中文摘要：

目的：探讨三峡工程蓄水对鄱阳湖区洲滩植被和钉螺的影响及变化规律。方法对鄱阳湖4块典型洲滩高、中、低3个高程地带，以分层机械抽样、定点导航方法进行时间跨度为8年的植被演替观察，并同步调查钉螺分布情况，分析不同高程的植被优势群丛及钉螺分布变化规律。结果4块洲滩在三峡工程蓄水后的2004年和2008年，平均水淹日数较蓄水前的2002年分别减少了74.8 d和65.8 d。2005年以来，鄱阳湖区洲滩植被空间分布格局发生了变化，植被优势种群及分布发生了演替，多种植被有向湖心推进的趋势。在湖区14 m高程以上的洲滩，湿生植被退化，并逐步为中生性草甸替代；在14 m以下高程洲滩，苔草、虉草大面积显现，向湖心缓慢扩张，湿生植被蓼子草面积扩大且下移。苔草群丛下检获的钉螺相对较多，但钉螺密度呈逐年下降趋势，钉螺孳生地呈现向高程较低的地带迁移的趋势。结论三峡工程蓄水对鄱阳湖的水文情势产生明显影响，湖区洲滩植被出现了新的演替，中生性草甸植被与钉螺呈现向洲滩低高程区域缓慢迁移的趋势。

英文摘要：

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 O. hu-pensis 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 The hygrophilous vegetation has degenerated and gradu-ally been replaced by mesophily meadow in the marshland area above 14 m elevation. Carex,Phalaris arundinacea and Polygo-num 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 habi-tats towards low terrain was observed. Conclusions The impoundment of Three Gorges Project has had a significant impact on hy-drological 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.