Graduate Theses & Dissertations

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Practicing and Rewarding Task-Relevant Motor Variability to Optimize Motor Performance
It is universally accepted that human motor performance is variable in both its timing and spatial qualities. However, it is unclear to what extent motor variability impedes performance when learning a new skill and to what extent it enables our ability to learn. The first experiment examined whether performance during a test task depended on whether participants practiced to constrain or vary the task-relevant parameter. Participants used their right hand to make simple point-to-point movements. Results demonstrated the importance of paying attention to test task demands to evaluate which form of practice is most beneficial. The second experiment examined whether levels of variability could be manipulated using a reward-based paradigm to enhance learning when adapting to a perturbation of a simple visually-guided reaching movement. A reward-based feedback task was designed to encourage exploration along the task-relevant dimension, specifically movement direction variability. Overall, I did not find any significant results. Author Keywords: Adaptation, Motor Control, Motor Learning, Reaching
Representations of Aboriginal Health in the Media
The goal of the present study was to explore the overall discourse within media articles regarding Aboriginal health issues. The present research aimed to answer the following questions: What Aboriginal health issues are being discussed in the media? How are Aboriginal health issues being discussed in the media? And, does the media propagate power imbalances between Aboriginal and non-Aboriginal Canadians? A thematic analysis was conducted, coopting aspects of Critical Discourse Analysis (CDA) to assess media content. Four CDA devices were used: overlexicalisation, structural oppositions, nominalizations and functional nominations, and concessions and hedging. Results suggest that while there are disparities in health outcomes between Aboriginal and non-Aboriginal Canadians, it is not widely reported in the media. The thematic analysis of 208 articles revealed patterns of stereotypical ideologies and negative framing appearing in media articles, the creation of an us versus them narrative, and themes of out of sight, out of mind, criminalizing Aboriginal Canadians, politicizing health, and access to health services. Author Keywords: Aboriginal Health, Communication, Health, Media, Psychology, Thematic Analysis
Application of One-factor Models for Prices of Crops and Option Pricing Process
This thesis is intended to support dependent-on-crops farmers to hedge the price risks of their crops. Firstly, we applied one-factor model, which incorporated a deterministic function and a stochastic process, to predict the future prices of crops (soybean). A discrete form was employed for one-month-ahead prediction. For general prediction, de-trending and de-cyclicality were used to remove the deterministic function. Three candidate stochastic differential equations (SDEs) were chosen to simulate the stochastic process; they are mean-reverting Ornstein-Uhlenbeck (OU) process, OU process with zero mean, and Brownian motion with a drift. Least squares methods and maximum likelihood were used to estimate the parameters. Results indicated that one-factor model worked well for soybean prices. Meanwhile, we provided a two-factor model as an alternative model and it also performed well in this case. In the second main part, a zero-cost option package was introduced and we theoretically analyzed the process of hedging. In the last part, option premiums obtained based on one-factor model could be compared to those obtained from Black-Scholes model, thus we could see the differences and similarities which suggested that the deterministic function especially the cyclicality played an essential role for the soybean price, thus the one-factor model in this case was more suitable than Black-Scholes model for the underlying asset. Author Keywords: Brownian motion, Least Squares Method, Maximum Likelihood Method, One-factor Model, Option Pricing, Ornstein-Uhlenbeck Process
Effects of biodiversity and lake environment on the decomposition rates of aquatic macrophytes in the Kawartha Lakes, Ontario
