About 10 acres went up in smoke in the Shoshone National Forest Sept. 24.

There was a purpose for that.

The burn area is due east of the junction of Wyo. Highway 296 and U.S. Highway 212 in the Shoshone National Forest south of Red Lodge, Mont. It’s likely there hasn’t been a fire in the area in 100 years, so the prescribed burn is a preventive measure to keep a big fire from burning out of control, says Tim Klukas, Shoshone National Forest north zone fire management officer.

The purpose is to reduce fuels like trees and sagebrush in a mosaic (checkerboard) pattern to act as a fire line to prevent the spread of wildland fire, Klukas says.

Carrying drip torches containing one-third gasoline and two-thirds diesel fuel, the fire crew torches the grass and sagebrush. In some spots the grass ignites instantly, while in other places the greener grass is reluctant to burn.

Like a blacksmith’s bellows, the wind fans the flames, pushing the smoke uphill like morning fog clinging to a river.

“Perfect wind,” Klukas says.

The fire burns quickly, crackling like dry twigs in a campfire.

The crackling sound is the green vegetation expanding and exploding, Klukas said.

“Like popcorn,” he says.

A transportable weather station reports in a dispassionate computer voice to Klukas’ two-way radio 30 percent humidity with 2 to 3 mph winds and gusts up to 6 mph.

If the humidity is 30 percent, it is relatively dry, providing good conditions for a controlled burn. A 20 percent humidity is almost too dry, enabling fire to spread too rapidly. With 100 percent humidity it is either raining or foggy, Klukas said.

With a cool demeanor, borne from experience and training, the crew lights the grass and brush and notes their handiwork as the flames burn practically at their feet. In their distinct Nomax green and yellow attire, the firefighters appear relaxed, but they know what they are doing.

The 11-person crew of men and women keep the fire contained to a specific size so they can control it. For public safety the crew will patrol the area until Sept. 26 to ensure the fire dies and doesn’t spread, Klukas says.

Thinning trees reduces torching.

As the fire lays siege around its base, a lone pine tree bursts into flames. It does indeed look like a torch. The tree’s needles sizzle like bacon cooking in a greasy skillet.

If two-thirds of a tree’s foliage or needles are consumed by flames the tree will likely die. If the pines are removed from the fire line they won’t torch. When trees torch, the burning pine needles transported by the wind act as a firebrands to land and accelerate a wildfire’s growth, Klukas says.

Another objective is to remove 30 to 60 percent of the sagebrush. By thinning sagebrush, particularly older sage, it reduces the spread of fire. Sage bark is dry and leaves are oily, making for a very combustible plant that spreads fire rapidly.

Paring down sage prompts more grass, thus encouraging a diversified wildlife like elk to graze on it, and improving grazing allotments for livestock, Klukas says.

The fire grows by leaps and bounds in the tall grass and scattered trees, but burns itself out quickly when it consumes its fuel.

Prescribed fire protects watersheds. If a fire’s spread is checked by fire lines, forests can be protected. More forest canopy provide more shade to prolong snow melt, thus reducing erosion and the volume of sediment during spring runoff, Klukas says.

Prescribed fires cost between $50 to $500 per acre to ignite and manage. A wildfire costs from $1,000 to $5,000 per acre to fight, he says.

Klukas says he wishes to inform the public that the Forest Service is careful with controlled burns. They painstakingly plan fires that pose no risk to humans, but improve habitat, he says.

If more controlled burns are initiated, they will form barriers when wildfire strikes. Then firefighters’ focus can be protecting property and campgrounds, Klukas says.

“If we can put in a few breaks here and there maybe it won’t all go up at once,” he says.

Sagebrush and grass are burned but some is allowed to remain during the process last week. The Shoshone National Forest fire crew also burned some conifers.