洞庭湖区近50年土地利用/覆盖的变化研究

LAND USE/COVER CHANGES IN DONGTING LAKE AREA BETWEEN 1955～1998

利用1978、1989、1998年的Landsat卫星遥感影像资料及20世纪50年代航测的地形图,研究了洞庭湖区近50年土地利用/覆盖及其景观结构的变化。土地利用/覆盖类型分为水体、湿地、农田、林地和建成区五类,各时期遥感影像的总体分类精度都在80%以上。运用ArcInfo和ArcViewGIS软件,将不同时期的土地利用/覆盖格局在空间上清晰地显示出来;通过叠加4个不同时期的影像分类图,计算出各种土地利用/覆盖类型转变为其他土地利用/覆盖类型的比例。洞庭湖区50年来水体面积不断减少,减少量为1460km2,其中1955年到1978年水面面积缩小了970.57km2,分别为1978年到1989年和1989年到1998年缩小面积的2.23倍和18.05倍;湿地面积逐渐增加,1998年湿地面积分别为1955、1978和1989年的1.46、1.41和1.09倍;农田的面积百分比从1955年的54.70%增加到1978年62.15%,又逐渐降低到1989年的51.88%和1998年的48.17%;林地的面积1978年比1955年减少了17%,1989年比1978年增加了57%,1998年比1989年增加了11%;建成区的变化表明近50年来湖区城市化的进程。洞庭湖区土地利用/覆盖及其景观结构的变化是社会经济和自然因素综合作用的结果。

Land use/cover changes and their landscape structures in Dongting Lake area during 1955～1998 were identified by using Landsat MSS of 1978, TM satellite imagery of 1989 and 1998, along with digitizing topographical maps of research area surveyed in the 1950s. The land coverage was grouped into five types: water body, wetland, cropland, forest and settlement, and overall classification accuracy on Landsat satellite imagery for periods of 1978, 1989 and 1998 were all above 80%. By applying Geographical Information System (GIS), spatial patterns of land use/cover in different stages were explicitly explored. By overlaying four classification maps, the percentage of each type of land use/cover converted into other categories was computed. The area of water body consistently decreased by 1 460 km\+2 over last fifty years, of which 970.57 km\+2 was shrinked between 1955～1978, which was respectively 2.23 times and 18.05 times of that during 1978～1989 and 1989～1998. While the area of wetland increased gradually, its area in 1998 was respectively 1.46 times, 1.41times and 1.09 times of that in 1955, 1978 and 1989. Cropland area percentage increased from 54.70% in 1955 to 62.15% in 1978 then decreased to 51.88% in 1989, and to 48.17% in 1998. The area of forest decreased by 17% between 1955～1978, compared with a noticeable increase by 57% during 1978～1989, and a slight increase by 11% during 1989～1998. Changes of settlement showed an urbanization process in recent fifty years. All these changes were driven by the complex interactions of physiographic and socioeconomic factors.