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Intensively managed forests of the Southern United States are among the most important sources of wood fiber and timber in this country. There is a great deal of concern that disturbances associated with trafficking by heavy machinery might diminish long-term soil-site productivity. However, determining the effect of harvesting disturbance and silvicultural treatments on the long-term productivity of pine plantations is difficult because, in addition to harvesting effects, growth distributions are affected by changes in climate, silviculture, and genetics. The primary objectives of this study were to determine (1) whether logging disturbances under operationally realistic circumstances affect soil quality, hydrologic function, and loblolly pine (Pinus taeda L.) productivity on wet pine flats, and (2) whether intensive forest management practices mitigate disturbance effects if they exist. Three 20-ha loblolly pine plantations located on wet pine flats in South Carolina were subjected to combinations of wet- and dry-weather harvesting and mechanical site preparations. Changes in soil-site productivity after five years were evaluated using a new rank method. The key advantage of the rank change method is that it is largely independent of the confounding factors (e.g. genetics, silvicultural practices, and climate) that affect comparisons of tree growth and soil quality between growth cycles. After five years, loblolly pine site indexes (base age 25) ranged between 13 and 33 m, and production ranged between 0.5 and 95 Mg ha-1. Soil bulk densities increased from 1.15 to as high as 1.44 g cm-3 after harvesting; by age 7 years it had decreased to approximately 1.25 g cm-3. At the sub-stand scale (0.008 ha), visually assessed soil physical and harvesting residue disturbances had little influence on relative changes in soil-site productivity after five years. Factors that specifically reflect site drainage were the most influential on changes in productivity. At the operational scale (3.3 ha), there were no differences between wet- and dry- harvested sites as long as bedding was applied as a site treatment. These results indicate that when standard site preparation is employed, fertile, wet pine flats such as these are resilient in that they recover from severe, but operationally realistic, harvesting disturbances. / Ph. D.

Antibiotics and antibiotic resistance genes from animal manure applied to soil as fertilizer are now among the most concerned contaminants in soil. The widespread use of antibiotics in livestock might amplify the risk of developing antibiotic resistance, causing once treatable diseases to turn deadly. The World Health Organization declared antibiotic resistance as "one of the biggest threats to global health, food security, and development". The goal of this dissertation was to develop best manure management practices by understanding the behavior of manure-associated antibiotics in manure, water, and soil. In particular, my research focused on the effects of manure application methods, on-site manure treatment methods, manure application seasons, and manure-rainfall time gaps on antibiotic surface runoff losses, antibiotic distribution and movement in soil, antibiotic dissipation in soil, and development of antibiotic resistance. Rainfall simulation field-scale and soil incubation lab studies were combined to find the best manure management practices. My research has shown for the first time that using the manure soil subsurface injection method, especially during spring application season due to moist soil, applying manure at least 3 days before a subsequent rainfall, and using composted manure, can significantly reduce the quantity of antibiotic loss with runoff from manure-applied fields to the surrounding environment. The majority of applied antibiotics remained in soil. All antibiotics showed a similar dissipation pattern with fastest kinetics during the first 14 d before slowing down. The effect of two manure application methods on antibiotic dissipation kinetics varied with different antibiotics. Although the half-life of tested antibiotics in soil was short (<21 days), some remained detectable even at 6 months after a single manure application. Results also showed that compared to the surface application, the subsurface injection slits acted as a "hot zone" with a higher amount of antibiotics, manure microbes, and antibiotic resistance. The results provide information for policy makers, manure managers, and farmers to develop better manure management practices that can use manure as fertilizer while minimizing the spread of antibiotics to surrounding water, soil, and plants. / Doctor of Philosophy / There is growing concern about antibiotic resistance as a serious human health threat because a resistant infection may kill, can spread, and increases health costs. Every year in the United States, there are 2 million people infected with antibiotic resistant bacteria, 23,000 people die as a direct result of these infections, and $55 billion is lost due to increased hospital stay and lost work days. Although bacteria naturally develop the ability to resist antibiotics, the problem is the length between antibiotic introduction and resistance development is shortening because of the widespread and overuse of antibiotics, especially in the livestock industry. The goal of this study was to develop the best manure management practices balancing the benefits of antibiotics in livestock and animal manure and their impact on the environment. In particular, we monitored, using field-scale and laboratory studies, the effects of manure application methods, on-site manure treatment methods, manure application seasons, and manure-rainfall time gaps on antibiotic loss through surface runoff, antibiotic distribution and movement in soil, antibiotic dissipation in soil, and development of antibiotic resistance. In order to reduce the amount of antibiotic loss with surface runoff from manure-applied fields to the surrounding environment, farmers are recommended to 1) compost manure before application, 2) watch the forecast to apply manure at least 3 days before a subsequent rainfall, and 3) use the subsurface injection method, especially when the soil is wet (spring season). The majority of applied antibiotics remained in soil. All tested antibiotics showed a similar dissipation pattern with the fastest rate during the first two weeks after manure application, then slowing down. Although the half-life of tested antibiotics in soil was short (<21 days), some remained detectable even at 6 months after a single manure application. Besides, the subsurface injection slits acted as a hot zone with a concentrated amount of antibiotics, manure microbes, and antibiotic resistance. The results provide recommendations for policy makers, manure managers, and farmers to maximize benefits of manure as fertilizer while minimizing the spread of manure-associated antibiotics to surrounding water, soil, and plants.

