Abstract: Based on the investigations of root parameters and soil physical properties, the improving effects of soil physical properties by the roots in different depth of soil in Chinese pine plantation and their interaction have beenfirst quantitatively demonstrated in this paper. The results show that theeffects of roots to improve soil physical properties are consistent with thedistributing rule of effective root density (fibrous less than 1mm in diameter) in soil profile, which follows the decreasing law of exponential function. The vertical changes of roots in improving the soil physical propertiescan be divided into 4 obvious areas of soil layers, and the effects of rootson improving soil physical properties corelate more closely with effective rootdensity than with root weight, and which show a learn positive relation ata significant level (p<0.001). Therefore, an effective model of improvingsoil physical properties by the roots of Chinese pine plantation is established.The value of the model is to plain the mechanism of stabilizing soil structure by roots and to evaluate the effectiveness of roots for improving the physical properties of soil.

Key words: Roots of Chinese pine plantation, Improving effects of soil physical properties, Effective model, The loess plateau