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Wildland fire management has reached a crossroads. Current perspectives are not capable of answering interdisciplinary adaptation and mitigation challenges posed by increases in wildfire risk to human populations and the need to reintegrate fire as a vital landscape process. Fire science has been, and continues to be, performed in isolated "silos," including institutions (e.g., agencies versus universities), organizational structures (e.g., federal agency mandates versus local and state procedures for responding to fire), and research foci (e.g., physical science, natural science, and social science). These silos tend to promote research, management, and policy that focus only on targeted aspects of the "wicked" wildfire problem. In this article, we provide guiding principles to bridge diverse fire science efforts to advance an integrated agenda of wildfire research that can help overcome disciplinary silos and provide insight on how to build fire-resilient communities.

Spruce budworm (Choristoneura fumiferana (Clemens)) defoliation has been shown to increase the likelihood of large forest fires in central Canada. However, the time frame of heightened risk based on the duration of spruce budworm defoliation has not yet been quantified. In this article, we document the extent of stand breakdown and surface fuel accumulation after a period of spruce budworm defoliation that occurred between 1972 and 1976. Data on stand characteristics were derived from previous studies at three different locations in the boreal mixedwood forests of central Canada: Aubinadong (B.J. Stocks. 1987. For. Chron. 63: 8-14), Gogama, and Gowganda in Ontario. Stand breakdown was measured using a series of transects set in plots 7 years following aerially mapped defoliation (1977-1983). Results show that during the 4 years following 5 years of defoliation, crown breakage, a typical symptom of defoliation, increased by nearly 200%, and surface fuel increased by 145% from predisturbance levels. The high correlation between crown breakage and surface fuels linked defoliation to fuel buildup. We begin to solve the challenge of measuring fuel structure over the expansive scale of spruce budworm outbreaks by quantifying the relationship among stand breakdown, time since the end of defoliation, and the duration of defoliation so that the expected fuel structure can be modelled from annual defoliation surveys. Key words: spruce budworm defoliation, crown fire, forest fire management, forest structure, natural disturbance. Il a ete demontre que la defoliation causee par la tordeuse des bourgeons de l'epinette (Choristoneura fumiferana (Clemens)) augmente la probabilite que de vastes feux de foret surviennent dans la partie centrale du Canada. Cependant, la periode de risque accru fondee sur la duree des defoliations causees par la tordeuse des bourgeons de l'epinette n'a pas encore ete quantifiee. Dans cet article, nous documentons l'ampleur de la deterioration des peuplements et de l'accumulation des combustibles de surface a la suite d'une periode de defoliation survenue entre 1972 et 1976. Les donnees sur les caracteristiques des peuplements ont ete extraites d'etudes precedentes realisees a trois endroits differents dans les forets boreales mixtes du centre du Canada : Aubinadong (B.J. Stocks. 1987. For Chron. 63: 8-14), Gogama et Gowganda, en Ontario. La deterioration des peuplements a ete mesuree a l'aide d'une serie de transects etablis dans des parcelles 7 ans apres une defoliation cartographiee par la voie des airs (1977-1983). Les resultats montrent que durant les 4 annees qui ont suivi 5 annees de defoliation le bris des cimes, un symptome typique de defoliation, a augmente de pres de 200% et les combustibles de surface de 145%, relativement aux niveaux existants avant la perturbation. La correlation etroite entre le bris des cimes et les combustibles de surface relie la defoliation a l'accumulation de combustibles. Nous commencons a relever le defi que represente la mesure de la structure des combustibles considerant l'ampleur croissante des epidemies en quantifiant la relation entre la deterioration des peuplements, le temps ecoule depuis que la defoliation a cesse et la duree de la defoliation, de telle sorte que la structure anticipee des combustibles puisse etre modelisee a partir des releves annuels de defoliation. [Traduit par la Redaction] Mots-cles: defoliation causee par la tordeuse des bourgeons de l'epinette, feu de cime, gestion des feux de foret, structure de la foret, perturbation naturelle., Introduction Spruce budworm (Choristoneura fumiferana (Clemens)) outbreaks and forest fire are two important natural disturbances in Canada's boreal forests; however, the relationship between these two ecological drivers has not been [...]

Background. Crown fires are an ecologically necessary but hazardous process in conifer forests. Prediction of their behaviour in Canada has largely depended on the Canadian Forest Fire Behaviour Prediction System, in which fire weather indices drive primarily fixed fuel type models. The Crown Fire Initiation and Spread (CFIS) system presents a more flexible approach to predicting crown fire occurrence than fixed fuel type models. Aims. Using a multi-decadal database of experimental fires carried out in conifer plots (1960–2019, n = 113), our aim was to develop updated models based on the CFIS system approach, fitting crown fire occurrence models to fire environment variables using logistic regression. Methods. We tested alternative fuel moisture estimates and compared various model forms using repeated cross-validation. In two-storeyed stands, crown fire occurrence was defined as the involvement of lower canopy stratum fuels. Key results. Final models based on wind speed, fuel strata gap, litter moisture and surface fuel consumption predicted crowning events correctly in up to 92% of cases in training data (89% in cross-validation). Conclusions and implications. These new models offer improved accuracy and flexibility that will help users assess how competing environmental factors interact under different fuel treatments and wildfire scenarios. [ABSTRACT FROM AUTHOR]

Fire is a major disturbance in the boreal forest, and has been shown to release significant amounts of carbon (C) to the atmosphere through combustion. However, less is known about the effects on ecosystems following fire, which include reduced productivity and changes in decomposition in the decade immediately following the disturbance. In this study, we assessed the impact of fire on net primary productivity (NPP) in the North American boreal forest using a 17-year record of satellite NDVI observations at 8-km spatial resolution together with a light-use efficiency model. We identified 61 fire scars in the satellite observations using digitized fire burn perimeters from a database of large fires. We studied the postfire response of NPP by analyzing the most impacted pixel within each burned area. NPP decreased in the year following the fire by 60-260g CM-2 yr-1 (30-80%). By comparing pre- and postfire observations, we estimated a mean NPP recovery period for boreal forests of about 9 years, with substantial variability among fires. We incorporated this behavior into a carbon cycle model simulation to demonstrate these effects on net ecosystem production. The disturbance resulted in a release of C to the atmosphere during the first 8 years, followed by a small, but long-lived, sink lasting 150 years. Postfire net emissions were three times as large as from a model run without changing NPP. However, only small differences in the C cycle occurred between runs after 8 years due to the rapid recovery of NPP. We conclude by discussing the effects of fire on the long-term continental trends in satellite NDVI observed across boreal North America during the 1980s and 1990s.

Research of forest fires in Canada show that their incidence may be increasing. Studies based on statistics obtained from Canada's boreal forests, extreme fire years are becoming more common, with just 2% to 3% of incidents generating around 98% of total area burned per year. These findings may require reconsideration of intentional burning as a forest management technique.

The seasonal occurrence of human-caused savanna fires in Africa has been determined in greater detail. These fires are important environmentally because they account for at least 1/3 of worldwide gas emissions from the burning of biomass. Data collected by the Defense Meteorological Satellite Program Block 5 satellites in 1986 and 1987 show that the yearly occurrence of fires varies according to month and locality. For instance, north of the equator fires happen most often in January. This knowledge may help improve the management and prevention of these fires.