2025 Volume 77 Issue 2 Pages 49-69
The aim of this study was to elucidate long-term changes in a conifer-deciduous mixed forest based on the life history traits of tree species. A 60-year survey was conducted in a permanent plot established in an Abies-Fagus forest, which represents the typical forest vegetation in the southern Pacific region of Tohoku, Japan. The results indicated that the composition and relative dominance of the main tree species showed little change, suggesting the long-term stability of this forest. However, between 2011 and 2021, changes reflecting the life history traits of tree species were observed, including a gradual slowdown in the decline of deciduous broad-leaved trees. This trend was associated with increased recruitment of Fagus japonica and Meliosma myriantha, likely facilitated by sprouting regeneration. Forest stratification also changed over time, with Carpinus spp. becoming dominant in the canopy layer, whereas M. myriantha was more concentrated in the shrub layer. Additionally, the number of shrub species, such as Callicarpa mollis, Ilex crenata var. crenata, and Cephalotaxus harringtonia var. harringtonia, increased significantly. In contrast, the abundance of pre-established seedlings of Abies firma, which had previously been growing in the shrub layer, decreased in number. Small individuals of A. firma were found exclusively beneath the canopy of mature trees, suggesting that despite its shade tolerance, A. firma is unlikely to regenerate successfully in the low-light conditions of the forest floor. These findings suggest that this conifer-deciduous mixed forest is undergoing structural changes influenced by the life history traits of its tree species. Over the past 60 years, the forest has matured into a more complex structure with increased tree species diversity.
