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Examining how ecological processes are influenced by spatial variation can provide valuable insights into how communities are formed and how they may change in dynamic landscapes. In this thesis I address three objectives surrounding the spatial and temporal variation in species’ recruitment and predation, the influence of habitat isolation on consumer-resource relationships, and the influence of habitat fragmentation on a multi-trophic system. I used marine invertebrates, specifically crustaceans, bivalves, and sessile species as a model system. First, I address the spatial and temporal variation in local and regional processes in a multispecies assemblage of marine sessile invertebrates. Using diverse communities of marine sessile invertebrates as a model system I tested the hypothesis that spatial and temporal variation in recruitment and predation would shape local communities, and that both recruitment and predation would have significant effects on the abundance and structure of adult communities. I found that both recruitment and predation vary through time and space leading to the emergence of regional community divergence. I also address how habitat isolation interacts with top-down and bottom-up processes in seagrass ecosystems. Spatial structure of the habitat may mediate top-down and bottom-up controls of species abundances through decreased habitat connectivity and increased habitat isolation. I manipulated top down and bottom up processes by excluding mesograzers, adding resources, or altering both factors in isolated and contiguous patches of artificial seagrass. I then measured epiphyte recruitment, epiphyte abundances, and macroalgae abundance. I paired this with epiphyte sampling from isolated natural seagrass patches. I found that habitat isolation significantly decreased the abundance of epiphytes settling on seagrass blades due to dispersal limitation for epiphytic invertebrates. I found that consumers had strong effects on epiphyte biomass in continuous habitats, but not isolated habitats. Resource additions increased macroalgae cover and epiphyte biomass only in isolated habitats. The results suggest that isolated habitats may be nutrient limited and that top-down effects are stronger in continuous habitats, while bottom-up effects may dominate in isolated habitats. In my third objective, I address how habitat fragmentation may alter marine food webs. I examined whether predation rates, prey, and predator behavior differed between continuous and fragmented seagrass habitat in a multi-trophic context at two sites in Barnegat Bay, NJ. I hypothesized that blue crab predation rates and foraging would decrease in fragmented seascapes, due to a reduction in adult blue crab densities, increasing survival rates of juvenile blue crabs and hard clams. I expected hard clams to exhibit weaker predator avoidance behavior in fragmented habitats because of decreased predation. I found that species’ responses to fragmentation were different based on trophic level. Clams experienced higher predation and burrowed deeper in continuous habitats at both sites. Densities of blue crabs, the primary predator of hard clams, were higher in continuous habitats at both sites. Predation on juvenile blue crabs was significantly higher in fragmented seagrass at one site. Our results suggest that in fragmented seascapes, the impact of fragmentation on higher trophic level predators may drive predation rates and prey responses across the seascape, which may lead to trophic cascades in fragmented habitats. / Biology

BACKGROUND: Current research regarding the impact aging has on characteristics of sleep suggest that over the course of one’s lifespan, the quantity and quality of sleep declines. Sleep quality is a measure of the extent to which sleep is consolidated- the less number of brief awakenings one experiences during a period of sleep, the better. The extent to which degradation of sleep quality may impact overall health and increase susceptibility to age-related diseases is currently unknown, nor is the mechanism that mediates sleep fragmentation and consolidation understood. OBJECTIVE: The purpose of this study was to ascertain if the increased sleep fragmentation experienced with age is due to a decreased arousal threshold towards external stimuli. A decreased ability to inhibit sensory processes during sleep could potentially trigger a greater number of brief awakenings and negatively impact sleep quality. METHODS: Various age groups of inbred wild-type genotypes of Drosophila melanogaster had arousal threshold tested during the night using mechanical stimuli to see if the older flies were more likely to be woken up. Sleep characteristics at baseline and after the arousal assay were compared to observe any impacts aging has on the ability to recover from a mild sleep deprivation as such. RESULTS: I observed an increase in arousal threshold with age; older flies were less likely to be aroused by the presentation of the mechanical stimulus. Arousal threshold findings were consistent between sexes but not between genotypes. It was noted that the degree to which aging impacted arousal threshold was affected by the expected lifespan of a genotype. In terms of sleep characteristics measured outside of the arousal assay, I noticed an increase in quantity of sleep and decrease in activity as flies aged, including a greater reliance on day sleep. This was further reflected by a decrease in rebound sleep after the arousal assay was performed. More specific sleep architecture characteristics such as bout number and bout length were greatly impacted by both sex and genotype. CONCLUSION: Our results were greatly unexpected in comparison to previous studies, especially in regards to older flies having an increased arousal threshold and an increased quantity of sleep. This is not conclusive, however, as previous studies have shown that the saliency of the stimulus presented may prove important, especially when considering the internal state of the fly. Instead of solely focusing on if older flies are more or less easy to wake up with the application of an external stimulus, it may instead be beneficial to also consider their ability to discriminate between salient stimuli while quiescent.

