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The
Wind River Canopy Crane is a 250-foot "tool" that takes scientists to the tops of old-growth trees, opening a whole new realm of research.
The crane stands in the Gifford Pinchot National Forest in southwest Washington near the Columbia River Gorge. It was erected in 1995 as a cooperative venture of the Gifford Pinchot National Forest and the Pacific Northwest Research Station, both part of the USDA Forest Service, and the University of Washington.
The UW is responsible for the day-to-day management of the crane site where scientists and students from Pacific Northwest institutions and organizations around the globe have studied such things as how an old-growth forest grows, absorbs carbon, harbors animals and insects, and how it differs from younger forests.
Just as doctors
couldn't begin to understand human health by looking only at the lower
third of patients' bodies, scientists can't understand what makes forests
thrive unless they can examine whole trees.
Just as doctors couldn't begin to understand human health by looking
only at the lower third of patients' bodies, scientists can't understand
what makes forests thrive unless they can examine whole trees.
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From the
gondola of the Wind River Canopy Crane, scientists can gather samples,
install instruments, and conduct experiments in the canopies of trees
as tall as 220 feet. The crane's gondola operates in a 550-foot circle,
giving researchers access to nearly six acres of old-growth canopy.
It's at the tops of trees and the tips of branches where most budding, branching, and photosynthesis occur. It's here, where the forest meets the sky, that scientists want to study such things as how trees absorb carbon dioxide and how moisture evaporating from forests helps cool the planet.
The Wind River Canopy Crane was the third canopy crane erected in the world. There are now eight, but it is still the largest. It stands in a temperate forest. Most of the world's people-in North America, Europe, most of China and much of Russia-live near temperate forests, according to Jerry Franklin, UW professor of forest resources and the moving force behind getting the crane established.Understanding these forests is of regional and worldwide importance in the face of, among other things, growing concerns about climate change, he says.
Researchers measuring photosynthesis have learned that the process goes on year-round in the Pacific Northwest; the trees don't go dormant in the winter as was once assumed, according to Oregon State University's Bill Winner and University of Toronto's Sean Thomas. Research using the crane shows that photosynthesis slows in the winter, down to 40 percent of the rate during the summer, but not because of the cold. Rather, it's due to a lack of sunlight during dark winter days.
If this region should have many more dreary days each year-warmer, wetter winters are expected consequences of climate change for this region, experts say-then our forests may actually take up less carbon dioxide every year in spite of an atmosphere enriched with growing amounts of carbon dioxide, Winner says.
A dozen projects at the Wind River Canopy crane are currently sponsored by the National Institute for Global Environmental Change, which is funded by the U.S. Department of Energy to examine the carbon being absorbed and released by the forest-often referred to as the "carbon flux."
During photosynthesis, trees draw carbon dioxide out of the air, create wood cells with the carbon, and release oxygen back into the atmosphere. That carbon can be immediately released again if the trees burn in a wildfire. It is more slowly released when trees die, topple, and decay.
Carbon also is released during harvesting as wood is processed and if leftover debris is burned. Much of the harvested wood, however, holds its carbon when the wood is used in buildings, furniture and other wood products. The longer we use such products, the longer the carbon remains locked in the wood cells.
When carbon is lost from forests or wood products, it joins carbon dioxide from power plants, automobiles, and other sources to trap heat and warm the atmosphere.
One idea under consideration by world leaders is a system of national and international markets for "carbon credits," with carbon emissions in one place being offset by carbon absorbed elsewhere. That topic was one part of last winter's "Workshop on Climate Change, Carbon and Forestry in Northwestern North America" organized by Dave Peterson, UW professor and research forester with the Forest Service's Pacific Northwest Research Station, and John Innes, a University of British Columbia professor.
While the Pacific Northwest is one of the world's major forested regions, there has been relatively little activity concerning carbon credits, Peterson says.
One idea under consideration by world leaders is a system of national
and international markets for "carbon credits," with carbon
emissions in one place being offset by carbon absorbed elsewhere.
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"The Canadians are way ahead of any region in the United States," he says. "They have more people working on the mechanism for trading carbon credits, are working closely with private industry and have a Vancouver, British Columbia, company to facilitate trades."With a carbon-credit system, a Midwest utility might offset the amount of carbon dioxide it emits by paying a Pacific Northwest landowner to grow more trees. Or, perhaps landowners who are compensated would be willing to leave more trees behind when they harvest or else grow them longer before cutting, say 60, 70 or 80 years instead of 35- to 50-year rotations.
"Everything eventually burns or decays, returning carbon to the atmosphere, but the goal is to delay that process as long as possible," Peterson says.
Developing a carbon-trading system will take a number of steps, including advancing the science so we can properly account for carbon stored and lost in our forests, he says.It appears there is still much to learn.
Some of the key processes resulting in the storage of carbon in an old-growth ecosystem occur below ground, says Jeff Klopatek of Arizona State University, one of the researchers who-despite the availability of the canopy crane to reach the tree tops-is more interested in what's beneath his feet at Wind River.
Research in the forest around the crane shows dramatic root growth: up to 1,000 grams per year per square meter. Such growth means carbon is being gained in the area below the forest floor.
To analyze how root growth changes the nutrient content of soil, nearly 200 soil bags have been buried at the crane. Once riddled with tree roots, the bags are retrieved for processing that involves, among other things, separating and collecting all the roots down to the size of a human hair.
For another project, a Stanford University group led by Harold Mooney is monitoring fine tree roots using 64 "mini-rhizotrons." Yard-long, transparent Plexiglas tubes imbedded in the soil hold fiber-optic cables able to relay pictures of roots. Scientists are learning about the longevity of individual roots, determining how their biomass changes and, eventually, will relate such information to carbon uptake.
It's sensitive instruments such as these in use at the research site-as well as safety concerns (one must have a hard-hat when walking beneath the crane)-that make the forest around the crane closed to the general public. Research groups obtain access with the approval of a science committee and pay $185 an hour to use the crane.
A number of groups are trying to estimate the total carbon flux at the crane site to determine if the forest takes up more carbon dioxide than it gives off, making it what researchers call a "sink," or if the flux of carbon is about even or "flat."
A team of researchers from California led by K.T. Pau of the University of California-Davis is using a technique known as eddy covariance to measure changing levels of carbon dioxide and water vapor in the canopy. The group's two years of data say the site is a sink.
Meanwhile, Oregon State University's Mark Harmon and colleagues have more than five years of measurements, including the changing diameter of trees, so scientists can calculate growth and estimate how much carbon has been absorbed.
That their results show the site is "flat" in terms of carbon flux underscores that accounting for carbon in forests is new scientific territory, according to Dave Shaw, UW forest ecologist and research manager at the crane.
Some of the scientists hypothesize that the weather patterns over the past two years may be part of the reason for the difference. Annual weather events may have a larger influence on carbon flux than previously thought.
The most dramatic such event since the crane began operating was 1997-98's El Nino, Shaw says. With more than three months of warm, dry weather, the forest floor became so dry that wood and other debris decayed much quicker than usual. The rate outpaced the carbon being absorbed during photosynthesis in the stand. The site became a source of carbon in late summer, giving off more than it absorbed.
One can't help but think what this might portend for the future if global climate change leads to longer, drier summers in the region. The conventional thought has been that longer growing seasons could mean our forests would take up more carbon, helping counter some of the excess carbon we generate. Instead, this may be countered by additional decay or other unforeseen ecosystem changes.
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