Speaker
Description
Laser ablation isotope ratio mass spectrometry (LA-IRMS) offers a unique tool for investigating changes in the stable isotope composition of organic materials at a very high resolution. Stable isotope compositions of carbon (δ13C) and oxygen (δ18O) are well-established proxies in ecophysiological research as these elements connect plant and animal tissue to changes in environmental conditions. A novel LA-IRMS method (“laser pyrolysis”) for analysing δ18O in tree rings was established at the Stable Isotope Laboratory of Luke in 2025 (Sahlstedt et al. 2025), enabling isotope measurements at a spatial resolution of 100 µm. Here we show that the method allows simultaneous analysis of δ18O and δ13C and can be applied at an even higher resolution of 50 µm. The δ13C data produced by laser pyrolysis-IRMS and the more conventional combustion-based LA-IRMS are highly comparable (r=0.97, n=18 for annual mean tree-ring δ13C; r=0.87, n=96 for intra-annual tree-ring δ13C), showing that both δ18O and δ13C can be confidently analysed by the novel laser pyrolysis-IRMS method. At this sampling resolution, it is possible to analyse features related to, for example, extreme environmental conditions such as drought or frost events which cause small disturbances in wood anatomy. Isotopic analyses of these features can reveal important information on plant physiological responses, crucial to understanding tree responses to environmental stressors. Similarly, small samples, such as shrubs, become accessible for stable isotope research and allow isotopic tools to be used in investigating key environments in the northern latitudes.
Sahlstedt, E.K., Loader, N.J. and Rinne-Garmston, K.T. 2025. Analysis of 18O/16O Isotope Ratios in Organic Matter by Laser Ablation IRMS. Analytical Chemistry, DOI: 10.1021/acs.analchem.4c06896
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