1,721,018 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Impacts of climate change and intensive lesser snow goose (Chen caerulescens caerulescens) activity in high Arctic pond complexes - Banks Island, Northwest Territories
No full textRapid increases in air temperature in Arctic and subarctic regions are driving significant changes to surface water. These changes and their impacts are not well understood in sensitive high Arctic ecosystems. This thesis explores changes in surface water in the high Arctic pond complexes of western Banks Island, Northwest Territories, and examines the impacts of this change on vegetation communities. Landsat imagery (1985-2015) was used to detect trends in surface water, moisture, and vegetation productivity, aerial imagery change detection (1958 and 2014) quantified shifts in the size and distribution of waterbodies, and field sampling investigated factors contributing to observed changes. The impact of expanding lesser snow goose populations on observed changes in surface water was investigated using the aerial imagery change detection of 2409 waterbodies and an information theoretic model selection approach, while their impact on vegetation was assessed using data from field surveys. Our analyses show that the pond complexes of western Banks Island are drying, having lost 7.9% of the surface water that existed in 1985. This loss of surface water disproportionately occurred in smaller sized waterbodies, indicating that climate is the main driver. Model selection showed that intensive occupation of lesser snow geese was associated with more extensive drying and draining of waterbodies and suggests this intensive habitat use may reduce the resilience of pond complexes to climate warming. Evidence from field surveys suggests that snow goose foraging is also contributing to patches of declining vegetation productivity within drying wetland areas. Diminishing and degrading high Arctic pond complexes are likely to alter permafrost thaw and greenhouse gas emissions, as well as the habitat quality of these ecosystems. Additional studies focused the mechanisms of surface water loss, the direct impacts of wetland drying on vegetation, and the contributions of snow geese to these processes, are necessary to better understand the changes occurring on Banks Island.Graduat
The effects of climate change and fire on tundra vegetation change in the western Canadian Arctic
No full textRapid climate change is driving increases in tundra vegetation productivity and altering the frequency and severity of natural disturbances across the Arctic. While tundra vegetation change has been widespread, there is still uncertainty about the influence of fine-scale factors on change and the role of interactions between warming, disturbance, and vegetation change. In my MSc research I investigated how Arctic tundra vegetation is responding to ongoing climate change and more severe tundra fire in the western Canadian Arctic. In the first part of my thesis I measured post-fire soil and vegetation recovery along a burn severity gradient at six fires, which burned in 2012 in the Northwest Territories. My observations suggest that deciduous shrub communities (dominated by Betula glandulosa) are resilient to high severity fire and that severe fire promotes edaphic conditions that favor the persistence of this vegetation type. In the second part of my thesis, I investigated the spatial patterns of trends in tundra vegetation productivity over the past three decades using Random Forests machine learning to analyze Enhanced Vegetation Index (EVI) data derived from Landsat imagery. My Random Forests models of the relationship between Landsat EVI trends and biophysical variables showed that two-thirds of the western Canadian Arctic productivity has increased during the past three decades and that this change is occurring most rapidly in dwarf and upright shrub-dominated regions. Taken together, my research demonstrates that shrub tundra communities are well adapted to severe fire and show increasing productivity in response to warming Arctic temperature. My research also indicates that these relationships can be highly complex at finer scales, where they are mediated by local variations in microclimate, topography, and moisture.Graduat
Monitoring environmental conditions using participatory photo-mapping with Inuvialuit knowledge holders in the Mackenzie Delta Region, Northwest Territories
Full text linkThe Mackenzie Delta region of Northwestern Canada is a dynamic environment that is ecologically and culturally significant. This region is experiencing rapid environmental change that is expected to worsen with continued climate warming and additional anthropogenic stressors. In northern regions, conventional environmental monitoring strategies can be hindered by complex and cost prohibitive logistics. In this context of environmental change and uncertainty, there is a critical need to draw on traditional ecological knowledge (TEK) and observations to inform decision-making. In some areas changes in land cover are occurring so rapidly that maintaining an accurate inventory is problematic. Knowledgeable land users are in a unique position to assess changes in regional environmental conditions and inventory cumulative impacts.
Environmental decision-making in the Inuvialuit Settlement Region requires Inuvialuit participation in several co-management bodies. The objectives of this project were to develop and field-test a community-based monitoring program that shares Inuvialuit observations with stakeholders in environmental decision-making in a standardized and accessible format. Working with the Hunter and Trapper Committees of Aklavik, Inuvik, and Tuktoyaktuk, the Inuvialuit Joint Secretariat, and the Cumulative Impacts Monitoring Program we (1) adapted a participatory photo-mapping (PPM) method to record Inuvialuit observations of environmental conditions using a strategy consistent with community goals and Inuvialuit culture.
In the summer of 2010, we worked with knowledgeable Inuvialuit hunters and land users to document Inuvialuit observations of environmental conditions using digital cameras and hand held GPS units. Subsequently, digital photographs and video footage became the focus of photo-elicitation interviews, which added a detailed narrative to each geo-referenced observation. Following fieldwork and interviews, geo-referenced photos, video, and associated text files were entered into web-based map. Approximately 150 observations were mapped and grouped into 33 themes.
