Redwoods are sprouting 1000-year-old buds

When lightning ignited fires in California’s Big Basin Redwoods State Park north of Santa Cruz in August 2020, the fire spread quickly. Redwoods naturally resist burning, but these fires reached the canopies of trees over 300 feet tall. “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, according to a report in Science magazine, and in a paper published in Nature Plants, Peltier and his colleagues explain why:  The burned trees, despite losing their needles, mobilized their long-held energy reserves, the sugars that were produced from sunlight decades ago. The trees routed this energy into dormant buds under the bark.

“This is one of those papers that challenge our previous knowledge on tree growth,” says Adrian Rocha, an ecosystem ecologist at the University of Notre Dame. “It is amazing to learn that carbon taken up decades ago can be used to sustain its growth into the future.”

When the wildfires in 2020 burned through Big Basin Redwoods State Park, reported the San Francisco Chronicle, they left some of the oldest trees on the planet badly burned; researchers now have estimates of  just how old the energy reserves of those redwoods are. Researchers studying a stand of severely burned old-growth redwoods found the buds were more than 1,000 years old.

Mild fires burn through coastal redwood forests about every decade, and the giant trees resist flames in part because the bark is up to a foot thick on the lower trunks, and it contains tannic acids that are fire-resistant. But in 2020 even the uppermost branches of many trees burned and their ability to photosynthesize went up in smoke along with their needles. Giant sequoias — which are different from the redwoods — can live for up to 3000 years, but in 2020 about 10 to 14 percent of the giant sequoias in the Sierra Nevada that were at least four feet in diameter were killed in the Castle Fire on the Sequoia National Forest.

A single sprout pushing up through thick redwood bark in Big Basin Redwoods State Park, as seen in April 2021.

Courtesy of Drew Peltier/Northern Arizona University 2021

A sprout emerges from thick redwood bark in Big Basin Redwoods State Park — 2021 photo by Drew Peltier, Northern Arizona University

Fire managers weren’t sure the trees on the Sequoia and in Big Basin would make it, but visiting the state park a few months after the fires, Peltier and his colleagues found fresh growth emerging from the trunks of blackened redwoods. They knew that shorter-lived trees can store sugars for several years. Because redwoods can live for more than 2000 years, the researchers wondered whether the trees were drawing on much older energy reserves to grow these new sprouts.

Within about 5 months, ancient trees had mobilized old stores of carbohydrate to resprout.LISSY ENRIGHT/U.S. FOREST SERVICE
Within about 5 months, ancient trees had mobilized their old stores of carbohydrate to resprout. LISSY ENRIGHT/USFS photo

Melissa Enright with the USFS covered parts of 60 blackened tree trunks with black plastic to block out sunlight, ensuring that any new sprouts would grow with only stored energy, not new sugars produced from current photosynthesis. After 6 months, the team brought some sprouts back to the lab, and they radiocarbon-dated them to calculate the age of those sugars. At 21 years, they are the oldest energy reserves shown to be used by trees.  But the mix of carbohydrates contained some carbon that was much older, and Peltier calculated that the redwoods’ carbohydrates were photosynthesized nearly 6 decades ago.

“They allow these trees to be really fire-resilient because they have this big pool of old reserves to draw on,” Peltier says. These redwoods have formed new sprouts, but Peltier and other forest researchers wonder how the trees will cope with far less energy from photosynthesis, considering that it will be many years before the trees can grow as many needles as they had before.

“It is likely that other long-lived trees also harbor carbon reserves that are much older than previously recognized,” said Peltier. The carbon stores observed in the trees, he told a Forbes reporter, date back as far as 1500 years, and they may provide hope for other ancient trees “destroyed” by fire.

Enviros sue Park Service over planting sequoias

The National Park Service plans to replant sequoia groves in Sequoia and Kings Canyon National Parks, where fires in 2020 and 2021 caused lasting damage to sequoia groves on federal land, but environmentalist groups in California say it would set a legal precedent and be a huge mistake.

