Fate of residual canopy trees following harvesting to underplant longleaf pine seedlings in loblolly pine stands in Georgia
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Over the past few decades, reports of forest health problems have concerned scientists and forest managers in loblolly pine forests of the southeastern United States. Several interacting factors likely contribute to observed reductions in loblolly pine health, including low resource availability on many upland sites that were once dominated by longleaf pine. Currently, land managers are interested in converting such sites back to longleaf pine, while maintaining ecosystems services that are now provided by loblolly pine. Recent research suggests that underplanting longleaf pine in loblolly pine stands may be a viable solution for stand conversion, but it is not clear how such treatments affect the longevity or condition of residual canopy trees. In this study, we compared the effects of three levels of uniformly-distributed stand density (uncut Control, ~16 m2/ha basal area; MedBA, ~9 m2/ha basal area; LowBA, ~6 m2/ha basal area) and three gap sizes (LG, radius of 40 m; MG, radius of 30 m; and SG, radius of 20 m) on the survival, growth, and canopy condition of residual trees through five years after harvest. Survival was not significantly affected by treatment (p = 0.5899), with an average of 96.8 percent survival. Tree growth during the study period was significantly greater on the LowBA plots than on the Control plots. By the end of the study period, LowBA plots had greater live crown ratios and less crown dieback than Control plots. Our results suggest that harvesting loblolly pine trees for underplanting longleaf pine does not accelerate pine decline in the short-term but does have the potential for growth release of residual trees.