Fire-free Forests Stressed
In 1806 Meriwether Lewis passed through what is now downtown Missoula, Montana while heading home on the Fourth of July.
A classic stand of old-growth ponderosa pines in the Pattee Canyon Recreation Area near Missoula.

Today he would probably remark that not only has the population around here increased, there are also more, rather than fewer, trees astride Mount Sentinel, which looms over the city in glacier-rubbed beneficence. More recognizable to Lewis might be the few remnant acres of old growth around the hind end Mount Sentinel. "That's a big one," says Forest Service fire ecologist Steve Arno, appreciatively eyeing a 300- to 400-year-old ponderosa pine. Its trunk runs straight and untapering to its first branches a hundred feet off the ground.

Scorching Scars

Vic Dupuis, who studies the development and care of forests as a silviculturist, runs his hand across the four visible fire scars that form a small Gothic arch at its base. Each time the fire burned hot enough to penetrate the bark, the tree poured out pitch to seal the exposed heartwood from insects and rot, then commenced to grow around the wound in slow motion.

As a sapling -- just after the Pilgrims realized Plymouth Rock wasn't Virginia -- this ponderosa felt the scorch of fire every 15 to 25 years. It probably sprouted in soil opened up by fire and made comfortably alkaline by ash. The next time fire came through, the young ponderosa was well-equipped for survival: Buds of new growth are large enough to keep growing even if some fresh needles are scorched dead.

Native Americans in the region acquired horses in about 1730, allowing them to expand their territories and increase their numbers. Fire was a favorite Indian hunting tool and this pine now enjoyed just seven to nine years between fires. Indian burning both stimulated grass growth for game animals to eat and made it easier for hunters to spot and pursue their quarry on open ground. Without small trees coming from below to compete for water and nutrients, this giant bulked up like a weight lifter on steroids.

Pitch oozes where a bark beetle has drilled into this tree's trunk.

Fire Suppression's Results

Flames last licked the tree's trunk more than 100 years ago in 1890. The Indians had been pushed onto reservations and vigilant fire protection from the Forest Service was only 20 years away. Since then many more seeds from its prolific cones have sprouted, but the upstarts haven't done the Old Man proud. Without frequent fire to stimulate the flow of pitch in their trunks, the younger trees' softer heartwood will rot more quickly after they die. They'll topple in only a few years, depriving snag-dwelling critters of prime habitat.

Under the old pine's protective shade, thousands of seedlings of Douglas-fir sprang up in the grassy parkland, too. But there's not enough water to go around, so the young trees get stressed. This causes a change in the chemical composition of their pitch -- an event detected by neighborhood bark beetles, who come running. While a healthy tree can literally drown a chewing bark beetle in pitch, a thirsty tree can't, so the mama beetle tunnels into the living cambium layer just beneath the bark to lay her eggs. When the larvae hatch, the grubs eat their way around the circumference of their host tree, girdling and killing it as effectively as if you'd hacked around it with an ax.

Too Many Trees

Arno and Dupuis agree there are too many trees here in Pattee Canyon. Moreover they are the wrong trees. Douglas-firs are adapted to higher, moister elevations. Fires burn far less frequently there, so the trees don't have as many fire defenses. Once the Douglas-firs invade these lower-altitude ponderosa stands, they create fuel for hotter, more destructive fires. A 1977 blaze near here was such a fire, burning 1,200 acres and five houses in 55 minutes.

Dupuis is working to restore much of Pattee Canyon's National Forest land to widely spaced, open ponderosa pine, so fire can return to its role as a valuable partner in shaping a sustainable landscape. He's already thinned pulp and saw logs, slashed out the undergrowth and burned in some places. Because this is a heavily used public recreation area, he may have to wait 10 years before he can thin some stands again to minimize the visual impact.

Though complaints are fewer than when the project started in 1990, Dupuis says the new science is still a hard sell. "People want to save Nature from the nasty foresters. But the Nature they want to save is the Nature created by foresters," who used to put out all fires.