[Studies on changes of vegetation and Oncomelania hupensis snails in Poyang Lake after impoundment of Three Gorges Project].

ABSTRACT

OBJECTIVE: To explore the impact and change regularity of Oncomelania hupensis snails and vegetation in the marshlands of Poyang Lake caused by the impoundment of the Three Gorges Project. METHODS: By using the methods of stratified systematic sampling and pinpoint navigation, the succession of vegetation was observed and the distribution of O. hupensis snails was investigated in a period of 8 years on 4 typical marshlands in Poyang Lake. The regularity of changes in vegetation and 0. hupensis snails was analyzed on the marshlands at high, medium and low elevations, respectively. RESULTS: After the impoundment of Three Gorges Project, the average flooding days of these 4 marshlands in 2004 and in 2008 were reduced of 74.8 and 65.8 days compared with those in 2002, the year just before the impoundment of the project, respectively. The change of spatial distribution pattern and the succession of dominant species of vegetation on the marshlands of Poyang Lake have taken place since 2005, and several vegetations showed a trend of moving toward the center of the lake. The hygrophilous vegetation has degenerated and gradually been replaced by mesophily meadow in the marshland area above 14 m elevation. Carex, Phalaris arundinacea and Polygonum appeared in large area and expanded slowly towards the center of the lake on the marshland below 14 m elevation. O. hupensis snails were mostly found under the Carex association. The tendency of decreasing in density of snails and of migration of snail habitats towards low terrain was observed. CONCLUSIONS: The impoundment of Three Gorges Project has had a significant impact on hydrological regimes, and a new succession of vegetation has taken place in the marshlands of Poyang Lake. O. hupensis snails and the mesophily vegetation show a trend of migrating slowly to the areas of low elevation in the marshlands.