中文摘要：

在西藏河谷区拉萨、山南、日喀则的6个人工牧草地及其边界共设置了28个样地,通过样方调查和标本采集,鉴定得到苔藓植物2科6属13种,其中真藓（Bryum argenteum）为调查区广布种。该地苔藓植物群落的特点表现为各试验地之间物种丰富度区别明显,而物种均匀度的变化较小;CCA分析表明,小生境的温度与相对湿度对苔藓生长与分布的影响较大。在人工牧草地边界、种植一年以上的牧草地和一年以内的牧草地等3种类型样地中,由于人为干扰程度的差异,人工牧草地边界的苔藓物种最丰富,而一年内的牧草地几乎没有苔藓植物;随着土壤稳定时间的延长,才逐渐形成以真藓属为优势的苔藓植物群落。在牧草种植过程中,1年内采用刈割方法而不进行放牧活动,将有助于保障人工牧草的正常生长和防止水土流失,降低荒漠化发生的可能性。

英文摘要：

28 plots of 6 sites were investigated to identify the bryophytes communities on planted pastures in valley area of Tibet,China.3～5 quadrates of 25 cm×25 cm with 100 grids were selected to count the coverage of bryophytes in each plot.The result showed that there were 13 species of bryophytes（including 2 varieties）,belonging to 6 genera and 2 families,and Bryum argenteum was widely distributed in the whole research area.The bryophytes communities were obviously different on species richness among the plots,but on species evenness.The similarity between any two communities was higher if their niches were more similar to each other.Based on Canonical Correspondence Analysis（CCA） of relationship between bryophytes and environmental factors,it indicated that the distribution of bryophytes was more affected by temperature and relative humidity of the niche.The highest species diversity was located around planted pastures and the lowest（almost no bryophyte） was located inside the planted pastures which were planted this year.As time went on,the bryophyte communities,dominated by genera Bryum,would be formed in the new planted pastures with decrease of the disturbances and stabilization of the topsoil.It consented that the results above can be applied for avoiding soil and water erosion,and reducing the possibility of desertification as well if the planted pasture will be cut instead of being grazed around the first planted year.