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étiquettes: permafrost, vegetation, soil chemistry

Objectif(s): To quantify the relationships between vegetation community composition and structure and near-surface ground ice content.

Description du projet: The primary objective is to quantify the relationships between vegetation community composition and structure and near-surface ground ice content. An improved understanding of ground ice-vegetation interactions could contribute both to the understanding of permafrost ecosystems as well as the more applied geotechnical value afforded by an easily measured surrogate of near surface ground ice conditions. Around Yellowknife there is a patchwork of bedrock outcrops separating discrete lacustrine deposits, and consequently discrete forest stands, which consist of a range of vegetation types. Mature vegetation cover can range from deciduous forest cover of white birch, to mixed stands, to white spruce and/or black spruce dominated forests, with corresponding shifts in the understory community. Sampling will be conducted across these different vegetation types to ensure that the range of ecological communities is captured. Within each discrete forest stand, vegetation plots will be established to determine community composition and structure. To determine forest characteristics, 400m2 plots will be established and woody vegetation with diameter at breast height of 5cm or greater will be identified and measured as per standard permanent sample plot protocols. Four 1m2 ground vegetation plots will be established adjacent to tree plots and the identity and abundance of all vegetation <2m in height determined. At each vegetation plot, the organic layer thickness and the thickness of the active (seasonally thawed) layer will be measured. Soil sampling will consist of the extraction of shallow soil cores (3/site) from the active layer and top 50cm of permafrost using a 2-person, hand-held auger. Core logging in the field will include visual estimates of ice content and sample length for laboratory-based bulk density determination. Soil physical and chemical properties will be characterized in a laboratory facility in Yellowknife. Core sections will be subsampled and dry bulk density, water and ice contents quantified. Soil organic carbon will be estimated by loss on ignition, and soil salinity (conductivity, major ions, pH) will be determined using standard methods. These measurements will allow for relationships between plant community composition and ground ice content to be developed. The research team have had informal discussion with the Yellowknives Dene First Nation and the project will target some key areas of interest for them with respect to permafrost sensitivity (areas along the Dettah road and near, but not on, the Welehdeh site (YK river)). Once their environment committee gets up and running in April or May the research team will meet with them and look to establish outreach opportunities via local YK, Ndilo and Dettah school contacts. The research team have close connections to the government both through collaborators and through the ongoing Partnership between Wilfrid Laurier and the GNWT thereby ensuring rapid communication of findings. By living and working in the Yellowknife area for an extended period, the research team will be regularly engaging community members thereby ensuring regular updates and communication of research findings. At project completion, the team will provide an update of the research in Yellowknife and, if possible, in Behchoko to communicate the findings to the community. All theses, publications, and presentations arising from this work will be shared with communities and government and a plain language document will be developed for communication of findings to community members unable to participate in public presentations. The fieldwork for this study will be conducted from July 1, 2014 to Sept 30, 2014.