关键词: 三峡库区, 消落带, 坡地, 磷素, 径流流失

Abstract: Water fluctuation zone is an important riparian zone in the Three Gorges Reservoir area. Eutrophication could be exacerbated as the spontaneous and disorder reclamation of water fluctuation zone by local famers likely induce substantial soil phosphorus loss into receiving water bodies in the Three Gorges Reservoir. However, phosphorus loss characteristic via overland flow and interflow from sloping cropland in the water fluctuation zone of the Three Gorges Reservoir is unclear. In this study, plot experiments were conducted to study the characteristics of phosphorus loss via overland flow and interflow from sloping cropland in the water fluctuation zone of the Three Gorges Reservoir from 2011 to 2013. Results showed that the average concentration of total phosphorus in overland flow and interflow per runoff event were 0.848±0.153 mg/L and 0.140±0.006 mg/L in the conventional fertilization treatment, respectively. Particulate phosphorus was the main form in overland flow, while bioavailable phosphorus dominated in interflow. Annual phosphorus loss flux via overland flow for the conventional fertilization treatment was 0.236±0.004 kg/hm2, accounting for 70.2% of total hydrological phosphorus loss flux. By contrast, annual phosphorus loss flux via interflow for the conventional fertilization treatment was only 0.100±0.003 kg/hm2 that only accounted for 29.8% of total hydrological phosphorus loss flux. Our results indicated that overland flow was the main way of phosphorus loss from slope croplands in the water fluctuation zone of the Three Gorges Reservoir. However, phosphorus loss via interflow could not be ignored because its dominant form was bioavailable phosphorus. Moreover, compared with conventional fertilization, the optimized fertilization treatment reduced phosphorus losses of overland flow and interflow by 45.3% and 40.0%, respectively, which could represent an important practice of controlling phosphorus losses from sloping cropland in the water fluctuation zone of the Three Gorges Reservoir via reducing nitrogen fertilizer.

Key words: Three Gorges Reservoir, water fluctuation zone, sloping cropland, phosphorus, runoff loss