Temperature signal instability of tree-ring δ13C chronology in the northeastern Qinghai-Tibetan Plateau

Tree ring δ13C as a climate proxy is widely used for palaeoclimate research, however, its temporal stability response to the climate change remains unclear under more than one limited factors on tree growth. Here, we used a millennium tree-ring δ13C chronology combining two annual-resolution δ13C chronologies since 1800 from long-lived Qilian juniper (Sabina przewalskii) to assess its instability of the climate signal in the northeastern Qinghai-Tibetan Plateau. Tree-ring δ13C chronologies were strongly correlated with the regional mean April to August temperature from 1956 to 2008, but the associations were absent within the period 1901 to 1955 values in the CRU TS dataset. Comparison of the millennium-long δ13C series with reconstructed Asian temperatures also demonstrated that the δ13C chronology exhibited climate signal temporal instability. Substantial oscillations were revealed using a frequency-dependent analysis and 51-year running correlation analysis from the millennium-long tree-ring δ13C and δ18O series. Dual-isotope approach indicated that stomatal limitations created a statistical significant positive correlation between tree-ring δ13C and δ18O, but photosynthetic rate may be dominant when the correlations were not significant. Our results suggest that tree-ring δ13C series in the northeastern Qinghai-Tibetan Plateau is responded instability to temperature variations in the past 1000 years.