Abstract:Rainfall infiltration through soil profile forms a key process of water cycle in the critical zone of terrestrial ecosystem. The hydrological function of soil pedons on transporting and accumulating rainwater constructs the foundation of forestland on soil and water conservation in mountainous area. To study impacts of vegetation cover and topographic position on soil hydrologic features of mountain area, three separated hillslopes covered with different vegetation in a typical catchment of the Dalaoling Forest Region were selected as the study area, where just located at 40km upstream of the Three Gorges Dam. Undisturbed soil cores were sampled with cutting rings from upslope and downslope positions. Saturated hydraulic conductivity and soil water characteristic curves of these soil cores were measured indoors, using constant water head method and centrifugal method, to analyze the influence of vegetation cover and topographic position on soil hydrological parameters and water storage. The results indicated that soil infiltration ability of evergreen forest land was the largest, and its soil saturated hydraulic conductivity was 7.8-322.81 cm/d, which was relative greater than that of deciduous forest soil (0.33-137.03 cm/d) and grassland soil (0.84-115.80 cm/d). Variation between different topographic positions revealed that the saturated hydraulic conductivity of upslope sites greater than that of downslope sites. Compared with the less difference between soil saturated water content, capillary moisture capacity and field capacity of six experimental sites varied significantly, and the two capacity parameters of grassland soil (20.77%-50.39%) were greater than that of forestland soil. Soil capillary moisture capacity, field capacity and wilting water content of upslope sites were less than those of downslope sites according to the comparison between the sites under the same vegetation coverage. Soil storage capacity varied apparently among six sites. The percentage of reservoir capacity obtained from field capacity accounting for total soil water storage capacity was largest in grassland sites, at 63.25%, while that of evergreen forestland sites was the least with only 55%. Comparison among topographic positions indicated the result of downslope sites was larger than that of upslope sites. Correlation analysis between soil water characteristic parameters and soil properties showed saturated hydraulic conductivity had significant positive relation with soil total porosity and organic matter content, and significant negative relation with soil bulk density. Soil saturated water content, capillary moisture content and field water capacity were significantly positively correlated with soil total porosity, organic matter content and silt particle content, and negatively correlated with soil bulk density and sand particle content. In conclusion, the soil water holding capacity of grassland was the largest among all observed sites, which was conducive to accumulate soil water, while evergreen forestland had the largest water infiltration rate which was prone to recharge underground water. For different topographic positions, downslope sites had larger soil water storage than upslope sites.