Search and rescue: detection and mitigation of rare vascular plant species

  • Author / Creator
    Dennett, Jacqueline M
  • Understanding where and when populations occur is the first step to conservation and maintenance of biodiversity. Where human land-use overlaps with populations of conservation concern, population loss may occur, potentially reducing long-term persistence of species, particularly for those that are rare. Understanding the relationship between land-use change and extirpation is therefore essential to guiding conservation, but this can only be achieved through well-designed surveys and monitoring programs. One key aspect of surveys that is often overlooked is the ability to accurately and consistently detect populations, while the success of mitigation practices depends on a clear understanding of what techniques will best ensure the longevity of a given population. In this thesis, I examined factors that affect detection, extirpation of historic populations, and the efficacy of mitigative translocations for rare vascular plants in the oil sands region of Alberta. First, I used two field experiments to better understand and test the effects of scale (1 – 2500 m2), abundance (plant density), and observer experience on detection rates of rare plants in forested systems. Scale and abundance were the most important determinants of detection for plot-based surveys, whereas previous experience of the observer had limited influence. Plants at low abundance often went unrecorded in large plots (>1000 m2), even when they were morphologically distinct or flowering. Second, I focused on graminoids and used Carex (sedges) as a model group to examine how forest structure and morphology affected detection success for this notoriously challenging group. I found that graminoids were not any less likely to be detected in field surveys than other growth-forms, but greater differences between observers were most related to higher ground cover of forbs and short shrubs. Exploring factors that further affect detection for Carex, I found that detection failures were related to local abundance (cover), species morphology, and vegetation cover. In contrast, detection delays of Carex were less related to morphology, suggesting that cryptic species are likely to go unnoticed where they are present, even with careful searching. Third, I examined the relationship between oil and gas footprint and persistence of rare plant populations in northeastern Alberta by revisiting historical populations across a range of footprint types. I found no correlation between the amount of surrounding oil and gas footprint and extirpation of field-visited populations, suggesting either adjacent development poses little threat or there exists an unpaid extinction debt. Fourth, I conducted experimental translocations for two rare peatland species and monitored their growth and survival over three years. I found high survival across different types of recipient sites, suggesting this technique may be quite suitable for many peatland species, especially Sarracenia purpurea. However, poor growth and evidence of stunting in Carex oligosperma stresses the importance of conducting translocation with species whose ecology is well understood. When the niche of a species is poorly understood, use of an experimental approach to translocations with detailed monitoring is needed to assess the efficacy of this practice. Key conservation issues within the oil sands area continue to be a lack of consistency in methodology and public reporting for surveys and mitigation. The experiments conducted for this thesis serve to improve our knowledge around rare plant survey practices, rates of population persistence, mitigative efforts, and more broadly contribute to the development of best practices and guidelines for plant conservation within this rapidly changing region of Canada’s boreal forest.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.