Trees giving bizarre clues to climate change
Suspended 20 stories in the air, Ken Bible looks down on the crown of a 500-year-old Douglas fir and ponders a mystery. It's not the obvious...
Seattle Times science reporter
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CARSON, Skamania County — Suspended 20 stories in the air, Ken Bible looks down on the crown of a 500-year-old Douglas fir and ponders a mystery.
It's not the obvious one: How does a man without superpowers hover above the treetops?
That's easy. The University of Washington forest ecologist rose to his lofty perch in a metal gondola hoisted by a 285-foot-tall construction crane.
The vantage point allows Bible to study the upper reaches of this old-growth forest, where a reproductive orgy is under way.
"We've never seen anything like this here," he says, reaching over the edge of the open-air gondola to grasp a limb laden with cones.
He counts at least 30.
"Normally, a branch like this would have about three," he says. "Why so many this year? We really don't know."
Maybe global warming nudged the trees to procreate. Perhaps it's a natural cycle.
In either case, Bible wants to pinpoint the trigger. Did the forest crank up cone production in response to temperature? Is moisture the key? Or could the flush of fertility be traced to high spring winds that whipped up a sexy cyclone of pollen?
The work is part of a bigger effort to figure out what climate change, both natural and man-made, will mean for the Northwest's iconic forests. The UW's Wind River Canopy Crane, erected in 1995 near the Columbia River, is proving an ideal tool.
The crane and the research area that surrounds it have already helped answer several fundamental questions about forests and their ability to counteract global warming. A cooperative venture with the Forest Service, the crane is the largest in the world dedicated to forestry research, and the only one in North America.
It was here that scientists put to rest the myth that mature forests are biologically moribund. By rising above the treetops, they were able to take measurements that showed old forests continue to grow and act as a sink for carbon dioxide, a major greenhouse gas.
Studies here also proved it doesn't make sense from a global-warming perspective to cut older forests and replace them with seedlings, which grow faster and had been thought to absorb more carbon dioxide. Old forests are storehouses for such vast amounts of carbon that it would take many decades for new forests to catch up on the carbon balance sheet.
"If you want to measure these kinds of things, you need to be able to get up in the tops of the trees and out at the ends of the branches where processes like photosynthesis are really going on," says UW forestry professor Jerry Franklin, who pioneered the study of old growth. "The canopy crane gives you that ability."
Scientists' thrill ride
Riding the crane is like taking an elevator to the sky.
As the gondola glides upward, the gloom of the forest floor falls away. Sunlight floods in and the temperature climbs 10 degrees. Branches draped with tattered lichens called old man's beard float past.
When the gondola reaches its apex, startled hawks sometimes circle around to see who's intruding on their bird's-eye view of the forest canopy, which spreads out in every direction like a lumpy green blanket.
The Douglas firs here can reach between 180 and 220 feet above the forest floor. The species mix also includes Western red cedar, Pacific silver fir and grand fir.
In addition to counting cones, Bible and his colleague Matt Schroeder are using the crane on this November morning to examine the buds that will determine how many new branches the trees will produce next year.
Schroeder speaks into a walkie-talkie, asking the crane operator to swivel the nearly 300-foot boom and bring the gondola hard up against a massive fir. Centuries of battering by wind and rain have flattened its crown.
Schroeder bends back the needles on the closest branch to reveal tiny brown spots that hold the arboreal equivalent of stem cells, able to form either branches or cones. "I can see about 100 buds on these top branches," he says.
There's abundant evidence from around the world that crocuses, lilacs and other flowering plants are blooming earlier each spring in response to rising temperatures. But nobody has figured out how to look for a similar response in full-grown trees. Buds may hold the answer, says Bible, director of the crane facility.
"The first thing we're going to look at is whether these buds are going to break earlier in the spring over time."
Warming is expected to bring more fires and insect infestations to Northwest forests, says Mark Harmon, an Oregon State University forestry expert who has used the canopy crane in his research. But experts are split on whether forest productivity will increase over time.
Carbon dioxide is a basic building block plants use to generate energy through photosynthesis, so it's possible higher CO2 levels in the atmosphere will act like a fertilizer. But other nutrients could eventually put the brakes on forest growth, as would the drying predicted as snowpacks diminish in the Northwest, Harmon said.
Ambitious research plans
That uncertainty about what to expect reflects how little is known about the basic biological responses of trees — even the mainstay of the region's timber industry, Bible says.
"We know next to nothing about Douglas fir, and it's the species we know the most about," he said.
Without a better understanding of the way trees will respond to a changing climate, it's hard to evaluate programs that claim to offset carbon emissions by planting trees or protecting forests.
Many of the existing data gaps could be filled if the federal government funds an ambitious proposal for a nationwide network of ecological monitoring stations called NEON — the National Ecological Observatory Network.
The 10,000-acre Wind River Experimental Forest, now home to the canopy crane and a wide array of other forestry-research projects, is on the shortlist to be included in the network.
The area would be wired with a variety of sensors to monitor the way changing climate and different land-use practices, such as logging, affect flora, fauna, soil chemistry and the entire web of life.
"These measurements are going to be made on a scale that's never been done before," Franklin said. "And for the first time, we'll be using identical instruments, so we'll be able to integrate data from across the United States."
In the meantime, Bible and Schroeder plan to spend part of the winter poring over weather data from the past year, to see if they can tease out the factors behind this year's bounty of cones, which seems to extend well beyond the boundaries of the research area.
"It's a very big cone year all around," Bible said. "There has to be a reason."
Sandi Doughton: 206-464-2491 or email@example.com
Copyright © 2007 The Seattle Times Company
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