Historical Responses of Quercus variabilis Growth to Environmental Changes in Southern Korea: Evidence from Tree Ring Width and δ13C

Historical growth response of Quercus variabilis, which is the most important deciduous timber species in Korea, was investigated using the width and C isotope ratio (C-13/C-12 denoted as delta C-13) of the annual ring from 1975 to 2007. Tree disks were collected from three Q. variabilis trees with different growth statuses from a site in the Mt. Naejang area, and analyzed for annual ring width and delta C-13. Basal area increment (BAI) of the annual ring was calculated from the width data, and carbon isotope discrimination (Delta) was calculated using delta C-13. The inter-correlations among BAI, Delta, and environmental variables were explored. The BAT was positively (p < 0.001) correlated with atmospheric CO2 concentration ([CO2]), reflecting increased net photosynthesis with [CO2], whereas the negative correlations of BAT with either NO2 (p < 0.05) or O-3 (p < 0.05) concentrations suggested that atmospheric pollution might have restricted tree growth to some degree. The Delta was positively correlated with both temperature (p < 0.05) and [CO2] (p < 0.001), and BAT was also positively correlated with Delta (p < 0.001). However, precipitation was correlated with neither BAT nor Delta, indicating that the precipitation amount is sufficient for tree growth in the study site. Such relationships suggest that stomatal rather than non-stomatal control is the predominant mechanism of photosynthetic acclimation of Q. variabilis under changing environmental conditions in the study site where water availability is not limited.