不同人为管理措施坡面地表微地形变化特征及其对渗流的响应

Variation Characteristics of Slope Surface Microtopography and Its Response to Seepage Under Different Artificial Management Measures

探究不同人为管理措施坡耕地地表微地形变化特征,阐明地表微地形变化对渗流响应,以期为紫色土坡耕地水土流失的有效防治与人为管理措施的合理布设提供科学依据。以平整坡面、穴播坡面和垄作坡面为研究对象,基于室内人工模拟渗流试验,开展5°和15°紫色土坡面微地形变化特征研究。结果表明:(1)渗流试验前后平整坡面、垄作坡面和穴播坡面微地形半方差函数在0~135°和180°~315°方向上呈中心对称分布,随地表坡度的增加分布范围逐渐缩小,且具有明显的方向性。渗流条件下,平整坡面和穴播坡面微地形各向异性的变化趋势较为一致,而垄作坡面微地形空间变异性较强。(2)渗流条件下,3种人为管理措施坡面高程均集中于-20~0 mm的变化区域,穴播坡面和垄作坡面高程值的分布较平整坡面离散。(3)与5°坡面相比,15°平整坡面地表糙度的变化对渗流的响应更为明显,且糙度变化率呈平整坡面>穴播坡面>垄作坡面;渗流作用下,各坡面中、下坡位地表糙度变幅较大。坡面初始起伏程度越剧烈,微地形对渗流侵蚀作用的骤变响应越明显。地表糙度可作为刻画坡面微地形响应渗流变化的指标,可较好地实现中、下坡位土壤侵蚀—沉积空间分布的表征,以期为阐明紫色土坡面微地形变化与渗流侵蚀的耦合关系提供理论依据。

In order to explore the characteristics of slope surface microtopography(SSM)change of slope farmland under different artificial management measures,and clarify the response of SSM change to seepage,so as to provide a scientific basis for the effective prevention and control of soil erosion and the reasonable layout of artificial management measures,this study took the flat slope(CK),artificial digging slope(AD)and ridge tillage slope(RT)as the research object.Based on simulated seepage experiment,the variation characteristics of SSM on 5°and 15°purple soil slopes were studied.The results showed that(1)The semivariogram of SSM on the three slopes showed a central symmetric distribution in the directions of 0~135°and 180°~315°before and after the seepage test,and the distribution range gradually decreased with the increasing of slope gradients and exhibited obvious directivity.Under seepage condition,the variation trend of SSM anisotropy on CK and AD was relatively consistent,while the spatial variability of SSM on RT was strong.(2)Under seepage condition,the range of elevation variation on the three kinds of slopes was mainly concentrated in-20 mm to 0 mm,and the distribution of slope elevation of relative rough slopes(AD and RT)was more dispersal compared with CK.(3)Compared with 5°slope,the response of soil surface roughness(SSR)change to seepage was more obvious on 15°flat slope.The change rate of SSR followed the order of CK>AD>RT.Under seepage condition,the SSR varied greatly at the midslope and downslope.The more intense the initial fluctuation of slope surface was,the more obvious the abrupt change response of SSM to seepage erosion.In this study,soil surface roughness could be used as an indicator for describing the response of SSM changes to seepage condition,which could efficiently characterize the spatial distribution of soil erosion-deposition at the middle and downslope,so as to provide a theoretical basis for clarifying the coupling relationship between the variation of SSM and seepage erosion on purple soil slope.