Competition from hardwood species has long been considered a constraint on longleaf pine (Pinus palustris). However, evidence suggests that hardwood midstories may improve longleaf regeneration on xeric sites. Additionally, overstory retention for red-cockaded woodpecker (Leuconotopicus borealis; RCW) habitat may be inadvertently contributing to regeneration failures. Experimental plots in the North Carolina Sandhills were planted with containerized longleaf seedlings across a gradient of overstory density, and hardwoods were chemically controlled by treating at planting, treating after one year, or left untreated. Seedling survival (percent), growth (mass), and brown spot needle blight (percent infected seedlings; BSNB) were measured after two years. Seedling survival, growth, and BSNB infection rates were inversely related to overstory density. Midstory treatments did not significantly affect seedling survival, growth, or BSNB infection rates. Early results did not show facilitative effects from a hardwood midstory, but indicated overstory densities greater than 12 m2/ha negatively impact longleaf regeneration.

The Gopher Tortoise is an important component of a number of upland ecological communities throughout the southeastern U.S., but populations have experienced significant declines over the past century, largely in conjunction with the loss of longleaf pine (Pinus palustris) forests. Military installations have preserved large tracts of longleaf pine, often while implementing prescribed fires that mimic natural lightning-ignited fires (frequent low intensity fire is a necessary component of longleaf pine communities), which in turn has provided refuges for many imperiled longleaf associates, including the Gopher Tortoise. Eglin Air Force Base in the western Florida panhandle presents a unique situation in which large tracts of longleaf pine sandhill (suitable Gopher Tortoise habitat) are available, but tortoise sub-populations on base are small, and many tortoises currently inhabit treeless military testing and training ranges (test ranges) rather than typical forested sandhill. My objectives were therefore to identify factors that may have been influencing use of test ranges as habitat by gopher tortoises and that might explain observed differences in burrow densities among sites. In Chapter 1, I compared vegetation structure, composition, and burrow site selection among sites and between forested and test range vegetation types. I also attempted to identify relationships between vegetation characteristics and variation in burrow densities (a proxy for abundance within a given area) among sites. In Chapter 2, I distributed a questionnaire to other military installations throughout the southeast to identify common management techniques used to maintain testing and training areas at other tortoise-occupied military installations, as these techniques likely affect their suitability as tortoise habitat. In Chapter 3, I compared surface activity patterns of juvenile Gopher Tortoises between forested and test range vegetation types, as surface activity in these vulnerable, but important size classes may affect survival rates. I found that test ranges generally had greater herbaceous vegetation cover than forested sites (greater forage availability), were highly species diverse in terms of groundcover plants, and had herbaceous communities that shared a number of common sandhill plant species with forested sites, but also were unique in a number of ways. I also found that adult tortoises (burrow site selection) and juvenile tortoises (surface activity) may have exhibited different behaviors in novel test range vegetation types compared to individuals inhabiting more natural longleaf pine sandhill on base. However, I did not find strong evidence that current vegetation structure or composition was related to observed differences in burrow densities among sites and that other factors might have played a greater role in structuring Eglin's remnant tortoise sub-populations. / Master of Science / The Gopher Tortoise is an important component of a number of upland ecological communities throughout the southeastern U.S., but populations have experienced significant declines over the past century, largely in conjunction with the loss of longleaf pine (Pinus palustris) forests. Military installations have preserved large tracts of longleaf pine, often while implementing prescribed fires that mimic natural lightning-ignited fires (frequent low intensity fire is a necessary component of longleaf pine communities), which in turn has provided refuges for many imperiled longleaf associates, including the Gopher Tortoise. Eglin Air Force Base in the western Florida panhandle presents a unique situation in which large tracts of longleaf pine sandhill (suitable Gopher Tortoise habitat) are available, but tortoise sub-populations on base are small, and many tortoises currently inhabit treeless military testing and training ranges (test ranges) rather than typical forested sandhill. My objectives were therefore to identify factors that may have been influencing use of test ranges as habitat by gopher tortoises and that might explain observed differences in burrow densities among sites. In Chapter 1, I compared vegetation structure, composition, and burrow site selection among sites and between forested and test range vegetation types. I also attempted to identify relationships between vegetation characteristics and variation in burrow densities (a proxy for abundance within a given area) among sites. In Chapter 2, I distributed a questionnaire to other military installations throughout the southeast to identify common management techniques used to maintain testing and training areas at other tortoise-occupied military installations, as these techniques likely affect their suitability as tortoise habitat. In Chapter 3, I compared surface activity patterns of juvenile Gopher Tortoises between forested and test range vegetation types, as surface activity in these vulnerable, but important size classes may affect survival rates. I found that test ranges generally had greater herbaceous vegetation cover than forested sites (greater forage availability), were highly species diverse in terms of groundcover plants, and had herbaceous communities that shared a number of common sandhill plant species with forested sites, but also were unique in a number of ways. I also found that adult tortoises (burrow site selection) and juvenile tortoises (surface activity) may have exhibited different behaviors in novel test range vegetation types compared to individuals inhabiting more natural longleaf pine sandhill on base. However, I did not find strong evidence that current vegetation structure or composition was related to observed differences in burrow densities among sites and that other factors might have played a greater role in structuring Eglin’s remnant tortoise sub-populations.

