Browsing by Author "Jackson, Barry Clayton"

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    Assessing Species Composition in Second Growth and Old Growth Rich Coves of the Southern Appalachians
    (2008-04-28) Jackson, Barry Clayton; DR. H. LEE ALLEN, Committee Co-Chair; DR. THOMAS R. WENTWORTH, Committee Co-Chair; DR. DAVID L. LOFTIS, Committee Member; DR. BRONSON P. BULLOCK, Committee Member
    I compared composition of plant communities in second growth (60 - 80 years old) and old growth rich coves for evidence of reduced abundance or presence of plant species in the second growth communities. I evaluated the utility of both univariate and multivariate analytical methods. Data were collected from twenty-six 1000 m2 plots located across three distinct mountain ranges and geologies in the southern Appalachians of North Carolina. Comparison of nested and non-nested sampling protocols found no statistical differences in the parameters of species-area curves. Furthermore, I found no difference between the species-area curves of old growth and second growth; but, multiple comparison procedures identified 13 of 79 species with either lower abundance or incidence of occurrence in second growth rich coves. Nonmetric Multidimensional Scaling (NMS) revealed no age class differences, but detected significant block differences associated with the three mountain ranges. Elevation and base cation concentrations were strongly correlated with the first and third NMS axes, respectively, but there was no strong correlate with the second NMS axis. In comparing univariate and multivariate analysis methods, I found that (1) aggregate univariate methods (like species diversity and species-area relationships) facilitate comparison of unrelated communities (2) multivariate methods support comparison of related communities and (3) univariate, multiple comparison procedures readily detect specific species changes within a community .
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    Vegetation Differences in Neighboring Old Growth and Second Growth Rich Coves in Joyce Kilmer Wilderness Area: A Thirty-two-year Perspective
    (2007-06-22) Jackson, Barry Clayton; Thomas R. Wentworth, Committee Member; J. Dan Pittillo, Committee Member; David L. Loftis, Committee Member; H. Lee Allen, Committee Chair
    I surveyed vegetation in neighboring old growth and second growth rich coves in the Joyce Kilmer Wilderness Area, North Carolina. This data, combined with data from three previous studies, provide a 32 year perspective of stand structure, species frequencies of occurrence at the 1 m2 scale, and species richness at the 1 m2 scale. I sampled one 0.1 ha plot in each cove. I subdivided each plot into ten 10 m by 10 m modules and sampled percentage cover of all species present in each module, plus stem diameter for woody stems. Additionally, I sampled presence absence in a variety of subplots at scales of 0.01 m2, 0.1 m2, 1 m2, 10 m2, and 100 m2. A cohort of 30-40 cm diameter at breast height Liriodendron tulipifera trees dominated the second growth cove, while the old growth site had a broader mix of species with an inverse J-shape diameter distribution. In both rich coves, the frequencies of occurrence at 1 m2 appeared highly variable for individual species between sample years and distances of 200 m or less. The four studies provided species richness comparisons at the 1 m2 scale between the old growth and second growth (at ages 16, 35, 39, and 47 years). I concluded that the differences in second growth species richness between studies demonstrated rich cove forest succession. High species richness following disturbance reflected a surge of opportunistic species (age 16). The opportunistic species declined following canopy closure, resulting in significantly lower species richness (age 35). After further stand development, a resurgence of late-succession species increased species richness to equal levels with old growth (age 39 and 47). Finally, I examined species-area relationships between the two coves, and between these rich coves and the regional average. Arrehnius model (log10 species: log10 area between the scales of 0.1 m2 to 1000 m2) species-area curves indicated no difference in species-area relationships between the two coves. Collectively, these two rich coves had a significantly higher intercept but no difference in regression slope from the regional average. These findings reflect an average rate of species accumulation in the Joyce Kilmer coves, but with higher-than-average species density at all measured scales.