Fractal characteristics of soils under different land-use patterns in the arid and semiarid regions of the Tibetan Plateau, China

Abstract

The application of fractal geometry to describe soil structure, soil dynamics, and physical processes within soil is becoming an increasingly useful tool that allows for a better understanding of the performance of soil systems. The fractal dimension of particle-size distributions (PSDs) is often used to estimate several properties in soils, such as texture and moisture characteristics. Land use patterns largely influence the PSD of a soil, but information on how this occurs for different land use patterns is very limited. In this study a modified number-based method has been applied to characterize fractal dimension of PSDs of Cryic Aridisols soils from the Tibetan Plateau, China. The various soil samples were obtained from four different types of land-use patterns: a land with integrated grass and sparse brushwood cover (IGB, ∼10–30% grass and ∼10% brushwood), a well-covered grassland (WCG, > 75% grass), a bare land without any vegetation (BL), and a cropland used for growing wheat (CL). Analysis of the soils revealed that (1) the sand content of the top 15 cm of soil increased from 50.14 to 85.61 g/kg, (2) the soil carbon decreased from 9.94 to 3.11g organic carbon per kg soil, (3) the soil nitrogen content decreased from 0.223 to 0.844 g nitrogen per kg soil, and (4) the fractal dimension of PSD decreased from 2.92 to 2.45, following the order IGB > WCG > BL > CL. Thus, land use had considerable influences on the fractal dimension of PSD and various other soil properties. Further, this study shows that the fractal dimensions of PSD can be a useful parameter to monitor soil degradation induced by land use patterns and changes.