The Landscape Neighboring Characteristics Dynamic Evaluation On The Ecological Security Of Ejina Oasis

The Ejina oasis is the important ecological barrier in north-China and northwest in China .In history,the Ejina oasis can exist depending on the water resources in Heihe river. But in the recent years,along with the development of social economic and the increasing of human activities,some ecological matters happened due to the decreasing of water esource from Heihe river such as:groundwater table descending,vegetation coverage declining,function of the oasis degenerating and so on.This paper takes Ejina oasis as research area. Bases on the RS and GIS techniques PCI, use the TM remote sensing image in 1990 and 2003 as resource data, get the parameters such as landscape patch area,perimeter and the neighboring length, amount, area, between different landscape patches with ArcView3.2. Then attain the area transforming matrix and transforming probability matrix of different landscape types throughing the overlapping analysis. Based on the neighboring characteristics, calculate the threatening and ecological security indices of different oasis landscape types. Evaluate the ecological security changing in the latest 13 years. Main results show that:1)the ratio of neighboring length between woodland, farmland, residential area, water area and sandland has minished; Only the ratio of neighboring length between grassland and sandland has augmented.2)the ratio of neighboring length between oasis landscape and Salina increased obviously.3)the transforming matrix shows that: The probability of the change from grassland and woodland to Salina and sandland is high; the probability of the change from Salina and sandland to grassland and woodland is low.4)the threatening of oasis from sandland is declining. The oasis ecological security value calculated from sandland area dropped from 3.11 in 1990 to 1.60 in 2003, this indicates that the area of sandland in oasis is minishing, the threatening degree of oasis from sandland has declined.5)the threatening of oasis from salina is increasing. It indicates that the area of salina in oasis is increasing and the threatening degree of oasis from sandland has increased.