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Collaborators on the study, which compared three-ring data to satellite images, include Glenn Juday, a professor of forest ecology at the University of Alaska Fairbanks, and co-author of the article. "This is one of the first extensive analyses of annual growth and climate response of black spruce in Alaska," said Juday, who collaborated on the UAF research with Valerie Barber, Patricia Heiser and Emily Sousa. The study found that tree growth declined across most of the current area of Alaska boreal forest but increased in a smaller area on the cold margins of the forest.
Scientists at the Woods Hole Research Center and three other institutions based in Alaska and France conducted the study. UAF scientists were instrumental in the project, which involved one of the largest and most widely distributed samples of tree-ring data ever analyzed in Alaska: 839 trees, including 627 white spruce from 46 stands and 212 black spruce from 42 stands.
"The tree rings tell us for sure what's happening on the ground, and the satellite data covers the whole region," said Juday. "Recent temperature increases have reduced tree growth over most of central Alaska, and increased growth in places where the temperature used to be too low for optimum growth, such as the Western Alaska tundra margin. Summer temperatures in central Interior Alaska are now almost too warm for white spruce to survive."
The study is the first time the two sets of data were compared, Juday said. "Every tree ring sample was compared to the satellite data and they mostly agreed. It's particularly impressive that the tree ring and satellite data agree so well. This gives the final piece of assurance that this is real."
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http://www.thecordovatimes.com/article/1109study_illustrates_shifting_alaska_boreal