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采用人工模拟降雨方法,从坡面水动力学角度,结合土壤抗冲性分析,对不同坡度和雨强组合下牧草调控黄土高原风蚀水蚀交错区绵沙土坡面侵蚀机理进行了定量研究,为揭示植被调控土壤侵蚀机理及黄土高原水土保持植被选择提供科学参考.结果表明:覆盖度约为40%的牧草沙打旺能够有效控制坡面土壤侵蚀,减沙效益达70%以上,而且根系减沙效益大于草冠.裸坡、只有根系作用的坡面和整株牧草作用的坡面水流流速与雨强、坡度均呈V=DJ0.33i0.5的函数关系,其中,J为坡度比降,i为雨强(mm·min-1),下垫面不同,综合系数D取值不同.牧草根系和冠层能够显著减小流速,增加阻力,根系的减速作用大于草冠,而增阻作用小于草冠.根系调控坡面阻力主要通过增加坡面泥沙颗粒阻力实现,而草冠通过增加坡面形态阻力和波阻力来实现.利用薄层水流坡面产沙概念模型对土壤抗冲性进行评价,得到试验条件下裸坡、只有根系作用的坡面和整株牧草作用的坡面的临界径流切应力分别为0.533、0.925和1.672Pa.
Using artificial rainfall method, from the slope hydrodynamic point of view, combined with the analysis of soil anti-scourability, we conducted a quantitative study on the slope erosion mechanism of grass mound on the Loess Plateau, Vegetation control of soil erosion mechanism and the selection of soil and water conservation vegetation in the Loess Plateau to provide a scientific reference.The results showed that: the coverage of about 40% of the grass Astragalus can effectively control slope erosion, sediment reduction benefits of more than 70%, and the sediment reduction The benefit is greater than the grass canopy.Besides bare slope, only the root effect of the slope and the role of the entire grassland slope flow velocity and rainfall intensity, slope showed a function of V = DJ0.33i0.5, where J is the gradient, i For rain intensity (mm · min-1), the underlying surface is different, and the value of comprehensive coefficient D is different.The forage roots and canopy significantly reduce the flow rate and increase the resistance, the root decelerating effect is greater than that of grass canopy, The resistance of root system to slope resistance is mainly achieved by increasing the resistance of sediment particles on the slope, while the canopy crown is realized by increasing the shape resistance and wave resistance of the slope surface. Monovalent, bare slope obtained under the test conditions, the effect of slope and only root runoff critical shear stress slope of the whole action of forage were 0.533,0.925 and 1.672Pa.