Study on Water-Holding Capacity of the Top Soil of a Steppe Reserve in the Yunwu Mountains, Guyuan, Ningxia Hui Autonomous Region

The study was undertaken to determine the tendency and variation of the soil-water holding capacity during the restored vegetation community succession in a plot of former cropland bordering a typical steppe zone on the Loess Plateau. The curves of soil water characteristics measured by centrifugation showed: there was a high power function correlation between the soil moisture and the potential of soil water, which could be represented by θ=aS~b. Following the succession of the vegetations, the value a increased gradually. Soil water contents of various vegetations are different at the same range of soil water potential. The data indicated that the water content of soil covered with Stipa bungeana was the highest, while the land was the lowest in the slope, though at the same range of soil water potential. The soil water contents of other plant community successions reached the same level with the increase of soil water potentials. The vegetation succession lessened the soil bulk density and enhanced the soil porosity by increasing the soil organic matter and improving the soil construction; thus, affecting the soil-water holding capacity.