Yellow-cedar research yields prototype for climate change adaptation planning
Adapted from an article by Marie Oliver
Three decades ago, a handful of researchers took on a century-old mystery. Since about 1880, swaths of yellow-cedar were dying across 600 miles of North Pacific coastal rain forest for reasons entirely unknown. At first they suspected a biotic explanation for the species’ death-a fungus, perhaps, or maybe an insect pest. But, when those investigations failed to yield a culprit, they broadened the scope of their work to draw from a range of disciplines. The outcome was not only the successful identification of the cause of yellow-cedar decline, but an interdisciplinary research approach that now holds great promise for evaluating the effects of climate change.
Pacific Northwest (PNW) Research Station pathologist Paul Hennon and soil scientist Dave D’Amore were among the first to study the decline of yellow-cedar, a culturally, economically, and ecologically valuable species. Noted for its strength and resistance to rot, yellow-cedar is coveted for a variety of uses, ranging from totem poles to building materials, so its decline was a serious cause for concern. As a graduate student in the 1980s, Hennon explored biotic cause after biotic cause-including an assortment of insects, fungi, and viruses-but was unable to generate any conclusive results.
Each round of investigation generated more questions than it answered, and so the small project steadily grew into a large research program. Ecologists, soil scientists, hydrologists, ecophysiologists, dendrochronologists, climatologists, and landscape scientists all joined in the investigation. And, when they did, the cause of yellow-cedar decline slowly came into focus.
"We were led by the clues to eventually look at other possible factors, and that was a turning point," Hennon said. "It was never one of our goals to research climate change effects on forests. We just followed the most likely evidence and it turns out that climate change is a central part of cedar death. Before we expanded into a multidisciplinary approach, we only got so far and didn’t solve it. It was only by involving a broader team that we were able to make more progress toward understanding the cause of the decline ."
Ultimately, that interdisciplinary team found that yellow-cedar loss was the result of a complex, "perfect storm" of conditions-a warming climate, reduced snowpack, poor soil drainage, and the species’ unique shallow rooting. These factors lead to fine-root freezing, which eventually kills the trees. "The amount and duration of snow is decreasing in Alaska due to warming temperatures, and cedars provide a clear example of vegetation response to climate change," says D’Amore.
But the scientists’ identification of the cause of widespread yellow-cedar mortality wasn’t the only important outcome of their decades-long investigation, though it was the original motivation. Their long-term, multidisciplinary approach forms the basis for a new conservation and adaptive management strategy, one whose mapping overlays topography, cedar populations, soil drainage, and snow and so enables land managers to pinpoint locations where yellow-cedar habitat is expected to be suitable or, conversely, threatened in the future. The approach brings climate change predictions squarely into management scenarios and can serve as a prototype for evaluating the effects of climate change in other parts of the country.