Response Characteristics of Soil Fractal Features to Different Land Uses in Typical Purple Soil Watershed

As a fundamental characteristic of soil physical properties, the soil Particle Size Distribution (PSD) is important in the research on soil moisture migration, solution transformation, and soil erosion. In this research, the PSD characteristics with distinct methods in different land uses are analyzed. The results show that the upper bound of the volume domain of the clay domain ranges from 5.743μm to 5.749μm for all land-use types. For the silt domain of purple soil, the value ranges among 286.852~286.966 μm. For all purple soil land-use types, the order of the volume domain fractal dimensions is D(clay)<D(silt)<D(sand). However, the values of D(silt) and D(sand) in the Pinus massoniana Lamb, Robinia pseudoacacia L and Ipomoea batatas are all higher than the corresponding values in the Citrus reticulate Blanco and Setaria viridis. Moreover, in all the land-use types, all of the parameters in volume domain fractal dimension (D(vi)) are higher than the corresponding parameter values from the United States Department of Agriculture (D(vi)(U)). The correlation study between the volume domain fractal dimension and the soil properties shows that the intensity of correlation to the soil texture and soil organic matter has the order as: D(silt)>D(silt)(U)>D(sand) (U)>D(sand) and D(silt)>D(silt)(U)>D(sand)>D(sand)(U), respectively. As it is compared with all D(vi), the D(silt) has the most significant correlativity to the soil texture and organic matter in different land uses of the typical purple soil watersheds. Therefore, D(silt) will be a potential indictor for evaluating the proportion of fine particles in the PSD, as well as a key measurement in soil quality and productivity studies.