Effects of landscape positions on soil resistance to rill erosion in a small catchment on the Loess Plateau.

Landscape position has significant effects on soil properties and plant roots, and thus probably affects soil resistance to rill erosion, reflected by rill erodibility and critical shear stress. However, the potential effects of landscape positions on soil resistance to rill erosion are still unclear. Therefore, this study was conducted to investigate the spatial variations in soil resistance to rill erosion under different landscape positions, and to identify the main factors controlling these variations in a small catchment of the Loess Plateau. 540 undisturbed soil samples were collected from 18 typical sampling sites of natural succession grassland under six landscape positions and subjected to scour under different flow shear stresses. The results showed that landscape position significantly affected the spatial variation of rill erodibility. The mean rill erodibility decreased gradually from the top of ridge to footslope and increased linearly with elevation. Significant differences were detected in rill erodibility between three grass species. No significant difference was found in critical shear stress between six landscape positions. Soil erosion and soil water content dominated the regular spatial changes of soil properties and root mass density along six landscape positions. All of these factors collectively resulted in the regular decrease of rill erodibility from the top of ridge to footslope. A negative relationship was identified between critical shear stress and clay content. Rill erodibility could be satisfactorily estimated by the median soil grain size, soil cohesion, water stable aggregate and root mass density. [ABSTRACT FROM AUTHOR]