粗质地土壤坡度和前期含水量对土壤侵蚀的影响

利用野外模拟降雨试验,研究了粗质地土壤裸地和苜蓿地在不同坡度(5°,15°,25°)、不同前期含水量(低、中、高)条件下坡面降雨产流、产沙的过程及其特征,以此探究该区退耕还草效益。结果表明:3种坡度条件下裸地和苜蓿地的产流过程在不同前期含水量下均为先增大后趋于稳定,不同坡度之间的径流量差异不显著,但泥沙流失量随着坡度的增大而显著增加,在降雨过程中先增大达到峰值趋于稳定波动,裸地的波动幅度大于苜蓿地。2种处理的前期含水量对径流量以及平均入渗率的影响均达显著水平,裸地在相同的坡度下,前期含水量由低水平增加到中水平、低水平增加到高水平,径流量分别增加38.2%~52.8%,39.7%~42.8%,苜蓿地径流量分别增加27.3%~77.8%,45.5%~91.1%。坡度对泥沙流失量及含沙率影响显著,在相同的前期含水量下,裸地由5°增加到15°,15°增加到25°的泥沙流失量分别增加96.3%~268.7%,6.9%~40.3%,苜蓿地的泥沙流失量分别增加81.1%~384.2%,61.7%~169.9%。在相同坡度和前期含水量下,苜蓿地的径流量和泥沙流失量均显著低于裸地。研究结果表明粗质地土壤前期含水量和坡度显著影响坡地土壤侵蚀过程和总量,植被不但因为冠层拦截而减少径流,而且因为耗水量增加,降低了土壤前期含水量而减水减沙。

Effect of Soil Slope and Antecedent Soil Water Content on Soil Erosion in Coarse Texture Soil

Through the simulated rainfall experiment,the effects of slope and antecedent soil water content on the process of rainfall runoff and sediment on bare land and alfalfa land of coarse texture soil were investigated.The experiment treatment included three slopes(5°,15° and 25°) and three antecedent soil water content (low,middle and high).The results showed that the processes of runoff on bare land and alfalfa land were at first increased and then leveled-off under different slopes and antecedent soil water content,and the effects of slopes on runoff volume were marginal.Sediment losses were greatly increased with the increasing slopes,which were increased firstly and then tended to be stable,and also greater changes occurred in bare land.Both of the runoff volume and the mean infiltration were significantly affected by antecedent soil water content.Under the same slope gradient,when antecedent soil water content increased from low to middle,and from low to high,the runoff volume of bare land increased 38.2％～52.8％,and 39.7％～42.8 ％,respectively,while the runoff volume of alfalfa land increased 27.3％～77.8％ and 45.5％ ～91.1％,respectively.Slopes had significant influences on sediment losses and sediment concentration.Under the same antecedent soil water content,when slope increased from 5° to 15°,and from 15° to 25°,the sediment losses of bare land increased 96.3％～268.7％,and 6.9％～40.3％,respectively,whereas the corresponding values of alfalfa land increased 81.1％～384.2％,and 61.7％～169.9％,respectively.The results showed runoff volume and sediment losses of alfalfa land were significantly lower than bare land at same slope and antecedent soil water content.The findings indicate that antecedent soil water content and slope of coarse texture soil play important roles on the process and amount of soil erosion.The vegetation not only reduces runoff by canopy interception,but also decreases antecedent soil water content through consuming soil moisture.