Abstract: The unique morphological structure and physiological characteristics of bryophytes enable them to grow in the harsh habitat with extreme drought and cold climate. As one component of alpine grassland on the Qinghai-Tibet Plateau, bryophytes play an important ecological role. The present study aimed to describe the characteristics of bryophyte associations in the alpine grassland of Tibet and explore their environmental driving factors. Forty plots were set up across the alpine grassland of Tibet. Bryophytes were collected and recorded from quadrats. Quantitative classification and ordination of the bryophyte associations were analyzed by two-way indicator species analysis (TWINSPAN) and canonical correspondence analysis (CCA), based on species and ecological data. A total of 36 species belonging to 18 genera and 9 families were recorded, all of which were mosses. The most species-rich family is Pottiaceae. The species number of genera Didymodon and Bryum accounted for one-third of the total species. The dominant species were Didymodon tectorus, Barbula gracilenta, Didymodon fallax, and Didymodon michiganensis. The dominant life form is turf, accounting for 83.33% of the total species. Two-way indicator species analysis divided the bryophyte associations into eight types (i.e. Bryum uliginosum association, Didymodon fallax + Anomobryum auratum association, Didymodon tectorus + Didymodon fallax association, Didymodon tectorus + Didymodon tophaceus + Didymodon fallax association, Didymodon michiganensis + Didymodon tectorus + Barbula gracilenta association, Barbula gracilenta +Didymodon tophaceus association, Didymodon constrictus + Didymodon ditrichoides + Didymodon rivicola association, Distichium brevisetum association). Some of the plots were clustered on the CCA ordination graph, which indicated the continuity of the associations and the complexity of the relationships between bryophytes and the environment. The CCA results showed that mean annual precipitation was the primary factor affecting the distribution of bryophyte associations in the alpine grassland of Tibet, followed by soil pH, silt fraction, NDVI, altitude, mean annual wind speed, and mean annual temperature.

Key words: mosses, Qinghai-Tibet Plateau, alpine grassland, ecological factor.