植被覆盖结构对坡面产流产沙的影响及调控机制分析

利用野外模拟降雨试验,以自然修复草本植被完整覆盖、地表覆盖、高层覆盖和无覆盖有根系等4种不同垂直覆盖结构为研究对象,分析了植被不同垂直结构对坡面产流产沙的影响作用。研究表明:(1)不同垂直覆盖结构条件下的坡面产流产沙特征差异明显,以无覆盖有根系坡面作对照,完整覆盖、地表覆盖及高层覆盖结构减流率分别为91.12%、83.28%和61.55%,减沙率分别为98.71%、96.10%和64.69%,完整覆盖结构对产流产沙过程的抑制作用最强;(2)试验条件下,植被完整覆盖、地表覆盖和高层覆盖可截留降雨1.85、1.01和0.84 mm,场次降雨截留率分别为1.73%、1.09%和0.90%;(3)坡面径流特征与植被覆盖结构有关,试验条件下,与无覆盖有根系坡面相比,完整覆盖、地表覆盖、高层覆盖坡面流速分别降低66.69%、53.47%和19.21%,径流深降低66.70%、51.17%、39.38%。植被垂直结构是影响坡面产流产沙的重要因素,仅用单一的覆盖指标难以充分反映植被对水沙的调控作用。研究成果对于定量评价不同植被覆盖结构的减水减沙作用有参考价值。

Effects of vegetation cover structure on runoff and sediment yield and its regulation mechanism

Using simulated rainfall experiment in the field,the effects of different vertical structures of natural remediation grass vegetation on sediment yield on slope were analyzed, including undisturbed vegetation cover,surface cover,vegetation cover above the surface and with root layer only without covers above. The experiment results showed that:(1) The characteristics were obviously different of runoff and sediment yield from different coverage structures on slope. Taking the slope with root layer only without covers above as a contrast, the runoff reduction rates of undisturbed vegetation cover, surface cover and vegetation cover above the surface were 91.12%, 83.28% and 61.55%, and the sediment reduction rates were 98.71%, 96.10% and 64.69%,respectively. The undisturbed vegetation cover has the stronger inhibitory effect on runoff and sediment yield. (2) Under 90 mm/h rainfall simulation conditions,3 kinds of vegetation cover structure including undisturbed vegetation cover, surface cover and vegetation cover above the surface could intercept rainfall of 1.85 mm, 1.01 mm and 0.84 mm respectively, and the interception rates were 1.73%, 1.09% and 0.90% in one simulated rainfall. (3) The characteristics of slope runoff were related to the structure of vegetation cover. Under the experimental conditions,compared with the slope with root layer only without covers above, the flow velocities on the slopes with undisturbed vegetation cover, surface cover and vegetation cover above the surface were decreased by 66.69%, 53.47% and 19.21%, respectively, and the runoff depths were decreased by 66.70%, 51.17% and 39.38%, respectively. Vertical structure of vegetation is an important factor to analyze the influence of vegetation on runoff and sediment yield on slopes. It is difficult to fully reflect the regulating effect of vegetation on water and sediment only using a single coverage index. The results provide conditions for quantifying the different vegetation cover structure of runoff and sediment reduction.