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Research in optimizing forest management has focused on single-stand problems to derive optimal harvest sequences in terms of residual basal area or residual stand structure for uneven-aged stands, and timing of pre-defined thinning treatments and clearcut harvests for even-aged stands. Recent research results provide various means of numerically deriving optimal management prescriptions for single-stand problems, thus considering all feasible solutions as opposed to considering only pre-defined harvest alternatives. However, forest-level problems involving aggregates of stands with similar management constraints are usually solved by evaluating pre-defined harvest sequences. Forest-level management optimization problems in which individual stands may be assigned to either even-aged or uneven-aged silvicultural systems have not been modelled. A dynamic forest management model is describer: that prescribes silvicultural treatments for stands within a multi-stand management unit. Results of an application of this approach to an Appalachian hardwood forest, comparisons of individual stand and whole forest optimal solutions, and efficiency of the solution algorithm are discussed. / Ph. D.

Competition for resources and other interference from non-crop vegetation often limits the productivity of pine and pine-hardwood forest stands in the southern United States. However, forest researchers have yet to fully quantify the effect of this interference on forest tree yield and there is an incomplete understanding of the biological mechanisms of interference. To better quantify the effects of interference interactions and elucidate their mechanisms, a field replacement series experiment and two supporting greenhouse experiments were carried out using loblolly pine (Pinus taeda L.), red maple (Acer rubrum L.), black locust (Robinia pseudoacacia L.), and herbaceous vegetation. Interference between pine. hardwood species, and herbaceous vegetation significantly impacted the growth and yield of young experimental pine-hardwood stands. While herbaceous vegetation significantly affected all stands. it reduced the yield of hardwood species more than loblolly pine. Loblolly pine appeared to ameliorate the effect of herbaceous vegetation on hardwoods in some stands. Interference outcomes were site- and scale-dependent. In field stands, synergistic adjustment in total yield due to pine-hardwood interference was not observed, except for loblolly pine-black locust mixtures on lower site quality replicates. Hardwood species suppressed the growth of pine in seedling stands planted at very close spacing in greenhouse boxes, while the yield at age three of less densely-planted field stands was positively related to the proportion of pine in the stand. Close spacing increased the ability of wide-spreading hardwood crowns to overtop and restrict light availability to conically-shaped pine crowns. Interference outcomes were related to the interactive effect of light, soil moisture, and soil nitrogen resources on tree growth and competitive ability. If not overtopped by hardwoods, loblolly pine had high yields in mixtures with hardwoods and competed effectively for soil moisture and nitrogen through efficient use of these resources. Changes in allometric relationships were observed for tree species in response to interference including root-shoot ratios, crown dimensions, and specific leaf areas. Tall fescue (Festuca arundinacea Schreb.), the principal herbaceous species in the field study, appeared to affect the physiology and yield of all species through allelopathy in a greenhouse experiment. suggesting that reduced yield in herbaceous plots may be due to direct chemical effects in addition to resource competition. / Ph. D.

The FVS-Sn model was developed by the USDA Forest Service to project and report forest growth and yield predictions for the Southern United States. It is able to project forest growth and yield for different forest types and management prescriptions, but it is a relatively new, complex, and untested model. These limitations notwithstanding, FVS-Sn once tested and validated could meet the critical need of a comprehensive growth and yield model for the mixed hardwood forests of the southern Appalachian region. In this study, sensitivity analyses were performed on the FVS-Sn model using Latin hypercube sampling. Response surfaces were fitted to determine the magnitudes and directions of relationships between FVS-Sn model parameters and predicted 10-year basal area increment. Model sensitivities were calculated for five different test scenarios for both uncorrelated and correlated FVS-Sn input parameters and sub-models. Predicted 10-year basal area increment was most sensitive to parameters and sub-models related to the stand density index and, to a lesser degree, the large tree diameter growth sub-model. The testing procedures and framework developed in this study will serve as a template for further evaluation of FVS-Sn, including a comprehensive assessment of model uncertainties, followed by a recalibration for southern Appalachian mixed hardwood forests. / Master of Science

