Beech forests especially those in the lower and southern distribution limits are assumed to be severely affected by climate change. Reduced growth and elevated mortality have been increasingly reported in European countries in this decade. In Japan, such evaluation is still limited. Furthermore, beech forests in the Western Japan may be also suffering from pollen limitation and reduced genetic diversity due to forest fragmentation during long human interferences. To evaluate the synergetic effect of forest fragmentation and climate change, we started a survey in the beech forest in Mt. Takanosu, which is isolated from other beech forests. Dominant species were Fagus crenata and Abies firma, suggesting that this forest is located in the boundary of cool temperate and warm temperate zones. Beech trees showed positive aboveground biomass growth. Mass flowering was observed in 2015 and 2018 but few sound acorns were produced. These result suggests that regeneration of beech trees is unsuccessful in this forest even though diameter growth of adult beech trees does not show any sign of degradation.