Mycorrhizal and Rhizosphere Community Characterization in Tundra Plants

Background/Question/Methods

As the North American Arctic warms, plant communities are shifting from sedge-dominated to shrub-dominated in a process known as shrubification. The change in vegetation is associated with shifts in belowground microbial ecology such as mycorrhizal colonization and rhizosphere community composition. Tundra plants contain distinct mycorrhizal and rhizosphere community structures, but little is known about the variation in communities between different tundra plants species, or variation among plants of the same species. Moreover, the extent to which mycorrhizal fungi shapes rhizosphere community structures is unexplored. To understand mycorrhizal and rhizosphere community variation between and within tundra plants we used amplicon sequencing of the ribosomal region (ITS for fungi, 16S for bacteria). Since most tundra plants are generalists that harbor many different species of ectomycorrhizal symbionts, we hypothesized that within-plant species variation of mycorrhizal fungi would be equal to the between-plant variation. We also hypothesized that mycorrhizal fungal composition would be the primary driver of rhizosphere community composition, followed by plant species and edaphic properties. Our samples were collected in the North Slope of Alaska in August 2021. They spanned four different glacial ages presumed to vary in edaphic properties and were collected in moist acidic and non-acidic sites.

Results/Conclusions

Our preliminary results show distinct groupings of bacteria and fungal species matrices upon NMDS ordinations. Bacterial rhizosphere and fungal communities appear to group strongest by individual plant, followed by plant species and edaphic properties. Mycorrhizal variation appears to be larger than predicted between different plant species and lower than predicted within plants of the same species. A mantel test will be employed to compare our mycorrhizal species matrix to rhizosphere species matrices of the same plants to determine if a correlation exists. A partial least squares regression will follow up to quantify the extent to which mycorrhizal fungi shape rhizosphere community structures. The link between mycorrhizal and rhizosphere communities may serve as a valuable predictor for belowground ecological changes brought on by shrubification and could have implications for biogeochemical functions such as decomposition and carbon sequestration.