A method was developed to approximate the diameter distribution of unthinned plantations of loblolly pine from whole stand predictions of stand attributes. The beta probability density function (pdf) and the Weibull pdf were used as models for the diameter distribution function for estimating a stand attribute (such as average diameter at breast height (dbh) or total volume per acre) and the whole stand estimation of the attribute was defined. The given estimates of k stand attributes from whole stand models, the k parameter of the pdf were estimated (recovered). Two types of parameter recovery models were constructed. The first used equations for the non-central moments of dbh. For the beta pdf, equations for the predicted first moment (average dbh) and second moment (basal area per acre/(0.005454 N)) were used to compute the analytic solution for parameter α and β. The endpoints of the pdf were defined to be the predicted minimum dbh minus 0. 6 inches and maximum dbh plus 0.6. In the case of the Weibull pdf, the parameter c was solved from the coefficient of variation which itself was computed from the predicted first and second non-central moments. Then given this value of c, b was solved for using the predicted average dbh. The parameter a was set equal to one-half predicted minimum dbh. The second type of parameter recovery model used volume as one of the stand attributes used to solve for the parameters. Due to failure of the numerical solution algorithms to consistently converge to a solution for the parameters, the beta pdf could not be used. For the Weibull though solutions were always possible. The parameters a and c were estimated as before and b was then solved using the diameter distribution yield equation for total volume per acre. The three models described above achieved a solution for the parameters 100% of the time. Comparison of the three using Kolmogorov-Smirnov statistics showed all three to be nearly equal in their ability to approximate the diameter distribution of stands. When compared to other conventional diameter distribution prediction methods (Burkhart and Strub 1974 and Smalley and Bailey 1974a), the parameter recovery models proved as good as or better than these other methods. In unthinned loblolly pine plantations the parameter recovery models proved to be a feasible alternative for predicting diameter distributions. The major advantage of the models is the numerical compatibility of the whole stand estimates of stand attributes and the diameter distribution estimates. Thus given whole stand estimates, such as basal area per acre or total cubic-foot volume per acre, the distribution of these attributes by diameter classes can be obtained. / Ph. D.

Loblolly pine is an important managed tree species within the southeastern United States, and better understanding spatial patterns in its productivity has potential to contribute to both modeling and management of the species. Using recently-created pine management maps specific to Virginia and empirical relationships predicting pine LAI from the Landsat satellite, we conducted a statewide analysis of temporal patterns in stand-level southern pine leaf area index (LAI) following clear-cut and planting. Here, using 28 years of Landsat time-series data for 13,140 stands that were clear-cut between 2014-2017, we examined 1) when LAI peaked over the rotation, and 2) how LAI in each stand compared to a recommended fertilization threshold of 3.5 LAI. We found that, on average, winter LAI reached a maximum of 2.02., which can be approximately doubled to give a summer LAI of 4.04, and within stand peak occurred between years 13 and 15. We also found that around 45.8% of stands achieved an LAI value higher than 3.5: a fertilization threshold recommended for managed stands in Virginia. The dataset produced by our analysis will bolster information required for modeling loblolly pines as a plant functional type in regional land simulations, and the finding that most stands are below the recommended LAI fertilization threshold will fuel further management-motivated research. / Master of Science / Management of pines in the southeastern U.S. contributes to the region's economy and carbon sequestration potential. In this study, we used Virginia forest harvest maps to identify individual patches (stands) of pine forest which had each gone through a full harvest life cycle (rotation). With unique managed pine stands identified, we used satellite imagery to estimate growth of canopy leaf area over time within each stand, using a metric called leaf area index (LAI). We identified 13,140 separate stands, each with up to 28 years of available data. We took the first full-state census of areas of managed pines in Virginia, and their leaf area development. We acquired one LAI measurement from February of each year, for each stand in Virginia. Using February LAI for each of our stands, we found that an average stand in VA has a maximum winter LAI of 2.02 (meaning an approximate maximum summer LAI of 4.04), and that stands generally reached their peak LAI after around 14 years of growth. It is recommended, in VA, that a landowner fertilize their stand in the middle of a harvest rotation if summer peak LAI is under 3.5, at stand closure. We found that at ten years of stand age, 45.8% of stands were estimated to reach above this threshold. Since this study's dataset is the most comprehensive LAI dataset for managed pines in VA, it may be used to improve management outcomes as well as understand pine productivity for land surface modeling purposes.

