Diversity evaluation of riparian vegetation in middle reaches of the East River

Vegetation diversity is one of the important indexes for evaluating the river health.The riparian vegetation in the middle reaches of the East River,Guangdong Province,is investigated and its diversity is analyzed with Shannon-Weiner index method.The riparian vegetation in the subtropical zone develops well and the evolution of vegetation community depends mainly on the flood frequency and flooding elevation.From floodplain to high floodplain,the vegetation community changes from grasses to shrubs and woods.The index of the vegetation diversity increases with the elevation of the land.The vegetation composition in high floodplain is relatively complete and stable,having the highest diversity index,which is even higher than those in temperate zone.The species composition of vegetation community of 4 groups at different elevations are presented and discussed.The vegetation diversity on low elevation floodplain is closely related to water level.Many grass species scatter on these flood plains as the water level is low.Some of the species are flooded and vanished during the flood season.Only some tall grasses survive with high tolerance of submergence.The dominant species belong to Gramineae and Cyperaceae.