Issue 9

Oaks, People, and Fire

Natural fire regimes vary significantly across the range of upland hardwood forests in the Southeast. In the Southern Appalachians, fire started by lightning is very infrequent. As we move across the map west into Tennessee, natural fire becomes more frequent-and more frequent still as we move into Arkansas and Missouri. In all of these oak systems, fire is often tied to human activity.

Martin Spetich, upland hardwoods unit research forester and vegetation research team leader based in Hot Springs, AR, is working with Rich Guyette (University of Missouri), Mike Stambaugh (University of Missouri), and Dan Dey (FS Northern Research Station) to develop fire histories using the scars that show up in the growth rings of trees that have survived fire.

Guyette and other researchers examined fire scar data from more than 40 different sites in Eastern North America to document fire regimes in forests with oak. They found that fire frequency was highly variable across the region and from site to site. Sites that burned as frequently as every 2 or 3 years could be found near others that burned once in 20 years. The fire scar data study showed that the major factors controlling fire frequency were human population density, culture, and drought.

A study Spetich and Guyette conducted on the fire history of the Boston Mountains in Arkansas made the human connection more explicit. In general, the researchers found that fire was more frequent during the period when Native Americans and early settlers were in the area, with large fire years strongly tied to climate conditions, especially drought. Once a certain population density was reached in the 1880s, fire became less frequent, with fire suppression becoming the norm in the following decades. A second study by Spetich, Guyette, and Stambaugh over a larger portion of the Boston Mountains further implicated humans as well as short- and long-term climate variability. This may be the first fire history study to directly link a known Native American population to historic fire.

A third study now underway by Guyette, Stambaugh, Spetich, and Dey examines fire in upland forests throughout the Southeast. In this study, the researchers use fire scars to reconstruct historic fire intervals in deciduous and subtropical forests. They can then use the data to develop models to provide information for areas where fire scar data are not available. This project will help fill both spatial and temporal gaps in the fire scar record and provide information to better estimate mean fire intervals at the national level.-ZH