褐土与棕壤坡耕地细沟侵蚀发生的阶段性水沙变化

为深入探究辽西低山丘陵区坡耕地土壤侵蚀机理,以该区的典型土壤类型褐土和棕壤为研究对象,采用室内人工降雨模拟试验,研究3种坡度(5°,10°,15°)和3种降雨强度(40,60,80 mm/h)下细沟侵蚀发生的阶段性水沙变化过程。结果表明:褐土与棕壤坡面侵蚀过程可划分为3个阶段,即细沟侵蚀之前阶段、跌坎发育阶段和细沟侵蚀快速发育阶段;细沟侵蚀之前的面蚀阶段,同一坡度条件下,褐土与棕壤随雨强的增加,坡面流速呈增大趋势,而在同一雨强条件下,坡度对流速的影响并无明显规律;细沟侵蚀阶段,当坡度一定条件下,褐土与棕壤细沟内、细沟间的流速随雨强的增加而增大,当雨强一定时,褐土与棕壤随坡度的增加细沟间流速增加;细沟侵蚀阶段流速表现为细沟内流速坡面流速细沟间流速;细沟侵蚀快速发育阶段2种土壤产生的径流量占总径流量的80%以上,土壤侵蚀量占总侵蚀量均在70%以上,且棕壤对总体侵蚀量的贡献更稳定,更易发生细沟侵蚀。整场降雨的侵蚀方式是面蚀向细沟侵蚀的转变,坡面一旦发生侵蚀,细沟侵蚀对坡面总侵蚀的贡献更大。

Periodic Variation of Water and Sediment in Rill Erosion of Cinnamon Soil and Brown Soil Sloping Farmland

In order to further study soil erosion mechanism of sloping farmland in low mountain and hilly region of western Liaoning Province, we selected cinnamon soil and brown soil as research object, periodic variation of water and sediment in rill erosion was studied under three slopes (5°, 10° and 15°) and three rainfall intensities (40, 60 and 80 mm/h) by using artificial simulated rainfall system. The results showed that the erosion process of cinnamon soil and brown soil slope could be divided into three stages, which were the pre-rill erosion stage, the development of drop sill stage and the rapid development of rill erosion stage. At the surface erosion stage before rill erosion, the flow velocity of cinnamon soil and brown soil increased with the increasing of rainfall intensity under the same slope condition. However, the effect of slope on flow velocity was not obvious under the same rainfall intensity. At the rill erosion stage, the flow velocities of in and between rills of cinnamon soil and brown soil increased with the increasing of rainfall intensity under specific slope. The flow velocity between rills of cinnamon soil and brown soil increased with the increasing of slope gradient under specific rainfall intensity. At the rill erosion stage, the flow velocity followed the order of in rill > on slope > between rills. At the rapid development of rill erosion stage, the runoff of cinnamon soil and brown soil accounted for more than 80% of the total runoff, and the soil erosion accounted for more than 70% of the total erosion. The contribution of brown soil to total erosion was more stable, and rill erosion was more likely to occur. The erosion pattern of the whole rainfall was the transformation from surface erosion to rill erosion. Once slope surface erosion occurred, rill erosion contributed more to the total erosion.