Abstract: Water hyacinth(Eichhornia crassipes) is a notorious invasive species in the water bodies of Shanghai,the biggest city of China.The study in Shanghai and its administrative districts from July 2002 to December 2003 showed that the distribution of water hyacinth population was disproportional,the most in Qingpu,Jinshan,Songjiang and Jiading,medium in Fengxian,Nanhui and Baoshan,and least in Pudong,Chongming and urban districts.The population dynamics of E.crassipes was significantly correlated with water quality and with other hydrophytes lived together,and thus,the effective control methods should be integrative,i.e.,under the coordination with Jiangsu and Zhejiang Provinces,control other hydrophytes,decrease river pollutants,and salvage the clones of water hyacinth from December to next June.

Key words: Tianshan Mountains, grassland, reactive nitrogen, ammonia, deposition.