Dan HannonNorth Carolina Division of Land and Water Stewardship · Natural Heritage Program
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Prescribed fire and other forest management practices aimed at restoring longleaf pine (Pinus palustris) communities often focus on the reduction, or removal, of upland hardwoods with the goal of providing habitat for threatened and endangered plant and animal species, including the federally endangered red-cockaded woodpecker (Leuconotopicus borea...
The longleaf pine (Pinus palustris) ecosystem has been reduced to a fraction of its original extent, and where this ecosystem does occur, it is often degraded by hardwood encroachment. The reduction of hardwood tree cover is often a desirable longleaf pine community restoration outcome, though hardwood midstory and overstory trees have been recogni...
We investigated the role of mature hardwood cover in driving avian occupancy in a landscape managed with long-term frequent fire. We used fixed-radius point count surveys with repeat visits to sample the presence-absence of 15 focal species (Bachman’s sparrow, blue-gray gnatcatcher, brown-headed nuthatch, blue-headed vireo, Carolina chickadee [Poecile carolinensis], eastern wood-pewee [Contopus virens], great crested flycatcher [Myiarchus crinitus], northern bobwhite, pine warbler [Setophaga pinus], prairie warbler [Setophaga discolor], summer tanager, tufted titmouse [Baeolophus bicolor], red-eyed vireo, red-headed woodpecker [Melanerpes erythrocephalus], yellow-throated vireo) that we expected to display a range of responses to hardwood midstory and canopy cover. We assessed forest composition around each point count location using field-based and remote sensing methods to capture information about hardwood cover, which typically is sparse and patchily distributed in longleaf pine uplands on the study area. We developed models of occupancy with the goal of identifying avian species for which hardwood cover is an important predictor of occupancy, negative or positive, in longleaf pine uplands. We sought to identify specific thresholds of hardwood cover for individual bird species, in turn informing efforts aimed at balancing the goals of endangered species management and biodiversity conservation.
The longleaf pine (Pinus palustris) ecosystem has been reduced to only a fraction of its original extent, and restoration of longleaf pine plant communities is a focus across the southeastern United States. The reduction of hardwood tree cover is often a desirable longleaf pine community restoration outcome, although hardwood midstory and overstory trees have been recognized as a natural component of the communities. Moreover, the appropriate amount of hardwood tree cover in a restored longleaf pine community is debated, as more hardwood tree cover can benefit mast-dependent wildlife (e.g., fox squirrels [Sciurus niger], white-tailed deer [Odocoileus virginianus]) and less hardwood tree cover is critical to the federally endangered red-cockaded woodpecker [Leuconotopicus borealis]. To inform the debate, we assessed the environmental (e.g., topography, edaphic conditions, and pine basal area) and management (e.g., distance to firebreaks, prescribed fire history) factors that influenced abundance of mature upland hardwood trees in xeric longleaf pine communities on a site where frequent growing-season fire has been ongoing since 1991. We counted upland hardwoods ≥5 cm diameter at breast height (DBH) at 307 random field plots (0.04 ha) and categorized all hardwood trees as belonging to either a guild of fire-tolerant oaks or a guild of fire-sensitive hardwood species. We used generalized linear models (GLM) to determine the most important predictors of abundance for both guilds. The predictors of abundance differed between the two guilds, with fire-tolerant oak abundance increasing with greater slope and proximity to ignition sources and decreasing with greater pine basal area. Fire-sensitive hardwood abundance increased with mesic site conditions and decreased with the number of dormant season fires and greater pine basal area. Although seasonality in fire history was an important predictor of fire-sensitive hardwood abundance, variables related to long-term fire-history were not important predictors of fire-tolerant oak abundance in longleaf pine communities. Management for reduced pine basal area can lead to greater hardwood abundance, though extensive hardwood encroachment could occur without frequent prescribed fire.