Fire in Southern Appalachians: Fuels, Stand Structure and Oaks

Managers responsible for maintaining the diversity and productivity of Southern Appalachian forests are increasingly turning to prescribed fire as an important management tool in oak dominated forests. The decision to use fire with increasing frequency and spatial extent is based, in part, on an emerging sense of the prehistoric significance of fire in this landscape and its potential to control the proliferation of fire-sensitive competitors in contemporary forests. While it is well documented that fire has been an important ecological force in Southern Appalachian forests for a very long time, there has been little research to demonstrate that prescribed fire effectively controls fire-sensitive competitors, promotes regeneration of desirable species, or maintains and promotes healthy forest stands. In the face of increased management burning there is a need to address these questions, and to quantify the role of existing and residual fuels in fire management following repeated fire of differing intervals. Two studies were initiated in 1995 and 2002 in upland forests on the Cumberland Plateau of Kentucky to examine the effectiveness of prescribed fire to maintain oak dominance by altering stand structure and enhancing oak seedling establishment and development. We hypothesized that fire would: (1) reduce midstory stem density, and that these changes to stand structure and light availability would lead to improved performance of oak seedlings; and (2) control oak competitors. On ridgetop sites on the escarpment of the Cumberland Plateau, we measured stand structure and tree regeneration on 48 plots in 6 treatment areas over an 11-year period. Four units were burned 3-4 times and two units serve as fire-excluded references. On the topographicallydissected landscape of the Cumberland Plateau we recorded stand structure and multiple aspects of the tree regeneration process on 9 study sites (93 plots), with three sites burned four times, three sites burned twice, and three fire-excluded sites. Prescribed fire reduced midstory stem density and basal area, and increased light availability which was transitory due to understory sprouting. Seedling population studies revealed that oaks and maple seedlings responded to stem kill by re-sprouting, with increased height and diameter. However, red maple seedlings grew more than oaks after burning. Burning reduced seedling density of potential competitor species, yet high fecundity of some species (e.g., red maple) and strong sprouting response of others (e.g., sassafras), suggests that multiple fires have provided neither the stand structural changes nor competition control that would lead to the development of more competitive oak advance reproduction. An oak mast event revealed a potentially positive role for fire in reducing the depth of the litter layer and enhancing oak seedling establishment and growth. Overall, our results suggest a modest role for prescribed fire in enhancing the establishment, growth and persistence of oak advance regeneration.