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Do trees' water-use strategies intensify droughts? In this study two traits stuck out: maximum leaf gas exchange rate and water transport. The first trait is the rate at which leaves can pump water vapor into the air. The second describes how much water the tree can move to the leaves. The results showed that in cool regions, plants and trees slowed down their water use in response to declining soil moisture. But in hot climates, some plants and trees with high water transport and leaf gas exchange rates cranked up the AC, so to speak, when the soil got dry, losing more and more water in an effort to carry out photosynthesis and stay cool while depleting the soil moisture that was left.
New research findings led by University of Utah biologists William Anderegg, Anna Trugman and David Bowling has been published in Proceedings of the National Academy of Sciences.
"We show that the actual physiology of the plants matters," Anderegg says. "How trees take up, transport and evaporate water can influence societally important extreme events, like severe droughts, that can affect people and cities."
Anderegg studies how tree traits affect how well forests can handle hot and dry conditions. Some plants and trees, he’s found, possess an internal plumbing system that slows down the movement of water, helping the plants to minimize water loss when it’s hot and dry. But other plants have a system more suited for transporting large quantities of water vapor into the air—larger openings on leaves, more capacity to move water within the organism. Anderegg’s past work has looked at how those traits determine how well trees and forests can weather droughts. But this study asks a different question: How do those traits affect the drought itself?
It’s true that hot and dry regions tend to have more plants and trees that are adapted to dry conditions. But regardless of the climate some species with water-intensive traits, such as oaks in a Mediterranean climate, can still exacerbate a drought.
It’s true that hot and dry regions tend to have more plants and trees that are adapted to dry conditions. But regardless of the climate some species with water-intensive traits, such as oaks in a Mediterranean climate, can still exacerbate a drought.
Anderegg says that understanding the relationship between a tree’s traits and drought conditions helps climate scientists and local leaders to plan for future drought effects on communities.
“Failing to account for this key physiology of plants would give us less accurate predictions for what climate change is going to mean for drought in a lot of regions,” he says.
How trees affect the weather. University of Utah. Proceedings of the National Academy of Sciences. Unpublished as yet; doi;10.1073/pnas.1904747116
Further reading; https://unews.utah.edu/which-trees-face-death-in-drought/