Impacts of Different Land Uses on Carbon Fluxes from Subtropical Soils in Central China: Implications for Carbon Sequestration

论文摘要

全球碳循环和全球气候变化过程中土地利用方式起重要作用,因此了解土壤中碳释放（CO2和CH4）及其环境影响因素,便于探讨亚热带不同土地利用方式生态系统中碳动力学机制。在湖北省咸宁地区和秭归县设置采样点,采用静态箱法监测不同土地利用方式下土壤CO2、CH4释放和环境因素的关系。为了更进一步了解不同土地利用方式下对土壤含碳量的影响,设置62天培养试验,在水分含量WHC为20-100%和温度为5-45℃下测定四种土地利用方式土壤CO2排放通量,同时在水稻生长季节开展田间观测试验以预测红壤固碳能力。试验结果表明:不同土地利用方式下土壤是大气CH4吸收“汇”和CO2排放“源”。年平均CO2释放量范围为5.3～10.5 Mg CO2ha-1yr-1,年平均CH4释放量范围为+0.47～-2.37 kg CH4ha-1yr-1,林地土壤CO2和CH4排放通量显著低于农田土壤,所有土地利用方式中菜地土壤CO2排放通量最大,常耕CO2果园排放通量显著高于免耕果园,揭示耕作激发了CO2产生,而常耕果园CH4吸收通量显著低于免耕果园,说明耕作影响甲烷氧化菌的产生。受土壤温度、水分含量、微生物碳、微生物氮和可溶性有机碳的季节性变化的驱动土壤CO2和CH4排放或吸收存在明显的季节性变化规律,湿热季节（4月-9月）CO2的排放通量显著高于干冷季节（10月-3月）。土壤CO2排放通量和微生物商（Qt）、MBC:MBN显著相关,而与DOC:DON不相关。逐步回归单因素分析表明,不同土地利用方式下土壤温度、WFPS、DOC、MBC和MBN对CO2排放有显著影响,而DON对CO2影响较小,然而,在所有土地利用方式中以土壤温度、WFPS、DOC、MBC、DON和MBN为模型,CO2排放与这些因素呈显著相关。所有土地利用方式中综合分析所有影响因子,土壤温度是控制CO2排放最重要因子。由季节性的土壤温度、WFPS、土壤NO3--N和土壤NH4+-N含量的驱动,干冷季节的CH4吸收显著高于湿热季节,以线性逐步回归方程分析表明,所有土地利用方式中土壤温度、WFPS、土壤NO3--N和土壤NH4+-N含量显著影响土壤CH4排放。为预测不同土地利用方式中土壤有机碳动力学机制,培养试验中土壤有机碳矿化分为活性碳……在四种土地利用方式下的培养试验结果表明:（1）土壤活性碳平均驻留时间为49-65天,占总有机碳的1.2-3.5%,（2）土壤缓效性碳平均驻留时间为2-27年,占总有机碳的25.3-60%,惰效性碳占总有机碳的36.5-73.9%。林地含较高的惰效性碳和较低的活性碳。土壤碳呼吸（SCDR）与所有形态有机碳、C:N比、pH、土壤呼吸（SDR）和总氮相关性较好,土壤有机碳SOC与Cs,CrSDR,总氮和WHC（含水量）呈正相关,与容重呈负相关。稻田、果园、林地、旱地Q10分别为1.90±0.17,2.19±0.32,2.34±0.32,3.23±0.47。不同Q10值说明土壤有机碳对温度的敏感度,不同土地利用方式中由于土壤有机碳含量不同,造成Q10值不同。稻田试验不同处理中,植株土壤施氮肥显著促进CO2排放,而株间土壤和空地没有影响。而空地土壤中,CO2随施氮量增加而降低,说明氮肥的施用抑制微生物活动。……说明氮肥加秸秆处理有减缓全球碳释放趋势。三种温室气体累计全球增温潜势（GWP）大小依次为菜地＞旱地＞果园＞林地,所有土地利用方式中N2O的GWP显著高于CH4,林地CH4吸收完全抵消N2O释放的GWP,总体来说,CH4吸收一定程度上抵消CO2和N2O排放的GWP,本研究得出主要结论如下:（1）由于亚热带地区不同土地利用方式下土壤环境因子存在差异从而使CO2和CH4排放差别较大,则土地利用方式决定GWP的大小,而土壤温度是最重要的影响因子,不同土地利用方式下其它土壤条件相互作用影响底物的矿化从而影响CO2和CH4的排放。（2）不同土地利用方式下土壤有机碳有不同的温度敏感度,且植物类型和耕作方式控制土壤微生物和生化特性,是重要的影响碳释放因素。（3）氮的施入增加CO2的排放,然而,氮肥和油菜秸秆配施可使红壤中的碳增加是最合理的农业生产方式。（4）由于不同土地利用方式存在不同的管理方式造成土壤特性差异,从而使碳释放率不同,因此,如果在不同的土地利用方式下采取合理的管理措施,可使亚热带地区土壤成为巨大的土壤碳库。

论文目录

• Abstract（English）
• Abstract（Chinese）
• Abbreviation
• Chapter 1 Review of literature
• 1.1.Overview
• 2 fluxes'>1.2.Factors determining soil CO₂fluxes
• 1.2.1.Overview
• 1.2.2.Temperature and moisture
• 1.2.3.Fertilizer
• 1.2.4.Vegetation
• 1.2.5.Litter
• 1.2.6.Soil characteristics
• 4 fluxes'>1.3.Factors determining soil CH₄fluxes
• 1.3.1.Overview
• 1.3.2.Soil moisture
• 1.3.3.Temperature and moisture
• 1.3.4.Crop management and tillage
• 1.3.5.Fertilization
• 1.3.6.Landscape
• 1.3.7.Soil characteristics
• 2 fluxes'>1.4.Effect of land use on soil CO₂fluxes
• 4 fluxes'>1.5.Effect of land use on soil CH₄fluxes
• 1.6.Factors determining C sequestration capacity of the soil
• 1.6.1.Tillage and residue management
• 1.6.2.Carbon sequestration with application of manures
• 1.6.3.Carbon sequestration with organic agriculture
