Why do sequoia trees need fire

The ever-increasing intensity of fires in California has become too much even for the sequoias, which evolved to survive — even thrive — in fires. The dangers prompted firefighters last week to wrap General Sherman, believed to be the largest tree in the world, in flame-retardant foil in a bid to save it from flames. Experts say the fires that sequoias endured for centuries were mostly low grade.

Thick bark and sky-high crowns protected the trees from serious damage. Heat from the flames even helped them reproduce by releasing seeds from their cones. Drought and rising temperatures have killed other plants and turned them into kindling.

Some of the trees, which grow only in California, were charred from their trunk to their crown. One century of missed reproduction is not enough to threaten the future of these long-lived trees. But it remains a high priority to sustain frequent enough fire in these forests to produce many young sequoias and to reduce fuels, helping these groves be more resilient to the impacts of a warming climate and high-severity wildfire. Enough young trees must survive the challenges of insects, disease, drought, and occasional fire to become the monarch giant sequoias for future generations to enjoy.

Even as fire gives birth to the next generation of sequoias, it can also play a role in the death of a big tree. Many large trees will eventually die by falling, triggered by wind or heavy snow, and often weakened by basal caverns from centuries of fire. Recently, large giant sequoias are also dying in large numbers from high-severity wildfire. See the section below on impacts from the Castle Fire on park sequoia groves. Firefighting teams worked actively to contain the fire, however, a combination of fuels, topography, and weather resulted in high fire severity in some areas.

Hazardous and smoky conditions hampered fire control efforts, and many fires burning at once across the state competed for fire-fighting resources.

While assessment of fire impacts is still underway, we know that the fire burned 12 giant sequoia groves in the park, with differing levels of fire severity depending on their fire history and location. Groves on warmer and drier south-facing slopes, and with no recent fire, sustained extensive mortality of large giant sequoias over four feet, or 1.

Examples include Homer's Nose and Board Camp groves. Other groves, growing on cooler, more moist north-facing slopes or having recent history of fire had more mixed and moderate fire severity or limited fire spread. One example is the Garfield Grove, where managers did a prescribed burn in About half of the sequoia grove area in the Castle Fire burned at low severity or had no detectable change. About half burned at moderate or high severity. In the park grove areas that burned at high severity, we currently estimate that at least large sequoias were destroyed by fire.

In the neighboring Sequoia National Forest and additional sequoia groves managed by other organizations, thousands of large sequoias were killed by the fire. These estimates are from aerial surveys and sequoia grove maps; additional assessments on the ground are needed to more fully document fire effects in these groves. Show 10 40 per page.

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Brush and smaller trees are destroyed, leaving sunny patches and a clear forest floor, perfect for germinating seeds. Fire loosens the soil, allowing seeds to fall into the mineral-rich earth and gather moisture that was previously drawn by larger plants. Tiny sequoia seeds then have a fighting chance to grow to the size of their huge cousins. As the forest debris, or duff, builds up again, the seedling is protected from the cold and seed-eating creatures. Only a small percentage of seeds ever germinates and grows to adulthood.

Too much sun, not enough moisture, or an unexpected fire can kill young, barely rooted seedlings.