Giant Sequoia and Fire Statement from Berkeley Forests
Author: Rachelle Hedges
Contributors (in alphabetical order): Ariel Roughton (RPF) – Berkeley Forests Research Forest Manager; Dr. Robert York (RPF) – UC Berkeley Cooperative Extension Specialist, Berkeley Forests Research Forest Advisor, and Adjunct Faculty in the Dept. of Environmental Science, Policy and Management.
Few trees capture the attention and fascination of humans in the way that large diameter giant sequoia (Sequoiadendron giganteum) do. Their size, age, and scarcity pique our curiosity and make visiting these giants a bucket-list item for those who may otherwise not travel to a natural environment. With the devastating impacts of the 2020 Castle Fire on giant sequoia populations still top of mind, there has been great concern and public interest as the 2021 KNP Complex Fires again burn through many of the best-known groves of large diameter giant sequoia. Members of the press and general public alike have reached out to Berkeley Forests to inquire about the risks to the large diameter giant sequoia in the path of the KNP Complex Fires, and to ask about measures in place to protect these trees. Below, Berkeley Forests provides a summary of the natural adaptations and vulnerabilities of giant sequoia to fire, and gives information on the human interventions we have implemented to protect these trees from mortality caused by fire damage.
Giant sequoia are a fire-adapted species, designed to withstand fire with thick non-resinous bark and scorch-resistant foliage. They require fire to regenerate. It stimulates seed release from the cones, prepares the soil bed by removing organic material and exposing mineral soil, and (through tree mortality) creates openings in the canopy that allow sufficient sunlight to reach the seedlings below. Despite these adaptations, large-scale high severity fire can be damaging to giant sequoia, as was observed following the 2020 Castle Fire. A warming, drying climate, coupled with short-sighted forest management and fire suppression policies over the last century has created an altered fire regime that giant sequoia are not adapted to. These conditions produce fires that burn at much higher intensity and have more severe impacts across larger landscapes than historically seen in the native range of giant sequoia. Instead of preparing the seedbed, stimulating seed release and opening gaps in the canopy to allow for sunlight, these large-scale high severity fires destroy seedbeds, create unfavorable soil conditions for seeds that do remain, and eliminate the seed source by causing wide-spread tree mortality. High-intensity fires can overcome the adaptations and protections of the large-diameter giant sequoias, scorching and subsequently browning foliage, which eventually leads to mortality (as was seen in the 2020 Castle Fire).
Berkeley Forests’ own Whitaker’s Forest contains a portion of the Redwood Mountain Grove, the largest area of old growth giant sequoias (in total area) that contains more mature sequoias than any other grove. As with all Berkeley Forests properties, Whitaker’s Forest has been actively managed for many years, including the use of prescribed fire on a portion of the property as recently as 2012. Management activities such as prescribed fire can help keep fuel levels low and may protect large-diameter giant sequoia by creating conditions that encourage moderate-to-low severity fire. At this time, Berkeley Forests has not engaged in individual-tree protection efforts, such as wrapping tree bases in fire resistant materials or raking the organic matter from around the base of trees, but we continue to monitor the fire’s movement and severity and will act as needed. A UC Berkeley employee remains at Whitaker’s Forest to monitor fire activity and to coordinate with local fire personnel as the fire progresses.
At the time of writing, the KNP Complex Fires had burned over 28,000 acres in Sequoia National Park, and had over 1,400 personnel from various agencies assigned to the incident. The fire is currently burning at moderate-to-low severities, and thus does not currently present the same risks to the giant sequoia on the landscape as the 2020 Castle Fire. Fire behavior and weather conditions can change quickly, and as they change, Berkeley Forests will reassess our fire mitigation plan for Whitaker’s Forest.
Additional Resources:
For answers to frequently asked questions about giant sequoia mortality in the 2020 Castle Fire, the role of fire in giant sequoia ecology, and threats and strategies for protection, please visit the Giant Sequoia Lands Coalition page.
An in-depth condition assessment of the Giant Sequoias at Sequoia and Kings Canyon National Parks is available for download here.
Updates about the KNP Complex Fires can be found on the InciWeb site, here.
If you would like to speak with Berkeley Forests staff or faculty, please email rachelle.hedges@berkeley.edu.