Gaps in a gappy forest: plant resources, longleaf pine regeneration, and understory response to tree removal in longleaf pine savannas

Resource availability and planted longleaf pine (Pinus palustris Mill.) see dling and understory vegetation response within and among three sizes of ex perimentally created canopy gaps (0.11, 0.41, 1.63 ha) in a mature longleaf pine savanna were investigated for 2 years. Longleaf pine seedlings and un derstory vegetation showed increased growth in gaps created by tree removal . Longleaf pine seedling growth within gaps was maximized approximately 18 m from the uncut savanna. Increased longleaf pine seedling survival under t he uncut savanna canopy observed after the first year suggests that the ove rstory may facilitate establishment of longleaf pine seedlings rather than reduce survival through competition. Despite the relative openness of the u ncut longleaf pine forest, light quantity was increased by tree removal. Li ght was also the resource most strongly correlated with seedling and unders tory vegetation growth. Although net N mineralization was correlated to see dling response, the amount of variation explained was low relative to light . Belowground (root) gaps were not strong, in part because of non-pine unde rstory roots increasing in biomass following tree removal. These results su ggest that regeneration of longleaf pine may be maximized within gap sizes as small as approximately 0.10 ha, due largely to increases in light availa bility.