Flow Detachment of Soils under Different Land Uses in the Loess Plateau of China

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Land use has a significant effect on soil properties, and therefore on soil erodibility. In many cases, land use controls soil erosion to a greater extent than does climate change or other system properties, yet only a few studies have quantified the effect of land use on soil detachment rates. This study was conducted to evaluate the effect of land use on soil detachment of natural, undisturbed soil samples, which were taken from fields under five typical land uses in the Loess Plateau of China. Flow discharges ranged from 0.25 to 2.0 L s-1 and slope gradients varied from 8.8% to 46.6%. The results indicated that soil detachment rates were significantly influenced by land uses. Cropland soil was most easily detached, followed by grassland, shrub land, wasteland, and woodland soils. The average ratios of detachment rates of cropland soil to grassland, shrub land, wasteland, and woodland soils were 2.05, 2.76, 3.23, and 13.32, respectively. Detachment rates were shown to be a power function of flow discharge and slope gradient (R2 > 0.93, NSE > 0.87). Both critical shear stress and erodibility were affected by land use. The different land uses in this study resulted in erodibility ranging from 0.0021 to 0.164 s m-1 and critical shear stress ranging from 2.08 to 6.30 Pa. No superiority was found if shear stress was replaced by stream power for detachment prediction, and either one could simulate rill detachment rates well. The result indicated that soil detachment rates in rill erosion could be well simulated by hydraulic parameters of stream power, slope, and runoff density and by soil properties of clay content, bulk density, aggregate median diameter, and soil strength. Further studies are needed to quantify the potential effects of plant root systems on detachment rates and to investigate the potential temporal variability of soil detachment rates.