Emulating natural disturbances: the role of silviculture in creating even-aged and complex structures in the black spruce boreal forest of eastern North America

Abstract

Ecosystem-based forest management is based on the principle of emulating regional natural disturbance regimes with forest management. An interesting area for a case study of the potential of ecosystem-based forest management is the boreal forest of north-western Québec and north-eastern Ontario, where the disturbance regime creates a mosaic of stands with both complex and simple structures. Old-growth stands of this region have multistoried, open structures, thick soil organic layers, and are unproductive, while young post-fire stands established following severe fires that consumed most of the organic soil show dense and even-sized/aged structures and are more productive. Current forest management emulates the effects of low severity fires, which only partially consume the organic layers, and could lead to unproductive even-aged stands. The natural disturbance and forest management regimes differ in such a way that both young productive and old-growth forests could ultimately be under-represented on the landscape under a fully regulated forest management regime. Two major challenges for ecosystem-based forest management of this region are thus to: (1) maintain complex structures associated with old-growth forests, and (2) promote the establishment of productive post-harvest stands, while at the same time maintaining harvested volume. We discuss different silvicultural approaches that offer solutions to these challenges, namely the use of (1) partial harvesting to create or maintain complex structures typical of old-growth stands, and (2) site preparation techniques to emulate severe soil burns and create productive post-harvest stands. A similar approach could be applied to any region where the natural disturbance regime creates a landscape where both even-aged stands established after stand-replacing disturbances and irregular old-growth stands created by smaller scale disturbances are significant.

Landscape composition influences local pattern of fire size in the eastern Canadian boreal forest: role of weather and landscape mosaic on fire size distribution in mixedwood boreal forest using the Prescribed Fire Analysis System

“…More particularly, harvest rotations inspired by the natural fire regime, such as fire frequency and fire cycle, would better respect the natural distribution of forest stands in the landscape mosaic in terms of composition and proportion (Bergeron et al 2002;Fenton et al 2009). The present study aims to analyse the effect of the landscape mosaic composition on fire propagation by evaluating fire size distribution for different mosaic compositions under different weather conditions from fire ignition to extinction.…”

Ecosystem management in paludified boreal forests: enhancing wood production, biodiversity, and carbon sequestration at the landscape level

“…High-severity soil burns convert these stands to first cohort stands, whereas low-severity soil burns, by not completely consuming the organic layer (gray area under the stands), create low-productivity forests that are structurally similar to third-cohort stands. Modified from Lecomte et al (2006a), Simard et al (2009), andFenton et al (2009) 2015). Since each of these species are associated with specific stand structures, community composition is greatly influenced by soil burn severity and time elapsed since fire (Bergeron and Fenton 2012;Boudreault et al 2009;Paradis and Work 2011;Fenton and Bergeron 2013;Doblas-Miranda and Work 2015).…”

“…Over the years it appeared that where organic layer is > 30 cm thick, careful logging was suspected to favor paludification and to reduce black spruce forest productivity (Fenton et al 2005;Lavoie et al 2005b). Reports of declining productivity following careful logging initiated an important research program focusing on the effects of silvicultural treatments on stand productivity for sites prone to paludification with the aim of identifying silvicultural treatments most likely to control paludification and maintain forest productivity Fenton et al 2009). …”

“…Achieving these two goals however is challenging, at least at the stand scale. For example, biodiversity protection involves maintaining forest structures that are often associated to old forests, which have the additional benefit of storing large amounts of carbon in their organic soils (Fenton et al 2009). Old forests however are increasingly rare in managed landscapes.…”

“…Old forests however are increasingly rare in managed landscapes. Maintaining the abundance of old forests can be achieved through full conservation of old-growth forests but also by using partial cutting, a silvicultural practice that is however susceptible to reduce productivity on paludified sites (Fenton et al 2009). Nevertheless, reporting on the fifteen-year results of uneven-aged management in forested peatlands, Groot (2013) observed and increase in basal area with time indicating that partial cutting can maintain stands which structure is suitable for the implementation of uneven-aged silviculture through the use of partial cutting.…”