Wednesday, August 4, 2010: 4:00 PM
301-302, David L Lawrence Convention Center
Background/Question/Methods
Using fires scars from stumps and remnant pieces of wood, we determined the fire history of a broad area of the landscape of the Huron Mts. in the Upper Peninsula of Michigan, along the shoreline of Lake Superior. The landscape is highly variable, consisting of forests underlain with granite on some of the higher elevations contrasted with outwash plain sands and former dunes, lake terraces and plains near Lake Superior. In order to understand the importance of fire as disturbance, we established study sites in several forested areas: a granite knob currently dominated by mixed hardwoods and conifers, lake plains and terraces with forests dominated by jack pine and red pine, an interior lakeshore dominated by red pine, as well as red pine forests that comingle with mixed hardwoods, white pine and hemlock. We used red pine remnants, stumps and snags at all sites. Results/Conclusions
The entire tree ring record across the eight sites sampled spans the years from 1440 to 2007. Fires were evident across a 440 year period, from 1510 to 1950. The mean fire interval (MFI) varied from 12.8 years on a granite mountain to >30 years near lowerslope positions at interior lake shores. The MFI at the lake plains and terraces sites near Lake Superior was 26 years; however each fire scarred 80-90% of the samples, suggesting that fires were spatially extensive. In the early 1800’s, annual fires were common in the higher elevations, but few trees were scarred by any one fire, suggesting that the fires were neither intensive, nor spatially extensive. On the granite mountain, trees approaching 400 years of age were killed by an anthropogenic fire in the 1890’s, indicating that there were centuries where fires may have killed a few trees, but fires were largely inconsequential as mortality agents and stand restructuring events. In contrast, cohorts likely developed with stand replacing fires on the forests nearest Lake Superior. Fire history at this area reflects strong human influences starting ca. 1750.
The entire tree ring record across the eight sites sampled spans the years from 1440 to 2007. Fires were evident across a 440 year period, from 1510 to 1950. The mean fire interval (MFI) varied from 12.8 years on a granite mountain to >30 years near lowerslope positions at interior lake shores. The MFI at the lake plains and terraces sites near Lake Superior was 26 years; however each fire scarred 80-90% of the samples, suggesting that fires were spatially extensive. In the early 1800’s, annual fires were common in the higher elevations, but few trees were scarred by any one fire, suggesting that the fires were neither intensive, nor spatially extensive. On the granite mountain, trees approaching 400 years of age were killed by an anthropogenic fire in the 1890’s, indicating that there were centuries where fires may have killed a few trees, but fires were largely inconsequential as mortality agents and stand restructuring events. In contrast, cohorts likely developed with stand replacing fires on the forests nearest Lake Superior. Fire history at this area reflects strong human influences starting ca. 1750.