基于空间分带的崇明东滩水鸟适宜生境的时空动态分析

本文采用1990—2008年期间6期Landsat TM遥感影像的解译结果，基于ArcGIS空间分带方法并构建生境有利度指数，分析了崇明东滩水鸟适宜生境的时空动态。结果表明：（1）近20 a来，主要受自然湿地的围垦、堤内土地利用方式变化和堤外互花米草(Spartina alterniflora)入侵的影响，崇明东滩海三棱藨草(Scirpus mariqueter)群落（SMC）和养殖塘（AP）的数量特征变化较大，水鸟适宜生境的数量和结构经历了由自然生境到人工生境再到自然生境占支配地位的变化；（2）1990—2008年期间，SMC和AP生境有利度指数值的最高年份分别是1990和2003年，指数值的最低年份分别是2000和2008年；（3）1990s年代的大规模围垦以及互花米草的入侵，致使SMC生境的面积锐减，其主要分布范围从1990年的堤外1000—5000 m变为堤外0—3000 m处，导致SMC生境状况恶化；（4）大堤内AP生境是崇明东滩的重要水鸟生境类型，受堤内土地利用方式改变的影响，该生境2008年的生境有利度指数很低。崇明东滩鸟类生境的管理和保护不仅应重视自然湿地中的光滩与浅水区域，同时更应侧重于海三棱藨草群落和堤内养殖塘的管理和保护，其重点管理和保护范围可界定在堤外3000 m到堤内2000 m之间。崇明东滩水鸟生境的管理应实现多目标管理，维持各类适宜生境的足够面积和合理的空间布局，并在时间尺度上保持相对稳定，才能有效地保护各类水鸟种群及其生物多样性。

An analysis on spatio-temporal dynamics of suitable habitats for waterbirds based on spatial zonation at Chongming Dongtan, Shanghai

Chongming Dongtan, an important habitat for migratory birds in East Asia, is located on Chongming Island in the Yangtze Estuary. The Dongtan wetlands were listed in the Chinese Protected Wetlands in 1992, and were designated as internationally important under the Ramsar Wetlands Convention in 2001 and as a national nature reserve in 2005. By their very nature and location, the estuarine and coastal habitats are dynamic and their biodiversity conservation and management relies on up-to-date spatial information. Based on the interpretation results of six Landsat TM images of the years 1990-2008 and a method of spatial zonation on ArcGIS, this paper developed an index of habitat advantage degree (ADIH), in combination with the main impact factors such as habitat area, habitat spatial distribution and human disturbance intensity, and analyzed spatio-temporal dynamics of habitat suitability for waterbirds at Chongming Dongtan for the period of 1990-2008. The results showed that : (1) Over the past two decades, under the impacts of wetland reclamation, changes in the ways of land use and invasion of an exotic plant Spartina alterniflora, the quantitative characteristics of Scirpus mariqueter community (SMC) and aquaculture ponds (AP) at Chongming Dongtan changed greatly. The amount and structure of suitable habitats for waterbirds underwent changes from natural dominance to artificial dominance; (2) During the period of 2000-2008, the highest values of ADIH for SMC and AP occurred in the years of 1990 and 2003, while the lowest values in the years of 2000 and 2008, respectively; (3) The large-scale reclamation of wetlands during 1990s had led to the decrease in SMC area and its main distribution range changed from 1000-5000m outside dike in the year 1990 to present 0-3000m outside dike, leading to deterioration of SMC habitat during the period of 1990-2000. In spite of slight improvement in habitat status after 2000, the large-scale invasion and replacement of Spartina alterniflora in the range of 1000-2000m, together with intense human disturbance, the values of ADIH for SMC remained lower during the period of 2000-2008; (4) AP habitat inside the reclamation dike was an important habitat type for waterbirds at Chongming Dongtan. This type of habitat was in a relatively favorable status during the period of years 2003-2005, while degraded duo to the changes in the ways of land use inside the dike and the values of ADIH for AP in the year 2008 was low. The conservation and management of suitable habitat for waterbirds at Chongming Dongtan should focus not only on the region of mudflats and shallow waters in the natural wetlands, but also pay more attention to the region of Scirpus mariqueter community and aquaculture ponds. The key range for conservation and management would be between 3000m outside the dike and 2000m inside the dike. To effectively conserve waterbird populations and biodiversity at Chongming Dongtan, the waterbird habitat management should implement a multi-objective management, maintain a sufficient area and rational spatial pattern of each suitable habitat for waterbirds, and keep stable in temporal scale. This study indicated the potential of this approach for objective and effective evaluation of the species habitat suitability in a dynamic estuarine and coastal area. The implications of the results as a tool for biodiversity conservation, wetland conservation and management are discussed.