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Wednesday, April 11 • 10:00am - 10:15am
CLIMATE CHANGE EFFECTS AND ADAPTATION: Multi-Scale Climatic and Topographic Characteristics of Low-Snow Mortality and Regeneration in Yellow-Cedar Suggest Directional Change in Forest Composition

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AUTHORS: Sarah Bisbing*, Department of Natural Resources & Environmental Sciences, University of Nevada -Reno; Brian Buma, Department of Natural Sciences, University of Alaska-Southeast; Lauren Oakes, Emmett Interdisciplinary Program in Environment & Resources, Stanford University; John Krapek, Department of Natural Sciences, University of Alaska-Southeast; Allison Bidlack, Alaska Coastal Rainforest Center, University of Alaska-Southeast; Matthew Brousil, Department of Entomology, Washington State University

ABSTRACT: Climate change is altering the conditions for tree recruitment, growth, and survival, and range shifts are widely anticipated under novel temperature and precipitation regimes. Local adaptation to historical climate will leave species maladapted to ongoing and predicted changes in climate, and these mismatches are likely to be most extreme for seedlings, which have a narrower range of tolerance than mature individuals. The shifting climatological niche of mature trees and the regeneration niche relevant to recovery may lead to life-history mismatches. These mismatches may lead to significant changes in forest composition wherever climate change results in increased mortality. In a well-studied case, the decline of yellow cedar (Calliptropsis nootkatensis) across southeast Alaska and British Columbia has been linked to declining snow coverage and resultant root freezing. Little is known about regeneration dynamics across the area of decline nor on climatic drivers of mortality across varying spatial scales. To address these knowledge gaps, we sampled plots over a 5 degree latitude range to ask: 1) What climatic and community factors are associated with mortality and regeneration at fine scales?, 2) Does seedling community composition correlate with patterns of mortality?, and 3) Is forest composition stable, or in the process of a decline-induced shift? Mortality in mature individuals was closely tied to climate and slope, with proportion dead higher in areas with higher winter precipitation and higher temperatures. Regeneration was related to overstory health, and areas of high decline had the lowest abundances of yellow cedar regeneration. In these areas, yellow cedar regeneration was replaced by hemlock (Tsuga spp.), and seedling community composition was best explained by winter temperatures, slope, and regional climate. Our results also suggest that yellow cedar forests are experiencing a decline-induced shift in community composition, which is likely to lead to a directional shift from yellow cedar to hemlock dominance.

Wednesday April 11, 2018 10:00am - 10:15am CDT
LaSalle 1 (7th Floor)