Peatland ecosystems are important as natural climate regulators for their capacity to store carbon over long-time scales. Carbon cycling in peatlands in the boreal ecozone of Canada has been more widely studied than the boreal shield of Ontario, where peat depths are thinner and peatlands spatially smaller. The reliance on fill and spill hydrologic connectivity makes the water table dynamics of peatlands in Ontario’s Eastern Georgian Bay (EGB) region of the Ontario shield ecozone sensitive to rain and drought periods. The drying of wetlands in the EGB region decreases moss productivity and increases the ecosystem’s vulnerability to wildfire through an increase in the water table depth. In an effort to understand how peatlands respond to interannual climate variability and wildfire, we examined the role of regional climate patterns on growing season CO2 exchange from an Ontario shield peatland and completed a post-wildfire assessment of CO2 exchange patterns in a recently burned peatland for the first and second year post-wildfire. Using the eddy covariance technique, we analyzed 5-years of growing season CO2 exchange data from 2016 to 2020 from an unburned peatland and 2-years of growing season CO2 exchange data from a burned peatland (2019-2020) in EGB. Plot-scale CO2 exchange measurements were also completed within the burned peatland jointly with abiotic variables and vegetation community surveys. Water table depth was identified as an important variable to explain total summer CO2 uptake (GPP) and net ecosystem exchange (NEE), where years of considerable rainfall maintained a water table near the peat surface and perpetuated high vegetation productivity. Summer total ecosystem respiration (ER) was greatly influenced by preceding winter and spring air temperature, with warmer winter air temperatures leading to summers of increased total ER. Warmer winter air temperatures also initiated water flow across the landscape, thus reviving plant and microbial activity following snow cover. These findings have important implications for the function of these shallow Ontario shield peatlands in a warming climate, where decreased water availability with projected increased temperatures and evapotranspiration leaves peatlands at risk of a net loss of C over the summer with lower water table. In the burned landscape, there was lower GPP in the summer (2019) compared to the wet summer of 2020, however the burned landscape continued to act as a net CO2 sink for the summer season of both years. The rapid recovery of vegetation across the wildfire-disturbed landscape has important implications for the function of these peatlands over time, with the ability for continued carbon uptake and reinstating peat accumulation processes. / Thesis / Master of Science (MSc)

A scapolite-hornblende-biotite schist from the Grenville province of the Canadian Shield has been analysed for Tl by an atomic absorption technique with a high sensitivity. K, Rb and some major oxides were determined by wet chemistry. Tl, K/Rb, K/Tl and Tl/Rb were compared to several other rocks and for this report were found to be 432ppb, 429, 4.85x10³ and 88.4x10⁻³ respectively. These values are similar to those quoted for other rocks. / Thesis / Bachelor of Science (BSc)

Ecotourism offers a non-consumptive form of economic activity globally. Human activity, however, might negatively affect the ecology of areas and their biota, likely varying with type and intensity of ecotourism. Wildlife, for example, might perceive ecotourists as predators, and adjust behaviour accordingly (i.e., human avoidance). Alternatively, wildlife might actually seek human activity if it protects them from greater risks (Human Shield Hypothesis). The Anthropause, a period of decreased human activity due to COVID-19, provided unparalleled opportunity to examine wildlife behaviour when perceived risks from humans were removed. In partnership with the Kitasoo Xai’xais First Nation (KX), we assessed if and how ecotourism, in the form of bear-viewing, might influence spatial and temporal activity of grizzly bears. We deployed remote cameras in the Khutze watershed in 2020 in the absence of human use. To provide increased inference when tourism resumed in 2021, KX implemented alternating spatial closure experiments within the watershed. Additionally, in 2021 we implemented a tourist group size experiment in a second watershed, Green River. In Khutze, we found that a closure of 25 days was required for bear detection rate to return to the 2020 (non-ecotourism) level. We did not observe an influence of the alternating within-watershed north-south closures on activity. The data also revealed complex relationships among bear detections, ecotourism activity, and salmon availability, varying by age and sex of bears. Specifically, we found a human shield effect for females with young when salmon levels were moderate to high, but this effect diminished in times of low salmon. An activity pattern analysis in Khutze did not show an effect of ecotourism. In Green, where inference was likely constrained by our short-term experiment, we found a positive influence of the number of days since people were present on detection rate. We additionally found temporal avoidance of within 100m of the viewing site on days when people were present. These patterns from both watersheds show the complex ways in which wildlife can respond to even seemingly benign human presence. Inference from this research has application to wildlife, land, and ecotour management by the KX, who are reasserting authority in governance. More broadly, this study contributes to literature on the dynamic landscape of fear induced by spatiotemporal variation in human activity. / Graduate / 2023-09-09

