Temporal Emergence and Slope Dependence of RUSLE-Based Erosion Reduction Associated with Cropland Abandonment in Northeast China’s Black Soil Region

Cropland abandonment is expanding, but the timing and slope dependence of modelled erosion contrasts and residual soil loss remain poorly resolved. The study reconstructed continuous abandonment in Northeast China’s black soil region using 30 m annual land cover data (2000–2023) and 30 m RUSLE-based water erosion estimates (2000–2020), with local contemporaneous continuously cultivated controls. By 2020, land with event-time Age >10 represented 48.91% of continuously abandoned cropland. The relative reduction metric was small and uncertain at the cropland-exit event anchor (Age 1; 2.13%), reached 40.56% in the first complete post-exit year (Age 2), and remained at 47–50% during Ages 4–17. The operational stable reduction criterion was met earlier on 0–5° slopes than on steeper land, where early and long-term contrasts were weaker. Across 6040 10 km × 10 km cells with continuous abandonment, model-based residual loss totalled 1.090 × 106 t yr−1. Unadjusted 15 km Getis–Ord Gi* hot spots at ≥95% confidence occupied 15.0% of all cells but contained 55.5% of residual loss; two high-loss zones occupied 22.20% of abandonment-containing cells but contained 64.9% of residual loss. Continuous abandonment was associated with lower modelled hillslope water erosion without eliminating absolute pressure. Because regional field validation was unavailable, priorities for recently abandoned moderate-to-steep slopes and high-loss areas remain indicative pending field confirmation.