ハイマツ群落の生態と日本の高山帯の位置づけ

抄録

There has been a discrepancy between the European view of the term “alpine” zone and the Japanese one. European researchers consider orthodoxically the alpine zone as a tree-less area covered with ericaceous dwarf shrubby cushion plants between the timberline at its lower limit and the climatic snow line at its upper limit. Japanese researchers have traditionally reckoned the alpine zone as an area covered with the extension of the Pinus pumila thickets admixing many alpine-boreal elements above the forest limit. Japanese phytosociologists have recently payed attention to such a traditional Japanese view of the alpine zone. The author is much interested in this problematic usage of the term “alpine”; in the present study, an approach is made to this subject through his own research on the ecology of the P. pumila thickets carried out in Mts. Taisetsu, Central Hokkaido.
Compared with the European alpine communities with those of Japan, it is clear that the latter is fundamentally different from the former because of the well-establishment of the P. pumila thickets rich in boreal forest elements and the high productivity of P. pumila itself which is nearly equal to that of the Abies-Picea forest. Thermally, WI of the area occupied by the P. pumila thickets is no less than WI=15 that has been considered to coincide with the northern forest limits. Further, P. purnila thickets differ fundamentally from the conifer krummholz which is highly popular to the European high mountains though the thickets look like the krummholz forms. The latter forms the component of the forest while the former never forms the forest.
The author concluded that the traditional definition of the “alpine” zone in Japan should be abandoned, and that the P. pumila thicket belongs essentially to the upper part of the forest zone in the vertical distribution. Another conclusion is that the so-called alpine zone occupied with the extension of the P. pumila thickets in Japanese high mountains as well as at Mts. Taisetsu does not strictly correspond to the krummholz zone at the upper part of the forest zone in European high mountains
The Japanese alpine zone is a unique and independent vegetational zone, and it is not the fragment of the forest zone such as the conifer krummholz zone in Europe.