不同放牧制度对呼伦贝尔草原径流中磷流失模拟研究

为了探究不同放牧制度对干旱半干旱地区草原土壤磷元素流失的影响,以呼伦贝尔砂质草原为研究对象,通过设置不同降雨强度,选择自由放牧、轮牧、休牧草场进行人工模拟降雨试验,利用混合深度模型模拟磷流失过程。结果表明:在4种雨强下,自由放牧草场总磷流失量最大,是休牧草场的1.31~1.50倍,是轮牧草场的1.59~1.74倍。颗粒态磷为草场土壤磷素的主要流失形式,其含量为溶解态磷的2.2~3.7倍。混合深度模型模拟结果显示,不完全混合模型的优于完全混合模型,并且在雨强较高情况下的模拟效果较好。在雨强小于1.5mm/min降雨事件中,放牧制度对磷元素流失影响显著(p0.05),轮牧草场磷流失最少。因此,适当的将呼伦贝尔草原自由放牧草场向休牧和轮牧草场转变,将有利于减少草场磷元素流失及草原生态可持续发展。

Study on Effects of Different Grazing Systems on Phosphorus Loss in Surface Runoff in Hulunbair Grasslands

The Hulunbair sandy grassland was used as the research object, and studied the effects of different grazing systems on phosphorus characteristic and phosphorus loss in surface runoff in arid and semi-arid grassland. We simulated rainfall with different intensities to study phosphorus concentration changing of surface runoff under three types of grazing systems such as no grazing, rotation grazing and free grazing. The effective mixing depth model was used to simulate the process of phosphorus loss from soil. Conclusions were as follows: Under different rainfall intensities, phosphorus runoff loss of free grazing system was the highest; its phosphorus loss was 1.31 to 1.5 times for no grazing grassland and 1.59 to 1.74 times for rotation grazing grassland. Particulate phosphorus was the major form phosphorus in the runoff and its content was 2.2 to 3.7 times higher than dissolved phosphorus. According to the result of experimental data fitting, the incomplete mixing model was better than the complete mixing model, and the model could simulate accurately for the case of higher rainfall intensity. The different grazing systems had significant influences on phosphorus losses in runoff under the rainfall intensity less than 1.5 mm/min. The phosphorus losses in rotation grazing grassland were the lowest. So, if we gently changed the grazing systems from the free grazing to no grazing and rotation grazing, the phosphorus loss situation would be decreased, which also would be helped for ecologically sustainable development in grassland.