Abstract: Fractal theory deals with the natural figures and images with self-similarity but without characteristic length, which offers an effective tool to quantitatively study complicated systems such as soil. Based on this theory, the fractal characteristics of soil particle size distribution under the 12 subalpine coniferous forests in Western Sichuan were studied, and the results showed that the fractal dimension of soil particles in surface layer ranged from 2.5209 to 2.7978. This fractal dimension only had a very significant correlation with the content of <0.001 mm soil particles. No significant correlations were observed between thisfractal dimension and the contents of soil organic matter, total nitrogen and pH, but there was a very significant correlation between the contents of soil organic matter and total nitrogen. The quantitative symbolization of the characteristics of subalpine coniferous forest soil by the fractal dimension of soil particle size distribution was discussed in the paper.

Key words: Nemipterus bathybius, Fisheries biology, Optimum catchable size, ELEFAN technique, Northern South China Sea