Using a recent statewide inventory of forest lands, UM researchers are creating computer models that will let landowners and managers in Montana know the degree of fire hazard on their property, what treatments would reduce the risk, at what cost and how much revenue, if any, could be gained.

Up to now no such assessment has been available because there was no comprehensive forest inventory to base it on. Existing surveys were spotty and their criteria inconsistent, according to Carl Fiedler, a research associate professor in UM’s School of Forestry and leader of the new fire-hazards study.

Specially trained crews from the U.S. Forest Service sampled thousands of plots on federal, state, tribal, municipal and private lands. Their Forest Inventory Analysis for Montana, finished in 1999, includes detailed information on numbers of trees, sizes, species, density, condition and location.

Fiedler now is working with this data to classify forests into nine categories, or forest types. He then uses computer models to evaluate each category for fire hazard.

“We want to determine the crowning index for a range of conditions in each forest type,” he says. “That is the wind speed at which a fire in the tree tops, or crowns, can be sustained.” Crown fires generally are considered stand-replacing events, killing nearly all the existing trees.

Forest stands with a low crowning index are high fire hazards because they require winds of only 10 to 15 mph to sustain a fire, Fiedler says. Stands that require 50-mph winds are low hazard because such winds are rare.

“That analysis allows us to identify where the forest-fire hazards are in Montana, what conditions create the biggest hazard, and then we’re looking at applying treatments in high-hazard areas to reduce the risk,” he says.

Fiedler and research associates Chris Woodall and Steve Robertson have developed computer programs that model different forest conditions and simulate various hazard-reducing treatments, from thinning to more comprehensive approaches. They can then re-run the program to see what effect each treatment has.

“We can also see how much a treatment costs versus the effect you get,” Fiedler says. He and Charles Keegan, associate director at UM’s Bureau of Business and Economic Research, have developed other computer programs to determine the harvest and prescribed-burning costs associated with treatments, and the potential revenue they generate from timber. Such information would help landowners and managers make the best decisions about protecting and using their resource.

Fiedler says many forest fire-hazard reduction treatments use a “thinning from below” approach, which removes everything below a certain size but gives little consideration to what remains. His models instead work to achieve the best example of whatever type of forest is at issue.

“Our approach is not based on how much wood you get,” he says, “but on what you need to leave” to create sustainable forest conditions with low fire hazard.

“The idea is if you keep the trees that are best adapted, vigorous and in appropriate sizes and numbers for the type of forest we’re looking at, then by definition the conditions we create should be more fire-resistant,” he says. However, some proof would be nice.

“Prescriptions for each category are intended to lower the fire hazard, but just calling it a fire-reduction treatment doesn’t mean it really works,” Fiedler says. “That’s where the models are helpful. They allow us to look at each scenario and run it out into the future to see if a treatment continues to be effective decades later.”

Study results should be available to the public this spring.

— Caroline Lupfer Kurtz