Negligible local-factor influences on tree ring cellulose δ¹⁸O of Qilian juniper in the Animaqing Mountains of the eastern Tibetan Plateau

Tree ring cellulose oxygen isotopes (δ¹⁸O) were measured on 21 trees of Qilian juniper from the Animaqing Mountains, Tibetan Plateau, to investigate intra- and inter-tree variability, potential juvenile and elevation effects and climatic implications. There are no significant differences in mean and standard deviation of tree ring δ¹⁸O values at different heights in individual trees. Tree ring δ¹⁸O values from different directions show a high degree of coherence. The mean and standard deviation for vertical and circumferential δ¹⁸O time series are very similar, and δ¹⁸O data from different heights and directions are highly correlated (r > 0.88). The δ¹⁸O values of young trees are lower than those of old trees in the first 10 years of tree growth. Tree ring δ¹⁸O data from five different altitudes are highly correlated (r > 0.88) and share similar climatic signals. As such, an altitude effect on tree ring δ¹⁸O is not observed. Our results indicate that samples from one site, regardless of sampling height, direction or altitude, can be used to reconstruct a long-term δ¹⁸O record. Tree ring δ¹⁸O data from the Animaqing Mountains show a significant negative correlation (r = −0.67; p < 0.001) with May–July regional precipitation and appear to be a promising proxy for precipitation reconstruction.