Fire is a major disturbance in Canadian forests. Along with fuel and ignition characteristics, climatic conditions are seen as one of the main drivers of fire regimes. Projected changes in climate are expected to significantly influence fire regimes in Canada. As fire regime greatly shapes large-scale patterns in biodiversity, carbon, and vegetation, as well as forest and fire management strategies, it becomes necessary to define regions where current and future fire regimes are homogeneous. Random Forests (RF) modeling was used to relate fire regime attributes prevailing between 1961 and 1990 in eastern Canada with climatic/fire-weather and environmental variables. Using climatic normals outputs from the Canadian Regional Climate Model (CRCM), we delineated current (1961–1990) and future (2011–2040, 2040–2070, 2071–2100) homogeneous fire regime (HFR) zones. Heterogeneous response of fire regime to climate changes is projected for eastern Canada with some areas (e.g., western Quebec) experiencing very small alterations while others (e.g., southeastern Ontario) are facing great shifts. Overall, models predicted a 2.2- and 2.4-fold increase in the number of fires and the annual area burned respectively mostly as a result of an increase in extreme fire-weather normals and mean drought code. As extreme fire danger would occur later in the fire season on average, the fire season would shift slightly later (5–20 days) in the summer for much of the study area while remaining relatively stable elsewhere. Although fire regime values would change significantly over time, most zone boundaries would remain relatively stable. The information resulting from HFR zonations is clearly of interest for forest and fire management agencies as it reveals zones with peculiar fire regimes that would have been hidden otherwise using predefined administrative or ecological stratifications. Read More: http://www.esajournals.org/doi/abs/10.1890/12-0698.1

Over the past decades, there has been an increasing interest in the development of forest management approaches that are based on an understanding of historical natural disturbance dynamics. The rationale for such an approach is that management to favor landscape compositions and stand structures similar to those of natural ecosystems should also maintain biological diversity and essential ecological functions. In fire-dominated landscapes, this approach is possible only if current and future fire frequencies are sufficiently low, comparing to pre-industrial fire frequency, that we can substitute fire by forest management. We address this question by comparing current and future fire frequency to historical reconstruction of fire frequency from studies realized in the Canadian boreal forest. Current and simulated future fire frequencies using 2 and 3 x CO2 scenarios are lower than the historical fire frequency for many sites, suggesting that forest management could potentially be used to recreate the forest age structure of fire-controlled pre-industrial landscapes. There are however, important limitations to the current even-age management.

The forest fire regime was characterized for the boreal forest of western Quebec using the provincial government's digital databases (1945-1998). Lightning- and human-caused fires account for 71% and 29% of the total area burned, respectively. With regard to ignition sources, lightning was responsible for 38% of the fires while humans were the ignition agent for 62% of fires. The fire regime parameters (burn rate, fire occurrence, and size) were subjected to a stepwise regression analysis on the basis of regional landscape units. Models indicate that climatic factors, particularly summer precipitation and maximum temperatures, play a primary role in forest fire dynamics, regardless of the ignition source. Fire occurrence models were the most predictable with R-2 values of 0.79 and 0.60 for lightning fires and human-caused fires, respectively. Models of burned areas reached an R-2 value of 0.63 for lightning but only 0.22 for human-caused fires; on the other hand, the fire-size model for human-caused fires showed an R-2 value of 0.57 but only 0.24 for lightning fires. In the case of human-induced fires, the density of the road network and sand deposits were important in fire occurrence and burned areas models. Once characterized, landscape units tend to group together naturally, forming extensive areas in which the fire regime is relatively homogeneous. The results of the regionalization based on lightning fire regimes are discussed from the standpoint of sustainable forest management.

The fire history of two adjacent regions of the boreal forest, one characterized by fogging (Ontario-510,000 ha) and the other by small scale agricultural activities (Quebec-140,000 ha), was studied before and after these regions were opened up to settlement in 1916. From a review of provincial forest fire records and the assessment of the age of fire-initiated forest stands, it appears that large but rare fires occurred during the presettlement period on both sides of the border. After 1916, due to slash and burn activities, the agricultural region (Que) had proportionally about twice the burned areas and ten times more fires than the forestry region (Ont). Despite differences in population density, road network, and land use, fire size class occurrence did not differ between landscapes overtime. However,the occurrence of fires larger than 100 ha, considering three development phases (1916-1939; 1940-1969; 1970-1998), decreased in both regions from settlement to the present, particularly during the late phase (1970-1998) in the agricultural region. An analysis of fluctuations in the Canadian forest Fire Weather Index system (FWI), a rating of fire danger severity, showed major climatic stresses at the beginning of the century (1916-1924), followed by a decrease in the occurrence of extreme FWI values. Combined with the impact of climate, which affected the annual area burned and the number of large fires in both landscapes, the results suggest that the landscape fragmentation, the increase in the percentage of deciduous trees overtime and/or effective fire detection by residents led to a decrease in the number of fires larger than 100 ha on the agricultural side for the late phase (1970-1998).

