崇明东滩自然保护区盐沼植被的时空动态

The spatio-temporal dynamics of salt marsh vegetation for Chongming Dongtan National Nature Reserve,Shanghai

盐沼植被是滩涂湿地的重要组成部分，其动态变化直接影响着湿地的生态服务功能和价值。通过对1998—2005年间4景不同时相的LandsatTM遥感影像的解译分析，结合历史资料数据和近年来的现场调查，分析了崇明东滩鸟类自然保护区自建立以来，盐沼植被的时空演替动态过程。结果显示，随着滩涂的淤涨，东滩盐沼植被的面积从1998年的2478．32hm^2增加到2005年的4687，74hm^2，而互花米草（Spartirta alterniflDm）自人为引入至2005年，其面积已增加到1283．4hm^2，其增加速率显著高于土著种芦苇（Phragmitesaustralis）和海三棱藤草（Scirpus mariqueter），并且已在东滩保护区相当区域内形成单优势种群落。受1998年和2001年两次高滩围垦和互花米草入侵影响，崇明东滩的芦苇群落面积大大减少，虽随着滩涂的淤涨，芦苇群落的面积逐年有所增加，但增加的速度缓慢。互花米草有着更广的生态幅和竞争优势，是滩涂中扩散最快的植被，而淤涨型滩涂为其提供了可扩张的空生态位，如不加以控制和治理，其快速扩散将会对崇明东滩保护区的生态系统造成更大的威胁和影响。

Salt marsh vegetation is one of the most important components of coastal wetlands, and its evolution and dynamics have direct influences on the ecosystem service and value of wetlands. Based on analyses and interpretation of four Landsat TM remotely sensed images, integrated with historical data and field surveys, this study investigated the spatio- temporal dynamics of salt marshes at Chongming Dongtan National Nature Reserve for the period 1998 --2005. The results showed that the total area of salt marsh increased from 2478.32 hm^2 in 1998 to 4687.74 hm^2 in 2005 along with the expansion and accretion of tidal flats in the natural reserve. Results also indicated that Spartina alterniflora expanded at a much faster rate than the native species Scirpus mariqueter and Phragmites australis. In less than 10 years, the area of S. alterniflora increased from the initial introduction to 1283.4 hm^2 by 2005 and it had formed a large area of mono-dominant community. During this same period, the area of the P. australis community influences of wetland reclamations in 1998 and 2001, and the invasion of S. decreased significantly, mainly due to the alterniflora. S. alterniflora expanded very quickly in the nature reserve due to its stronger competitive capacity and wider ecological niche, and the rapid accretion of intertidal flats which provided more suitable habitat. It can be concluded that the range expansion of exotic S. alterniflora poses a potential threat to local ecosystems, and measures should be taken for the management and control of this invasive species at the nature reserve