[Effects of land use type and slope position on soil physical properties in loess tableland area]

Soil samples under different land use types and at different slope positions in the Wangdonggou watershed of loess tableland area were collected to determine their particle composition, bulk density (pb), and saturated hydraulic conductivity (Ks), and the effects of land use type and slope position on the soil physical properties were studied in virtue of the variation coefficient and non-parameter tests. The results showed that the physical properties of soil varied in horizontal direction and vertical profile, however at the same slope position or under the same land use type, the pb and particle composition were similar. In horizontal direction, Ks varied strongly, slit content and pb varied weakly, and clay and sand contents varied medially. In vertical profile, soil particles had a continuous distribution, but pb and Ks varied greatly in 0-25 cm layer. With the slope degree descended, soil contained more clay and had a higher pb, and Ks increased. At upper and middle slopes, soil physical properties were similar, and thus, could be merged into one in related researches. There was a significant difference in soil physical properties between grassland and other land use types, which was mainly due to the effects of slope position, but the soil physical properties in farmland and orchard were similar, indicating the important effects of human activities.