Abstract
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 Dclay<Dsilt<Dsand. However, the values of Dsilt and Dsand 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 (Dvi) are higher than the corresponding parameter values from the United States Department of Agriculture (Dvi(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: Dsilt>Dsilt(U)>Dsand (U)>Dsand and Dsilt>Dsilt(U)>Dsand>Dsand(U), respectively. As it is compared with all Dvi, the Dsilt has the most significant correlativity to the soil texture and organic matter in different land uses of the typical purple soil watersheds. Therefore, Dsilt 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.
Highlights
The fractal theory was proposed and established by Mandelbrot (1977, 1982) [1,2], which is a method of describing systems with non-characteristic scales and self-similarity
3.1 Characteristics of soil particle size distribution by land use According to the analysis of the relationship between soil particle size and cumulative volume percentage distribution in six main land-use types, including Pinus massoniana Lamb, Robinia pseudoacacia L, Citrus reticulata Blanco, Zea mays L, Ipomoea batatas) and Setaria viridis, the doi:10.1371/journal.pone.0122842.g002
The linear relationship between soil particle size and cumulative volume percentage is shown in Fig 2. (Fig 2 shows that the linear relationship between soil particle size and cumulative volume percentage of the six landuse types, and the upper size boundaries in the measured clay domain and silt domain of purple soil were approximately 5.74μm and 286.85μm.). These values are not totally in agreement with the upper size limit for fractal behavior determined by the United States Department of Agriculture (USDA) classification standard, in which the upper size limits for clay, silt, and sand domains are 0.002 mm, 0.05 mm, and 2 mm, respectively
Summary
The fractal theory was proposed and established by Mandelbrot (1977, 1982) [1,2], which is a method of describing systems with non-characteristic scales and self-similarity. This theory has been utilized to quantitatively describe the characteristics of the soil particle size distribution (PSD), which is important in hydrological conductivity, solution transportation, and soil. Response of Soil Fractal Features to Different Land Uses
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