Preliminary Evidence of Mixed-Severity Fire Regimes on the East Slopes of the Rocky Mountains of West-Central Alberta

DANIELS, LORI; AMOROSO, M; BATAINEH, M; ANDISON, D

Seattle

Congreso; AAG Annual Meeting; 2011

American Asociation of Geographers (AAG)

The Canadian Rocky mountains include a wide range of different fire regimes ranging from infrequent, high-severity stand-replacing fires in several upper montane and subalpine forests to frequent low-severity fires in valley-bottoms. There is also growing evidence of mixed-severity fire regimes (i.e. infrequent high-severity and frequent low-severity fires) and their significant impact on historic forest structures and dynamics. Yet, our understanding of these fire regimes in some areas is poor. Our research aims to address this knowledge gap by investigating fire history in the Berland River watershed of the Rocky Mountain foothills of west-central Alberta. We sampled six sites for historical reconstruction. Fires scars and increment cores were crossdated to determine fire dates and establishment dates, respectively. Stand-replacing fires burned 120 to 300 years ago initiating even-aged cohorts of fast-growing lodgepole pine at all study sites.  Evidence of subsequent, stand-maintaining fires included single and double fire scars on thin-barked lodgepole. These stand-maintaining fires resulted in structurally complex stands with a broad range of tree diameters and multiple cohorts of lodgepole pine, white and black spruce and subalpine fir.  At the site level, fire return intervals were variable, ranging from 19 to 167 years, but most were c.20 to 80 years. This study provides new evidence of historic stand-maintaining fires, intermixed with stand-replacing fires, in the Berland River watershed in the foothills of the Rocky Mountains, Alberta. This new knowledge of historical, stand-maintaining fires has important implications for forest management and conservation of biodiversity.