Forest roads and stream crossings have the potential to be sources of sediment from forest operations. Recent litigation has renewed interest in furthering research related to forest road Best Management Practices (BMPs). Three legacy (100 year old) forest road stream crossings were monitored for suspended sediment for nine months before and six months after upgrading three unimproved ford crossings with one bridge, one culvert, and one improved ford. During construction, rainfall simulation was utilized to estimate the sediment contribution of each crossing with minimal BMPs (BMP-), BMPs equal to state recommendations (BMP), and BMPs beyond state recommendations (BMP+). Construction costs were recorded to quantify the change in cost with a change in BMP level. Three levels of rainfall simulation were used on each BMP treatment for each crossing resulting in 27 rainfall simulations. Water samples collected by an automatic sampler downstream of the crossings were analyzed for suspended sediment. Pre - and post- construction time periods were compared to assess how the improved crossings altered total suspended sediment concentrations downstream of the crossings. The number of stream crossings constructed per year in Virginia was also estimated using satellite imagery on 400 harvest tracts. Site visits were conducted on 240 harvest tracts where data were collected on the presence of crossings, the types of crossings, and the level of BMP implementation. Rainfall simulation experiments showed decreased sediment with increased BMP level and daily total suspended sediment concentrations measured over 15 months showed a decrease in mean daily sediment concentration after construction of the bridge and culvert crossings. There was no decrease in sediment concentration for the ford crossing. Statewide crossing construction and BMP implementation rates were estimated. Approximately 67% of the audited stream crossings were characterized as having BMPs that were equal to or beyond state recommendations. Increased BMPs and upgrading of stream crossings resulted in decreased total suspended sediment. However, increased BMP implementation also increased stream crossing construction costs. Effectiveness of increased levels of BMPs and the pre and post construction analysis suggests the improvement of a legacy stream crossing may reduce total suspended sediment concentrations. / Ph. D.

Interest in BMP-related logger education and training has increased dramatically in recent years. Harvest planning is a critical component of forestry water quality BMPs. All states’ BMP manuals recommend written timber harvest plans, and several states require them by law. The objective of this study was to evaluate the impact of harvest planning training and the use of written timber harvest plans on BMP compliance, landowner satisfaction and weather-related downtime in the Virginia Piedmont. Nine randomly chosen loggers (study group) from the Virginia Piedmont participated in two days of intensive harvest planning field training. Nine additional loggers were randomly chosen as a control group. Study loggers prepared and followed written timber harvest plans for the 29 tracts they harvested during the 8-month study period immediately following the training. Study Group loggers outperformed Control Group loggers for mean BMP compliance (90% vs. 86%), mean landowner satisfaction (3.54/4.0 vs. 3.27/4.0), and mean weather-related downtime (10% vs. 13%). Absolute scores for all evaluation criteria for both groups were good, and differences, though statistically significant, were relatively small, leading to conclusions that: • Loggers in the Virginia Piedmont are generally doing a good job. • Loggers in the Virginia Piedmont are planning their operations, whether a written plan is required or not. • Harvest planning training and written harvest plans can marginally improve BMP compliance, landowner satisfaction and weather-related downtime, even for loggers who are already performing well. / Master of Science

Three watersheds located in Westmoreland County, Virginia were monitored to evaluate effectiveness of forestry best management practices (BMPs) for minimizing hydrologic and water quality impacts associated with timber harvesting. One watershed was clear-cut without implementation of BMPs, one watershed was clear-cut with the implementation of BMPs and the third watershed was left undisturbed as a control. The 27 months of pre-harvest monitoring data and 17 months of post-harvest monitoring data were compared using the paired watershed regression analysis and the minimum detectable change (MDC) statistic. Analysis of the hydrologic data showed that peak discharge rates were not impacted by harvesting, regardless of whether BMPs were implemented. Harvesting with or without the implementation of BMPs resulted in no statistically significant change in stormflow volume. BMP implementation was found to be effective in minimizing harvesting impacts on stormflow total suspended solids (TSS), ammonia, total Kjeldahl nitrogen (TKN), total nitrogen (TN), sediment-bound nitrogen and total phosphorous (TP) concentrations and total flow TSS and TP concentrations. BMP implementation was also effective in minimizing harvesting impacts on stormflow TSS, TKN, sediment-bound nitrogen, TP and sediment-bound phosphorous loadings and total ammonia loading. The BMPs were not effective in reducing nitrate concentrations and loadings. The BROOK90 forest hydrology model was used to predict the site hydrology. Model predictions compared favorably with streamflow measurements from watersheds QN3 and QN4 until the time of harvest, but did not predict streamflows as accurately for the control watershed, QN5. / Master of Science

Rainwater harvesting (RWH) refers to the collection of rainwater for subsequent on-site use. Rainwater is most often used for non-potable purposes including toilet flushing, laundering, landscape and commercial crop irrigation, industry, fire fighting, air-conditioning, and vehicle-washing. This study evaluates the potential impacts of RWH on residential housing on Virginia Tech campus in southwestern Virginia in regards to potable water offset, energy conservation, stormwater mitigation, carbon emission reduction, and financial savings. Potential rainwater collection was estimated from three simulations used to approximate the maximum, average, and minimum range of annual precipitation. Collected rainwater estimates were used to calculate the impacts on the areas of interest. Cumulatively, the sample buildings can collect 3.4 to 5.3 millions of gallons of rainwater — offsetting potable water use and reducing stormwater by an equivalent amount, save 320 to 1842 kWh of energy, and reduce carbon emissions by 650 to 3650 pounds annually. Cumulative savings for the nine buildings from combined water and energy offsets range between $5751 and $9005 USD, not substantial enough to serve as the sole basis of RWH implementation on campus. A significant advantage of RWH relates to the management and improvement of the Stroubles Creek watershed in which the majority of the campus sits. Additionally, RWH implementation would benefit sustainable initiatives and provide Virginia Tech additional opportunities for conservation incentives and environmental stewardship funding. / Master of Science