| Summary: | Graduate Rapid climate change is driving increases in tundra vegetation productivity and altering the frequency and severity of natural disturbances across the Arctic. While tundra vegetation change has been widespread, there is still uncertainty about the influence of fine-scale factors on change and the role of interactions between warming, disturbance, and vegetation change. In my MSc research I investigated how Arctic tundra vegetation is responding to ongoing climate change and more severe tundra fire in the western Canadian Arctic. In the first part of my thesis I measured post-fire soil and vegetation recovery along a burn severity gradient at six fires, which burned in 2012 in the Northwest Territories. My observations suggest that deciduous shrub communities (dominated by Betula glandulosa) are resilient to high severity fire and that severe fire promotes edaphic conditions that favor the persistence of this vegetation type. In the second part of my thesis, I investigated the spatial patterns of trends in tundra vegetation productivity over the past three decades using Random Forests machine learning to analyze Enhanced Vegetation Index (EVI) data derived from Landsat imagery. My Random Forests models of the relationship between Landsat EVI trends and biophysical variables showed that two-thirds of the western Canadian Arctic productivity has increased during the past three decades and that this change is occurring most rapidly in dwarf and upright shrub-dominated regions. Taken together, my research demonstrates that shrub tundra communities are well adapted to severe fire and show increasing productivity in response to warming Arctic temperature. My research also indicates that these relationships can be highly complex at finer scales, where they are mediated by local variations in microclimate, topography, and moisture.
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