As part of the collaborative Dorset Research Project investigating mercury and energy fluxes in fresh-water lakes, I measured mercury in the seston (Chapter 1) and studied the biomanipulation impacts on the phytoplankton (Chapter 2) of two Precambrian Shield lakes. Sestonic-mercury (HgT) was measured in the metalimnion and hypolimnion of each lake throughout the summer of 1995 to determine seasonal fluctuations and the relationship with algal productivity. In each lake, sestonic-HgT (pg Hg/L) did not significantly change in the metalimnion but significantly increased in the hypolimnion by season's end. Combined influences of external HgT inputs, seston sedimentation and increased methylmercury production in the hypolimnia over the season may have contributed to these trends. In comparison to other variables measured, algal productivity was highly correlated with sestonic mercury concentrations in both lakes at each limnetic depth. Although there were no significant differences between lakes with respect to average weight-specific HgT (pg HgT/mg D.W.), chlorophyll a exhibited the best correlations with HgT in MouseL. whereas algal biomass was more highly correlated with HgT in Ranger L. This disparity between lakes may be the result of apparent inter-lake differences in light availability and algal community structure. It was also apparent that changes in the proportions of large and small cells over the season affected the magnitude of sestonic mercury measured. With respect to the potential for trophic transfer of mercury, I suggest that small edible algal cells may bioconcentrate more mercury per unit weight than larger, inedible ones. The data also indicate that seston samples should be collected throughout the season at discrete depths if sestonic-mercury measurements are to be used in trophic transfer models. I also examined the effects of fish biomanipulation on the phytoplankton community of these study lakes. Prior to the biomanipulation, Ranger L. had a top-piscivore community whereas Mouse L. had a top-planktivore community. The biomanipulation involved the removal of top-piscivores from Ranger L. and adding top-piscivores to Mouse L. Trophic Cascade theory predicts that algal biomass in these lakes, with their similar morphometries and resource characteristics, should be ultimately controlled by top-consumer abundance. In addition, model predictions expect "edible" algal size-classes and groups in the community to experience the greatest changes in abundance. Therefore in Ranger L., it was expected that the removal of piscivores would result in higher algal biomass (particularly edible algae), whereas the addition of piscivores in Mouse L. would result in lower algal biomass (particularly edible algae). However, for those years following the biomanipulation, algal biomass significant increased in both lakes compared to pre-manipulation years. This suggests that variables other than direct trophic forces were controlling algal biomass from year to year, regardless of changes in the fish communities. When algal size-classes were tested, only edible cells varying from 10-30 μm increased in Mouse L., contrary to what was predicted. In Ranger L., large cells and colonies > 30 μm unexpectedly increased when all other size-classes did not significantly change. With respect to algal group composition, both Greens and Cryptomonads significantly increased in Mouse L. whereas only Greens significantly increased in Ranger L.. Both of these groups were considered to be edible and thus these results were not consistent with the model predictions. As such, I suggested that "bottom-up" influences were important in controlling both size-class and taxonomic abundances. However, when individual size-classes of representative algal genera were compared between pre-and post-manipulation years, there were some effects which may be attributed to the biomanipulation. In particular, large Green colonies became prevalent in Mouse L. during post-manipulation years as a probable response to increased grazing pressure. Conversely, "edible" Greens became prevalent in Ranger L. after the biomanipulation, supporting the prediction of reduced zooplankton grazing pressure. These results have revealed the necessity to test specific algal genera of varying size-classes in order to detect the effects of biomanipulation. They also showed that the majority of algal genera, regardless of size, were not affected by the biomanipulation. Limitations to my interpretation of the data are discussed and vary from time-scale issues to consumer and resource availability unknowns. Along with recommendations for further studies in this area, I hypothesized that the trophic transfer of sestonic-mercury to zooplankton could be intensified if small, edible algal genera (shown to be impacted by Top-Down forces), have relatively higher weight-specific mercury concentrations. However, considering that the phytoplankton community as a whole has shown resilience to herbivory, I also suggest that the majority of mercury measured in the seston is not available for trophic transfer to zooplankton consumers. / Thesis / Master of Science (MSc)

