The effects of high temperatures on seedling survival for seven major conifer species of the Acadian Forest of eastern Canada

Abstract The Acadian Forest Region is a unique transitional ecotone in northeastern North America where temperate and boreal forests converge. It is comprised of ~32 tree species, many of which are currently situated at either the extreme northern or southern extent of their climatic range. At these ranges, some species are expected to be substantially affected by climate change, particularly during the more vulnerable regeneration stage of forest stand development. In this study we examined the effects of climate warming on the performance and survival of seven conifer species native to the Acadian Forest Region. To do so, 840 tree seedlings were grown in phytotrons under 12 different temperature treatments over one growing season. At the end of the treatment, heat-induced foliar damage and seedling survival was recorded. The results revealed a strong correlation between seedling damage and increasing temperature, particularly in colder-adapted boreal species. White pine (Pinus strobus L.), a temperate conifer, exhibited strong resilience to even the highest temperatures, while balsam fir (Abies balsamea (L.) Mill), a cold adapted boreal species, experienced the highest rate of mortality. Overall, we found colder-adapted boreal conifers suffered greater seedling mortality under warming relative to temperate species. Results from this study may be used to improve the parameterization of forest simulation models to support adaptive forest management policies and decision making.