Ecologists question research on burns in bug-killed forests after Montana fires

Photo by Matt Stensland
Thanks to Derek for submitting. From the Missoulian here.

Last summer, a wall of flame roared through a three-mile stretch of tinder-dry, bug-killed lodgepole pine forest and forced a large group of firefighters to retreat to a safety zone.

An official said later the flames moved through the trees like fire does through grass.

In the upper West Fork of the Bitterroot, another fire blew through 17,000 acres in a day. Much of that area also was covered by lodgepole pine killed by mountain pine beetle.

That unusual fire behavior now has some fire ecologists questioning conventional research that suggests that wildfires won’t burn as fiercely through forests filled with bug-killed trees.

“We definitely saw some unusual and pretty amazing runs under fire conditions that we would normally consider to be moderate,” said Matt Jolly, a research ecologist with the Rocky Mountain Research Station’s Fire Sciences Laboratory in Missoula.

Earlier research based on modeling suggested that stands of dead and dying trees were not as prone to flare into fast-moving crown fires. And if the fire did manage to make it into the crowns, the research said it was unlikely to stay there long.

Firefighters and researchers saw something quite different happen this summer.

“These fires were quite a bit more active than what the conventional research suggests,” Jolly said. “The problem is most of the conventional research used simulation models. If you don’t have good observations, then you have to assume the models are correct.”

Before this year, the past three summers were marked by very wet Augusts, which is typically the peak of the wildfire season in western Montana.

“We’ve been dodging the bullet, if you will, over the last three seasons,” Jolly said.

Canadians have been reporting similar fires in their own forests filled with beetle-killed trees for a number of years.

The fires this summer burned in conditions that weren’t considered extreme over an understory that was often still green. At times, the solid walls of flame reached from the ground to far above the canopy.

In some cases, the fire was burning through a forest of mostly dead trees that had already shed most of their needles.


Jolly said trees attacked by mountain pine beetles start a downward spiral that makes them more susceptible to fire early on. Once the trees die, their needles turn red before falling off. The red needles are extremely flammable.

Once the needles fall off, the forest has a gray appearance. This summer, Jolly said the fires blew through those standing gray stands.

“A lot of people have proposed that once the needles fall off, there’s little opportunity for a crown fire,” he said. “In these gray stands, you essentially have a vertical dead fuel with extremely low fuel moistures that once ignited, can create a flaming front.”

Fire researchers also noted the fires were quick to form a column that created its own weather, which further enhanced burning conditions.

For these fires to occur, Jolly said fuel conditions, weather and topography have to be aligned just right.

In many cases, the fire conditions were not considered extreme.

“These fires burned under less than extreme conditions in the same way that a healthy stand would burn under extreme conditions,” Jolly said.

The dead stands are made up of vertical fuels that respond quickly to changes in the weather and humidity levels.

“That’s why it happens very quickly,” he said.


With hundreds of thousands of acres of bug-killed stands scattered across the West, Jolly said there is a “very real possibility” of seeing more fires like this past summer’s.

“It’s totally dependent on weather,” he said. “As soon as we have a dry year like we saw in 2000 or 2003, which came with a very prolonged period of drying, it will be very interesting to see what happens.”

Bitterroot West Fork District Ranger Dave Campbell said research like Jolly’s will be important to those who fight and attempt to manage the blazes.

“This was a good opportunity for us to partner with the fire lab, which has some of the best fire scientists around,” he said. “Hopefully, we will be able to make the models for the future.”

Read more:

6 thoughts on “Ecologists question research on burns in bug-killed forests after Montana fires”

  1. The premise of the original claim was that dead lodgepole forests don’t burn any worse than the normally intensely-flammable green stands. Of course, this disregards the the historical species compositions and the fact that lodgepoles have expanded their range by encroaching into what was formerly pure ponderosa stands. We now have excessively large Lodgepole-Ponderosa Interface zones, that are at ultra-high risk of catastrophic stand-replacing firestorms, completely “unnatural” for native ponderosa pines. Pretending that forests in the LPI are supposed to burn to a crisp disregards historical facts. We need to restore the LPI to a more “manageable” size. Sure, go ahead and let the high elevation PURE lodgepole stands in Wilderness die and burn, like it is supposed to but, don’t let the firestorms “wander off the rez”.

