How much boreal lake shoreline is burned by wildfire? Implications for emulating natural disturbance in riparian forest management

Understanding of post-fire residual vegetation patterns is important when shoreline vegetation management aims to emulate natural disturbance (END) patterns. To assess the impacts of fire, lake and lakeshed sizes on the burning pattern of shorelines and lakesheds, we quantified the burned shorelines and post-fire residual vegetation patterns in the lakesheds of 123 lakes of Ontario affected by 26 wildfires between 2005 and 2007. We used ArcGIS and Ontario's Enhanced Forest Resources Inventory (eFRI) GIS data to digitize burn patterns. The lake catchments for all lakes were delineated using ArcGIS via lake, river, and elevation data from the Integrated Hydrology geodatabase (MNRF, 2016). The shorelines of fire impacted lakes were generated from the eFRI polygon feature classes, and the polylines were then split according to the digitized burn pattern polygons by running a geometric intersection with these data. The results of this study show that the percentages of burned shorelines and lakesheds are positively correlated with the size of fire and negatively correlated with the sizes of lake and lakeshed. However, irrespective of the size of fire, lake or lakeshed, shorelines are not left completely unburned, which is contrary to existing practice of retaining fixed-width shoreline buffers. It may imply that under END based management, forest harvesting can be possible up to the shorelines in some areas of the landscapes that are left unharvested under a fixed-width riparian buffer management system. However, areas of strong hydrological connectivity between land and water serve as biogeochemical control points and require protection from disturbance during forest management planning and operations. We suggest that GIS-based models developed based on the hydrological and topographical features associated with the unburned shorelines and lakesheds might be useful to predict shoreline residual forest pattern and facilitate END based shoreline forest management.