Nitrogen Budgets Research At Different Spatial Scales In Upstream Of Miyun Reservoir Watershed

Nitrogen is an important nutrient in the ecosystem. With the intensification of human activities, a large number of nitrogen into the biogeochemical cycles, and caused a series of environmental problems of groundwater pollution and eutrophication of water bodies. Thus, the study of nitrogen balance and its environmental effects, the scientific management of the regional nutrient and ecological environment protection and improvement, to promote the sustainable development of society has a very important significance. On the basis of the theory of nutrient balance, with upstream of Miyun reservoir watershed as the study area, nitrogen balance budget was studied. According to the data of actual survey and yearbook, with different land use as the study unit, nitrogen balance budget of typical small watershed was studied. Input, output and surplus of nitrogen at different watershed scales were estimated. And the composition of nitrogen balance was analyzed. The main conclusions are as followed:1-, Nitrogen surplus in upstream of Miyun reservoir watershed at amount of74045t. The main source of nitrogen input is atmospheric deposition and biological nitrogen fixation, the output is soil erosion. The low nitrogen use efficiency and higher rate of nitrogen surplus in the watershed. Fertilizer utilization rate was34%, feed efficiency was51%, and nitrogen surplus was59%. Upstream nitrogen surplus strength is higher than the downstream. White river is above Chao river basin. Miyun is high risk areas. Huairou, Yanqing, Xinglong classed as medium risk areas. Luanping, Chicheng, Fengning are low risk areas.2、 Nitrogen surplus in SYC small watershed was56.2kg/hm2. It is high risk areas. Differences in surplus nitrogen were observed among the five land use patterns in the following order:farm> economic forest> farmland> residential area> ecological forest, being12kg/hm2,443.55kg/hm2,140.63kg/hm2,53.02kg/hm2,2656.35kg/hm2. Anthropogenically enhanced nitrogen surplus into the ecosystem are about2.5～174times that from natural sources, indicating that human activities have seriously affected the nitrogen balance. Nitrogen use efficiency among the five land use patterns in the following order:residential area> farm> farmland> ecological forest> economic forest, indicating that with23～60%of nitrogen is not fully utilized. The surplus nitrogen not only results in waste of resources, increased eutrophication risk.3, Nitrogen surplus in TYXG small watershed was18.3kg/hm2. It is low risk areas. Differences in surplus nitrogen were observed among the five land use patterns in the following order:economic forest> residential area> ecological forest> farmland, being51.32kg/hm2,28.18kg/hm2,16.3kg/hm2,-50.98kg/hm2.4、It is low level of nitrogen surplus in the whole basin. The highest nitrogen surplus is Miyun County. There are two typical small watersheds in Miyun County, SYC and TYXG Nitrogen surplus in SYC and TYXG small watershed were56.2kg/hm2,18.3kg/hm2. In the in the whole basin scale, atmospheric deposition and soil erosion process is a dominant factor in the watershed nitrogen balance. It shows a smaller impact of human activities. Atmospheric deposition and soil erosion should pay attention to. In the in the typical small watershed scale, livestock is a dominant factor in SYC nitrogen balance, and farming is TYXG’s. The common feature in small watershed is that the fertilizer is the main input source, and atmospheric deposition in a considerable proportion of the input structure.