What is it about?

Understanding how plant function changes during dehydration is vitally important to improve predictions of the composition, productivity, and resilience of woodland and forest communities under future climate conditions. Our study examines embolism (air blockages) in the internal water transport network of oaks, one of the Northern Hemisphere’s most ecologically and economically important angiosperm genera. We ask whether avoiding embolism is a key component of drought tolerance in oaks. We use a novel, non-invasive optical technique to capture the process of embolism in more than twenty species of oaks.

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Why is it important?

Our results indicate that western North American oaks show an evolutionary increase in drought resistance which has enabled them to colonize more arid areas and to develop what are, for now, relatively comfortable safety margins to cope with climate change. Our results show that oaks have evolved to avoid embolism, and that this damaging process only occurs under conditions of extreme drought stress.

Perspectives

Although embolism is reported to be a highly damaging process that occurs in plants under water stress, there is much debate about how frequently plants experience it under natural conditions. Our study demonstrates that evolved relationships between traits and climate in oaks ensure that these trees and shrubs currently avoid embolism, even under dry years. These results indicate just how important it is for these trees and shrubs to avoid certain critical water level thresholds during dry periods to maintain function. Surpassing these thresholds of damage may be one way in which future climate change may have catastrophic impacts on economically important trees.

Robert Skelton
South African Environmental Observation Network

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This page is a summary of: Evolutionary relationships between drought-related traits and climate shape large hydraulic safety margins in western North American oaks, Proceedings of the National Academy of Sciences, March 2021, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2008987118.
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