Post-Disturbance Stand Dynamics
Alberta-Pacific Forest Industries Inc.
Lead Researcher: 
S. Hanus, Alberta Research Council, Vegreville, Alberta, S. Crites, Consultant, Sunset Beach, Alberta
Little is known regarding the fate of residual trees in harvested stands, limiting the understanding of the ecological and economic impacts of this practice. This long-term study monitors residual material within mixedwood boreal stands following three treatments: structured cutblocks, high intensity burn, and low intensity burn.

The study was conducted within the Alberta-Pacific Forest Industries Inc. Forest Management Agreement (FMA) area in northeastern Alberta. The study monitored residual trees within the first six years following disturbance, and also established research sites for long-term monitoring.

Results indicate that falldown rates were low over the six-year period (17%). Overall, falldown rates were not significantly different between structured cutblocks (17%) and low intensity burn (19%); however, both were significantly higher than falldown in the high intensity burn (12%). Although live aspen and white spruce both had falldown rates of 14%, fallen aspen most often broke along the bole while white spruce were root thrown, resulting in differing ecological legacies. It was found that residuals in the smallest and largest diameter categories had the highest falldown rates, while solitary residuals had a higher rate of falldown than grouped residuals. The study provides relevant information regarding the short-term fate of residual material, and can help managers plan for effective residual material retention over the long-term.