Warming temperatures are hindering the ability of the world’s oldest trees, California redwoods, to perform essential functions. Redwood leaves “exhibit significant decreases in photosynthesis and carbon uptake” at higher temperatures, said a study published in the journal JGR Biogeosciences.
Leaves contain pores called stomata, which take carbon dioxide in and let water out. When the stomata are open, the tree is “breathing” and photosynthesizing. When they’re closed, the tree is conserving water but not photosynthesizing. When it’s hot, stomata tend to open to release water, essentially sweating.
However, during heat waves, “coast redwoods hit a point where they can’t cool down fast enough, and they just keep their stomata closed,” said Vox. It conserves water, but it also means the “tree isn’t taking in more carbon,” therefore not “‘eating’ or building up energy stores it can use to keep growing.” Redwoods, accustomed to temperatures of 59 degrees Fahrenheit, are now facing temperatures topping 86 degrees.
Slowed photosynthesis could have a “big impact” on redwood forests, “creating a vicious cycle where trees don’t have enough carbon stored to replenish their leaves in the future,” said Vox. There could be larger environmental implications too, as redwood forests “store more carbon dioxide per acre than any other forest in the world.”
Heat waves also “burn off the coastal fog that redwoods depend on for much of their water,” the University of California, Davis, said in a release about the study. This research is an “important start” for figuring out what “parts of the redwood range are at risk” and “trying to intervene,” said study author Lily Klinek.
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