The relationship between climatic conditions and the distribution of the epiphyllous liverwort, Cololejeunea nakajimae, was investigated in Niigata Prefecture and its adjacent regions, central Japan. The species is widely distributed in mountainous areas where there is deep snow in winter. It frequently grows on leaves of the evergreen shrub Camellia rusticana, reducing the effects of strong sunlight and drying winds. Heavy snow covers the liverwort in winter and depresses it and the host shrubs to the ground. The liverwort is well adapted to conditions of snow cover and is probably more tolerant of low temperatures than the host C. rusticana, but the extreme wet conditions under the heavy snow may restrict its occurrence in the midwestern region of the prefecture.

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To compare the species composition of bryophytes epiphytic on various host tree species, we obtained samples from Tsuga diverszfolia, Abies veitchii and Larix kaempferi growing on ridges on the north and south slopes of the subalpine coniferous zone on Mt. Fuji, Yamanashi and Shizuoka prefectures. A total of 7 moss taxa and 14 liverwort taxa were recognized. The total number of epiphytic bryophyte species on the trunks of T.diversifolia was greater than that on the trunks of A. veitchii, corresponding to the bark form. Although the bark of L. kaempferi was similar to that of T. diversifolia, the total number of epiphytic bryophyte species on the trunks of the former was lower than that on the latter. The number of epiphytic bryophyte species on the trunks of a single tree species also varied with the forest type of which the tree species was a part. In pure forest dominated by only evergreen coniferous trees such as T. diversifolia and A. veitchii, or only deciduous trees such as L. kaempferi and other broad-leaved trees, the number of epiphytic bryophyte species was low. Conversely, in mixed forest containing both evergreen coniferous and deciduous tree species, the number of epiphytic bryophyte species was higher than in pure forest. We conclude that the variations in environmental conditions around tree trunks in mixed forest are more suited to the growth of epiphytic bryophytes in comparison with pure forest.

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