<p>GRAY, JANET BRACEY. Rare vascular flora of the longleaf pine-wiregrass ecosystem: temporal responses to fire frequency and population size. (Under the direction of Dr. Thomas R. Wentworth) We examined factors likely to be important in the management of rare flora occurring in the longleaf pine-wiregrass ecosystem on Fort Bragg and Camp Mackall Military Reservations in North Carolina. Thirty-six rare plant species, comprising 1,268 records, were documented during the course of two inventories of rare flora conducted during the periods 1991-93 and 1998-99. There were 891 (70.3%) records of persistence, 258 (20.3%) records of extinction, and 119 (9.4%) records of colonization; extinctions exceeded colonizations by 139 records. We used analyses of contingency table frequencies and logistic regressions to test hypotheses about temporal responses of local populations of rare flora. We found statistically significant effects of fire frequency on the colonization and extinction of rare flora; extinctions declined and colonizations increased with increasing fire frequency. There were statistically significant effects of both area occupied and stem number on the persistence and extinction of rare flora; extinctions declined and persistences increased with increasing area occupied and stem number. Relative turnover of rare flora was correlated with mean fire frequency and mean stem number. Relative turnover increased with increasing fire frequency and declined with increasing population size. Our analyses indicate the importance of fire and population size for the conservation of rare flora in this landscape. <P>

<p>Lysimachia asperulifolia, commonly known as Rough Leaved Loosestrife, is a federally endangered, rhizomatous herb restricted to ecotones between long-leaf pine savannas and pocosins in North and South Carolina. Botanists and land use managers across the species' range have observed low rates of seed production in natural populations. Low seed production may prevent establishment of new populations and production of new genotypes, thus limiting the ability of the species to survive diseases and changing environmental conditions. I conducted a study to determine causal mechanisms of the limited seed production at five natural populations in North Carolina. Using field observations and experiments, I examined pollen fertility, pollen compatibility, pollinator limitation, and population structure of L. asperulifolia. In this paper, I present background information on natural causes of low seed production, previously published information about L. asperulifolia species biology, and results of my own experiments.<P>

<p>This study examines the distribution of plant communities across the Southern Appalachian region and seeks to understand the role that soil fertility plays in the complex pattern of vegetation that exists in this landscape. A regional dataset consisting of 1,273 sample plots was used to explore patterns of species composition. A total of 6 vegetation classes and 19 plant communities were classified from this dataset. The correlation of environmental variables with Nonmetric Multidimensional Scaling (NMDS) ordinations indicated three major environmental gradients, elevation (a surrogate for temperature ), topographic landform (a surrogate for moisture), and soil fertility (base cations). The regional dataset was subset to mesophytic plant communities (Acidic Cove Forests, Rich Cove Forests, and Mesic Montane Oak-Hickory Forests) that represent narrow segments of the elevation and topographic landform gradients. Variables associated with soil fertility were highly correlated with the NMDS ordination of this reduced dataset. Finally, Acidic Cove Forests and Rich Cove Forests were examined separately. Soil fertility variables continued to be important correlates with patterns of species composition within Acidic Cove Forests. The Rich Cove Forests also exhibited a strong relationship between soil fertility and species composition. In addition, much of the compositional variation in Rich Cove Forests appears to have a geographic component. Future efforts to understand the causal factors of species distribution in this region should consider soil fertility.<P>

Thesis (Ph. D.)--Oregon State University, 1972. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Bioluminescence resonance energy transfer (BRET) is a biological phenomenon in some marine organisms such as Renilla reniformis and Aequorea victoria. In BRET, resonance energy from decarboxylation of coelenterazine, a substrate of Renilla luciferase (RLUC), is transferred to its acceptor such as green fluorescent protein (GFP) or yellow fluorescent protein (YFP), dependent on a distance of around 5 nm between the energy donor (RLUC) and its acceptor. The activation of the energy acceptor results in a spectral change in luminescence emission. The BRET system allows investigation of in vivo protein-protein interactions in real time. This was demonstrated with two heterodimeric interactions in transgenic Arabidopsis. In an attempt to optimize the activity and to address the reaction mechanism of the RLUC enzyme, a homology model of RLUC was obtained using a haloalkane dehalogenase, LinB, as a template. Furthermore, the homology model and the crystal structures of RLUC were docked with coelenterazine. The computational analyses suggested potential roles of catalytic triad residues (Asp120, Glu144, and His285) and substrate binding residues (N53, W121, and P220) in the active site. Mutagenesis, spectroscopy, and expression in E. coli were carried out to elucidate the reaction mechanism of RLUC and the possible roles of the residues. Moreover, the catalytic triad was probed using pharmacological tests. Using random mutagenesis, a new triple mutant was isolated, which showed increased kcat, increased half-life, and higher resistance to substrate inhibition. These results establish enzymatic characteristics of RLUC and, furthermore, suggest that the triple mutant may result in potentially advantageous properties for BRET assays, including imaging routines in Arabidopsis.

