Chemical and anatomical signals of past volcanic eruptions in tree–ring records from Northern Patagonia

We assessed anatomical and dendrochemical variations in Nothofagus pumilio annual tree–rings from Andean forests in Northern Patagonia following two VEI ≥ 3 eruptions of the Puyehue–Cordón Caulle Volcanic Complex in 1921–22 and 2011. White rings formed due to tephra–induced defoliation showed decreased or unchanged vessel lumen diameter, increased vessel density, increased fiber lumen diameter, and reduced fiber wall thickness, suggesting reduced structural resistance. Dendrochemical analysis revealed increased concentrations of Mg, Al, K, Ca, Ni, Ba, and Fe in 1921, and Mg, K, Ca, Mn, Cu, Zn, and Ba in 2011. While some elements retained in tree rings align with tephra composition, short–term leaching of soluble elements in tephra likely influenced their final distribution. Differences in chemical responses between eruptions are attributed to seasonal timing and tree phenology. We discuss the potential mechanisms of chemical element uptake and translocation in trees following tephra fall, highlighting the role of bark and roots in soil–plant interactions. These findings provide new insights into the dynamic interactions between trees and deposited tephra, as well as understanding the behavior of chemical elements absorbed in the short term. This information could be useful for the reconstruction of past volcanic eruptions and for understanding ecosystem responses to volcanic disturbances.