Montana wildfire observations will increase understanding of fire behavior in changing Western forests
By Bob Berwyn
SUMMIT COUNTY — Fire experts said they were surprised by the intensity of a pair of fires that burned in Montana this summer during less-than-extreme fire weather. The fire moved through areas of beetle-killed lodgepole faster than some previous fire modeling suggested.
The rapid spread of the two fires was probably the result of a perfect mix of fuels, including recent beetle-killed lodgepole pine with flammable red needles, stands of older beetle-kill in the gray stage. Live trees and an a full-grown understory that provided ladder fuels.
The observations could help experts gain a better understanding of how fires will behave in beetle-killed forests. Some previous fire observations, in Yellowstone, for example, suggested that pure stands of dead gray-stage lodgepoles could actually slow the spread of a blaze, and some fire modeling has also suggested that the gray trees are not as susceptible to fire.
“Fires grow faster and bigger than this, but not in years like this. It was unexpected,” said fire researcher William “Matt” Jolly, referring to weather and fuel conditions during the fires. In some areas, the understory was still green, and temperatures weren’t extremely high, with the fire danger rating listed as moderate before the fires. Despite those conditions, the blazes grew to intense crown fires, consuming all the fine branch material in the dead, gray beetle-killed stands.
Both fires burned so hot at times that they created their own weather, which intensifies the fires even more.
“The summer started incredibly wet … the fire hazard was barely at moderate,” said Jolly, a researcher at the Missoula Fire Sciences Lab, part of the Forest Service Rocky Mountain Research Station. Fire experts weren’t expecting the fires to spread so quickly in those circumstances, he said.
The lightning-sparked Saddle Complex fire was detected Aug. 10 and made a 17,000 acre run on Aug. 22 through an area with about 40 percent beetle-killed lodgepole. It burned across a footprint of more than 32,000 acres.
Jolly said the fuel mix included red- and gray stage beetle-kill and subalpine fir with branches extending to the ground. Both the subalpine fir and the dead lodgepole had been exposed to the sun, which Jolly cited as another possible factor in the explosive growth of the fires.
The lightning-caused Salt Fire burned more than 24,000 acres, in some places roaring through areas of almost pure beetle-killed lodgepole, again at a rate that caught fire experts off-guard.
Jolly characterized the complex mixture of fuels as very responsive to short-term weather conditions.
“There seems to be a big coupling between weather and the red-stage trees,” Jolly said, explaining that ignition tests under controlled conditions show that red needles ignite three or four times faster than green needles, even when those green trees are drought-stressed.
Jolly emphasized the benefits of watching the fires first-hand and said the observations underscore the fact that there are still things that fire researchers don’t understand when it comes to forecasting fire behavior.
Filed under: Environment, forest fires, forests, US Forest Service Tagged: | beetle kill, Idaho, Lodgepole Pine, Montana, Mountain pine beetle, Rocky Mountain Research Station, Saddle Complex Fire, Salt Fire, United States Forest Service, Wildfires, William Jolly