Flowering phenology of alpine plant communities was observed at seven sites (two fellfields, two alpine meadows, and three snowbeds) in 1996 and 1997 in the Taisetsu Mts., northern Japan. These sites were selected along a gradient of snowmelt time. In total, flowering phenologies of 39 species were compared across the seven sites. The length of flowering season within communities decreased with lateness of snowmelt from 88 days at the fellfield site to 32 days at the snowbed site. The onset of flowering varied among species at the early snowmelt sites, and it became concentrated within narrow periods among species at the later snowmelt sites. Interspecific overlap of anthesis was large in the late flowering season at the earliest snowmelt site, whereas it was large in the early flowering season at the snowbed sites. Such changes in flowering patterns at community level along the snowmelt gradient were considered to be induced by the difference in temperature sequence after snowmelt among the sites, i. e., the increasing pattern of the effective cumulative temperature. Thus, the time of snowmelt affects not only the flowering phenology of individual species but also the flowering pattern of a whole community. Some species growing in the fellfields changed the temperature-demand for onset of flowering which was considered as an adjustment to decrease the interspecific overlap of anthesis within the community.
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