STUDY ON PERIGLACIAL PHENOMENA AND ENVIRONMENTS OF THE DAISETSUZAN MOUNTAINS,CENTRAL HOKKAIDO

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From 1992 to 1993, observations of air temperature, solar rediation and soil temperature, and vegetation research were carried out in the alpine zone of the Daisetsuzan Mountains of central Hokkaido, Japan.The study area is under a periglacial environment.According to the air temperature observation for a year, the annual mean temperature was -3.0ﾟC.It means that the study area belongs to a discontinuous permafrost zone. In fact, permafrost is distributed in the alpine zone as shown by palsa bog. The distribution of permafrost, however, is restricted by ground surface conditions ; snow cover, vegetation cover etc.Ground temperatures were measured in the autumn of 1993. Higher ground temperatures were recorded in the alpine tall herbaceous community and the Sasa kurilensis community, where the ground surface are covered with more than 100 cm of snow in winter. The depth of snow in the Pinus pumila community exceeds 100 cm as well. But the autumn ground temperature in the community is lowest except for that in the permafrost area. The ground temperature of wind-blown bare ground falls below -20ﾟC in winter and rises higher in summer than in the ground under other other surface conditions. As a result, the temperature of the wind-blown bare ground is comparatively high in autumn. The observation of ground temperature in autumn suggests that permafrost occurs in the wind-blown bare grounds with a surface layr of loose structure, with a peat layr more than 60 cm thick, and with other thick organic layrs such as humus layr and lichen mat.Abave ground conditions affect a distribution of alpine plants. In the vegetation research in 1993, Carex rotundala Wahlenb. was found newly in Japan. The species is distributed in the circumpolar areas of the Northern Hemisphere.