Soil fractal features of typical forest stands in Jinyun Mountain, Chongqing City, Southwest China

Abstract

In order to explore the forest soil physical property in the Three Gorges Reservoir areas, the fractal theory was adopted to study the soil fractal features of the four typical forest stands (mixed Pinus massoniana-broadleaf forests, evergreen broadleaved forests, Phyllostachys pubescens forests and evergreen broadleaved shrub forests) in Jinyun Mountain, Chongqing City, and they were compared with arable land. It has been proposed that the model can be used for the analysis of the relationship between the fractal dimensions and the properties of forest soil. The impacts of fractal dimensions on the soil properties were analyzed with the elasticity analysis and marginal yield analysis. Results showed that the fractal dimension of particle size distribution (PSD), the micro-aggregate size distribution (ASD) and the soil pore size distribution (SPD) can be used as the indices to evaluate the soil structure. In the typical stands of Jinyun Mountain, the fractal dimension of PSD is 2.7–2.9, the ASD is 2.5–2.8, and the SPD is 2.3–2.8. The soil structure of evergreen broadleaved shrub forests performed best in PSD, ASD and SPD, and the soil of P. pubescens forests is the worst. There were some relationships among the PSD, ASD, SPD and some soil properties in the different forests and farmland. The related coefficients are over 0.5. Based on the elasticity analysis and marginal yield analysis, the effect of PSD was more than those of ASD and SPD. Obviously, the further study on the fractal theory application in soil structure and soil properties has important significance.