Synchronizations of tree-ring δ¹⁸O time series within and between tree species and provinces in Korea: a case study using dominant tree species in high elevations

The current study was initiated to test the synchronizations of tree-ring δ¹⁸O (hereafter δ¹⁸O_TR) time series within and between tree species and provinces, which are about 144 km apart from each other in Korea. For the test, a 50-year δ¹⁸O_TR time series (1966–2015) was developed using four trees from each tree species which are Pinus densiflora and Quercus mongolica from Songnisan National Park and Taxus cuspidata, Pinus koraiensis, Abies koreana, and Quercus mongolica from Jirisan National Park. Their synchronizations were evaluated using t-value, Gleichläufigkeit (Glk), and Expressed Population Signal (EPS). The mean t-values and Glk scores within the tree species ranged 5.2–11.2 (p < 0.05) and 69–83%, and between the tree species ranged 6.1–13.2 (p < 0.05) and 73–81%, respectively. The mean t-value and Glk score between the regions were 4.3 (p < 0.05) and 72%, respectively. Furthermore, the EPS showed higher than 0.85, which is the generally accepted threshold value in dendrochronology, except for Q. mongolica at Songnisan National Park for which the value is 0.83 calculated by only two δ¹⁸O_TR time series. Based on the statistical results, we concluded that a δ¹⁸O_TR chronology established using more than four trees could serve as a promising reference for dating an undated wood without considering the tree species, as well as for research on climate in the past.