Past, current, and future fire frequencies in Quebec's commercial forests: implications for the cumulative effects of harvesting and fire on age-class structure and natural disturbance-based management

The past decade has seen an increasing interest in forest management based on historical or natural disturbance dynamics. The rationale is that management that favours landscape compositions and stand structures similar to those found historically should also maintain biodiversity and essential ecological functions. In fire-dominated landscapes, this approach is feasible only if current and future fire frequencies are sufficiently low compared with the preindustrial fire frequency, so a substitution of fire by forest management can occur without elevating the overall frequency of disturbance. We address this question by comparing current and simulated future fire frequency based on 2 x CO2 and 3 x CO2 scenarios to historical reconstructions of fire frequency in the commercial forests of Quebec. For most regions, current and simulated future fire frequencies are lower than the historical fire frequency, suggesting that forest management could potentially be used to maintain or recreate the age-class distribution of fire-dominated preindustrial landscapes. Current even-aged management, however, tends to reduce forest variability by, for example, truncating the natural age-class distribution and eliminating mature and old-growth forests from the landscape. Therefore, in the context of sustainable forest management, silvicultural techniques that retain a spectrum of forest compositions and structures at different scales are necessary to maintain this variability and thereby allow a substitution of fire by harvesting.