Relationships among Radial Growth of Cryptomeria japonica, Carbon Budget of a Forest Ecosystem, and Climate Factors in a Cool Temperate Zone

In this study, we analyzed correlations among the earlywood width (EW) and latewood width (LW) chronologies of Cryptomeria japonica, annual stem biomass increment derived from tree-ring width, climatic factors, and carbon budget of a forest ecosystem [gross primary productivity (GPP), ecosystem respiration (RE) and net ecosystem productivity (NEP)] in Takayama evergreen coniferous forest, central Japan. EW was found to show a significant positive correlation with stem biomass increment, whereas LW showed no significant correlation. EW also showed significant positive correlations with temperature from spring to summer of the previous year and from winter to spring of the current year, as well as significant positive correlations with GPP and RE during these periods. Moreover, GPP and RE showed positive correlations with temperatures during the period from winter to spring. These results indicate that the temperature from spring to summer of the previous year may affect needle production, thereby contributing to the photosynthetic capacity during the growing season of the following year, and consequently leading to a variation in EW. It is also suggested that temperature from winter to spring of the current year may affect photosynthesis, which contributes to the amounts of stored photosynthates, thereby leading to a variation in EW. Moreover, our findings indicate that the increment in stem biomass changes according to EW.