Variation in soil erosion rate under typical land uses and vertical zones in an agricultural catchment of the Daliangshan region, Southwest China

Identification the effects of land use and vertical zone on soil erosion is vital to optimize land management in mountainous areas. In this study, the variation in soil erosion rate under typical land uses and vertical zones in a small agricultural catchment of the Daliangshan region (DLS), Southwest China, were evaluated using the cesium-137 tracer technique. Ten plots representing five land uses with four typical vertical zones (valley, low mountain, middle mountain and subalpine) were selected herein. Two parallel downslope transects were built in each plot, and soil samples were collected at 3-7 m intervals along these transects. The results showed that the sloping farmland (4.82 kg·m^-2·y^-1) and grassland (4.09 kg·m^-2·y^-1) soil erosion rates were significantly higher than those in abandoned farmlands (0.91 kg·m^-2·y^-1) and forest lands (0.80 kg·m^-2·y^-1), and horizontal terraces were dominated by net deposition (with erosion rate of -0.62 kg·m^-2·y^-1). The low mountain zone yielded the highest erosion rate (5.65 kg·m^-2·y^-1), followed by the middle mountain (2.96 kg·m^-2·y^-1) and subalpine (1.46 kg·m^-2·y^-1) zones, and the lowest erosion rate (1.28 kg·m^-2·y^-1) was observed in the valley zone. In addition, the soil erosion rate showed significant correlations (P<0.05) with sloping farmland proportion. The results indicate that land use controls soil erosion, and the vertical zone associated with land use patterns, topography, and human activities impact soil erosion variation. The low mountain zone near the catchment lower reaches has the highest erosion rate, largely because it is dominated by steep sloping farmlands and affected by immigration from high-altitude areas. Our findings highlight the importance of agricultural activities in sloping farmlands regarding soil erosion acceleration and the role of vertical zone in soil erosion rate impact. Appropriate management measures must be implemented to prevent soil erosion in the low mountain zone with increasing anthropogenic activities.