The interplay of biotic and abiotic factors shapes tree seedling growth and root-associated microbial communities

Root-associated microbial communities can alleviate plant abiotic stresses, thus potentially supporting adaptation to a changing climate during range expansion. While climate change is extending plant species fundamental niches northward, the distribution and colonization of mutualists (e.g., arbuscular mycorrhizal fungi) and pathogens may constrain plant growth and regeneration. Yet, the degree to which biotic and abiotic factors impact plant performance and associated microbial communities at the edge of their distribution remains unclear. In this study, we used a combination of root microscopy and amplicon sequencing to characterize tree root microbial communities (soil and root mycorrhizae, bacteria, and fungi) of sugar maple seedlings. We also explored the affect of abiotic and biotic factors on root microbial communities and their relationship with seedling growth along two elevation gradients in Quebec, Canada.