Preliminary evidence of mixed-severity fire regimes in the east slopes of the Rocky Mountains

AMOROSO, MARIANO M.; DANIELS, LORI; BATAINEH, MOHAMMAD; ANDISON, DAVID

Workshop; The Foothills Research Institute Natural Disturbance Program: What do we have for you?; 2009

This study provides new evidence of historic stand-maintainingfires, intermixed with stand-replacing fires, in the Berland River watershed inthe foothills of the Rocky Mountains, Alberta. Stand-replacingfires burned 120 to 300 years ago initiated even-aged cohorts of fast-growinglodgepole pine at each of the six study sites. Evidence of subsequent, stand-maintaining fires included single anddouble fire scars on thin-barked lodgepole pine that were as small as 3.6cm indiameter at the time of the fire but survived. These stand-maintaining firesresulted in structurally complex stands with a broad range of tree diametersand multiple cohorts of lodgepole pine, white and black spruce and subalpinefir.  At the site level, fire returnintervals were variable, ranging from 19 to 167 years, but most were c.20 to 80years.  Of the 11 years in which we documented stand maintaining fires, onlythe fires in 1889 and 1915 scarred trees at more than one site, indicating thatthe stand-maintaining fires were relatively small with local effects.  This new knowledge of historical,stand-maintaining fires provided by this study has important implications forforest management and conservation of biodiversity. Although we recognize that further research needs todetermine the extent of stand-replacing fires and mixed-severity fire regimesat the landscape scale, we discuss the important implications of ourfindings for stand-level management, including harvesting and silviculturalsystems, susceptibility to wildfire and mountain pine beetle, and wildlifehabitat.