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The Cardinal Edge

Program/Event

Arts and Research Showcase 2025

Abstract

As the polar jet stream’s activity transforms under climate change’s influence, short-term, or ephemeral, cooling events could become more frequent. Understanding how such cooling events may affect forest dynamics and tree-growth can allow us to predict how the morphing jet stream may reflect in our future forests. “Blue rings” (BRs) have presented themselves as subsections of annual rings, made clear through the double-staining of microsections of wood, which have been associated with the interruption of conifers’ lignification process. Such features could allow us to peer back into pre-instrumental records and assess how a tree’s growth and their surrounding canopy may be affected by ephemeral cooling events, while also gaining and understanding of such event’s historic frequency. This study explores the discrete feature of BRs, their presentation, and efficacy as proxies for cooling events within a section of a millennium-length, dendrochronological record of Engelmann spruce from the Greater Yellowstone Ecoregion. Using quantitative wood anatomy (QWA) methods, we compare qualitatively the appearance of BRs in the understudied Engelmann spruce to their appearance in whitebark pine, a species that belongs to the more studied Pinus genus. Comparison showing that BRs in whitebark pine resemble the titular coloring more than those belonging to the Engelmann spruce, which appear more magenta and thinner. Following their characterization, we examine statistically their use as proxies for volcanic or meteorological cooling events using the Smithsonian’s volcanic records along with reconstructed SO4 flux records and August TMAX records, finding that BRs are more often associated with meteorological events than volcanic.

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