南四湖湿地景观格局变化及原因分析

Research on Wetland Landscape Pattern Change of Nansihu Lake and Its Driving Mechanism

根据南四湖1987年、1991年、1999年和2007年的TM/ETM遥感影像解译分析结果,结合对自然环境及人类活动特征的分析,研究了南四湖湿地的景观格局变化过程与主要影响因素。结果表明,1987年以来南四湖自然湿地面积锐减,其中挺水植物区面积减小了近538km2,而台田—坑塘、人工养殖区等人工湿地以及农业用地面积分别增加了171km2、327km2、86km2。1991年之前,南四湖湿地类型变化主要受湖泊水位等自然环境因素的影响,其中,1988～1990年南四湖几近干涸,使得挺水植物区的分布向湖心区迁移,而近岸地区挺水植物区面积大大减小;这一时期南四湖水位的降低加剧了近岸湖区的围垦,农业用地面积增加。1991年以来,南四湖湿地类型变化主要受人类活动的影响,由于大规模的围垦圈圩,台田—坑塘、人工养殖区的面积大幅增加。

The evolution of wetland landscape patterns of Nansihu Lake during the last 20 years was analyzed according to the TM/ETM remote sensing data, and the driving mechanisms were also discussed in the paper. It was characterized by the decrease of natural wetland （ emergent plant zone） and increase of human wetland （ terrace -pit, aquaculture） and farmland. The area of emergent plant zone decreased about 538 km^2 during 1987 - 2007, and the areas of terrace - pit and aquaculture zones and farmland increased 171 km^2, 327 km^2 and 86 km^2 respectively. The variations of wetland landscape patterns were mainly influenced by the natural factors during 1987 - 1991. Dried up of Nansihu Lake during 1988 - 1990 induced the transfer of emergent plant zone towards the lake center, and accelerated the degradation of emergent plant zone in the lake area near the shore. Simultaneously, the decrease of water lever strengthened human inning, the area of farmland increased 51 km^2. With the water accumulation of Nansihu Lake since 1991, some degenerate emergent plant zone resumed in the near shore area, and the newborn emergent plant zone during 1988 -1991 retrogressed due to the deep water. Nevertheless, the wetland landscape evolution since 1991 was influenced mainly by strengthening human inning. The area of terrace - pit and aquaculture increased rapidly, and the emergent plant zone disappeared nearly till 2007.