Forest service says lower-severity fire areas could activate sequoia seedling growth, fuel load reductions, leave more water for new growth
PORTERVILLE – Snow, rain and hail over the weekend cleared away the summer smoke from California wildfires and have given Valley towns the beautiful view of the Sierra Nevada mountains again. Since the majority of the Castle Fire has come under containment the forest service is surveying some of the damage left behind.
Thousands of acres have been burned, but it is not all bad news. According to the forest service approximately 9,800 acres (35%) burned out of the 27,830 acres of giant sequoia groves in the Monument, with approximately 6,000 acres (61%) burning at high-severity. Where fire burned at lower-severity, or where high-severity patches were small, the fire is expected to have restorative effects on the groves by activating sequoia seedling growth, reducing fuel loads that may influence future fires, and clearing out small trees leaving more water and light available for remaining plants and sequoia seedlings.
The 2020 Castle Fire burned an estimated 13,600 acres in 10 giant sequoia groves located within the Giant Sequoia National Monument of the Sequoia National Forest, which has a total of 33 groves. The Forest Service groves impacted were Alder Creek (shared with private landowner), Mountain Home (shared with State of California), Belknap Complex (McIntyre, Wheel Meadow, Belknap; shared with private landowner), Dillonwood (shared with National Park Service), Middle Tule (shared with State of California), Burro Creek, Freeman Creek, Silver Creek, Upper Tule, and Wishon groves.
Giant sequoias are a fire-adapted species and need localized high-severity fire to regenerate. Forest fuels in many groves have dramatically changed from fire exclusion and the presence of drought-killed trees of other species, which influences how severely wildfire moves through them. Patches of high-severity fire in the 2020 Castle Fire were likely much larger than they would have been historically, and this could mean an uncertain future for portions of the groves.
The U.S. Forest Service will not be able to assess grove impacts until a thorough survey can be conducted. Preliminary satellite data indicate the highest losses of mature giant sequoia trees are in the Belknap Complex and the Freeman Creek groves. Of the recently burned groves, the U.S. Forest Service Burned Area Emergency Response Team found that Alder Creek, Belknap Complex, Dillonwood, and Freeman Creek groves burned at the highest soil burn severity, which implies there were also higher losses of trees in those groves. Protection measures around the Stagg Tree in the Alder Creek Grove and the Bush Tree in Freeman Creek Grove resulted in minimal damage.
In 2017, the Pier Fire burned through the Black Mountain Grove on the Sequoia National Forest, and the Railroad fire burned through the Nelder Grove on the Sierra National Forest. In both places, there were significant losses of mature giant sequoia trees. The Save the Redwoods League and the U.S. Forest Service Ecology Program teamed up to monitor giant sequoia losses. They found that in the Nelder Grove, 39 out of the 104 mature sequoias died. In the areas burned at higher severity sampled in the Black Mountain Grove, 52 of the 183 mature sequoias surveyed died. These events raised awareness that even the oldest, largest giant sequoias are vulnerable to high-severity fire.
Large areas of high-severity fire within giant sequoia groves are concerning because most of these ancient trees lived through hundreds of fires, yet modern wildfires are killing them. Also, while a pulse of giant sequoia seedlings will germinate after a fire, new seedlings often have difficulty competing with the shrubs that tend to flourish in response to high-severity fire. However, with careful monitoring of giant sequoia seedlings, the forest service may be able to intervene by manually reducing competing shrubs and planting giant sequoias if necessary.
Recent fires highlight the need for restoration in the giant sequoia groves. By reducing fuels through prescribed burning and other density-reduction treatments, the likelihood of future large, high-severity fires can be reduced. The Giant Sequoia National Monument Management Plan requires protection, preservation, and restoration of giant sequoias through management activities. The U.S. Forest Service partners with Tule River Indian Tribe, National Park Service, Save the Redwoods League, and Cal Fire on best management activities.