The use of nitrogenous fertilizers in agricultural and forestry practices coupled with increased fossil fuel combustion and resulting nitrogen (N) deposition across the landscape have contributed to a near doubling of N inputs to terrestrial ecosystems.  With such dramatic changes have come adverse environmental consequences including the acidification of soil and water resources and an increased rate of biodiversity loss in both flora and fauna.  A method of rapidly predicting ecosystem susceptibility to N loss across large spatial scales would facilitate the identification of those systems most likely to contribute to potentially adverse environmental impacts.  To begin the development of such a framework, this research utilizes study sites located throughout the geographic ranges of Douglas-fir (Pseudotsuga menziesii) and loblolly pine (Pinus taeda) to explore relationships between hyperspectral remote sensing, N stable isotope ratios ("15N) and growth response to nitrogenous fertilizer.  In both species multiple linear regression models relating leaf-level reflectance to "15N showed strong predictive capabilities, with some models explaining more than 65% of the variance in "15N.  Significant correlations between "15N metrics and growth response to N fertilization were also observed in both species.  Additional exploratory analysis of the inclusion of "15N metrics with other environmental and edaphic variables to predict fertilizer growth response showed an increase in model performance with the addition of the enrichment factor (EF ="15NFol - "15NSoil).  This research demonstrates the ability of hyperspectral reflectance to predict "15N and reveals the potential of "15N to be included in future models to predict fertilizer growth response. / Master of Science

The effect of date and method of lifting on ethylene production by 1-0 loblolly pine (Pinus taeda L.) seedlings during cold storage, the dose-response relationship between ethylene and loblolly pine seedlings during cold storage, and the effect of water stress on ethylene and aminocyclopropane-1-carboxylic acid (ACC) production in two half-sib loblolly families were investigated. Seedlings stored in Kraft-Polvethvlene (K-P) bags showed a general trend of increasing ethylene concentrations from November through February, with an abrupt drop in March. Production rates may be related to the level of dormancy of the seedlings, with the peak in production corresponding to fulfillment of the chilling requirement. Ethylene concentrations within the K-P bags generally declined over the twelve weeks in cold storage. Roots produced significantly higher levels of ethylene while stored in the K-P bags; however, when incubated under light, the needles produced higher concentrations. Roots of machine-lifted seedlings produced significantly higher levels of ethylene than roots of hand-lifted seedlings. However, rates tended to moderate during storage and differences in production between HL and ML whole seedlings were not significant, which suggests that mechanical lifting is not a source of increased ethylene production. A dose-response study indicated that ethylene fumigation during cold storage tended to slightly enhance growth of outplanted seedlings. The effects of water stress on a Virginia Coastal Plain (CP) and an East Texas Drought Hardy (DH) loblolly family were also investigated. Ethylene production during severe stress (-2.8 MPa) appeared to be related to drought hardiness, with the CP seedlings producing much higher levels. Roots of both families produced greater levels of ethylene than the needles and may be due to an enhanced ability to convert 1-Aminocyclopropane-1-carboxylic acid (ACC) to ethylene. / Master of Science

