Forests Created by Fire
by Sarah Walker
he Lewis and Clark Bicentennial observance of 2003-2006 coincides with a period of especially droughty summers along K’useyneiskit. Summer visitors to the high country are likely to see smoky horizons, or catch a whiff of smoke. Trees here are stressed from the continuing dryness of recent years. During our hot summers, forests dry out even more. With this region’s typical summer thunderstorms, dry lightning, and gusty winds, forest fires ignite and spread.
Daybreak, mid-September in the Bitterroot Mountains during fire season, with lingering smoke from multiple large fires. At lower center a small cluster of trees bursts into flame in the morning calm.
The word "fire" doesn’t appear much in Lewis and Clark’s journals during their wet and snowy trips along K’useyneiskit, except for a few references to Indians apparently having set fire to parts of the forest. But the phrases they repeated nearly every day--"thick timber," "bad falling timber," "more falling timber," "innumerable logs of fallen timber," and "emence quantity of falling timber which had falling from dift. causes i e. fire & wind"--are, really, all about fire.
Thick stands. Fallen trees on the ground. This is the look of western lodgepole pine forests, whose association with insect outbreaks and fire are well known to foresters and fire ecologists. Lodgepole pines, whose prodigious seed crops and sunlight-loving seedlings repopulate the very ground they burn upon, are today's poster child for forests created by fire. Clark called them “pitch pines.”
Today, along the higher elevations of K’useyneisskit’s cleared roadway, travelers may find themselves in living tunnels, their view blocked by thick stands of lodgepoles along the road. Beneath the look-alike trees lies a jumble of fallen dead snags, cast every which way like pick-up sticks, atop a bed of huckleberry bushes, whortleberry, and beargrass.
Dense stands of trees, nearly all of about the same age, result from the type of burn called "stand-replacement," where all or most of the trees are killed by flames or heat, but persist as standing dead snags whose bark will loosen, whose roots will decay, and which will eventually topple and fall onto the forest floor. Some forests along K’useyneiskit are like this.
These lodgepole seedlings began growing within a year or two after the pinecones that gave them birth opened from the heat of this "stand-replacement" fire. All the mature trees here were killed by the heat or flames of the fire; some of the dead snags have begun to fall over.
Lodgepole pine's fire-adapted lifestyle, which amounts to replacing itself as a result of periodic fires, has long been well known. More recently, ecologists have brought to light other species’ relationships with fire. Fire scientists have found evidence of fires from past centuries or even millenniums by studying tree rings and charcoal deposits.
Many animals, insects, birds, and plants have evolved interesting adaptations to forest fires. The time span required for these adaptations is viewed as confirmation of fire’s ancestry in forest ecosystems. A woodpecker whose feathers may have evolved to match the blackened charred tree trunks on which it forages; insects armed with remote sensing equipment that guides them to recently burned forests: fire has been part of K'useyneiskit's landscape for a long time.
Content reviewed by Stephen F. Arno, Intermountain
Fire Sciences Laboratory, and
Richard Hutto, University of Montana.
Stephen F. Arno and Rebecca P. Hammerly, Northwest Trees. Seattle: The Mountaineers Press, 1977.
“Forest Fire in the Northern Rockies,” http://www.northernrockiesfire.org/ (Nov. 3, 2003).
Roberta Parish, Ray Coupe and Dennis Lloyd, "Fire and Ecosystem Dynamics," Plants of Southern Interior British Columbia. Vancouver BC: Lone Pine Publishing, 1996, p. 14.
Roberta Parish, Ray Coupe and Dennis Lloyd, "Lodgepole Pine," Plants of Southern Interior British Columbia. Vancouver, BC: Lone Pine Publishing, 1996, p. 35.
Supported in part by a grant from the Idaho Governor's Lewis and Clark Bicentennial Commission