Managed loblolly pine (Pinus taeda) stands are common in the southeastern United States and provide young forest conditions for early successional breeding birds. Common pine management practices (e.g. hardwood control) and novel practices (e.g. switchgrass [Panicum virgatum] intercropping), may influence breeding bird use. I evaluated breeding bird abundance, diversity, and resource use within loblolly stands treated to control hardwood species, intercropped with switchgrass, and with no additional management. Hardwood control and switchgrass intercropping both decreased hardwoods and shrubs, and increased forbs. Switchgrass intercropping increased some early successional bird abundances. However, diversity was not different among treatments. Switchgrass intercropping increased 13C:12C in birds and vegetation; both hardwood control and switchgrass intercropping increased 15N:14N in birds and vegetation. Birds moved freely among stands of different ages and management practices. My results suggest these practices improve conditions for some early successional birds and may help maintain ecological value of loblolly stands for birds.

Woody competition during mid-rotation limits available nutrients to crop species. Mid-rotation competition control was evaluated to determine if applications would result in significant increase in growth. Two studies were initiated using herbicides and prescribed burning on mid-rotation loblolly pine plantations. The first study contained afforested stands in Mississippi. Combination of imazapyr and burn was applied. The second study contained reforested sites in Mississippi. Treatments consisted of imazapyr and burn, imazapyr only, burn only, and a control. Five-year post-treatment measurements for the first study showed no significant treatment differences in height, diameter, basal area, or volume growth. Nine-year post-treatment measurements for the second study showed no significant differences in growth using the same measurements. Although previous research has documented significant growth responses to mid-rotation competition control, results from this study demonstrate that increased growth does not always result from mid-rotation competition control, suggesting initial site conditions may dictate degree of response.

Increased growth rates, wood quality, and disease resistance have been accomplished within loblolly pine (Pinus taeda L.) through genetic selection and improved management practices. Genetic engineering of trees has the potential to further improve these selections but also needs to be tested. Two studies were conducted. Study one compares three levels of genetic improvement: Mass-Control Pollinated (MCP), Second Generation Op (2nd gen), and Varietal Material. After three years the MCP material had larger mean heights, mean diameters, and mean volume than the other two genetic entities. However the top five performing varietals were about 0.5 feet taller than the MCP material. Study two tested two contrasting loblolly pine ideotypes across different spacings and management intensities. After two years the crop tree ideotype and the intensive management plots had larger mean heights, mean ground-line diameters, mean volumes, and mean crown widths. Mean branch angle differed significantly between the two crown ideotypes.

This study examined the effect of manipulating forest floor and harvest residue inputs on nutrient availability and carbon content in the context of intensive forest management. Treatments were removal and addition of forest floor and slash, and a reference. Tree volume, litterfall, and root biomass were measured to assess aboveground productivity and soil moisture and temperature, available nitrogen and phosphorus, O-horizon, and mineral soil for below ground processes. Organic matter additions increased stand bole volume, carbon at 20-60cm, and total nitrogen in the mineral soil. Severely removing the floor and harvest residues did not result in any large differences in below or above ground productivity, soil carbon or nitrogen pools. Removing a potential nutrient pool did not severely affect stand productivity through mid-rotation but could be a concern in subsequent rotations.

Bareroot and containerized loblolly pine (Pinus taeda L.) were planted in December 2016 and February 2017 to compare performance across four sites in South Carolina and Georgia. Main treatments analyzed for growth differences were stocktype, genetics, and planting date. Analysis of variance results showed significant growth differences after two growing seasons for containerized over bareroot seedlings, for control-pollinated seedlings over open-pollinated and varietal seedlings, and for December-planted seedlings over February-planted seedlings. Control–pollinated seedlings demonstrated the most incremental growth between ages one and two. Site conditions dictated seedling survival to a certain degree, and bareroot seedling growth was slightly better than containerized on the least stressful site. Results uncover important trends for main effects of stocktype, genetics, and planting date, but also underscore the importance for land managers to avoid blanket reforestation prescriptions, with more emphasis placed on site-specific conditions.

