Seasonal changes of floral frequency and composition of flower in two cool temperate secondary forests in Japan

Abstract

As a means of quantitatively evaluating the frequency and species richness of flower at forest community level, we studied flowering phenology throughout the growing season in two cool temperate forests at different successional stages. Flowering observed once for 2 weeks in 1997 and frequency was evaluated the number of 5 m 2 subquadrates flower appeared. The proportion of species that flowered was higher for herbs (76.3 in Pinus-dominated forest and 81.4% in Carpinus-dominated forest) than for trees (35.3 and 35.7%, respectively), shrubs (34.3 and 33.3%, respectively) and vines (21.7 and 11.8%, respectively). A high proportion of the canopy tree species flowered (68.8 and 87.5%, respectively). Similar bimodal distribution of flowering phenology was observed at the community level in both forests, although the total frequency of flowers was much greater in the Carpinus forest than in the Pinus forest. Tree and shrub life forms flowered from spring to summer, with two main flower types: wind-pollinated flowers (29.2 in Pinus-dominated forest and 14.3% in Carpinus-dominated forest) and dish-shaped, insect-pollinated flowers (66.7 and 76.2%, respectively). In contrast, herbs continued flowering until the autumn, and the proportion of funnel-shaped, insect-pollinated flowers was high. White flowers were most abundant for herb and shrub species.