In this study we used dendrochronology to reconstruct the history of eastern spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks over the last 450 years in the Bas-Saint-Laurent region of southeastern Quebec. In total, 260 tree cores were sampled from 204 beams in seven historic buildings and 12 trees in a virgin forest stand. Eight previously documented outbreaks (1975–1992, 1947–1958, 1914–1923, 1868–1882, 1832–1845, 1805–1812, 1752–1776, 1710–1724) and three presumed previous outbreaks (1678–1690, 1642–1648, 1577–1600) were identified based on periods of growth reduction. Of these 11 confirmed or presumed outbreaks, six were documented for the first time in eastern Quebec. Such data suggest that outbreak frequency has remained quite stable, with a mean interval of about 40 years between the midpoint of successive outbreaks since the mid-16th century. In addition, together with previous studies, our results indicate a strong spatial synchrony of spruce budworm outbreaks across central and eastern Quebec during the last 300 years. Consequently, our study does not support the hypothesis that spruce budworm outbreak frequency and synchrony increased during the 20th century.

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The ability of national and multipurpose ecological classification systems to provide an optimal zonation for a fire regime is questionable. Using wildfire (.1 ha) point data for the 1980-99 period, we defined zones with a homogeneous fire regime (HFR) across Canada and we assessed how these differ from the National Ecological Framework for Canada (NEFC) units of corresponding scale, i.e. ecoprovinces. Two HFR zonations were produced through spatially constrained clustering of (i) 1600-km 2 cells and (ii) the smallest units of the NEFC system, i.e. ecodistricts, using attributes for natural and anthropogenic fires. Thirty-three HFR zones were identified. HFR zonations showed smaller differences among each other than with NEFC ecoprovinces. Comparisons with ecoprovinces suggested general agreement of generalised fire regime values with HFR zones but with poor zone boundary correspondence. Ecoprovince zonation led to an overgeneralisation of fire regime estimates with less variation captured than by the HFR zonations, especially that using gridded fixed-area cells. Estimates of fire-return interval strongly differed between a priori and HFR zonations. The use of large-scale NEFC units or a zonation using its smallest units may constrain our ability to accurately quantify and portray fire regime variability across the country. The alternative empirical HFR zonation using gridded cells refines the location and nature of fire risk.