Remote sensing offers many advantages to previous forest measurements, such as limiting costs and time in the field. Light detection and ranging (lidar) has been shown to enable accurate estimates of forest height. Lidar does produce precise measurements for ground elevation and forest height, where and when it is available. However, it is expensive to collect and does not have wall-to-wall coverage in the United States. In this study, we estimated height using the National Agricultural Imagery Program (NAIP) photogrammetric point clouds to create a predicted height map for managed loblolly pine stands in the southeastern United States. Recent studies have investigated the ability of digital aerial photogrammetry (DAP), and more specifically NAIP, as an alternative to lidar as a means of estimating forest height due to its lower costs, frequency of acquisition, and wall-to-wall coverage across the United States. Field-collected canopy height for 534 plots in Virginia and North Carolina were regressed against the 90th percentile derived from NAIP point clouds. The model for predicted pine height using the 90th percentile of height (P90) is predicted pine height = 1.09(P90) – 0.43. The adjusted R^2 is 0.93, and the RMSE is 1.44 m. This model is being used to produce a 5 m x 5 m canopy height model for all pine stands across Virginia, North Carolina, and Tennessee. NAIP-derived point clouds are thus a viable means of predicting canopy height in southern pines. / M.S. / Collecting accurate measurements of pine plantations is essential to managing them to maximize various ecosystem goods and services. However, it can be difficult and time-consuming to collect these measurements by hand. This study demonstrates that point clouds derived from digital stereo aerial photograms enable calculating forest height to an accuracy sufficient for pine plantation management. We developed a simple linear regression model to predict forest canopy height using the 90th percentile of the photo-derived heights above the ground in a given area. With this model, we created a map of pine plantation canopy heights (consisting of 5 m x 5 m grid cells, each containing a canopy height estimate) for pine forests in Virginia, North Carolina, and Tennessee. Digital aerial photography from the National Agricultural Imagery Program (NAIP) is repeated every three years for a given state, allowing growth to be mapped over time. Photography collected by NAIP and similar programs also has uniform acquisition parameters in a given year applicable over large regions. State- and national photography programs like NAIP are also less expensive than other data sets, like airborne laser scanning data, that enable estimation of tree height.

The effects of two forms of mid-rotation release on thinned, fertilized loblolly pine (Pinus taeda L.) plantations in Virginia were examined: aerial imazapyr and basal triclopyr application. Imazapyr measurement plots were installed in nine Piedmont and twelve Coastal Plain plantations operationally released with imazapyr, and triclopyr measurement plots were installed within a controlled fertilization/release study spanning both regions. No differences in volume were detected following triclopyr release. All release dates combined, Piedmont released areas averaged 0.06 m3/tree (18%) greater than the control and Coastal Plain released areas averaged 0.05 m3/tree (14%) greater than the control. Reductions in hardwood basal area, stem density, and shrub stratum cover were observed for both forms of release. Reductions in shrub stratum richness and diversity were also documented for imazapyr release; however, trends indicate that richness and diversity, as well as stem density and shrub stratum cover, may recover to pre-treatment levels. Herbaceous vegetation was increased on triclopyr sites, which was reflected in an elevated turkey (Meleagris gallopavo sylvestris L.) food/brood index. Following imazapyr release, habitat suitability index (HSI) values for pine warblers (Dendroica pinus L.) and black-capped chickadees (Parus atricapillus L.) increased due to reductions in canopy hardwoods and increases in snags. Reduced shrub stratum density resulted in a lower bobwhite quail (Colinus virginianus L.) cover index on imazapyr-released areas. / Master of Science

Root growth potential (RGP), the ability of a transplanted seedling to rapidly elongate existing roots and initiate new roots, is used as an indicator of seedling physiological quality. Three separate experiments were conducted on loblolly pine RGP during 1983-84 and 1984-85 using 1-0 nursery-grown seedlings. In the first study, seedlings were hand-lifted from September to April at 17-day intervals in 1983-84 and 7-day intervals in 1984-85. The RGP variation over time was related to environmental and seedling phenological changes. In addition, the new root systems were morphologically described. In the second study, changes in loblolly pine seedlings following different lift-date X cold storage duration treatments were described. These changes were compared to the RGP, shoot activity, and new root system morphology of fresh-lifted seedlings. Genetic variation in RGP on different lift-dates was quantified in the third study. Variation patterns over time among 14 half-sib loblolly pine families hand-lifted at one-month intervals were examined. Root growth potential was low in the autumn until the cessation of shoot activity. Seedlings stored poorly if put in cold storage during this time, or prior to the accumulation of at least 400 chilling hours. Seedling RGP increased in the early-winter to a late-February peak, and then decreased when spring shoot elongation occurred during the RGP tests. Similar trends over time were noted with seedlings removed from cold storage during these times. The RGP pattern over time was consistent among years and among the half-sib families, although there were some minor differences among half-sib families in the rate of increase to, and decrease from, the late-winter peak. Most new roots resulted from elongation of existing roots rather than initiation of new roots regardless of lift-date; however, when seedling metabolism was high (early autumn and late-winter) both root initiation and elongation of existing roots contributed to the new root system. In addition, the morphology of root systems of cold-stored seedlings was similar to fresh-lifted seedlings. Differences in numbers and lengths of new roots among half-sib families were due to the differential ability to produce new roots through both root initiation and elongation. / Ph. D. / incomplete_metadata

