Physical Sciences and Mathematics Commons^™

Past Fire Regimes Of Table Mountain Pine (Pinus Pungens L.) Stands In The Central Appalachian Mountains, Virginia, U.S.A., Georgina Deweese

Doctoral Dissertations

Table Mountain pine is an Appalachian endemic that occurs in a patchy distribution from Georgia to Pennsylvania and is prolific at sites with a history of fire disturbance. The purpose of this dissertation was to reconstruct the fire regimes of Table Mountain pine stands in the Jefferson National Forest, Virginia. Sections from firescarred Table Mountain pines were collected at four sites to analyze fire history, while increment cores and stand composition information were collected from macroplots within each fire history site to investigate the possible influence of fires that were more ecologically severe. Results show that fire was frequent before …

A Multi-Scale Analysis Of Disturbance Dynamics In Hardwood Forest Communities On The Cumberland Plateau, U.S.A., Justin L. Hart

Doctoral Dissertations

The purpose of this research was to quantify forest disturbance processes and evaluate the influence of these processes on secondary hardwood forest communities on a section of the Cumberland Plateau in Tennessee. The specific objectives of this study were to: (1) reconstruct the disturbance history of a secondary hardwood forest using species composition, stand structure, tree-ring data, and soil charcoal analyses, (2) quantify canopy gap formation mechanisms, (3) document canopy gap characteristics, and (4) determine the forest response to small-scale disturbance events. This information is useful to understand the importance of localized disturbances on stand development and forest successional patterns. …

Mapping The Martian Geologic Record: Studies Of The Gusev Crater Spirit Landing Site And Plagioclase Feldspar Compositions On Mars, Keith Alan Milam

Doctoral Dissertations

The flurry of activity involved in the scientific study of Mars has resulted in multiple new data sets from several missions (Mars Global Surveyor (MGS), Mars Odyssey (MO), Mars Exploration Rovers (MER), Mars Reconnaissance Orbiter (MRO), and Mars Express) that provide information for unlocking the planet’s geologic and climatic history.

This three part study utilized both orbital data and laboratory experiments to examine Mars for morphologic and mineralogic evidence of aqueous activity and magmatic evolution.

The first study examined Gusev Crater, landing site for the Spirit MER rover. This work began during final landing site selection and was published just …

Remote Sensing Of Impact Crater-Exposed Subsurface Lithologies And Martian Rayed Crater Systems, Livio Leonardo Tornabene

Doctoral Dissertations

Impact cratering is ubiquitous, energetic and fundamental geologic process acting on the solid planetary bodies. As a consequence, craters provide planetary scientists with useful information regarding the surface and subsurface properties of planetary bodies. Specific mineral and lithologic compositions can be ascertained via craters in two ways: 1) by the remote sensing of crater-exposed subsurface materials, or 2) by studying the differentiated meteorites (e.g., lunar, Martian, etc.) ejected from their surfaces by highenergy impacts under specific conditions. As a proof of concept for subsurface-crater mapping, remote sensing techniques were applied to a terrestrial impact structure. Visible-near infrared (VNIR), short-wavelength infrared …

Beauveria Bassiana, A Cotton Endophyte With Biocontrol Activity Against Seedling Disease, Mary Ruth Griffin

Doctoral Dissertations

Beauveria bassiana isolate 11-98 is entomopathogenic, endophytic in tomato, and has biocontrol activity against Rhizoctonia solani on tomato. The objectives of this study were to determine 1) if B. bassiana is endophytic in cotton, following seed treatment; 2) if B. bassiana can protect cotton against seedling pathogens; 3) if different conidial rates, applied to seed, alter effectiveness of B. bassiana; and 4) mechanisms of biocontrol used by B. bassiana against plant pathogens. Cotton ‘Delta Pine 436’ seed was inoculated with isolate 11-98 conidia, sown in a gnotobiotic system, and then isolated from surfacesterilized seedlings on selective medium. Using scanning …

Ecological Indicator Development, Integration And Knowledge Mapping, Aaron Dean Peacock

Doctoral Dissertations

The overall goals of this project were: (1) to develop a microbiological ecological indicator that would describe military land disturbance, (2) integrate previously collected ecological indicator data from five separate research teams, and (3) produce knowledge maps with the resulting information that illustrates how the selected indicators are involved in ecosystem processes. To address goal one, soil samples were obtained from four levels of military traffic (reference, light, moderate, and heavy) with an additional set of samples taken from previously damaged areas. Using the soil microbial biomass and community composition as ecological indicators, reproducible changes showed increasing traffic disturbance decreases …