Héloïse Le Goff

Fire regime zonation under current and future climate over eastern Canada

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.

Historical fire regime shifts related to climate teleconnections in the Waswanipi area, central Quebec, Canada

The synchrony of regional fire regime shifts across the Quebec boreal forest, eastern Canada, suggests that regional fire regimes are influenced by large-scale climate variability. The present study investigated the relationship of the forest-age distribution, reflecting the regional fire activity, to large-scale climate variations. The interdecadal variation in forest fire activity in the Waswanipi area, north-eastern Canada, was reconstructed over 1720–2000. Next, the 1880–2000 reconstructed fire activity was analysed using different proxies of the Pacific Decadal Oscillation (PDO) and the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO). We estimated the global fire cycle around 132–153 years, with a major lengthening of the fire cycle from 99 years before 1940, to 282 years after 1940. Correlations between decadal fire activity and climate indices indicated a positive influence of the PDO. The positive influence of PDO on regional fire activity was also validated using t-tests between fire years and non-fire years between 1899 and 1996. Our results confirmed recent findings on the positive influence of the PDO on the fire activity over northern Quebec and the reinforcing role of the NAO in this relationship.

Dendroclimatic inference of wildfire activity in Quebec over the 20th century and implications for natural disturbance-based forest management at the northern limit of the commercial forest

We examined the fire–climate relationship at the northern limit of commercial forest in western Quebec, a region where forest management is currently competing with fires for mature stands. The main objective was to determine if a particular climate signal would control the fire activity in this region when compared with other parts of the Quebec boreal forest. We used 500-hPa spatial correlation maps to compare the atmospheric patterns associated with the annual area burned (AAB) in the study area, the entire province of Quebec, the intensive (southern Quebec), and the restricted (northern Quebec) fire management zones. Next, dendroclimatic analyses were used to obtain tree-ring estimates of the AAB back to 1904 and to investigate the temporal stability of the fire–climate relationship. The climate controls associated with the AAB of the study area are intermediate between those associated with the AAB of the intensive and restricted fire management zones. The 500-hPa correlation patterns for the 1948–71 and 1972–2001 periods were relatively stable through time for the study area and for the restricted fire management zone. Our results provide a plausible mechanism for explaining the link between sea surface temperature and regional fire activity established in previous studies. They also provide information complementary to the Canadian fire danger rating system that uses daily weather data.