This research evaluated the extent to which forests in Virginia have either become fragmented (disconnected) and/or connected over a ten year time period. The study analyzed the accuracy of forest fragmentation analysis depending on the spatial resolution of the satellite imagery used. This analysis highlights the importance of using appropriate satellite images for forest fragmentation analysis. Secondly, this research focused on building a model to identify the significance of factors such as slope, physiographic region and forest types on Virginia's populations of Wood Thrush and Ovenbird. This assessment identified the difference in effects of variables on bird populations depending on the scale at which the analysis is carried out. Third and final analysis combined the first two assessments to determine how management policies can be used to mitigate negative effects of forest fragmentation and protect biodiversity. The research results highlight increasing forest fragmentation trends in Virginia between 2001 and 2011 and the negative impacts of this trend on Wood Thrush and Ovenbird species. The results also demonstrate the effectiveness of riparian buffers as corridors. / Doctor of Philosophy / This research evaluated the extent to which forests in Virginia have either become fragmented (disconnected) and/or connected over a ten year time period. The study analyzed the accuracy of forest fragmentation analysis depending on the spatial resolution of the satellite imagery used. This analysis highlights the importance of using appropriate satellite images for forest fragmentation analysis. Secondly, this research focused on building a model to identify the significance of factors such as slope, physiographic region and forest types on Virginia’s populations of Wood Thrush and Ovenbird. This assessment identified the difference in effects of variables on bird populations depending on the scale at which the analysis is carried out. Third and final analysis combined the first two assessments to determine how management policies can be used to mitigate negative effects of forest fragmentation and protect biodiversity. The research results highlight increasing forest fragmentation trends in Virginia between 2001 and 2011 and the negative impacts of this trend on Wood Thrush and Ovenbird species. The results also demonstrate the effectiveness of riparian buffers as corridors.

