Death Rates In Alaskan Yellow Cedars Accelerating - Juneau Empire

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The cedars, which have been used for centuries by Alaska Natives for totem poles and canoes, are now thought to contain oils that could be used to repel mosquitos and other pests. In chip form, the tree also could help prevent the spread of sudden oak death - a disease that has killed thousands of trees in California.

Yellow cedar (Chamaecyparis nootkatensis ) is highly valued as a timber product and is often used by engineers for hardy structures such as bridges and building beams, said U.S. Forest Service scientist Paul Hennon. Hennon, who is based in Juneau, has done considerable research into the decline in Alaska's yellow cedar stands. For the past 100 years, more than half of the trees within the 500,000 acres of the Tongass National Forest have died, according to the U.S. Forest Service.

Hennon and others have linked the decline to climate change. With warmer temperatures and lower rates of snowfall in late winter and early spring, some scientists theorize that the tree's shallow roots are being exposed to blasts of cold air, killing them in their prime.

It's the notoriously strong trees' "Achilles heel," Hennon said. He said it's particularly surprising considering the tree's natural defenses against decay. When yellow cedars die, they can remain standing for decades without decaying. The reason has been attributed to the composition of oils and their compounds within the tree's core, the "heartwood," which are slowly altered after the tree dies. U.S. Forest Service scientist Rick Kelsey, based in Corvallis, Ore., said it was only common sense to explore whether any practical use could be found for the hyper-defensive trees. "It is kind of like a no-brainer in some regards. The snags remain fairly decay resistant until 80 years after they die," he said.

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http://juneauempire.com/stories/010707/loc_20070107013.shtml