|Sponsor:||Alberta-Pacific Forest Industries Inc.|
Object & Deliverables
The primary objective of this project was to determine the rate and pattern of falldown of residual aspen trees and snags, approximately 5 years post-harvest and post-burn, by revisiting sites originally sampled in 1996 and 1997.
Little is known regarding the fate of residual trees in harvested stands, limiting the understanding of the ecological and economic impacts of structure retention. This long-term study monitors residual material within mixedwood boreal stands following three treatments: cutblocks with structure retention; high intensity burn; and low intensity burn. The study was conducted within the Al-Pac Forest Management Agreement (FMA) area in northeastern Alberta. The study monitored residual trees within the first six years following disturbance and established research sites for long-term monitoring.
During the 2000 summer season, sixteen structured cutblocks were sampled ranging in size from 7.9 ha to 51.7 ha for a total sampling area of 384 hectares. Fifteen sites [in three stands] and nine sites [in two stands] were sampled in high intensity and low intensity wildfires, respectively with each site measuring 1 ha (100m x 100 m).
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 the low intensity burn (19%); however, both were significantly higher than falldown rates in the high intensity burn (12%). Although live aspen and white spruce 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; and 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.
The project results are contained in a thirty-four page document entitled “Post Disturbance Stand Dynamics: Falldown of Residual Trees and Snags Following Harvest and Wildfire”, prepared by the Alberta Research Council dated March 2001.