Analyzing risk of regeneration failure in the managed boreal forest of northwestern Quebec

Changes in the fire regime can affect the postdisturbance regeneration potential of boreal forest tree species, thereby modifying tree density and cover. This could adversely affect the sustainability of forest management, especially in regions currently characterized by a short fire cycle and low productivity. As a case study, we use a real landscape (1.3 Mha) in the boreal forest of northwestern Quebec, characterized by a high annual area burned and where fire activity is projected to strongly increase, to model the effect of current (baseline) and climate-induced (projected) changes in the fire cycle and harvesting rate on the regeneration failure potential of pure black spruce (Picea mariana (Mill.) BSP) and jack pine (Pinus banksiana Lamb.) stands. Simulations were carried out over a 50-year period under three reproductive maturity thresholds per species, representing the age at which an adequate seed supply is attained to ensure self-replacement. Results show a progressive increase in the area affected by natural regeneration failure over the course of the simulation period under both climate scenarios, culminating with an 18.5% loss (149 210 ha) of productive area under the baseline scenario and a 65.8% loss (532 141 ha) under the projected scenario (intermediate maturity threshold and current harvest rate). Variation in the fire cycle had the greatest effect on the regeneration failure rate, followed by regeneration threshold age and harvest rate. We outline proactive forest management practices to reduce the likelihood of regeneration failure following fire. This includes intensive stand management and retention strategies following timber harvest. Monitoring of forest recovery after fire would help in assessment of regeneration failure over time and be useful in validating both model results and the efficacy of strategies aimed at minimizing its likelihood.