To certify the effect of the reproduction on trunk radial growth, trunk girths of Fagus crenata were measured around the time of moderate masting event in 2013. The amount of flowers in spring and those of fruits in autumn were checked visually. Additionally, digital dendro meters were installed on 18 trees to monitor trunk growth in high-resolution time-scale.

In April 2013, 18 of 71 F. crenata dominant trees in the study plot flowered more than 50% of upper canopy part (mass-flowerings), and 19 trees were observed as the mass fruitings in October. The trunk girth increment in mass reproductions was smaller than few reproductions (< 50% of upper canopy flowered/produced fruits), but the relationship between the trunk girth increments and the degree of reproduction was not significant. Although the logs of dendro meter brought us useful information about the radial growth rate and the moment of radial growth settled, neither growth rate nor the moment of growth settled showed clear difference between mass- and few-reproduction trees. These results suggested that mass reproduction suppressed trunk growth in F. crenata, but individual variation of radial growth was too large to detect the relationship easily.