坡长对贵州喀斯特区黄壤坡耕地土壤侵蚀的影响

为揭示坡长对喀斯特坡耕地土壤侵蚀的影响作用，根据贵州省毕节石桥小流域水土保持监测点监测资料，研究了坡长为5，10，15，20，25 m的径流小区在次降雨条件下土壤侵蚀随坡长的变化规律。结果表明:喀斯特坡耕地坡面年内径流深随坡长增加表现为先减小后增大再减小；次降雨量小于30 mm时，径流深随着坡长的增加先增大后减小；次降雨量大于30 mm时，径流深随坡长增加表现为先减小后增大再减小。年内平均土壤侵蚀模数随着坡长的变化呈现一次函数关系的增长，拟合度R²=0.9217；次降雨量小于30 mm时，土壤侵蚀模数随着坡长的变化呈现先急剧增加后减小的趋势，峰值出现在10 m；次降雨量大于30 mm时，土壤侵蚀模数随着坡长的变化亦呈现一次函数的增长关系，拟合度R²=0.9146。在最大30 min雨强为25 mm/h和41.4 mm/h条件下，随着坡长的增加，径流深均表现为先减小后增大再减小，土壤侵蚀模数均表现为先增大后减小。

Influence of Slope Length on Soil Erosion in Yellow Sloping Farmland of Karst

This article studies the change rule of soil erosion and sediment yield with the slope length according to the monitoring data of soil and water conservation monitoring from runoff plots with the slope lengths of 5, 10, 15, 20 and 25 meters in Shiqiao small watershed in Bijie District in Guizhou Province. The results show that the annual runoff depths of slope surface in Karst sloping farmland decrease first, then increase and decrease later with the increase of slope length; when the rainfall is less than 30 mm, runoff depth increases first and then decreases with the increase of slope length; when the rainfall is greater than 30 mm, runoff depths decrease first, then increase and decrease later; the average soil erosion modulus within a year presents the linear function (R²=0.9217); when the rainfall is less than 30 mm, soil erosion modulus shows a trend of first sharp increasing and then decreasing, the peak value appears on the slope with length of 10 m; when the rainfall is greater than 30 mm, soil erosion modulus within a year also presents a linear function (R²=0.9146); under the condition of maximum thirty-minute rainfall intensities of 25 mm/h and 41.4 mm/h, the runoff depth decreases first, then increases and decreases later, and the soil erosion modulus increases first and then decreases with the increase of slope length.