Impacts of climate and tree morphology on tree-ring stable isotopes in central Mongolia.

This article focuses on the analysis of stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotopes in tree rings of Siberian Pine (Pinus sibirica Du Tour) from a xeric site in central Mongolia (Khorgo Lava) to investigate past climate variability and tree physiological responses over the last 182 years. The study finds that tree-ring δ¹³C and δ¹⁸O reflect summer hydroclimatic variability and capture recent extreme droughts, with δ¹⁸O also sensitive to spring temperatures, thereby complementing traditional ring-width climate reconstructions. Trees exhibiting partial cambial dieback ('strip-bark morphology') show increasing long-term trends in ring-width, δ¹³C (and intrinsic water-use efficiency, iWUE), and δ¹⁸O relative to trees with full cambium ('whole-bark morphology'), suggesting that stem morphological changes may influence leaf-level physiological behavior and gas exchange. The findings highlight the potential of stable isotopes to broaden paleoclimate reconstructions in north-central Asia but emphasize the need for further research on how stem morphology affects isotopic trends and their implications for climate studies.