Abstract: In an alpine snowbed on the eastern Tibetan Plateau, three portions were established along snowmelt gradient. At each portion, the phenology and population distribution pattern of three alpine species(Pyrethrum tatsienense, Leontopodium longifolium and Polygonum macrophyllum) were tested. The results showed that from early-to late-melting portion, phenological phases of three species delayed to different extents. Plant emergence delayed 12-14d, first flowering delayed 6-8 d and peak flowering delayed nearly 6 d. For each species, however, consenescence at three portions did not differed significantly, indicating that growing season length of a species at late-melting portion shortened. At population level, the distribution pattern of Leontopodium longifolium and Polygonum macrophyllum varied as the snowmelt delayed, changing from cluster pattern at early-melting portion to random pattern at late-melting or medium portion. Pyrethrum tatsienense showed cluster pattern at three portions. However, its intensity of cluster weakened as the snowmelt delayed.

Key words: alpine snowbed, phenology, population distribution pattern, snowmelt gradient