PARENT SESSION
Poster Session # 4: Paleoecology.

Monday, August 4 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Late-Holocene fire and vegetation history in the Wisconsin pine barrens.

Lynch, Elizabeth^*,1, Calcote, Randy², Hotchkiss, Sara³, ¹ Luther College, Decorah, IA² University of Minnesota, Minneapolis, MN³ University of Wisconsin - Madison, Madison, WI

ABSTRACT- Land managers seeking to restore "pine barrens" ecosystems in northwestern Wisconsin are interested in characterizing pre-European fire regimes. Our objective is to use charcoal and fossil pollen in lake sediments to reconstruct fire and vegetation patterns, and to investigate how fire and vegetation interacted over the past 2000 years. At Ferry Lake we used historical records to determine how known fires are represented in ²¹⁰Pb dated lake sediment, and then reconstructed forest fires for the past 2000 years. Charcoal accumulation rates (CHAR) of macroscopic (125-250 ) fragments in contiguous core samples (each representing 5-10 years) were calculated based on ²¹⁰Pb and ¹⁴C dating. Graminoid charcoal fragments were tallied separately to estimate the relative abundance of grass charcoal over time. CHAR peaks greater than 1.25x background influx rates were used to infer local forest fires. Pollen analysis shows a transition from oak-dominated woodland to a relatively open pine forest or savanna at 1400 ¹⁴C yr BP. The fire regime also changed at this time from a 90-year fire return interval to a regime with shorter return intervals, smaller CHAR peaks, and less graminoid charcoal for 400 years after the vegetation change. Beginning around 1000 ¹⁴C cal yr BP the return interval lengthened and both CHAR and graminoid charcoal influx began a decline that extended to the time of European settlement. Our results demonstrate that even within the last 2000 years the vegetation and fire regime changed at this site and that the vegetation patterns recorded in land survey records from the mid-19th century may not represent typical conditions over the last 2000 years. Restoring pine barrens ecosystem dynamics will require an understanding of the temporal and spatial patterns of vegetation and fire dynamics across the barrens region over thousands of years.

Key words: paleoecology, pine barrens, fire history, Wisconsin