August Complex
A Wildfire Resilience Success Story: Forest Health treatments yield important management insights
The largest wildfire in California history
In mid-August, 2020, a plume of moist air from Tropical Storm Fausto headed northwards, mixing with a hot, dry, high pressure system that had been situated over California and Nevada. The resulting atmospheric instability produced an unprecedented dry lightning storm. Between August 16 and August 18 more than 12,000 cloud-to-ground lightning strikes were recorded, resulting in some 585 ignitions.
Of those ignitions, 37 would go on to constitute the August Complex. Producing fires that were substantial in the own right - such as the Elkhorn and Doe fires - they would eventually merge, leaving a million-acre footprint across seven counties.
The August Complex burned from August 18 to November 12, 2020.
It ultimately consumed 1,032,648 acres, around 1% of the state's total landmass.
Photo Credit: NASA
The August Complex burned across three national forests - including Mendocino, Shasta-Trinity, and Six Rivers - and seven counties, including Mendocino, Humboldt, Trinity, Tehama, Glenn, Lake, and Colusa.
Tehama Mendocino Fuel Reduction Partnership Project
Critics wouldn't look at a 'giga-fire' like the August Complex and find much success in it. However, every incident provides an opportunity to evaluate the result and adapt future practices based on that result.
The Tehama Mendocino Fuel Reduction Partnership provided one such opportunity. Under a CAL FIRE Forest Health grant awarded to the Tehama County Resource Conservation District, in collaboration with the Mendocino National Forest (Paskenta), and Crane Mills, the August Complex allowed for a comparative study in fuels management practices that will guide management decisions well into the future.
The map at left shows all fires since 1980, with those greater than 10,000 acres displayed more prominently.
The area has an extensive fire history, but all prior incidents dwarf in comparison to the August Complex.
The footprint of the Tehama Mendocino Fuels Reduction Partnership areas can be viewed at left.
At the time of the fire approximately 2,500 of the planned 4,054 acres had been treated.
Treatments across the project area focused on basal area reduction, and included mastication, manual hand-cut/pile, mechanical cut/pile, and mechanical thin/biomass removal.
As depicted on the map, some 90% of the project footprint area was burned over by the August Complex fires.
Differences among treatments provided an opportunity to observe how treatment prescription may have influenced fire behavior and overstory mortality.
Lessons Learned
A review of the landscape post-fire suggests that fire behavior was influenced by all basal area reduction treatments. Fire activity was moderated, transitioning from crown fire to surface fire where basal area - and therefore canopy density - were reduced.
Despite the moderation in fire activity, complete overstory mortality was observed in all treatment areas where biomass had not been removed. These treatment areas experienced a rearrangement of fuel such that the thick mat of masticated or piled material acted as 'jackpots,' eventually killing the roots of overstory trees as they smoldered and emitted heat.
Areas within the footprint that were treated at least four years prior did not experience overstory mortality, likely because the resulting fuel mats had decomposed or the piles had been burned previously.
Minimal mortality was observed in treatment areas where the biomass was removed from the site (in this case, utilized for bioenergy production).
Mastication in this stand resulted in a mat of material with a depth of approximately 24 inches.
Long fire residence time in the fuel bed likely resulted in root damage and eventual mortality to the residual overstory.
This stand was masticated approximately four years prior to the August Complex fire.
The interval between treatment and the occurrence of wildfire allowed the material to decompose, resulting in beneficial fire effect and minimal overstory mortality.
This stand was mechanically thinned followed by biomass removal in the months prior to the August Complex fire.
The reduction and removal of fuel resulted in minimal overstory mortality.
A Forest Health Success Story
While the treatment areas in the Tehama Mendocino Fuels Reduction Partnership project did reduce wildfire activity, this event constitutes a different kind of success story. By providing a rare opportunity to compare fuels management practices, this project will help guide biomass management decisions to come. This small case study suggests that biomass generated from Forest Health Fuels Treatments should be removed from the site if managers want stands to be resilient to wildfire in the near term.
Forest Health practitioners can take these lessons and use them to guide management decisions goin forward.
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