Decomposition of aquatic macrophytes has an important role in defining lake carbon (C) storage and nutrient dynamics. To test how diversity impacts decomposition dynamics and site-quality effects, I first examined whether the decomposition rate of aquatic macrophytes varies with species richness. Generally, I found neutral effects of mixing, with initial stoichiometry of component species driving decomposition rates. Additionally, external lake conditions can also influence decomposition dynamics. Therefore, I assessed how the decomposition rate of a submersed macrophyte varies across a nutrient gradient in nine lakes. I found decomposition rates varied among lakes. Across all lakes, I found Myriophyllum decomposition rates and changes in stoichiometry to be related to both nutrients and water chemistry. During the incubation changes in detrital stoichiometry were related to lake P and decomposition rates. Aquatic plant community composition and stoichiometry could alter decomposition dynamics in moderately nutrient enriched lakes. Author Keywords: Aquatic Plants, Decomposition, Diversity, Littoral, Macrophytes, Nutrients
Acidification of lakes in northern Saskatchewan
The emission of acid precursors by large point sources in Western Canada (such as the Athabasca Oil Sands Region) has prompted studies into the possible impact to downwind aquatic and terrestrial ecosystems. Sensitivity of catchments to acidic deposition was estimated for the total lake population of northern Saskatchewan (n=89,947) using regression kriging. Under the Steady State Water Chemistry model, a range of 12-15% of the total catchment population was predicted to be in exceedance of critical loads under 2006 deposition levels and 6% of catchments were estimated to be very sensitive (pH below 6 and acid neutralizing capacity, alkalinity, calcium below 50 eqL-1). Temporal changes in soil and water chemistry estimated for 18 Alberta and Saskatchewan catchments using the Very Simple Dynamic and PROFILE models showed that changes in soil base saturation and lake acid neutralizing capacity between 1850 and 2100 were slight, declining 0.8% and 0.9% by 2012, respectively. Author Keywords: acidification, critical loads, exceedance, PROFILE, regression kriging, VSD
Effects of road salt sodium on soil
While previous studies have focused on how road salt affects water quality and vegetation, limited research has characterized road salt distribution through soil and the resulting impacts. The potential for sodium (Na+) to be retained and impact soil physical and chemical properties is likely to vary depending on the soil’s parent material, and more specifically on the extent of base saturation on the cation exchange complex. This thesis contrasted Na+ retention, impacts, and mobility in roadside soils in two different parent materials within southern Ontario. Soils were sampled (pits and deep cores) during fall 2013 and spring 2014 from two sites along highways within base-poor, Precambrian Shield soil and base-rich soil, respectively. Batch experiments were subsequently performed to investigate the influence of parent material and the effect of co-applied Ca2+-enriched grit on the longevity of Na+ retention in soils. Less Na+ is adsorbed upon the co-application of Ca2+, suggesting grit has a protective effect on soil by increasing cation exchange competition. Positive correlations between Na+ and pH, and negative correlations between Na+ and soil organic matter, % clay and base cations within Shield soils suggest that they are more vulnerable to Na+ impacts than calcareous soils due to less cation exchange competition. However, Na+ is more readily released from calcareous roadside soils, suggesting there is greater potential for Na+ transfer to waterways in regions dominated by calcareous soils. Author Keywords: cation exchange, parent material, road salt, sodium retention, urban soil
Regional differences in the whistles of Australasian humpback dolphins (genus Sousa)
Most delphinids produce narrowband frequency-modulated whistles with a high level of plasticity to communicate with conspecifics. It is important to understand geographic variation in whistles as signal variation in other taxa has provided insight into the dispersal capabilities, genetic divergence and isolation among groups, and adaptation to ecological conditions. I investigated whistle variation of Indo-Pacific humpback dolphins (Sousa chinensis chinensis), Taiwanese humpback dolphins (S. c. taiwanensis) and Australian humpback dolphins (S. sahulensis) to test whether differences in whistles support the hypotheses of population structure, regional and species differences in the genus Sousa, which were based on morphological and genetic data. I also investigated important factors that may contribute to local distinctiveness in whistles including behavioural state, group size, and the influence of vessel noise. Multivariate analyses of seven acoustic variables supported the hypotheses of population structure, regional and species differences. Acoustic diversification between groups is likely influenced by behaviour and social contexts of whistles, and environmental noise. The use of sound to identify discrete groups of humpback dolphins may be important in future studies where genetic and morphological studies may not reveal recent differentiation or are difficult to conduct. Author Keywords: Bioacoustics, Cetacean, Geographic variation, Population biology, Sousa, Whistle characteristics
