Since 2008, the Kaisho forest has suffered from Japanese oak wilt and about 60% of oak trees were wilted. Such mass mortality can results in significant impact on not only forest structure but also seedling community. Here, we aimed to determine the temporal changes in forest structure and seedlings, together with light conditions, soil water content, and seed/litterfall production, after the damage of Japanese oak wilt.
The study was conducted at three plots in secondary forests of the Kaisho forest during 2008-2018. At each plot, 16 seedling quadrats and 16 litter traps were set, and tree census has been carried out every 2-3 years.
Total basal area substantially decreased due to death of large oak trees and then gradually increased, whereas stem density quickly recovered and we found the highest stem density in 2018 in all plots. Canopy openness and soil water conditions showed general decreasing pattern but the values fluctuated among years and plots. The density of current-year seedlings drastically increased during 2012-2013 in all plots, and its high density was maintained in 2018 only in one plot. These results indicate that canopy gaps are closing by vigorous growth of sub-canopy trees but the pattern differs among plots.