• 1.6.4.Effects of fertilization and straw/manure on soil C sequestration
• 1.6.5.Benefits of sequestering carbon
• 1.7.Aims
• 1.7.1.C fluxes and its determinants under different land uses
• 1.7.2.SOC pools under different land uses
• 1.7.3.C sequestration capacity of a paddy field
• Chapter 2 Materials and methods
• 2.1.Site description
• 2.1.1.Site 1
• 2.1.2.Site 2
• 2.2.Experimental design
• 2 fluxes between different land uses in Xianning'>2.2.1.Study 1:Differences of soil CO₂ fluxes between different land uses in Xianning
• 2.2.2.Study 2:SOC dynamics from different land uses during an incubation study
• 2 and CH₄ fluxes from different land uses in Zigui'>2.2.3.Study 3:Soil CO₂ and CH₄ fluxes from different land uses in Zigui
• 2 fluxes from different land uses in Zigui'>2.2.4.Study 4:Effect of microbial biomass and dissolved organic carbon and nitrogen on soil CO₂ fluxes from different land uses in Zigui
• 2.2.5.Study 5:Estimation of soil carbon sequestration potential of a paddy field
• 2.3.Soil sampling and analysis methods
• 2.3.1.Field studies
• 2.3.2.Incubation study
• 2.4.Measurement of other environmental factors
• 2.5.Measurement of gas fluxes
• 2 flux'>2.5.1 Soil CO₂flux
• 4 fluxes'>2.5.2 Soil CH₄fluxes
• 2.6.Estimation of net primary and ecosystem production
• 2.7.Model used for incubation study
• 2.8.Statistical analysis
• 2 flux among paddy,orchard,woodland and upland in Xianning'>Chapter 3 Differences in soil CO₂ flux among paddy,orchard,woodland and upland in Xianning
• 3.1.Overview
• 3.2.Results
• 2 fluxes'>3.2.1 Soil CO₂fluxes
• 3.2.2.Soil temperature,WFPS and dissolved organic carbon
• 2 flux versus soil temperature,WFPS and dissolved organic carbon'>3.2.3.Soil CO₂ flux versus soil temperature,WFPS and dissolved organic carbon
• 2 flux'>3.2.4.Predominating factors controlling soil CO₂flux
• 3.3 Discussion
• 2 fluxes'>3.3.1.Soil CO₂fluxes
• 2 fluxes'>3.3.2.Effect of land use on soil CO₂fluxes
• 2 fluxes'>3.3.3.Effect of environmental variables on soil CO₂fluxes
• 2 flux'>3.3.4.Predominating factors controlling soil CO₂flux
• Chapter 4 Carbon dioxide emissions in association with soil organic carbon pools from red soil under paddy,orchard,woodland,and upland in Xianning
• 4.1.Overview
• 4.2.Results
• 4.2.1.Soil characteristics
• 4.2.2.Characteristics of SOC decomposition
• 4.2.3.SOC pools and dynamics
• 4.2.4.Soil organic carbon vs soil properties
• 2 flux vs soil temperature and moisture'>4.2.5.Soil CO₂ flux vs soil temperature and moisture
• 4.3.Discussion
• 4.3.1.Soil properties
• 4.3.2.Carbon mineralization
• 2 fluxes'>4.3.3.Effect of soil moisture and temperature on soil CO₂fluxes
• 10'>4.3.4.Effect of soil moisture and temperature on Q₁₀
• 2 fluxes'>4.3.5.Effect of land use on soil CO₂fluxes