At the Fort Bragg Military Installation, an army base in North Carolina, the habitat associations for the breeding bird species and the effects of the current prescribed fire program on the avifauna are virtually unknown. Fort Bragg encompasses one of the largest, fire-dependent longleaf pine systems existing today and is a mosaic of forested habitats. I used bird count data collected during 1994-1997 at 50-m fixed radius point count stations to examine bird species-habitat relationships in relation to fire treatment (i.e., fire intense longleaf pine woodlands versus fire suppressed mixed pine-hardwood and hardwood forests) and a riparian-upland habitat gradient, and at multiple spatial scales (i.e., the microhabitat and landscape). I used two-way factorial analyses to test for the effects of fire treatment and the riparian-upland habitat gradient on total bird abundance, species richness, and species relative abundance. To examine species-habitat associations at multiple spatial scales, I measured vegetation characteristics at a 50-m radius microhabitat scale, and I quantified landscape structural attributes at a 300-m to 1500-m radius landscape scale using a GIS database and the spatial analysis program FRAGSTATS. I then used logistic regression to determine which microhabitat and landscape variables were associated with the probability of occurrence for each species and which spatial scale was of greater relative importance to a species' occurrence. Finally, I tested logistic regression (LR) models and multiple linear regression (MLR) models, specific to the microhabitat scale, with independent data to evaluate their usefulness at predicting the occurrence and relative abundance for several breeding bird species. Total bird abundance did not vary across fire treatment and species richness may be only slightly greater in fire suppressed habitats, even though this habitat offered greater structural complexity than the park-like longleaf pine, fire intense habitats. Both total bird abundance and species richness were highest within the riparian habitat of streamhead pocosins, which offered distinctive vegetative characteristics otherwise lacking in this landscape. The fire treatment and riparian-upland habitat gradient also were greatly associated with the relative abundance of many species. Four bird species assemblages were defined based on the relative abundance patterns across fire treatments and the riparian-upland gradient: longleaf pine, fire suppressed, drain (i.e., riparian habitat), and generalist assemblages. Continued longleaf pine restoration using growing season prescribed fire likely will cause a decline in species of the fire suppressed assemblage in mixed pine-hardwood and hardwood forests, including many Neotropical migrant songbirds, but will greatly benefit members of the longleaf pine assemblage, such as the Red-cockaded Woodpecker, Brown-headed Nuthatch, Prairie Warbler, and Bachman's Sparrow. Breeding bird distributions in this fire-influenced, forest-dominated system were associated with attributes at both microhabitat and landscape spatial scales, though microhabitat attributes generally were of greater importance for the occurrence of most species. Microhabitat variation associated with the fire management gradient (intensely burned habitat versus fire suppressed habitat) and the riparian-upland gradient were the most frequent predictors in the species-habitat models. These results are similar to other studies documenting that microhabitat features were more influential than landscape features for birds in a naturally patchy or forest-dominated landscape. The microhabitat LR (probability of occurrence) models performed best in presence/absence classification when tested with the same data used for model development (cross-validation tests), and the LR and MLR (relative abundance) models performed better for an independent two-year data set compared to an independent one-year data set (validation tests). Although most MLR models were not significantly biased when tested with an independent two-year data set, these models had relatively low precision, suggesting they can be used to predict species relative abundance across a large area but they may not be sensitive to changes in abundance at individual count stations. These model validation results suggest that modeling species occurrence, rather than both occurrence and relative abundance, would have been sufficient to describe general species-habitat associations and to produce reliable, predictive models sensitive to changes in microhabitat structure and composition. / Master of Science

