原位观测13C同位素解析土壤有机碳稳定性的研究

Carbon isotope (13C) observation is a new method to help understand the ecological processes in soil all the world. Agro-ecosystem has great potential for soil carbon sequestration. The stability of soil organic carbon (SOC) not only affects the carbon sequestration, but also is vital to a stable and high crop yield. In this study, we will monitor the soil CO2 emission and δ13C-CO2 in situ by a carbon isotope analyzer, and surface, 5cm, 10cm, 20cm, and 40cm soil layers will be observed in winter wheat fields treated by conventional tillage and no-tillage, straw mulching and no mulching. Furthermore, some environmental parameters such as air pressure, air temperature and humidity, soil moisture, soil temperature, and soil electrical conductivity will be measured in situ. For the analyzing in lab, soil architecture such as soil Bulk density, porosity, and aggregate, soil carbon component, those nutrient components which can affect the stability of SOC such as nitrate, ammonium, effective nitrogen, and humus. Based on these data, the objectives are to understand the influence of soil physical and chemical characteristics on soil carbon emission, to release the principle of soil carbon fraction how to controlled by tillage method ( and no tillage here) and straw mulching using the carbon isotope method, to illuminate the processes and mechanism of the stability of SOC. The results will Provide a scientific basis for SOC promotion and land productivity improvement.

原位观测碳同位素是研究土壤中生态学过程的新手段。农田生态系统对土壤固碳有着巨大的潜势，土壤有机碳稳定性不但影响土壤固碳，对农田稳产高产也至关重要。本研究拟以不同耕作和秸秆处理下华北冬小麦农田土壤为研究对象，通过对静态箱内0-40cm土壤CO2排放量、13C-CO2同位素以及空气和土壤温湿度等环境要素的原位观测，辅以不同生育期耕层土壤结构（如容重、孔隙度、团聚体等）、土壤碳组分、影响土壤有机碳稳定性的养分要素（如铵态氮、硝态氮、碱解氮和腐殖质等）、以及作物生长产量构成等进行野外监测与室内分析，解析土壤理化特性对土壤碳排放的影响，用碳同位素方法揭示耕作和秸秆还田对土壤碳排放各组分的影响机理，阐明耕作和秸秆影响土壤有机碳稳定性的过程与机制，为华北农田土壤有机碳的提升和土地生产力的提高提供科学依据。

农业活动对农田土壤和所处流域水体的温室气体排放产生影响，并具有独特的地域性特征。因此，定量衡量水土环境中温室气体排放对农业活动的响应，对于研究农田所在的水-土交互系统的碳氮水平衡具有重要意义。.为探究农田免耕和降雨变化对土壤CO2及其来源（自养呼吸和异养呼吸）排放的影响，研究组在华北平原禹城站设立定点原位观测试验，采用自动静态箱与全天即时测定的方法，连续测定了免耕和秸秆还田作用下农田土壤CO2排放特征。研究发现，短期免耕促进土壤呼吸，秸秆还田作用促进土壤CO2排放，但两者受年际气象要素影响极大。研究组在禹城试验站建立了河流中试生态系统，首次从控制试验角度定量证明了在不同的流速和养分条件下，流速决定了农业灌渠中CO2排放速率和DIC消耗，并印证探究了当地河流CO2和CH4的排放特征。开展的蒸渗仪试验表明，异常降雨年份，不同地下水位对土壤的N2O排放差异加大。.相关研究明确了农田耕作、灌溉和土地利用类型变化对水-土系统的温室气体排放的变化特征，显示当前极端天气多发对土壤水-土-气系统温室气体排放产生重要影响，表明土壤水分变化和灌溉过程对碳、氮排放的影响机制，对华北平原农田水土资源的合理管理和利用提供重要依据。.项目执行期间，共发表8篇论文（第一标注6篇），其中Sci论文5篇，中文论文3篇，并培养4名博士和1名硕士研究生毕业。组织和接待多次专家和学生参观试验样地和仪器设备，极大地推介了本研究方法和研究经验。