Abstract: The analysis with fractal theory on the fractal characteristics and related affecting factors of particle size distribution in mangrove soils in Dongzhai Harbor of Hainan showed that the fractal dimension of mangrove soils ranged from 2.302-2.575. There was a significant positive linear relationship between the fractal dimension and the contents of soil clay, salts, organic matter and total nitrogen. The fractal dimension was lower in outside beach than in middle and inner beach, and changed with soil texture, being in the order of sandy loam<light loam<medium loam<heavy loam. From land to sea, the fractal dimension decreased gradually. The main factors affecting the fractal dimension were community type, soil texture, beach position, soil salinity, and organic matter and total nitrogen contents.

Key words: Megranate field, Aphis gossypii, Natural enemies