Ashley Hillman | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree. This is an ALES PhD Final Exam Seminar by Ashley Hillman. This seminar is open to the general public to attend.

Zoom Link: https://ualberta-ca.zoom.us/j/96829707716

PhD with Dr. Scott Nielsen      

Thesis Topic: Lake-mediated climate buffering in Canada’s western boreal forest

Abstract:

As climate change affects Canada’s boreal forest, cold-adapted plant species face threats from warming temperatures and competition from encroaching species. Climate-change refugia can serve as remnant suitable habitat or as stepping stones for species to disperse in latitude and altitude. Large, deep lakes can act as climate-change refugia, as cold water brought to the surface results in the cooling of shorelines and adjacent forests. Lake Superior serves as a model system for lake-mediated temperature buffering, as its cool water temperatures and wave action have maintained shoreline habitats suitable for disjunct populations of arctic-alpine plants since deglaciation. While lake-mediated cooling is a well-known phenomenon, the degree and extent of temperature buffering at most lakes is unknown. My research seeks to quantify this effect at a network of lakes across the boreal forest region of western Canada, identify environmental factors affecting buffering, and assess the effect on cold-adapted plant species. I first sought to explain the spatial patterns and environmental drivers of disjunct arctic-alpine plant refugia at Lake Superior under current and projected future warming conditions, using known occurrences of disjunct arctic-alpine plants as indicators of refugia. Second, I examined the localized factors driving disjunct plant occurrence, including local site conditions and interspecific competition. Third, I determined geographic patterns and environmental drivers of nearshore and inland buffering at Lake Superior, and identified inland refugia that may resist forest transitions. Finally, I quantified the temperature buffering effects of lakes across western Canada’s boreal forest, using a network of 11 lakes ranging in size, depth, volume, and latitude. I identified seasonal patterns of temperature buffering at all lakes, with implications for growing season length and tree species composition. Knowledge of the extent and magnitude of lake-mediated cooling and drivers of lakeshore refugia at lakes across western boreal Canada may inform regional climate models, as well as guide conservation and management of cold-adapted species and vulnerable habitats under a changing climate.