Abstract: In order to investigate the plant community diversity status and its interaction with water quality in a riverine wetland, a two-year study was carried out in five different bayous along the Yangtze riverine wetland in Changshu, Jiangsu, using sampling method to survey the plant communities species composition and diversity status. The results showed: there were five major kinds of plant communities in the wetland, including Form. Phragmites australis, Form. Scirpus validus, Form. Scirpus planiculmis, Form. Sagittaria trifolia and Form. Vicia sepium, the community structures of which were simple. The α diversity indices significantly differed from each other in five observing areas. The Changhuhe area had the highest α diversity indices, while the indices in Baimaotang area were the lowest. Shannon-Wiener index and PIE index of 2010 in all observing areas were higher than those of 2009, except the Baimaotang area. While the Pielou evenness index of 2010 in all observing areas were higher than those of 2009, except the Wangyuhe area. The three α diversity indices increased with the increase of NH3-N, CODMn, BOD5, TN and TP pollutants in the wetland water, while had no significant correlation with pH．

Key words: wetland plant community, diversity index, Yangtze River estuary, water quality, correlation analysis