The south edge of Mu Us sandy land belongs to the Erdos Plateau and the Loess Plateau transition zone. At the same time the area is the typical farming-pastoral region and the ecological environment is extremely fragile. Vegetation as the primary producers of ecological system not only provides the system required organic substances and biological chemical energy,but also can improve and adjust the environment in the ecological systems. Vegetation change is the most intuitive performance of desertification development or reversal. It also is the sensitive index of the climate and human factors impacting on the ecological environment. Vegetation pattern information of Dingbian County can be served as vegetation protection,restoration and reconstruction.
Remote-sensing data includes the TM or ETM+ images of 1991,1999 and 2007 in this study. Vegetation coverage information extracted from 1991 to 207 by using RS and GIS is divided into two areas according to different landform. Landscape indexes of two zones calculated are used to analysis vegetation pattern changes. The results show the following conclusions. (1)The turning point of vegetation coverage is 1991 in two zones during sixteen years. Vegetation coverage conditions continue to worsen in the first stage while both improve in the second stage. The lower and low level accounted for the absolute superiority. Meanwhile, both levels in two zones is increasing from 1991 to 1999. It has risen from 55% to 70% in sandy areas and from 70% to 80% in hilly region. The high level ratio below 5% is continuing to decline. In two zones dominance level are changed to low and moderate level in 2007. They are 55% in sandy area, 70% in hilly region. The high level has risen with different degree. (2)After 1999 the vegetation landscape pattern changes reversed. Landscape pattern change trend is the same but the degree is different. Landscape diversity and landscape evenness firstly decreases and then increases. Types of alternating distribution firstly wake and then enhances. The landscape fragmentation index of sandy areas firstly increases and then decreases, while continuously rising in hilly region. On the whole sandy areas landscape fragment degree is small and diversity is high. Vegetation alternating distribution is obvious and evenness index is high. The characteristic of landscape pattern is on the contrary in hilly region. The interference from outside is strong in sandy area,but weak in hilly region. (3)Vegetation pattern is the multi-core model during evolvement process. Meanwhile, the core size, shape and type change in different degrees. Sandy area core mostly is non-vegetation patches while hilly area high vegetation coverage level patches. Vegetation around the core distribution shows a gradient.