Taking the Minqin county as the research region, the sand soil crust sample in different geomorphic site and plant community
were collected, and its
physical and chemical characteristics were analyzed, in which the soil mechanical composition, soluble salt, soil nutrient elements, organic matter, Ph value, CEC and CaCO 3 content were included. The result showed that whether in the sand dune or the takyr soil, the crust soil mechanical composition is mostly composed by sand (1~0.05mm) and coarse silt particle (0.05～0.01mm). The total salinity is the highest in the takyr soil crust than in any other soil crust, but in the shrub sand dune, the physical soil crust and the Tamarix ramosissima soil crust is highest, and changes of the total cation and anion has the same changing trend. The Nitraria tangutorum soil crust and the takyr soil crust have the higher CEC, and this shows that they have the higher ability in keeping soil fertility. The pH value all is bigger than 7 in different soil crust. The CaCO 3 content in takyr soil is the highest, but in shrub sand dune the situation is that closed Nitraria tangutorum > Nature Nitraria tangutorum community > Tamarix ramosissima community >artificial Haloxylon ammodendron community. In the soil crust nutrient aspects, Nitraria has the highest fertilizer and the artificial Haloxylon ammodendron community has the lowest fertilizer. If we set the top soil of the shifting sand dune and physical soil crust as a background, we can found that the content of Total N, Total P, rapidly available N and rapidly available P is decreased and rapidly available is increased after crust developing. For the integrated view, the result shows that the physical and chemical characteristics of soil crust is better in the takyr soil and Nitraria tangutorum, especially in the closed Nitraria tangutorum. There are three reasons result from above conclusions. The first one is that the takyr soil has the lower microlandform which conduce to rain water and soil matter to congregated in it. The second one is that the takyr soil has a bigger open space than that of shrub sand dune, so it can receive more sand dust matter which is very important for the soil crust development. The third one is the adaptability of plant to environment and its succession process. Under present situation, Nitraria tangutorum is the climax species in this region, and Tamarix ramosissima is in the degenerate stage, so the soil crust developing state under the former plant is better than that of the latter. From our research, we found that the Nitraria tangutorum soil crust develop better after enclosed, in which the organic matter, total N, Total P and rapidly available nutrient were enhanced rapidly. Because the degradation of vegetation and soil is very serious in
desert-oasis region, the artificial close measurement is a availability way to combat this process.