Abstract: For exploring the relationship between population characteristics of Phragmites australis in different communities and the distance between them and river bank, spatial distribution pattern of P.australis and spatial association between P. australis and Artemisia desertorum, Haloxylon ammodendron, Astragalus variabilis, Inula salsoloides were analyzed using point pattern analysis. In a 5 m series spatial scale, the P.australis population as dominant species was characterized by random distribution near the river bank, and by clumped distribution in small scale while random distribution in large scale far from the river bank. However, P.australisas companion species was characterized by clumped distribution and the clumping degree is stronger with short distance to river bank. There is a positive association between P.australis and A.desertorum and the association degree is stronger with far from river bank. There is a negative association between P.australis and A.variabilis at 4.1-5 m, and positive association between P.australis and I.salsoloides at 1.5-4.6 m. The results have an important significant on protecting and repairing riparian vegetation of Shiyanghe River.

Key words: Shiyanghe River, Phragmites australis, spatial distribution pattern, spatial association