Fire Regimes of Xeric-oak Pine Forests

While ecologists disagree to what extent fire shaped other forest types in the Southern Appalachians, there is general agreement that fire was a very important component of the xeric oak-pine forests along the southern slopes and ridges. Although southern Appalachian forests likely did not burn as frequently as the pine-grasslands of the adjacent Piedmont and Coastal Plains, several authors assert that the frequency of lightening-caused fires was sufficient to maintain oak-pine forests (Whittaker 1956, Zobel 1969, Komarek 1974, Barden and Woods 1976, White and Lloyd 1997). This natural fire regime was greatly increased when native Americans arrived in the region. Pollen records from pond and bog sediments indicate that anthropogenic fires increased populations of fire-tolerant oaks, chestnut, and pines in upland forests of the southern Appalachians (Delcourt et al.1986, Delcourt et al. 1998, Delcourt and Delcourt 1997). 

Anthropogenic fire regimes that characterized the southern Appalachian landscape began to change with the settlement of Europeans in the 16th century.  European settlement had a devastating effect on the Native American population, and indirectly decreased the influence of anthropogenic fires. Native Americans of the l6th-18th centuries continued to influence landscape conditions, albeit on a much smaller scale. Despite this decrease in fire set by native Americans, anthropogenic fires still affected the Southern Appalachians to a large extent during the 1700-1800s since the European settlers that moved into the region during that time adopted the firing practices of the Indians (Pyne 1982). It wasnt until the fire suppression era of the early 1900s that fire was essentially removed as a vector for shaping landscapes in the southern Appalachian region. For example, the creation of the Great Smoky Mountains National Park (GSMNP) in the 1930s altered fire frequencies from once every 10-40 years (from the period of 1856-1940) to once every  2000+ years (Harmon 1982).

Effects of fire suppression on oak-pine forests

The highly effective fire suppression programs of the 1900s resulted in a decline of oak-pine forests throughout the southern Appalachian region. Once vast areas of open oak-pine forests in the Great Smoky Mountains National Park (GSMNP) are essentially non-existent today (SAMAB 1996e).   In the absence of periodic fire, forest succession has allowed hardwood species and white pine (Pinus strobus) to invade areas previously dominated by yellow pines on upper elevation, southwest facing slopes. This process has affected two rare forest communities in particular, mountain longleaf pine woodlands and Table Mountain pine/pitch pine woodlands (SAMAB 1996e). In recent years, the pine component of these stands has been furtHer reduced by drought and associated southern pine beetle infestations (Smith 1991). Many oak-pine forests are slowly degrading into poorly stocked stands with dense understories dominated by mountain laurel (Clinton et al. 1993, Swift et al. 1993, Vose and Swank 1993, Clinton and Vose 2000).

While oaks may withstand the absence of fire better than yellow pines, even they loose their competitive ability against shade tolerant and fire intolerant species such as soft maples, white pine, and sourwood (SAMAB 1996e), particularly on more mesic sites.  The loss of oak from these stands has negative implications on wildlife, since acorns are an important food source for black bear, white-tailed deer, wild turkey, and other wildlife species.  

Due in part to fire suppression, most oak-pine ecosystems in the southern Appalachians today are characterized by high overstory mortality and slow growth rates, inhibited regeneration of overstory species, increased density and biomass of mountain laurel in the shrub layer, heavy fuel loads in the forest floor, decreased herbaceous abundance and diversity, and increased susceptibility to insect infestations (Vose 2000). Due to these structural shifts, fire exclusion has increased the likelihood of catastrophic fires in forest ecosystems more adapted to low-severity and -intensity fire. Failure to restore some of these fire-dependent communities will likely result in their permanent loss as ecosystem components since extensive areas that once supported these communities are without a seed source needed for their reestablishment (Buckner and Turrill 1999).