Abstract: Based on classification of the wetland vegetation coverage in the Xixi Wetland Park, relationship between plant communities and water quality were studied. Results show that the park has 16 species of wetland plants, belonging to 16 genera, 13 families, and is low in species richness. When vegetation coverage of the wetland is maintained at a low (1% - 20%) or moderate level (>40% - 60%), its water quality was kept at a relatively good level. It seems that a higher vegetation coverage is not at all conducive to maintenance of a good water quality. Based on analysis of relationships of common plant communities (ca 40% in coverage) with water quality, the plant communities can be sorted into 3 types, i.e. Type I : Iris tectorum + Alternanthera philoxeroides and Arundo donax + A. philoxeroides, and Thalia dealbata + A. philoxeroides, where chemical indices of the water were all very high, indicating that the water environment is very poor in quality; Type II : A. philoxeroides, Zizania latifolia + A. philoxeroides, and Thalia dealbata + A. philoxeroides, where the water environment is at a moderate level in quality; and Type III : Phragmites australis + A. philoxeroides, where the water environment is relatively good. Therefore, reestablishment of vegetation of native plants, like P. australis and maintenance of a proper vegetation coverage, low or moderate is recommended to keep the water in good quality in wetland park.

Key words: Xixi Wetland, wetland plant community, coverage, water environment