Abstract: The Zhifang gully catchment,which model was established by 1:400 scales,has area of 8.27km².Under controlling artificially rainfall with intensity of 2mm/min and lasting 30min,the soil erosion and N loss of catchment model was studied for revealing the catchment N loss in runoff and sediment as effected by vegetation cover ratio.The results show that loss amounts of runoff ammonium and nitrate in vegetation cover ratios of 60%,40%,20% and 0%,were 58.08,44.31,25.16,13.71kg/km² and 85.50,74.06,63.95,56.23kg/km² respectively,the loss amounts of sediment organic matter and total N were 15.67,24.02,44.68,164.87t/km² and 0.81,1.18,1.98,7.51t/km² respectively.With delay of runoff yield time,the nitrogen concentrations in runoff and sediment drop off,whereas,the accumulation amounts of nitrogen loss rise gradually.Vegetable cover on soil is an available method to control soil erosion and total N loss,nevertheless,it might enhance soil available N loss.

Key words: Catchment model, Vegetation coverage, Nitrogen loss

摘要： 以8.27km²纸坊沟流域1:400模型为对象,在人工控制的条件下,模拟天然降雨(降雨强度2mm/min,历时30min),研究不同植被覆盖度对小流域土壤氮素随径流流失的规律。结果表明,当覆盖度为60%、40%、20%和0%时,土壤铵态氮流失量为87.08、44.31、25.16和13.71kg/km²,硝态氮流失量为85.50、74.05、63.95和56.23kg/km²,有机质流失量为15.67、24.02、44.68和164.87t/km²,全氮流失量为0.81、1.18、1.98和7.5t/km²。泥沙氮素含量随着产流时间的延长呈下降趋势,而流失累积量测呈逐渐增大趋势。植被覆盖虽能有效地减少土壤侵蚀和全氮的流失,却能增加土壤矿质氮的流失。

关键词: 小流域模型, 植被覆盖度, 氮素流失