中文摘要：

耐旱苔藓广泛分布于干旱半干旱荒漠地区，对荒漠生态系统稳定性与功能多样性具有重要作用。齿肋赤藓（Syntrichia caninervis）是古尔班通古特沙漠苔藓结皮层的优势物种，生于不同的微环境中。古尔班通古特沙漠冬、春季降雪频繁，并能形成稳定的积雪层。目前关于降雪与微生境对齿肋赤藓生理生化特征影响的研究极为缺乏。该研究探讨了初冬一次降雪前后活灌丛、死灌丛和裸露地3种微生境下齿肋赤藓相关生理生化特征。结果表明，与降雪前相比，降雪后各微生境下齿肋赤藓植株的含水量、荧光活性、可溶性糖含量、超氧化物歧化酶（SOD）和过氧化物酶（POD）活性均有明显提高，但脯氨酸、可溶性蛋白和丙二醛（MDA）含量有不同程度的降低。微生境对齿肋赤藓的生理指标有不同程度的影响，而且与降雪具有显著的交互作用（脯氨酸除外）。降雪前后，活灌丛下的齿肋赤藓具有较高的含水量和光合活性，以及较低的保护酶（POD和SOD）活性，裸露地则表现出完全相反的特点。表明前者面临的胁迫最小，生理活性最大，但抗性较弱；而后者具有更大的抗胁迫能力，但生理活性低。降雪后，脯氨酸、MDA、POD及SOD均与植株含水量呈显著负相关，而荧光活性、可溶性糖及可溶性蛋白含量与植株含水量为显著正相关，表明降雪降低了齿肋赤藓的水分胁迫程度，改善并促进了生理活性与光合作用，而且初冬的低温也起到了促进作用。

英文摘要：

Aims Water is the most constraining factor to the growth of plants in arid and semiarid regions of China. Biological soil crusts （BSCs） develop well in Gurbantunggut Desert and Syntrichia caninervis is a dominant species in the moss crusts of this cold desert. Compared to other desert ecosystems, the Gurbantfinggut desert is home to stable and abundant snow cover in winter. The moisturizing and warming effects of snow cover provide the desert mosses with optimal growth conditions. Our objective in this study was to determine how S. caninervis shoots utilize the special snow resources under different microhabitats in early winter.Methods The experiments were conducted from prior to the snowfall and until following the snow thawing at a long-term study site of the GurbantiinggiJt Desert. We measured the physiological and biochemical characteristics in S. caninervis in three habitats： the live shrub, the dead shrub, an exposed area. The shoot water content, chlorophyll fluorescence, proline content, soluble sugar content, soluble protein content, malonyldialdehyde （MDA） content, peroxidase （POD） and superoxide dismutase （SOD） activity were compared.Important findings The results showed that snowfall increased moss water content, the maximal photochemlcal efficiency of PSII （Fv/Fm）, soluble sugar content, SOD and POD activity. The content of proline and MDA were reduced with snow melting. Microhabitats influenced the physiological characteristics in S. caninervis, with the effects varying with snowfall event. The water content and chlorophyll fluorescence activity were significantly higher in samples under the living shrub, while in the exposed area S. caninervis had lower water content and chlorophyll fluorescence activity regardless of the snowfall cover. These findings suggested that the S. caninervis plants under the loving shrub experienced the least stress and had the best physiological performance but weak resistance, and that those in exposed area were more stress tolerant and had poorer