Fairbanks, Alaska-- Research completed by a doctoral student and two professors at the University of Alaska Fairbanks among the tall sentinels of white spruce guarding Interior Alaska may have an international impact on how scientists analyze climate change and predict the effects of global warming. Val Barber, a UAF paleoclimatology student whose research focuses on climate change during the last 12,000 or so years, spent the past four years analyzing data collected with forestry professor Glenn Juday and geological oceanographer Bruce Finney.
The trio took more than 260 samples from 20 different white spruce tree stands, ranging from the Yukon River to Tok. Barber, Juday and Finney's research was featured in the latest edition of Nature magazine, an internationally known science publication that covers the cutting edge of research and discovery.
The UAF scientists found that while temperatures in Interior Alaska are rising, precipitation has been leveling off, causing drought-like conditions for the white spruce and inhibiting their growth. Slower-growing trees mean scientists studying climate change will have a new perspective on how northern forests react to warmer global temperatures.
"When they do their models, they'll have to take this into account and start changing their predictions," Barber said.
Increased carbon emissions from the burning of fossil fuels and other sources during the past century has caused temperatures to increase significantly through a process known as the "Greenhouse Effect."
Until now, scientists have assumed that rising temperatures and longer summer seasons would cause northern trees to grow faster, thus increasing their capability to absorb carbon from the atmosphere. The Alaskan and Canadian boreal, or northern, forests have been considered a potential lifeboat during the climate change.
Scientists refer to the boreal forest in Alaska and northern Canada as a huge carbon "sink," or depository that captures and contains the growing amount of carbon released into the atmosphere, much like the rainforests in the Southern Hemisphere.
But the new study shows that just the opposite appears to be happening among stands of white spruce trees, Barber said. The longer summers and hotter days baking the Interior since the 1970s have left gardeners glowing, but trees groaning.
"If this limitation in growth due to drought stress is sustained, the future capacity of northern latitudes to sequester carbon may be less than currently expected," Barber explained in the Nature article.
Another problem, Juday said, is that stressed spruce trees are more susceptible to destruction by other organisms like fungal invasions and spruce budworm attacks. In addition, dried-out trees provide prime fuel for wildfires. Destruction of the spruce trees would put even more carbon into the atmosphere, and might open up more room for hardwood competitors like quaking aspens and paper birch to grow where the white spruce once did.
"White spruce store more carbon than hardwoods like poplar and aspen because they are older," Barber said. "The younger trees live fewer years and grow faster, but with less capacity for storage."
White spruce, which grow in boreal forests that span across Alaska and Canada, typically reach 80 to 100 feet high and up to three feet in diameter. The tree's full, pyramidal shape makes it a popular choice for a Christmas tree with families throughout the state.
Commercially, white spruce is often used for pulpwood, lumber and furniture. It has also been used as sounding boards for pianos and violins. Although drought conditions spell bad news for white spruce growth with possible repercussions to other species, there is some good news-- spring seasons, like this year's in the Interior, that are loaded with precipitation.
"A rainy spring may be bad for people, but it's good for the white spruce," Finney said. "On whole, this is the best spring these trees have had in the past 20 years."
CONTACT: Val Barber, School of Fisheries and Ocean Sciences, at 907-474-7899, or Doug Schneider, Alaska Sea Grant College Program, at 907-474-7449.
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