Assessment of cropland soil erosion patterns and driving factors in Northeast China through semi-monthly enhanced modeling

Soil erosion is thinning the fertile black soil in the croplands of Northeast China. However, the spatial patterns, temporal dynamics, and driving factors of cropland soil erosion under the combined effects of freeze-thaw processes, vegetation cover changes, and rainfall erosivity remain insufficiently quantified. This study constructed the Semi-Monthly Enhanced Chinese Soil Loss Equation (SE-CSLE) by incorporating the Freeze-Thaw Adjustment Factor for Soil Erodibility (Ka) and Composite Tillage Factor (Tc) into the Chinese Soil Loss Equation (CSLE). It was applied to analyze cropland soil erosion patterns in Northeast China from 2003 to 2023. The Random Forest analysis showed that Ka and Tc had relative importance values of 23% and 18% among erosion drivers. Temporal comparison with sediment discharge showed generally consistent variations, although the degree of agreement varied among years. Compared with CSLE and other erosion estimates, SE-CSLE yielded the highest NSE (0.551) and the lowest PBIAS (12.363%) based on runoff plot observations. Spatially, soil erosion was mainly controlled by the topographic factor (LS), with steeper and higher areas experiencing more severe erosion. The annual average erosion rate was 7.78 t ha −1 year −1 , and the average semi-monthly soil erosion rate was 0.32 t ha −1 period −1 . Cropland erosion showed an increasing trend from 2003 to 2023. Within a year, soil erosion increased rapidly from April to May due to sparse vegetation and soil thawing and peaked in late June and early July. From the perspective of reducing erosion risk, maintaining straw cover until mid-May in mountainous areas and adjusting straw removal and sowing timing in other croplands may help support erosion control. These findings highlight the need for soil conservation measures that account for regional conditions and seasonal erosion risks in the croplands of Northeast China.