Succession, Sapling Density and Growth in Canopy Gaps Along a Topographic Gradient in a Second Growth East Tennessee Forest

Canopy gaps in a second growth forest in East Tennessee were studied to document succession, sapling species partitioning in individual gaps and possible sapling adaptations for gap colonization. Ten gaps (64 to 309 [m.sup.2], mean = 186 [m.sup.2]) and four closed canopy plots (200 [m.sup.2] each) were surveyed. All trees were identified and located, extension growth of the leader stem of saplings (n = 933) was measured and diameter at breast height (dbh) of trees > 3 m tall (n = 504) was measured. Sapling composition in gaps was dominated by Fagus grandifolia Ehrh., Acer rubrum L. and A. saccharum Marsh., indicating that several species in the current canopy, dominated by Quercus spp, Pinus spp, Liriodendron tulipifera L. and F. grandifolia Ehrh., will eventually be replaced. There was little evidence of within gap partitioning either between the north and south portions of gaps or between their centers and edges, perhaps due to a history of instability in disturbance regimes. All three dominant sapling species showed significantly greater extension growth in gaps than in closed forest. Acer rubrum grew significantly less in gaps than A. saccharum. Under closed canopy this result was reversed, suggesting that while A. saccharum may be better adapted to using gaps, A. rubrum may grow better beneath the canopy.
INTRODUCTION Ecological studies of tree by tree replacement in light gaps within primary old growth forests of Eastern North America are now fairly common (Barden, 1981; Romme and Martin, 1982; [...]