Hugenholtz, Christopher

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https://opus.uleth.ca/handle/10133/3322

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Browsing Hugenholtz, Christopher by Subject "Dissertations, Academic"

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    The effects of dune stabilization on the spatiotemporal distribution of soil moisture resources, Northern Great Plains, Canada
    (Lethbridge, Alta. : University of Lethbridge, Dept. of Geography, c2012, 2012) Koenig, Daniel Edgar; Hugenholtz, Chris H.; Letts, Matthew G.
    In dryland environments, the availability of soil moisture is the primary control on plant species’ distributions. In the sandhill regions of the northern Great Plains, vegetation establishment has transformed highly mobile, desert-like dune fields into stabilized landscapes covered by mixed-grassland prairie. This study examines how dune stabilization has modified the spatiotemporal distribution of soil moisture resources. An ergodic (space-for-time) approach was used, comparing soil moisture dynamics on active and vegetation-stabilized dunes in the Bigstick Sand Hills of southwestern Saskatchewan. Results indicate that while dune stabilization has enhanced near-surface soil moisture availability, deeper profile soil moisture recharge is reduced. Through better understanding how vegetation has modified soil moisture dynamics in stabilizing sandhill regions, better management practices may be implemented to maintain water resource availability and ecosystem health.
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    Field-based aeolian sediment transport threshold measurement : sensors, calculation methods, and standards as a strategy for improving inter-study comparison
    (Lethbridge, Alta. : University of Lethbridge, Dept. of Geography, 2010, 2010) Barchyn, Thomas E.; University of Lethbridge. Faculty of Arts and Science; Hugenholtz, Chris H.
    Aeolian sediment transport threshold is commonly defined as the minimum wind speed (or shear stress) necessary for wind-driven sediment transport. Threshold is a core parameter in most models of aeolian transport. Recent advances in methodology for field-based measurement of threshold show promise for improving parameterizations; however, investigators have varied in choice of method and sensor. The impacts of modifying measurement system configuration are unknown. To address this, two field tests were performed: (i) comparison of four piezoelectric sediment transport sensors, and (ii) comparison of four calculation methods. Data from both comparisons suggest that threshold measurements are non-negligibly modified by measurement system configuration and are incomparable. A poor understanding of natural sediment transport dynamics suggests that development of calibration methods could be difficult. Development of technical standards was explored to improve commensurability of measurements. Standards could assist future researchers with data syntheses and integration.
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    Plant-insect interactions between yellow toadflax, Linaria vulgaris, and a potential biocontrol agent, the gall-forming weevil, Rhinusa pilosa
    (Lethbridge, Alta. : University of Lethbridge, Department of Biological Sciences, c2011, 2011) Barnewall, Emily C.; University of Lethbridge. Faculty of Arts and Science; De Clerck-Floate, Rosemarie; Goater, Cameron P.
    Yellow toadflax, Linaria vulgaris (L.) Mill. (Plantaginaceae), is a non-native invasive plant. Rhinusa pilosa Germar (Coleoptera: Curculionidae) is a proposed biocontrol agent. Gall development by R. pilosa was described using histological methods and compared between plant populations from native and introduced ranges. Key stages of oviposition were isolated histologically to determine their importance in gall induction. Rhinusa pilosa galled and developed on four geographically distinct Canadian populations in a pre-release quarantine study. Low agent densities only negatively affected one population. High densities of R. pilosa reduced potential reproductive output and plant biomass. Conducting detailed investigations into the biology, impact, and development of R. pilosa on populations from invasive and native ranges may help predict the efficacy of R. pilosa in the field if approved for release and.goes beyond current pre-release testing requirements.