Species-species and species-habitat interactions have been demonstrated to be important in influencing diversity across a variety of ecosystems. Despite generalities in the importance of these interactions, appropriate mechanisms to explain them are absent in many systems. In sandhill systems of the southeast U.S., gopher tortoises have been hypothesized to be a crucial species in the maintenance of diversity and function. However, the mechanisms and magnitude in which they influence their communities and habitats have rarely been empirically quantified. I examined how habitat structure influences tortoise abandonment of burrows and how tortoise densities influence nonvolant vertebrate community diversity. Tortoise burrow abandonment is directly influenced by canopy closure, with each percent increase in canopy cover relating to a ~2% increase in the probability of burrow abandonment. In addition, tortoise burrow density was positively correlated with diversity and evenness, but not species richness. This influence was directly proportional to burrow density, supporting a dominance role for this species and rejecting the commonly asserted keystone species mechanism. I also quantified the influence of tortoises in influencing diversity relative to other environmental and habitat variables. Through this research, I have demonstrated that disturbance and habitat structure are important, but diversity responds most to density of burrows in the habitat. These findings demonstrate the intricate relationships interacting to maintaining diversity in sandhill systems. In particular, habitat change leading to declines of gopher tortoises may have drastic negative impacts on vertebrate species diversity.

A nationwide mail survey was conducted among importers and other members of the supply chain linked to the importation of tropical hardwood products to assess the market potential for Bolivian lesser-known wood species (LKS) in the U.S. market. One hundred and eleven companies responded to the questionnaire and provided information on their interest in importing lesser-known wood species, their willingness to pay for a Bolivian wood species substitute, percentage of their imports that are environmentally certified, and important factors considered to try new wood species. The results indicate that tropical hardwoods represent 33% of the product mix of companies that purchased wood products. Typically, companies imported less than 100 MBF in 2006. Sawnwood was the product that was imported the most, followed by plywood, veneer and flooring. Six Bolivian LKS are among the top 16 new wood species purchased by respondent companies in 2006 and three Bolivian LKS are part of the top 12 common tropical wood species imported in the U.S. Sixty-seven percent of overall respondents stated that they have plans to increase the imports of tropical hardwoods in 2007. Typically, members of the supply chain tried 1 to 2 new wood species in 2006. Retailers were the sector that tried the most, on average 5 new species. Price and availability were the major reasons to try new wood species. A MS-Access database was developed that allows comparisons of 20 potentially marketable Bolivian LKS with 10 common U.S. domestic hardwoods and 20 common tropical hardwoods imported into the U.S. Finally, strategic marketing recommendations are suggested to promote Bolivian LKS in the U.S. Results indicate that there are good opportunities for Bolivian LKS in the U.S market. / Master of Science

Invasions by alien understory plant species have gradually become a worldwide challenge in maintaining forest biodiversity and ecosystem productivity. Notably, Microstegium vimineum, a C4 grass native to Japan, has increased dominance in mixed deciduous hardwood forests of the southeastern United States, largely due to its shade tolerance and ability to spread through rhizomes. Microstegium vimineum also proliferates after prescribed fire, a common management tool used in the region to restore forests to desired conditions, and may compete with hardwood seedlings, hindering restoration efforts. Using two upland deciduous hardwood forest research sites in Marshall and Tate Counties, Mississippi, this study measured competitive effects of Microstegium vimineum on native hardwood seedling growth and survival with and without prescribed fire treatments. A single burning had no significant effect on Microstegium vimineum abundance, while the effect of Microstegium vimineum on seedling growth and survival varied by species.

<p> Age-Related Resistance (ARR) has been observed in numerous plant species, resulting in increased disease resistance as the plant matures. The ARR defective mutant, iap1-1, (important in the ARR Pathway,) was discovered in an ARR mutant screen and EDS1, (enhanced disease susceptibility,) which is involved in other disease resistance pathways, was shown to be required for ARR. lntercellular accumulation of salicylic acid (SA) is required for ARR suggesting that SA may act as an anti-microbial agent. Mature (6 wpg) iap1-1 does not accumulate intercellular or intracellular SA in response to Pst inoculation. lntercellular and intracellular SA accumulation is also partially reduced in young (4 wpg) plants during R gene-mediated resistance to Pst(AvrRpt2) which is partially compromised suggesting that the two pathways share common elements. The novel discovery of the presence of intercellular SA during R gene-mediated resistance suggests that it may act as an antimicrobial agent during R gene-mediated resistance as it is hypothesized to during ARR. The iap1-1 mutation maps to chromosome four between 17,938,268bp and 18,133,423b. The semi-dominant, loss of function nature of the iap1-1 mutation suggests that IAP1 is a positive regulator in the ARR pathway.</p> / Thesis / Doctor of Philosophy (PhD)

