坡耕地氮素面源污染产生的实质是水蚀过程驱动下氮素从土相向水相的运移，而微生物对水-土界面的氮素转化有重要的引擎作用。但是，微生物对水蚀影响下氮转化迁移的响应、适应及反馈作用依然不清晰。以紫色土区典型坡耕地为研究对象，通过坡耕地径流小区高频监测坡面径流和壤中流不同形态氮素的流失，同时用氮同位素标记技术结合原位树脂芯方法同步测定水蚀影响下土壤氮素的矿化和硝化，定量刻画水蚀激发作用下不同形态氮素的转化、释放及输移特征，分析水蚀作用下不同赋存形态氮素在单次降雨下的流失特征及季节性叠加效应；利用第二代高通量测序和荧光定量等分子生物学技术，分析水蚀影响下坡耕地氮循环微生物群落结构的丰度、分布和变化特征，明确与坡面氮素转化流失相关的关键微生物类群；运用典范对应分析和结构方程模型，解析水蚀驱动下坡耕地氮素转化流失与氮循环功能微生物的联动关系，阐明水蚀驱动过程中氮素面源污染发生发展的微生物调控机制。

The essence of land source pollution is the migration of reactive nitrogen at water and soil interface. The water erosion process is an important driving factor for the transfer of land nitrogen in soil - water interface, and the soil microorganism is the most closely related to nitrogen transfer. The nitrogen cycling and different N microbial communities is mainly affected by water erosion. However, reactive nitrogen transforms at water and soil interface and the abundance of the different N cycling microbial communities driven by water erosion process are still poorly understood. The objective of the project is to determine reactive nitrogen dynamics changed with the distributions and compositions of N cycling microbial communities under different water erosion state. Runoff plots would be used for high frequency monitoring of N Losses from runoff and subsurface flow on slope farmland. Simultaneous determination of mineralization and nitrification of soil nitrogen under water erosion by 15N tracing method combined with in situ resin core method. The Linkage between the absolute abundances of NFGs with reactive nitrogen under different erosion state will be assessed. The project will analyze the difference the relative abundances of NFGs among water erosion control treatments. The relationship between different forms N contents with N cycling microbes to invest energy in N supplying mineralization and fixation processes that invest energy in ammonia oxidization to balance the soil stoichiometry in the intensive water erosion soils. The mainly controlled factors for driving the nifH will be analyzed to know the microbial demand for N. The microbial N storages and the leaching, runoff and sediment loaded NO3- potentials will be investigated under different soil water control treatments. These potentials relationship with the soil microbial communities under the different water erosion state will be analyzed. The project will estimate how changes of N cycling microbes invest their energy at the molecular scale with the N microbial communities driven by water erosion processes.