2018 ESA Annual Meeting (August 5 -- 10)

PS 47-145 - Changes in tree species abundance: 30-year patterns, trends, and potential drivers across the northeastern United States

Thursday, August 9, 2018
ESA Exhibit Hall, New Orleans Ernest N. Morial Convention Center
David J. Gudex-Cross1, Jennifer A. Pontius1, Paul G. Schaberg2 and Alison B. Adams1, (1)Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, VT, (2)USDA Forest Service, Burlington, VT
Background/Question/Methods

Changes in tree species abundance are one potential impact of climate change on forested ecosystems. To date, related studies have largely focused on modeling compositional shifts under various climate scenarios or analyzing site-specific field inventory data to approximate broader changes across landscapes. Here, we leveraged a novel remote sensing technique to model regional changes in the abundance (percent basal area) of eight key northeastern United States species/genera over a 30-year period (1985-2015). For each species/genus, we examined spatiotemporal patterns in abundance and relationships with abiotic factors that might influence competitive trajectories.

Results/Conclusions

We detected significant declines in regional abundance for sugar maple (Acer saccharum, ~12%), eastern hemlock (Tsuga canadensis, ~11%), balsam fir (Abies balsamea, ~5%), and birch species (Betula spp., ~4%). Species that exhibited significant abundance increases included American beech (Fagus grandifolia, ~9%) and red maple (Acer rubrum, ~3%). However, changes often varied by elevation and exhibited significant spatial clustering. For example, red spruce increased primarily across upper elevations of the Adirondacks, concurrent with losses of balsam fir. Increased American beech abundance was often co-located with decreased sugar maple and birch. Several abiotic factors were significantly associated with changes in species abundance, including landscape position (e.g., elevation) and ecologically-relevant climate metrics (e.g., temperature variability, heat loading, and winter temperature extremes), though these relationships varied spatially and by species. Our results indicate climate may be influencing changes in species composition in ways not previously witnessed under traditional successional processes, suggesting potential changes in the long-term composition of northeastern forests.