SPATIAL AND TEMPORAL VARIATIONS IN BOREAL FOREST-FIRE FREQUENCY IN NORTHERN ALBERTA

Spatial and temporal variations in fire frequency in the boreal forest of Wood Buffalo National Park (WBNP) were assessed using forest stand age, fire scar and historical data. I test the hypotheses that (1) fi re frequency is higher in jack pine forests and aspen forests than in black spruce forests and white spruce forests, (2) these variations in fire frequency can be related to the mean waterbreak distance (MWD) a round a site and (3) fire frequency has changed over the past 300 year s. The fire cycles (the time required to burn an area equal in size to the entire study area) in jack pine forests (39 years) and in aspen f orests (39 years) were significantly shorter than those in black spruc e forests (78 years) and in white spruce forests (96 years). The lengt h of the fire cycle varies inversely with the MWD around a site, and t he MWD was significantly higher in jack pine and aspen forests than in black or white spruce forests. It is suggested that covariations betw een soil type and the MWD influence, respectively, variations in fores t dominant and fire frequency. A change in fire frequency at 1860 was apparent in the fire history for all of WBNP, the black spruce dominat ed stands, and the near and medium MWD classes. The fire cycle estimat es for these classes were all significantly shorter during the period 1750 to 1859 (fire cycles=25-49 years) than they were in the period 18 60 to 1989 (fire cycles=59-89 years). The possible roles of changes in climate and aboriginal burning practices in causing the temporal chan ge in fire frequency are discussed.