Mycorrhizal Communities and Their Effect on Tree Growth at a Post-Mining Site

Abstract Purpose Primary succession of vegetation in post-mining areas offers an opportunity to study how plant species and individuals interact in space and notably how biotic interactions such as mycorrhizal symbiosis contribute to the revegetalization of degraded environments. Our study aimed to characterize the taxonomical and spatial structure of mycorrhizal communities and determine how mycorrhizae affect seedling growth at a post-mining site. Methods Mycorrhizal fungal communities were identified from fine roots of tree seedlings in a mine tailings site in Quebec, Canada. We used next-generation DNA sequencing to determine mycorrhizal richness and abundance, and analyzed patterns of species sharing based on host plant species or distance. The influence of neighbourhood competition, mycorrhizal communities and soil nutrients on seedling growth were characterized. Results Fungal DNA was amplified from 40% of plant samples, and 474 fungal operational taxonomic units (OTUs) were identified. Ectomycorrhizae were shared among all host species with no significant host specificity but were segregated at the scale of individual plants. The site was characterized by extremely low soil nitrogen and phosphorus concentrations and high arsenic levels. Growth of most host plants was not affected by neighbourhood competition, soil nitrogen, shoot biomass, mycorrhizal richness, mycorrhizal abundance, or sharing of mycorrhizae. Conclusion We found that plant-plant interactions, mycorrhizal networks and soil nutrients were not important factors determining plant growth at this site due to strong nutrient limitations and high As contamination. Considering the low specificity and low access to mycorrhizae in degraded environments, revegetalization projects could introduce mycorrhizae to boost seedling growth.