Quantifying ridge-induced slope correction and its impact on soil erosion estimation in black soil sloping croplands of Northeast China: Mechanisms and Mitigation

Conventional erosion models systematically overestimate soil loss in the typical black soil region of Northeast China, because they ignore how ridge cultivation redirects runoff. We corrected this by calculating the slope gradient along the ridge direction, which substantially alters the regional risk profile. Our analysis of three representative counties—Moqi, Baiquan, and Yushu—showed that the correction increased the gentle-slope area (<1.5°) by 26%, 29%, and 20%, and reduced the area of soil loss rate exceeding 1 mm/a by 1,244 km 2 , 619 km 2 , and 565 km 2 , respectively. Mechanistically, slope gradient dominates the black soil layer loss, with its interaction with ridge direction as a secondary driver. Using these corrected rates, complete loss of black soil layer at eroding sites is a century-scale process, exceeding 270 years. These findings argue for risk-based conservation: low-risk areas may not require strict contour ridging, while higher-risk zones demand optimized ridge direction to minimize the slope gradient along ridge direction, supported by residue mulch in furrows to enhance infiltration and stabilize ridges. Our work provides the quantitative basis for such tailored strategies by integrating ridge-induced topographic correction into erosion assessment.