What is it about?
Trees can usually cope with heat if they have enough water, but drought limits their ability to cool. In our five-year experiment with European beech and downy oak, we manipulated temperature and water separately to see how leaves respond. We found that when heat and drought occur together, leaves overheat and scorch, especially in beech, revealing a key risk for forests under climate change.
Featured Image
Photo by Julia Weihe on Unsplash
Why is it important?
Our study is the first to show experimentally that when tree leaves get hotter than their safe temperature limits, they can develop permanent scorching, a negative effect that's much worse when the trees also face drought. This means that Central European forests, especially beech-dominated ones, could be at greater risk as hot and dry spells become more common.
Perspectives
I loved working on this study because of its elegant design: we measured trees after five years in open-top chambers, where they were exposed to heat and/or drought. This setup let us isolate the effects of each stressor and observe long-term responses in our trees. Also, the new cameras we used could track leaf temperature and visible scorching at high frequency, which allowed us to capture the first direct connection between leaves exceeding their thermal limits and actual damage. Seeing those scorching events unfold in real time was really exciting.
Alyssa Kullberg
Swiss Federal Institute for Forest, Snow and Landscape Research
Read the Original
This page is a summary of: Hydraulic stress limits thermal acclimation in trees under chronic drought, Proceedings of the National Academy of Sciences, April 2026, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2531865123.
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