Study On Wetland Change And Its Drive Factor In Ejina Based On Modern Spatial Information Technology

Wetland is a transitional ecological system between land and water, widely scattering all the world, which is one of ecological landscape of most richly biological diversity and most important survival environment in the natural world. Wetland is a special natural resource and ecological environment, so it can regulate runoff, groundwater, protect biological diversity, prevent becoming desert. Just because of it's special status ,wetland has attracted interest among researchers around the world , but in china , the studies of wetland is only beginning , the systematic studies of wet land in oasis region are less. So in our country the studies are not enough. Ejina oasis is drought region in inland, and is natural ecological barrier of northwest and north region. The waters of upper reaches in ejina oasis region has gradually decreased through the interaction of natural and artificial drive factor, and the area of oasis has sharply decreased from 320 thousands square kilometer in early 1950's to 6.9 thousands square kilometer in 1980's. Now, it remains 3.328thousand square kilometer. About 0.37million waters, wetland became desertification. The role of it's ecological barrier increasingly weakened. It became one of important sand source in our country. So, it has influenced ecological environment in the north of our country, affect national defense scientific research, stability of the frontier, and implement of massive western development program.This paper take ejina oasis for example, using remote sensing dates, GIS (geography information system) technology combined with qualitative and quantitative method firstly to analysis the situation and change of wetland in ejina in last 15 years, then, according to document dates and statistic dates the drive factor was debated. Finally, it put forwards the problem of environmental weakness resulted from the changes of wetland, the result of studies show:(1) Natural wetland is a main types in the research area, in which, interior saline-alkali wet land, marshland-wetland, lake beach take up lager proportion than artificial wetland. (2) Wetland has sharply shrunk for recent 14 years. It's dynamic change show that transform of types are not apparent, and mainly change to sand, grass, saline-alkali soil, etc. (3) Water discharge in upper reaches gradually declined. This is main reason about the area of wetland decreasing and wetland sanding. The Induced factor of the change come from the change of environment, increase of population, development of society and economy, the change of human behavior's intensity and way, the influence of culture, politics, strategy, etc. To some extent, which fasten the change. (4) Because of various of drive factor, wetland significantly changed and lead to a series of ecological environmental problem such as decrease of function itself and other environmental problems, for instance, decrease of runoff, reduce of groundwater's level, worsening of water's quality, decline of forest, biological diversity, broadening of desert, aggravation of wind and desert's harm, etc.