Although longleaf pine (Pinus palustris) forests have been primarily managed with even-aged methods, interest is increasing in uneven-aged systems, as a means of achieving a wider range of stewardship goals. Selection silviculture has been practiced on a limited scale in longleaf pine, but difficulty with using traditional approaches and absence of an evaluation across a range of site types has left managers in doubt concerning its suitability. This study was conducted to quantify the overstory and understory effects of applying single-tree selection, group selection, irregular shelterwood and uniform shelterwood in longleaf pine forests on flatwoods and uplands. Selection treatments (using the Pro-B method) reduced stand basal area to 11.5 m2 ha-1 and shelterwood treatments left a basal area of 5.8 m2 ha-1.
Results/Conclusions
While logging intensity during shelterwood treatment decreased saw-palmetto (Serenoa repens) and increased wiregrass (Aristida beyrichiana) on flatwoods, it resulted in a sharp decline in wiregrass and silverthread goldaster (Pityopsis graminifolia) on uplands. Group selection brought modest understory change on flatwoods (decline in shrubs, increase in grasses), but doubled plant cover on uplands (increased hardwood tree seedlings, shrubs, vines, grasses, forbs, ferns). Single-tree selection caused no lasting impact on saw-palmetto, a decline in other shrubs and grasses and increase in wiregrass on flatwoods and increase in hardwood tree seedlings, shrubs, grasses and forbs on uplands. Although stand density and volume decreased, growth rates were normal in all stands, as were subsequent increases in basal area and tree density. Despite a continuing abundance of saw-palmetto and absence of prescribed fire during post-treatment years, pine regeneration increased in all treated stands on flatwoods. Multi-year drought on uplands decreased pine seedlings, no matter which reproduction approach was used. Although seedling numbers eventually began to recover, they were again depressed by a wildfire in 2013. Even with such losses, sufficient pine seedlings remained in each treatment to foster successful stand regeneration. Single-tree selection produced less overall change in forest ecosystems than group selection, which caused less alteration than shelterwood treatment. Single-tree selection appears to be an effective means of conserving understory plant diversity and achieving stand regeneration, while maintaining a continuous canopy cover that aids in the control of woody competitors and supports an array of resource values. Selection silviculture seems to be a lower risk approach for guiding forests along a trajectory of gradual improvement, with adjustments provided by frequent surface fires and periodic tree harvest.