Distribution factors of alpine moor vegetation on Mt. Hiragatake, Central Japan

Abstract

Mt. Hiragatake is located on the boundary between Gunma and Niigata prefectures (Oku-tone and Okutadami regions), central Japan. This mountain has a flat top covered with alpine moor vegetation. Previous studies indicated that this moor was formed by heavy snowfall, but the details of its formative factors are not clear because this opinion is qualitative. To clarify the formative factors of the moor, we investigated the detailed relationship between snow cover and vegetation, including that on the moor. The prevailing winds in winter and their effects on snow cover distribution were investigated, using wind-shaped trees and snow cornices as indicators of those winds. On the basis of the similarities between the moor and the vegetation seen in snowy environs around the summit of Mt. Hiragatake, this study confirmed that the formation of the moor was mainly influenced by snowfall. In addition, plant species more adapted to dry environs were seen in parts of the moor. Such vegetation was found in areas where snow had been blown off by strong wind. This suggests that the Mt Hiragatake moor vegetation is a result of residual snow and wind flows.