There have been several studies that aim to determine the most superior Weibull parameter recovery approach of specifying a given forest stand’s Weibull diameter distribution, but no consensus has been made. The lack of agreement could be attributed to studies using different moments/percentile prediction models as well as using different plot size data. This study investigates how plot size and prediction model form affects the performance for moments, hybrid, and percentile Weibull parameter recovery approaches. Five plot sizes and three moments/percentile prediction models were used to determine their effects. Weibull parameters were calculated using each recovery method for each plot size and moments/percentile prediction model combination. Each combination’s diameter distribution was recovered and assessed using absolute error index. Results showed that plot size affected rank of precision for parameter recovery methods. Findings suggest that order statistics may be important in recovering Weibull distribution parameters from stand diameter summary statistics.

My research is focused on advancing understanding of the genomes of two important distantly related conifer species, loblolly pine (Pinus taeda L.) and bald cypress (Taxodium distichum (L.) Rich. var. distichum). Loblolly pine is the most commercially important tree crop in the United States, the major source of pulpwood for paper manufacturing, a source of quality lumber, a prime bioenergy feedstock, and an important part of the ecosystem of the southeastern U.S. Bald cypress is the dominant tree species in the aptly named ¡°cypress swamps¡± of the South.Its ecological importance to the wetlands of the southern U.S. is immeasurable. Moreover, bald cypress is a popular ornamental due to its attractive appearance and extreme resistance to pests, pathogens, and weather. Maintaining the security and productiveness of these important crop/forest species in the face of new pest, pathogen and environmental threats will require a better understanding of their genes and the structures of their genomes. We have conducted a study of loblolly pine and bald cypress in which Cot analysis and DNA sequencing of Cotiltered DNA were utilized to study genome structure. Cot analysis revealed that loblolly pine and bald cypress genomes are each composed of three major kinetic components which we have deemed highly repetitive (HR), moderately repetitive (MR), and single/low copy (SL). In loblolly pine, the HR, MR, and SL components account for 57, 24, and 10%, of genomic DNA, respectively. Of note 2.71% of random genomic sequences (i.e., 580 Mb, an amount roughly three times that of the Arabidopsis genome) show significant (bit score ≥ 60) homology to mRNA sequences. This result suggests that the loblolly pine genome contains many genes or pseudogenes, and/or gene duplications. In bald cypress, the HR, MR, and SL components account for 52, 38, and 4%, of genomic DNA, respectively. Sample sequencing was performed only on the HR component of bald cypress; sequence analysis shows only 0.81% of HR sequence reads with homology to mRNA sequences. My research provides insight into the evolution of these distant conifers and key sequence data that should greatly facilitate ongoing molecular breeding programs.

Studies were conducted to determine the incidence and severity of Heterobasidion annosum (Fr.) Bref. root rot in loblolly pine (Pinus taeda L.) unthinned plantations and subsoiled seed orchards and to demonstrate the potential for direct root colonization by percolated basidiospores. Twenty-two 0.02 ha circular plots were installed in nine unthinned loblolly pine plantations in Virginia. Five plantations were located on sites classified as high hazard for annosum root rot while four plantations were located on low hazard sites. Bulldozer excavation of the root systems permitted extensive analysis of annosum root rot incidence and severity which was substantiated by isolation of the asexual stage of the fungus from symptomatic resinous and stringy-decayed roots. On low hazard sites, 10 of 300 trees (3.3 percent) were colonized by H. annosum with 2 trees (0.7 percent) severely colonized ( > 1 percent of the total root system mass). On high hazard sites, 29 of 348 trees (8.3 percent) were colonized with 5 trees (1.4 percent) severely colonized. On low hazard sites, the predominant colonization symptom was stringy decay which indicated an older established disease situation as opposed to colonized trees on high hazard sites which exhibited resin-soaking characteristic of more recent infection and colonization. No basidiocarps were observed on any trees on low hazard plots while only 2 trees exhibited conks on high hazard sites. Mean radial increment growth differences between H. annosumcolonized and noncolonized trees were analyzed using the Duncan's Multiple Range test and for the 10-year period prior to excavation no significant growth reduction was observed. Due to low incidence and severity of annosum root rot in unthinned loblolly pine plantations and the absence of reduced radial increment growth, the disease is not a primary management consideration, especially on low hazard sites. However, the disease may be of secondary importance in managing first-generation unthinned loblolly pine plantations on high hazard sites due to inoculum production from residual stumps of H. annosum trees removed during thinning. The root systems of 2, 20 and 30 loblolly pines at the Chesapeake Corporation, Virginia Division of Forestry and Union Camp Corporation seed orchards, respectively, were excavated with a backhoe to permit intensive analysis of subsoiled roots for annosum root rot incidence and severity. The absence of wound callus, lack of adventitious root formation and the presence of a resin-soaked band greater than approximately 6 mm wide at the wound surface were three criteria for determining whether a lateral primary root had failed to heal following subsoiling. Soil texture was closely associated with the incidence and severity of general root disease as the wetter soil conditions at the Chesapeake Corporation seed orchard probably afforded a more amenable environment for the healing of subsoiled roots. Sandy, drought-susceptible soils at the Union Camp Corporation and Virginia Division of Forestry seed orchards were associated with the higher incidence and severity of root disease among subsoiled lateral primary roots. The asexual stage of H. annosum was not successfully isolated from resin soaked subsoiled root tissue at any of the three orchards. Duncan's Multiple Range analysis demonstrated that mean radial increment growth was significantly decreased among healthy and declining subsoiled trees at the three orchards. At the Union Camp Corporation orchard, when healthy and declining trees were subsoiled they exhibited significantly less radial increment growth than their respective control counterparts. Loblolly pine root segments were inoculated with a suspension of H. annosum basidiospores and observed using scanning electron microscopy. Appressorial-like structures occurred at distal ends of elongated germ tubes demonstrating probable direct infection of loblolly pine root segments. / Ph. D.

