九段沙湿地植被群落演替与格局变化趋势

长江口新生湿地九段沙由上沙、中沙和下沙三部分组成。2004年对湿地植被群落的演替与格局变化进行了研究。结果表明,九段沙湿地植被群落由芦苇(Phragmites austra-lis)、互花米草(Spartina alterniflora)、海三棱藨草(Scirpus mariqueter)和藨草(S.triqueter)构成。芦苇和互花米草生长于潮滩高程,海三棱藨草和藨草生长于低潮位。1998—2004年,上沙植被覆盖面积年平均约增长17%,中沙22%,下沙38%~39%,植被群落处于快速增长演替状态,这可能与沙洲发育速度有关。由于在中沙、下沙人为种植过外来物种互花米草,其增长速度最快,覆盖面积占九段沙植被总面积的比例从1998年不足1%上升到2004年的22%,地上部分总生物量的年平均增长率为79.79%,互花米草对藨草-海三棱藨草的竞争压力较大。鉴于互花米草对九段沙的影响尚无定论,本文提出了初步的植被管理措施。

Succession and distribution pattern of vegetation communities on Jiuduansha Wetland

Jiuduansha Wetland is a newly formed intertidal wetland, which consists of three parts, i.e., Shangsha, Zhongsha and Xiasha. The study on the succession and distribution pattern of vegetation communities on this wetland in 2004 showed that the dominant species were Phragmites australis, Spartina alterniflora, Scirpus mariqueter, and Scirpus triqueter. P. australis and S. alterniflora dominated the areas in high tidal flat, while S. mariquete and S. triqueter occupied the inter-middle tidal flat. The area covered by the vegetations was increased by an average of 17%, 22% and 38%-39% per year in Shangsha, Zhongsha and Xiasha, respectively, and the vegetation communities were in accelerated succession, which might be correlated with the development of the wetland. Due to artificial planting, the area covered by S. alterniflora community in Zhongsha and Xiasha increased from less than 1% in 1998 up to 22% of the whole vegetation area in 2004, and the annual increase of the total aboveground biomass of S. alterniflora was 79.79%. The competition pressure of S. alterniflora on S. mariqueter and S. triqueter was heavy. Some elementary measures on the management of the vegetation communities on Jiuduansha wetland were brought forward.