中文摘要：

生物土壤结皮的生存环境是地球上自养生物生存最为极端的生境之一，真藓是荒漠结皮中最为重要的组分之一。很少有研究涉及冬季降雪对结皮层生物体的影响。以宁夏沙坡头人工植被区内发育良好、长势均匀的真藓结皮为研究对象，系统研究降雪影响下荒漠地区藓类结皮层真藓的光合色素含量、可溶性糖含量、可溶性蛋白含量、丙二醛（MDA）含量以及脯氨酸含量的变化，并探讨其对降雪的生理生化响应。采用了4个降雪处理，分别是无降雪、0．5倍降雪、1倍降雪、2倍降雪。结果表明：随着降雪量的增加，其光合色素含量和可溶性蛋白含量显著增加；而可溶性糖含量、游离脯氨酸含量以及MDA含量均呈下降趋势。研究结果表明，作为生物土壤结皮重要水源之一的冬季降雪，能够为结皮层生物体提供适宜的水分条件以激发其生理生化活性，对维持荒漠生态系统的稳定性具有重要作用。

英文摘要：

Biological soil crusts （BSCs） endure the most extreme habitats in the world. They grow on the soil surface in desert regions and withstand extreme temperature, drought and intense radiation. BSCs comprise many kinds of micro- organisms, such as bacteria, algae, lichen and moss. Water is the main limiting factor in the growth of BSCs, and winter snowfall is likely to be one of their important water resources. However, few studies have explored the effects of snowfall on BSCs untill now. In this study, moss crust （Bryum argenteum） was sampled from a revegetated area in Shapotou, at the southeastern fringe of the Tengger Desert. The effects of snowfall on the content of photosynthetic pigment, water-soluble sugar, water-soluble protein, proline and malondialdehyde （MDA） in B. argenteum were measured. Four snowfall treatments were applied： non-snowfall （control, 0S）, half of the ambient conditions （0.5S）, ambient snowfall （1 S）, and double ambient conditions （2S）. The 0S samples were each covered with a euphotic plastic disc of 10 cm diameter to exclude all snowfall. The remaining treatments accepted natural snowfall, then half of the natural snowfall was removed from 0.5S samples and an additional mass of snowfall equivalent to natural snowfall was added to the 2S samples. The results show that with an increase in snowfall, the chlorophyll and water-soluble proteins increase significantly, while the water- soluble sugars, proline, and MDA decrease. Snowfall results in an increase in the chlorophyll and water-soluble protein content, hence, leads to a pontential promotion of the ability of photosynthesis and metabolism. At the same time, increased snowfall reduces the soluble sugar, proline, and MDA content, thus affecting B. argentum＇s osmotic adjustment and membrane lipid peroxidation. This study elucidates the physiological and biochemical activities of B. argenteum under snowfall, and has academic and practical significance in maintaining the stability of desert ecosystem.