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Stand structure of an old-growth forest was studied by tree (〓4.0 cm in DBH) census in a main plot of 1.3 ha and 8 additional plots (0.525 ha in total) located in the Mt. Moiwa Forest Reserve, central Hokkaido, northern Japan. Major tree species with 〓1.0% of the relative basal area and of relative number of trees (Acer mono, A. mono var. mayrii, Kalopanax pictus, Magnolia knbus var. borealis. M. ohovata, Prunus ssiori. Tilia japonica, and Ulmus laciniata) have positive values of skewness in DBH, which shows the abundance of smaller-sized stems. All stems over 1.3 m high in the main plot were mapped to clarify the relationship between stem densities and canopy states. Although advances from sapling (> 1.3 m tall and < 4.0 cm DBH) to small tree (10.O cm 〓 DBH <25 cm) for all major component species, except P. ssiori and U. laciniata, were independent of canopy s tates, those of P. ssiori and U. laciniata depended on canopy gaps. Betula spp. was the most abundant gap makers, but T. japonica and A. mono (including var. mayrii) were dominant species in the main plot. This suggests the shift of dominant species in the forest of the study site. Historical records of disturbance demonstrated that selective cuttings of conifers during the late 19th century were responsible for the dominance of Betula spp. and the subsequent shift of dominant species. This fact suggests that artificial disturbance plays an important role in the establishment of Tilia japonica-Acer mono forest considered to be a climax of the mixed deciduous broadleaf/conifer forests.