HR: 11:20h
AN: PP52A-05    [Abstracts]
TI: Reconstructing Terrestrial Biospheric Responses and Feedbacks to Past Climatic Change
AU: * Williams, J W
EM: jww@geography.wisc.edu
AF: Dept of Geography University of Wisconsin, 550 N Park St, Madison, WI 53706
AU: Shuman, B N
EM: bshuman@geog.umn.edu
AF: Dept of Geography University of Minnesota, 414 Social Sciences Bldg, Minneapolis, MN 55455
AU: Webb, T
EM: thompson\_webb\_iii@brown.edu
AF: Dept of Geological Sciences Brown University, 324 Brook St, Providence, RI 53704
AB: Since CLIMAP, paleoecological records have primarily served as proxies of past climatic variation. As the IPCC mission shifts from climate change detection and attribution to prediction and mitigation, paleoecological records are increasingly valuable for studying the behavior of ecological systems at levels of organization from populations to biomes, and the responses and feedbacks of these systems to atmospheric variability. The expanding availability of isotopic and other physically based paleoclimatic records provides an independent climatic framework for interpreting paleoecological data. Moreover, dynamic vegetation models coupled to general circulation models allow biosphere-atmosphere feedbacks to be assessed and model comparisons to paleodata to be carried out at ecological units ranging from plant functional types to biomes. Fossil pollen data remain the primary source of information about late-Quaternary vegetation dynamics, complemented by plant macrofossils, phytoliths, charcoal, carbon isotopes, and molecular techniques. Here we review 1) recent work mapping late-Quaternary vegetation history in North America at 1000-year intervals at the level of plant taxa, broadleaved and needleleaved woody cover, leaf area index (LAI), and biomes, 2) time-series of climate and woody cover for selected sites, and 3) the application of these datasets to providing boundary conditions and assessing general circulation and vegetation models. Biomes emerge from the individualistic behavior of plant taxa, with a widespread increase in tree cover and LAI since the last glacial maximum and rapid shifts of the prairie-forest ecotone during the Holocene. Likely feedbacks include positive hydrological feedbacks along the prairie-forest boundary, increased carbon sequestration, and enhanced albedo seasonality with the expansion of broadleaved deciduous forests.
DE: 9350 North America
DE: 3322 Land/atmosphere interactions
DE: 3344 Paleoclimatology
DE: 0400 Biogeosciences
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting