Scientists in northern Scandinavia have uncovered remarkable insights into historical climate secrets, including the impacts of volcanic eruptions, by studying the “blue rings” in pine trees and juniper shrubs. These unique tree rings form during exceptionally cold summers, often caused by volcanic activity, when the growth season is too short for proper lignification of cell walls.
The research identified blue rings linked to two particularly cold summers, in 1902 and 1877, potentially caused by volcanic eruptions. Mount Pelée in Martinique erupted in May 1902, while Cotopaxi in Ecuador erupted in late June 1877. These eruptions likely caused atmospheric cooling, impacting tree growth in the region.
Dr. Agata Buchwal, lead author from Adam Mickiewicz University, explained, “Blue rings look like unfinished growth rings and are associated with cold conditions during the growing season.” The study revealed that pine trees, more vulnerable to cold summers than juniper shrubs, are effective indicators of past climatic events.
Researchers sampled cores from 25 Scots pine trees and stem-base discs from 54 juniper shrubs at the treeline of Mount Iškoras in northern Norway. Blue rings were most prevalent in 1902, with 96% of pine trees and 68% of shrubs showing evidence of cold-induced stress. In 1877, the blue rings appeared in 84% of pine trees and 36% of shrubs.
These findings not only shed light on past volcanic cooling events but also highlight the need for further research to establish a global “blue ring network” to reconstruct historical climate changes. “We hope to inspire other research groups to explore blue rings in their material,” Dr. Buchwal added.
Understanding how trees respond to extreme climatic conditions offers valuable lessons about environmental resilience and the far-reaching impact of volcanic activity.
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