Response of soil infiltration properties to water erosion in a Mollisol agricultural catchment, Northeast China

• Spatial patterns and main controlling factors of SIPs under extreme erosion were identified. • Crop roots enhanced infiltration in the mid-late growing season. • SIPs dominant factors differed between gully peripheries and slope areas. • Nonlinear hydrological responses increased local erosion risk. Soil infiltration properties (SIPs) play a pivotal role in regulating hydrological processes, mitigating soil erosion, and sustaining land productivity in agricultural landscapes. However, the spatiotemporal responses of subsurface processes and crop growth to water erosion remain insufficiently understood. This study investigates the spatiotemporal variations of SIPs and root growth traits in a typical agricultural catchment in the Mollisol region of Northeast China, and compare infiltration behavior between the gully periphery and the slope area within a severely eroded unit. Our findings show pronounced spatial and seasonal variations in SIPs: water erosion modifies soil physicochemical properties and SIPs within both geomorphic domains, while crop roots play a crucial role in enhancing infiltration, particularly during the mid‑ to late growing season. Utilizing Redundancy analysis (RDA) and Partial least squares path model (PLS-PM), we further quantified how soil structure and root traits jointly govern the spatiotemporal variation of infiltration, identifying distinct dominant factors between gully peripheries and slope areas. In the gully periphery, SIP variation is controlled mainly by erosion‑induced particle redistribution and soil organic matter dynamics, whereas in the slope area it is predominantly associated with crop root traits. The results highlight the complex interactions between soil properties and erosion, revealing nonlinear hydrological responses that contribute to localized erosion risks. This research provides essential insights into the mechanisms infiltration mechanisms in gully‑affected Mollisol catchments subjected to severe water erosion and offers critical information for developing targeted soil and water conservation strategies in vulnerable agricultural landscapes.