Natures wonders: how redwoods survive fire (Introduction)

by David Turell , Tuesday, December 05, 2023, 17:07 (352 days ago) @ David Turell

Preserved energy supports new buds:

https://www.science.org/content/article/ancient-redwoods-recover-fire-sprouting-1000-ye...

When lightning ignited fires around California’s Big Basin Redwoods State Park north of Santa Cruz in August 2020, the blaze spread quickly. Redwoods naturally resist burning, but this time flames shot through the canopies of 100-meter-tall trees, incinerating the needles. “It was shocking,” says Drew Peltier, a tree ecophysiologist at Northern Arizona University. “It really seemed like most of the trees were going to die.”

Yet many of them lived. In a paper published yesterday in Nature Plants, Peltier and his colleagues help explain why: The charred survivors, despite being defoliated, mobilized long-held energy reserves—sugars that had been made from sunlight decades earlier—and poured them into buds that had been lying dormant under the bark for centuries.

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Mild fires strike coastal redwood forests about every decade. The giant trees resist burning thanks to the bark, up to about 30 centimeters thick at the base, which contains tannic acids that retard flames. Their branches and needles are normally beyond the reach of flames that consume vegetation on the ground. But the fire in 2020 was so intense that even the uppermost branches of many trees burned and their ability to photosynthesize went up in smoke along with their pine needles.

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After 6 months, the team brought the sprouts back to the lab. There, they radiocarbon dated the molecules within to calculate the average age of those sugars. At 21 years, they are the oldest energy reserves shown to be used by trees. (A previous study had clocked 17 years in maples.)

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Based on the age and mass of the trees and their normal rate of photosynthesis, Peltier calculated that the redwoods were calling on carbohydrates photosynthesized nearly 6 decades ago—several hundred kilograms’ worth—to help the sprouts grow. “They allow these trees to be really fire-resilient because they have this big pool of old reserves to draw on,” Peltier says.

It's not just the energy reserves that are old. The sprouts were emerging from buds that began forming centuries ago. Redwoods and other tree species create budlike tissue that remains under the bark. Scientists can trace the paths of these buds, like a worm burrowing outward. In samples taken from a large redwood that had fallen after the fire, Peltier and colleagues found that many of the buds, some of which had sprouted, extended back as much as 1000 years. “That was really surprising for me,” Peltier says. “As far as I know, these are the oldest ones that have been documented.” (my bold)

Comment: As amazing as the age and size of redwoods is, this fire resistance is just as mind boggling. Other fir trees have similar survival techniques. Pines in the West are helped in their seed formation and dispersal by fires.