降雨和汇流对黑土区坡面土壤侵蚀的影响试验研究

东北黑土区上坡汇流对坡面土壤侵蚀有重要影响,因此辨析降雨和汇流对黑土区坡面土壤侵蚀的影响对农田土壤侵蚀防治有重要意义。通过设计不同降雨强度和汇流速率以及二者组合的模拟降雨及上方汇流试验,分析了降雨和汇流对黑土坡面侵蚀的影响及其贡献。试验处理包括两个降雨强度(50 mm/h和100 mm/h)、两个汇流速率(50 mm/h和100 mm/h,即:10 L/min和20 L/min)、以及4种不同降雨强度和汇流速率的组合((50+50)mm/h、(50+100)mm/h、(100+50)mm/h和(100+100)mm/h)。结果表明,在50 mm/h和100 mm/h上方汇流引起的坡面侵蚀量仅分别是50 mm/h和100 mm/h降雨引起坡面侵蚀量的1.9%和0.6%;当降雨强度和坡上方汇流速率分别由50 mm/h增加至100 mm/h时,降雨试验处理下的坡面侵蚀量增加6.1倍,汇流试验处理下的坡面侵蚀量增加3.2倍,说明降雨对坡面土壤侵蚀的影响显著大于汇流的作用。在降雨和汇流组合试验中,总供水强度(降雨强度+汇流速率)为150 mm/h时,降雨强度为100 mm/h和汇流速率为50 mm/h组合试验的坡面侵蚀量是降雨强度为50 mm/h和汇流速率为100 mm/h组合试验坡面侵蚀量的7.9倍。在相同汇流条件下,降雨强度由50 mm/h增加到100 mm/h时,降雨强度的增加对坡面侵蚀量的贡献率为89.6%-99.5%;而在相同降雨条件下,坡面汇流速率由50 mm/h增加100 mm/h时,汇流速率的增加对坡面侵蚀量的贡献率为17.2%-78.7%,说明在东北黑土区防治坡面汇流对坡面土壤侵蚀影响也尤为重要。

An experimental study on the impacts of rainfall and inflow on hillslope soil erosion in typical black soil regions

Upslope runoff has a great influence on hillslope soil erosion in typical black soil regions. However, few attempts have been made to clearly distinguish the effects of rainfall and upslope runoff on the hillslope soil erosion. Therefore, quantifying the contributions of rainfall and upslope runoff to the hillslope soil erosion is important, which will provide a scientific basis to prevent and control the hillslope erosion in the black soil regions. This study used simulated rainfall and inflow experiments to investigate how rainfall and inflow affect hillslope soil erosion and estimated their contributions to soil loss in typical black soil regions. The black soil used in this experiment was collected from the Yushu city in the Jilin Province and the experiment was conducted in the simulation rainfall hall of the Institute of Soil and Water Conservation. The set of rainfall simulator with lateral spraying nozzles, 16 m above the ground, were used to simulate the rainfall. An overflow tank, attached to the upper end of the soil pan, was used for supplying the inflow. The soil pan (8 m long, 3 m wide, and 0.5 m deep) was divided into two sub-soil pans by separation of PVC sheets. The experimental design included two rainfall intensities (50mm/h and 100 mm/h), two inflow rates (50 mm/h and 100 mm/h, equal to 10 L/min and 20 L/min, respectively), and combinations of two rainfall intensities and two inflow rates (50 mm/h rainfall + 50 mm/h inflow, 50 mm/h rainfall + 100 mm/h inflow, 100 mm/h rainfall + 50 mm/h inflow, 100 mm/h rainfall+ 100 mm/h inflow). All experiments were run at a 10° slope gradient and the duration was 100 min. Each treatment had two replications. During the experiment, runoff samples were collected every 2 min with a 15 L bucket and the weight of the dried sediment was used to calculate the erosion rate. Results showed that soil loss caused by 50 mm/h and 100 mm/h inflow rates only occupied 1.9% and 0.6% of soil loss induced by 50 mm/h and 100 mm/h rainfall intensities, respectively. With increasing rainfall intensity from 50 mm/h to 100 mm/h, the soil loss increased 6.1 times, and with increasing inflow rate from 50 mm/h to 100 mm/h, the soil loss increased 3.2 times. The results indicated that the influence of rainfall intensity on soil loss is greater than that of inflow rate. Regarding the combination treatments of rainfall and inflow, when the total water supply was 150 mm/h, the soil loss under 100 mm/h rainfall intensity + 50 mm/h inflow rate was 11.52 kg, which was 7.9 times higher than that under 50 mm/h rainfall intensity + 100 mm/h inflow rate. Under remaining 50 mm/h inflow rate or under 100 mm/h inflow rate, when the rainfall intensity changed from 50 mm/h to 100 mm/h, the increased rainfall intensity contributed to 89.6%-99.5% of the soil loss. At keeping 50 mm/h rainfall intensity or under 100 mm/h rainfall intensity, when the inflow rate varied from 50 mm/h to 100 mm/h, the increased inflow rate contributed to 17.2%-78.7% of the soil loss. These results indicate that controlling the upslope runoff is also an important way for reducing the hillslope soil erosion in typical black soil regions.