Controlled burn near Earth’s largest tree cancelled

A visitor sizes up the General Sherman Tree, the world’s largest living thing, in California’s Sequoia National Park in 2002.

LOS ANGELES – A National Park Service plan to set fire to an ancient sequoia grove in western Sierra Nevada has been canceled for the second time this year, further delaying a delicate forestry operation aimed at triggering new growth near the world’s largest tree.

The controlled burn in Sequoia and Kings Canyon national parks was expected to blacken 483 acres in the Giant Forest, a cathedral-like grove of sequoias straddling Generals Highway. The carefully tended fire was expected to last seven days, but was canceled Friday after a test fire failed to consume vegetation fast enough for the plan to work, according to Mike Theune, a fire information officer with the National Park Service.

California’s famed General Sherman Tree and other giant sequoias have evolved in a manner that allows them to not only survive periodic wildfires, but also thrive in their aftermath. The towering are wrapped in a thick, fireresistant bark, and their pine cones release seeds when exposed to heat. Fire also helps to clear the forest floor and expose nutrients that allow the fallen seeds to germinate.

Since the 1960s, the National Forest Service has used intentionally set fires to foster new growth of giant sequoias. Before conducting a controlled burn, however, operation managers have to consider the moisture content of the vegetation that will burn, wind conditions and the chance that firefighters might be called to help out on wildfires elsewhere in the state, Theune said.

Although vegetation appeared to be dry enough for a controlled burn during the planning stage, a test fire on Friday did not burn as intensely as officials hoped, Theune said.

Accelerating the controlled burn with drip torches – devices that drop burning diesel fuel and gasoline onto dry brush – would have been too dangerous for firefighters and would have increased the risk of the fire getting out of control, Theune said. The goal is to have a moderately burning fire that clears overgrowth and makes room for the next generation of plant life, among other things.

“The reason we don’t try to force it and use more firefighters with drip torches is it comes back to safety,” Theune said. “Are we going to put firefighters at risk? It’s your return on investment. What is going to give us the best outcome that’s not only safe for our crews but also what is healthiest for the forest?”

The Park Service will monitor conditions going forward to determine when they can launch the prescribed fire for the Giant Forest. No timetable was immediately set, officials said Sunday.

Sequoia and Kings Canyon officials deliberately burn between 1,100 and 1,500 acres of forestland annually to manage forest health. But one of its other benefits – mitigating wildfires – has taken on greater importance as California experiences a surge and deadly and destructive blazes.

Not all federal lands are suited for prescribed burns, Theune said. Some landscapes might be too rugged to manage safely and others are too overgrown so officials have to wait for Mother Nature to take the lead.

The Giant Forest has been under a prescribed fire regimen for decades. So, even though officials have had to cancel burns twice this year, it’s not as bad as some areas and can be revisited at a future date, Theune said. Assigning a never-before-treated area for a controlled burn can take years because it has to be surveyed for relevant infrastructure and archaeological or historical artifacts as well as environmental impacts, funding, weather and logistics.