INTRODUCTION In this study, the forest composition of Wilson Mountain, Morgan County, Tennessee, is described and distribution of tree taxa and site factors are related. The study arose from the need for geographic knowledge of an area where resource understanding is of great national concern, and to provide data for characterization of local forest and soil resources as an aid in their management. Of further interest is characterization of the genetic and ecological amplitude of forest tree taxa in this area close to the center of Deciduous Forest diversity. The objectives in this study of the vegetation of Wilson Mountain were: (a) to describe the pattern of tree communities, (b) to analyze the variation in environmental factors which may be responsible for the distribution of tree taxa, (c) to evaluate the degree of correlation between environmental factors and vegetational pattern, (d) to determine if variation in characteristics of overstory and understory tree taxa was related to soil characteristics, slope direction and (or) topography. Tree vegetation occupying approximately 830 acres of Wilson Mountain was sampled during the summer months of 1965.

Thesis (M.S.)--Ohio State University, 1973. / Includes bibliographical references (leaves 58-59). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--Universität Zürich, 1905. / Reprint. Originally issued in series: Vierteljahrsschrift der Naturforschende Gesellschaft in Zürich ; Jahrg. 50. 1905. Includes bibliographical references (p. 158-166).

Thesis (M.S.)--Oregon State University, 1972. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

This thesis deals with physical factors and biological interactions affecting the distribution of two fucoid species, Fucus vesiculosus and F. serratus, in the Baltic Sea. Studies have been carried out in two quite different environments: an archipelago, and an open rocky coast. The archipelago has an extremely long coastline with a heterogeneous submerged landscape of different substrate types, slopes, water qualities, and degrees of wave exposure. The factors influencing F. vesiculosus distribution, morphology and epiphyte composition were studied in the Stockholm archipelago using field surveys and spatial modelling in Geographic information systems (GIS). A GIS-method to estimate wave exposure was developed and validated by comparing the result to an index based on vertical zonation of lichens. Wave exposure was considered an important factor for predicting the distribution of F. vesiculosus by its ability to clean hard surfaces from silt, and a predictive model was constructed based on the information of wave exposure and slope of the shore. It is suggested that the lower distribution boundary of attached F. vesiculosus is set by sediment in sheltered parts of the archipelago, and by light availability in highly wave exposed parts. The morphology of F. vesiculosus was studied over a wave exposure gradient, and several characters responded in accordance with earlier studies. However, when separating effects of wave exposure from effects of other confounding water property parameters, only thallus width was significantly different. Several water property parameters were shown to be correlated with wave exposure in the Stockholm archipelago, and the mechanism responsible for the effects on F. vesiculosus morphology is discussed. The composition of epiphytes on F. vesiculosus varied over a wave exposure gradient with a positive correlation to Elachista fucicola, and a negative to Chorda filum. At an open coast the physical environment is much less heterogeneous compared to an archipelago. The distributions of F. vesiculosus, F. serratus, turf-forming algae, and the seafloor substrate, were surveyed along the open coasts of Öland and Gotland. Turf-forming algae dominated all hard substrates in the area, and Polysiphonia fucoides was most abundant. At the Gotland coast F. vesiculosus was less abundant than at the Öland coast, and F. serratus occurred only in the southern-most part. Fucus serratus was increasingly more common towards south which was interpreted as an effect mainly of the Baltic salinity gradient, or the variation of salinity that has occurred in the past. The effects of turf-forming algae and sediment on F. serratus recruitment at 7 m depth off the Öland east coast were studied in the field, and by laboratory experiments. Almost no recruits were found in the algal turf outside the F. serratus patches. More fine sediment was found in the turf than in the F. serratus patches, suggesting that the turf accumulates sediment by decreasing resuspension. Both filamentous algae and sediment decreased the attachment ability of F. serratus zygotes and survival of recruits, and sediment had the strongest effect. It is therefore suggested that F. serratus has difficulties recruiting outside its patches, and that these difficulties are enforced by the eutrophication of the Baltic Sea, which has favoured growth of filamentous algae and increased sedimentation. An overall conclusion is that Fucus distribution is affected by large-scale-factors, such as the eutrophication and salinity changes of the Baltic Sea, as well as by small-scale variation in wave exposure, substrate and slope, and by surface competition with neighbouring species.