Effects of land use on spatial heterogeneity of soil bulk density, moisture and organic material in karst hilly depressions: An example of the Zhumashao depression of Nandong watershed

The purpose of this work was to explore the influencing factors of soil spatial heterogeneity in Karst hilly depressions. Taking the hill depression catchment of Zhumashao as an example, by the methods of classical statistics and geostatistics, spatial heterogeneity of soil bulk density and water content and organic matter were analyzed in view of different land uses, slopes and aspects. The results show that the soil organic matter is strongly varied with a coefficient of variation (CV) 0.71 while the soil bulk density and moisture are of moderate variation with CV 0.16 and 0.11, respectively. The soil bulk density is significantly negatively correlated with the moisture and organic matter with correlation coefficients -0.609 and -0.58, respectively. Geostatistics shows that the block-to-base ratio is between 0.78 to 0.97. The spatial variation caused by random part is large, the spatial autocorrelation is smaller, and the model fits well. Soil structure of the cultivated land is poor, with lowest organic matter and moisture content in the soil with largest bulk density, while the shrub is better. Soil bulk density in the north slope is higher than that of the south slope, while the CV is smaller than that of the south slope. And soil moisture content and organic matter on north slopes are lower than that of the south slopes. The effects of land use on spatial heterogeneity of soil are reflected in the comparison of different slope positions and directions. Under these effects, spatial variability of soil moisture, bulk density and organic matter increase from random parts, and spatial autocorrelation decreases. These information would be useful for prediction of soil property change and study in hilly depression areas.