Yellow-cedar (Callitropsis nootkatensis D. Don; Oerst. ex D.P. Little) is an economically and ecologically important tree species that is experiencing high rates of growth decline and mortality in northwestern North America’s temperate rainforest. This ongoing tree dieback has been considered a prime example in how global change affects forest health and may prove as a bellwether in future forest decline as climate changes accelerate. As a result of this dieback, many stands of yellow-cedar trees in Southeast Alaska contain numerous standing, dead snags. Snag-age estimates based on morphology have been used to support the interpretation that a warming climate after ca. 1880 triggered unprecedented yellow-cedar dieback. In addition, growth declines have been used to determine the onset of root dieback episodes that have been linked to dieback in individual trees. Here we present: 1) new estimates of yellow-cedar snag longevity by cross-dating 61 snags with morphologies that suggest they stood dead for extended periods, and 2) quantify the timing of growth declines in healthy, dead, and declining yellow cedar trees. Results indicate that ~59% of yellow-cedar snags that lost their branches to decay have remained standing for > 200 years, and some for as long as 450 years (snag longevity mean ± SD: 233 ± 92 years). Preliminary results suggest that growth declines in dying yellow-cedar trees occur decades prior to snag formation, and during certain prehistoric climate conditions. These findings, along with supporting evidence from historical photos, dendrochronology, and snag-morphology surveys in the published literature suggest that episodes of yellow-cedar dieback also occurred before 1880 and before significant anthropogenic warming began. The roles played by climate change in these earlier forest dieback events remain to be further explored.