Mathematical methods of assessing the spatial autocorrelation associated with individual tree characteristics in forest stands were identified. These measures were used to investigate the spatial autocorrelation of discrete tree characteristics including the species, product, and defect classifications. With the exception of the species classification, none of the discrete tree characteristics examined showed any evidence of significant (α = 0.05) levels of spatial autocorrelation in loblolly pine stands. The significant autocorrelation of the species classification was probably due to past stand history or microsite variability rather than overall stand conditions such as age, density, or percent pine. The relationship between the level of spatial autocorrelation associated with basal area and several descriptive stand characteristics was also examined. No strong relationships were identified but trends were noticed between the autocorrelation measures and measures of stand competition such as basal area and crown competition factor. The measures of spatial association indicate positive autocorrelation between the characteristics of neighboring trees at very low levels of competition with the autocorrelation becoming increasingly negative as competition increases. At extremely high levels of competition, the spatial autocorrelation measures become positive again, reflecting the stagnated condition of the stand. Methods were developed, using the measures of spatial autocorrelation, to assign characteristics to individual trees in computer generated stands. These methods, applicable for discrete or continuous characteristics; assign the characteristics to individual trees depending on the spatial location of the individual tree and the locations and characteristics of its neighbors. / Ph. D.

Yellow poplar (Liriodendron tulipifera L.) and loblolly pine (Pinus taeda L.), families 2-8 and 540, seedlings were fumigated with 0.07 ppm ozone, 0.06 ppm sulfur dioxide 0.07 ppm ozone + 0.06 ppm sulfur dioxide, 0.06 ppm sulfur dioxide + 0.10 ppm nitrogen dioxide and 0.07 ppm ozone + 0.06 ppm sulfur dioxide + 0.10 ppm nitrogen dioxide for 35 consecutive days, 6 hr/day. Control seedlings received charcoal-filtered air. Ozone or sulfur dioxide did not significantly affect height growth or dry weight of yellow poplar seedlings. All other treatments significantly reduced height growth and dry weight after 2 weeks of fumigation. Height growth effects of loblolly pine families were not repeatable from one year to the next in replicate experiments and weekly growth trends in the two experiments were reversed. Environmental factors related to time of year were thought to be involved with this growth trend reversal. Root dry weight was found to be a more sensitive indicator of air pollution stress than either shoot dry weight, height growth or visible symptoms. Loblolly families 2-8 and 540 were not found to be differentially sensitive to pollutant treatments. Loblolly pine seedlings, nonmycorrhizal and mycorrhizal with Pisolithus tinctorius, were fumigated with 0.07 ppm ozone and 0.06 ppm sulfur dioxide singly and in combination, 6 hr/day, for 35 consecutive days. Height growth of mycorrhizal and nonmycorrhizal seedlings was not affected by fumigation. Root dry weight of nonmycorrhizal seedlings was significantly reduced by all pollutant treatments in two replicate experiments. A similar reduction in root dry weight of mycorrhizal seedlings did not occur. Shoot dry weight of nonmycorrhizal seedlings was reduced in four of six pollutant treatments, and in one of six treatments of mycorrhizal seedlings. Mycorrhizal formation was extensive regardless of treatment. Apparent photosynthesis, measured every 4 days, was variable and significant differences among treatments did not occur. Total reducing sugar concentrations of roots were an inconclusive indicator of air pollutant stress. / Ph. D.

Short term studies have suggested that ground based timber harvesting on wet sites can alter soil properties and inhibit early survival and growth of seedlings. Persistence of such negative effects may translate to losses in forest productivity over a rotation. During the fall and winter of 1989, numerous salvage logging operations were conducted during high soil moisture conditions on wet pine flats in the lower coastal plain of South Carolina following Hurricane Hugo. A long-term experiment (split-plot within an unbalanced randomized complete block design) allowed assessment of long term effects of rutted and compacted primary skid trails and subsequent site preparation on soil properties and loblolly pine (Pinus taeda L.) productivity. The experiment had 12 blocks, four levels of site preparation as the whole plot factor (bedding, disking with bedding, disking, and no site preparation), and two levels of traffic as the subplot factor (primary skid trail, no obvious traffic). After 23 years, bedding and disking with bedding treatments effectively enhanced soil physical properties and stand productivity via promoting greater survival and stocking, but had little effect on the size of individual trees relative to disking and no site preparation treatments. Primary skid trails significantly reduced the size of individual trees, but had no appreciable long term effects on soil properties or stand productivity after 23 years. The study suggests that bedding is the most efficient practice to enhance soil properties, seedling survival, and stand productivity on wet sites. However, site preparation is not necessary for these soils and sites, if strictly intended to restore soil properties and stand productivity in primary skid trails. Reduction in individual tree sizes on primary skid trails emphasizes benefits in minimizing the spatial extent of disturbance. / Master of Science / Heavy equipment traffic associated with ground-based timber harvesting has potential to alter soil properties resulting in lower productivity of the subsequent forest. Various soil tillage techniques have been suggested to offset changes in soil properties and forest productivity on disturbed soils, and to enhance soil properties and forest productivity on undisturbed soils. An experiment was conducted on low-lying Atlantic Coastal Plain sites to compare the effects of four soil tillage treatments (bedding, disking, disking with bedding, no tillage) on soil properties and forest productivity 23 years after treatments were installed. Bedding displaces soil from furrows into continuous, linear mounds called beds, such that bed surfaces are above the original soil surface. Disking is a tillage practice commonly implemented in agriculture. For the disking with bedding treatment, plots were disked followed by bedding. The no tillage treatment served as a control. Additionally, the experiment provided comparison of soil properties and forest productivity between soils heavily disturbed by logging activities and relatively undisturbed soils. Bedding and disking with bedding created favorable, localized soil conditions that promoted greater loblolly pine survival which translated to approximately double the total stand volume per unit area relative to disking and no tillage treatments. Differences in the sizes of individual trees among tillage treatments were minimal. Heavily disturbed soils and soils undisturbed by logging activity were similar in terms of soil properties and loblolly pine volume per unit area; however, individual trees were smaller on heavily disturbed soils. The implications of this study provide practical guidance for forest management decisions. Of treatments compared, bedding is the most efficient to increase total stand productivity on poorly drained sites. Disking with bedding offers no additional benefits, but is more expensive to implement. Results also imply that soils disturbed by logging have potential to recover over time such that long term forest productivity is sustained. However, the reduction in individual tree sizes emphasizes benefits of minimizing soil disturbance during timber harvests.