The 2012 Decadal Survey has stated that there is a critical role for a Venus In-situ Explore (VISE) missions to a variety of important sites, specifically the Tessera terrain. This work aims to answer the Decadal Survey's call by developing a new comprehensive Entry, Descent, Landing, and Locomotion (EDLL) vehicle for in-situ exploration of Venus, especially in the Tessera regions. TANDEM, the Tension Adjustable Network for Deploying Entry Membrane, is a new planetary probe concept in which all of EDLL is achieved by a single multifunctional tensegrity structure. The concept uses same fundamental concept as the ADEPT (Adaptable Deployable Entry and Placement Technology) deployable heat shield but replaces the standard internal structure with the structure from the tensegrity-actuated rover to provide a combined aeroshell and rover design. The tensegrity system implemented by TANDEM reduces the mass of the overall system while enabling surface locomotion and mitigating risk associated with landing in the rough terrain of Venus's Tessera regions, which is otherwise nearly inaccessible to surface missions. TANDEM was compared to other state-of-the-art lander designs for an in-situ mission to Venus. It was shown that TANDEM provides the same scientific experimentation capabilities that were proposed for the VITaL mission, with a combined mass reduction for the aeroshell and lander of 52% (1445 kg), while eliminating the identified risks associated with entry loads and very rough terrain. Additionally, TANDEM provides locomotion when on the surface as well as a host of other maneuvers during entry and descent, which was not present in the VITaL design. Based on its unique multifunctional infrastructure and excellent crashworthiness for impact on rough surfaces, TANDEM presents a robust system to address some of the Decadal Survey's most pressing questions about Venus. / Ph. D. / NASA has proposed the possibility of performing a robotic mission to Venus in this upcoming decade. This could be NASA’s first attempt to design a robot that is capable of landing on the surface of our solar systems hottest planet. Venus presents a great exploration opportunity, as it is our closest planetary neighbor. Venus is similar to Earth in both size and location in the solar system, yet it is profoundly different in many other aspects regarding habitability. There is a significant scientific interest in exploring the mysteries of the greenhouse gases and runaway climate change present in the Venusian atmosphere. Understanding Venus’ atmosphere will help us to increase our knowledge of Earth’s atmosphere. Exploring the difference in these two planets will greatly further our intuition of other planetary systems and will aid in our search for life in the universe. Yet, exploring Venus presents a number of severe engineering challenges: the extreme temperature and pressure at the planet's surface, the highly corrosive atmosphere, and lack of terrain resolution caused by the dense permanent cloud layer. In order to address these engineering challenges, a new ultra-lightweight planetary probe has been invented. TANDEM, the Tension Adjustable Network for Deploying Entry Membrane, is unique in its design as it has combined all of the subsystems in needs to safely land on the surface into a single lightweight, multifunctional structure. This enables the design to be nearly 1.5 metric tons lighter than the same mission that was proposed in 2010 using the current state-of-the-art technologies. Based on this and other unique capabilities that are provided, TANDEM presents a robust system to address some of NASA’s most pressing questions about Venus.

No / A shield of beaten bronze from South Cadbury, Somerset, England is the first shield to be discovered by excavation on an archaeological site. The shield lay in a silt-filled Bronze Age ditch on a spur of land below Cadbury Castle. A stake was thrust through the shield. The paper considers the recovery and conservation of the shield, the technology of metal shields and the evidence for the ritual deposition of shields in the Later Bronze Age of western Europe.

