Spatiotemporal Dynamics and Driver Pathways of Soil Erosion in Qilian Mountain National Park (1990–2022) Under Ecological Restoration

Soil erosion in alpine ecosystems threatens biodiversity, ecosystem services, and SDGs, yet its spatiotemporal dynamics and drivers remain unclear. Using multi-source remote sensing (1990–2022), deep learning, and Random Forest, we assessed soil erosion in Qilian Mountain National Park, an ecotone between the Qinghai–Tibet Plateau and northwestern arid regions, offering a natural laboratory for advancing understanding of water erosion in fragile alpine–arid ecosystems. Results show a mean annual erosion of 2.77 × 10² t·ha⁻¹·yr⁻¹ across the whole national park. Over the past three decades, the conversion of bare land to vegetated ecosystems (5355 km²) has reduced soil erosion by approximately 5.36 × 10⁸ t. Bare land had the highest annual mean erosion (100.17 t·ha⁻¹·yr⁻¹), followed by cropland (10.03 t·ha⁻¹·yr⁻¹) and shrubland (7.58 t·ha⁻¹·yr⁻¹), while forest and grassland were <2.55 t·ha⁻¹·yr⁻¹. Slope and precipitation (contributing over 49.85% and 6.80% across ecosystems, respectively) were the dominant drivers of soil erosion, whereas vegetation covers consistently migrated erosion (−0.04 ≤ r ≤ −0.01). Human activity reduced vegetation cover (−0.15 ≤ r ≤ −0.08), thereby intensifying erosion. Overall, erosion intensity declined by 17.04% over the past three decades, yet management should prioritize bare land, cropland, and sensitive zones to strengthen restoration and prevent soil erosion.