Impact of Invasive Earthworms on Soil Respiration and Soil Carbon within Temperate Hardwood Forests
Improving current understanding of the factors that control soil carbon (C) dynamics in forest ecosystems remains an important topic of research as it plays an integral role in the fertility of forest soils and the global carbon cycle. Invasive earthworms have the potential to alter soil C dynamics, though mechanisms and effects remain poorly understood. To investigate potential effects of invasive earthworms on forest C the forest floor, mineral soil, fine root biomass, litterfall and litter decomposition rates and total soil respiration (TSR) over a full year were measured at two invaded and one uninvaded deciduous forest sites in southern Ontario. The uninvaded site was approximately 300m from one of the invaded sites and a distinct invasion front between the sites was present. Along the invasion front, the biomass of the forest floor was negatively correlated with earthworm abundance and biomass. There was no significant difference between litterfall, litter decomposition and TSR between the invaded and uninvaded sites, but fine root biomass was approximately 30% lower at the invaded site. There was no significant difference in soil C pools between the invaded and uninvaded sites. Despite profound impacts on forest floor soil C pools, earthworm invasion does not significantly increase TSR, most likely because increased heterotrophic respiration associated with earthworms is largely offset by a decrease in autotrophic respiration caused by lower fine root biomass. Author Keywords: Biological Invasions, Carbon, Earthworms, Forest Ecosystems, Forest Floor, Soil Respiration
An Assessment of Spatial Trends in the Accumulation of Oil Sands Related Metals in the Clearwater River Valley and Temporal Trends in Six Northern Saskatchewan Lakes
The objective of this thesis was to assess current spatial trends and historic trends in the accumulation of trace metals related to the Athabasca Oil Sands Region (AOSR). The AOSR hosts some of the largest industrial developments in Canada, yet relatively little is known about the transport and fate of trace metal emissions from the region – particularly in the relatively remote areas to the east of the AOSR. Lichens are widely used as biomonitors and are employed in this thesis to assess the range of metals deposition within the Clearwater River and Athabasca River Valleys. Lake sediment cores can retain a historical record of the long-range transport and deposition of metals but can also respond to large regional metal emissions sources. This thesis used lake sediment cores to assess temporal trends in metals accumulation in six road accessible lakes in NW Saskatchewan that are likely to be used by local residents. Results show that metal concentrations (V, Co, Cu, Ni, Pb, Zn, Zr and Cd ) in lichen decline exponentially with distance from the AOSR and approach background levels within a few kilometers . Results from lake sediment cores show that there was no evidence that metal concentrations had increased due to industrial activities in the AOSR. Author Keywords: Air Emissions, Lakes, Lichens, Oil Sands, Saskatchewan, Trace Metals
Adaptive Genetic Markers Reveal the Biological Significance and Evolutionary History of Woodland Caribou (Rangifer tarandus caribou) Ecotypes
Migratory and sedentary ecotypes are phenotypic distinctions of woodland caribou. I explored whether I could distinguish between these ecotypes in Manitoba and Ontario using genetic signatures of adaptive differentiation. I anticipated that signatures of selection would indicate genetic structure and permit ecotype assignment of individuals. Cytochrome-b, a functional portion of the mitochondrial genome, was tested for evidence of adaptation using Tajima’s D and by comparing variations in protein physiology. Woodland caribou ecotypes were compared for evidence of contemporary adaptive differentiation in relation to mitochondrial lineages. Trinucleotide repeats were also tested for differential selection between ecotypes and used to assign individuals to genetic clusters. Evidence of adaptive variation in the mitochondrial genome suggests woodland caribou ecotypes of Manitoba and Ontario corresponded with an abundance of functional variation. Woodland caribou ecotypes coincide with genetic clusters, and there is evidence of adaptive differentiation between migratory caribou and certain sedentary populations. Previous studies have not described adaptive variation in caribou using the methods applied in this study. Adaptive differences between caribou ecotypes suggest selection may contribute to the persistence of ecotypes and provides new genetic tools for population assessment. Author Keywords: Adaptation, Cytochrome-B, Ecotype, RANGIFER TARANDUS CARIBOU, Selection, TRINUCLEOTIDE REPEAT
