The analysis on the oasis landscape dynamics

Landscape changes or landscape dynamic is one of the central research topics in landscape ecology. Oasis is one of specific landscapes that exist with desert in the arid zone. In China, oases are mainly distributed in the deserts and gobies between Helanshan\|Wuqiaoling Mountains and the west frontier of the country. Although it takes up only 4%～5% of the total area of the region, over 90% of the population and over 95% social wealthy are concentrated within it. The oasis is not only the essence of the regional economic and political activities but also artificial disturbance factor at regional scale in arid zone. The object of this study is to investigate the landscape dynamics and its driving forces of No.150 Regiment of Mosouwan Cultivated Farmland in Shihezi District, Xinjiang Uygur Autonomous Region. Land\|use maps with the scale of 1:25 000 in 1982 and 1996 were used in the study. Furthermore, eight patch types were classified into 1) cropland, 2) vegetable land, 3) orchard, 4) forested land, 5) residential site, 6) abandoned cultivated land, 7) wasted grassland, and 8) sand land. According to the influential degree of human activities, they also were amalgamated as three patch kinds artificial (1)～(5), natural (7)～(8), and semi\|natural patch (6). Transition probability matrix was adopted to complete the trend analysis of landscape patch dynamic. To investigate the spatial variations of landscape dynamics, the regiment was divided into 3 sub\|regions in terms of similarity of natural condition and agricultural development direction as well integrity of administrative unit. They are southern grain\|cotton gray desert soil region, central grain\|cotton\|residual bog soil region, and northern grain\|cotton\|sheep gray desert soil region. The following results with respect to landscape changes have been drawn:1) landscape matrix was changed from cultivated land to wasted grassland, 2) of the eight patch types the areas of wasted grassland, forested land, and residential site had been increased and others decreased among which sand land, cultivated land, and abandoned cultivated land took the dramatic decline, 3) the transition probabilities of vegetable land, abandoned cultivated land, orchard and sand land patches were over 40%, while wasted grassland and cultivated land about 20% in the processes of patch transition. There exist the differentiation of such landscape changes for the different landscape sub\|regions of research area. Self\|stability of artificial oasis could be summarized from the phenomena and driving forces of above\|mentioned landscape changes. The stability was indicated by the decrease of sand land which was the most sever threat to the economic activities and daily life of the oasis, and correspondingly the dramatic increase of wasted grassland where was the most valuable elements to the environment improvement of the oasis. Its internal mechanisms lied in the formation of ground water raised zone due to the objective oasis management practices. The biggest threat of survival and development of the oasis comes from the natural elements and influences of the other oasis.