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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。
Objective To explore the effects of the Three Gorges Project impoundment on the vegetation and snails in the beach of Poyang Lake. Methods The vegetation succession observation with 8-year time span was carried out by means of stratified mechanical sampling and point-to-point navigation in three high, middle and low elevation areas of four typical beaches of Poyang Lake. The distribution of Oncomelania snails was simultaneously investigated, The dominant species of vegetation and snail distribution changes. Results In 2004 and 2008 after the Three Gorges Project was recharged, the average number of flooding days at 4 Block Beach decreased by 74.8 days and 65.8 days respectively compared with 2002 before the impoundment. Since 2005, the spatial distribution pattern of the beach in Poyang Lake has changed. The dominant species and distribution of vegetation have undergone the succession, and many kinds of vegetation have the tendency to advance toward the lake center. Wetland vegetation degenerated and gradually replaced by Mesozoic meadows at the beach above 14 m above sea level in the lake area. At the height of 14 m, the beaches of Carex, Carex and Ephedra showed large area and slowly expanded toward the lake center. Wet vegetation Polygonum grass area expanded and down. There were relatively more snails seized in the moss grass group, but the density of snail declined year by year. The tendency of snail breeding shifted to lower elevation. Conclusions The Three Gorges Project impoundment has a significant effect on the hydrological situation of Poyang Lake. The vegetation of Chaban Beach in the lake area has a new succession. Mesozoic meadows and snails tend to migrate slowly to the low elevation area of Chau Beach.