Effects of vegetation restoration on soil infiltrability and preferential flow in hilly gully areas of the Loess Plateau, China

Soil infiltration plays a critical role in soil hydrological processes. Land use/cover changes are generally considered to influence soil infiltration. However, the effect of long-term vegetation restoration on the soil infiltration capacity and infiltration pattern is poorly understood. In the present study, we analyzed the infiltration capacity with a double ring infiltrometer and detected the degree of preferential flow using a dye tracer in a typical loess hilly gully catchment of China. Additionally, we identified the relationships between soil characteristics and infiltration capacity and preferential flow. The results showed that (1) converting cropland to forest, shrubland and grassland generally enhanced the soil infiltration capacity. Compared with cropland, the steady-state infiltration rate (SIR) and saturated hydraulic conductivity (Ks) increased by 135 % and 155 % in shrubland, by 76 % and 91 % in forest, and by 22 % and 23 % in grassland. (2) Land use changes markedly increased the degree of preferential flow, following the order of shrubland > forest > grassland > cropland. (3) The decline in soil moisture (SM) and bulk density (BD) and the increase in total porosity (TP), macroporosity (MP) and soil organic matter (SOM) could cause higher infiltration capacity and preferential flow. SM and TP were the dominant factors affecting soil infiltrability, while MP was the greatest contributor to variations in preferential flow. Our findings demonstrated that vegetation restoration had a positive impact on soil infiltrability and preferential flow. This effect should be considered when assessing the influence of vegetation restoration on water resources in the Loess Plateau and other arid and semiarid regions.