1974 年 24 巻 1 号 p. 35-42
Dormant one-year-old twigs of about 60 tree species were collected from mature trees growing in different altitudes on Yakushima Island in early January. Evergreen broad-leaf trees growing in the low altitudes below 200 m above sea level, resisted freezing between -3 and -15℃, with the exception of Ficus retusa and Kandella Candel. Most of the tree species growing near the top of Mt. Taichu (1511 m) resisted freezing to -20℃. Three species, Sorbus commixta, Pieris japonica, Rhododendron Metternichii survived freezing down to -25℃ or below. Abies firma collected at about 1200 m altitude was hardy to about -25℃. This fir was found to be nearly as hardy as those of the northern boundary of its natural ranges, Fukushima Prefecture. A similar trend was observed in most of the evergreen broad-leaf trees from between Yakushima Island and Ibaraki Prefecture. However, slight intraspecific differences were observed in the freezing resistance among the evergreen broad-leaf and coniferous trees tested. These differences generally appeared to be closelv related to the winter coldness of their native habitats.