(2019) Cumulative patterns of fire and harvest disturbance: Comparing case studies from Russia and Canada

ABSTRACT: As fires become more frequent due to climate change, and the footprint of timber harvesting continues, the cumulative effects of multiple disturbances will become more prevalent across the boreal forest. While emerging literature highlights the ecological consequences of these interactions, such as threatening biodiversity, watershed health and regeneration, there remains little information on their geographic scale. The purpose of this study is to quantify the cumulative impacts of fire and harvest disturbance in two study regions (Saskatchewan, Canada, and Angara, Russia), including both their additive and compounding effects. Study regions were chosen based on high rates of disturbance from harvest and fire, relative to their respective countries. While data were available for harvest and fire in Saskatchewan, and for harvest in Angara, fire polygons needed to be digitized by hand for Angara. To do so, I used a MODIS burned area product to guide the search for fires, and derived the difference Normalized Burned Ratio from Landsat imagery to trace fire perimeters. Of the total study areas, 8% of Saskatchewan and 22% of Angara were impacted by fire, harvest or both, while 0.26% and 2.67%, respectively, were impacted by successive disturbances between 2001-2017. Harvesting increased the total area disturbed by 26% and the areas successively disturbed by 73% in Saskatchewan, and by 14% and 30%, respectively, in Angara. The compounding impacts of successive disturbances may be mitigated by re-evaluating priority regions for firefighting or reducing the flammability of regenerating stands. However, landscape level approaches will be necessary to address the additive impacts of harvest and fire, such as setting maximum disturbance thresholds.