Compared to Wildfire, Management Practices Reduced Old-Growth Forest Diversity and Functionality in Primary Boreal Landscapes of Eastern Canada

Abstract

Large primary forest residuals can still be found in boreal landscapes. Their areas are however shrinking rapidly due to anthropogenic activities, in particular industrial-scale forestry. The impacts of logging activities on primary boreal forests may also strongly differ from those of wildfires, the dominant stand-replacing natural disturbance in these forests. Since industrial-scale forestry is driven by economic motives, there is a risk that stands of higher economic value will be primarily harvested, thus threatening habitats, and functions related to these forests. Hence, the objective of this study was to identify the main attributes differentiating burned and logged stands prior to disturbance in boreal forests. The study territory lies in the coniferous and closed-canopy boreal forest in Québec, Canada, where industrial-scale logging and wildfire are the two main stand-replacing disturbances. Based on Québec government inventories of primary forests, we identified 427 transects containing about 5.5 circular field plots/transect that were burned or logged shortly after being surveyed, between 1985 and 2016. Comparative analysis of the main structural and environmental attributes of these transects highlighted the strong divergence in the impact of fire and harvesting on primary boreal forests. Overall, logging activities mainly harvested forests with the highest economic value, while most burned stands were low to moderately productive or recently disturbed. These results raise concerns about the resistance and resilience of remnant primary forests within managed areas, particularly in a context of disturbance amplification due to climate change. Moreover, the majority of the stands studied were old-growth forests, characterized by a high ecological value but also highly threatened by anthropogenic disturbances. A loss in the diversity and functionality of primary forests, and particularly the old-growth forests, therefore adds to the current issues related to these ecosystems. Since 2013, the study area is under ecosystem-based management, which implies that there have been marked changes in forestry practices. Complementary research will be necessary to assess the capacity of ecosystem-based management to address the challenges identified in our study.

Contemporary Wildfires Not More Severe Than Historically: More Fire of All Severities Needed to Sustain and Adapt Western US Dry Forests as Climate Changes

“…Disturbances are recognized as essential natural processes in forests. As shown here, dry forests historically experienced episodic high-severity fires and can recover from these fires [36,37], in many cases better than they can recover from high-severity logging [36]. Natural disturbances can nonetheless be potentially dangerous for people and the built environment.…”

Long-Term Impacts of Forest Management Practices under Climate Change on Structure, Composition, and Fragmentation of the Canadian Boreal Landscape

“…For example, pioneer species that require fire to regenerate were disadvantaged after harvesting compared with species that regenerated in the absence of fire; the result was an alteration of forest composition and successional dynamics because coniferous pioneer species were more dependent on fire than hardwood species [8]. The impact of forest harvesting on boreal landscapes was difficult to predict because it primarily targeted stands of sufficient age and market value following contiguous spatial patterns [4,9,10]. Thus, this disturbance caused important changes in forest structure and composition, decreased and fragmented the area of old-growth forests, and produced a large-scale shift from coniferous to mixed and hardwood stands [8,[10][11][12][13][14].…”

“…The impact of forest harvesting on boreal landscapes was difficult to predict because it primarily targeted stands of sufficient age and market value following contiguous spatial patterns [4,9,10]. Thus, this disturbance caused important changes in forest structure and composition, decreased and fragmented the area of old-growth forests, and produced a large-scale shift from coniferous to mixed and hardwood stands [8,[10][11][12][13][14]. These alterations in composition, structure, and biomass had negative implications for timber supply and value chains [15][16][17].…”

Editorial: Forests of high naturalness as references for management and conservation: Potential and pitfalls

“…The extension of forest management practices over increasingly large areas and the application of silvicultural treatments aimed at increasing the yield of wood products from forests have a major impact on the habitats and ecosystem services (Puettmann et al, 2009;Kuuluvainen and Gauthier, 2018). Boreal forests are an excellent example of these issues: their low productivity makes clearcutting the preferred silvicultural treatment, even in areas where stand-replacing disturbances such as wildfire are rare and old-growth forests are abundant (Östlund et al, 1997;Boucher et al, 2017;Martin et al, 2021). Extensive agglomeration of clearcutting in boreal areas has resulted in significant forest rejuvenation and fragmentation of old-growth forests (Haeussler and Kneeshaw, 2003).…”