Understory forage production, species composition, and nutrient concentrations were studied in relation to overstory structure and site characteristics in thinned loblolly pine (Pinus taeda) plantations in the Virginia Piedmont. Stands exhibited a wide range in overstory basal areas (18.8 to 43.5 m²/ha) and site indices (14.2 to 23.8 m at base age 25 years). Understory forage production for the 0 to 2 m stratum averaged 610 kg/ha and ranged from 154 to 1690 kg/ha. Initially, differential models were used to develop prediction equations relating understory production to overstory characteristics, but an empirical prediction equation proved to be somewhat superior. Forage production was most predictable from total overstory basal area, canopy cover, and slope position. Understory species composition was analyzed with respect to overstory structural and site gradients, using vegetation ordination techniques. Species composition was less closely related to these gradients than was production; however, the greatest species diversity appeared to occur during the period following thinning but before crown closure, when successional and mid-tolerant species coexisted. Nutrient concentrations in forage material averaged 4643 cal/g for gross energy, 38.3 percent for invitro dry matter digestibility by white-tailed deer (Odoooiteus virginiana) and 8.4 percent for crude protein. There were no apparent trends of these nutrient concentrations with respect to overstory structural or site characteristics. Forage based carrying capacities for white-tailed deer were computed using values from this study for production and nutrient concentrations, and values from the literature for deer forage preferences and nutrient requirements. Results indicated that the pine habitat could support 0.03 to 0.19 lactating does per ha during the summer season, and that energy and not protein is likely the limiting nutritive parameter. Suggestions are made for future research in pine overstory-understory and wildlife habitat relationships. These include the use of experimental overstory manipulation followed by periodic remeasurements to directly observe changes in understory production and species composition, intensive sampling to determine specific local wildlife forage preferences, and the quantification of wildlife movements and population dynamics. / Ph. D.

The objective of this study was to develop diameter/basal area increment equations for loblolly pine trees in thinned and unthinned plantations on cutover, site-prepared areas. Results indicated that one set of coefficients was sufficient to estimate individual tree growth (for the three year period following thinning) on lightly thinned and heavily thinned plots. However, unthinned plots required a separate set of coefficients and therefore a separate equation to estimate growth. Diameter growth was adequately explained by some form of the following regressor variables: pine basal area, hardwood basal area, initial age, initial diameter, average height of the dominant and codominant trees, and crown ratio ( optional). Transforming the dependent variable from a function of diameter to a similar function of basal area had no apparent effect on the precision of the predicted results. Two alternative methods of predicting diameter growth were evaluated: (1) direct fitting of diameter growth, and (2) fitting a potential diameter growth equation and a modifier function. Even though the potential times modifier approach performed slightly better in terms of fitting the data, it provided unrealistic results at ages beyond the upper range of the data. After additional data are obtained at older ages, the potential times modifier approach may surpass the direct approach. However, at present, the direct diameter growth model was chosen as the final model form. / M.S.