PARENT SESSION
Poster Session #15: Paleoecology.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
147
Climate, fire, and vegetation change over the past 10000 years at two sites along the prairie-forest border in south central Minnesota.
UMBANHOWAR, CHARLES1, CAMILL, PHIL*,2, TEED, BECKY3, GEISS, CHRISTOPH4, DVORAK, LEAH1, KENNING, JON2, LIMMER, JACOB2, WALKUP, KRISTINA1, 1 St. Olaf College, Northfield, MN2 Carleton College, Northfield, MN3 University of Minnesota, Minneapolis, MN4 Trinity College, Hartford, CT
ABSTRACT- Responses of vegetation and fire to climate change are tightly linked as a result of strong feedbacks between fuels and vegetation structure. We analyzed pollen, charcoal, sediment magnetic, and LOI properties for Kimble Pond and Sharkey Lake, two small glacial lakes in south-central Minnesota that provide a continuous high-resolution record of paleoclimate throughout the Holocene. Both lakes were dominated by a non-analogous Ulmus-Ostrya assemblage (forest) ~9000-10000 BP (cal. 14C), shifted gradually to prairie (Poaceae-Ambrosia-Artemisia) ~8000 BP, and finally back to a Quercus dominated (woodland/savanna) assemblage ~3000-4000 BP. Charcoal flux rates showed an increase from an average of 0.7-1.0 mm.cm-2.yr-1 during the forest period to 2.0-3.0 mm.cm-2.yr-1 during the prairie period and again increased to 4.0-5.0 mm.cm-2.yr-1 at the start of the woodland/savanna period. LOI and rock magnetic data suggest changes during this period towards wetter and more productive conditions. Our study suggests that, as a result of the influence of climate on fuel productivity, changes in fire frequency may be the result and not the cause of shifts in vegetation. However, fire frequency may still be a controlling factor on rates of vegetation change.
KEY WORDS: Bigwoods, climate change, fire ecology, pollen