| Desertification is one of the eco-geological disasters which distributes widely and has great imperil in China Erjina basin in western Mongolia municipality is one of the regions in China where desertification is the most serious and develops in the fastest speed. Desertification in the region not only restricts the harmonious development between economy and society, threatens the survival of the people, but also blights the stabilization of the society and the solidification of different nations, and even threatens the whole environment in Northern China. Therefore, there has been no time to delay for the prevention and cure of the desertification in Erjina basin. Because the process of desertification is exhibited in morphologic of fragmentation, reduction and disappearance of vegetation patches, the prevention and cure of the desertification must be based on the mechanism of the vegetation patches' evolution. Desertification is modally represented by degradation of vegetation parches. However, its essence is retrogressive succession of plant communities materially, which is controlled by the degradation of plant habitat, especially plant underground habitat. Therefore, it is must be started with the systemically analysis of structure of the plant underground habitat to insight into the mechanism on establishment and evolution of vegetation patches pattern.Based on field investigation and indoor test results of the plant underground habitat structure and vegetation structure in different sub-zones in Erjina Basin, and combining digital graphic data of infrared color photo in 1996 from TM satellite and of remote sensing image in 1999 and 2000 from America Landsat ETM, we found that the structure of plant underground habitat controls the structure of plant community, and further affects the form of vegetation patch. To determine how the structure of plant underground habitat controls the evolution of vegetation patch, we selected the area where vegetation patches pattern changed markedly for more detailed study. In the area, by investigation and analysis of the plant community structure, form and plant underground habitat structure of vegetation patches in different succession phase, we found that evolution of plant underground habitat structure controls the vegetation patch succession, and predicted that wind erosion is the main driver to vegetation patch degradation, and human activities may be the inducement. As to the establishment of new vegetation patch, wind deposition may be its major cause, and relatively ample moisture and slow deposition speed are essential factors. The whole study will be given in detail as follows:(1) Presenting existing study on the mechanism of the evolution of vegetation patch, we expound the different angles and defects of former study, and pose the research flow of the paper.(2) Guided by eco-geological theory, we pointed out that vegetation patch just is the form of plant community, and the evolution of vegetation patch just is the representation of plant community succession. We also deduced that the structure of plant underground habitat affects thedistribution pattern of vegetation patches by controlling the structure of plant community, and the evolution of plant underground habitat affects the evolution of vegetation patches pattern by controlling the succession of plant community.(3) Firstly, we analyzed the general characters of plant underground habitat in Erjina Basin, divided its profile into two layers, and summarized the rules of fluctuation, resources content and their ecological function. Then, considering the difference of plant underground habitat structure in different zones, its significance to the structure of plant community and the establishment of vegetation patches pattern, we divided Erjina Basin into five sub-zones, and analyzed the structure of plant underground habitat and its controlling function to vegetation and vegetation patches pattern of different sub-zones in detail. The results showed: 〢t different layers of plant underg...
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