干旱区典型农业绿洲的景观变化与原因分析

Landscape changes of typical agricultural oasis in arid regions and its driving factors

应用 GIS和 RS技术 ,运用 FRAGSTATS格局分析软件 ,从景观破碎度、分维数和分离度等综合分析了河西走廊武威绿洲的景观格局十多年的变化情况。并通过建立景观类型转移矩阵和转换图 ,详细描述了各类型间的转化情况。武威绿洲各项格局指数的变化都可表明人类影响不断加大 ,发生变化最大的在绿洲边缘地带。从人类活动和水资源的变化找到绿洲景观变化的驱动因子 ,并提出了可持续利用的对策。

Wuwei oasis is a typical agricultural oasis in Gansu province, there are 10×10~4 hm^2 farmland and 1 Million population. The oasis development keeps stability in long history. With human disturbance activities become more and more obvious in recently 20 years, Landscape spatial pattern change rapidly. Based on GIS and Remote Sensing, the paper analyzed landscape changes of Wuwei oasis from 1986 to 2000 and its driving force. The irrigated farmland increased 6295 hm^2, mainly changed from bare land and desert, and secondly from grassland and forest by transition matrix. The desert decreased 13530 hm^2. The increasing part of town and rural resident is mainly from farmland. Changes often occurred in the edge of oasis, which reveals the ecological system is unstable. The main results of landscape analysis computed by FRAGSTATS.The increasing of fragment index of farmland is a result of many small patches increasing on the edge of oasis. The decreasing of isolation index and increasing of fragment index of desert is due to some of large patches divided into many small patches. The isolation index increasing and mean fractal dimension index decreasing show that the arbor forest was destroyed and lost its natural patch shape. The spatial distribution type of patches was judged by nearest index in settlement geography. Low-coverage grassland, desert, salt land, bare land and shrubbery belong to aggregate distribution type which often occurs with some certain resource. Low-coverage grassland often occurs in arid area such as the edge of desert; salt land occurs in some low-lying area. Farmland increasing is a result of increasing population. Meanwhile, some farmland occur desertification because runoff reduced, rate of ditch utility rose and exploitation of groundwater increased.