Oxygen isotope ratios of subalpine conifers in Jirisan National Park, Korea and their dendroclimatic potential

The present study aimed to explore the dendroclimatic potential of three conifer species, viz. Taxus cuspidata, Abies koreana, and Pinus koraiensis, in the subalpine zone in the Republic of Korea. The tree-ring δ¹⁸O chronologies were analyzed for the last 50 years and were found to be well correlated with one another (r = 0.70 – 0.87). In the correlation analyses with temperature in the growing season, the tree-ring δ¹⁸O data of Abies / Taxus / Pinus showed positive correlation coefficients significantly with April, June, and July / April and July / April. On the other hand, in the correlation analyses with precipitation, only the tree-ring δ¹⁸O data of Abies and Taxus showed negative correlation coefficients significantly with April and May, respectively. For the correlation analyses with relative humidity, only the tree-ring δ¹⁸O data of Abies and Taxus showed significant negative correlation coefficients with April, June, and July for Abies, and with June and July for Taxus. Based on the results, we developed an extended Taxus δ¹⁸O chronology back till 1864 CE (152 years). Spatial correlation analyses revealed that the Taxus δ¹⁸O was mainly influenced by precipitation in the upstream regions of western Japan rather than that in the study region. This result pointed out the importance of the upstream hydrological processes that govern δ¹⁸O in precipitation. In addition, the TC δ¹⁸O showed meaningful correlations with temperature over Korea including our study region. These results indicated that the tree-ring δ¹⁸O of southern Korea was controlled not only by local temperature, but also by the upstream moisture conditions of western Japan.