Long-Term Fire and Vegetation History from Soil Charcoal in Boone Creek Barrens, Indiana, U.S.A.

This research project used macroscopic charcoal in soil cores to reconstruct the fire and forest history of an historic oak barren in the Interior Low Plateau of the eastern United States. Thirty-two soil cores were recovered from eight plots in five sites within the area of a prior dendrochronological reconstruction of fire history in Boone Creek Barrens, Hoosier National Forest, Indiana. Core increments were wet sieved using a brass sieve with a 2 mm mesh, and retained charcoal fragments were dried, weighed, and randomly sampled for taxonomic identification and radiocarbon dating. Macroscopic charcoal was present in cores from all sites. Total charcoal mass showed a significant negative correlation with depth at all sites. Average charcoal mass per core was significantly less than in previous soil charcoal studies in closed-canopy eastern forests, but the frequency of charcoal presence in 10-cm increments was not statistically different from results at other oak-dominated sites. A 1500-year fire chronology, ranging from 483 to 2000 CE, was developed from radiocarbon dates on 12 taxonomically identified charcoal fragments, extending the dendrochronological fire history for the site by nearly 1200 years. The soil charcoal record provides evidence of at least two fire events occurring prior to the historic period, as well as fires throughout the historic period likely including modern management fires. Charcoal from oak, hickory, chestnut, and undifferentiated ring-porous hardwoods was identified. Oak charcoal from the white oak subgroup was most common. Charcoal from mesic hardwood species currently present at the site was not represented in identified charcoal, suggesting that current mesophytic conditions were not present in the past. Low amounts of macroscopic charcoal in the soil suggest trees were historically scarce and supports the interpretation of the site as a former oak barren.