ブナ林構成樹種の太平洋型分布と日本海型分布  [in Japanese] One-sided distribution of the component species of the Japanese beech forest along either the Pacific or the Japan Sea  [in Japanese]

Twenty beech forests from the middle beech zone of various localities are divided into the Pacific type and the Japan Sea type on the basis of the ordination by both factor analysis and principal component analysis using the frequency of the tree species of each forest. It is worth notice that a good few of the species which are distributed geographically on both the Pacific side and the Japan Sea side show one-sided distribution in this study. As to the species occurring one-sidedly on the Pacific side, both the northern limit of geographical distribution and the upper limit of vertical distribution of them are lower because of high susceptibility to the cold of winter than the species which occur on both sides. In the beech zone on the Japan Sea side, the cold of winter is bitterer than that in the zone on the Pacific side in spite of the same warmth of summer, so these species cannot appear on the Japan Sea side in this study not to go up to the middle part of the beech zone. On the other hand, many of the species which occur more abundantly not also in gap stands but also in closed stands not severely suppressed by canopy beech trees with relatively small crowns on the Japan Sea side are found on the Pacific side but limited to only gap stands owing to harsh suppression in closed stands by canopy beech trees with vigorously extending crowns. Due to the shortness of shoot longevity and the lack of dormancy of buried seeds, some of them cannot subsist in beech forests on the Pacific side where the regeneration under gaps does not start through many years before the death of dense Sasa cover.