Ecological Succession around Mt. Yake, Kamikohchi. : I. Forming Process of Forest Vegetation.

Mt. Yake, located on the southern part of Hida Mountain Range as the only one live volcano in the range, has seriously affected the vegetation around it by its volcanic activities. On the slopes of this volcano, the forming process of forest vegetation was discussed after field surveys of 15 quadrate plots (10 were secondary forests and 5 surviving coniferous forests) and one belt-transect. The secondary forests were divided into three types; Betula forest, Betula-Abies forest and Larix-broadleaved forest. The former two type forests occurred on open areas where vegetations had been lost by eruption disasters but their soils saved, while Larix type forest on open area where its soil had hardly been disturbed. The sunny forest floor of these secondary forests was densely occupied by Sasa senanensis (dwarf bamboo). Especially, the first type Betula forest had very dense Sasa layer and few undergrowth of woody plants, so this situation suggested the future progress to a Sala-land after deteriolation of upper Betula trees. As the second type Betula-Abies forest had not a few undergrowth of Abies trees occurred on old stumps or near rocks where rhizomes of Sasa could not easily intrude on, the canopy layer seemed to be occupied by Abies and other subalpine conifers in the future. Larix-broadleaved forest, formed on the mud-flow, was thought to allow the emergence of tolerant conifers on its floor with the decrease of Sasa caused by canopy closure progress. Undisturbed coniferous forests had many coniferous undergrowth depend upon sparse density of Sasa, while forests survived but affected had few woody undergrowth influenced by the dense invasion of Sasa after canopy brake caused by eruptions. The result of belt-transect survey showed that both number and tree height of regenerating Abies increased with increasing distance from the crater. Dead standing trees indicated the wide distribution of Picea forest before the eruption of Mt. Yake.Article信州大学理学部紀要 23(1): 21-32(1988)departmental bulletin pape