A review of the scientific literature relevant to the Claybelt region was undertaken under the initiative of Lake Abitibi Model Forest (LAMF) and in collaboration with the Canadian Forest Service, the Ontario and Quebec Ministries of Natural Resources and the NSERC-UQAT-UQAM (Natural Sciences and Engineering Research Council - Universite du Quebec en Abitibi-Temiscamingue Universite du Quebec A Montreal) Industrial Chair in Sustainable forest Management. The objective was to synthesize this information in order to develop better forestry practices and identify knowledge and research gaps. Forestry-related knowledge was gathered on six broad topics: i) natural disturbances, ii) forest ecosystems, iii) past and present forest practices, iv) biological diversity, v) forest management and vi) examples of current applications of natural disturbance-based forest management. The work allowed us to synthesize a large body of knowledge into one publication that will be a useful reference for foresters in both provinces.

Given that fire is the most important disturbance of the boreal forest, climatically induced changes in fire frequency (i.e., area burnt per year) can have important consequences on the resulting forest mosaic age-class distribution and composition. Using archives and dendroecological data we reconstructed the fire frequency in four large sectors along a transect from eastern Ontario to central Quebec. Results showed a dramatic decrease in fire frequency that began in the mid-19th century and has been accentuated during the 20th century. Although all areas showed a similar temporal decrease in area burned, we observed a gradual increase in fire frequency from the west to Abitibi east, followed by a slight decrease in central Quebec. The global warming that has been occurring since the end of the Little Ice Age (similar to 1850) may have created a climate less prone to large forest fires in the eastern boreal forest of North America. This interpretation is corroborated by predictions of a decrease in forest fires for that region of the boreal forest in the future. A longer fire cycle (i.e., the time needed to burn an area equivalent to the study area) has important consequences for sustainable forest management of the boreal forest of eastern Canada. When considering the important proportion of overmature and old-growth stands in the landscape resulting from the elongation of the fire cycles, it becomes difficult to justify clear-cutting practices over all the entire area as well as short rotations as a means to emulate natural disturbances. Alternative practices involving the uses of variable proportion of clear, partial, and selective cutting are discussed. ©2001 NRC Canada

Afin de déterminer l'influence respective du climat et de la colonisation des territoires abitibiens sur les régimes de feux, nous avons procédé à une reconstitution historique des incendies de forêt. Celle-ci s'étend sur 235 ans ce qui nous a permis d'étudier les fluctuations précoloniales et coloniales du régime de feux. En période coloniale, l'impact de l'homme blanc a été étudié à deux niveaux; nous avons comparé le régime de feux d'un secteur agricole (Québec) de 130 000 ha versus un secteur adjacent de 500 000 ha voué à l'exploitation forestière (Ontario).

Les résultats indiquent que les deux territoires présentent un régime de feux où les aires incendiées décroissent depuis 1760 pour s'accentuer avec la fin du Petit Age Glaciaire vers 1850. Quant à l'occurrence de feux, elle semble demeurer relativement stable dans le temps.

Par ailleurs, l'influence humaine a été principalement analysée à deux niveaux: l'occurrence des feux et les aires incendiées. L'analyse utilisant des modèles mixtes fait clairement ressortir qu'il y a un effet significatif du type d'utilisation du paysage sur le régime de feux. Le secteur agricole a connu 7 fois plus de feux et près du double des aires incendiées que le secteur forestier, soit 28 400 ha contre 51 000 ha par 100 000 ha de territoire. Les modèles mixtes révèlent également que l'occurrence de feux et les aires incendiées varient selon la période d'évolution technologique et le mois de la saison de feux.

L'homme est la source d'ignition principale peu importe le type d'utilisation du territoire. Cependant, les feux d'origine humaine comptent pour 42% des aires incendiées dans le secteur agricole contre 12% dans le secteur forestier. D'autre part, la taille moyenne des incendies de forêt du paysage ontarien est plus grande que celle de l'Abitibi québécoise. Enfin, si les deux premières décennies du siècle ont expérimenté de très grands feux de forêt (>30 000 ha), il appert que les grands événements de feux sont pratiquement inexistants depuis 70 ans.

Les fluctuations du régime de feux s'expliqueraient par une diminution à long terme du danger d'incendie. Par ailleurs, l'impact de l'homme sur le régime de feux se définit principalement par des activités de défrichage utilisant le feu alors que la suppression active, le morcellement des territoires et la transformation des peuplements forestiers n'y auraient qu'une faible influence. © 1998 UQAM tous droits réservés.