The effects of surficial deposit-drainage combinations on spatial variations of fire cycles in the boreal forest of eastern Canada

Spatial variations in the fire cycle of a large territory (190 000 km(2)) located in the boreal forest of eastern Canada were assessed using random sampling points. Our main objective was to determine if regions characterised by a large proportion of dry surficial deposit-drainage (SDD) burn more frequently than regions with a smaller proportion. Through a regionalisation of the landscape units, we analysed the effects of SDD on spatial variations of the fire cycle. A discriminant analysis involving the SDD and other physical variables (precipitation, temperature, aridity index, water bodies, elevation and slope) made it possible to identify a combination of variables characterising each region. A considerable variation in fire cycle was observed among the different SDD types (from 144 to 425 years) and between regions (from 90 to 715 years). Through the discriminant analysis, this study suggests that a combination of possible climatic top-down (precipitation R-2 = 0.727, aridity index R-2 = 0.663 and temperature R-2 = 0.574) and bottom-up factors (xeric undifferentiated till R-2 = 0.819 and humid undifferentiated till R-2 = 0.691) could explain this variation at the regional scale. Implications of those results for forest protection against fire and regional development are briefly discussed.