Forest Development in Canopy Gaps of a Diverse Hardwood Forest of the Southern Appalachian Mountains

In a mature hardwood forest of 15 canopy species (l/Xp2 = 7.2) in Great Smoky Mountains National Park, Tennessee, tree replacement in 118 single-tree gaps and 42 multiple-tree gaps was predominantly by species which are tolerant of shading. However, four species of low shade tolerance, Liriodendron tulipifera, Prunus serotina, Quercus rubra, and Fraxinus americana, were able to hold three percent of the canopy area by infrequent capture of gap space, particularly in multiple-tree gaps. Trees of lower tolerance for shade have larger crowns than very tolerant trees. Relative crown sizes were used as weighting factors to improve predictions of a Markov chain model of canopy composition. Tilia heterophylla tended to replace itself by basal sprouts. Liriodendron tulipifera was found as a replacement tree primarily in gaps formed by the fall of Tsuga canadensis.