Variations of soil infiltration in response to vegetation restoration and its influencing factors on the Loess Plateau

Soil infiltration is essential in the hydrological cycle, fulfilling plant water requirements, particularly in semi-arid regions such as the Loess Plateau. However, comprehensive characterization of soil infiltration responses to different vegetation restoration types remains unclear. Therefore, this study aims to examine the effects of revegetation on soil infiltration by conducting field experiments with nine representative plant species across five vegetation restoration types. Specifically, we focused on how revegetation affects soil and root properties to determine key factors impacting soil infiltration. The results showed that artificial forestland and natural grassland exhibited the most substantial effects on soil properties. Natural grassland exhibited the highest soil aggregate stability and organic matter content. Root length density and root surface area increased after vegetation restoration, most notably in artificial forestland. Root characteristics were positively correlated with aggregate stability, soil organic matter, and porosity. An increase in root surface area significantly enhanced the steady infiltration rate and saturated hydraulic conductivity (P < 0.01). Except for economic forestland, all types of vegetation restoration improved soil infiltration properties, especially notable in Artemisia sacrorum and Platycladus orientalis. The soil infiltration properties in forestland surpassed those in natural grassland, artificial grassland, and shrubland. Random Forest Regression (RFR) suggested that soil particle size, porosity, and aggerate stability were key predictors of soil infiltration properties. Partial least squares structural equation modeling (PLS-SEM) indicated that soil infiltration rates were altered by root-mediated changes in soil porosity. Additionally, soil organic matter exerts an indirect positive effect on infiltration rates by influencing soil aggregate stability. These findings are crucial for evaluating hydrological processes and devising more effective ecological restoration and soil and water conservation strategies in the Loess Plateau.