The forest tent caterpillar (Malacosoma disstria Hbn.) is an eruptive forest insect common across North America and an important defoliator of trembling aspen (Populus tremuloides Michx.). Forest stands having suffered severe defoliations by the forest tent caterpillar over multiple years are known to incur reduced tree growth and increased tree mortality. In this study, we developed a predictive model of forest tent caterpillar defoliation dynamics using local and contextual variables expressing forest composition and structure, and their heterogeneity, at different scales. Of all scales considered (500, 1000, 1500, and 2000 m), contextual variables at 1500 m were found to have the greatest effect on defoliation dynamics. At this scale, we found that a greater proportion of preferred host trees in the landscape increased defoliation severity, but duration was modulated by compositional heterogeneity, where persistence was reduced in highly heterogeneous landscapes. Indeed, the likelihood of a single year of defoliation was much greater in highly diverse landscapes than the likelihood of multiple years of defoliation. These findings are consistent with ecological theory. Contrary to the expected result that older trees would be most susceptible, we found that “middle-aged” trees (~50 years) were most likely to be defoliated.

As evidence points to the importance of climate change (CC) impacts on forests, it is critical to understand how forestry and forest-dependent communities will be affected. People active in the Quebec forest sector were consulted about their perceptions on the most important potential impacts and adaptation measures. Preoccupations covered many aspects of natural ecosystems, forest-based communities, and industries. Expected impacts and adaptation measures were grouped according to biomes and sectors. Prioritized impacts included increases in extreme meteorological events and natural disturbances. Impacts were also expected for human or economic systems such as reductions in wood volume and quality, difficulties in accessing forests, and additional costs for forest operations. Adaptation was perceived to come from new policies, a greater awareness, and local and regional adjustments to forest operations and management. Identified barriers to adaptation included lack of knowledge or understanding of CC impacts, lack of scientific support and knowledge transfer, and lack of leadership in CC issues at a regional scale. This synthesis will help orient future needs in climate-sensitive forest management planning and identify ways to increase adaptive capacity of the forest sector.Keywords: climate change, adaptation measures, impacts, perception, barriers to adaptation, forest management, Quebec, Canada, forest sector RÉSUMÉLes impacts des changements climatiques (CCs) sur la forêt sont déjà observés et iront en s'amplifiant dans le futur. Dans ce contexte, il importe de comprendre comment les communautés et l'industrie forestière seront affectées. Des professionnels du secteur forestier québécois ont été consultés lors d'un atelier afin de recueillir leurs perceptions des impacts potentiels des CCs et des possibles mesures d'adaptation. Les préoccupations touchaient les écosystèmes naturels, ainsi que les collectivités et l'industrie forestière. Les impacts identifiés incluaient l'augmentation des évènements météorologiques extrêmes et des perturbations naturelles, une diminution quantitative et qualitative du bois, ainsi que de plus grandes difficultés d'accès aux territoires et des coûts additionnels pour les opérations. Les mesures d'adaptation pourraient comprendre de nouvelles règlementations, une meilleure sensibilisation aux enjeux, et des ajustements locaux et régionaux dans la gestion et les opérations. Les barrières à l'adaptation identifiées incluaient une faible compréhension des enjeux au niveau des intervenants du milieu forestier, ainsi qu'un manque de soutien scientifique, de transfert des connaissances, et de leadership à l' échelle régionale. Cette synthèse aidera à orienter les besoins en matière de planification et de gestion et à identifier des solutions pour augmenter la capacité d'adaptation du secteur forestier. Mots