Jason Paul
MSc student, Department of Integrative Biology, Wilfrid Laurier University (Supervisors: Jennifer Baltzer and Steve Kokelj)
Thesis Topic: Forest development as a driver of ground ice content in mineral soil permafrost near Yellowknife, NWT
Rapid climate warming has increased thaw rates of permafrost (ground at or below 0°C for two or more years). If thaw occurs where permafrost is ice-rich (i.e., high ground ice content), ground subsidence will ensue proportionately. Subsidence can damage infrastructure, alter landscapes, and affect the well-being of people living in the area; therefore, it is imperative to understand the distribution of ground ice for use in future planning. Permafrost thaw can also lead to the alteration of entire ecosystems by releasing water stored as ice, disrupting groundwater flow pathways, and causing soil disturbances and mass wasting. There has been some work to model the distribution of ground ice in areas of discontinuous permafrost. However, there have been few in situ studies in mineral soils of the boreal forest, which compare the relative importance of the multitude of factors that influence and predict ground ice content.
A field study was conducted to examine the influence of ecological factors on the occurrence of ground ice content of the mineral soil permafrost in the North Slave region of the Northwest Territories. Data were collected at twenty sites to sample the gradient of vegetation development for two main forest types: black spruce, and white spruce/white birch. At each site, topography (hummock size, slope, and elevation), forest structure, and ground vegetation composition was measured. Near-surface permafrost was cored to quantify ground ice present at each site. The objective of this research is to gain a better understanding of the ecological drivers of ground ice in boreal forests with fine-grained mineral soil. Results suggest an increase in permafrost ground ice content for black spruce stands as the forest progresses in its development, with small changes in mineral soil sediment size significantly impacting ground ice content. Stands of the white spruce successional trajectory are much more variable in both ice content and active layer thickness, and are significantly impacted by their soil organic matter content, which may be linked with local drainage conditions.