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 (δ18 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 δ18 O at different heights do not have significant differences, and there are no significant differences in the mean and standard deviation of tree-ring δ18 O between trees near the brook and trees at the top of moraine, indicating that we can collect samples for tree-ring δ18 O analysis regardless of sampling heights and that the micro-environment does not affect tree-ring δ18 O significantly. The mean inter-series correlations of cellulose δ18 O for A. georgei/H. tibetana are 0.84/0.93, and the correlation between δ18 O for A. georgei and H. tibetana is 0.92. The good coherence between inter-tree and inter-species cellulose δ18 O demonstrates the possibility of using different species to develop a long chronology. Correlation analysis between tree-ring δ18 O and climate parameters revealed that δ18 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 δ18 O for A. georgei/H. tibetana reflected the regional Standardized Precipitation Evapotranspiration Index (29°-32° N, 88°-98° E). In addition, tree-ring δ18 O in Xincuo has a significant correlation with tree-ring δ18 O in Bhutan. The results indicate that cellulose δ18 O for A. georgei and H. tibetana in Xincuo is a good proxy for the regional hydroclimate.