Variability of the Soil Physical Properties on the Loess Plateau
黄土丘陵小流域土壤物理性质的 空间变异

The degree of spatial variability of the soil physical properties and the ability of environmental attributes to predict that variability were studied in Da Nangou catchment (3.5 km2) on the Loess Plateau, China. The soil physical properties including soil texture (sand, silt, clay), bulk density, saturated soil moisture content, aggregate stability, soil cohesion, stable infiltration rate were measured at 111 plots across the catchment. It is found that the spatial variation is small for soil texture, bulk density and saturated soil moisture content, moderate for aggregate stability and cohesion, and great for stable infiltration. The spatial distribution of the soil physical properties is due to the joint-influence of land use and topography, and the dominant factors differ for different soil physical properties. There is significant difference in the soil physical properties between different land use types as determined by the correlation analysis. The sand content shows the lowest value while the silt content exhibits the highest values on the woodland, and the silt content is lower for the fallow land than the other land use types. The bulk density exhibits the greatest values for the woodland while it is the lowest for the cropland. For the saturated soil moisture content, it is the greatest for the shrub land while it is the lowest for the woodland. The woodland also is the strongest in the aggregate stability, while the cropland is the weakest. The soil cohesion shows higher values for the shrub land, woodland, wasteland and the fallow land, but it displays a lower value for the cropland. The shrub land is the greatest in the stable infiltration rate, while the intercropping land is the lowest. Based on the correlation analysis, it is indicated that a significant correlation exists between the soil physical properties and the terrain indices. The sand content is lower and the silt content is higher on the concave slope than the other surface types, however, the straight slope shows an opposite picture.