韓国智異山の落葉広葉樹二次林における林冠ギャップの特徴とギャップ更新

抄録

The gap disturbance regimes and gap regeneration behaviour were investigated in secondary deciduous broad-leaved forests in a lower-altitude stand and a higher-altitude stand, on a forest floor covered with dense dwarf bamboo on Mt. Jiri, South Korea. The species compositions of the canopy trees, suppressed saplings, and gap successors differed between stands. Gap disturbance regimes, such as the total gap area in the total survey area, and the density of the gaps also differed across stands. The densities of the canopy gaps in both stands were basically similar to those reported in other old-growth forests, although the percentage gap area and the size of each gap were smaller in these stands than those in old-growth forests. Different types of gap regeneration behaviour were identified among the major canopy and sub-canopy tree species. Quercus mongolica occurred in all regeneration categories (canopy trees, gap makers, suppressed saplings, and gap successors), indicating that this species can regenerate in gaps from saplings recruited before gap formation. Lindera erythrocarpa and Acer pseudo-sieboldianum lacked canopy trees and gap makers, suggesting that these species might not yet be large enough to reach the canopy layer, but could have sapling banks beneath the closed canopy. The gap regeneration behaviour observed on Mt. Jiri differed markedly from that in various old-growth forests in Japan. These differences might be attributable to differences in the natural disturbance regimes as well as to differences in the successional stages among the forests. There were also very few canopy and/or sub-canopy species with gap successors, suggesting that the canopy gaps in both stands do not play important roles in the gap regeneration of the component species of the stands. The dense cover of dwarf bamboo on the forest floor may explain why the gaps have little effect on the regeneration of many tree species.