Natural disturbances, forest resilience and forest management : the case of the northern limit for forest allocation on Québec in the context of climate change

Sustainable forest management as practiced in Québec involves a timber harvest that does not exceed the capacity of the forest to renew itself over time. In the context of climate change, where the frequency of natural disturbances is expected to increase, it is important to ensure that ecosystem regeneration capacity is sufficient to maintain satisfactory forest density and productivity to support development activities. The issue is all the more pressing at the northern limit for forest management, which is faced with a high frequency of forest fires. It is important to better understand the process of forest regeneration at this northern limit, in order to develop sustainable forest management strategies that will enable the implementation of measures that are both ecologically and economically feasible, taking into account the effects of climate change.

• Evaluate the impact of fire and insect disturbances on forest dynamics on both sides of the present northern limit for commercial forestry activity with regard to past, present and future climate change.

• Introduce and optimize sustainable forest planning and management strategies.

• Reconstruct recent disturbance regimes (fire, insects) south and north of the northern limit.

• Reconstruct the Holocene fire and vegetation history in time and space along a climate gradient to highlight the relationship between climate and fire and assess forest resilience.

• Evaluate the resilience of forests after natural disturbances (fire, insects) and analyze the factors that influence them.

• Model past and future risk of fire, insects and extreme climate events based on climate model simulations.

The work cited below helped to define, on an ecological basis, the northern limit at which sustainable management is possible in Québec and to explore possible constraints related to climate change. The work of Rapanoela et al. (2015) showed that burn rate alone explains 63% of the variation in the proportion of currently productive stands and 41% of the relative difference between percentages of currently and potentially productive stands. The results of Gauthier et al. (2015) indicated that productive stand area generally decreases with decreasing degree-days, increasing elevation or in relation to surficial geology. Their innovative approach made it possible to assess the vulnerability of different sectors to fire (Figure 1). In addition, four criteria specific to the biophysical aspects of sustainable forest management were evaluated in the study of Jobidon et al. (2015): physical environment, timber production capacity, forest vulnerability to fire, and biodiversity conservation. Indicators and acceptability threshold values were determined for each criterion and an analytical method was developed to assess whether a land district has the potential to be sustainably managed. This process made it possible to classify the districts into three categories: slightly sensitive, moderately sensitive and highly sensitive (Figure 2).

Figure 1 : Fire vulnerability at the district level; (A) mean time required to reach double productivity; (B) district vulnerability to fire using a constant probability of burning; and (C) district vulnerability to fire using an increasing probability of burning from 0 to 50 years (Gauthier et al. 2015).

Figure 2 : District types and subtypes according to sensitivity to sustainable forest management. The figure presents 5 sectors: a) northwestern Abitibi, (b) west of Lake Mistassini, (c) north of Saguenay-Lac-Saint-Jean, (d) Middle North Shore, and (e) Lower North Shore (Jobidon et al. 2015). 

• Ministère des forêts, de la faune et des parcs du Québec

• Université du Québec à Chicoutimi (UQAC)

• Université de Montpellier