1,721,067 research outputs found
New dimensions in agroecology
No full textDavid Clements, Anil Shrestha, editors.xv, 553 p. : ill. ; 23 cm
Understanding plant-soil-management interactions of Reynoutria spp. (knotweeds) to inform ecological restoration
No full textThe management of knotweed species (Reynoutria spp.), aggressive clonal invasive plants of riparian areas, present unique management challenges, particularly within the province of British Columbia (BC) where a knowledge gap exists between field practitioners who work to control knotweed infestations and academic researchers who study them. Academic research on invasive plant management tends to apply a target-based lens, which limits our knowledge to effectively control invasive plants long-term. The primary objective of this research project was to shift this focus from a target-based approach to other often overlooked important relationships, such as plant-soil-management interactions. These are relationships that may reveal much needed solutions to effective long-term control and subsequent ecological restoration. Accomplishing this required a broad set of research questions: 1. Examining the soil microbial ecology of knotweed infestations and native salmonberry (Rubus spectabilis) dominated sites. We found that knotweed infestation altered the soil bacterial community, decreased arbuscular mycorrhizal fungi (AMF) abundance and increased phosphorus compared to soil from salmonberry; 2. Testing the efficacy of a non-chemical control method that could be used near waterways where herbicide use is restricted, wire mesh girdling. It was determined that wire mesh significantly reduced stem and patch height but did not eradicate knotweed infestations in a field setting after two years; and 3. Attempting to conduct a dose-response assay to test for resistance to glyphosate in knotweed. Invasive Plant Managers have been reporting cases of epinastic knotweed patches in BC for several years that seem unaffected by repeated annual herbicide treatment. Rhizomes were collected from two such epinastic populations in Port Alice and North Vancouver, BC. However, a series of climate events impacted the ability to conduct the necessary experiments, and resistance to glyphosate could not be confirmed. While climate events had a significant impact on investigation of research questions, our primary research objective to focus on plant-soil-management interactions was accomplished and demonstrates that bridging the practitioner-researcher divide is critical to meeting long-term ecological restoration goals. The research also illuminates the importance of further understanding the legacy of knotweed invasion on the soil to inform restoration of native ecosystems in the post-control phase.Land and Food Systems, Faculty ofGraduat
Effects of climate change on the habitat suitability of 4 relatively new invasive plant species in the Pacific Northwest
No full textInvasive species are a substantial threat to biodiversity and ecosystem structure. This threat is exacerbated by the increasingly concerning and urgent outlook of predicted climate change, land cover change, and other human influences. Specifically, an increasing number of invasive plant species are spreading in the Pacific Northwest (PNW), an area of unique natural areas, economic value, and increasing human population. Predicting the potential habitat suitability for invasive plant species that are not yet established in the region is crucial for developing preventative management strategies. To this end, I developed habitat suitability models for four invasive plant species, two terrestrial species: Geranium lucidum and Pilosella officinarum; and two aquatic species: Butomus umbellatus and Pontederia crassipes. I initially considered 33 bioclimatic variables, 10 land cover types, and a human influence index as current model predictor variables with location records for each species drawn from the introduced range (North America). I projected each species’ current habitat suitability in the PNW region using ensemble modelling of six algorithms to 2050 and 2080, under 3 potential future climate scenarios. The majority of the coastal PNW is predicted to remain potential habitat for Geranium lucidum under all future climate scenarios, with some loss of habitat suitability in Oregon. In contrast, Pilosella officinarum, while currently suited to most inland regions of the PNW, is predicted to lose suitable habitat by 2050 under all climate scenarios, retaining high elevations as potential habitat. The suitable habitat for Butomus umbellatus in the PNW, which is currently moderately suitable, is not predicted to increase substantially in the future. Likewise, potential future habitat suitability remains relatively unchanged for Pontederia crasipes, which is currently highly suitable for inland waterways that do not experience freezing temperatures. Overall, the bioclimatic variables and human influence index were more important than land cover variables, suggesting that climate change and human activity are the determining factors for changes in future suitable habitat. My research provides a template to model other concerning species, assisting local land managers and practitioners to inform current and future management strategies and increasing the efficiency of allocating limited resources toward species with expanding ranges.Arts, Faculty ofGeography, Department ofGraduat
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Soil microbial effects on weed seedbank persistence: current knowledge and applications for weed management
No full textChapter 13. The use of microbe–seed interactions for weed management has been variously discussed over the last few decades, and soil microbes have been demonstrated to play an important role in affecting weed seedbank persistence and weed demography. However, very few weed management applications based on such interactions have so far been successfully tested under field conditions. This chapter provides an up-to-date summary of what is known about direct interactions between buried weed seeds and soil-borne microbes. The principal mechanisms of microbial attack of seeds, the roles of abiotic environmental factors and of biotic interactions in modulating microbe–seed interactions, and seed defence mechanisms underlying weed seed resistance to microbial decay are herein discussed. In addition, how these different aspects can affect weed management applications, via soil inoculation with seed-pathogenic microbes, the manipulation of environmental conditions to promote seed decay processes, and the weakening of seed defences against microbial attack is also discussed. These approaches can be deployed alone or in combination, but combinational approaches may be more promising when designing weed management applications. As shown in this chapter, due to the availability of modern molecular microbial methods, remarkable progress has been made in understanding seed defences and defence syndromes and mechanisms of microbial attack. However, the underlying processes in the field are still only very poorly understood, and a more detailed conceptual framework of how soil-borne seed-decaying microorganisms, weed seeds and their seed-borne microflora, and their environment interact with each other must be developed to facilitate the development of more reliable weed management options
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