典型薄层黑土区前期地表风蚀作用影响坡面水蚀的研究

Study on Effect of Surface Wind Erosion on Hillslope Water Erosion in Regions of Typical Thin Layered Mollisol at Early Stages

水力、风力、冻融作用等多营力叠加的复合土壤侵蚀是东北黑土区土壤侵蚀的重要特征,但目前该地区复合土壤侵蚀研究还相当薄弱,进而影响黑土复合侵蚀防治措施的精准实施。采用室内风洞试验和模拟降雨试验相结合的方法,分析前期地表风蚀作用对黑土坡面水蚀的影响。结果表明:(1)前期地表风蚀作用使坡面产流时间明显滞后,但其显著增加了坡面水蚀量(P<0.05),且坡面径流和水蚀强度均随前期风蚀作用的风速增加而增加。(2)前期地表风蚀作用对后期坡面水蚀产生了明显的正向效应,地表风蚀作用对坡面水蚀的贡献随前期风蚀作用的风速增大而显著增加,且雨强较小时前期地表风蚀作用对后期坡面水蚀的影响更加明显。在50和100mm·h^(-1)两种降雨强度下,9、12和15m·s^(-1)风速的风蚀作用对坡面水蚀量的贡献率分别为24.2%、45.4%、80.3%和17.5%、26.3%、46.3%。(3)地表风蚀作用增加坡面水蚀的主要原因一方面是前期风蚀作用使土壤抗侵蚀能力指标(地表土壤抗剪强度和土壤硬度)减小;另一方面是风蚀过程中的风沙颗粒运动冲击、摩擦地表,使坡面形成了风蚀凹痕微形态,改变了后期坡面水蚀过程的径流路径,加快了坡面径流汇集,增加了坡面径流流速和减少了水流阻力,从而增加了坡面径流侵蚀力和搬运能力;此外,前期风蚀作用也为后期坡面水蚀过程提供了侵蚀物质。本研究结果不仅丰富了复合土壤侵蚀理论,也为黑土区土壤侵蚀防治提供了科学依据。

【Objective】Soil erosion in the Mollisol region of Northeast China is a compound process occurring under the joint effect of water,wind,freeze-thaw and other external forces.However,so far researches on compound soil erosions in this region are still far from adequate,thus affecting precise implementation of soil erosion control measures.【Method】This paper applied a research strategy of combining an indoor wind erosion simulation experiment with a simulated rainfall experiment to analyze effects of early-stage surface wind erosion on hillslope water erosion in the Mollisol region of China.【Result】Results showed:(1)the foregoing wind erosion significantly delayed the generation of hillslope runoff,but it significantly increased hillslope runoff and soil loss(P<0.05),with both rates rising with wind velocity;(2)The foregoing wind erosion did have a positive effect on the following hillslope water erosion,and contribution of the former to the latter was increased significantly with rising wind velocity,but declined with rainfall intensity from 24.2%,45.4%,80.3%,down to 17.5%,26.3%and 46.3%,respectively,when the wind was at 9,12 and 15 m·s^(–1),respectively;(3)The contribution of wind erosion was attributed on the one side to the effect of wind erosion reducing soil erosion resistance by lowering shear strength and impactness of the surface soil,and on the other side,to the effect of wind erosion causing generation of aeolian sand particles that impacted and scrubbed the land surface in their wind-driving movement,thus forming micromorphology of wind erosion dents,and in turn altering runoff paths on the slope,speeding up pooling of runoff on the slope,increasing flow velocity and reducing flow resistance,and eventually intensifying surface runoff erosion and sediment transport.In addition,the foregoing wind erosion also provided erosion material for the later hillslope water erosion.【Conclusion】All the findings of this study not only enrich the theory of compound soil erosion,but also provide a scientific basis for soil erosion control in the Mollisol region of China.