Questions: What climate variables best explain fire occurrence and area burned in the Great Lakes-St Lawrence forest of Canada? How will climate change influence these climate variables and thereby affect the occurrence of fire and area burned in a deciduous forest landscape in Témiscamingue, Québec, Canada?

Location: West central Québec and the Great Lakes-St Lawrence forest of Canada.

Methods: We first used an information-theoretic framework to evaluate the relative role of different weather variables in explaining occurrence and area burned of large fires (>200 ha, 1959-1999) across the Great Lakes-St Lawrence forest region. Second, we examined how these weather variables varied historically in Témiscamingue and, third, how they may change between the present and 2100 according to different scenarios of climate change based on two Global Circulation Models.

Results: Mean monthly temperature maxima during the fire season (Apr-Oct) and weighted sequences of dry spells best explained fire occurrence and area burned. Between 1910 and 2004, mean monthly temperature maxima in Témiscamingue showed no apparent temporal trend, while dry spell sequences decreased in frequency and length. All future scenarios show an increase in mean monthly temperature maxima, and one model scenario forecasts an increase in dry spell sequences, resulting in a slight increase in forecasted annual area burned.

Conclusion: Despite the forecasted increase in fire activity, effects of climate change on fire will not likely affect forest structure and composition as much as natural succession or harvesting and other disturbances, principally because of the large relative difference in area affected by these processes.

Le premier article était : « How is ecological resilience relevant for natural disturbance-based forest management? ». Les autres auteurs étaient : Garry Peterson, Christian Messier, Yves Bergeron, et Mike Flannigan. Cet article a été publié en 2006 dans le Revue Canadienne de Recherche Forestière (volume 36, pages 2285- 2299).

Le deuxième article était : « Fire and canopy species composition in the Great Lakes-St. Lawrence forest of Témiscamingue, Québec ». Les autres auteurs étaient : Christian Messier, Yves Bergeron, et Frédérik Doyon. Cet article a été publié en 2006 dans le revue Forest Ecology and Management (volume 231, pages 27-37).

Le troisième article était : « Fire and the relative roles of weather, climate and landscape characteristics in the Great Lakes-St. Lawrence forest of Canada ». Les autres auteurs étaient : Mark C. Drever, Christian Messier, Yves Bergeron, et Mike Flannigan. Cet article a été accepté en mai 2007 par la revue Journal of Vegetation Science.

Le quatrième et dernier article était : « Effects of climate change on fire for a deciduous forest landscape in Témiscamingue, Québec ». Les autres auteurs étaient : Mark C. Drever, Christian Messier, Yves Bergeron, et Mike Flannigan. Cet article a été soumis au journal Applied Vegetation Science. © 2007 UQAM tous droits réservés.

Abstract: The past decade has seen an increasing interest in forest management based on historical or natural disturbance dynamics. The rationale is that management that favours landscape compositions and stand structures similar to those found historically should also maintain biodiversity and essential ecological functions. In fire-dominated landscapes, this approach is feasible only if current and future fire frequencies are sufficiently low compared with the preindustrial fire frequency, so a substitution of fire by forest management can occur without elevating the overall frequency of disturbance. We address this question by comparing current and simulated future fire frequency based on 2 × CO2 and 3 × CO2 scenarios to historical reconstructions of fire frequency in the commercial forests of Quebec. For most regions, current and simulated future fire frequencies are lower than the historical fire frequency, suggesting that forest management could potentially be used to maintain or recreate the age-class distribution of fire-dominated preindustrial landscapes. Current even-aged management, however, tends to reduce forest variability by, for example, truncating the natural age-class distribution and eliminating mature and old-growth forests from the landscape. Therefore, in the context of sustainable forest management, silvicultural techniques that retain a spectrum of forest compositions and structures at different scales are necessary to maintain this variability and thereby allow a substitution of fire by harvesting.

