三江平原流域湿地景观破碎化过程研究

Fragmentation process of wetland landscape in watersheds of Sanjiang Plain,China.

以流域为研究单元,利用历史图件和遥感数据资料及GIS技术,系统分析了该区典型流域50年来湿地景观的破碎化过程.结果表明,该区湿地景观破碎化在斑块个体和空间结构两方面变化极大.景观斑块个体变化主要表现为最大斑块、平均斑块面积不断缩小,斑块密度不断增大,斑块形状破碎化指数不断增大,景观内部生境面积破碎化指数不断上升;空间结构变化主要表现为湿地景观由初始基质景观逐渐变为河岸带景观;同时,随着农田面积逐渐扩大,隔离湿地斑体数量不断上升,隔离度不断增大;景观空间分布模式由“大陆岛屿模式”向“卫星型模式”转变,最后变化为“完全隔离型模式”.导致该区湿地景观破碎化的主导因素是大规模的农业开发,反映了人类活动对湿地景观的巨大影响.

The Sanjiang Plain is the largest fresh water wetland distribution area in China and the center of waterfowls breeding and habitat area in Asia,but over the past 50 years,more than 73% of its wetland had lost because of agricultural development,and as a result,the wetland biodiversity declines dramatically,and the remnant wetlands are in a very fragment state.Based on historical maps,remote sensing data and GIS techniques,this paper selected two watersheds to analyze their wetland landscape fragmentation process during 1950～2000.It was indicated that land reclamation resulted in a decrease of 98% wetland corridors in Qixing River,90% in Naoli River,87% in the middle reach of Bielahong River,and 94% in the lower reach of Bielahong River;The amount of isolated wetlands in watershed increased dramatically;The maximum patch areas of wetland decreased by 92.6% in Naoli River watershed and 74.6% in Bielahong River watershed,and the mean wetland patch area in the two watersheds decreased by 99%.Before 1983,the wetland landscape was in an extensive area distribution state (the index of patch density was <0.1),but after 1983,it fragmented dramatically,with the index of patch density larger than 1.5.The shape fragmentation indices of wetland decreased from 1950 to 2000,indicating a very big change in wetland patch shapes in the watersheds.The area fragmentation indices of wetland also increased from 1950 to 2000,especially after 1983,showing that the wetlands were in a serious fragmentation state.The wetland landscape fragmentation changed from a landmass and island model to a satellite model,and finally to a completely isolated model,which indicated the great changes in spatial structure of wetland in the Sanjiang Plain.