Effects of vegetation loss and soil erosion intensity on soil carbon dynamics across landscape position: Evidence from China’s Loess Plateau

The role of plant in regulating soil carbon cycling is well recognized. However, this regulatory function is increasingly threatened by human-driven vegetation loss and intensified erosion, especially in ecologically fragile ecosystems. Despite their frequent co-occurrence, the interactive effects of these stressors on soil organic carbon (SOC) dynamics remain poorly understood. In this study, we conducted a field experiment on China’s Loess Plateau to investigate the impacts of vegetation loss and soil erosion intensity on soil carbon processes, focusing on enzyme activities and SOC dynamics across landscape position. Our results showed that vegetation removal significantly reduced SOC by 0.63 %, along with declines in enzyme activities. These effects were more pronounced in surface soils (0–10 cm), under moderate erosion intensity (SOC: 1.19 % reduction), and in northern erosion-prone sites such as Suide (SD) in erosion areas. In contrast, deposition zones exhibited comparatively weaker responses in both SOC and enzyme activities following vegetation removal. Vegetation loss altered SOC regulation across geomorphic zones. In erosion areas, the controlling factor shifted from erosion intensity to climate, whereas in depositional zones, the contribution of nutrient stoichiometry became more pronounced . Structural equation modeling revealed contrasting pathways: enzyme suppression drove SOC loss in erosion zones, while nutrient stoichiometry shifts governed SOC in depositional zones. Our findings demonstrated that anthropogenic vegetation loss intensifies erosion-induced SOC loss by shifting its biogeochemical regulation, highlighting the critical need for integrated vegetation restoration and erosion control to stabilize soil carbon in vulnerable landscapes.