Graduate Theses & Dissertations

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Wetland Offsetting
Wetland loss in southern Ontario, escalated by development, is putting pressure on planners as they struggle to meet development needs while maintaining a balance with regional natural heritage. Wetland offsetting, coupled with strategic environmental assessment and sustainable community planning, offers a potential solution. A combined approach of literature review, interviews, focus group, and case study with Central Lake Ontario Conservation Authority (CLOCA) allowed me to present experiences and perspectives on wetland offsetting, site selection methods, and ecosystem service priorities. The focus group looked at organizational interactions and decision-making processes during wetland offsetting. Research resulted in creation of the Strategic Wetland Offset Site Selection Score Card (SWOSSS Card). Five of CLOCA’s past offsetting projects were reviewed to see what worked and what did not. Findings determined that use of strategic wetland offset site selection tools have the potential to provide an efficient means to quantify offsetting risk ahead of restoration efforts. Author Keywords: compensation, landuse planning, offsetting, prioritization, restoration, wetlands
Sensitivity of Forest Soils to Acidic Deposition Downwind of an Aluminum Smelter, Kitimat, B.C.
Maximum permitted SO2 emissions from an aluminum smelter in Kitimat, B.C., increased after modernization in 2015. An increase in acidic deposition can potentially acidify forest soils. Monitoring was conducted at two long-term soil monitoring plots at near (7 km) and far (41 km) sites downwind from the smelter. Change in soil properties was assessed between 2015 and 2018: for the near plot, there was significant decrease in pH and exchange acidity; far plot soils exhibited significant decrease of base cations and exchange acidity in the 0–5 cm layer only. The average total SO42- deposition at near and far plots were estimated to be between 8.2–12.1 and 6.7–7.4 kg/ha/yr, respectively. It was concluded no soil acidification was detected. Observed changes were attributed to measured differences in organic matter, likely influenced by sampling difficulty and measurement process discrepancies. Estimated SO42- deposition levels pose no risk to soil base cation depletion. Author Keywords: acid forest soils, acidic deposition, aluminum smelter, exchangeable base cations, long-term monitoring, minimum detectable change
Assessing effects and fate of environmental contaminants in invasive, native, and endangered macrophytes
Macrophytes play an important role in aquatic ecosystems, and thus are integral to ecological risk assessments of environmental contaminants. In this dissertation, I address gaps in the assessments of contaminant fate and effects in macrophytes, with focus on glyphosate herbicide use for invasive plant control. First, I evaluated the suitability of Typha as future standard test species to represent emergent macrophytes in risk assessments. I concluded that Typha is ecologically relevant, straight-forward to grow, and its sensitivity can be assessed with various morphological and physiological endpoints. Second, I assessed effects from glyphosate (Roundup WeatherMAX® formulation) spray drift exposure on emergent non-target macrophytes. I performed toxicity tests with five taxa, Phragmites australis, Typha × glauca, Typha latifolia, Ammannia robusta, and Sida hermaphrodita, which in Canada collectively represent invasive, native, and endangered species. I found significant differences in glyphosate sensitivity among genera, and all species’ growth was adversely affected at concentrations as low as 0.1% (0.54 g/L), much below the currently used rate (5%, 27 g/L). Third, I assessed the potential for glyphosate accumulation in and release from treated plant tissues. I found that P. australis and T. × glauca accumulate glyphosate following spray treatment, and that accumulated glyphosate can leach out of treated plant tissues upon their submergence in water. Finally, I assessed effects of released glyphosate on non-target macrophytes. I found that P. australis and T. × glauca leachate containing glyphosate residues can stimulate the germination and seedling growth of T. latifolia, but can exert an inhibiting effect on A. robusta, although leachate without glyphosate caused similar responses in both plants. Additionally, I found no negative effects in A. robusta when exposed to glyphosate residues in surface water, or when grown with rhizosphere contact to an invasive plant that was wicked (touched) with glyphosate. My results show that non-target macrophytes can be at risk from glyphosate spray for invasive plant control, but risks can be mitigated through informed ecosystem management activities, such as targeted wick-applications or removing plant litter. Integrating contaminant fate and effect assessments with emergent macrophytes into ecological risk assessments can support the protection of diverse macrophyte communities. Author Keywords: Ecosystem management, Ecotoxicology, Glyphosate, Herbicide, Invasive plant, Species at risk
Robust assessment of changes in wild mammal occupancy and activity relative to livestock and human disturbance
