“Historically,” the LA Times explains, “giant sequoias have been armored against fire — even dependent on it, said Robert York, an adjunct professor of forestry at UC Berkeley who has been studying the rare species for 18 years.” But these fires, York specifies, must be low-severity fires.
The faster, more intense fires created by a warming climate are a threat to giant sequoia trees. As NPR reports: “Sequoias need fire, but fires are changing.”
“In some groves, researchers are finding hundreds of seedlings where the Castle Fire burned with low-intensity, the kind of fire sequoias are accustomed to.
But in the Alder Creek grove, where the fire burned with ferocious heat, the team only finds a dozen seedlings the entire afternoon. Other groves look similarly bare.”
Even under normal conditions, around 98% of sequoia seedlings die in their first year. This year could be even tougher with extreme drought gripping the landscape.”
In a balanced climate, the planet’s largest and oldest trees have used fire to help them reproduce for thousands of years. This clip from Nature on PBS shares how this destructive force can bring for new life. Some background from nps.gov:
In the early 1960s, Dr. Richard Hartesveldt explored the connection between fire and sequoia regeneration. His small-scale prescribed fires followed nearly a century of fire suppression, and resulted in the germination of sequoia seeds and the recruitment of sequoia seedlings – something that had not occurred in the absence of fire.
Since those first experiments, researchers have further shown the benefits to sequoias from fire. Dendrochronology has determined that low intensity surface fires swept through the big trees approximately every 5 to 15 years. Sequoias rely on fire to release most seeds from their cones, to expose bare mineral soil in which seedlings can take root, to recycle nutrients into the soil, and to open holes in the forest canopy through which sunlight can reach young seedlings.
But fire is also just one of the ways that Sequoias can grow. Their cones can also open from the sun’s heat or seeds can also scatter after a cone dries out, sometimes with some help. More from the National Park Service:
“…Seeds may be distributed from tree-top level as the cones either open upon browning or are eaten by chickarees on the limbs of the crown; or, the cones may be cut or otherwise fall to the ground, where they dry out and spill their seeds upon a relatively small area of the soil or leaf litter surface. Each has advantages and disadvantages. A very important point here is that a high percentage of sequoia seed is dispersed by the activities of animals.”
Related reading: Differences between giant sequoia and redwood and the science of Fire Ecology.
And in 2021 news: A Single Fire Killed Thousands Of Sequoias. Scientists Are Racing To Save The Rest, World’s largest trees under siege from California wildfire as sequoias face new perils, and ‘Mind-blowing’: tenth of world’s giant sequoias may have been destroyed by a single fire.In the TKSST video archives:
• How do firefighters combat and control wildfires?
• How do fires spread? Solving the mysteries of firebrands
• How scientists climb and measure redwood giants.
• Each Tree Is Its Own Adventure: Climbing giant sequoias for science
2021 Update: This post has been amended with more recent resources and information.
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