Using fire to restore pine/hardwood ecosystems in the Southern Appalachians of North Carolina
In the Southern Appalachians, mixed pine/hardwood ecosystems occupy the most xeric sites (i.e., south/west aspect ridge sites). They are typically comprised of varying proportions of pitch pine (Pinus rigida), Virginia pine (Pinus virginiana), and/or shortleaf pine (Pinus echinata) and a mixture of hardwoods, including scarlet oak (Quercus coccinea), chestnut oak (Quercus prinus), and red maple (Acer rubrum). Mountain laurel (Kalmia latifolia), an evergreen ericaceous shrub, is a major component of these ecosystems. While the pine/hardwood ecosystem is limited in extent (e.g., <5 percent of the landscape in the Southern Appalachians), it is a unique vegetation type that provides important habitat for both flora and fauna.
The pine component of many of these pine/hardwood ecosystems is in a serious state of decline. R.N. Smith determined in 1991 that 98 percent of the pine/hardwood stands at the Coweeta Hydrologic Laboratory in western North Carolina have little or no remaining live pine. Smith's study showed that pine has been declining since the early 1970's; however, a major loss of pine occurred in the mid 1980's. This loss is coincident with a severe drought in the region which weakened trees and caused widespread and severe southern pine beetle infestations.
The initial origin of many mixed pine/hardwood stands in the Southern Appalachians is largely a result of past agricultural activities which created microsite conditions conducive to pine regeneration (i.e., mineral soil, limited competition). However, many of these stands are located on sites which could not be cultivated due to steep topography and poor soils, and fire has been advanced as the major factor determining their origin. In either case, the maintenance of pine/ hardwood ecosystems is hypothesized to depend on intense wildfires. Because pine/ hardwood sites are typically dry, hot, and contain substantial quantities of flammable fuels, natural or human-caused fires have the potential for the high intensity fire necessary for pine regeneration. Fire suppression has limited the role of either human-caused or natural fires in perpetuating these ecosystems. While fuel loads in these stands are currently substantial (due to pine mortality and large amounts of mountain laurel), fire suppression efforts will continue to limit the extent of intense wildfires in these ecosystems, even during dry conditions. As an alternative, silvicultural treatments may have equal success in regenerating these stands. Over the past 10 to 20 years, some of these degraded pine/hardwood stands have been chainsaw felled, burned, and planted to white pine (Pinus strobus) in an attempt to increase overall site productivity. As another alternative, the authors have initiated research on the use of prescribed "stand replacement" fires to restore degraded pine/ hardwood stands. In this application, the objective of the fire is to produce a high intensity fire (i.e., a simulated wildfire) sufficient to produce seedbed conditions for pine seed germination and reduce mountain laurel vigor to allow for seedling establishment. This approach has only recently been applied in the southern Appalachians and very little is known about ecosystem responses to this prescription. The authors? objective is to compare the effectiveness of the fell and burn method with stand replacement techniques for restoring pine/hardwood ecosystems in the Southern Appalachians of North Carolina. This is accomplished by comparing pine regeneration and overstory composition among an unburned reference site, a 13-yr-old fell and burn site, a 25-yr-old wildfire site, and a stand replacement fire site. They also briefly compare the effects of burning on aboveground nitrogen (N) pools.