S. 2002. Natural fi re regime: a guide for sustainable management of the Canadian boreal forest. Silva Fennica 36(1): 81-95.The combination of certain features of fi re disturbance, notably fi re frequency, size and severity, may be used to characterize the disturbance regime in any region of the boreal forest. As some consequences of fi re resemble the effects of industrial forest harvesting, conventional forest management is often considered as a disturbance that has effects similar to those of natural disturbances. Although the analogy between forest management and fi re disturbance in boreal ecosystems has some merit, it is important to recognise that it also has its limitations. Short fi re cycles generally described for boreal ecosystems do not appear to be universal; rather, important spatial and temporal variations have been observed in Canada. These variations in the fi re cycle have an important infl uence on forest composition and structure at the landscape and regional levels. Size and severity of fi res also show a large range of variability. In regions where the natural matrix of the boreal forest remains relatively intact, maintenance of this natural variability should be targeted by forest managers concerned with biodiversity conservation. Current forest management tends to reduce this variability: for example, fully regulated, even-aged management will tend to truncate the natural forest age distribution and eliminate over-mature and old-growth forests from the landscape. We suggest that the development of strategic-level forest management planning approaches and silvicultural techniques designed to maintain a spectrum of forest compositions and structures at different scales in the landscape is one avenue to maintain this variability. Although we use the boreal forest of Quebec for our examples, it is possible to apply the approach to those portions of the boreal forest where the fi re regime favours the development of even-aged stands in burns.

Bird community response to both landscape‐scale and local (forest types) changes in forest cover was studied in three boreal mixed‐wood forest landscapes modified by different types of disturbances: (1) a pre‐industrial landscape where human settlement, agriculture, and logging activities date back to the early 1930s, (2) an industrial timber managed forest, and (3) a forest dominated by natural disturbances. Birds were sampled at 459 sampling stations distributed among the three landscapes. Local habitat and landscape characteristics of the context surrounding each sampling station (500‐m and 1‐km radius) were also computed. Bird communities were influenced by landscape‐scale changes in forest cover. The higher proportion of early‐successional habitats in both human‐disturbed landscapes resulted in significantly higher abundance of early‐successional bird species and generalists. The mean number of mature forest bird species was significantly lower in the industrial and pre‐industrial landscapes than in the natural landscape. Landscape‐scale conversion of mature forests from mixed‐wood to deciduous cover in human‐disturbed landscapes was the main cause of changes in mature forest bird communities. In these landscapes, the abundance of species associated with mixed and coniferous forest cover was lower, whereas species that preferred a deciduous cover were more abundant. Variation in bird community composition determined by the landscape context was as important as local habitat conditions, suggesting that predictions on the regional impact of forest management on songbirds with models solely based on local scale factors could be misleading. Patterns of bird species composition were related to several landscape composition variables (proportions of forest types), but not to configuration variables (e.g., interior habitat, amount of edge). Overall, our results indicated that the large‐scale conversion of the southern portion of the boreal forest from a mixed to a deciduous cover may be one of the most important threats to the integrity of bird communities in these forest mosaics. Negative effects of changes in bird communities could be attenuated if current forestry practices are modified toward maintaining forest types (deciduous, mixed‐wood, and coniferous) at levels similar to those observed under natural disturbances.

No abstract

Although the concept of forest ecosystem management based on Le concept d'arnknagement &yst6mique, soit une approche #am& natural disturbance has generated a great deal of interest, few connagement forestier s'inspirant des perturbations naturelles, suscrete examples exist of FEM principles being put into application.cite de plus en plus d'intkret auprks des forestiers mais son Silvicultural practices that emulate natural disturbances are proapplication concrkte en est encore B ses dkbuts. Des pratiques sylviposed with examples from the principal vegetation zones of coles s'apparentant aux perturbations naturelles sont proposkes Quebec. With the exception of the large-scale use of careful en donnant des exemples pour les principales zones de vCg6ta-logging to protect advanced regeneration in ecosystems generally tion du Qukbec. A l'exception de l'utilisation 2i grande Cchelle de controlled by fire, stand-level silvicultural practices currently used la coupe avec protection de la rkg6nkration et des sols dans des are reasonably similar to natural disturbances, although impor6cosystkmes gknkrdement cont18lCs par les incendies, les pratiques tant differences exist. In contrast, at the forest-level, even-aged ~y l v i c~l e s rkalistes couramment B l'kchelle des ~e u~l e m e n t s management, as is currently rarely adequate sont assez similaires aux perturbations naturelles, bien qu'il duction of the variety of age ,-lasses, stand types, and structural existe encore des diffkrences importantes. Par contre, l'amkcomponents d y found in the boreal forest. A model that allows nagement normal des for& kquiennes, tel que pratiquk actuellean even-aged management approach inspired by natural dynamment, Permet rarement de reproduire adkquatement la varikt6 des ics is proposed.classes d'$ges, des types de peuplements et des composantes structurales habituellement rencontrks en for& boreale. Un modkle permettant d'appliquer une approche d'amknagement Cquienne s'inspirant de la nature est proposk.

Balsam fir (Abiesbalsamea (L.) Mill.) mortality caused by the last spruce budworm (Choristoneurafumiferana (Clem.)) outbreak (1970–1987) was studied in 624 sites belonging to a complex natural forest mosaic originating from different fires in northwestern Quebec. Multiple regression analyses were used to assess the respective effects of stand structure, species composition, site characteristics, and the forest composition surrounding the stand on observed stand mortality. Mortality was observed to increase in relation to diameter of the trees, basal area of balsam fir, and the number of stands dominated by conifers in the forest mosaic. All of these factors showed significant independent effects, but 60% of the variance remained unexplained. Site characteristics, however, did not show a significant relationship to stand mortality. The results suggest that forest composition at both the stand and the forest mosaic levels may be responsible for differing degrees of defoliation that result in differences in stand mortality. Forest management strategies that favor the presence of mixed compositions both at the stand level and at the mosaic level may contribute to decreased stand vulnerability.