Effect of tree species and seed origin on climate change trial outcomes in Southern Ontario

Abstract

Under a changing climate, species will need to rapidly adapt to novel conditions at existing locations, migrate to track suitable climate, or risk widespread declines. For sessile, slow-migrating organisms like trees, adaptive capacity is expected to be particularly important for survival. Alternatively, assisted migration has been proposed as a means to help align tree populations with shifting climate habitats. Here we report on the performance of seed sources and species at broadleaf and conifer climate change trials at 10 and 11 years after planting, respectively. The trials were established in southern Ontario – an important transition zone between boreal and temperate ecosystems – and were designed to assess: (1) the assisted migration potential of six broadleaf species (via northward movements of seed sources), and (2) the adaptive capacity of three conifer species (via southward movements of seed sources). Both broadleaf and coniferous seed sources tolerated significant movements while maintaining reasonable growth and survival rates. In fact, several coniferous seed sources exhibited relatively high growth and survival rates despite southward transfers of more than 1000 km (> 5 °C mean annual temperature) – indicating considerable adaptive capacity to climate change in these northern conifer populations. Furthermore, several of the broadleaf species exhibited high levels of growth and survival despite being planted at, or beyond, their current northern range limits – suggesting the potential for modest range expansions via assisted migration. Despite caveats related to the relatively young age of the plantations and deer browsing at the site, these findings help forest managers better understand potential climate change impacts and assisted migration outcomes.