Bacterial diversity and community structure in native legume root nodules in intact and mining-disturbed Arctic tundra

Mining restoration in Arctic regions is challenging due to harsh environmental conditions with slow natural ecosystem recovery taking decades or even centuries. Identifying native species that can both colonize disturbed areas and contribute to soil development is critical to hasten restoration timelines. Nodules were collected from four native legume species ( Astragalus alpinus Linnaeus, Hedysarum americanum (Michaux ex Pursh) Britton, Oxytropis arctica R. Brown, and Oxytropis maydelliana Trautvetter) observed to be naturally colonizing gravel quarries within a mine footprint near Rankin Inlet, Nunavut, Canada. Samples came from both gravel quarries and adjacent intact tundra . Next-generation sequencing of the 16S and nifH regions was used to characterize the nodule bacterial community composition and diversity. Despite the large differences in soil conditions between gravel substrates and intact tundra, no significant effects of soil environment were found on bacterial community composition within plant nodules. Further, few differences were observed in nodule communities between the plant species. Overall, the study suggests that the microbial propagules necessary for successful nodulation are present in gravel quarries. While restoration efforts involving native legumes may succeed without commercial inoculants, further research is needed to determine whether the rhizobia in these environments can provide sufficient nitrogen to support robust host plant growth.