    • Foto, in many places in the Interior West, lodgepole grows associated with spruce or by itself, with no ponderosa involved. I’m not sure exactly where the fire in the article was located, but it could have been one of the many pure lodgepole stands.

      • In Idaho, lodgepoles VERY commonly are growing underneath, or in pure pockets within the greater ponderosa pine forests. I also saw lodgepoles in Montana invading into ponderosa stands. Here in the Sierra Nevada, you also often see lodgepole invasions, due to a lack of historic fire suppression. Certainly, lodgepoles are opportunists and will definitely take advantage of a wildfire in mixed conifers, grabbing as much of the scorched land as possible. Indians were smart and probably knew that lodgepoles were not good to let grow underneath the fire-resistant ponderosas, at least at some level. Certainly the LPI is MUCH bigger than it ever was.

  2. I am not surprised that the bug kill lodge pole pine is burning hot. Anybody that cuts firewood knows that seasoned and checked wood burns better than green wood and puts off much more heat. It doesn’t take a drought year in seasoned bug kill to cause it to burn hot. Standing snags dry out quick in the summer since they aren’t in contact with the ground. I think it just comes down to the sheer volume of standing dry fuels and the amount of heat it produces when burning. The larger limbs and bowls of the lodge pole are drier after the red needles drop. Checks in the main trunk of lodge pole snags usually don’t occur until the needles drop.
    Dead stands can and do burn very hot, scorching the soil and consuming almost all of the dead wood.

  3. Bozeman and Helena Montana’s municipal watershed is full of MPB killed lodgepole. Come to think of it-so is Denver’s. Change will only come about when the people of Bozeman drink bottled water for 6 months after a fire. That might just make the cover of TIME magazine. The Las Conchas fire this summer came very close to burning up Albuquerque New Mexico’s municipal watershed which is also the site of the Jemez Mountain collaboration that is so championed by Sen. Bingaman.

    These lodgepole forests never burned for the last 100 years because they were young forests. “asbestos forests”, as Andy Stahl once called them is a perfect description. Nothing fireproofs a lodgepole forest for the next 100 years like wildfire. The forest of today is starting to look a lot like the forest of 100 years ago-except the vast fires that made Colorado so beautifull with Aspen. Was it global warming that burned off so much of Colorado 100 years ago? It makes one wonder if there isn’t “large area” geographical “pulses” in lodgepole forests. AS in I wonder if this large scale MPB killed lodgepole followed by large scale fire event hasn’t been repeated over and over again.

    Anyway, wildfire will drive the forestry and logging issue for the next ten years for the simple fact that the one driving constant that will shove aside all other peripheral variables is the fact that fire hazard will just keep getting worse. We’ve only just begun. It will be exciting times.

  4. Some eye-witness observations from John Leiberg’s 1899 report on SW Oregon forests, which have some relevance here (1900 US Geological Survey report “Cascade Range Forest Reserve from Township 28 South to Township 37 South, Inclusive, Together With the Ashland Forest Reserve and Forest Regions from Township 28 South to Township 41 South, Inclusive, and from Range 2 West to Range 14 East, Willamette Meridian, Inclusive.”):


    (p. 277) The largest burns directly chargeable to the Indian occupancy are in Ts. 30 and 31 S., Rs. 8 and 9 E. In addition to being the largest, they are likewise the most ancient. The burns cover upward of 60,000 acres, all but 1,000 or 1,100 acres being in a solid block. This tract appears to have been systematically burned by the Indians during the past three centuries [ca. 1600 to 1855]. Remains of three forests are distinctly traceable in the charred fragments of timber which here and there litter the ground.