The rock art that is found in the region of Reindeer Lake, Saskatchewan is part of a larger category of rock art known as the Shield Rock Art Tradition. At present, there are more than 400 known and recorded rock art sites throughout the Canadian Shield region. These sites are found over an extensive geographical area and can be found from south-western Quebec across the Shield westward, up to north-western Saskatchewan. The majority of these rock art sites are comprised of imagery that has been painted on rock surfaces. The rock art sites at Reindeer Lake, or panels as they are called, depict a variety of symbols and characters that portray humans, animals, anthropomorphs, ceremonies and motifs of a spiritual nature. A variety of explanations have been proposed as to the function and meaning of rock art in general. Among the more accepted explanations are that rock art paintings were created by shamans; that they depict dreams or visions of an individual seeking medicine or participating in a vision quest/puberty rites; that they are a form of hunting magic whereby the author in capturing the animal in a painting assures capture of the animal in life; or that they serve as markers for travellers. Regardless of function and meaning, all of the rock art sites on Reindeer Lake are of immense heritage value and should be regarded as sacred locations. Very little is known about the rock art in the Reindeer Lake regions. Before any significant analyses of their meaning can be conducted, they must first be relocated and properly documented. At present there are only a very small number of publications that document or mention the Reindeer Lake rock art. This thesis surveys the rock art of Reindeer Lake, Saskatchewan. It discusses the general nature of pictographs from the Shield Rock Art Tradition and how the panels at Reindeer Lake fit into the overall scheme, and applies a systematic method to the recording and analysis of pictographs using a contextual approach. Although the primary focus is on recording the painted imagery, the specific context of each panel as well as the surrounding landscape is also considered. Recording these ancient rock art sites using a proper systematic method has ensured that this significant element of Aboriginal culture will endure not only for future research, but also for the benefit of future generations of the local Cree people.

The rock art that is found in the region of Reindeer Lake, Saskatchewan is part of a larger category of rock art known as the Shield Rock Art Tradition. At present, there are more than 400 known and recorded rock art sites throughout the Canadian Shield region. These sites are found over an extensive geographical area and can be found from south-western Quebec across the Shield westward, up to north-western Saskatchewan. The majority of these rock art sites are comprised of imagery that has been painted on rock surfaces. The rock art sites at Reindeer Lake, or panels as they are called, depict a variety of symbols and characters that portray humans, animals, anthropomorphs, ceremonies and motifs of a spiritual nature. A variety of explanations have been proposed as to the function and meaning of rock art in general. Among the more accepted explanations are that rock art paintings were created by shamans; that they depict dreams or visions of an individual seeking medicine or participating in a vision quest/puberty rites; that they are a form of hunting magic whereby the author in capturing the animal in a painting assures capture of the animal in life; or that they serve as markers for travellers. Regardless of function and meaning, all of the rock art sites on Reindeer Lake are of immense heritage value and should be regarded as sacred locations. Very little is known about the rock art in the Reindeer Lake regions. Before any significant analyses of their meaning can be conducted, they must first be relocated and properly documented. At present there are only a very small number of publications that document or mention the Reindeer Lake rock art. This thesis surveys the rock art of Reindeer Lake, Saskatchewan. It discusses the general nature of pictographs from the Shield Rock Art Tradition and how the panels at Reindeer Lake fit into the overall scheme, and applies a systematic method to the recording and analysis of pictographs using a contextual approach. Although the primary focus is on recording the painted imagery, the specific context of each panel as well as the surrounding landscape is also considered. Recording these ancient rock art sites using a proper systematic method has ensured that this significant element of Aboriginal culture will endure not only for future research, but also for the benefit of future generations of the local Cree people.

Approved for public release; distribution in unlimited. / The International Space Station (ISS) must be able to withstand the hypervelocity impacts of micrometeoroids and orbital debris that strike its many surfaces. In order to design and implement shielding which will prevent hull penetration or other operational losses, NASA must first model the orbital debris and micrometeoroid environment. Based upon this environment, special multi-stage shields called Whipple and Enhanced Stuffed Whipple Shields are developed and implemented to protect ISS surfaces. Ballistic limit curves that establish shield failure criteria are determined via ground testing. These curves are functions of material strength, shield spacing, projectile size, shape and density, as well as a number of other variables. The combination of debris model and ballistic limit equations allows NASA to model risk to ISS using a hydro-code called BUMPER. This thesis modifies and refines existing ballistic limit equations for U.S. Laboratory Module shields to account for the effects of projectile (debris/ micro-meteoroid) densities. Using these refined ballistic limit equations this thesis also examines alternative shielding materials and configurations to optimize shield design for minimum mass and maximum stopping potential, proposing alternate shield designs for future NASA ground testing. A final goal of this thesis is to provide the Department of Defense a background in satellite shield theory and design in order to improve protection against micrometeoroid and orbital debris impacts on future spacebased national systems. / Lieutenant, United States Navy

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