Redwood trees scorched in the wildfire sprout new leaves from century-old buds

In a hopeful sign of nature’s resilience, the ancient redwoods of the California coast charred by a devastating wildfire in 2020 have sprouted new leaves. That redwoods can regenerate after a disturbance is well known. These sprouts, however, grew from buds that had been dormant under the bark for centuries. And the carbon deposits that fueled their regrowth are believed to be up to 100 years old, some of the oldest ever measured.

“It is likely that other long-lived trees also harbor carbon stores that are much larger than previously recognized,” he said. Drew Peltieran ecologist at Northern Arizona University and lead author of a new study on what made the redwoods possible to sprout new life in their blackened roots, trunks and branches. Older carbon stores in redwoods, trees dating back 1,500 years, may provide some hope for other older foliage that has been destroyed by disasters such as pest outbreaks, wildfires and hurricanes.

Peltier and team studied redwoods that were burned at Fire CZU Lightning Complex, which ignited in August 2020, tearing through large groves of majestic redwoods in Big Basin State Park, the oldest state park in California. The researchers’ findings about what allowed California redwoods to regenerate appear in the journal Nature: Plants.

In the well-understood natural process known as photosynthesis, plants and trees absorb carbon dioxide and water, which are converted into sugar and other carbohydrates when exposed to sunlight, triggering new tissue growth.

In the case of the burned redwoods at Big Basin State Park, “carbon synthesized from the atmosphere more than 50 years ago is being used as energy to grow new leaves in 2021,” Peltier said in an interview. “That’s a long time for the sugars to stick.”

Peltier, along with Northern Arizona University Professor of Biological Sciences George Koch and other colleagues, visited Big Basin State Park six times during the winter, spring and early summer of 2021 to investigate how long redwood tree carbon stores could be stored for future use. It’s an increasingly relevant question, with wildfires and other climate-related disasters threatening natural landscapes with increasing frequency.

“Trees can’t move, and global warming makes all of that worse, like drought and fire,” Peltier said.

Many redwoods and other trees in the park, such as Douglas firs, did not survive the CZU Lightning Complex fire, which started when a rare summer lightning storm sparked small flames carried by strong, dry winds. The fire burned a total of 86,509 acres in two Northern California counties.

To make the study possible, Melissa Enright, a research consultant with the US Forest Service, covered parts of 60 regrown trees with black plastic bags to block photosynthesis and ensure the tiny shoots were fed entirely from carbon stores. Northern Arizona University researchers then used radiocarbon dating to determine the age of this stored carbon.

Redwoods have evolved to be highly adaptable to fire, with thick, shaggy bark that keeps the flames at bay and protects the towering trees from the heat.

However, they are not fireproof, and even California coast redwoods that show signs of regeneration will likely never be the same. “These redwood trees just can’t regain that giant leaf canopy that they had before the fire for many years,” Peltier said. “So while the redwoods have survived, many things have also changed.”