4):39-44.He S Y,Xu S Y,Zhang M L.Observation on soil CO2concentration,hydrochemistry,and their relationship with karst processes[J].Carsologica Sinica,1997,16(4):39-44.
[30]Dunjo G,Pardini G,Gispert M.Land use change effects on abandoned terraced soils in a Mediterranean catchment,NESpain[J].Catena,2003,52(1):23-37.
[31]Cerda A.Aggregate stability against water forces under different climates on agriculture land and scrubland in southern Bolivia[J].Soil&Tillage Research,2000,57(3):159-166.
[32]李阳兵,谢德体,魏朝富.岩溶生态系统土壤及表生植被某些特性变异与石漠化的相关性[J].土壤学报,2004,41(2):196-202.Li Y B,Xie D T,Wei C F.Correlation between rock desertification a n d v a r i a t i o n s o f s o i l a n d s u r f a c e v e g e t a t i o n i n k a r s t eco-system[J].Acta Pedologica Sinica,2004,41(2):196-202.
[33]Curtin D,Beare M H,Scott C L,et al.Mineralization of soil carbon and nitrogen following physical disturbance:A laboratory assessment[J].Soil Science Society of America Journal,2014,78(3):925-935.
[34]魏亚伟,苏以荣,陈香碧,等.人为干扰对喀斯特土壤团聚体及其有机碳稳定性的影响[J].应用生态学报,2011,22(4):971-978.Wei Y W,Su Y R,Chen X B,et al.Effects of human disturbance on soil aggregates content and their organic C stability in karst regions[J].Chinese Journal of Applied Ecology,2011,22(4):971-978.
[35]Bimüller C,Kreyling O,K?lbl A,et al.Carbon and nitrogen mineralization in hierarchically structured aggregates of different size[J].Soil&Tillage Research,2016,160:23-33.
[36]Fornara D A,Steinbeiss S,Mcnamara N P,et al.Increases in soil organic carbon sequestration can reduce the global warming potential of long-term liming to permanent grassland[J].Global Change Biology,2011,17(5):1925-1934.
[37]Briedis C,SáJ C D M,Caires E F,et al.Soil organic matter pools and carbon-protection mechanisms in aggregate classes influenced by surface liming in a no-till system[J].Geoderma,2012,170:80-88.
[38]Fernández-Ugalde O,Virto I,BarréP,et al.Mechanisms of macroaggregate stabilisation by carbonates:Implications for organic matter protection in semi-arid calcareous soils[J].Soil Research,2014,52(2):180-192.