<国立科博専報>北海道日高・夕張山系における高山植物の植物地理学的研究
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The Hidaka-Yubari range, the axial zone of Hokkaido, is one o the most important localities of the Japanese alpine flora. During the last 17 years (1953-1970), the author has engaged field surveys of the alpine plants of this range. Thie axial zone of the range is geologically divided into two belts; the Hidka metamorphic belt in the east and the Kamuikotan belt in the west. From phytogeographical point of view, the former is subdivided into four districts, the Mt. Apoi, the southern Hidaka, the central Hidaka and the northern Hidaka districts, and the latter into three, the Nukabira-yama, the Mt. Yubari and the Mt. Ashibetsu districts. Mt. Kirigishi, a peak in the northwestern part of the Yubari range is composed of limestone of the Cretaceous age. Thus, the whole range is subdivided into 8 districts (Fig. 1)The alpine plants so far as l could recognized in this range are 209 species. Table 1 shows the distribution of the alpine plants for the 8 districts in this range and the distribution types of species. The number of the species in each distribution type of this range is compared with those of the Daisetsu Volcanic Mts., central Hokkaido, in Tables 2 and 3. It is concluded that the alpine elements of the Hidaka-Yubari ranges are closely related to the drying elements of the arctic or the boreal alpine flora. 0n the contrary, the Daisetsu Volcanic Mts. have the wetty elements of the same floras. It is noteworthy that the species related to the North-American elements are 41 in the Hidaka-Yubari ranges, most of which are found in the Daisetsu Volcanic Mts.; however, there are other 12,which are found only in the Daisetsu Volcanic Mts., and disjunctive species of the North-American elements. Two possible reasons are proposed to interprete this characteristic distribution; the continuity of volcanic island arcs, as pointed out by TATEWAKI (1938), and the wetty weather around the northern Pacific areas. The distribution of the drying alpine flora of the Hidaka-Yubari ranges is essentially related to the lack of wetty condition in this range because of steep relief of the mountains by the upheaval during younger Alpine orogeny. The alpine plants and their geological habitats are shown in Table 4. The relation of specific rocks and their corresponding alpine plants are as follows : (I) Ultrabasic rocks (a) Ultrabasic relic elements are Betula apoiensis, Arenaria katoana, and var. lanceolata, Callianthemum miyabeanum, Draba japonica, Lagotis takedana, Hypochoeris crepidioides, Saussurea chionophylla, Crepis gymnopus, Eriocaulon perplexum, Hierochloc pluriflora. (b) 2) Sedum pluricaule (MAXIM.) KUDO var. yezoense (MIYABE et TATEWAKI) TATEWAKI et KAWANO.-Syn. Sedum hidakanum TATEWAKI, ex KAWANO, 1957,in Acta Phytotax. Geobot., 17 : 1. 3) Trollius riederianus FISCHER et MEYER var. japonicus (MIQ.) OHWI forma citrinus (MIYABE) S. WATANABE, comb. nov.-Trollius citrinus MIYABE, 1936,Acta Phytotax. Geobot., in 13 : 15-16. 4) Oxytropis kudoana MIYABE et TATEWAKI var. hidaka-montana (MIYABE et TATEWAKI) S. WATANABE, comb. nov.-Oxytropis hidaka-montana MIYABE et TATEWAKI, 1933,in Trans. Sapporo nat. Hist. Soc., 8 : 3. Ultrabasic modified elements are Silene repens var. apoiensis, Thalictrumn foetidum subsp. glabrescens var. apoiense, Aruncus dioicus var. subrotundus, Potentilla matsumurae var. apoiensis, Viola brevistipulata subsp. hidakana var. hidakana, V. sacchalinensis var. alpina, V. yubariana, Angelica acutiloba subsp. lineariloba, Peucedanum multivittatum var. linearilobum, Tilingia ajanensis var. angustissima, Primula farinosa subsp.fauriae var. samanimontana, P. yuparensis, Veronica schmidtiana subsp. yezo-alpina f. exigua, Cirsium kamtschaticum var. apoiense, Saussurea riederi subsp. yezoensis var. kudoana. Taraxacum yuparense, Deschampsia caespitosa var. levis, Allium schoenoprasum var. yezomonticola, Tofieldia coccinea var. kondoi. (c) Elements of disjunctive distribution are Botrychum lunaria, Selaginella selaginoides, Juniper
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