1977年有珠山噴火後の森林植生の14年間の推移 : 特に高木類の対応パターン

抄録

Forest vegetation was severely disturbed by the 1977 eruption of Mt. Usu in Hokkaido. However, most of the intermediately disturbed sites were immediately reforested by decurrentgrowth species(e. g., Acer mono)which survived through the eruption and then grew rapidly. The decurrent-growth species also established their seedlings there to some extent. These responses could be regarded as competitive ones because intermediately disturbed sites are characterized by severe competition. In general, the shade intolerant excurrent-growth species(e. g., Populus maximowiczii)did not invade these sites even though they were severely damaged at the time of the eruption. Unexpectedly, they responded to a few intermediately disturbed sites which they had occupied before the eruption and therefore were damaged severely. Consequently, they reoccupied these sites immediately. They also invaded a few strongly disturbed sites caused by severe volcanic impacts. However, the growth activity was extremely low in these sites ; therefore, the reforestation scarcely progressed. Because such an unharried response could correspond rather to stress tolerant behavior, it was suggested that early successional excurrent-growth species exhibited not noly early succession but also stress tolerant behavior collectively. Their wide-spread distribution was concluded to be due to two such aspects of behavior.