Abstract
On the effect of snow patches, the processes of nivation and the resulting depression landforms have received some workers' attention. An important factor of it is the length of the season during which snow affects slopes. The author surveyed the distribution of snow patches and the conditions of topography, vegetation, and soil on certain slopes of Mt. Tairabyô (1, 983.7 m.) in the Mikuni Mountains in 1961 and investigated the relationship between them.
On Mt. Tairabyô, all snow patches melted away by early July and no remarkable erosion by snow patches was observed. The result of the study is considered to mean that snow action on the slopes of the area such as denudation and accumulation of peat is different from place to place due to the len gth of the season during which snow covers them.
The result of this investigation is summarized as follows:
1) The distributions of snow patches, depression landforms and the communities of hygrophytic herbs (chief species are: Moliniopsis iaponica, Fauna cristagalli, Tofieldia japonica, Primula nipponica, Drosera sp., Sphagnum sp., etc.)
2) Peat accumulates in all depression invesigated by the author. It is considered that such accumulations of peat on the slopes which look well drained are formed by successive supply of surplus melt-water of snow, as well as the luxuriance of hygrophytic herbs.
3) While, at the places where snow remains longer (by the end of June in this invesigation), the peat layer is thin and some indication of denudation can be seen.
4) At the places where snow melts away early (earlier than the middle of May), however, accumulation of humus is made and on the ridges, where snow disappears earliest, the soil layer is thin and short of humus.
5) The places where peat accumulates are habitats of hygrophitic herbs on the whole, but their mar-gins are invaded by Sasa kurelensis (a kind of bamboo-grass) which is a dominant species at the places where humus accumulates. This is considered to be related with the fact that peat is decomposed into humus at the margin.
6) Judging from the result, it can be concluded that these depressions have been transformed because of the annual reduction of lingering snow in this area, on the assumption that these depressions were formed by past nivation.
