Abstract:Biological soil crusts(BSC) are complex organic integrities of cyanobacteria, green algae, lichens and mosses, fungi as well as soil microorganism, cementing with surface soil fine particles by their exude mucilaginous material. They are common cryptogamic communities in various arid and semi-arid regions of the world. Mosses are not only a common pioneer plant in the process of vegetation succession but also one of two groups with the highest biomass in the biological soil crusts. As pioneer plants, mosses are indispensable in the process of establishing the biological soil crusts, which play an important role in desert ecosystems, namely indicating vegetation type, holding soil, fixing sand, and preventing from erosion by water or wind. With regards to BSCs, up to now, it not only becomes one of international key scientific issues for earth surface processes in arid regions, but also cross highlight between geographical and biological knowledge. The mechanism of water absorption and adaptability of tolerant to drought of Taxiphyllum aomoriense were studied in this paper. The results indicated that the maximal water holding rate and amount of water uptake of the mosses were 9.74 times and 7 times higher than the dry mosses, respectively. According to the dynamic curve, Km value, Vmax value, inter water absorption and outer water absorption were 21.67 g and 10.42 g?g-1?DW?min-1, 28.91g and 8.56 g?g-1?DW?min-1, and 43.18 g and 1.76 g?g-1?DW?min-1, respectively. The concentration of soluble sugar was increased from 142.6 mg?g-1?DW to 344.3 mg?g-1?DW, which was 2.4 times higher than the control. However, the concentration of free proline was increased slightly. The activity of the antioxidant enzymes superoxide dismutase（SOD）did not change significantly, fluctuating over 0.04U?g-1?FW; and under the PEG6000 concentration stress that peroxydase（POD） was increased significantly until 20% of the state, after easing, and finally up to 131 U?g-1?min-1?FW, an increase of nearly 2 times content; the catalase（CAT）of the changes alike POD in tendency, but with less variation. Indicators of membrane lipid peroxidation MDA content first increased slightly and gradually fell down. The explanation that the systematic use of antioxidant enzymes to improve POD and CAT activity synergy SOD superoxide anion radical and to remove generated of H2O2 under superoxide anion radical action in cells of T. aomoriense. Therefore, the results indicated that the moss crusts were able to absorb and reserve water, and desiccation-tolerant adaptation. Besides, moss crusts had great effect on pedogenesis, which was very important to control rock desertificationin karst regions.