不同放牧强度对流域降雨径流中氮磷流失的影响

在呼伦贝尔草原克鲁伦河流域选取轻度放牧、重度放牧及不放牧草场，利用降雨模拟器进行降雨模拟试验，研究了不同放牧强度草场的地表物理性质、植被类型对降雨产流、营养元素流失等因素的影响。结果表明:在20，45，65 mm/h降雨强度下重度放牧草场产流时间最短，不放牧草场产流时间最长。径流量及径流系数总体规律显示为重度放牧草场 > 轻度放牧草场 > 不放牧草场。3种放牧强度草场的氮磷流失量均随雨强的增加而增大。降雨产流初期氮磷浓度相对较高，随径流时间增加逐步下降，最后达到稳定。径流量与氮磷含量之间存在二项式显著相关关系。

Effects of Different Grazing Systems on Nitrogen and Phosphorus Losses Along the Rainfall Runoff

A rainfall simulator was used to determine the influence of the surface physical properties and vegetation types as well as three systems of grazing (light, heavy and no grazing) on the rainfall infiltration and runoff yield in pastures in the Kherlen basin of Hulun Buir. The results showed that, under three rainfall intensities: 20, 45, 65 mm/h, the runoff duration in the heavy grazing pasture was the shortest, while runoff duration in the no grazing pasture was the longest. The runoff volume and runoff coefficient showed a general trend: heavy grazing pasture > light grazing pasture > no grazing pasture. As the rainfall intensity increased in the three grassland grazing systems, the losses of nitrogen and phosphorus from these systems also increased. The levels of nitrogen and phosphorus in the initial rainfall runoff were quite high, and then declined gradually and tended to become stable with the increase of runoff duration. There was a significant binomial correlation between runoff volume and the levels of nitrogen and phosphorus in runoff.