Vegetative response to 37 years of seasonal burning on a Louisiana longleaf pine site

Abstract

From 1962 through 1998, 20 prescribed burns were applied in a natural stand of longleaf pine (Pinus palustris Mill.) to determine the effects of various fire regimes on the forest plant community. The original longleaf seedlings regenerated from the 1955 seed crop and were growing in a grass-dominated cover when the study began. By 1999, prescribed burning in March and May resulted in a significantly greater stocking of longleaf pine (203 trees/ac) than on the unburned and July burned treatments (72 trees/ac) (α = 0.05). Fire arrested the growth of natural loblolly pine (P. taeda L.) and hardwoods, but loblolly pines and hardwoods of at least 4 in. dbh added 70 ft2/ac of basal area on the unburned plots. Thus, total woody basal area was significantly greater on the unburned (117 ft2/ac) and May burned (132 ft2/ac) treatments than on the July burned treatment (66 ft2/ac); basal area was intermediate on the March burned treatment (97 ft2/ac). Pin e volume was 4,315, 2,870, 2,652, and 1,970 ft3 inside-bark/ac on the May burned, March burned, unburned, and July burned treatments, respectively, but these differences were not statistically significant (P = 0.06). There was only 11 lb/ac of herbaceous plants on the unburned plots. Herbaceous plants averaged 993 lb/ac on the three burned treatments, with pinehill bluestem (Schizachyrium scoparium var. divergens [Hack] Gould) being the most common herbaceous plant. We believe the chief influence of burning in this natural lo, alpine forest was not on pine yield but how fires influenced overall stand structure and species composition.