The effect of moisture stress conditioning on the drought tolerance and performance of three open-pollinated families of loblolly pine (Pinus taeda I.) during water stress were investigated. Seedlings were subjected to prolonged sublethal drought treatments which included a watered control, a moderate stress treatment (MWS, seedlings watered only when needle water potential reached -0.8 MPa) and a severe stress treatment (SWS, seedlings watered only when water potential reached -1.4 MPa). After the conditioning period, numerous physiological and morphological parameters were measured, and performance of seedlings during water stress evaluated. Significant decreases in needle osmotic potential occurred in moisture stress conditioned seedlings. As a result, turgor in conditioned seedlings was equal to or greater than control seedlings even at lower needle water potentials. Photosynthesis vas decreased greatly with reduced needle water potential. However, the MWS and SWS seedlings maintained photosynthesis to water potentials 0.15 and 0.45 MPa lower than control seedlings, respectively. This response is likely the result of both osmotic adjustment, and an acclimation of the photosynthetic process resulting in less non-stomatal inhibition of photosynthesis at low needle water potentials. Initial needle conductance and transpiration, but not photosynthesis, were reduced greatly by the conditioning treatments, and resulted in improved water-use efficiency in conditioned seedlings. The response of stomata to changing vapor pressure deficit was increased through moisture stress conditioning. Boot growth was affected more by moisture stress than shoot growth, causing a decrease in root/shoot ratio. Changes in root morphology as a result of conditioning are not likely to improve the drought tolerance of loblolly pine seedlings. SWS conditioning significantly improved the height growth increment and resulted in slightly greater shoot and root biomass of outplanted, containerized seedlings after the first growing season, despite these seedlings being much smaller at the time of planting. Differences between seed sources did occur in the experiments, with a source from Texas generally showing the least response to moisture stress conditioning. / Ph. D.

A greenhouse study was initiated to asses P uptake, growth, colonization, total mycorrhizal P levels, and mycorrhizal polyphosphate levels in loblolly pine seedlings colonized with different ectomycorrhizal fungi and grown in a Piedmont soil. The pine seedlings were inoculated with one of four species of fungi (Scleroderma aurantium, Pisolithus tinctorius, Thelephora terrestris, and Rhizopogon roseolus). Uninoculated trees served as a control. The seedlings were grown in pots containing a Cecil sandy clay loam amended with one of the following: 75% sand, 25% sand, enamended, 56 kg P ha⁻¹, 112 kg P ha⁻¹. They were harvested ten months after planting. Shoot lengths, root lengths, biomass, and total P of all plant parts including mycorrhizae were determined. Mycorrhizae of T terrestris and S aurantium were analyzed for polyphosphates, and amended soils were analyzed before planting and after harvest for double-acid extractable Al, Fe, and P. Each fungus changed postharvest extractable P, Fe, and Al differently in the soil amendments. Seedlings colonized with S. aurantium were larger, contained more P, and had a higher degree of mycorrhizal colonization. There was no significant differences in growth among seedlings colonized with the other three fungi, but all colonized seedlings were significantly larger and contained more P than uncolonized seedlings. Soil amendments had no effect on the total levels of mycorrhizal P. Mycorrhizae of S. aurantium increased polyphosphate levels with increasing available P in the soil amendments. The pattern of polyphosphate accumulation in T. terrestris among the soil treatments was less definitive. Accumulation of foliar P was affected by the interaction of soil and mycorrhizal treatments. Control seedlings were P deficient in all soil treatments although foliar P increased as soil P increased. The accumulation of foliar P seemed to reflect the ability of each symbiont to survive, uptake P, and transfer it to the seedling. Seedlings colonized with S. aurantium were P deficient in sand-amended soils, while seedlings colonized with R. roseolus were P deficient in fertilized soils. Seedlings colonized with either P. tinctorius or t. Terrestris increased foliar P with the addition of sand the addition of P. This study indicates that S. aurantium is adapted to Piedmont soils such as the Cecil, is able to extract more of the vast amount of unavailable P present in these soils, and hence stimulate growth and P levels in loblolly pine. / Ph. D.

