Background Erosion is one of the main causes of soil degradation worldwide. The Qinghai-Tibet Plateau is a vast area with obvious differences in topography, climate, and vegetation in different areas, covering almost all terrestrial soil erosion types. This brings a huge risk of erosion to the soil, which will seriously threaten its ecological barrier function. Quantitative assessment of soil erosion risk in the southern Qinghai-Tibet Plateau, so as to fully understand the status quo of soil erodibility in the study area, and put forward reasonable suggestions, which will help reduce the risk of soil erosion in the study area.

Methods In this study, a large-scale sampling was carried out in the southern Qinghai-Tibet Plateau, and four typical land use patterns (Farmland, grassland, woodland, and shrubland) in this area were taken as the research objects. The composition of soil particles and organic carbon mass fraction were measured, and the soil fractal dimension was calculated. Quantitatively assess the soil erosion risks of different land use types and different soil layers, and analyze the impact of soil particle size characteristics on soil erodibility.

Results The K value of soil erosion in the study area ranged from 0.022-0.036 t·hm²·h/(hm²·MJ·mm), the proportion of soil above medium erosion (K > 0.033 t·hm²·h/(hm²·MJ·mm)) was 43.19%, and the risk of soil erosion in the southern Qinghai-Tibet Plateau was higher. There were general differences in soil erosion among different land use types, soil erodibility was as follows: farmland > shrubland > grassland > woodland, and the soil erosion of farmland was significantly higher than that of the other three land use types (P < 0.05). In the soil vertical profile, the proportions of sample points with above-medium erosion (K > 0.033 t·hm²·h/(hm²·MJ·mm)) for the three soil layers (0-10, 10-20, and 20-30 cm) were 26.47%, 47.22% and 55.89%, respectively. Conversely, the proportions of sample points with below-medium and low erosion (K≤0.033 t·hm²·h/(hm²·MJ·mm)) were 73.53%, 52.78% and 44.11%, respectively. As soil depth increases, soil erodibility also increases, and soil erosion resistance decreases. Regression analysis revealed that the K value of soil erosion exhibited an exponential negative correlation with sand content and an exponential positive correlation with clay content and fractal dimension, both correlations being highly significant (P < 0.001).

Conclusions These results indicate that the soil erosion risk in the southern Qinghai-Tibet Plateau is relatively high, especially in farmland. We should start with the adjustment of land use, implement the policy of returning farmland to woodland and grassland, and increase vegetation coverage to reduce the risk of soil erosion in the study area and improve the benefits of soil and water conservation. The relevant research results can provide data support for the rational use of soil resources and ecological protection under different land use patterns in the southern Qinghai-Tibet Plateau.