Anthropogenic activities such as human activity and livestock grazing are responsible for the global rise in disturbance impacts on wildlife and may underlie regional changes in biodiversity and ecosystem dynamics. Few studies have tried to disentangle the effects of different anthropogenic activities on wildlife behaviour, leaving a major gap in our understanding of conservation and management needs in disturbed areas. Human activity and livestock grazing are increasing in spread and intensity worldwide, thereby imposing pressure on both wildlife and natural areas. In this thesis, I used a camera trapping and occupancy modeling framework to assess whether human presence and livestock grazing had different impacts on site occupancy and activity of 10 wild mammal species, and how responses differed across taxa. Specifically, I predicted that all species would be sensitive to disturbance, but the type and intensity of the response would depend on disturbance type. I detected different responses to each disturbance type across species, but response type (displacement, activity change, crepuscularity) was not associated with species characteristics such as body. Importantly, disturbance intensity had a strong effect on wildlife activity levels, with many species exhibiting marked reductions in activity at high human or livestock disturbance intensity. It remains unclear whether all species’ responses are a direct consequence of disturbance versus indirect outcomes of shifts in behaviour of other species in the wildlife community (i.e., disturbance-related changes in prey activity may affect predator activity). Although on the whole disturbance intensity and effect sizes tended to be relatively low in this study, responses were exhibited across all species, implying that disturbance responses may be universal in wild mammals and largely underestimated. Ultimately, my work offers a template for the robust assessment of disturbance impacts on wildlife and provides new avenues for future research to deepen our understanding of wildlife sensitivity to anthropogenic activities. Author Keywords: activity, anthropogenic disturbance, human activity, livestock, occupancy, wildlife
Rethinking Subjectivity
The following thesis problematizes different theories of subject formation in relation to morality, accountability, and consciousness raising. Focusing on the conditions subjects emerge in, I argue that socially transformative subjectivities emerge in movement through spaces. The theoretical discussion departs from the premise that morally accountable subjectivities drive social change. The politics of positionality that anchor the subject in a particular social location conceptualize morality as the result of critical consciousness raising. The causal nature of the relationship between the subject’s ability to reflect back on itself and its moral capacity is problematic for it leaves the reflective subject in a position of epistemic and moral authority. Rather, a subject who does not fully know itself nor the conditions of its being has the ability to engage in moral inquiry. Grounding subject formation in epistemic uncertainty construes the subject as inherently accountable to other unknowing subjects. Transformative subjectivities emerge out of epistemic resistance and uncertainty. The particular understanding of morality that underlies the rethinking of my moral subject emanates from its relational constitution. A morality of care prioritizes the responsibilities a subject has to others. In the context of Covid-19, relational subjects act in accordance with a morality of care that leads them to intervene in the lives of others who are threatened by the virus and left unprotected by institutional structures. The desire to interfere is cultivated when subjects emerge in ontological fields generated through epistemic intervention. One way to create such interventions is through counter-hegemonic cultural production such as works of art. Author Keywords:
Individual Differences in Human Tolerance for Wildlife and The Role of Nature Relatedness
Human-wildlife interactions are inevitable and lead to decisions about wildlife. The current research investigated what demographic and psychological factors influence decisions in wildlife management. Also, a new measure, the Tolerance for Wildlife Scale, was developed. A student sample (n = 329) and a community sample (n = 213) completed measures on their nature relatedness, environmental concern, and emotions towards wildlife. They completed the Tolerance for Wildlife Scale and rated decisions to use lethal or non-lethal action in nine human-wildlife scenarios. Correlation analyses revealed people who are more tolerant towards wildlife are more connected with nature, concerned for the environment, feel positive emotions towards wildlife, and are more likely to choose non-lethal management actions. ANOVAs revealed that location and occupation have an impact on tolerance for wildlife. By identifying factors that influence tolerance for wildlife, humans can hope to share space with wildlife and foster coexistence. Author Keywords: emotion, environmental concern, nature relatedness, tolerance, wildlife, wolves
Evidence of an Interaction Between Memory Stores for Long-Term Context Fear Memory in the Rat
Memories which typically require the hippocampus (HPC) can become represented in structures outside of the HPC, and therefore resistant to HPC damage, but, the properties of these memories are poorly understood. Some research has suggested that the HPC continually contributes to memories that are resistant to hippocampal damage, and without this support, they are weaker and more susceptible to loss. However, this hypothesis has yet to be tested experimentally. We examined this possibility in rats by assessing decay and extinction of a context fear memory that had become independent of the HPC via repeated learning episodes. We found that HPC-independent context fear memories decay and extinguish faster without continued HPC support, suggesting that the HPC plays a continued role in long-term memory. We also provide new evidence of a persistent interaction between the HPC and other memory systems, which strengthens non-HPC representations so that they withstand HPC damage at longer intervals. Author Keywords: consolidation, context fear, hippocampus, memory, retrograde amnesia
