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Monday, April 9 • 2:00pm - 2:15pm
SYMPOSIA-01: Processes Controlling the Pattern of Presettlement Vegetation in the Landscape of the Southern Tip of Lake Michigan

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AUTHORS: Noel Pavlovic*, U.S. Geological Survey; Marlin Bowles, The Morton Arboretum; Samniqueka J. Halsey, University of Illinois; Jennifer McBride, The Morton Arboretum

ABSTRACT: Understanding how landscape processes shaped North American vegetation prior to European settlement is critical for restoring biological diversity and understanding how shifting climate will alter biome transitions. Climate, soil characteristics, and fire are thought to have shaped local and regional vegetation pattern and oak dominance in the Prairie Peninsula. Quantitative geographical analysis of 1830’s Government Land Office (GLO) Public Land Survey data along the south coast of Lake Michigan, from southeast Wisconsin to southwest Michigan, has been limited due to the lack of analytical datasets.GLO vegetation pattern and structure was compared against a fire model, in which we expected a non-random vegetation pattern, with regional oak dominance and a greater abundance of shade-tolerant fire-intolerant woody vegetation associated with landscape fire breaks. Tree cover and composition were compared among physiographic regions and in relation to gradients in soil types, precipitation, evapo-transpiration, fire proxies, and soil moisture.The landscape was dominated by prairie in the southwest, with increasing tree cover to the north and east. Greater extent of tree cover, as well as forest tree density (> 100 trees/ha), occurred on the lee side of major water courses. Savanna (< 50 trees/ha) tended to be less restricted and became dominant along the northern and eastern Prairie Peninsula border. Oaks dominated all woody vegetation, with greater sub-dominance of maple-basswood-ash vegetation at higher tree densities. Correlates of individual tree distribution included distance from water courses, slope and elevation. High abundance of barrens in the eastern portions of Indiana are notable. These results support regional models of fire-caused and soil moisture-controlled local vegetation patterns, and the need for incorporating fire into management planning as well as recognizing fire as a factor in climate change modeling. We will discuss these transitions in relation to fire breaks, climatic gradients, and conservation.

Monday April 9, 2018 2:00pm - 2:15pm CDT
Hancock Parlor