The growth trajectories of trees are not fully understood due to their long lifespan. We characterized the population dynamics of the canopy tree Castanopsis cuspidata (Thunb.) Schottky in a Japanese warm-temperate forest over 49 years (1966–2015). Our study was initiated approximately 50 years after our study site was clear-cut. The forest had a closed canopy for the first 23 years of the study. Strong typhoons in 1991 and 1993 seriously damaged the forest, and since then the forest has been recovering from these disturbances. The diameter distribution of this species was bell-shaped in 1966, suggesting that the trees emerged simultaneously after the clear-cut in the 1910s, and the recruitment of trees has remained unchanged since then. The lack of recruitment of C. cuspidata before the typhoon disturbance supports this conclusion. Assuming that the C. cuspidata trees in 1966 were cohorts that were established soon after the clear-cut, the size differences reflect differences in growth rate, with small trees corresponding to slow growers and large trees corresponding to fast growers. Before the typhoon, slow growers had low survival, and the mortality rate of fast growers was low. Many fast growers were uprooted or snapped by strong winds by the typhoons. However, their mortality rate did not differ from that of slow growers because many slow growers were killed by large fallen trees. The growth of some slow-growing survivors increased after the typhoon, which allowed them to rapidly reach the canopy. Therefore, the typhoon altered the distribution of canopy trees among slow and fast growers. Survivors experienced faster growth than trees that died during the census period, suggesting that growth rate provides a robust indicator of future survival. Before the typhoon, the survival of fast growers was higher than that of slow growers. This suggests that fast growers disproportionally contribute to reproduction compared with slow growers. However, no recruited tree was observed in this subperiod, suggesting that fast growers made no contribution to reproduction. Fast growers might not play a more significant demographic role than slow growers in this species.

This study was performed in a warm-temperate evergreen forest in Minamata, Kyushu, Japan (33°19’ N, 130°80’ E, 400 to 637 m above sea level). A 33-ha secondary forest at our study site was designated as a forest reserve for the conservation of genetic resources for timber trees by the Japanese government. The forest is dominated by the evergreen broad-leaf trees Castanopsis cuspidata, Quercus acuta (Thunb. ex Murray), Q. salicina (Blume), and Machilus thunbergii (Sieb. et Zucc.), which regenerated after the clear-cut between 1910 and 1920 for charcoal production. Therefore, the trees in the forest were established after the clear-cut from coppices, dispersed seeds, or soil seed banks. Castanopsis cuspidata is a common evergreen broad-leaved tree species in Japanese warm-temperate forests. Castanopsis cuspidata grows to approximately 20 m tall and over 100 cm in dbh.

Within the forest, a permanent plot of 40 m × 40 m was established in 1966 approximately 50 years after the clear-cut for studies of the International Biological Program, and it has been monitored since then. Thus, 49 years of data were collected. All tree stems with dbh ≧ 4.5 cm were monitored in the plot. These stems were tagged, mapped, and identified, and dbh measurements were taken. Instances in which trees had multiple stems because of coppice regeneration were noted. All trees inventoried in previous censuses were remeasured to estimate growth and mortality rates. Trees were recorded as recruits, and their size was measured when new trees reached dbh ≧ 4.5 cm during the census period. Censuses were conducted in 1966, 1989, 2001 and 2015.