Kevin C. Ryan. (2002). Dynamic interactions between forest structure and fire behavior in boreal ecosystems. Silva Fennica vol. 36 no. 1 article id 548. https://doi.org/10.14214/sf.548

Keywords: boreal forest; disturbance dynamics; stand structure; fire behavior; fire severity

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This paper reviews and synthesizes literature on fire as a disturbance factor in boreal forests. Spatial and temporal variation in the biophysical environment, specifically, vegetative structure, terrain, and weather lead to variations in fire behavior. Changes in slope, aspect, elevation, and soil affect site energy and water budgets and the potential plant community. These terrain features also have a major influence on fire-caused disturbance through their role in determining moisture conditions and flammability of fuels on hourly, seasonal, and successional time-scales. On fine time scales (minutes to hours), changes in weather, specifically wind and relative humidity, significantly affect a fire’s intensity and aboveground effects. Normal seasonal changes in dryness and periodic drought influence fire intensity and severity principally by affecting the depth of burn and belowground effects. On decades-long time scales changes in vegetative structure affect the mass of fuel available for burning and therefore the potential energy that can be released during a fire. The severity of fire varies in time and space depending not only on the biophysical environment, but also on the location on the fire’s perimeter (head vs. flank vs. rear). Spatial and temporal variation in severity within a fire can have long-lasting impacts on the structure and species composition of post-fire communities and the potential for future disturbances. Characteristic temperature histories of ground, surface, and crown fires are used to illustrate variations in fire severity. A soil-heating model is used to illustrate the impact of varying depth of burn on the depth at which various fire effects occur in the soil profile. A conceptual model is presented for the effects of fire severity on fire-plant regeneration interactions. The conceptual model can be used by restoration ecologists to evaluate the differential effects of controlled or prescribed fires and wildfires and to plan and implement fire treatments to conserve biodiversity.

Ryan, USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, P.O. Box 8089, Missoula, Montana 59807, USA E-mail: kryan@fs.fed.us

Category : Discussion article

article id 25031, category Discussion article

Simon Lebel Desrosiers, Nicolas Bélanger, Evelyne Thiffault, Nelson Thiffault. (2025). Climate change and transformation in forest fire regimes: an opportunity for the implementation of assisted migration of tree species in the Canadian boreal forest? Silva Fennica vol. 59 no. 2 article id 25031. https://doi.org/10.14214/sf.25031

Keywords: fire severity; site suitability; post-fire regeneration; climate change adaptation; forest resilience; reforestation strategies; tree migration

Highlights: Increasing fire activity is reshaping post-disturbance landscapes in boreal forests; Post-fire sites offer new opportunities for introducing climate-resilient tree species; Fire can improve or impair site conditions for forest regeneration; Assisted migration of tree species may enhance reforestation success after severe wildfires; Research on post-fire regeneration of introduced species remains critically limited.

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Climate change is intensifying fire regimes in boreal forests, leading to ecological disruption and raising concerns about forest resilience and post-disturbance recovery. Altered fire dynamics creates novel opportunities for implementing adaptive silviculture for climate change, including assisted migration, the intentional movement and establishment of tree species or tree populations outside their current range of distribution to better match anticipated future climates. Here, we examine how the increasing frequency, severity, and spatial extent of Canadian boreal wildfires can serve as strategic windows for introducing climate-resilient tree species and genotypes. We review how fire influences the availability and suitability of post-fire sites for assisted migration, highlighting how fire-induced changes in soil abiotic and biotic properties may facilitate or hinder the establishment of relocated tree species. While fire can simplify site preparation, reduce biotic competition, and temporarily enhance soil nutrient availability, it may also degrade soil structure by consuming or altering soil organic matter and increasing soil susceptibility to erosion and disrupt essential mycorrhizal associations. We argue that assisted migration of tree species can be a proactive silvicultural tool when used in areas with regeneration failure or where future climate conditions are likely to exceed the tolerance limits of native species. Whilst scientific evidence remains limited on the regeneration success of migrated species and genotypes in post-fire environments, we argue for an integrated adaptation strategy that combines natural regeneration with targeted assisted migration interventions, guided by local site conditions, genetic considerations, and policy support, to build resilient boreal forests under changing disturbance regimes.

Lebel Desrosiers, Laboratoire sur la science des données, Université du Québec (TÉLUQ), 5800, rue Saint-Denis, bureau 1105, Montréal, Québec H2S 3L5, Canada https://orcid.org/0009-0007-1592-8505 E-mail: simon.lebeldesrosiers@teluq.ca
Bélanger, Laboratoire sur la science des données, Université du Québec (TÉLUQ), 5800, rue Saint-Denis, bureau 1105, Montréal, Québec H2S 3L5, Canada E-mail: nicolas.belanger@teluq.ca
Thiffault, Centre de recherche sur les matériaux renouvelables, Université Laval, 2425 De la Terrasse St, Québec, Québec G1V 0A6, Canada https://orcid.org/0000-0001-9586-3834 E-mail: evelyne.thiffault@sbf.ulaval.ca
Thiffault, Service canadien des forêts, Ressources naturelles Canada, 1055, rue Du P.E.P.S., C.P. 10380, Québec, Québec G1V 4C7, Canada https://orcid.org/0000-0003-2017-6890 E-mail: nelson.thiffault@canada.ca

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