Comparative study on ecological chracteristics of seedlings between Fagus crenata and Fagus japonica.

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Ecological characteristics of current-year seedlings were compared between co-occurred Fagus crenata (Fc) and F.japonica (Fj) to understand the process of seedling establishment on the forest floor. Seedling populations were censused and growth of the seedlings under different light conditions, and photosynthetic capacity were surveyed. Mast years of both species were determined by age of saplings and growth patterns of annual rings of mother trees.1.Light condition on the forest floor was favorable in spring when the seedlings had cotyledons and severe in summer. Survival of the seedling of Fc was higher than Fj. Mortality of seedlings was in part due to grazing by insects.2.Differences between species in phenology and morphology were observed ; cotyledons of Fj were larger and their longevity was longer (more than twice) than Fc, leaves of Fj were thinner and more spreading and emerged later than Fc. The longevity of the cotyledons was longer in more shaded condition in both species. … More 3.There were not significant differences in total biomass between species in any light conditions. Fj was allocate more dry matter to aerial parts than Fc in more favorable light condition. Maximum photosynthetic rate of Fc was higher and net assimilation rate was higher than Fj. These showed relative trends in light-use of each species ; Fc uses different levels of light resource efficiently by higher flexibility in photosynthetic capacity while Fj by higher morphological flexibility.4.Photosynthetic characteristics of cotyledons were similar to those of typical sun-leaf in both species and maximum photosynthetic rate was comparable to that of leaves. Photosynthetic production by cotyledons was not negligible in annual net production of Fc and more important in Fj.5.Mast years during resent 25 years were 7 times in Fc and 6 times in Fj, and not synchronous between species. Significant correlation between masting and radial growth of trunk was observed in both species, and mast years in the past was capable to be determined from the annual ring patterns. Less