Abstract: Biological soil crusts (BSC) are widespread in arid and semi-arid regions, and play significant roles in ecosystem stability maintenance and ecological balance. With successional stages of BSC (algae, lichen and moss) in the southeastern fringe of the Tengger Desert as test objects, and studies preliminarily the effects of snow on chlorophyll fluorescence parameters, photosynthetic pigments, malondialdehyde (MDA), and soluble protein of different types of crusts. Results show that different BSC species exhibit different responses to snow on photosynthetic physiological characteristics. A moderate amount of snow stimulates photosystem Ⅱ reaction center, and increases contents of photosynthetic pigments and soluble protein, decrease MDA content, while excess amount of snow prevents photosynthetic electron transport of algae and lichen crusts, and photosynthetic pigments contents and soluble protein synthesis decreases, MDA content increases, which cause photoinhibition. Our study indicates a moderate amount of winter snow is favorable to BSC at the photosynthetic physiological level, while moss crusts are more suitable to excess amount of snow, its relative molecular mechanisms still need further research.

Key words: water, biological soil crusts (BSC), snow, chlorophyll fluorescence, photosynthetic pigments