鳥取県西部朝鍋鷲ヶ山－宝仏山地域の自然環境 : 地形・地質および植生

The Asanabewashigasen-Houbutsusan area, western Tottori Prefecture, is a mountainous highland with elevation over one thousand meters. Saved from recent artificial reformation, the natural environment there is well preserved. The area consists geologically of lower to upper Mesozoic (meta-)sedimentary rocks, upper Cretacous to Paleogene volcano-plutonic rocks and uppermost Cenozoic sediments. The fairly restricted distributions of the latter sediments indicates the the mountainous area has been subjected to uplifting and subaerial erosion through late Cenozoic time. The climate type of Japanese Islands is divided into three, i.e., the Japan Sea, the Pacific Ocean and the transitional climate types. The transitional one is called also the Semi-Japan Sea climate type, based on less amounts of winter snowfall. The investigated area is of the the Semi- Japan Sea climate type. In addition, the present investigation suggests that the southwestern limit of Ilex leucoclada and Sasa kurulensis, characteristic of the Japan Sea climate type, locates between Mt. Kenashiyama and Mt. Houbutsusan. Many plants including scarce ones such as Erytronium japonicum, Galium kinuta, Tripterygium regelii, Lepisorus ussuriensis var. disrans and so on have survived in the Aasanabewashigasen-Houbutsusan area, but not in the Daisen volcanic area to the north, where a Pleistonce volcanism forms a big cone 30km across. This fact suggests that the flora in the latter area is still immatured probably due to the geological youthfulness of the volcanic area.