Effects of Fire and Thinning on Shrub Composition in Red Pine Forest Communities of Wisconsin

Red pine (Pinus resinosa) woodlands have been influenced by lightning ignited fires and fires of indigenous peoples for thousands of years. However, little is known about historic frequency and seasonality of fire in red pine stands. We examined fire frequency during three functional time periods; pre-European settlement (pre 1880), settlement (1881 to 1943), and suppression (1944 to present) in northern Wisconsin, USA. A total of 50 cross-sections from living and dead pines were examined for fire scars on two sampling sites (Treehaven and Bradley Park, Tomahawk, Wisconsin, USA). Standard cross-dating procedures were used to assemble two independent fire chronologies dating to 1832 and 1784 A.D. We found similar Mean Fire Intervals (MFI) at two sampling sites during the pre-settlement period (MFI = 5.1 years for Treehaven and 8.2 years for Bradley Park). Our results show divergent trends in fire history at each sampling site during the settlement period with the Treehaven MFI decreasing to 3.3 years and the Bradley Park MFI increasing to 16.0 years. No fire intervals were recorded at either site during the suppression period. Fire primary took place in early season (95% of samples) with the exception of one late season and one growing season fire event. The change in fire regime closely coincided with forest community changes in the Northern Highlands Ecological Landscape.University of Wisconsin-Stevens Point College of Natural Resources, and the USDA McIntire-Stennis Progra