Vegetation restoration and fine roots promote soil infiltrability in heavy-textured soils

Abstract Soil degradation impairs ecosystem functions, and vegetation restoration is a major eco-engineering method that is used to restore soils globally. Despite the fundamental role that plants play in enhancing soil functions and ecosystem services, little is known about the relationships among root traits, soil physical properties, and water infiltration. The objectives of this study were to therefore evaluate changes in soil infiltrability due to different vegetation types and identify soil properties and root trait predictors of variation in soil infiltrability. The influences of four plant species (two gramineous grasses and two leguminous shrubs) on physical properties of soil and water infiltration in heavy-textured soils with 43 % clay content following five years of restoration after surface soil removal were investigated. These data were subsequently incorporated into a conceptual path model to quantify the direct and indirect effects of root traits and root-induced soil properties on infiltration. Soil organic matter, aggregate stability, soil total porosity, and non-capillary porosity were significantly higher in planted soil than in bare soil (p   shrub-planted > bare soils. The infiltration rates during the initial and steady states were 63 % and 38 % higher in grass-planted soils than in shrub-planted soils, respectively. Among all evaluated root traits, fine root length density was the best predictor of these changes. Furthermore, the conceptual path model explained 82 % of the variance in water infiltration and confirmed the important role of roots in soil infiltration. Modeling indicated that this might not be a direct effect, but is rather mediated via soil physical properties like soil aggregate stability and soil porosity. These observations have important implications for designing efficient strategies in restoration of human-induced disturbed soils to mitigate overland flows and erosion.