PARENT SESSION
Poster Session #22: Paleoecology.
Wednesday, August 8, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Simulation of the impact of fire on the location and structure of the Prairie-Forest border in Minnesota.

Umbanhowar, Charles¹, Werner, Brett¹, ¹

ABSTRACT- The location of the Prairie-Forest Border has shifted dynamically over the past 10,000 years, reflecting the effects of climate on fire and vegetation, mediated on a local scale by topography. Paleoecological studies have revealed the broad outlines of these interactions but lack the temporal and spatial resolution to address more specific questions about fire frequency and changes in fuel-loading. We used LANDIS, a spatially explicit landscape model, to simulate the effects of changes in fire frequency in the Bigwoods region (4 x10⁶ ha) of central Minnesota. The Bigwoods was a mesic, deciduous forest surrounded by oak-aspen woodland and prairie. A total of 12 common species were modeled, including Ulmus americana, Acer saccharum, Tilia Americana, Quercus macrocarpa, and more generic taxa such as "grasses". Initial distributions and relative abundances for taxa were based on Government Land Office data and model runs were for 500 years. Exclusion of fire resulted in the rapid spread (< 60 years) of Populus into prairie areas followed by a dispersal-limited expansion of Ulmus and Acer. Addition of frequent fires (mean return interval = 100) resulted in the rapid dominance of Quercus and the restriction of Acer and Ulmus to small areas surrounded by water. In general, responses to changes in fire return interval were strongly mediated by assumptions about fuel loading and time since last fire, highlighting the need to consider feedbacks between vegetation and fire when considering the impacts of climate change.

KEY WORDS: prairie-forest border, fire frequency, simulation, LANDIS