PS 40-112 - Disentangling the core microbiome of Miscanthus x giganteus

Abstract: Microorganisms associate closely with plants at the root-soil interface (i.e., the rhizosphere). When specific microbial taxa are reliably detected in the rhizosphere across sites, they are considered part of the plant’s ‘core microbiome’. The core microbiome is actively and dynamically recruited by belowground plant inputs (namely, root exudates). Miscanthus x giganteus, an important candidate crop for bioenergy production, relies on microbial partners to aid its establishment and productivity and may be particularly effective at recruiting its core microbiome. This may explain why Miscanthus can remain productive even under the highly variable, harsh conditions present on disturbed lands, like those impacted by mineral extraction. Nevertheless, the composition and function of the Miscanthus core microbiome remain relatively unexplored. As such, this study aims to define and characterize the core microbiome of Miscanthus. We hypothesize if Miscanthus is recruiting a core microbiome to promote function, bacterial and fungal communities should be distinct from nearby soils associated with other plants. Additionally, we expect the structure and function of the core microbiome will be more evident as the magnitude of plant influence increases with Miscanthus stand age. Eight Miscanthus stands ranging from 3-10 years old were selected to test the above hypotheses. Soil samples were taken from the rhizosphere of Miscanthus and adjacent cool-season grasses and analyzed for chemical properties and microbial community dynamics (composition and function). We have observed increased plant height and biomass yield associated with increasing Miscanthus stand age. Soil nitrate concentrations are higher in cool season grassland soils on younger sites with an inverse relationship shown in older sites. Soil ammonia concentrations were higher in Miscanthus soils compared to adjacent cool-season grass soils, especially on the youngest sites. Microbial biomass carbon is higher in Miscanthus soils compared to adjacent grassland soils regardless of stand age. Going forward, we predict increased free-living nitrogen fixation rates and soil organic matter in Miscanthus soils. We aim to connect these function trends with shifts in microbial community composition. These findings would suggest that Miscanthus dynamically shapes its core microbiome over time as age stands. Our results will contribute to a working knowledge of how Miscanthus alters soil biological and chemical properties to remain productive and sustainable under changing environmental conditions. This knowledge contributes to the goal of understanding nutrient cycling dynamics in agricultural systems and facilitating a sustainable transition to renewable energy sources.