<p> An apparatus was designed and built to enable the study of volatilization reactions using a novel variant of thermogravimetry called thermoradiometry. The usefulness of the apparatus was demonstrated by investigating the volatilization of iron from solid samples with the fluorinated ligands 1,1,1-trifluoro-2,4-pentanedione and 1,1,1,5,5,5-hexafluoro-2,4-pentanedione.</p> / Thesis / Master of Science (MSc)

<p> The behaviour of iodic acid, of mixtures of iodic acid and iodine, and of various other iodine compounds as solutes in sulphuric and fluorosulphuric acids has been studied, using mainly cryoscopic and conductimetric techniques. Evidence has been obtained for the existence of polymeric species containing iodine (V), of the oxy-cation IO+, of the iodine cation, I+, in small concentrations in equilibrium with its disproportionation products, and of the cations I3+, I5+ and I2Cl+. The reaction of iodosyl sulphate with disulphuric acid has been studied. Conductimetric studies have been made of solutions of water, potassium nitrate and potassium perchlorate in fluorosulphuric acid. The results of some spectrophotometric and nuclear magnetic resonance experiments are also reported.</p> / Thesis / Doctor of Philosophy (PhD)

Stylaria is a genus of globally distributed clitellates consisting of two recognized species with a difficult taxonomic history: Stylaria lacustris and Stylaria fossularis. The current species-level taxonomy of this genus is unclear due to variation in several morphological characters. To assess the amount of species-level diversity in Stylaria, an integrative approach using morphological investigations and genetic information was employed. I investigated the phylogenetics of this genus using three loci, two mitochondrial (cox1, and rrnL), and one nuclear (ITS) gene regions. Using several species delimitation tools, I was able to estimate the number of species in this group. Automatic barcode gap discovery, assemble species by automatic partitioning (ASAP), and the Geneious Prime Species delimitation package all delimited at least five species within Stylaria, Bayesian Poisson Tree Processes(bPTP) recovered at least six, and DELINEATE proposed only three species, all within S. fossularis. Morphologically, there seems to be no clear, consistent distinction between members of S. lacustris from Europe and S. lacustris from North America. Based on my morphological investigations and disagreement among species delimitation methods, I conservatively propose that the subclades discovered via phylogenetic analysis of mitochondrial and nuclear sequence data within S. lacustris represent population-level rather than species-level variation. However, there appear to be at least two previously unknown species in need of proper descriptions within the S. fossularis species complex. Within Stylaria, morphological criteria might be useless at the species level as there is a high level of intraspecific morphological variation. Analyses of sexual characteristics of this group could help further document any differences between populations of S. lacustris.

Flowering rush (Butomus umbellatus L.) is a perennial wetland/aquatic plant that is native to Eurasia but has invaded North America and spread across Southern Canada and the Northern U.S. where it thrives along wetlands, shallow shorelines, and in submersed habitats of lakes, ponds, streams, rivers, and reservoirs. Little is known about the life cycle of flowering rush in its invaded range as only one study has investigated flowering rush phenology in Minnesota, USA. As flowering rush continues to expand its range southward in the U.S. it is imperative that resource managers 1) better understand the plants life cycle, 2) identify more aggressive and 3) selective herbicide strategies, and 4) utilize adaptive management protocols. In a mesocosm experiment, flowering rush grown in southern climates produced less overall biomass but produced more buds than recorded in northern populations. A second mesocosm study using one to four biweekly sequential diquat (0.37 mg L-1) treatments reduced flowering rush biomass and rhizome bud density by 62 to 100% one year after treatment. Additionally, there were no differences among diquat treatments suggesting that more aggressive diquat protocols may not be useful. In field trials, flowering rush was selectively reduced 92 to 99% by diquat treatments over two years, while hardstem bulrush was not affected. In mesocosms, flowering rush and hardstem bulrush were exposed to the contact herbicides diquat, endothall, copper, carfentrazone-ethyl, and flumioxazin; endothall (3.0 mg L-1) selectively reduced aboveground biomass of flowering rush by 69% and diquat (0.19 mg L-1) selectively reduced belowground biomass by 77%. None of the other herbicides affected flowering rush. In a Minnesota field project to identify adaptive control strategies, treatment sites were designated as having very-low, low, or high flowering rush prevalence with each receiving no, one, or two diquat treatments (0.37 mg L-1), respectively. Flowering rush did not increase after single diquat applications in low prevalence sites while prevalence declined in high prevalence sites. This suggests that single diquat applications are suitable to maintain control of sites with low flowering rush prevalence allowing resource managers to allocate unused resources elsewhere.

No description available.

No description available.