Regeneration Patterns in Canopy Gaps of Mixed-Oak Forests of the Southern Appalachians: Influences of Topographic Position and Evergreen Understory

Abstract

-Canopy gaps in southern Appalachian mixed-oak forests were assessed for the effects of topographic, gap and stand variables on density of wood seedlings. Seedling density was significantly correlated with percent slope and positively with gap age (1-5 yr). Density varied substantially among topographic positions and increased with gap size. Species richness decreased over time and increased with gap size. Regeneration was dominated by Acer rubrum L. Other important species included Quercus coccinea Muench., Q. rubra L., Q. velutina Lamarck, Liriodendron tulipifera L. and Cornus florida L. Some known gap species increased in density with increasing gap size. Competitive inhibition effects of the evergreen understory (Rhododendron maximum L. and Kalmia latifolia L.) were also examined. Gaps containing over 50% cover of R. maximum had significantly lower densities than all other gaps, including gaps with >50% K latifolia cover. Height distributions of major regenerating species were skewed away from small (<15 cm) height classes. Species establishment was a function of gap area, gap age, topographic position and cover of R. maximum. In addition, species of varying degrees of tolerance of understory conditions are capable of establishment in small to medium size canopy openings in the absence of an evergreen shrub understory.