AQUATIC VEGETATION OF POYANG LAKE

Poyang Lake of Jiangxi Province is the biggest freshwater lake in China and one of the numerous shallow lakes which are characteristic of the middle and lower Yangtze valley. It covers an area of about 2800 square kilometres. And its area of drainage basin is 162,000 square kilometres. Aquatic vegetation of Poyang Lake is very rich in number of species. A survey yields the sum total of 98 species, belonging to 71 genera and 37 families.The vegetation distributes in about 2262 square kilometres and accounts for 80.8% of the lake's area. The distribution of the plants exhibits irregular zonation and it may be grouped into 4 plant zones. According to the assemblage of the various species, aquatic vegetation of Poyang Lake may be grouped into 9 associations.Because Poyang Lake suffered from siltation from the five rivers and large-scale reclamation, its water area has become smaller and smaller and its area of vegetation has been also shrinking year after year. Some valuable plants, such as Phragmites communis, Nelumbo nucifera, Euryale ferox, Trapa spp, etc., have been reducing. At the same time, the zonal distribution of vegetation is getting more and more incomplete because the original shape of the lakebasin and the level of water have been changed.The seasonal changes of water level in Poyang Lake causes the types of. vegetation to display a strong seasonal alternation between the community of aquatic plants and that of hygrophytes.