Canadian Forest Service Publications

Topographic and fire weather controls of fire refugia in forested ecosystems of northwestern North America. 2016. Krawchuk. M.A.; Haire, S.L.; Coop. J.; Parisien, M.-A.; Whitman, E.; Chong, G.; Miller, C. Ecosphere 7(12):e01632.

Year: 2016

Issued by: Northern Forestry Centre

Catalog ID: 37791

Language: English

Availability: PDF (download)

Available from the Journal's Web site.
DOI: 10.1002/ecs2.1632

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Fire refugia, sometimes referred to as fire islands, shadows, skips, residuals, or fire remnants, are an important element of the burn mosaic, but we lack a quantitative framework that links observations of fire refugia from different environmental contexts. Here, we develop and test a conceptual model for how predictability of fire refugia varies according to topographic complexity and fire weather conditions. Refugia were quantified as areas unburned or burned at comparatively low severity based on remotely sensed burn severity data. We assessed the relationship between refugia and a suite of terrain-related explanatory metrics by fitting a collection of boosted regression tree models. The models were developed for seven study fires that burned in conifer-dominated forested landscapes of the Western Cordillera of Canada between 2001 and 2014. We fit nine models, each for distinct levels of fire weather and terrain ruggedness. Our framework revealed that the predictability and abundance of fire refugia varied among these environmental settings. We observed highest predictability under moderate fire weather conditions and moderate terrain ruggedness (ROC-AUC = 0.77), and lowest predictability in flatter landscapes and under high fire weather conditions (ROC-AUC = 0.63–0.68). Catchment slope, local aspect, relative position, topographic wetness, topographic convergence, and local slope all contributed to discriminating where refugia occur but the relative importance of these topographic controls differed among environments. Our framework allows us to characterize the predictability of contemporary fire refugia across multiple environmental settings and provides important insights for ecosystem resilience, wildfire management, conservation planning, and climate change adaptation.

Plain Language Summary

During wildfires, areas that experience little or no fire can provide habitat for fire-sensitive animals and plants and can help them to survive and repopulate the forest after the fire. These “fire refugia” are important in understanding how ecosystems survive and thrive and in planning wildlife management and conservation, as well as in adapting to climate change. Refugia have previously been studied, but this study tried to establish a framework to predict which areas would be refugia, based on how flat or rugged the landscape is, and on the fire weather conditions. It looked at aspects of seven recent wildfires in the Western Cordillera ecoregion of western Canada. The resulting framework showed that whether you can predict locations of fire refugia depends on the ruggedness of the terrain and on fire weather conditions. The locations of refugia can be fairly well predicted in most landscapes and weather conditions, except when the terrain is flat or when the fire weather is severe (hot and dry). Identifying these locations can allow them to be left as “islands” during forest harvesting or when clearing flammable vegetation for wildlife management. Creating and preserving these refugia can help forests recover after a fire.