PARENT SESSION
Symposium 11: How Will the Southeast's Biological Diversity Respond to Climate Change?
Organized by: P White, J Walker, and J Sutter
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Chatham Ballroom B.
Responses to Past Global Change: Biogeographic Change in the Southeastern United States over the Past 21,000 years.
Shuman, Bryan*,1, Jackson, Stephen2, Webb, Thompson3, 1 University of Minnesota, Minneapolis, MN2 University of Wyoming, Laramie, WY3 Brown University, Providence, RI
ABSTRACT- Climate change since the end of the last ice age has had a significant impact on the distribution of plant species in eastern North America. During the last glacial maximum, 21,000 years ago, northern conifers (including one extinct species) dominated the vegetation of the southeastern United States. Temperate and cool-temperate hardwoods also had widespread distributions, but like endemic species, were isolated to locally suitable habitats. Comparisons of sparse fossil pollen and plant macrofossil data from the Southeast with independent paleoclimate data have shown that these plant communities changed dramatically in response to subsequent climate change. For example, an expansion of the southern species of pine (Pinus spp.) in the southeastern United States between 10,000 and 8000 years ago coincided closely with an increase in available moisture that also raised lake levels along the coastal plain. However, a long-term increase in the abundance of many taxa, particularly temperate and northern hardwoods, requires further explanation. Abundance of these taxa increased between 17,000 and 11,000 years ago and maybe related, in part, to the simultaneous rise in atmospheric carbon dioxide content. An important consequence was an increase in the number of locally-dominant tree taxa (and in the evenness of abundance among tree taxa).
Key words: species diversity, vegetation history, climate change, southeastern United States