Mitigating post-fire regeneration failure in boreal landscapes with reforestation and variable retention harvesting: At what cost?

Abstract

Successive disturbances such as fire can affect post-disturbance regeneration density, with documented adverse effects on subsequent stand productivity. We conducted a simulation study to assess the potential of reactive (reforestation) and proactive (variable retention harvesting) post-fire regeneration failure mitigation strategies in a 1.37-Mha fire-prone boreal landscape dominated by black spruce and jack pine. We quantified their respective capacity to maintain landscape productivity and post-fire resilience, as well as their associated financial returns under current and projected (RCP 8.5) fire regimes. While post-fire reforestation with jack pine revealed to be the most effective strategy to maintain potential production, associated costs quickly became prohibitive when applied over extensive areas. Proactive strategies such as an extensive use of variable retention harvesting, combined with replanting of fire-adapted jack pine only in easily accessible areas, appeared as a more promising approach. Despite this, our results suggest an inevitable erosion of forest productivity due to post-fire regeneration failure events, highlighting the importance to integrate fire a priori in strategic forest management planning as well as its effects on long-term regeneration dynamics.

Factors influencing black spruce reproductive potential in the northern boreal forest of Quebec

“…Black spruce stands exhibiting limited reproductive potential are at greater risk of natural regeneration failure following fire and may result in the fragmentation of continuous forest cover, leading to changes in successional patterns and forest composition, and a potential shift from closedcrown forest to open lichen woodland (Sirois and Payette 1989;Sirois and Payette 1991;Girard et al 2008Girard et al , 2009Côté et al 2013;Splawinski et al 2019aSplawinski et al , 2019cBaltzer et al 2021;Cyr et al 2021). Projections of a more frequent and intense fire regime under climate change (Flannigan et al 2005(Flannigan et al , 2009(Flannigan et al , 2013Bergeron et al 2010;Boulanger et al 2014) will make both young and over-mature stands even more vulnerable to regeneration failure, although vegetation feedbacks may dampen the effect (Boulanger et al 2017).…”

“…The species can therefore be extirpated from stands affected by short fire intervals (Keeley et al 1999;Johnstone and Chapin 2006;Johnstone et al 2010a;Brown and Johnstone 2012;Pinno et al 2013). Given this sensitivity to both a short fire return interval and an increase in fire intensity in the context of climate warming, black spruce is vulnerable to regeneration failure following fires, as shown by comparative (e.g., Johnstone and Chapin 2006;Baltzer et al 2021) and modelling studies (Splawinski et al 2019a(Splawinski et al , 2019cCyr et al 2021). This process has the potential to decrease forest resilience and stand productivity over time.…”

“…A better understanding of the reproductive ecology and life history traits of black spruce in northern cold forests will improve modelling and forecasting of regeneration and succession in the context of global changes in climate and associated disturbance regimes, environmental stressors, and forest management. These forcing stressors (climate warming, fire, insect epidemic, harvest) have the capacity to induce regeneration failure and productivity loss, thereby leading to a decline in forest resilience and cover over time (Simard and Payette 2005;Splawinski et al 2019a;Baltzer et al 2021;Cyr et al 2021). Such knowledge will prove particularly useful in the development of sustainable forest management, restoration, and adaptive strategies aimed at minimizing or reversing such changes (Raulier et al 2013;Gauthier et al 2014Gauthier et al , 2015aGauthier et al , 2015bSplawinski et al 2019aSplawinski et al , 2019cCyr et al 2021).…”

“…These forcing stressors (climate warming, fire, insect epidemic, harvest) have the capacity to induce regeneration failure and productivity loss, thereby leading to a decline in forest resilience and cover over time (Simard and Payette 2005;Splawinski et al 2019a;Baltzer et al 2021;Cyr et al 2021). Such knowledge will prove particularly useful in the development of sustainable forest management, restoration, and adaptive strategies aimed at minimizing or reversing such changes (Raulier et al 2013;Gauthier et al 2014Gauthier et al , 2015aGauthier et al , 2015bSplawinski et al 2019aSplawinski et al , 2019cCyr et al 2021).…”

Forecasting wildfire-induced declines in potential forest harvest levels across Québec

“…Wildfires have an important influence on forest management activities. In the short term, fire suppression is expensive (Stocks and Martell 2016), as are post-fire silvicultural interventions to restore or maintain forest productivity (Cyr et al 2022a). In the long term, wildfires also cause decreases in sustainable harvest rates (Van Wagner 1983;Boychuk and Martell 1996) and may exert great pressure on other ecosystem services such as carbon sequestration (Colombo et al 2012).…”