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" Predictors of Upland Hardwood Distribution and the Relationship Between Hardwood Distribution and Avian Occupancy in Fire Maintained Longleaf Pine Forests "
Hannon, Daniel Richard
DePerno, Christopher
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Latin Dissertation
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English
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| Record Number
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1105904
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| Doc. No
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TLpq2344363054
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| Main Entry
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DePerno, Christopher
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Hannon, Daniel Richard
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| Title & Author
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Predictors of Upland Hardwood Distribution and the Relationship Between Hardwood Distribution and Avian Occupancy in Fire Maintained Longleaf Pine Forests\ Hannon, Daniel RichardDePerno, Christopher
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| College
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North Carolina State University
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| Date
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2019
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| student score
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2019
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| Degree
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M.Sc.
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| Page No
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94
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| Abstract
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The longleaf pine (Pinus palustris) ecosystem has been reduced to a fraction of its original extent, and restoration of longleaf pine communities is a focus of managers 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 and management factors that influenced abundance of mature upland hardwood trees in xeric longleaf pine communities and how hardwood distribution influenced the occupancy probability of 15 avian species 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 hardwood 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 growing-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. Hardwood abundance could be increased by reducing pine basal area, though extensive hardwood encroachment could occur without frequent prescribed fire. We used fixed-radius point counts to sample the presence-absence of 15 avian species at 305 points and assessed forest composition and structure around each point using field-based and remote sensing techniques. We developed single-season single-species occupancy models with an emphasis on the influence of hardwood overstory cover on occupancy. Due to issues with model fit, we were unable to model occupancy for 3 of the 15 focal species. Occupancy probability for 3 of the 12 species was positively influenced by pine overstory cover and occupancy probability for 2 of the 12 species was negatively influenced by pine overstory cover, including 1 species for which pine overstory cover was the sole variable in the top model. Occupancy probabilities for 7 out of the 12 focal species were positively influenced by hardwood overstory cover or stem density, whereas occupancy probabilities of 4 out of 12 of the focal species was negatively influenced by hardwood cover or stem density. Hardwood overstory cover levels of 5-15% resulted in high occupancy probabilities for the species that were positively influenced but did not result in substantially low occupancy probabilities for the species that were negatively influenced. We suggest that managing longleaf pine uplands with lower and upper bounds of 5% to 15% hardwood overstory cover with stem densities of ≤ 250 stems/ha will provide habitat for the greatest diversity of birds while avoiding negative effects to species associated with upland longleaf pine communities.
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Environmental management
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Forestry
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Macroecology
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