How a Forest Stopped a Fire in Its Tracks
New York Times
SUSANVILLE, Calif. - Where the fire came through Blacks Mountain
Experimental Forest last September, the ground is
ash and the trees are charcoal. Black and gray are the colors,
lightened only by small mounds of red dust at the base of
some of the charred trunks - the leavings of bark beetles - and flecks
of green where new growth pokes above the ash.
Through the tall, ravaged columns, however, a living pine forest
visible. And as visitors inspecting the fire damage walk toward
the living forest, they come to an abrupt transition.
September's blaze was named the Cone Fire, for the hill where it
first thought to have begun. It burned 2,000 acres of
Lassen National Forest, and 1,600 of those were in Blacks Mountain
Experimental Forest, a 10,000-acre area within Lassen set
up in 1934 for ecological study by the Forest Service.
When the Cone Fire swept through these woods it came to a patch of
forest that was different from the rest, and stopped dead,
like a mime at an invisible wall. What stopped the fire was an
experimental plot that had been selectively logged to thin it, and
been burned in controlled fashion. The result was an open forest,
the way it might have been 500 years ago when regular
forest fires swept through the high dry country and no one tried to
"It just stopped," Carl N. Skinner said, looking satisfied
surprised. Mr. Skinner, a geographer with the Forest Service
at the Redding Silviculture Laboratory in Redding, Calif., and Dr.
Zack, a conservation scientist with the North American
Program of the Wildlife Conservation Society, along with other Forest
Service colleagues, are showing a reporter the results of
an accidental experiment that still impresses them each time they
"Night and day," Dr. Zack said.
"If we hadn't treated this it would have just blown right through
area," Mr. Skinner said.
The members of the group are part of a cooperative research project
involving different parts of the Forest Service and the
Wildlife Conservation Society.
The researchers have been trying different forest management plans
250-acre research plots for about seven years. The
point was never to find out how best to stop fires. Instead the research
was meant to develop a general picture of how different
management techniques affect forest ecosystems.
In the past, many forests were either cut down for timber or left
A century of fire suppression resulted in the accumulated
underbrush and thick tree growth that can fuel catastrophic wildfires.
Parts of Blacks Mountain and the surrounding Lassen
National Forest have had enough time to grow thick and brushy.
In the experimental plots, some were selectively logged, either to
remove bigger trees, to mimic one lucrative logging approach,
or to leave a wide range of tree sizes. The plots that had the large
trees removed were so-called low diversity plots.
"So much of this kind of forest has had the large trees removed
years," Mr. Skinner said, and now "we have very dense
forests that need thinning now from a fire hazard perspective. This
what many of them are going to end up looking like."
Other plots were both thinned and subjected to prescribed burns -
set by the researchers, a management policy that is
followed in many national forests.
Finally, some areas were subjected to prescribed burns only. The
researchers - fire ecologists, wildlife specialists, botanists -
have followed the changes in plant growth, tree growth and wildlife
populations in all the different situations.
Ponderosa pine forests are no strangers to fire. Mr. Skinner has
samples of trees up to 700 years old to find out their fire
history. Most trees showed evidence of some sort of fire about every
to 10 years. And big, intense fires occurred every 20
years or so, up until a century ago when the idea of fighting forest
fires took hold.
Once the natural fires were stopped, Dr. Zack said, the Ponderosa
Jeffrey pine forests from Baja California to British
Columbia grew thick. Underbrush, fallen limbs and dry needles
accumulated to make fuel to feed fires that would consume the
large trees and destroy whole stands of timber.
When the Cone Fire hit, it created a controlled experiment on how
different management techniques, at least in this area, affected
a big forest fire.
The results are clear to the naked eye. The fire started in an area
where the woods were thick, and quickly became intense
enough to consume the woods that it went through. It was blown south
west, but it was turned away first by a mechanically
thinned plot, which it scorched before dying out, and then by a plot
that had been subjected to thinning and prescribed burning.
The fire did not penetrate that patch at all.
In the thinned area that had no controlled burn, Mr. Skinner pointed
the effects of the Cone Fire. "We definitely changed the
fire behavior and made it so the fire dropped to the ground and made
so that from a point of view of putting out fires it's easier
to put out," he said, "but still there's sufficient fuel
here to cause a
lot more damage to the stand that was left here."
Doing controlled burns, with no thinning, worked better. But the
all was a combination of thinning and controlled burns.
The stands of moderate-size trees, what the researchers call "low
diversity," stopped the fire cold.
The high diversity stands, which included more large trees, showed
scorching for 30 yards or so, as the fire burned the
needle bed that had accumulated over five years since the last
controlled burn. Then the fire died out.
Dr. Scott Stephens, director of the Stephens Laboratory for Wildland
Fire Science at the University of California at Berkeley,
has been to Blacks Mountain Forest and seen what happened when the
Fire hit. He said in an interview that this kind of
accidental research with rigorous data was very rare.
He would have predicted, he said, that thinning and burning together
would stop a fire, but was surprised that the plots that were
thinned but not burned survived as well as they did. Many trees died,
but enough lived for the stand to recover.
The key, he said, was that when the small trees were cut, they were
completely removed, rather than leaving remnants on the
forest floor, as was done with the larger trees. That reduced the
on the ground.
"It really points to surface fuel reduction," he said,
as the most
important step to prevent big fires.
Dr. Stephens said the Bush administration's current Healthy Forest
Initiative was mainly about reducing regulation and does not
specify fire management regimens. He also said he thought that not
enough emphasis in the initiative was placed on reducing
surface fuels by prescribed burning or other means. Whether large
were removed or left made a big difference for wildlife,
Dr. Zack said. Large trees, and large dead trees, are attractive to
woodpeckers and other creatures.
Although prescribed burns are common, they are also controversial,
partly because of a fire in New Mexico in 2000 that
destroyed 200 buildings in Los Alamos, leaving hundreds of people
homeless. That fire resulted from a prescribed burn by the
National Park Service that got out of control.
Cost is also an issue. In plots where large trees were removed, timber
sales were lucrative enough that the net gain was $1,400
an acre. Where only smaller trees were cut, the Forest Service suffered
a net loss of $200 an acre.
Dr. Zack and Mr. Skinner and their colleagues agree that no single
panacea will solve the problems resulting from a century of
fire suppression. Still, they can point to the evidence on the ground,
where you can stand on a line between charred trees and