Avian community response to understory protection harvesting in the boreal forest of Alberta, Canada

Traditional harvesting in western boreal forests seeks to approximate natural disturbances, such as wildfire. In mixedwood forests, understory conifers such as white spruce are typically destroyed during natural disturbance harvest (NDH). Understory protection (UP) is a harvesting approach that seeks to protect understory conifers during hardwood harvesting in mixedwood forests. While understory protection harvesting has been implemented for over a decade in Alberta, Canada, there has been no assessment of its use by birds. We surveyed birds in UP and NDH harvest blocks, and the nearby unharvested forest, and evaluated differences in species richness and community composition between the three treatment types. We found NDH had significantly higher species richness than unharvested forests, but did not differ from UP. The three treatments all had significantly different avian community compositions, and NDH showed no convergence with the unharvested forest over 15-years post-harvest. However, UP represented an intermediary between NDH and unharvested forests. When comparing the oldest age class of UP with unharvested forest, we found no significant difference in the bird communities 12 years post-harvest. These results suggest that following understory protection harvest, the retained forest regenerates quickly, rapidly providing habitat to more mature forest species than NDH.