    (p. 288) On the lava plateaus flanking the crest of the range in Ts. 34 and 35 S., R. 5 E., grassy places created by fires before the advent of the white man have, in course of time, become covered with thick stands of lodgepole pine, now mature and giving way to stands of noble fir and alpine hemlock.

    (p. 298) The southern and central portions are covered with stands of lodgepole pine, all reforestations after fires and representative of all ages of burns from one hundred fifty years ago [ca. 1750] up to the present time [1899]. There is no portion of these or the heavier stands of alpine hemlock and noble fir in the northern sections of the township that have not been visited by fire within the past forty-five years [since 1855]. Reforestations consist wholly of lodgepole pine as the first growth. In some places on warm southern declivities brush growth comes in after fires. In other localities a grass and sedge sward covers the ground. It is clearly evident that many of the fires have been set for the purpose of promoting these grass growths and enlarging the possible sheep range. It is also noticeable that wherever fires have been kept down for four or five years there is gradual return to forest and a disappearance of the grass.

    (p. 299) The forest consists of stands of alpine-hemlock type. Ninety per cent of it is composed of lodgepole-pine reforestations. Some of these stands date back to Indian occupancy, others are the result of fires set by the white man. All of the forest is fire marked. Reforestations after fires are invariably composed of lodgepole pine. Repeated conflagrations and total destruction of the forest bring grass and sedge growths. Fires in the townships have been fewer during the past four or five years [1895-1899] than formerly, and most of the grassy tracts are slowly reforesting.

    (p. 300) The forest consists of stands of yellow-pine and alpine-hemlock types. The alpine-hemlock type here is composed almost entirely of lodgepole-pine stands, which are reforestations after fires, and occupy the western half of the township. The eastern half is covered with yellow pine of mature age, running from 5,000 to 10,000 feet B. M. per acre . . .

    The forest is fire marked everywhere in this township. Seventy-five per cent of the yellow pine is fire seared in the lower 3 or 4 feet of the trunk. Reforestations are moderate, but the burned tracts in the yellow pine show a tendency to grow up to lodgepole pine.

    (p. 305) This region was burned periodically during the Indian occupancy, as the many different ages represented in the lodgepole pine stands prove. But when the white man came into the region the areas in this particular township was covered with a uniform stand of the species. During the past forty or forty-five years [1855-1899] the timber has been burned in many locations and the subsequent reforestations have again been burned. The region is too high in altitude to permit the growth of much brush. After a fire one of three things happens: either lodgepole pine comes in as the first forest growth, or grasses and sedges form a thin, interrupted sward, or the ground remains bare of all vegetation. It is impossible to predict beforehand which one of the three phases will appear.

    (p. 319) A great deal of the forest shows fire marks. The entire body of yellow-pine growth has been seared repeatedly. Large fires burned there last summer [1899]. The lodgepole-pine stands at middle elevations are the result of fires which burned before the advent of the white man. Reforestations are nearly always lodgepole pine at all elevations. Brush growths are not common.

    (p. 395) The forest is of the alpine-hemlock type throughout. Fires of modern origin have ravaged it extensively. The great burns which cover the eastern areas of the adjoining township and wrought great havoc among what must have been heavy stands of noble fir. The forests in the eastern areas have suffered no less, and there are scant signs of reforestation. Most of the young growth now standing is overwhelmingly composed of lodgepole pine. The bottom and eastern slopes of the South Fork Canyon have escaped fairly well and carry a forest in a state of tolerably good preservation. Much of it has not experienced a fire for 300 or 400 years, and in consequence it contains a vast amount of litter, consisting chiefly of the original lodgepole pine growth which followed a fire that occurred between three and four centuries ago [ca. 1500 to ca. 1600]. The lodgepole pine has had time to mature, die, and fall down, and a new forest 150 years old has taken its place since that time.


Leave a Comment