Ecological and palynological studies on the types and distribution of the Hiba Vitae (Thujopsis dolabrata var. hondai) forest

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Var. Hondai, a relic of the arcto-tertiary conifers, is widely distributed in northeast Japan, from Noto Peninsula to Hiyama, Hokkaido in north, but scarcely under heavily snow-fallen climate. It often forms the unique forests, admixed with Fagus crenata in Hiyana, Aomori, etc., with Tsuga diversifolia in the Kitakami Massif, and with Cryotomeria japonica in the north Ou mountains and Sado Island.The distribution and growth of Thujopsis is apparently affected by the snow stress; the tress are, under the typical Japan Sea climate with heavy snow fall, restricted to the lowlands. While in the area transitional between the Japan Sea climate and the Pacific one they go up to the higher altitudes.The pollen or macro-remains of Thujopsis were detected even from the deposits of the late-Pleistocene and the glacial refugiz were recognized:it probably survived in the subalipine or boreal conifer forests and even in the forest tundra zone. The pollen analytical studies were also made on some of the post-gracial deposits. The post gracial changes of the Thujopsis forests were discussed in reference to the mechanism with which the Fagus・Thujopsis forest, the Tsuga・Thujopsis forest and Cryptomeria・Thujopsis forest were estabished under the respective habitat condition.