Old-growth forests provide important habitat for wildlife, support the maintenance of biodiversity and serve as control areas for scientific research. Expanding current old-growth stand area by utilizing neighboring younger, managed stands allows private landowners to meet management needs and enables government agencies and private conservation organizations to meet old-growth forest objectives. Seven old-growth upland oak stands and seven adjacent younger, managed stands of the same site and stand type were measured in the Ridge and Valley, Blue Ridge, and Piedmont provinces of Virginia and Pennsylvania in an effort to characterize species composition, diameter distribution and canopy structure. A computer-based ecosystem/gap model (JABOWA-3) was modified and used to simulate silvicultural manipulations in the younger stands that would reproduce older forest characteristics. Various silvicultural techniques were used to convert the primarily even-aged younger stands into uneven-aged stands and then into old-growth. These manipulations included single-tree selection, herbicide application, culling larger diameter stems and planting seedlings where required. Individual trees within each of the younger, managed stands were removed at various time intervals and these simulated stands were then projected to a point in time in which the stand approximated the diameter distribution and composition of its paired old-growth stand. Several projections were made in each of the younger stands to meet this objective. Once a satisfactory projection was made for conversion of a younger stand to old-growth, a success rate was determined to gauge how close the simulated stand approximated the diameter distribution and composition of its old-growth counterpart. From this information, biologically feasible and environmentally sound management plans were created to carry out the silvicultural manipulations required by the model for each of the sites. / Master of Science

Data for this study were collected by the US Forest Service and the Pennsylvania Bureau of Forestry on nearly 600 plots in central Pennsylvania. Tree and stand characteristics recorded between 1978 and 1985 include estimates of percent defoliation on individual trees. Logistic regression using maximum likelihood estimation was employed to model individual-tree mortality of 15 species in central Pennsylvania that had been defoliated by the gypsy moth. Defoliation was estimated to the nearest ten percent for individual trees. Other variables used for prediction included stand basal area and an individual-tree relative basal area index. Success ranged from no fit for three of the species to an R value (a derivation of Akaike's information criterion) of .613 for white oak. The inclusion of defoliation in the models had a varied effect. For four of the species percent defoliation was not significant. For hickory and white oak respectively, percent defoliation raised the R value by .305 and .290 percentage points. As many as five models for each species were developed: one or two models with no defoliation measure in the model and one each for one, two or three consecutive years of defoliation measures. A beta and gamma function were used to model individual· tree basal area growth for the same 15 species. The models were fit using nonlinear least squares. Variables used include the relative basal area index, stand basal area, site index and a defoliation index that incorporated three years of individual-tree, percent defoliation. The beta and gamma functions fit equally well with values of (1 - relative mean square error) ranging from .1967 to .6290. Results for both models are presented for each species. The defoliation index was a significant variable for five of the fifteen species: white, chestnut, red, and black oak and sassafras. / Master of Science

A method is described for implementing group selection regeneration in Appalachian hardwoods. The diverse set of definitions of the method, and the current forest demands are combined to form a flexible system of implementation that can accommodate public as well as private forests. Group selection is used where an uneven-aged silvicultural system is required and multiple objectives demanded. Several types of information are collected in a sample of the forest and then used to make the selection decision of which groups of trees to remove, and which groups to leave. / Master of Science

The effects of site quality, dormant and growing season harvests, and four even-aged regeneration treatments on natural hardwood and planted loblolly pine (Pinus taeda L.) are examined three years after clear felling and whole-tree harvesting upland hardwood stands in the Virginia Piedmont. Natural hardwood regeneration was dominated by stump sprouts, with seedlings and advanced regeneration playing a secondary role. Stump sprouts and seedlings plus advanced regeneration were significantly taller with a dormant season harvest. A growing season harvest resulted in significantly better survival and growth of loblolly pine after 2 growing seasons. A trend for more loblolly pine volume index growth on the poor site class was noted. Regneration alternatives included an herbicide stump treatment at time of harvest that significantly reduced stump sprout growth, 70%, and resulted in significantly better loblolly pine survival. This stump sprout control also favored hardwood seedling and advanced regeneration. One regeneration alternative included either a triclopyr basal bark spray or hexazinone soil applied spot treatment for releasing loblolly pine at age one. Both release treatments significantly reduced natural regeneration basal area and density when used two years after the herbicide stump treatment. Loblolly pine growth was significantly increased by both pine release treatments. Herbicide treatments were most effective, in terms of lower hardwood basal area and greater loblolly pine volume index, in growing season harvest treatment plots. / Master of Science

