Pyrolysis-Derived Tree-Ring Stable Carbon Isotope Data Provide Reliable Records for Polar Paleoclimate

Tree-ring cellulose stable isotopes (δ¹⁸O and δ¹³C) are high-resolution proxies for reconstructing past climate variability. However, measuring carbon and oxygen isotopes separately requires substantial sample material and is time-consuming and costly.

Here, using subfossil and living wood from the southern Yamal Peninsula, Russia, we extracted α-cellulose with a plate-based method and evaluated the reliability of pyrolysis-derived cellulose δ¹³C (1350°C) using paired measurements against conventional combustion (1020°C; n = 954).

The two δ¹³C datasets were strongly correlated (r = 0.96). Pyrolysis-derived δ¹³C showed slightly reduced variance, along with a stable proportional bias and a small mean offset (+0.17‰). No systematic drift with run order was detected. After constructing multicore mean chronologies, the two δ¹³C chronologies showed nearly identical interannual variability (r = 0.99) and consistently captured a dominant June-August temperature signal. Moreover, δ¹³C variations in subfossil wood closely tracked those in living trees, and preservation state did not increase the inter-method offset.

Overall, under the analytical conditions applied here, pyrolysis-derived δ¹³C is suitable for chronology development and climate signal extraction, providing an efficient and reproducible basis for constructing dual-isotope tree-ring chronologies.