Four groups filed suit against the NPS on November 17, saying the agency’s efforts violate the law, because designated wilderness areas prohibit human involvement in the ecosystem — even if it includes planting trees.

Three fires in two years that killed giant sequoia trees. The darker green areas represent groves of giant sequoias.
Three fires in two years that killed giant sequoia trees. The darker green areas represent groves of giant sequoias.

Surveys of sequoias on NPS land found that in 2020 and 2021, almost 20 percent of all giant sequoias in their natural range that were over 4 feet in diameter or more were killed by fire (and neglect) or were expected to die in the next few years. In 2020, surveyors estimated that 10 to 14 percent of the entire Sierra Nevada population of giant sequoias over 4 feet in diameter were killed in the Castle Fire. The following year, the KNP Complex and the Windy Fire burned between 2200 and 3600 sequoias over 4 feet in diameter; those sequoias were killed or are expected to die within 5 years.

CBS News reported on the project a year ago:

The NPS announced the seedling-planting project and said it was “concerned that natural regeneration may not be sufficient to support self-sustaining groves into the future, particularly as the fires killed an unprecedented number of reproductive sequoia trees in the groves themselves.”

Chad Hanson, director of the John Muir Project, one of the groups that is suing, disputes that conclusion. Sequoias actually “depend on high-intensity fire in order to reproduce effectively,” Hanson told CNN. “Nature doesn’t need our help. We are not supposed to be getting involved with tending it like a garden.”

Advocates at Wilderness Watch, Sequoia Forest Keeper, and the Tule River Conservancy first sued the NPS in September to stop a separate project by the agency to cut and burn trees in the same designated wilderness areas, cutting on about 1000 acres of forest land and designating 20,000 additional acres as available to “manager-ignited fires and associated activity,” according to the complaint.

“Recently burned groves are RESTORING THEMSELVES — as they have done for more than one hundred centuries!”  according to the Sequoia Portal, whose mission is to add existing roadless areas of the Sequoia National Park, National Forest, and National Monument to the National Wilderness Preservation System. “Millions of sequoia seedlings carpet these burned groves,” says the Portal. “Do they think the public is stupid enough to think that any agency can replace full-grown 3200-year-old red barked sequoias? ALL the iconic ancient giants started as tiny seedlings, and they are already growing — immediately seeded by their scorched giant sequoia parents! As it has always been in the groves. And the majority of the largest giants are NOT DEAD.”

The John Muir Project, a nonprofit focused on protecting federal forests, joined the lawsuit on November 17, amending it to include the sequoia replanting project as part of the complaint. The groups now jointly accuse the NPS of illegally encroaching on federally protected land in both of the projects.

Firefighter on the Windy Fire applies water on a burning giant sequoia tree. Photo uploaded to InciWeb Oct. 11, 2021.
Firefighter on the 2021 Windy Fire applies water on a burning giant sequoia.  InciWeb photo

The complaint in U.S. District Court in Fresno is an addendum to a suit filed earlier this year that challenged the NPS for other work in wilderness areas of Sequoia & Kings Canyon National Parks. Besides planting seedlings, NPS crews have been thinning and burning around sequoia groves to reduce wildfire risk, according to the San Francisco Chronicle.

Both the fire-prevention work and the tree-replanting project followed in the aftermath of fires that wiped out unprecedented numbers of sequoias.

NPS staff declined to comment on the lawsuit, but confirmed that replanting had already begun in two sequoia groves back in mid-October, before the latter complaint was filed.

“The Park Service has to abide by the 1964 Wilderness Act,” said Kevin Proescholdt, conservation director at Wilderness Watch. “We should still allow these natural ecosystems to respond as they want to the changes brought about by the changing climate. The more that agencies will allow natural fire to burn and perform its role, the better these wilderness forests will be,” he said.

The groups claim the projects were approved after required processes of environmental review and public engagement were circumvented by declaring they were “emergency” projects that would not have to meet those requirements.

The NPS said in its project announcement it would replant only in areas that field surveys showed insufficient natural regeneration to successfully re-establish, as they would if they hadn’t experienced severe fire effects in recent fires.