Harvesting practices in the southern Appalachians have moved away from clearcutting in favor of variable retention harvesting systems. A study was initiated in 1995-8 to investigate the effects of retaining varying numbers of residual trees on regeneration in seven silvicultural treatments. A second study specifically focused on stump sprouting in only three of those treatments. The treatments for first study included: a clearcut, commercial harvest, leave-tree, shelterwood, group selection, midstory treatment, and an uncut control. The second only focused on the clearcut, leave-tree, and shelterwood. These treatments were implemented in seven stands in Virginia and West Virginia over two physiographic provinces, the Appalachian plateau and Ridge and Valley. The stands were even-aged oak dominated Appalachian hardwood stands on fair quality sites with average ages ranging from 63 to 100 yrs. Permanent plots were randomly located in each stand and all overstory trees (>5m tall) were inventoried and tagged prior to harvest. Regeneration was also quantified. Harvest occurred between 1995-8. For the current studies the plots were re-inventoried 9-11 years post-harvest and all regeneration in all treatments as well as stump sprouts in the selected treatments were quantified. The first study utilized a mixed model ANOVA to analyze five species groups: oak, maple, black cherry-yellow-poplar, miscellaneous, and midstory. Response variables included importance value, average height, and density compared within species group and among treatments. Differences between sprout and seedling origin regeneration were also investigated within species group among treatment. Results indicated that oak densities were similar in all of the treatments, and stump sprouts were larger and more frequent than seedlings. Maple exhibited an increase from pre-harvest overstory importance and exhibited competitive sprouting. The black cherry-yellow-poplar group had few but highly competitive sprouts and a considerable increase in seedling origin regeneration in all treatments. The miscellaneous species densities increased as well with more competitive sprouting in some treatments. The midstory species were excluded from the analysis as it was assumed these species would not occupy canopy positions in a mature stand. The second study investigated differences in the percent of stumps that sprouted and the number of sprouts per stump. The percent data were analyzed using a non-parametric one-way ANOVA and regression analysis, while the sprouts per stump data were compared in a mixed model ANOVA and regression. Species were combined into six groups: the red oak group, chestnut oak, red maple, white oak/hickory group, mixed mesic group, and midstory group. The plateau tended to have reduced sprouting compared to the Ridge and Valley for most species groups and treatments. The red oak group, chestnut oak, and red maple exhibited reduced sprouting with increased residual basal area. The mixed mesic group did not show any effect in sprouting related to residual basal area. Only chestnut oak showed fewer sprouts per stump as residual basal area increased. / Master of Science

The effects of seven silvicultural prescriptions were examined one full growing season post-treatment on five sites in the Ridge and Valley, Cumberland Plateau, and Allegheny Plateau of Virginia and West Virginia. Prescriptions were (1) control, (2) understory control with herbicide, (3) group selection, (4) high-leave shelterwood, (5) low-leave shelterwood, (6) leave tree, and (7) clearcut. The effects of each treatment on the vascular plant community were characterized by changes in species diversity, species composition, exotic species richness, Raunkiaer's life-forms, and growth-forms. Pre-treatment, baseline data, and a randomized block design ensured the precision of post-treatment comparisons. High-disturbance treatments (i.e., low-leave shelterwood, leave tree, clearcut) exhibited lower tree-stratum species richness than unharvested treatments. Prescriptions had no effect on shrub-stratum richness. Compared to the control, woody, herb-stratum richness was higher in harvested treatments. Non-woody herb-stratum richness was unaffected. No differences in herb-stratum species diversity were detected using Shannon's (exp H') or Simpson's (1/D) indices. Non-woody species richness per 2-ha treatment plot was significantly higher than the control for high-disturbance treatments. Pre- vs. post-treatment species composition was least similar for high-disturbance treatments, as measured by qualitative and quantitative community similarity indices. Exotic woody species richness was unaffected by treatment; however, non-woody exotic species were more prevalent in high-disturbance treatments. Hemicrytophytes replaced phanerophytes as the most important life-form for harvested treatments. Therophytes were more important in harvested treatments, while the proportion of cryptophtes and chamaephytes did not change in response to treatments. Tree and shrub growth-forms were less dominant in harvested treatments, while graminoids and annual/biennial forbs were more important for high-disturbance treatments. These data represent only the initial results of a long-term study designed to examine plant-community response to silviculture for one harvest rotation length. Long-term results will aid in devising management strategies that address concerns for biodiversity without devaluing traditional resource demands. / Master of Science