Fractal feature of soil structure and reflection on soil properties in different regeneration patterns of Casuarina equisetifolia forest in coastal sandy soil

Fractal model was used to study soil structure of ten regeneration patterns of Casuarina equisetifolia protection forest in coastal sandy soils to determine the relation between fractal dimension and soil fertility. The results indicate that the higher the finer sand content, the more fractal dimensions exist in the soil structure, and, the better the fertility and water storage ability of the soil. There are obvious regression relations between fractal dimension, soil structure and finer sand content of the soil as well as other soil physical and chemical properties. Fractal dimension of soil structure in multirow mixing pattern, in which C. equisetifolia, Acacia crassicarpa, Pinus elliottii and Eucalyptus 12 ABL are orderly located, is highest. The pattern most obviously improves soil fertility. The application of fractal dimension on sandy soil fertility provides a new way for regeneration pattern selection of C.equisetifolia protection forest.