Early impacts of midstory hardwoods and overstory density on longleaf pine seedling establishment on xeric sitesThis article is part of a larger document. View the larger document here.
Competition has long been considered a constraint on longleaf pine (Pinus palustris Mill.) regeneration. However, observational evidence suggests that neighboring vegetation may facilitate longleaf pine seedlings on xeric sites. To explore this notion, we established a manipulative experiment across a gradient of overstory basal area (9 to 25 m2/ha) with or without a hardwood midstory in the North Carolina Sandhills. After 2 years, seedling survival averaged 80 percent, differed significantly among overstory density groupings (p = 0.0006), and was lowest (73 percent) under high overstory density (greater than 18 m2/ha). Seedling survival also varied significantly among midstory treatments (p = 0.0261), with the highest survival occurring beneath an intact midstory (84 percent). Seedling biomass averaged 10.5 g, varied significantly among overstory groupings (p = 0.0007), and was greatest (10.9 g) under low overstory density (less than 12 m2/ha). The presence of a hardwood midstory did not significantly impact seedling growth.