Fire and Forest History from Soil Charcoal in Yellow Pine and Mixed Hardwood-Pine Forests in the Southern Appalachian Mountains, U.S.A.

The Holocene history and ecological role of fire in forested ecosystems in the southern Appalachians is incompletely known. Determining how often and when fire has affected forest communities requires us to think about fire over time scales that extend beyond those of written fire records. This research is the first to specifically address the spatio-temporal patterns of forest fires in southern Appalachian xeric forests using radiocarbon dating of taxonomically identified soil charcoal as the primary proxy. Forty-eight soil cores were recovered in eight sites established for a companion study of dendrochronological evidence of fire history. The eight sites were located in three study areas in the western portion of Great Smoky Mountains National Park. Macroscopic charcoal was isolated from core increments by wet sieving to provide samples for taxonomic identification and radiocarbon dating. Three of eight sites produced soil cores that varied significantly in charcoal mass, suggesting the influence of spatially patchy fires, bioturbation, or overland movement of charcoal. Seven of eight sites exhibited a significant and strong negative correlation between charcoal mass and depth in the soil column; however, charcoal fragments were not preserved in chronological order. A fire chronology (9649 to 107 cal yr BP, based on weighted means of calibrations) was developed from radiocarbon dates on 122 taxonomically identified charcoal fragments. Charcoal from six categories is represented in this study: southern yellow pine, mesic conifer, undifferentiated pine, chestnut, oak, and elm. Southern yellow pine charcoal is most common for all study areas, yet mesic conifer charcoal is also well represented, suggesting that the current period of “mesophication” may not be unique in this ecosystem. Soil charcoal from shallow core increments (0–10 cm) was compared with current forest inventories to determine the robustness of soil charcoal as a proxy for past forest vegetation, the results of which show limited potential for application in the western portion of Great Smoky Mountains National Park. The results from this study provide the first stand-specific evidence of prehistoric fire and forest composition for southern Appalachian yellow pine and mixed hardwood-pine forests.