New hypothesis for yellow-cedar decline links calcium accumulation to nitrogen cycles and rooting depth
Yellow-cedar and western redcedar are two valuable tree species of Pacific Northwest forests. They grow well in wet soils with limited nitrogen-areas where many other species don't. Station scientists formulated a new hypothesis that explains how cedar trees survive in marginal conditions, yet have roots that are susceptible to freezing injury-an occurrence that has killed more than 500,000 acres of yellow-cedar in southeast Alaska. The hypothesis proposes a mechanism whereby cedar trees assimilate nitrogen as nitrate, but must accumulate a counter-ion to nitrate, such as calcium, to control their internal cell pH and provide electrochemical balance. The simultaneous acquisition of calcium and nitrate- requires the trees to maintain shallow roots to acquire nitrate, as nitrification does not occur in the deeper, acidic soils. This may lead to a greater predominance of superficial fine roots of yellow-cedar relative to redcedar, which makes yellow-cedar more susceptible to freezing injury.
The cedar-nitrate hypothesis provides a means to design focused experiments to test this hypothesis and understand the possible successional pathways of cedars related to soil nutrient cycles. The interaction of cedars with soil nutrient cycles expands the potential interactions that must be considered in understanding yellow-cedar decline, as well as the ecology of cedars in general.
Forest Service Partners