Studies of woody species invasion on areas made barrened by volcanic debris deposites by eruptions is important for revegetation works there. Japan has many active volcanoes and disasters caused by eruptions have been increasing in recent years. Conservation of forests is a factor in the prevention of disasters.
Established natural forest stands provide the most important foundation for revegetation works. Typical stands were investigated on three volcanoes in Hokkaido Japan where natural forests have been well conserved.
Initial floristic composition was a significant factor in vegetation development on the volcanic deposit. The majority of species in the natural forest stands in these areas were so called pioneer trees such as Salix spp., Populus spp., Betula spp. and Alnus spp., but climax trees such as Abies sachalinensis and Picea jezoensis also established themselves together with lichens, mossee, herbs, shrubs and pioneer trees within a few years after the eruption. The number of woody species and individuals were large in the early stage but decreased with the development of stands. New spesies and individuals rarely established themselves after the early growth stage. Thus, twenty or thirty years after the eruption, even aged forest stands appeared.

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