Biosolids, materials resulting from domestic sewage treatment, are surface applied to forest soils to increase nutrient availability. Retaining streamside management zones (SMZs) can limit nutrient pollution of streams. We delineated 15 m SMZs along three intermittent streams in an 18-year-old Pinus taeda L. plantation. We applied biosolids outside the SMZ on one side of each of the streams maintaining the other side of the stream as control. We collected water samples from the three treated and six reference streams as well as from the perennial stream both upstream and downstream from the intermittent streams for 12 months following treatment. Along transects perpendicular to the treated streams, we collected overland flow samples, soil solution samples at 60 cm and extracts from ion exchange membranes (IEMs) placed in the surface soil. We found elevated nitrate concentrations outside the SMZ in the treated side soil solution samples, in which concentrations remained below 1.5 mg L-1. Nutrient concentrations outside the SMZ in treated side IEM extracts increased following biosolids application, returning to near control levels after one year. Nutrient concentrations in IEM extracts were not elevated adjacent to the streams. We observed elevated phosphorus concentrations adjacent to the stream in overland flow during one period on the treated side of the stream. Stream nutrient concentrations showed few differences downstream from the treatment with concentrations below 1.5 mg L-1. Our results indicate that a 15 m SMZ protected streams from nutrient pollution for the first year following biosolids application to adjacent forestlands. / 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

Nitrogen deficiency is characteristic of many mid-rotation loblolly pine (Pinus taeda L.) plantations in the Piedmont region of the southeastern USA. Fertilization with urea is the most common method used to correct this deficiency. Previous studies show that urea fertilization produces a rapid pulse of available nitrogen (N) with only a portion being utilized by plantation trees. Controlled release fertilizers release available N more slowly over a longer period of time and therefore may result in greater uptake efficiency. The objective of this study was to compare Nitroform®, a urea-formaldehyde controlled release N fertilizer versus urea and a control by measuring the effects of the two fertilizer treatments on N availability and loss as: total KCl extractable-N, total ion exchange membrane-N (IEM-N), N mineralization, and N volatilization, in a mid-rotation loblolly pine plantation in the Piedmont of Virginia. In addition, mid-summer and mid-winter fertilizations were compared to assess fertilizer uptake as a function of season. After the summer fertilization, Nitroform® significantly increased total KCl-extractable N, IEM-N, and N mineralization for two to three months over urea and the control. Three hundred times more N volatilized from urea than from controlled release Nitroform®. Interestingly, seven months after the summer application, the controlled release Nitroform® showed marked immobilization for three months while urea demonstrated greater N mineralization. After the winter application, fertilization with urea demonstrated greater soil inorganic N concentrations for two to three months over Nitroform®, very little N was immobilized, and volatilization was only 10 times that of Nitroform®. After summer and winter fertilizations, both fertilizer treatments significantly increased soil inorganic N concentrations and N volatilization over controls, however did not significantly increase N mineralization over controls when average response was tested over the entire sampling period. In addition to the fertilizer effects measured, a thinning only treatment was also incorporated into this study with soil N-availability indices compared to a control with no thinning or fertilization. The results from the thinning only treatment demonstrated no significant increases over the control in total KCl extractable-N, IEM-N, N-mineralization, or N volatilization when average responses were tested over the entire sampling period. / Master of Science