Résumé :Au cours de la dernière décennie, un intérêt grandissant pour le développement d'approches d'aménagement basées sur notre compréhension de la dynamique historique des perturbations naturelles s'est manifesté. Ces approches reposent sur l'idée qu'un aménagement favorisant une composition des paysages et une structure des peuplements similaires à celles créées dans les forêts passées devrait aussi maintenir la diversité biologique et les fonctions écologiques essentielles de ces mêmes paysages et peuplements. Dans les paysages contrôlés par les feux, cette approche est possible seulement si les fréquences de feux actuelles et futures sont suffisamment faibles lorsque comparées aux fréquences pré-industrielles, cela afin de permettre de substituer le feu par la coupe forestière. Nous évaluons cette possibilité en comparant les fréquences de feux actuelles et futures aux fréquences historiques à partir d'études réalisées dans la forêt commerciale québécoise. Les fréquences actuelles et futures des feux, simulées en utilisant deux scénarios de concentration de CO2 (2× et 3× la concentration actuelle), sont plus faibles que les fréquences passées pour la majorité du territoire, suggérant que l'aménagement forestier pourrait potentiellement être utilisé afin de recréer la structure d'âge de la forêt soumise à un régime de feux sévères. Les aménagements équiennes actuels tendent toutefois à réduire la variabilité naturelle du système: par exemple, un aménagement équienne amputera, à terme, la structure d'âge de la forêt naturelle éliminant ainsi les forêts surannées et anciennes du paysage. Le développement de techniques de sylviculture permettant le maintien d'un spectre de compositions et structures forestières à différentes échelles de paysage est une des avenues proposées afin de maintenir cette variabilité. ©2006 NRC Canada

Large severe fires are typically rare in the northern hardwood forests of eastern North America, with estimated return intervals as high as 1400–4500 years. We investigated the history of large severe fires in western Québec, Canada, where sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britt.), and eastern hemlock ((Tsuga canadensis (L.) Carr.) dominate a landscape at northern limit of the Great Lakes-St. Lawrence forest region. Using a combination of provincial archives of fire data, interpretation of historic air photos and dendrochronological sampling, we estimated fire frequency in a 179,300 ha landscape and tested the hypothesis that time-since-fire is a principal determinant of canopy species composition. Our results indicated that despite its proximity to the boreal mixedwood forest, fires have been relatively infrequent in this landscape, with over 60% of the landscape remaining unburned during the 413 year period of study. The overall fire cycle, an estimate of the time required to burn an area of equivalent size to the study area, was 494 year (95% CI: 373–694). This estimate showed strong temporal partitioning, with an elevated frequency that coincided with the period of pioneering settlement beginning in 1880, and spatial partitioning according to surficial deposits, pine dominance and ecological site type. Multivariate analyses elucidated both (i) distinct assemblages of canopy species that differed in their association with time-since-fire and (ii) the relative importance of environmental variables affecting canopy species composition, where time-since-fire explained the largest amount of variation. This time-since-fire effect suggested an important role for secondary disturbances in influencing composition of the canopy. Given the current long fire cycles, it is likely this landscape will experience an increasing dominance of fire-avoiding species such as sugar maple and eastern hemlock, with consequences for fire-adapted tree species and fire-dependent communities. © 2006 Elsevier B.V. All rights reserved.

This paper synthesizes elements of the theory and application of ecological resilience. It has three components. The first is a review of relevant literature concerning ecological resilience, with a focus on the work of ecologist Buzz Holling and his colleagues. Here, ecological resilience is a measure of the persistence of systems and of their capacity to absorb change and disturbance while maintaining the same structuring relationships between populations or state variables. The second component is an article critique of Peterson, G. D. 2002. Estimating resilience across landscapes. Cons. Ecol. 6(1): 17. [online] URL: http://www.consecol.org/vol6/iss1/art17. This article deals with the measurement of resilience across a longleaf pine-dominated landscape in Florida where fire plays a key role in determining forest composition and structure and transition between stable states. I summarize the objectives, methods and results of the article as well as discuss the article’s major strengths and weaknesses, including both general and specific comments on content and style. Third, I propose an experimental protocol designed to deal with issues raised by Peterson, in particular how structure and compositional diversity of component species relate to the notion that areas of cross-scale edge, a measure of resilience defined by Peterson, have low resilience. I conclude with reflections on how to effectively integrate ecological resilience into the sustainable management of resources. © 2004 UQAM tous droits réservés.