Response of southern Appalachian table mountain pine (Pinus pungens) and pitch pine (P-rigida) stands to prescribed burning

Southern Appalachian table mountain pine (Pinus pungens) and pitch pine (P. rigida) forests require disturbance for regeneration. Lightning-ignited fi res and cultural burning practices provided the disturbance that prehistori cally and historically maintained these forests. Burning essentially ceased on public lands in the early twentieth century when fire suppression becam e the primary fire management initiative of federal land managers. The last five to six decades of forest succession in the absence of fire have allow ed chestnut oak (Quercus prinus), scarlet oak (Q. coccinea), and red maple (Acer rubrum) to dominate both midstory and understory strata and to become poised to invade table mountain pine and pitch pine canopies. This study e xamined first-year responses of three 60-80-year-old southern Appalachian t able mountain pine and pitch pine stands to prescribed fire. Prior to burni ng, mean canopy (woody stems greater than or equal to 2.5 cm DBH), understo ry (all shrubs and saplings <2.5 cm DBH), and ground layer (all vascular sp ecies less than or equal to 1 m in height) species richness values ranged 6 -8 species/0.02 ha, 2-3 species/0.01 ha, and 1-3 species/m(2), respectively . Mean pre-burn basal area ranged from 23 to 32 m(2)/ha for the three stand s. Canopy and understory densities averaged 1500-1900 and 70-120 stems/ha, respectively Mean pre-burn ground layer cover ranged from 28 to 77% per met re square. There were no pine seedlings present in the pre-burn ground laye r. On all sites, burning top-killed some overstory and midstory fire-intole rant species such as sassafras (Sassafras albidum), red maple, and white pi ne (Pinus strobus). Numerous sprouts of these species appeared in the post- bum understory and ground layers. Canopy species richness was significantly lower (45%) whereas understory and ground layer species richness were sign ificantly higher (two times pre-burn values) following most bums. All three bums significantly reduced canopy basal area (20-30%), canopy density (50- 70%), and ground layer cover (40-70%) but increased understory density (two times pre-burn values). Table mountain pine (8000 seedlings/ha) and pitch pine regeneration (15 000 seedlings/ha) was observed following two of these burns but the seedlings were not likely to survive due to shading and comp etition from overstory, midstory, and understory strata. Future burns to re store similar stands must open the forest canopy, reduce accumulated litter and duff layers, and expose regenerative basal buds of hardwoods to lethal temperatures in order to lessen post-bum sprouting. Prescribed bums that d o not accomplish these goals may further encourage succession towards hardw ood-dominated stands as sprouts of understory hardwoods grow into midstory and overstory strata. (C) 2000 Elsevier Science B.V. All rights reserved.