Drought signals in tree-ring stable oxygen isotope series of Qilian juniper from the arid northeastern Tibetan Plateau

• Tree-ring δ18O variations show high correlations with regional droughts.
• δ18O variations in juniper wood explain 38% of Tibetan plateau drought variability.
• δ18O series from individual trees are highly correlated despite different means.
• Tree-ring δ18O and Indian Ocean sea surface temperatures are negatively correlated.
• The northern and southern Tibetan plateaus show opposite moisture variations.

For the mechanistic understanding of hydroclimate variability, stable oxygen isotopic ratios (δ18O) of tree-ring α-cellulose can play a key role in paleoclimatic research. On the north-east Tibetan Plateau (TP), a region particularly sensitive to climate change, there exists a distinct lack of δ18O research in tree-ring archives. The few currently existing tree-ring δ18O chronologies were obtained by pooling the wood material from the same year from different trees prior to preparation and analysis. Although this method is time and cost efficient, it might impede the analysis of changes within the internal variability of oxygen isotope signals and a deeper understanding of the resulting climate reconstruction. We selected five Qilian juniper (Sabina przewalskii Kom.) trees covering the period 1951–2011 on the north-east TP to investigate the climate signals contained in stable oxygen isotopic composition records obtained using single tree analysis. Although the inter-series correlation between the five individual δ18O series indicates a highly significant relationship (mean r = 0.59, n = 59, p = 0.01), the five individual δ18O series show significantly differently mean values. We found significant negative correlations between drought/hydroclimatically triggered climate parameters (PDSI, precipitation) and each of the individual δ18O series. Spatial correlation maps indicate negative correlation of tree-ring δ18O and Indian Ocean sea surface temperatures, and inverse correlation patters of moisture conditions on the northern and southern TP. Our results provide a reference for future research on stable oxygen isotope/climate signals in the species S. przewalskii Kom..