Site preparation is a required silvicultural practice for establishing loblolly pine plantations in the Piedmont physiographic region of the southeastern U.S.; however, relatively little is known about its effect on soil and site factors that influence growth and yield. In this study, the effect of seven different site preparation prescriptions on competing vegetation, tree nutrition, and the spatial distribution of planted seedlings was examined. Three treatments had a soil tillage component and differed with respect to the number of operations employed in removing residual trees and logging slash prior to discing. One treatment involved roller chopping and broadcast burning, one an application of the herbicide glyphosate followed by a broadcast-burn, one involved shearing all raking fogging-debris into windows, and one was no site preparation prior to planting. All treatments were applied to 12 sites in the South Carolina and Georgia Piedmont. After four years in the field, 756 trees within the site preparation treatment areas were randomly selected for analysis of foliar nutrients, soil nutrients, and competing vegetation. Herbaceous, woody shrub, and hardwood competition levels were not significantly different among site preparation treatment areas after four years. However, hardwood competition levels had increased at a faster rate during the last two growing seasons on chopped and disced areas than on the other areas. Hardwood competition became the predominant factor limiting pine basal diameter when 83% of the total basal area was in hardwoods or hardwood basal area levels exceeded 3.5 m²ha⁻¹. Potassium was identified as the most limiting nutrient 38% of the time, compared to 28% for phosphorus, 14 % for nitrogen, 7% for calcium, aiid 13% for magnesium. A significant linear relationship between soil and foliar nutrients confirmed these results. No treatment effect on nutrient deficiencies was evident. Foliar nutrient critical levels were derived using the Diagnosis and Recommendation Integrated System (DRIS) and were the same as those reported in the literature for nitrogen, phosphorous, and magnesium while potassium and calcium critical levels were determined to be twice as high as those reported (0.52% and 0.19%, respectively). The spatial distribution of seedlings at planting and after 2 years was determined. Spatial patterns varied from uniform to random as the degree of logging slash removal decreased. After two years, the spatial distribution shifted toward random and clustered. The degree of change was similar in all but the herbicide burn and untreated areas, which exhibited the greatest change and whose mortality tended to be clustered. / Ph. D.

This study was established to determine the effects of competition control on loblolly pine (<i>Pinus taeda</i> L.), woody plant diversity, and wildlife habitat quality in Virginia Piedmont plantations 12-14 and 24-27 years of age. The responses of loblolly pine and competing woody vegetation in plantations 12-14 years of age were analyzed at 8 levels of competition control: total, 2/3, 1/3, or no woody stem control in combination with either total or no herbaceous vegetation control. As woody stem (plus herbaceous) control increased, pine yield increased, and percent hardwood basal area (PHWD BA) and overstory plant diversity (Shannon index (H’)) decreased. Understory percent woody cover, and woody plant species richness, evenness, and diversity (H’) were not affected at any of the competition control levels. Regression analysis was used to determine relationships between loblolly pine yield, hardwood dominance and overstory plant diversity. Pine yield was negatively correlated to PHWD BA (R²=0.74), while overstory diversity (H’) was proportional to PHWD BA (R²=0.97) and inversely related to pine yield (R²=0.77). The relationship between diversity and PHWD BA was consistent for plantations 12-14 and 24-27 years of age, while relationships of yield to PHWD BA and to diversity were altered in the older plantations. In plantations 12-14 years, competition control reduced proportions of oak and hickory species and reduced canopy structural heterogeneity, but increased proportions of other fruit bearing plant species, and increased deer browse availability and ground stratum heterogeneity. In plantations 24-27 years, competition control altered plant species composition and increased structural heterogeneity. / Master of Science

Thesis (Ph.D.)--Mississippi State University. Department of Wildlife and Fisheries. / Title from title screen. Includes bibliographical references.