ブナ極相林の再生過程 : IV.ギャップ形成

抄録

Nature of gap formation was studied to know the scale and speed of regeneration in a climax beech forest at Mt. Moriyoshi, Akita Prefecture, northeastern Japan. The maximum size of gaps in a 2.4 hectare plot was 470 m^2,and the gap amounted to 20% of the total land area. Number of gap making trees per gap was 1-5,2.0 on the average. These findings supported the presumption that beeches regenerate in the gaps made by the fallings or death of one or several canopy trees. The concentration of gap formations in particular years was not observed. On the average, 0.55-1.1 canopy trees per hectare died, and a gap area of 41-82 m^2 per hectare was made annually. The turnover time of the canopy layer in the forest, which was calculated from the rate of the gap formation, was 100-200 years. The turnover time was comparable to that calculated from the annual increment or death rate of biomass and the biomass of the forest. The dynamic equilibrium in a climax forest seemed to be sustained by these partial regenerations and gap formations. The effects of gap size on regeneration and the undergrowth of dwarf bamboo on the repairing of gaps were discussed.