Field and greenhouse studies were conducted to investigate the role of water stress and time of glyphosate spraying in the variation in glyphosate efficacy. Data on water potential, foliar sugar and starch content, weather, and growth response were gathered for loblolly pine and four of its major competitors on 16 operationally sprayed tracts in Virginia. Glyphosate successfully released loblolly pine on all tracts. Control of white oaks was significantly related to foliar sugar concentration. Water potential and weather variables were not related to glyphosate efficacy for any species. Seedlings of loblolly pine, red maple, and sweetgum were raised in a greenhouse and nursery environment. At the end of the second growing season, three water stress treatments were imposed on each species at each of four glyphosate application dates. ¹⁴C-glyphosate was applied to a subsample of seedlings. Timing of application. water stress, or both significantly affected susceptibility of all three species to glyphosate. Efficacy for all three species corresponded to that expected from field data. Differences in species susceptibility to glyphosate were explained by differences in ¹⁴C-glyphosate translocation, but there was no difference among species in absorption of glyphosate. Efficacy changes across application dates followed seasonal changes in foliar sugar concentration. / Master of Science

During the last three years, 80% of mining permits in Virginia listed forestland as the post-mining land use. Adequate stocking and growth of tree stands at time of bond-release eligibility and beyond is an important beginning for returning mined lands to a productive state. In order to ensure reforestation success, biological constraints, including low mine soil fertility and competition from herbaceous ground cover, must be overcome. The effect of cultural treatments on the growth of three commercial pine species on reclaimed surface-mined land in southwestern Virginia was studied. In June, 1981, containerized seedlings of loblolly (Pinus taeda L.), Virginina (P. virginiana Mill.), and eastern white (P. strobus L.) pines were planted on a flat bench site (Site I) and a site returned to approximate original contour (Site I1). Seedlings were artificially inoculated with Pisolithus tinctorius ((Pers.) Coker and Couch), fertilized with slow-release fertilizer pellets at time of planting and broadcast with N fertilizer prior to the fourth growing season, and the ground cover around them was controlled with herbicides through the third growing season. Survival and growth of these seedlings after the first and second growing seasons were reported by Schoenholtz and Burger (1984). The response of these pines to treatments at the end of the third and fifth growing seasons were evaluated in this study. Treatment effects on foliar nutrient levels and soil properties were also examined. At the end of five years, loblolly and Virginia pines have been successfully established and are performing as well as trees in stands growing don natural soils in the southeastern U.S. Eastern white pine grows slowly the first three years and was just beginning to exhibit a response to treatment. Ground-cover control had the greatest effect on loblolly pine volume-index and elicited as much as an 86% increase in volume-index at the end of five growing seasons. Volume-index of Virginia pine was improved with ground-cover control on Site I and with fertilization on Site II. All species show an additive growth response to the combined treatments. At age five, white pine responded synergistically to combined fertilizer and ground-cover control treatments. The peak response to treatments occurred generally at age two for both loblolly and Virginia pines, while white pine response never peaked. The status of foliar and soil nutrients corroborated the importance of these cultural treatments in improving growth. Negative relationships between volume-index and foliar N and mineralizable N showed that N was not limiting pine growth at this time. Mature stands of serecia lespedeza may have supplied adequate N. A positive relationship between white pine volume-index and foliar P levels suggested that insufficient P may have limited growth of this species. As mine soils in this region age, soil P tends to be fixed by Fe-oxides present in the spoil, making competition for low levels of available-P even greater. Fertilization and ground-cover control will improve tree growth on reforested surface mines by alleviating complex interacting water and nutrient deficiencies. These treatments, implemented during establishment, were still evident at age five, a time that coincides with bond-release eligibility, and response curves suggested that response to treatments will continue as the stands develop. / Master of Science

Biological diversity, or biodiversity, is declining on a global scale at unprecedented rates. These declines are largely the result of human activities and resource use. Intensive forestry is often cited as a contributing factor in biodiversity declines. Because forestry practices are being placed under increased scrutiny with respect to biodiversity impacts, the objective of this project was to determine the effects of specific silvicultural practices on plant diversity in pine plantations on wet flats in Virginia. The study area consisted of three sites in the Coastal Plain. The sites were originally established in 1969 to study the effects of various treatments on loblolly pine growth. The three treatments applied were chop and burn, bedding, and ditching. Fertilization subplots of P, N and P, N, P, and lime, and a control were added to the treatment areas in 1978. This study was conducted in 1991 when stands were 23 years old, nearing rotation age. Bedding exerted the greatest effect on plant diversity. Diversity was lower on the bedded treatment, although total biomass was higher. Bedding appears to increase pine growth by providing seedlings with more available soil volume and by reducing the vegetative regeneration of hardwoods and shrubs, thereby decreasing site diversity. Ditching likewise increased pine growth by lowering water table levels, but ditching had little effect on plant diversity. Fertilization exhibited only minor effects on diversity, and those effects that were observed did not reveal any definitive trends. Of the treatments applied, liming appeared to increase pine growth most, possibly due to increased calcium availability. Water table level was highly correlated to mid story diversity, though it was less correlated to other canopy layers. In addition, correlation analyses indicated a significant degree of interaction between canopy layers. It appears that diversity, particularly in the lower canopy layers, is affected directly by treatments and indirectly by shifts in overstory characteristics. Intensive forest management involving hydrology-altering site preparation and fertilization impacted plant diversity within these wet flat plantations. Whether such changes affect wildlife habitat or ecosystem functioning requires further study. / Master of Science