Long-term reconstruction of the fire season in the mixedwood boreal forest of Western Canada

Climate modelling studies have predicted an increase in fire frequency with global warming as well as suggesting a longer fire season occurring later in the year. We used 160 years of fire scars in Pinus banksiana Lamb. dating from 1831 to 1948 and written fire records from 1927 to 1995 for Prince Albert National Park in the southern boreal forest to look for evidence of changes in the duration and timing of the fire season (defined as the months when large areas burn) that may have accompanied past changes in fire frequency. The Park's time-since-fire distribution had indicated two such changes: one around 1890 and the other around 1945, both in the direction of decreasing fire frequency. Both fire scars and written fire records indicated that the dominance of the spring fire season (April-June) has remained unchanged over the past 160 years. A small number of scars suggested that the fire season may have extended slightly into the summer (July) prior to 1890 when the fire cycle was much shorter and that the fire season may have shifted to a slightly earlier spring start after 1945 when the fire cycle was much longer.