Testing for Interspecific Hybridization and a Latitudinal Cline Within the Clock Gene Per1 of the Deer Mouse (Peromyscus maniculatus) and the White-Footed Mouse (Peromyscus leucopus)
The recent northward expansion of the white-footed mouse (Peromyscus leucopus) in response to climatic changes provides a natural experiment to explore potential adaptive genetic variation within the clock gene Per1 in Peromyscus undergoing latitudinal shifts, as well as, the possibility of hybridization and introgression related to novel secondary contact with its sister species the deer mouse (Peromyscus maniculatus). Because clock genes influence the timing of behaviors critical for survival, variations in genotype may reflect an organism’s ability to persist in different environments. Hybridization followed by introgression may increase the adaptive potential of a species by quickly generating adaptive variation through novel genetic recombination or by the transfer of species-specific alleles that have evolved in response to certain environments. In chapter 2, I used microsatellite and mtDNA markers to test for hybridization and introgression between P. maniculatus and P. leucopus and found that interbreeding is occurring at a low frequency (<1%). In chapter 3, I tested for a latitudinal cline in a polyglycine repeat located within the Per1 gene of Peromyscus and discovered a putative cline in the Per1-142 and Per1-157 allele of P. leucopus and P. maniculatus, respectively. Chapter 4, further expands upon these findings, limitations, and the lack of evidence supporting introgression at the Per1 locus. Despite this lack of evidence, it is possible that novel hybridization has or could lead to adaptive introgression of other genes, allowing for the exchange of adaptive alleles or traits that could be advantageous for range expansion and adaption to future environmental changes. Author Keywords: Clock genes, Hybridization, Latitudinal gradient, Per1, Peromyscus, Range Expansion
Impact of Wetland Disturbance on Phosphorus Loadings to Lakes
Total phosphorus (TP) concentrations have declined in many lakes and streams across south- central Ontario, Canada over the past three decades and changes have been most pronounced in wetland-dominated catchments. In this study, long-term (1980-2007) patterns in TP concentrations in streams were assessed at four wetland-dominated catchments that drain into Dickie Lake (DE) in south-central Ontario. Two of the sub-catchments (DE5 and DE6) have particularly large wetland components (31-34 % of catchment area), and wetlands are characterised by numerous standing dead trees and many young live trees (18 – 27 year old). These two streams exhibited large peaks in TP and potassium (K) export in the early 1980s. In contrast, TP and K export from DE8 and DE10 (wetland cover 19 – 20 %) were relatively flat over the entire record (1980-2007), and field surveys indicated negligible standing dead biomass in these wetlands, and a relatively healthy, mixed-age tree community. Furthermore, K:TP ratios in the DE5 and DE6 streams were around 5 in the early 1980s; very similar to the K:P ratio found in biomass, and as stream TP levels fell through the 1980s, K:TP ratios in DE5 and DE6 stream water increased. The coincidence of high TP and K concentrations in the DE5 and DE6 streams as well as evidence of a disturbance event in their wetlands during the early 1980s suggest that the two are related. The diameter of standing dead trees and allometric equations were used to estimate the amount of TP that would have been held in readily decomposed tree tissues in the DE5 wetland. The amount of P that would have been held in the bark, twig, root and foliage compartments of just the standing dead trees at DE5 was approximately half of the amount of excess stream TP export that occurred in the 1980s. This work suggests that disturbance events that lead to wetland tree mortality may contribute to patterns in surface water TP observed in this region. Author Keywords: Chemistry, Disurbance, Nutrients, Tree Death, Water, Wetland

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