Understory light environments are inherently heterogeneous and therefore difficult to characterize. Numerous methods to measure understory light have been assessed in closed-canopied forests; however, the reliability of these methods has not been addressed for open-canopied forests. Therefore, the first objective of this study, presented in Chapter 3, was to test the accuracy and precision of various light measurement techniques at different time scales and sky conditions. The methods assessed performed differently depending on the sky condition and time of year when the sample was taken. To estimate annual photosynthetic photon flux density transmittance (annual %PPFD), the use of a 10-minute average of PPFD measured on an overcast day (%PPFDovercast) was effective, but accuracy decreased with decreasing solar altitude (ie season change). Hemispherical photographs used to estimate weighted canopy openness and gap fraction were effective methods, but gap light index (GLI) also derived from hemispherical photographs performed better. Accuracy of daily %PPFD estimates using %PPFDovercast, weighted canopy openness, and gap fraction were strongly affected by solar altitude and sky condition. Gap light index was very effective in estimating daily %PPFD for all sky conditions and time periods. The second objective of this study, presented in Chapter 4, was to characterize the relationship between canopy structure and spatial distribution of light by using three replicates of one uncut treatment and three harvest treatments: single tree, small gap (0.1 ha), and large gap (0.2 ha). Each harvest retained similar residual basal area but with different spatial patterns of the residuals, ranging from uniformly dispersed (single tree) to different degrees of aggregation (small and large gap). Average stand level light availability increased 12-22% when the same residual basal area of trees was distributed in clusters versus a uniform distribution. The variation of light availability increased as stands became more aggregated and larger amounts of the variation was explained by the spatial pattern of the canopy structure. Spatial autocorrelation range was twice as large in the small gap harvest then the other harvest treatments. It is suggested that seedling growth response to these differences in spatial patterns of light may differ between the different harvests. / Master of Science

No description available.

For some forest landowners in the southern USA, multiple ecological and economic objectives are met through the conversion of longleaf pine (Pinus palustris) plantations to uneven-aged stands. This study was conducted in eight similarly-aged longleaf pine plantations at The Jones Center at Ichauway in southwestern Georgia. The stands were disturbed by commercial thinning in 2014 and partially disturbed by Hurricane Michael in 2018 and half of the stands were seeded with native grasses and a forb in 2015. I developed explanatory models of groundcover biomass and longleaf pine seedling occurrence and density. I detected a community composition difference in groundcover species assemblages between seeded and unseeded stands. For recruited longleaf pine regeneration, my model indicated that lower amounts of groundcover biomass were correlated with greater occurrence and density of pine regeneration. Partial stand disturbances and restoration of native groundcover set stands on a trajectory to resemble a more natural condition.

The objective of this study is to determine whether changes in arthropod community structure in restored longleaf pine savannas corresponds to differences in vegetation structure often associated with burn frequency. Longleaf pine savannas are fire-maintained ecosystems characteristic of the southeastern United States and have experienced severe declines (around 97%) since European settlement. Changes in fire regime have been instrumental in the declines. Restoration of these ecosystems has involved reinstitution of periodic burnings to promote and maintain vegetative characteristics of the savannas. This study investigates trends in arthropod communities from areas heavily invaded by hardwood shrubs against those dominated by longleaf pines and associated vegetation. These data suggest that herb-dominated sites have higher overall diversity. While overall abundance differences were not found, significant differences have been detected at the order and family level, indicating that vegetation structure and periodic burning are important factors in maintaining arthropod communities characteristic of these savannas.

On 26 May 2003, intense rainfall from a series of thunderstorms in eastern North Carolina caused flooding that eventually destroyed the concrete dam in Hope Mills, draining Hope Mills Lake, and revealing a formerly submerged and buried structure that was identified as a timber crib dam. Inspection revealed these logs to be old-growth longleaf pines, which are now rare on the coastal plain landscape. Our primary objective was to develop a new multi-century longleaf pine tree-ring chronology by crossdating the tree rings from sections extracted from logs in the crib dam with an anchored tree-ring chronology created from nearby living longleaf pine trees. We also examined the climatic response in the longleaf pine trees to evaluate their potential for reconstructing climate. Using tree-ring measurements obtained from old-growth longleaf pines found at a nearby church, we were able to date the rings on 21 series representing 14 logs from the crib dam, spanning the years 1597 to 1825. Distorted sapwood in many of the logs prevented us from finding absolute cutting dates and lessened the strength of correlation during the period of overlap between the church series and crib dam series. Human disturbances, specifically related to the naval stores industry, likely influenced the growth-ring patterns of the crib dam pine samples, as well. Correlation analyses between the longleaf pine chronology and temperature, precipitation, Palmer Drought Severity Indices, and North Atlantic sea surface temperatures showed a significant response to cool and wet spring months.

No description available.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1968.