上海地区外来种互花米草的分布现状

遥感技术(RS)现已广泛应用于海岸带资源调查、资源与环境动态监测以及滩涂植被定量分析。作者应用2003年8月2日Landsat5-TM多光谱遥感影像,利用遥感处理软件ERDASImagine8.6TM,经几何校正和分幅裁剪等图像预处理后,采用监督分类和目视解译相结合的方法对上海地区互花米草(Spartinaalterniflora)扩散现状进行解译分析,并结合全球定位系统(GPS)样点定位,对解译结果进行全面的野外验证和修正。同时,应用地理信息系统(GIS)对解译结果进行数据合成,统计出互花米草分布区域及面积等数据。实际调查与分析统计显示:上海地区互花米草群落总面积(2003年)为4,553.37hm2,占滩涂植被总面积的22.1%。除了崇明西滩和横沙岛外,互花米草群落已广泛分布于长江河口地区,其中南汇边滩最多,为2,069.01hm2,其次是崇明东滩和九段沙,分别为910.17hm2和769.05hm2。人工引种是互花米草种群在上海地区滩涂成功扩散的重要原因。大尺度的上海滩涂互花米草群落空间分布现状及其数量调查为外来物种的宏观定量调查提供了有效的手段,也为上海市滩涂资源生物多样性保护和可持续开发利用提供了科学依据。

Distribution of an exotic plant Spartina alterniflora in Shanghai

Remote sensing, in conjunction with Geographical Information Systems (GIS) and Global Posi-tioning Systems (GPS), has been used successfully in many studies on coastal resources, dynamical monitor-ing of the environment, and quantifying tidal flat vegetation. We investigated the potential of using multis-pectral satellite remote sensing to map and quantify an exotic plant, Spartina alterniflora, on tidal flats in Shanghai. A Landsat5-Thematic Mapper image, dated 2nd August 2003, was geometrically corrected using ERDAS Imagine 8.6, and a sub-sample of the study area was then extracted. The sub-image was then ana-lyzed using a Tassel Cap transformation (K-T) and the Normalized Difference Vegetation Index (NDVI) was used to identify different types of salt marsh vegetation. Based on these results, a series of classes were iden-tified and a supervised classification was carried out using the Maximum Likelihood Classifier in ERDAS Imagine. The results of the classification were then checked using an in situ field survey of selected areas. The classification had an overall accuracy of 80%. The classified image was then integrated with other data in a GIS to analyze the spatial distribution of the S. alterniflora communities in Shanghai. The results showed that the total area of the S. alterniflora community in Shanghai was 4,553.37 hm2 in 2003, which accounted for 22.1% of the total vegetation on tidal flats. Excepting Chongming Xitan and Hengsha Island, the S. al-terniflora community was distributed extensively on the tidal flats in the Changjiang Estuary. Nanhui Bian-tan accounted for 2,069.01 hm2; Chongming Dongtan, 910.17 hm2 and Jiuduansha, 769.05 hm2. The distribu-tion pattern of S. alterniflora showed that anthropogenic transplantation and the rapid proliferation of clones could be the main cause for successful expansion of this exotic. The results of this research indicate the po-tential of this approach for providing timely data for quantitative inventory of invasive plants over large ar-eas, and a scientific basis for biodiversity protection and sustainable utilization of tidal flats resources.