Nitrogen and Phosphorus Loss in Different Land Use Types and Its Response to Environmental Factors in the Three Gorges Reservoir Area
三峡库区不同土地利用类型氮磷流失特征及其对环境因子的响应

The control of agricultural non-point source pollution (AGNPS) is an urgent problem to be solved for the ecological environment construction in the Three Gorges Reservoir Area. We analyzed the nitrogen (N) and phosphorus (P) loss and its response to environmental factors through monitoring the nutrient loss in different land use types after returning farmland to forest. The results showed that: 1The variability of nutrient concentration loss was strong in different land use types under different rainfall conditions, and the variability in the concentration of available nutrient was much higher than that of total nutrient; 2Compared to farmland, the annual phosphorus loss of different land use types was reduced by 84.53%-91.61% after returning farmland to forest; the reduction of annual nitrogen loss was not significant except Chinese chestnut forest (Castanea mollissima) and arbor forest, and the nitrogen loss was much higher than the phosphorus loss in all land use types; 3The particle phosphorus and nitrate nitrogen (NO3--N) were the main forms of the phosphorus and nitrogen loss, respectively; 4The nutrient loss of tea garden (Camellia sinensis) and bamboo forest (Phyllostachys pubescens) showed a good correlation with precipitation, and the correlation of phosphorus was better than that of nitrogen, but there was no significant relation with the rainfall intensity; 5The coverage of vegetation, tree layer and litter had a great influence on the loss of total nitrogen(TN). NO3--N loss was highly influenced by the ammonium nitrogen (NH4+-N) content in the surface soil, and P loss mainly by the total phosphorus (TP) and sand content in the soil.