Historical responses of Quercus variabilis growth to environmental changes in Southern Korea: Evidence from tree ring width and δ 13C

Abstract

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 (13C/12C denoted as δ13C) 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 δ13C. Basal area increment (BAI) of the annual ring was calculated from the width data, and carbon isotope discrimination (Δ) was calculated using δ13C. The intercorrelations among BAI, Δ, and environmental variables were explored. The BAI was positively (p <0.001) correlated with atmospheric CO2 concentration ([CO2]), reflecting increased net photosynthesis with [CO2], whereas the negative correlations of BAI with either NO2 (p <0.05) or O3 (p <0.05) concentrations suggested that atmospheric pollution might have restricted tree growth to some degree. The Δ was positively correlated with both temperature (p <0.05) and [CO2] (p <0.001), and BAI was also positively correlated with Δ (p <0.001). However, precipitation was correlated with neither BAI nor Δ, 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.