植被空间配置对凸型坡侵蚀及泥沙颗粒分选的影响

针对黄土高原水土流失严重的问题,结合该地区缺水的现状,在有限的植被措施条件下,以凸型坡为研究对象,将草带布设在上坡面5种不同位置,利用室内放水冲刷试验对不同植被空间配置下坡面侵蚀过程和泥沙颗粒分选特征进行了研究,阐明了植被能够有效发挥水土保持功效的作用,并初步提出在低植被覆盖度下植被发挥水土保持功效的最优植被空间配置。结果表明:(1)不同植被空间配置的产流强度Cv值为10.26%～15.50%,产流强度的波动程度较小,其中配置A的产流强度与配置B和配置F的产流强度表现为显著性差异(p0.05),不同植被空间配置的产沙强度Cv值均在26.00%以上,配置A的产沙强度与其他配置的产沙强度均表现为显著性差异(p0.05),在坡面布设草带对产沙过程的影响大于对产流过程的影响;(2)在凸型坡的上坡面种植植被后,总产流产沙量与裸坡(配置A)相比均有不同程度的降低,其中配置F的减水效益达到19.65%,配置B的减沙效益高达70%以上;(3)不同植被空间配置下泥沙颗粒平均重量直径(MWD)的平均值表现为配置A配置F配置D配置E配置C本底物配置B,MWD的平均值随着产流时间的延长逐渐稳定并接近于本底物,在有植被覆盖坡面的水力侵蚀条件下,侵蚀颗粒以细颗粒为主,粉粒含量较高,砂粒含量相对较小,并且植被布设位置距离坡顶越远更容易侵蚀0.002～0.05 mm的粉粒。研究结果有助于加深植被空间配置对坡面侵蚀产沙作用机理的理解。

Effects of Vegetation Spatial Position on Convex Slope Erosion and Sediment Particle Size Fractionation

Aiming at the serious problem of soil erosion on the Loess Plateau,combined with the current situation of water shortage in the region,under the condition of limited vegetation measures,the convex slope was taken as the research object,and the grass belt was laid on 5 different positions on the upslope,and the indoor water discharge was used. The experiment studied the slope erosion process and sediment particle size fractionation characteristics under different vegetation spatial positions,and clarified that the vegetation can effectively exert the soil and water conservation effect,and primitively proposed the optimal position of soil and water conservation effects under low vegetation coverage. The results showed that: (1) The Cv value of the flow intensity of different vegetation spatial positions is between 10.26% and 15.50%,and the fluctuation of the runoff intensity is small. The runoff intensity of position A and the runoff of position B and position F were small. The intensity showed a significant difference (p<0.05),and the Cv value of the sediment yield in different vegetation spatial positions were above 26.00%. The sediment yield intensity of the position A showed significant difference with sediment yield of other positions (p<0.05). The effect of laying grass strips on the slope on the sediment production process was greater than the impact on the runoff process. (2) After planting vegetation on the upslope of the convex slope,the total runoff yield was reduced to a different extent compared with the bare slope (Position A),and the water reduction benefit of the position F was 19.65%. The sediment yield reduction benefit of position B was as high as 70% or more. (3) The average value of the average weight diameter (MWD) of sediment particles in different vegetation spatial position was: Position A > Position F > Position D > Position E > Position C > Substrate > Position B,the mean value of MWD gradually stabilized and approached the substrate with the prolongation of runoff generation time. Under the condition of hydraulic erosion with vegetation coverage,the erosion particles were mainly fine grains,the content of powder grains was higher,and the content of sand was relatively small. The farther the vegetation was from the top of the slope,the easier it was to erode 0.002~0.05 mm of powder. This study will help to deepen the understanding of the spatial distribution of vegetation on the mechanism of convex slope erosion and sediment production.