Effects of Prescribed Burning on Ecosystem Processes and Attributes in Pine/hardwood Forests of the Southern Appalachians

Pine-hardwood ecosystems in the southern Appalachians are in a serious state of decline due to the combined effects of fire exclusion, abusive land practices, and drought related insect infestations. A silvicultural treatment termed "fell and burn" is applied as a best management practice (BMP) in an attempt to restore the diversity and productivity of these ecosystems. A multi-investigator study was initiated to assess the effects of this treatment on ecosystem processes and attributes. Results showed that felling and burning had positive effects on vegetation diversity and nitrogen (N) cycling, while soil erosion rates were unchanged. Losses in total aboveground N pools were larger than observed with other silvicultural practices (e.g., stem only and whole tree harvest) due to the consumption of foliage and forest floor. A more complete assessment will require a long-term approach where potential N additions from N-fixation and other sources are quantified. INTRODUCTION Fire is used as a silvicultural tool in pine-hardwood ecosystems in the southern Appalachians. Stands receiving this treatment typically consist of mixtures of pitch pine (Pinus rigida Mill), scarlet and chestnut oak (Quercus coccinea Muenchh. and Quercus prinus L.), red maple (Acer rubrum L.), and a dense understory of mountain laurel (Kalmia latifolia L.). These ecosystems are most prevalent on xeric sites (i.e., south/west aspect ridge sites). While the pine/hardwood ecosystem is limited in extent (e.g., < 5% of the landscape in the southern Appalachians), it is a unique vegetation type that provides important habitat for both flora and fauna. Changes in pine/hardwood ecosystems in the southern Appalachians have been quite dramatic, particularly in the past 20 years. The combined effects of abusive land practices (e.g., high grade logging, grazing), fire exclusion, and drought have left many of these stands in poor condition. For example, selective logging through the early 1920's has resulted in a sparse (i.e., 200 stems/ha) and low quality hardwood overstory. In addition, pre-suppression wildfires are thought to have played a major role in maintaining a pine component in these ecosystems by providing mineral soil for seed germination and reducing mountain laurel density and vigor in the understory (Barden and Woods 1976, Van Lear and Johnson 1983). Fire exclusion, combined with drought related southern pine beetle infestations, has resulted hi significant reductions in overstory pine and increased mountain laurel in the understory (Smith 1991, Vose et al. in press). These poor conditions have prompted the use of cutting, burning, and planting (referred to as fell and burn) to restore the productivity of these ecosystems.