For the first time, triblock copolymers of novel styrenic-based macromolecules were investigated in detail and examined for structure-morphology-performance relationships. We were able to design novel imidazolium- and phosphonium-containing styrenic macromolecules using controlled radical polymerization and conventional free radical polymerization strategies, for a variety of potential applications including electromechanical devices, ionic liquids, adhesives, and lithium-ion batteries. Block copolymers have a unique architecture providing physical crosslinking to behave as thermoplastic elastomers. We preferred ABA triblock copolymers as compared to random and diblock copolymers for improved mechanical performance. ABA triblock copolymers synthesized using nitroxide-mediated polymerization (NMP) of polystyrene external blocks and a charged imidazolium-containing central block, exhibited sufficient modulus and ionic conductivity for electromechanical transducers. We successfully reported the actuation behavior of triblock copolymers in the presence of added ionic liquid for the first time. We proposed that diluting the ion concentration of the ion-rich phase with neutral polymer comonomers that reduces Tg, increases ion dissociation, and potentially maximizes ionic conductivity. Tendency of ethylene-oxide units to coordinate cations, forming stable crown ether-like, multi-nuclear coordination complexes, promotes solvation and dissociation of ionic aggregates. In situ Fourier transform infrared spectroscopy (FTIR) was used to monitor the thermal polymerization in various acrylate and methacrylate monomers. It was found that acrylates have lower activation energy than methacrylates. The copolymerizations of poly(ethylene glycol)methyl ether acrylate (EG9MEA) and imidazole-containing monomer (VBIm) resulted in controlled polymerization kinetics with narrow molecular weight distributions. The control behavior of the copolymerizations is likely attributed to the observed decrease in calculated apparent rate constants for the copolymerizations with addition of VBIm as comonomer. Reversible addition fragmentation transfer (RAFT) successfully synthesized well-defined A-BC-A triblock copolymers containing a synergy of pendant ether and imidazolium sites. We demonstrated that electromechanical transducers derived from these triblock copolymer membranes with added ionic liquid showed superior actuation performance compared to a benchmark Nafion® membrane, suggesting potential for ionic polymer device applications. This was attributed to optimum modulus, improved ionic conductivity, and microphase-separated morphology of triblock copolymers. Conventional free radical polymerization and anion metathesis of 4-(diphenylphosphino)styrene (DPPS) successfully generated high molecular weight triaryl phosphine-containing copolymers. These macromolecules have no -CH2 group at the benzylic position increasing the thermal stability of the DPPS-containing polymers. Counterion exchange to fluorinated, bulkier anions broadened the library of polyelectrolytes, led to improved thermal stabilities, lower glass transition temperatures, and tunable wetting behavior. We also reported the synthesis of salt-responsive copolymers using conventional free radical polymerization. Adhesive performance measurements such as peel tests and probe tack enforced the application of these polymers as pressure sensitive adhesives. We also demonstrated the synthesis and subsequent neutralization of novel, well-defined A-BC-A triblock copolymers containing a soft central 'BC' block consisting of Sty-Tf2N and DEGMEMA with polystyrene external blocks. Sty-Tf2N monomer enables an important delocalization of the negative charge. Li+ has weak interactions with this anionic structure, consequently enabling a high dissociation level. Li+ ions are associated to the polymer chain to produce high transport numbers. Furthermore, incorporating DEGMEMA lowers the Tg of the charged block copolymers, thereby increasing the segmental mobility and thus ionic conductivity. Finally, the structure-property-morphology study of these triblock copolymers will be helpful for their use in potential applications such as ion-containing membranes, lithium-ion batteries. / Ph. D.

The purpose of this study was to analyze landowner perceptions of an ecosystem management program proposed by The Nature Conservancy. This creation of this program, The Forest Bank, is an attempt to protect the unique ecological and biological resources of the Clinch River Valley of Southwest Virginia. This study analyzed the attitudes and characteristics of landowners that contribute to their decision to enroll in such a program. Data were collected by a 8-page mail questionnaire sent to 2000 landowners in a five-county area of Southwest Virginia. The final sample size resulting from this effort was 816 landowner surveys, representing an overall response rate of 45%. Two separate analyses were undertaken with respect to this data, each representing a unique and informative approach to landowners and The Forest Bank. The first analysis summarizes how landowners perceived the individual components of the program, their level of interest in enrollment, and what types of landowners would be most likely to express interest in such a program. Twenty-three percent of landowners expressed interest in enrolling in The Forest Bank at some time. In general, those interested in enrollment perceived the individual components of the program differently than those who were not interested in enrolling. Landowners who expressed enrollment interest were more likely to be younger, more affluent, more educated than those who did not express interest in enrollment. The second analysis employed a structural equation model in order to determine what attitudes and motivations influence attitudes toward an ecosystem management program such as The Forest Bank. Variables such as attitudes toward property rights, environmental attitudes, trust in sources of information, and level of community attachment were included in this model. Results indicate that while attitudes toward property rights and the environment were not as important as previous literature suggested, landowner reasons for owning land were key indicators in determining attitudes toward The Forest Bank. Results from this study provide valuable information to managers and researchers concerning landowner attitudes toward ecosystem management and their level of interest in enrolling in an ecosystem management program. This information will help managers better understand how landowners perceive individual components of these types of programs, as well as determining the types of landowners who would be interested in enrolling. These findings can then be used to tailor programs that are more consistent with landowner objectives, and to better understand the complex attitudes and characteristics of private forest / Master of Science

No / Trade data are often classified by product characteristics. We propose a new classification ¿sophistication¿ as a means of distinguishing between products. We construct a sophistication index based on the income levels of exporting economies. Sophistication captures a range of factors including technology, ease of product fragmentation, natural resource availability, and marketing. We calculate sophistication scores at the 3- and 4-digit levels and test how far the index relates to existing technological classifications of products. We use the index to examine trade patterns and illustrate how it can be applied in the analysis of export performance of individual economies.