Can tree-rings inform assisted migration? Revisiting provenance trials across Atlantic Canada to compare local adaptation between red spruce populations
As climate niches of most tree species are projected to shift rapidly in the coming decades, forest-assisted migration (FAM) of populations from warmer sites is a promising silvicultural tool to help forests adapt to global changes. However, additional knowledge on species-specific local genetic adaptation and phenotypic plasticity is needed to inform the deployment of FAM in forest management. Here we applied a novel dendroecological approach to a unique network of ten 60 year-old provenance trials covering a large climate gradient in eastern Canada to assess the FAM potential of red spruce, a species unique to the Acadian-Wabanaki forest region projected to decline under climate change. We first controlled for non-climatic growth drivers by applying a Bayesian hierarchical model to individual, annual tree growth records extracted from tree-rings. Nonclimatic variables explained 75.6 % and 92 % (posterior mean Bayesian R2) of tree-level and site-level growth, respectively. Across populations and sites, residual annual growth displayed the strongest correlations with summer climate, with growth declines during warm and dry summer conditions. Keywords: Radial growth; Acadian Forest; Climate sensitivity; Dendroecology; Assisted migration; Heat stress