• 2 and CH₄ fluxes of upland,vegetable field,orchard and pine forest in Three Gorges Reservoir area'>Chapter 5 CO₂ and CH₄ fluxes of upland,vegetable field,orchard and pine forest in Three Gorges Reservoir area
• 5.1.Overview
• 5.2.Results
• 2 and CH₄ fluxes'>5.2.1.Seasonal and annual variations in CO₂ and CH₄fluxes
• 2 and CH₄ fluxes'>5.2.2.Land use effect on CO₂ and CH₄fluxes
• 2 and CH₄ fluxes'>5.2.3.Impacts of environmental variances on CO₂ and CH₄fluxes
• 5.3.Discussion
• 2 and CH₄ budgets'>5.3.1.Annual CO₂ and CH₄budgets
• 2 and CH₄ fluxes'>5.3.2.Effect of land use on CO₂ and CH₄fluxes
• 2 and CH₄ fluxes'>5.3.3.Effect of environmental variables on CO₂ and CH₄fluxes
• 5.3.4.Global warming potential
• Chapter 6 Effect of microbial biomass,and dissolved organic carbon and nitrogen on soil respiration in upland,vegetable field,orchard,and pine forest in Three Gorges Reservoir Area
• 6.1.Overview
• 6.2.Results
• 6.2.1.Environmental factors
• 6.2.2.Microbial biomass C and N,and dissolved organic C and N
• 2 fluxes'>6.2.3.Seasonal variations in CO₂fluxes
• 2 fluxes'>6.2.4.Land use effect on CO₂fluxes
• 2 fluxes'>6.2.5.Impacts of environmental variances on CO₂fluxes
• 6.3.Discussion
• 2 fluxes'>6.3.1.Annual CO₂fluxes
• 2 fluxes'>6.3.2.Effect of seasonal changes on CO₂fluxes
• 2 fluxes'>6.3.3.Effect of land use on CO₂fluxes
• 2 fluxes'>6.3.4.Effect of environmental variables on CO₂fluxes
• 2 flux'>6.3.5.Predominating factors controlling soil CO₂flux
• 2 emission in a red paddy soil（Ultisol）as affected by straw and nitrogen fertilizer applications:Implications for C sequestration'>Chapter 7 CO₂ emission in a red paddy soil（Ultisol）as affected by straw and nitrogen fertilizer applications:Implications for C sequestration
• 7.1.Overview
• 7.2.Results
• 7.2.1.Crop yield and biomass
• 2 fluxes'>7.2.2.Soil CO₂fluxes
• 2 flux'>7.2.3.Soil temperature versus soil CO₂flux
• 7.3.Discussion
• 2 fluxes'>7.3.1.Soil CO₂fluxes
• 2 fluxes'>7.3.2.Effect of crop on soil CO₂fluxes
• 2 fluxes'>7.3.3.Effect of N fertilizer on soil CO₂fluxes
• 7.3.4.Net primary and ecosystem production
• Chapter 8 Research evaluation and future needs for sustainability and global C storage
• 8.1.Land use effect on soil C budget
• 8.2.Management impacts on soil organic carbon
• 8.2.1.Land use
• 8.2.2.Future needs to characterize the effects of land use on SOC sequestration
• 8.2.3.Inorganic and organic fertilization
• 8.2.4.Future needs to characterize the effects of inorganic and organic fertilization on SOC sequestration
• 8.3.GHG emissions
• 2 emissions'>8.3.1.Reducing soil CO₂emissions
• 4 emissions'>8.3.2.Reducing soil CH₄emissions
• 2 and CH₄ fluxes'>8.3.3.Future needs to characterize CO₂ and CH₄fluxes
• Conclusions
• References
• Acknowledgement
• Appendix