Natural decay resistance of heartwood from dead, standing yellow-cedar trees : Laboratory evaluations

Yellow-cedar trees have been mysteriously dying for more than a century in southeast Alaska. As these stems continue to stand for decades in the forest, foliage, twigs, and branches deteriorate. The sapwood in the stem degrades, leaving columns of essentially heartwood standing like ghosts in the forest until they eventually drop. To estimate the potential for utilization of these trees, several experiments have been initiated to characterize the natural durability of heartwood from dying and dead yellow-cedar trees. The objectives of this study were to characterize the durability of heartwood in living and dead stems using standard American Society for Testing and Materials procedures and to determine if durability of heartwood differs between living and dead trees, with tree size, with position relative to pith, and with years following tree death. Results from this study indicate that the heartwood from live trees and from snag class III trees was resistant to attack by G. trabeum. Heartwood from smaller diameter trees in snag class V was moderately resistant to G. trabeum, but heartwood from the larger diameter trees in snag class V was not. Heartwood of live and dead yellow-cedar trees was not resistant to decay by Postia placenta and Serpula himantioides. Results also suggest that the natural durability against decay fungi of clear heartwood from living yellow-cedar trees and from yellow-cedar trees that have been dead less than 80 years is adequate to have practical application for products used aboveground and subjected to intermittent wetting.