Spatial variability of soil moisture on hillslope in cluster-peak depression areas in Karst region

Spatial pattern and variability of surface(0～5, 5～10, 10～15 cm) soil moisture on hillslope were analyzed combining with classical statistics and geo-statistics with data measured by linear sampling method in Karst cluster-peak depression areas. Results show that under the condition of special land use structure on the slope (natural vegetation, abandoned cropland and cultivated land distributed along the slope), the surface soil moisture content decreases from upslope to downslope, and they are medium variability along the longitudinal and horizontal directions on the hillslope. The variability of soil moisture along horizontal direction is greater than that along longitudinal direction for special soil distribution, topography and physiognomy conditions. Land use type and degree of slope are key factors that affected the distribution and variability of surface soil moisture on the slope. The results from Semi-variogram analysis indicate that the surface soil moisture has significant nugget effect, very great sill, and middle or strong spatial correlation on the slope. Despite of the complicated land use structure, topography and thin rocky soil on the hillslope, the surface soil moisture has good variable structure and spatial continuity as a whole. It is viable to apply Geo-statistics method to study the spatial variability of soil moisture in Karst area.