National Fire Plan Success Story

Black Butte Fire Growth Slowed by Prescribed Fire Efforts
Nez Perce National Forest, Salmon River Ranger District, Idaho
National Fire Plan - Fuels Reduction
September 2006

Prescribed Fire as a Management Tool: Management-ignited prescribed fire is an effective tool for hazardous fuel reduction. Such prescribed fire is used to approximate the natural vegetative disturbance of periodic fire occurrence, thus maintaining fire-dependent ecosystems and restoring those outside their natural balance. Low-intensity prescribed fire is scientifically and strategically planned and applied by trained experts to clear ground of over-accumulated fuels. This low-intensity fire is vital to the life cycles of fire-dependent range and forest lands.

Abstract: The Black Butte Fire currently burning on the Nez Perce National Forest above the Salmon River is approximately 25,000 acres, as of September 9th. Fire growth was stalled on the eastern flank when the flames hit the Porcupine Fire of 1992. Fire growth on the western flank was slowed in the Robbins Creek drainage on September 5th as the fire entered an area where a prescribed burn was conducted earlier in the year. The decreased rate of spread afforded fire managers more time to gather information, prepare tactical strategies and position resources, ultimately increasing the safety of firefighters and the public.

History of the Black Butte Fire: This lightning-caused fire started on August 21, 2006. The eastern boundary of the fire stalled out in the Sheep Creek watershed, due to a lack of fuel. The Porcupine Fire of 1992 burned in Sheep Creek, reducing the amount of fuel available to wildland fires in subsequent years. The fire movement westward averaged a mile per day. The western boundary of the fire was slowed in Robbins Creek. Two prescribed burns, conducted in the spring of 1999 and again in 2006, resulted in a reduced amount of fuel in the Robbins drainage, which strongly contributed to slowing the fire spread westward. As the fire's edge reached the burn area, intensity was reduced considerably. As a result, the fire took five days to progress westward for three quarters of a mile through the burn. After exiting the burn area, the intensity again increased and the fire spread a mile to the west in one day.

Robbins Creek Prescribed Fire: Due to past fire suppression activities, a condition of increased fuel loads and shade-tolerant understory has been allowed to accumulate. The direct effect of a prescribed burn would be a reduction in smaller sized fuels and fire-intolerant, smaller grand fir species, which now are in place as a ladder fuel understory. Decreased fuel levels would lessen fire intensities and severities and increase the safety factor for firefighters when a wildfire does occur. This would in turn lower the risk of severe impacts on the watershed, which would not occur from a prescribed burn within controlled parameters, but would have a very high probability of occurring during a wildfire. A stand-replacement fire, such as that which occurred in 1992 in the adjacent drainage within the fire area (Scott fire) would result in unacceptable conditions within the watershed such as loss of timber, loss of wildlife habitat and high probabilities of soil erosion. While individual treatments would have localized impacts to the fuel loads, this would cumulatively contribute to a wider range of conditions that could retard the spread of a wildfire and provide fuel breaks where ground fuels and ladder fuels have been reduced.

Historically, when suppression activities were mandated by public opinion and wildland fire policies were adopted by the agency, this fire area was subject to high-frequency, low-intensity surface fires that kept the forest community in an open, structural condition and retained ponderosa pine as the dominant seral species and included warm dry Douglas fir and grand fir habitat types. Suppression activities have created conditions outside of the historic range of variability. These changes have occurred over time as a result of fire suppression, which has allowed natural fuels to accumulate. Brush has grown decadent and now occupies areas that would normally be dominated by grasses and forbs. Dense stands of shade-tolerant conifers now grow under the canopies of large ponderosa pines. A wildland fire can travel up through the smaller trees into the large pines, killing the tree. Historically, light understory burns would thin out these shade-tolerant species and perpetuate the park-like landscape.

The Robbins Creek burn of 2006 was initiated to reduce accumulated fuels and to help return this high-frequency, low-intensity fire landscape to its more natural, historical place. Fires along the Salmon River traditionally burned frequently and as a general under burn that thinned brush and reduced fuel accumulations that would otherwise cause large, high-intensity stand-replacing fire events and potential erosion and sediment problems. Results of the burn included a reduction in continuous fuels that typically carry a ground fire and a reduction in concentrated and ladder fuels that can cause single and multiple tree torching and often result in ember-ignited spot fires.

Conclusion and Future Implications: Prescribed burns such as the one in Robbins Creek can help reduce the chance of large, devastating fire events. The slower spread of the Black Butte Fire in Robbins Creek is largely due to reduced fuel accumulations from the spring burns. The delay in spread gives firefighters ample opportunity and time to prepare actions that could greatly enhance their success when taking a more direct attack on the fire. A fuel reduction program that includes prescribed fire is an effective way to reduce large fire suppression costs, protect community values, restore forest and grassland health, and improve firefighter and public safety.

Laura A. Smith
Public Affairs Specialist
Nez Perce National Forest
1005 Highway 13
Grangeville, Idaho 83530
(208)983-5143
lasmith@fs.fed.us