PARENT SESSION
Contributed Oral Session 77: Paleoecology
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 515 A, Level 5, Palais des congrès de Montréal

Taxonomic resolution and the postglacial history of the forests of eastern North America: Analysis from the North American Pollen Database.

Finkelstein, Sarah^*,1, Gajewski, Konrad¹, Viau, Andre¹, ¹ University of Ottawa, Ottawa, Ontario, Canada

ABSTRACT- Fossil pollen is used to reconstruct Holocene tree migrations and long-term ecological dynamics. A limitation of many pollen studies is the low taxonomic resolution at which pollen types are identified; frequently only genera can be studied. Since species within a genus are known to vary in ecological affinities, this limitation lessens the potential of pollen data in studies of landscape-scale forest dynamics. Although species- or subgeneric-level determinations are sometimes taxonomically possible (e.g. Acer, Fraxinus and Juglans) these are not always plotted or analyzed. The objective of our study is to determine whether species-level pollen identifications within the genera Acer, Fraxinus and Juglans can improve upon regional-scale studies of paleo-forest dynamics. We extracted data from the North American Pollen Database (NAPD) for sites in eastern North America for which species-level identifications have been recorded within the genera of interest. A first question was: have subgeneric-level identifications been made at a sufficient number of sites that these data can be mapped or studied? Analysis of the modern distribution of these data indicates a cautious yes, although the lack of distinction in many sites renders the analysis difficult. Within each of three selected high-resolution sites, ordinations indicate that individual species of Acer, Fraxinus and Juglans follow different trajectories through the Holocene. Therefore, grouping species-level pollen counts into generic categories results in the loss of ecologically valuable information. Regional scale comparisons of pollen percentage curves through the Holocene for a given species indicate that it is reasonable to conclude, considering the errors associated with the low resolution and insecure chronologies for many sites in the NAPD, that individual species of Acer, Fraxinus and Juglans responded synchronously to paleoclimatic changes within each region. We confirm that pollen datasets contain additional meaningful information than is commonly analyzed and conclude that increasing the taxonomic resolution to the maximum extent possible given current knowledge will improve the next generation of pollen studies.

Key words: pollen analysis, eastern North America, forest dynamics, Holocene