Fractal characteristics of soil under ecological restoration in the agro-pastoral transition zone of Northern China

Soil particle size distribution (PSD) is an important physical attribute due to its great influence on soil properties related to water movement, productivity, and soil erosion. In this study we use classical and geostatistical methods to identify the changes and characteristics of PSD and selected chemical properties in soil at the 0-20 cm layer from different vegetation covers of ecological restoration along the agro-pastoral transition zone of northern China. The relationships between the fractal dimension of the PSD (D-m) and selected soil properties are discussed. The results show that: (1) with the accumulation of vegetation cover, sand content dropped from 867 to 180 g kg(-1), and soil organic matter and nutrients increased significantly; (2) D-m ranged from 2.327 to 2.854. The higher the contents of clay, the higher the fractal dimension and the greater the vegetation, (3) significant linear regressions were found between D-m and soils properties such as sand, silt, clay. organic matter, total N, available N, P, K, cation exchange capacity and CaCO3. Therefore, the fractal model can be used as a main index to indicate the establishment of the restoration ecosystem and its degree of stabilisation.