Document: LOU-3-17-4

Potential changes in tree species and forest communities with climate change in the Eastern U.S.

IVERSON, L.R.* ¹, A.M.PRASAD ¹ and M.W.SCHWARTZ ²

USDA Forest Service, Northeastern Research Station, Delaware, OH ¹
Dept. Environmental Science and Policy, University of California, Davis, CA ²

Abstract:
Potential changes in tree species and forest community types were evaluated for the eastern United States, according to five scenarios of possible future climate resulting from a doubling of atmospheric carbon dioxide. An empirical model DISTRIB, which uses a regression tree analysis approach, was used to generate suitable habitat, or potential future distributions, of 80 common tree species for each of the scenarios. The DISTRIB model assumes the vegetation and climate are in equilibrium with no barriers to species migration. Besides 80 individual species models, combinations of the individual species outcomes yielded the ability to estimate species richness (from among the 80 species) and forest type (from simple rules) for each of 2100 counties in the eastern U.S. Depending on the scenario used, roughly 35 of the species were modeled to expand their range or importance at least 10%, while another 31 could decrease by at least 10%. Overall, average species richness across all counties could increase slightly among the 80 species. With forest types, dramatic changes were modeled. All five scenarios depict a complete extirpation of the spruce-fir forest types from New England. Outputs from only the two least severe scenarios retain any aspen-birch, and they are largely reduced. Maple-beech-birch also shows a large reduction in area under all scenarios. On the other hand, oak-hickory and oak-pine types were modeled to increase significantly. A cellular automata model, SHIFT, was used for selected species to simulate migration over the next 100 years through the fragmented landscapes of the eastern U.S. Model outputs show that potential migration distances and rates are controlled by the habitat quality into which the species are migrating, and by the current abundance of the species. Though many assumptions are made, these modeled outcomes substantially agree with a limited number of predictions from researchers using either paleoecological data or other models.

Keywords: climate change, migration, biodiversity, DISTRIB, SHIFT

This abstract is being presented at: 9:30 AM in session:
Symposium # 20: Global Change in Forests: Interactions Among Biodiversity, Climate and Land Use.