FLAGSTAFF, Ariz. — A few miles northwest of Flagstaff, stretching
toward Grand Canyon National Park, is the largest continuous ponderosa
pine forest in the world. Some forest stands are crowded with thin,
densely packed trees, while others are spacious, with scattered clumps
of towering yellow-barked pines.
The marked contrast is the result of one of the oldest experiments in
forest restoration in the country, taking place here in the Gus Pearson
Natural Area. The area, part of the 5,260-acre Fort Valley Experimental
Forest at the base of the San Francisco Peaks, is a living laboratory
aimed at answering the biggest questions in the management of forests
to reduce the risk of catastrophic wildfire: Is it better to burn or to
cut? How many trees need to be removed to change fire behavior? What is
a "natural" forest in the 21st century?
To find the answers, researchers from Northern Arizona
University's Ecological Restoration Institute have set up three plots,
each with a different treatment prescription: One employs tree thinning
to remove "fuels," or overcrowded trees, followed by controlled,
low-intensity burning; one uses only thinning; and a control, where
nothing is done.
The goal is to recreate the condition of the forest that
existed before the first European settlers arrived and began
suppressing wildfires, said Diane Vosick, associate director of the
institute. "We strive to reduce the fuel loads so that fire can come
through" at a low burn, instead of a high-intensity, crown-scorching
burn, she said.
Like many other forests around the West, these stands within
the Coconino National Forest did not see uncontrolled fires for more
than a century. As a result, the area became choked with thin trees
that were allowed to grow unchecked by natural fire cycles,
out-competing native grasses and increasing the forest's susceptibility
to unnaturally high-intensity, catastrophic fire, as well as bark
beetles and disease.
"Asking ponderosa pine ecosystems to thrive under dense stand
conditions with heavy fuel accumulations that support crownfire is like
asking spotted owls to thrive in open, sunny park-like savannas instead
of the dense cool forests they are adapted to," said Wally Covington, a
forest ecologist and director of the Ecological Restoration Institute.
"It just won't work over the long haul."
In the Gus Pearson Natural Area, Vosick said there were
between 20 and 30 trees per acre before 1876, but by the 1930s, the
number of trees increased to more than 1,200 trees per acre, primarily
due to fire suppression and grazing.
The experiment — the first ecologically based ponderosa pine
forest restoration project in the Southwest — began in 1992. First,
most of the small, thin trees that grew after area settlers began
suppressing fires, about 1876, were cut and removed, with a few left
behind to replace trees that had died or been cut in the past 130
years. Researchers also removed the top layer of soil that had
accumulated over the past century to expose pre-settlement soil. They
then scattered native grass throughout the plot.
The thin-and-burn sites were scorched in 1994, and continue to
be ignited every four years, mimicking historical fire patterns. On the
thinning-only units, researchers used the same level of tree thinning
but did not manipulate the forest floor and did not conduct burns.
After 15 years, researchers say that the thin-and-burn method
is the most effective way of restoring the forest and reducing the risk
of unnaturally hot-burning wildfire. The plot is now an expanse of
sun-dappled, park-like ponderosa forest, with scattered clumps of big
yellow-bark pines and well-spaced young "blackjacks" — a marked
contrast to the dark, overcrowded control stand adjacent to it. And in
the absence of the removed trees, the forest floor has grown rich with
squirreltail, Arizona fescue and other native grasses, and forbs like
Wheeler's thistle and silvery lupine.
Creating a more spacious forest has also allowed the mature
trees to flourish, by removing the competition. "After treatment, the
old-growth trees started growing like teenagers," Covington said.
The project has attracted a procession of high-ranking federal
officials, including former Interior Secretary Gale Norton, Agriculture
Secretary Mike Johanns and U.S. Senator Jon Kyl (R-Ariz.). In Flagstaff
and elsewhere, the research has been used in efforts to reduce the risk
of catastrophic wildfire in ponderosa pine forests.
A city in the hot seat
The city of Flagstaff, population 53,000, is completely
surrounded by national forest, and its "wildland-urban interface" — the
area where forest meets city — covers about 140,000 acres of public
land, military installments, national park land, city land and private
property. The Flagstaff area sees about 400 wildland fires each year,
most caused by lightning. In 1996, the far-ranging Hochderffer fire
burned more than 16,000 acres, making it the largest recorded wildfire
in the Coconino National Forest.
John Nelson, a staff officer with the forest's Mormon Lake
ranger district southeast of Flagstaff, said the research has allowed
forest managers to be smarter about how to conduct fuel treatments and
restore the forest.
"I think it's key to what we're doing," he said. "We're better
able to represent natural conditions, and when you're using data like
that, it makes a lot more sense to the general public."
Thinning and then regularly conducting prescribed burns
appears to be effective, Nelson said. He credits fuel treatments
southwest of town with reducing the bite of the Woody Fire in 2006. "So
far, what we've done in the area seems to be showing that it's
working," he said.
So far, the Forest Service has treated about 50 percent of the
wildland-urban interface around Flagstaff, and the other 50 percent is
in the pipeline, Nelson said. Eventually, the agency hopes to move
beyond the fringes of Flagstaff and conduct larger-scale treatments at
the landscape level, he added.
The project is not without its critics, however. When the
experiments first began, the Sierra Club denounced the proposed cutting
and urged researchers not to fell any tree bigger than 12 inches.
Arizona's Department of Game and Fish has successfully pushed
for some areas in the Fort Valley Experimental Forest to remain dense
to provide cover for the northern goshawk and other wildlife.
Nelson said that kind of mitigation is not unusual. "Every
site is different, and you have to do things differently in key
wildlife habitat," he said. "But generally you can adapt the standards
to any situation."
A diversity of opinions
Ethan Aumack, director of restoration programs at the Grand
Canyon Trust, a Flagstaff-based environmental group, said the
institute's emphasis on restoring the forest to pre-settlement
conditions is "one of several perspectives" on how to manage ponderosa
pine forests, particularly as climate change warms the Southwest. Other
researchers, such as Don Falk at the University of Arizona in Tucson,
are looking at how to restore an ecosystem to the point where it can
accommodate fire — not necessarily recreating pre-settlement
conditions.
"What we're asking has huge implications for how ecosystems
are managed in the Southwest," said Falk, an associate professor in the
University of Arizona's School of Natural Resources. "We want to know
how we can reintroduce fire as a process and modify forest structure in
such a way as to maintain the adaptability and resilience of the forest
ecosystems in the face of a changing climate."
Aumack, who also serves as co-chair of Gov. Napolitano's
Forest Health Council, said that given the expansion of urban
development into forested areas, conducting treatments could be
increasingly difficult, he said. "The question becomes how you arrange
treatments across the landscape to bring the wildfires back to a lower
intensity," Aumack said. "There's no one solution."
Treatments are expensive, he noted. It costs about $500 to
thin one acre of ponderosa pine forest and about $25 to burn an acre.
"I don't think any agency is going to perfectly be integrating science
into management, because they're constrained by time and budgets. So
there's no easy answer there," he said.
Vosick said too much of the Forest Service's budget goes to
fighting big fires, instead of doing fuel treatments to prevent them.
"Firefighting is just sucking up all the dollars," she said. "That's
like waiting for the patient to be in the emergency room. Better to
fund treatment and reduce the risk."
Nelson of Coconino National Forest declined to talk about the
budget issue but said he is confident that the forest will receive the
funds it needs for fuel treatments.
The next step will be to take fuel treatments to the landscape
level, changing fire behavior across tens of thousands of acres. "I
think we're primed to make a lot of progress in this region," Aumack
said.
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