Transitions in slope runoff generation mechanisms induced by land use change in the Loess Plateau, China

Large-scale land use change has been shown to have a significant impact on the underlying surface conditions, with consequences for soil erosion, river runoff, and sediment transport. The impact of land use change on soil infiltration capacity and whether the runoff generation mechanisms in typical watersheds of the Loess Plateau might change under strongly varying surface conditions remain unclear. This study selected three land use types in the Loess Plateau: forestlands, grasslands, and wastelands. Using a double-ring infiltrometer and artificial rainfall simulation, infiltration tests and rainfall-runoff experiments were conducted under different land use types to investigate the effects on soil properties, infiltration capacity, and slope runoff mechanisms. The results indicated that land use change significantly reduced the bulk density of shallow soils. Forestlands and grasslands exhibited significantly higher mean weight diameter and saturated hydraulic conductivity. Land use change effectively improved the infiltration characteristics. The infiltration characteristics of the soil vary across different soil layers. In the 0–30 cm soil layer, Ks (saturated hydraulic conductivity) made a significant contribution to soil infiltration performance. In the simulated rainfall experiments, subsurface flow was observed in both forestlands and grasslands. Due to land use change, the soil infiltration capacity was significantly enhanced, which in turn affected the transformation of runoff generation mechanisms. This suggests that changes in soil infiltration due to land use change lead to a shift in slope runoff generation mechanisms, potentially transitioning from a single surface infiltration excess overland flow mechanism to a combination of infiltration excess overland flow and subsurface flow mechanisms. These findings enhance the understanding of hydrological processes such as infiltration and runoff after land use change.