Interviews with monitors and a range of potential map users suggest that web-based mapping is an effective way to record and share observations and concerns related to the regional environment. We found that PPM could be very useful for northern researchers, decision-makers, and planners because it can facilitate knowledge transfer among stakeholders, facilitate community consultation, and contribute to environmental impact assessment and monitoring strategies. Our experience suggests that by providing a record of the location and magnitude of anomalous environmental conditions, this monitoring initiative will contribute northern planning and decision-making, and the communication of TEK and observations among northern stakeholders. Overall, this research highlights the effectiveness of using the web-based PPM tool to document and share Inuvialuit observations. A monitoring program built around TEK and observations that are linked to geo-referenced images (and other media) will significantly improve our capacity to detect the impacts of environmental change.
(1) Because chapters 2 and 3 were co-authored, plural was used throughout the entire document.Graduat
The ecological effects of storm surges on Arctic bird and vegetation communities in the outer Mackenzie Delta, Northwest Territories
No full textCoastlines in the Western Canadian Arctic are predicted to experience increases in the frequency and intensity of storm surges as rapid climate change continues to alter weather and biophysical factors of this land-sea connection. Although storm surges have the potential to cause widespread and persistent vegetation loss, little information is available about the influence of decreasing disturbance intervals (between storms), expected timelines of recovery for vegetation, and how this dramatic vegetation change alters habitat availability and/or quality for local wildlife populations. In my MSc research, I investigated how Arctic bird diversity is affected by heterogeneous vegetation recovery post-storm and characterized ecological recovery of vegetation from repeated disturbance. In the first part of my thesis (Chapter 2), I used a combination of Landsat & Sentinel satellite imagery (1984-2019) and measured post-storm soil & vegetation attributes to characterize vegetation loss and recovery in areas of the outer Mackenzie Delta (NWT) affected by storm surges in 1999 and 2016. My observations of areas affected by the 1999 storm indicate that sites farther from the river channel lacked vegetation re-establishment and had higher soil salinity. Furthermore, our analyses suggest that sites affected by the 1999 storm that were re- inundated by the 2016 storm differed in response depending on whether sites had previously revegetated or not; more vegetation re-established at the previously unvegetated sites, whereas there were decreases in the diversity of the plant community re-establishing at the previously revegetated sites. In the second part of my thesis (Chapter 3), I employed field survey protocols from the Program for Regional and International Shorebird Monitoring (PRISM) to investigate how avian community assemblage is affected by heterogeneous re-vegetation 20 years following the 1999 storm. Comparisons of my bird survey data with vegetation and habitat factors showed that the drier, post-storm vegetation barrens were preferred by ground-nesters or species that use open habitats such as lapland longspur and semipalmated plover; whereas the wetter, mostly ponded, revegetated habitats were frequented by species of ducks, red-necked phalarope, and savannah sparrow. Taken together, my research shows that areas that have revegetated after the 1999 storm can be considered as functionally recovered in comparison to our Reference (i.e., unaffected) sites in terms of vegetation and bird communities, but that areas still exist ~20 years post-storm that do not show any characteristics of recovery.Graduat
Carbon fluxes from high-centred polygonal terrain in the Northwest Territories
No full textNorthern regions account for approximately 30% (1035 Pg) of the world’s soil organic carbon (SOC). Much of this carbon is currently stored in permafrost soils, which are vulnerable to increasing air and ground temperatures. Permafrost landscapes rich in ground ice, such as high-centred polygonal terrain, are likely to be highly vulnerable to thaw. Degradation of ice wedges in high-centred polygonal terrain causes increased moisture and ground temperatures. These environmental controls are likely to have a large impact on carbon cycling in this terrain type. My M.Sc. research combined both lab and field-based analyses to investigate current and potential carbon emissions from high-centred polygonal terrain in the Tuktoyaktuk Coastlands.
To estimate the magnitude of future emissions from this terrain type I incubated six permafrost cores collected at two sites. Peat cores from four depths were each incubated under four conditions (cold anaerobic, warm anaerobic, cold aerobic, warm aerobic). The observation that carbon mineralization rates do not vary with depth demonstrates that the soil carbon liberated from permafrost in high-centred polygonal terrain will not be limited by SOC quality. This experiment also shows that emission rates will be moderated by temperature and moisture levels, and will be primarily in the form of CO2. To examine the impact of ice-wedge thaw on carbon emissions in high-centred polygonal terrain, we combined opaque chamber measurements of flux and estimates made from water samples using a gas diffusion model. Field sampling at two sites contrasted carbon emissions from polygon centres (n=18), wet troughs (n=18) and ponds (n=20). We also measured ground temperature and soil moisture using thermistors and a moisture sensor. Our field results demonstrate that ice-wedge degradation results in increased ground temperature, deeper active layers, and increased CO2 and CH4 emissions. Contrary to our expectations, CO2 emissions were not limited by waterlogged conditions, demonstrating the importance of anaerobic CO2 production. Our field measurements demonstrate that increasing temperatures are correlated with rising CO2 emissions in aerobic environments, and rising CO2 and CH4 emissions in anaerobic environments. Taken together, these two studies demonstrate that as ground temperatures increase in high-centred polygonal terrain, carbon emissions from ecosystem respiration are likely to increase.Graduate04810425076
Challenges and opportunities of urban food production : a case study from Victoria, British Columbia
Full text linkFood production in urban areas has been conducted worldwide as a subsistence strategy and source of income. Recently, however, it is recognized that urban agriculture has the potential to contribute to the development of sustainable urban environments. This study examines the benefits of urban food production in North American cities, as well as focusing on some of the critical barriers to its widespread expansion and acceptance. It also explores the potential for contamination of produce from the ambient atmosphere in mid-sized urban centres.
