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

Abstract

AbstractThe Daliangshan region (DLS) is characterized by significant vertical differentiation in human activity and land use owing to the high elevation gradient, which may affect the soil erosion pattern in the vertical direction. However, the spatial variability of soil erosion rates along a hillslope at the catchment scale remains poorly understood. In this study, we used the cesium‐137 tracer technique to estimate soil erosion rates under different land uses and vertical zones from a small agricultural catchment, the Luowugou catchment in the DLS. Ten plots comprising four typical vertical zones (valley, low mountain, middle mountain and sub‐alpine) and five land‐use types (sloping farmland, grassland, abandoned farmland, forest land and horizontal terrace) were selected. In addition, two parallel downslope transects were built in each plot, and soil samples were collected at 3–7 m intervals along these transects. The results indicated that the soil erosion rates on sloping farmland (4.82 kg·m−2·y−1) and grassland (4.09 kg·m−2·y−1) were significantly higher than those on abandoned farmland (0.91 kg·m−2·y−1) and forest land (0.80 kg·m−2·y−1). In contrast, the horizontal terrace showed net deposition, with a deposition rate of 0.62 kg·m−2·y−1. The erosion rates varied across different zones, with the low mountain zone having 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 valley zone having the lowest erosion rate (1.28 kg·m−2·y−1). Furthermore, there were significant correlations (P < 0.05) between the soil erosion rates from different vertical zones and the proportion of sloping farmland, implying that sloping farmland plays a dominant role in shaping soil erosion along a vertical gradient. These comparisons suggest that the highest soil erosion rate occurred in the low mountain zone, indicating that the steeply sloping farmlands, resulting from migration from high‐altitude areas, have intensified soil erosion in the vertical zone. These findings highlight the role of agricultural activities originating from sloping farmlands in influencing soil erosion across different vertical zones, which has important implications for mitigating soil erosion and optimizing agricultural layout in the region.