オオミズナギドリの影響下における冠島のタブノキ林の群落構造

抄録

Machilus thunbergii forests were studied in Kanmurijima Island, Kyoto Pref., to clarify the influence of disturbance by birds' nesting and streaking on the community structure of the forest. Density of nests was negatively correlated with the number of plant species and individuals, the skewness of frequency distribution of height and DBH, Shannon H' and the relative basal area of Aucuba japonica, respectively. Species composition, species diversity index, dominance-diversity curves, skewness of height distribution, crown projection diagrams and other ecological characteristics showed that the disturbance by birds resulted in poor vegetation and the development of simple stratification. The species diversity became slightly higher as the aboveground biomass increased. In these forests Mallotus japonicus very often filled up gaps of canopy trees, and seedlings and saplings of Machilus thunbergii were growing around patches of Carex matsumurae and some herbs as stable spots for germination on the forest floor.