We investigated population structures of woody seedlings emerged and established under canopy gaps, and their effect factors in the large-scale mature forest, Tadasu-No-Mori Forest in Kyoto city. There were 36 species, 4335 woody seedlings in 2012. The whole population density was 307.9 individuals/100m2. Population density of Celtis sinensis was the highest of all species, 81.6 individuals/100m2. Appearance frequency of Quercus glauca seedlings was the highest, 58.0%. Population densities of C. sinensis, Zelkova serrata and Aphananthe aspera seedlings had been significantly higher when the diffuse site factor was more than 12%. There had not been significantly differences of population densities of seedlings between modes of gap maker death, uprooting and trunk snap or standing dead. The 62 sites were classified into the two groups by TWINSPAN. The one group was that dominant species was C. sinensis and the mean diffuse site factor was significantly higher. The other was that dominant species was Q. glauca and the mean basal area of evergreen broadleaved mature trees was significantly higher. The population density of A. aspera seedlings was relatively lower than those of C. sinensis and Z. serrata. It indicates light condition in the forest floor of this site was insufficient for regeneration of A. aspera.