This study compares financially optimal uneven-aged and even-aged silvicultural regimes of loblolly pine (Pinus Taeda). Uneven-aged regimes which maximize net present value (NPV) are found by quantifying the effects of diameter distribution (Q factor), maximum diameter, cutting cycle, and residual basal area on NPV. For the benchmark inputs, the regime yielding the highest NPV had a maximum diameter of 12 inches, residual basal area of 45 ft²/acre, and a cutting cycle of 11 years. Financially optimal even-aged regimes are taken from published literature of even-aged silviculture. Even-aged and uneven-aged silvicultural regimes are simulated starting from, 1) bare land, 2) a balanced uneven-aged loblolly pine stand, and 3) a mature even-aged loblolly pine stand. For the three starting conditions and selected benchmark variable values, simulation of even-aged silviculture yields NPVs of $877, $2,152 and $3,400 per acre and simulation of uneven-aged silviculture yields NPVs of $644, $2,084, and $2,569 per acre. Sensitivity analysis shows, for the levels of the variables tested, that even-aged silviculture yields higher NPVs than uneven-aged silviculture when starting from bare land or from a mature even-aged stand. When starting from an uneven-aged stand, for the variable values tested, uneven and even-aged silviculture are financially very competitive. Aside from the aesthetic benefits of avoiding clearcutting under uneven-aged silviculture, non-timber considerations between loblolly pine silvicultural systems are not well documented. Resource professionals hold opinions often in direct conflict with each other regarding the non-timber costs and benefits of even-aged and uneven-aged silviculture when considering wildlife, soil and water, and catastrophic damage events. / Master of Science

Mid-rotation fertilization and vegetation control are some of the most common silvicultural treatments in loblolly pine (Pinus taeda L.) plantations in the southeastern United States. Competing vegetation is commonly thought to sequester fertilizer nitrogen (N) and reduce the potential growth response to a mid-rotation fertilization treatment. This experiment aims to identify what proportion of applied N fertilizer is retained in the crop tree pine foliage, and the degree to which understory vegetation is competing for this resource. Our mid-rotation loblolly pine plantation received an application of 15N fertilization (urea 365 kg/ha, at 46% N by weight, i.e. 168 kg/ha of N) and a portion of plots received an understory vegetation control (basal spray application of triclopyr; 13.6% active ingredient) treatment either before fertilization or not at all. One-year post-fertilization, 15N contents within pine foliage, leaf fall/leaf litter, forest floor, and soil were measured, as was competing vegetation presence. There was significant variation in applied nitrogen acquisition among the different ecosystem components measured, with 0-15 cm soils retaining a majority at 32-37% added 15N. Differences in fertilizer N acquisition in pine foliage between plots with and without understory vegetation control was marginally significant (p = 0.06) with pine foliage in plots without understory vegetation capturing greater 15N (4.3% greater). Red maple (Acer rubrum) and oak species (Quercus spp.) were the most common competitors but neither had a uniquely pronounced effect on pine nitrogen sequestration. My data indicate that increasing competition reduces fertilizer N foliar concentrations in crop pine trees but at a modest rate and equally across species groups. An unrefined threshold determining when fertilizer N capture in crop pine trees was affected was found at 3.1 m2/ha of competing vegetation basal area. This site will continue to be monitored over time to assess fertilizer N retention in loblolly pine each year after fertilization and evaluate the fertilizer N capture within competing vegetation. / Master of Science / Some of the most prevalent management practices for mid-rotation (age 15, i.e., roughly halfway through a crop cycle) loblolly pine (Pinus taeda L.) plantations in the southeastern United States are fertilization and vegetation control. Nitrogen (N) is consistently one of the most limiting factors to productivity. The addition of N via fertilization is therefore a common forestry practice. However, when a stand is fertilized, the added resource is partitioned and cycled throughout the ecosystem. It is presumed that the amount of fertilizer N obtained by crop trees in a plantation is dependent on the level of competing vegetation (i.e., weed-trees and shrubs) present on site. Controlling competing vegetation prior to fertilization may therefore be warranted under certain conditions. To date, the amount of competing vegetation where it begins to impact fertilizer uptake by the crop tree is unknown. This study aims to elucidate this competing vegetation threshold to better inform mid-rotation management of loblolly pine plantations. This study examined applied fertilizer N capture in ecosystem components with varying levels of understory vegetation, and found more fertilizer N in pine foliage when understory vegetation was completely removed prior to fertilization. No single understory hardwood weed species had a uniquely strong influence on crop tree productivity uptake. Plots that ranked in the upper third in competing vegetation presence did have significantly less foliar fertilizer N in the pine crop trees. Additional replication of this study would be necessary to determine a universal threshold of competing vegetation which would trigger the removal of competing vegetation prior to fertilization.