Variability of ray anatomy of Larix gmelinii along a forest productivity gradient in Siberia

Key message : This study provides new data and an alternative framework to the debate of tree carbon economy in a context of increasing stress. Abstract: For long-living trees, the resilience in times of stress is directly linked to the amount of accessible reserves. Despite the simplicity of this principle, the understanding of how carbon reserves limit growth and/or induce mortality under global change is still debated. In this study, we quantify how anatomical properties of rays—one of the main container for carbon reserves in tree stems—vary among sites, individuals, and annual rings of Larix gmelinii growing in contrasting sites in Siberia to verify if (1) the ray proportion and anatomical structure is linked to the environment, and/or (2) to changes in other wood tissues. Our observations have highlighted that ray proportion mainly varies among individuals, but little among sites and consecutive annual rings. We also observed that ray size and density scale to the wood structure with a relatively constant ratio of ~2.5 rays per tracheid, independent of site conditions. These results suggest that the functional connection between the anatomy of rays and tracheid is unaffected by environment and highlight the importance of considering allometric relations in ecological comparisons. Comparative studies of long-term trajectory of ray proportion of living and dead trees might unravel observed variability among individuals validating the link between long-term depleted reserves and mortality