Initial vegetation response to prescribed fire in some oak-hickory forests of the South Carolina piedmont

Three upland hardwood stands on first-order stream drainages in the Clemson University Experimental Forest near Clemson, South Carolina were burned in March 1999 and sampled for vegetation in May and June 1999. Comparison of burned and unburned plots showed significantly greater tree seedling abundance and an interactive effect between slope position and prescribed fire where the effect of fire on groundcover and tree seedlings differed by slope position. The increase in seedling abundance on burned plots was driven almost entirely by an 84-fold increase in yellow-poplar (Liriodendron tulip-ifera L.) seedlings. Red oak (Quercus spp.) abundance was greater on mid- and upper-slope positions on burned plots, but white oak (Q. alba L.) abundance was lower in burned plots at every slope position. Abundance of herbs, shrubs, and vines was nearly 10% greater on burned plots. Prescribed fire caused community-level changes for seedlings and groundcover vegetation. Seedling species diversity and evenness were relatively low at lower slope positions because of the copious germination of yellow-polar, but increased at higher slope positions. Conversely, groundcover diversity and evenness was relatively low on upper slope positions due to the abundant sprouting of lowbush blueberry (Vaccinium vacillans Torrey). Overall, groundcover diversity and evenness were higher for lower slope positions. Groundcover diversity was significantly altered by the interaction of prescribed fire and slope position. Results of this study suggest that one low-intensity prescribed fire in upland hardwood stands can alter tree regeneration patterns and composition of the groundcover layer at least temporarily, but its potential for the long-term promotion of oak-hickory regeneration and suppression of mesic hardwoods on these sites remains unclear. A program of periodic bums will be necessary to restore oak-hickory forests in fire-suppressed upland hardwood stands.