Sequoia grove damage assessments continue

Release Date: Nov 3, 2021

Contact(s): Denise Alonzo

The lightning-caused Windy Fire, currently 97,528 acres and 92% contained, burned into eleven giant sequoia groves. Five are entirely within Sequoia National Forest, two in the Tule River Indian Reservation, and four are shared across agency boundaries. The Forest Service is working to determine the impacts of the fire in the groves managed by the Forest Service. Initial assessments, based on observations by resource advisors and burn severity maps, indicate the fire killed hundreds of giant sequoias. Many more were heavily torched and may or may not survive. 

While most firefighters were battling the blaze and trying to contain the fire fully, a special task force of firefighters and resource specialists targeted the protection of giant sequoia trees where possible. In some groves, they constructed firelines surrounding the grove or individual groups of trees, set up sprinkler systems, and removed ladder fuels from around the grove and individual trees in advance of the fire. After the fire burned through the groves, additional efforts were made to further reduce the fire’s impact on giant sequoia trees by extinguishing hot spots in and around the trees.

During initial observations, it was apparent that giant sequoia trees treated before the Windy Fire swept through the groves were more likely to survive. Those with duff and woody debris scraped away from their trunks, especially near burn marks, were less susceptible in most cases. In the Starvation Complex, four out of six giant sequoia trees, treated before the fire reached them, survived. An estimated 116 trees not accessible before the fire were killed. Similar conditions were found in the Long Meadow Grove, where more than a decade of fuels reduction efforts helped save the giant sequoia trees along the Trail of 100 Giants.

Tree mortality has been widely used as a measure of fire severity in conifer forests in North America. Historically, there is substantial tree survival where the stand has been exposed to low-severity or mixed-severity fire regimes. Although the thresholds are subjective, overstory mortality below approximately 30% is considered low severity, 30 to 80% is considered moderate severity, and greater than 80% is considered high severity. https://www.nwfirescience.org/sites/default/files/publications/Fire%20Severity.pdf             

The following table summarizes the impacts to giant sequoias in each grove based on post-fire satellite imagery. The table below only includes the forest’s sequoia groves; all are within Giant Sequoia National Monument. Initial burn severity was assessed through the Rapid Assessment of Vegetation Condition after Wildfire (RAVG) program. This program assesses post-fire vegetation conditions for large wildfires using geospatial technology.

 

			*Windy Fire burn severity within groves
Sequoia Grove	Total Grove Acres	Acres inside Windy Fire perimeter	% Unburned	% Low	% Moderate	% High
Black Mountain	3084	90	46	46	5	3
Cunningham	32	32	0	90	10	0
Deer Creek	144	144	0	11	36	53
Long Meadow	568	568	14	28	29	29
Packsaddle	533	528	4	39	25	32
Peyrone	741	741	8	56	24	12
Redhill	602	602	0	34	35	31
South Peyrone	115	115	0	25	54	21
Starvation Complex	182	182	0	0	8	92
Total acres and overall average burn severity	6001	3002	12%	38%	25%	25%

“Within the high severity burned areas, most of the giant sequoias were burned and killed. In moderate severity areas, some giant sequoias may survive while those in low severity burned areas are likely to survive the Windy Fire,” stated Forest Ecosystem Manager Gretchen Fitzgerald. The Sequoia National Forest will be partnering with researchers and local experts to monitor the groves and determine the impacts of the Windy and Castle Fires over the next year.

“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,” stated Forest Supervisor Teresa Benson. “The Giant Sequoia National Monument Management Plan requires protection, preservation, and restoration of giant sequoias through management activities. We will continue to work with our partners, Tule River Indian Reservation, National Park Service, Save the Redwoods League, and CAL FIRE on best management practices to protect and restore our giant sequoia groves.”

“Cumulative impacts on our giant sequoias from the 2019 Castle Fire along with this year’s Windy and KNP Complex Fires will continue to be studied in coordination with the Sequoia and Kings Canyon National Parks,” stated Benson.