Dynamics of artificial regeneration in gaps within a longleaf pine flatwoods ecosystem

The selection silvicultural system has gained popularity as a means for developing and maintaining uneven-aged stand structure in a variety of forest types. Only limited information exists, however, regarding regeneration dynamics and growth of longleaf pine ( Pinus palustris Mill.) managed under the group selection silvicultural system in the southeastern USA. A replicated artificial gap study, established in a 65-year-old, second-growth stand in northwest Florida, was used to examine the interactions between site resource availability (light, nutrition, water) and canopy gap position on survival and growth of containerized longleaf pine seedlings over two growing seasons. A gradient in site resource availability was created using fertilizer and hand weeding treatments. Levels of light transmittance (averaged over the growing season) within the gaps varied by location and ranged from 72% near the uncut edge to 96% in the gap center. Seedlings growing in the gap center had significantly lower survival rates (e.g., 1999, center=23%, edge=51%), but larger diameter increments (e.g., 2000, center=3.6 mm, edge=1.4 mm) than those found in lower light environments along the gap edge. Soil moisture content had little apparent impact on these differences in survival and growth, as surface (0–15 cm) moisture contents did not vary significantly among gap positions in either growing season. Although seedling survival was significantly reduced by the fertilizer and hand weeding (control=41%, treated=31%), diameter increment was 44% greater than the untreated control. Results of this study suggest that a group selection silvicultural system that provides sufficient light and relief from competition (for nutrients) for seedlings may be a suitable silvicultural method for effectively regenerating longleaf pine forests.