An experimental study on the responses of spring snowmelt erosion to driving factors in a Chinese Mollisol soil

Snowmelt erosion, a major spring soil degradation process in the Mollisol region of China, is further exacerbated in the context of global warming. The mechanism of snowmelt erosion remains unclear due to the complex erosion process influenced by multiple factors during the melting period. In this laboratory study we examined the effects of three critical factors influencing soil erosion during thawing period: snowmelt flow rates (0.33 × 10⁻⁴, 0.67 × 10⁻⁴, and 1.32 × 10⁻⁴ m² s⁻¹), subsurface hydrologic conditions (seepage and drainage), and soil thaw depths (5 and 10 cm). The results indicated that seepage significantly aggravated sediment yield, with sediment yield increasing by 50% in comparison to the drainage treatments. Sediment yield was positively correlated with snowmelt flow rate, and as the flow rate increased from 0.33 × 10⁻⁴ to 0.67 × 10⁻⁴ m² s⁻¹, the sediment yield increased by more than 4 times, due to the enhanced runoff energy and sediment transport capacity. Path analysis confirmed that snowmelt flow rate and subsurface hydrologic condition were the dominant factors for snowmelt erosion (explaining 0.917 and 0.308 of the path coefficients, respectively) while the effects of soil thaw depth were relatively low (explaining 0.032 of the path coefficients). However, soil thaw depth had a substantial impact on rill morphology evolution; rills tended to erode horizontally toward the sidewalls at shallow thaw depths, and evolved vertically downward at deeper thaw depths. Additionally, runoff energy consumption (ΔE) was a suitable indicator for characterizing soil erosion on partially thawed slopes with a high Coefficient of Determination (R² > 0.70). In general, this study provides a scientific basis for a comprehensive understanding of snowmelt erosion dynamics, allowing development of more strategies for mitigating soil erosion in the spring and sustaining regional productivity in the Mollisol region of China.