Non-pooled oak (Quercus spp.) stable isotopes reveal enhanced climate sensitivity compared to ring widths

Multi-centennial- to millennial-long oak (Quercus spp.) tree-ring width (TRW) chronologies from living and relict wood are frequently used for climate reconstructions, but the amount of explained hydroclimatic variation remains relatively small. Although stable carbon and oxygen isotopic ratios (δ13C and δ18O values) in tree rings may offer enhanced climate sensitivity, our understanding of their paleoclimatic sensitivity is still limited by the general lack of well-replicated and high-resolution datasets. Here, we assessed the temperature, precipitation, and drought signal of annual δ13C and δ18O values and TRW measurements from 21 oaks growing under different ecological settings in the Czech Republic. Compared to the overall low climate sensitivity of TRW, the δ13C and δ18O chronologies revealed significant positive and negative correlations with March-August mean temperature and hydroclimate (for the period 1901-2018), respectively. Additional tests on the effect of sample size demonstrated robust climate sensitivity of the isotopic chronologies when non-pooled alpha cellulose from the latewood of at least 6 individual oaks was used. Our study suggests that oak stable isotopes are possibly the best high-resolution paleoclimatic proxy for the Central European lowlands, as well as any other temperate habitat where oak wood has historically been used as construction timber, and where traditional tree-ring parameters, such as TRW, tend to fail.