Effects of fungi and overstory composition on tree seedling survival and growth were investigated in closed canopy upland forests in the coastal plain of South Carolina. Seedlings of Quercus alba, Cornus florida and Pinus taeda were planted in the understory of two forest types -naturally regenerated hardwood and planted pine. Fungal species composition and biomass were experimentally manipulated with a treatment of the fungicide captan. In contrast with other studies conducted in different systems (sand dune, grassland, and old field), the effects of soil fungi were minor in a closed canopy forest. Only Q. alba showed a significant response to the fungicide (p < 0.05) treatment with increased growth. Overstory composition had no significant effect on growth or survival for any of the species. Both of the commercially desirable species (Q. alba and P. taeda) had reasonable survival ( @ 60%). Both also maintained positive, though modest, growth. This suggests that an advance regeneration pool could be established successfully by artificial regeneration. / Master of Science

This study examines the effects of clearcut regeneration with whole-tree harvesting on plant diversity. Three approaches were used to study changes in species composition and structure: (1) forest level, (2) stand level, and (3) diversity indices. Within each approach the forest was stratified into three horizontal vegetative regions based upon height: herb (< 1 m), shrub (between 1 and 5 m), and tree (> 5 m). Between the pre-harvest and 17-year-old forest, the relative percent cover of 3 out of 45 herbaceous and 2 out of 34 woody species were found to be significantly different (df = 3; a = 0.10) in the herb stratum; the importance value (average of relative basal area and stem density) of 2 out of 25 woody species in the shrub stratum; and 1 out of 21 woody species in the tree stratum. Within stands, the three lower quality, 17-year-old stands (SI50 = 12.2, 15.2, and 18.3 m) most resembled their pre-harvest composition; however, increases in ericaceous species were observed in the herb and shrub strata potentially inhibit the future regeneration of tree species. The SI50 = 21.3 m stand incurred the greatest changes in composition potentially due to the lack of fire as a disturbance mechanism. The major mechanism that has caused the shifts in species composition and structure is the change in the microenvironment due to the removal of the overstory, which has shifted the competitive advantages from one species to another. In all cases, diversity indices were not found to be significantly different between the 17-year-old and pre-harvest forests. Diversity indices were therefore determined to have limited use if a manager wants to know specific compositions and/or abundance of species. / Master of Science

In the upland hardwood forests of the southern Appalachians, management tools are needed based on the characteristics of the site to quantify the site quality where no accurate maps of site quality exist. Three studies were conducted to achieve this objective. The first study tested if independent measures of forest productivity, based on vegetation and environment, in a six-county study area in the Blue Ridge Mountains in North Carolina would correlate with measures of forest productivity obtained from U.S. Forest Service Forest Inventory Analysis (FIA) data. Specific hypotheses included: FIA measures of forest productivity are related to one another; FIA measures of forest productivity are related to FIA-measured landscape parameters; and FIA measures of forest productivity are related to independent measures of forest productivity based on landscape parameters and soil characteristics. Four predictive indices of forest productivity were used; three were generated in a geographic information system (GIS). FIA measures of forest productivity were not significantly correlated to FIA measured landscape parameters. FIA site productivity classes were significantly correlated to FIA measures of site index. Independent measures of forest productivity, particularly the Moisture Regime Index (MRI) and the Forest Site Quality Index (FSQI), were significantly correlated to FIA measures of site index. Topography can be used to delineate site quality, but the addition of soil depth can prove to be useful in the estimation. The second study was designed to develop methods, based on field and digital data, to identify colluvial soils in the central Ridge and Valley of southwestern Virginia. Two hypotheses were tested. First, on the linear side slopes of the study area, where site quality is low in stands with subxeric to xeric moisture regimes, vegetation and topography can indicate colluvial soils. A second hypothesis tested if the topographic signature of colluvial soils could be identified geospatially with a digital elevation model. Results indicated that the MRI and the Terrain Shape Index predicted the presence of colluvial deposits in the study area. The basal area of yellow-poplar was positively associated with colluvial soils. A GIS-based model found the slope difference of colluvial soils to be less steep than residual soils as the size of the neighborhood increased. The final study determined if measures of site quality in the Blue Ridge Mountains of North Carolina were related to the water budget. Specifically,the hypothesis that site index could be predicted by variables that represented the inputs, usage, and supply of water was tested. A second hypothesis questioned if site quality classes could be predicted by a combination of topography and the annual water budget. Regression models predicted site index to be a function of topography, available water supply, and the annual water budget, but the accuracy was low (R2=0.11 and 0.13). A classification approach yielded better results. Incorporating the annual water budget into the FSQI increased classification accuracy of predicted site index by 50%, and decreased the number of sites misclassified by one class by 8%. Where accurate maps of site quality do not exist, the MRI, the abundance of yellow-poplar, and the modified FSQI may be used to delineate site quality for site-specific management and, ultimately, greater return on investment for the landowner. / Ph. D.