滇池流域1974年至2008年土地利用的分形动态

Fractal Dimension Dynamics and Land Use in the Lake Dianchi Watershed from 1974 to 2008

在遥感与GIS技术的支持下,通过滇池流域从1974年-2008年近35年间时间序列上的土地利用分类数据监测流域整体景观与分地类的分形维动态,试图从分形视角为滇池流域土地利用政策的制定提供理论依据,协调高原湖滨城市发展和湖泊生态系统保护。结果表明:①流域内各地类的形态呈现分形维特征,分形维数从植被覆盖类型(荒草地、农用地和林地)到裸地与建成区、水体依次减小;②近35年来滇池流域景观的整体分形维数持续上升,逐渐接近于临界值1.50,其结构稳定度持续下降,趋于随机运动的不稳定状态;③农用地与建成区的分形维数均呈"逐渐提高后稍有降低"的变化趋势,荒草地分形维数的变化趋势则相反,林地的分形维数总体呈上升趋势,裸地与水体的分形维数总体呈下降趋势。城市建成区快速扩展过程中农用地的占用与补给所导致的一系列土地利用变化是滇池流域土地利用分形维数与结构稳定度变化的主要驱动因素。滇池流域在制定区域土地开发和利用政策时,应以控制流域整体分形维数的提高、保证流域景观整体的结构稳定度为基本原则,进行建设用地的空间蔓延管制,将发展的重心转移到旧城的改造与更新,对零星分布于林地与荒草地过渡地带的农用地贯彻退耕还林还草政策,将耕作条件良好且邻近分布的农用地整治连片。

Here, we use remote sensing and GIS techniques to monitor the fractal dimension dynamics of land use patterns in the Lake Dianchi watershed from 1974 to 2008. Our aim is to provide a theoretical basis for land use policy across the Dianchi watershed and coordinate urban development and lake ecosystem protection in this plateau lakeside city. We found that the morphology of each land use within the Dianchi watershed takes on fractal dimension characteristics. Ranked from high to low, the fractal dimension can be ordered by vegetation class （including wild grassland, agricultural land and forest）, bare land and built-up areas, and water. The fractal dimension of the whole watershed landscape has been gradually rising, is approaching the critical value of 1.50, and structural stability continues to decline towards an unstable state. Both the fractal dimension of agricultural land and built-up areas gradually increased then slightly decreased, opposite to that for wild grassland. The fractal dimension of forest increased, and the fractal dimension of bare land and water decreased. Land use changes resulting from the occupation and supply of agricultural land during the process of urban sprawl is the main driving force behind fractal dimension dynamics and structural stability in the Dianchi watershed. Therefore, regional land renovation policy should aim to control increases in fractal dimension. The spread of urban built-up areas should also be controlled, and more attention should be paid to the renewal of old town areas. Agricultural land distributed in patches across the transition zone between forest and wild grassland should be returned to forest and grass.