Desire to be Zine
This thesis explores access to feminist zine culture and community, specifically if, and how, access has been altered in the age of digital technologies and increased access to digital spaces. Results from a questionnaire completed by 8 young feminist zine-makers and readers of marginalized genders indicated that though the modern boundaries of what a zine is has been expanded to include e-zines, there remains a preference toward print zines in zine-making and reading practices. Results also revealed that while there is a preference toward accessing feminist zine culture and community in-person in theory, participants were more likely to access feminist zine culture and community online in reality. This project found that digital technologies and the Internet have affected feminist zine culture in multiple ways, ranging from the Internet creating a new access points to community, to the Internet making it easier to find, purchase, and distribute zines. Author Keywords: Digital Media, Feminism, Feminist Zine Culture, Feminist Zines, Materiality, Print Media
Peers, Props & Play
This study examined the relation between complexity of pretend play during preschool and early academic skills two years later. Preschool children (n =19), aged 3 years, were observed during self-directed free play, which was then coded for complexity of symbolic thought with respect to symbolic agent (ability to direct self or other’s play) and symbolic substitution (abstractness of props). Children’s literacy and numeracy skills were assessed concurrently and two years later when children were 5 years old. We found that children who directed others' play compared to children who focused on their own play had higher mathematics achievement at 5 years. In addition, children who engaged in more complex object substitutions (abstract props) had better counting at 3 years and better early reading skills at 5 years than their peers, who showed few complex substitutions. Our findings suggest that encouraging specific aspects of pretend play in preschool could be a relatively simple way to promote early academic achievement. Author Keywords: Math , Play complexity, Preschool , Pretend Play, Reading
Phytohormone-enhanced heavy metal responses in Euglena gracilis
Phytohormones, Cytokinin (CK) and Abscisic acid (ABA), are best known for controlling plant growth and stress responses; but they also mediate various developmental perspectives in alga. Yet, their mode of action in algal adaptive strategies to heavy metal responses, their involvement in orchestration of phytohormone crosstalk remain largely unknown and a molecular framework of phytohormone-controlled heavy metal uptake is absent. I found that three metals known globally to contaminate aquatic ecosystems, nickel (Ni), lead (Pb), and cadmium (Cd), cause changes in the levels of endogenous CKs, ABA, auxins, and gibberellins (GAs) in the green alga Euglena gracilis. Exogenous ABA or CK (trans-zeatin) alleviated metal toxicity through improved metal uptake efficiency and the regulation of the endogenous CKs activity profiles and GAs activity. This new evidence suggests that E. gracilis possesses functional phytohormone signals and metabolic pathways that are under metal stress response. Exogenously applied ABA or CK provoked the coordinated activation of metal uptake, likely via enhanced accumulation of metal binding compounds (i.e., proline, glycine, cysteine containing peptides), which are effective for metal sequestration. Using untargeted metabolomics analysis and functional annotation, this thesis further established that, CK and ABA modified pathways and metabolites, which were mainly involved in metal acclimation and resistance. These modified metabolites that were under the influence of phytohormones in algal cells growing under metal stress conditions were associated with: lipid pathways, riboflavin metabolism, biosynthesis of cofactors/vitamin, and carbohydrate metabolism. Bioactive secondary compounds (e.g., terpenoids, alkaloids, flavonoids, carotenoids) were also modified in algal cells treated with phytohormones. The present study highlights that ABA and CKs are important regulators of algal metal accumulation/acclimation strategies based on increased metal uptake, enhanced CK metabolism, regulation of hormonal crosstalk and regulation of some core cellular metabolism pathways, all of which improve metal uptake efficiency. Finally, our results suggest that ABA and CK form a novel strategy for metal bioremediation techniques and for sourcing microalgal value-added metabolites. Author Keywords: abscisic acid, cadmium, cytokinin, Euglena gracilis, lead, nickel
Landscape fitness
