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Massive Oregon Blaze a Match for Forest Rejuvenation

Nature: More than half of the nearly 500,000 acres either did not burn or did so at low intensity, leaving many trees better off after conflagration.


GRANTS PASS, Ore. — When Biscuit -- the nation's biggest wildfire this year -- was on its hind legs and roaring in July, anyone looking at the towering plumes of smoke in southwestern Oregon could only wonder how anything could survive.

Now that most of the flames have cooled, a closer look at nearly 500,000 acres within the containment lines reveals a landscape typical of wildfire: More than half either did not burn or burned at low intensity, leaving mature trees green, standing and better off.

"When a fire burns, unlike what is seen in cartoons, not every tree is killed, not every plant is killed, not every acre is burned to nothing," said Eric Christiansen, fire behavior analyst on the federal team that stopped Biscuit from roaring into Oregon's Illinois Valley.

Although the fire put the 17,000 people in the valley on evacuation alert as it burned five cabins and threatened others, in the long run, it maintained the well-being of individual species and the forest as a whole, said Tom Atzet, U.S. Forest Service ecologist for southwestern Oregon.

"The worst thing that we could have is to be so enamored of our forests that we eliminate the processes that change them," he said.

Charred rings on old trees show that fire returns to the area burned by Biscuit every 70 years on average on the wetter west side and every 50 years on the drier east side, Atzet said.

Just how that fire burns depends on the mix of weather, fuel and terrain, Christiansen said. A windy, hot, dry day, combined with steep ravines filled with heavy brush, downed logs and tightly packed trees, means flames twice the height of the timber and temperatures up to 2,000 degrees.

But you would hardly notice the fire that comes through sparse timber in flat rocky ground on a cool humid day with little wind. Even patches of grass survive.

Both scenarios can be found on Biscuit. As conditions changed each day and across the landscape, the fire intensity changed, creating a mosaic of results.

A satellite map for assessing rehabilitation efforts showed 19% of the Biscuit fire area, about 95,000 acres, was unburned, and 42%, about 205,000 acres, burned at low intensity, leaving green trees standing and healthy while clearing out brush and small trees.

Only 16%, about 78,500 acres, burned at high intensity, leaving little but ash and charcoal behind, and 23%, about 113,000 acres, burned at moderate intensity.

A good place to see the phenomenon is Babyfoot Lake. The fire burned hot on steep slopes around the lake, but at the shore, where the water cooled and humidified the air and a towering cliff cut the wind, half the shoreline did not burn. Centuries-old pine and Douglas fir stand as proof that fire can't fully flex its muscles here.

The same phenomenon served to spare much of the vegetation along the Illinois River, home to salmon and steelhead, said Jon Brazier, a hydrologist.

The Forest Service has yet to analyze just how logging may have affected fire behavior, an issue in the debate over how forests should be managed to reduce vulnerability to wildfire.

But logging may not prove to be much of a factor. There has been little cutting here since the 1980s, and the burn analysis of the 1987 Silver fire, which burned nearly 100,000 acres in the same area, showed little difference between wilderness and areas that had been logged.

At a cost of nearly $150 million, fighting Biscuit looks expensive. But another way to look at it would be to imagine Congress appropriating $150 million to do prescribed burns restoring fire to its proper place in the ecosystem, Atzet said.

"In an ecological sense, we just invested $150 million," he said.

For example, the kalmiopsis bush, for which the Kalmiopsis Wilderness where the fire started is named, depends on fire to kill the white fir that competes with it for water, sunlight and nutrients, Atzet said. The thin bark on white fir gives it less protection from fire than ponderosa pine and Douglas fir, with thick bark. Surviving trees do better than ever.

Spaced out more widely by fire, trees are less susceptible to root diseases, such as deadly Port Orford cedar root rot, which can be passed root-to-root, she added. Heat kills the spores.

Darlingtonia -- an insect-eating plant also known as cobra plant -- will likely expand its command of hillside bogs now that competing plants have been killed, said Diane White, Siskiyou ecologist.

Chemicals leaching out of the ashes can stimulate acorns to sprout into oak trees, giving them a head start on pines and firs waiting for the spring. Madrones will sprout from the bole -- the underground connection between the trunk and roots -- after the top of the tree is killed.

Knobcone pines not only need the heat of fire to open their cones, but their seeds love the mineral soil exposed when fire burns off the duff -- needles and bark built up over the years.

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