额济纳天然绿洲景观变化及其生态环境效应

Landscape change and its eco-environmental effects in Ejin natural oasis

基于研究区 1987年LandsatTM和 2001年LandsatETM+遥感影像资料, 综合运用遥感与GIS技术手段, 结合景观格局分析软件APACK, 就近 15年来额济纳天然绿洲景观格局变化进行了分析, 并进一步探讨了由此所引起的生态环境效应。研究结果表明: 1) 天然绿洲面积与水域面积急剧缩减, 绿洲荒漠化程度加剧; 2) 绿洲景观与荒漠景观过渡地带为各景观生态类型相互转化最为剧烈的区域; 3) 景观多样性与景观异质性程度减小, 景观稳定性降低; 4)景观变化所引起的生态环境效应包括地下水矿化度升高、水质下降, 植被退化与物种多样性降低, 沙尘暴危害加剧以及生态难民数量增加等。

The Ejin natural oasis landscape lies in the lower reaches of the Heihe river basin in the arid inland regions of northwestern China. With decreasing water resources from the upper reaches of the Heihe river basin, many serious ecological and environmental issues in the Ejin natural oasis have become more and more pressing in recent years. Using remote sensing techniques, GIS, and landscape pattern analysis software APACK, the landscape patterns changing characteristics, and the eco-environmental effects for Ejin natural oasis landscape are studied based on Landsat Thematic Mapper data in 1987 and Landsat Enhanced Thematic Mapper Plus data in 2001. The main results show that: 1) During the past 15 years, both the water area and main oasis area sharply decreased. The degree of oasis desertification process, at present, is more serious than before. 2) The most intense conversion among different landscape types was occurring in the transitional zone between oasis landscapes and desert landscapes. 3) As a result of the change of Ejin natural oasis landscape, the landscape patches shape complexity and its heterogeneity were obviously reduced. Moreover, the landscape texture became more and more coarser, the landscape diversity was decreasing and the landscape stability turned into unsteady. 4) Sharply decreasing surface water from the upper reaches of Heihe river basin is the vital factor for Ejin natural oasis landscape degradation in the past 15 years. The eco-environmental effects for Ejin natural oasis landscape induced by landscape change include the acceleration of groundwater mineralization degree, the degeneration of groundwater quality, the degradation of natural oasis vegetation, the decrease of species diversity, the increasing threats of sandstorms, the increasing quantity of ecological refugee and so on. In conclusion, the landscape condition of Ejin natural oasis landscape, today, is much worse than in the past years, with bad unsustainable developing trend.