Variation in habitat quality and disturbance levels can strongly influence a species’ distribution, leading to spatial variation in population density and influencing population dynamics. It is therefore critical to understand how density can lead to variability in demographic responses for effective conservation and recovery of species. My dissertation illustrates how density and spatial familial networks can be integrated together to gain a better understanding of the influence of density on population dynamics of boreal caribou. First, I created an analytical framework to assess results from empirical studies to inform spatially-explicit capture-recapture sampling design, using both simulated and empirical data from noninvasive genetic sampling of several boreal caribou populations in Alberta, Canada, which varied in range size and estimated population density. Analysis of the empirical data indicated that reduced sampling intensity had a greater impact on density estimates in smaller ranges, and the best sampling designs did not differ with estimated population density but differed between large and small population ranges. Secondly, I used parent-offspring relationships to construct familial networks of boreal caribou in Saskatchewan, Canada to inform recovery efforts. Using network measures, I assessed the contribution of individual caribou to the population with several centrality measures and then determined which measures were best suited to inform on the population demographic structure. I found substantial differences in the centrality of individuals in different local areas, highlighting the importance of analyzing familial networks at different spatial scales. The network revealed that boreal caribou in Saskatchewan form a complex, interconnected familial network. These results identified individuals presenting different fitness levels, short- and long-distance dispersing ability across the range, and can be used in support of population monitoring and recovery efforts. Finally, I used a spatial capture-recapture analytical framework with covariates to estimate spatial density of boreal woodland caribou across the Saskatchewan Boreal Plains, and then reconstructed parent-offspring relationships to create a familial network of caribou and determined whether spatial density influenced sex-specific network centrality, dispersal distance, individual reproductive success, and the pregnancy status of females. I show that caribou densitygreatly varied across the landscape and was primarily affected by landscape composition and fragmentation, and density had sex-specific influences on dispersal distance, reproductive success, and network centrality. The high density areas reflected good-quality caribou habitat, and the decreased dispersal rates and female reproductive output suggest that these remnant patches of habitat may be influencing demographic responses of caribou. Author Keywords: boreal caribou, density, familial networks, population dynamics, rangifer tarandus caribou, spatial capture-recapture
Using genomic and phenotypic data to explore the evolution and ecology of the North American mountain goat
Evaluating the impact of climate change is arguably one of the main goals of conservation biology, which can be addressed in part by studying the demographic history of species in the region of interest. In North America, landscape and species composition during the most recent Pleistocene epoch was primarily influenced by glaciation cycles. Glacial advance and retreat caused species ranges to shift as well, leaving signatures of past population bottlenecks in the genetic code of most species. Genomic tools have shown to be important tools for understanding these demographic events to enhance conservation biology measures in several species. In my thesis I first reviewed the state of ungulate genomics, with a focus on how such data sets can be used in understand demography, adaptation, and inform conservation and management. Importantly, the review introduces key analyses like the pairwise sequentially Markovian coalescent and features like variation in antlers and horns and selection pressures that are used throughout subsequent chapters. Using the North American mountain goat as a model species, I then explored the genomic and phenotypic variation in this alpine specialist mammal. Starting with the generation of the first genome assembly for the mountain goat, I identified genes unique to the mountain goat and modeled demographic history going back millions of years using a pairwise sequentially Markovian coalescent approach. Species’ effective population size generally paralleled climatic trends over the past one hundred thousand years and severely declined to under a thousand individuals during the last glacial maximum. Given the biological importance of horns in mountain goats and the recent scientific interest in genetic basis of headgear, I analyzed over 23,000 horn records from goats harvested in British Columbia, Alaska and Northwest Territories from 1980 to 2017. Overall, variation in horn size over space and time was low; goats harvested further North had shorter horn lengths and smaller horn circumferences in one year old and 4 years and older age classes and 4 years and older age class, respectively. Proximity of roads, which was used as an indicator of artificial selection, had a small effect on horn size, with larger horns being harvested closer to major roads. Finally, I used two range-wide genomic data sets sequenced with a whole genome re-sequencing and reduced representation approaches to provide estimates of genetic diversity, contemporary effective population sizes and population structure. These insights can help inform management and will potentially make an impact in preserving the mountain goat. Author Keywords: genome assembly, horn size, Oreamnos americanus, population demography, reduced representation sequencing, whole genome resequencing

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Graduate student theses produced at Trent University. You may also browse theses and dissertations by year, program, or author.

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