Out of sight, out of mind: changes in feather moss phyllosphere structure in mine offsite boreal landscapes

Plant-microbe interactions contribute to biodiversity and ecological services (e.g., nitrogen and carbon cycle) in different forest biomes, including the moss phyllosphere of the boreal forest. Increases in mining activities to satisfy mineral requirements are potential threats to ecosystem services provided by microorganisms of the moss phyllosphere, not only in directly disturbed mining areas, but also in relatively intact offsite landscapes. To improve our understanding of the offsite impacts of mining on microbial communities of the phyllosphere, we sampled Pleurozium schreberi (Brid.) Mitt. (a feather moss species) within 1-km mosaic landscapes containing four forest types (i.e., coniferous, deciduous, mixed forest and open canopy peatland) around six mine sites at different stage of the mining lifecycle in the Canada?s boreal zone. Microbial DNA was recovered from the P. schreberi phyllosphere and characterized by metabarcoding of the bacterial 16S rRNA gene and fungal ITS2 region. Offsite effects of mines on the bacterial and fungal communities of the phyllopshere were detected using this approach. Mining stage and forest type both affected the alpha and beta diversity as well as the relative abundance of individual taxa from both groups of organisms, but unexpectedly their effects did not generally interact. Individual microbial taxa had higher indicator values of offsite effects than community-level diversity indices, and the strongest effects occurred within a 0.2 km distance from operating mines for most taxa. Our results suggest that predicted shifts in forest composition under global change scenarios should not interact with the offsite effects on feather moss phyllosphere in boreal forest. Furthermore, although the influenced area is small near a single mine, the total area could be substantial across the globe. Further studies will be needed to assess how these offsite effects of mining on the phyllosphere structure affect the functioning of boreal ecosystems and to develop appropriate mitigation strategies.