Through interviewing nine urban farmers and one urban planner, in the city of Victoria, British Columbia, I documented each producer’s knowledge of the benefits and limitations associated with urban food production. Each interviewee impressed upon me the numerous benefits that can be accrued through the practice of urban agriculture, but they also painted a picture of the struggles that urban farmers face. Issues identified included: a real and perceived risk of contamination, problems with land ownership and access, and lack of meaningful support for urban farmers. Although urban agriculture has been accepted in principle by the City of Victoria and other Canadian cities, there are many challenges that must be overcome for urban food production to truly produce a viable, sustained food system. A coordinated, comprehensive government policy for involvement in the urban food system is critical to effectively addressing urban food issues.
Investigations of heavy metal levels in lettuce (Lactuca sativa) grown in sampling sites across an urban/rural gradient showed that atmospheric contamination by heavy metals is greatest at urban sites, but also affects residential and rural sites. Sampling site types included: a control area (rural farms and properties outside of Victoria); residential sites (yards in residential neighbourhoods in the City of Victoria); and, industrial/business sites (heavily trafficked and industrialized areas in downtown Victoria). Site types were intended to reflect areas perceived as safe, probably safe, and probably not safe, and were selected based on expert opinion and land use. Results indicate that caution should be exercised in growing leafy greens at downtown sites, and that growing food in most residential neighbourhoods and green spaces is typically no worse than growing greens in rural Victoria. In fact, due to the proximity of urban agriculture to the market, growing food locally eliminates the need for transportation and extra processing; reducing the extra exposure crops otherwise might face during these phases.
Urban food production requires the support of communities and governments in order to contribute to both urban food security and urban sustainability. The City of Victoria has started on a path to ensuring that this food system receives the required support, but it requires concerted effort and action. Further research into urban food systems is necessary to ensure that urban food production is able to become a viable, sustained food system.Graduat
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Springtime in the Delta: the sociocultural role of muskrats and drivers of their distribution in a changing Arctic delta
No full textClimate change is altering environmental conditions in Canada’s western arctic, including hydrology, permafrost, vegetation, and lake habitat conditions in the heterogeneous landscape of the Mackenzie Delta. The delta is an expansive alluvial plain dominated by thousands of lakes and interconnected channels that provide habitat for fish, birds, and mammals. Muskrats (Ondatra zibethicus) are a culturally important ecological indicator species found in the Delta. Throughout the 1900s, Gwich’in and Inuvialuit residents in the Delta relied heavily on the muskrat for food, fur, and culture, but as in other regions around the world, changing socioeconomic and ecological conditions are altering the land and Indigenous Peoples’ access to it. This can strongly impact communities by affecting food security, physical health, and overall wellbeing. In the first part of this thesis, I investigated the role of muskrats in the cultural traditions and land-based livelihoods of the Gwich’in and Inuvialuit residents of the Mackenzie Delta by conducting interviews and meetings with over 70 community members. Although the role of muskrats has changed over the last 100 years, muskrat harvesting continues to offer Delta residents a meaningful way to remain engaged in, perpetuate, and strengthen their cultural identity and land-based traditions among generations, and ultimately, to foster individual and community wellbeing.
In the second part of this thesis, I investigated the importance of landscape connectivity and patch quality – two properties affected by climate change – on muskrat presence and distribution in the Mackenzie Delta, using remote sensing and field-based surveys of lakes with and without muskrats present in the winter. I tested multiple hypotheses about predictors of muskrat presence and biomass using a model-selection, information theoretic approach. My results show that patch quality related to specific habitat requirements is a more important driver of muskrat distribution than landscape connectivity in the Mackenzie Delta. Muskrats were more likely to occur in lakes with longer perimeters, higher amounts of edible submerged macrophyte biomass, and sediment characteristics that supported macrophyte growth. The latter two conditions are related to spring flooding regimes, which are likely to be altered by climate change. This may result in a decrease in the quality and quantity of preferred muskrat habitat in the Mackenzie Delta. My research indicates that patch quality and landscape-level processes are important for understanding species distributions in heterogeneous landscapes.Graduat
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