Sampling strategy and climatic implication of tree-ring cellulose oxygen isotopes of Hippophae tibetana and Abies georgei on the southeastern Tibetan Plateau

The tree-ring cellulose oxygen isotopes (δ ¹⁸ O) for four trees of Hippophae tibetana and four trees of Abies georgei growing in different locations around the terminal moraine in Xincuo from 1951 to 2010 were measured to explore its potential for reconstructing climatic variations in the southeastern Tibetan Plateau. The mean and standard deviation of tree-ring δ ¹⁸ O at different heights do not have significant differences, and there are no significant differences in the mean and standard deviation of tree-ring δ ¹⁸ O between trees near the brook and trees at the top of moraine, indicating that we can collect samples for tree-ring δ ¹⁸ O analysis regardless of sampling heights and that the micro-environment does not affect tree-ring δ ¹⁸ O significantly. The mean inter-series correlations of cellulose δ ¹⁸ O for A. georgei/H. tibetana are 0.84/0.93, and the correlation between δ ¹⁸ O for A. georgei and H. tibetana is 0.92. The good coherence between inter-tree and inter-species cellulose δ ¹⁸ O demonstrates the possibility of using different species to develop a long chronology. Correlation analysis between tree-ring δ ¹⁸ O and climate parameters revealed that δ ¹⁸ O for A. georgei/H. tibetana had negative correlations (r = −0.62/r = −0.69) with relative humidity in July–August, and spatial correlation revealed that δ ¹⁸ O for A. georgei/H. tibetana reflected the regional Standardized Precipitation Evapotranspiration Index (29°–32° N, 88°–98° E). In addition, tree-ring δ ¹⁸ O in Xincuo has a significant correlation with tree-ring δ ¹⁸ O in Bhutan. The results indicate that cellulose δ ¹⁸ O for A. georgei and H. tibetana in Xincuo is a good proxy for the regional hydroclimate.