Could microbes be the architects of improved soil structure under Miscanthus x giganteus?

Miscanthus x giganteus is a perennial grass promoted as a sustainable biomass feedstock, with prior evidence that it improves soil structure, including water-holding capacity and aggregate stability. However, the relative contributions of soil-plant-microbe interactions to these improvements were not well understood. In this study, researchers characterized soil bacterial and arbuscular mycorrhizal fungal (AMF) communities across three sites in Iowa, USA, comparing miscanthus to annual maize (Zea mays L.) and non-cropped perennial turfgrass (Poa spp.). The goal was to determine whether microbiomes co-varied with soil aggregation and whether plant cover identity or life history categorization better explained observed patterns.

Bacterial and AMF communities varied across sites and plant types, with signals that both life history and plant cover identity mattered. Aggregate stability aligned with a perennial-annual divergence in microbial beta diversity, while finer-scale differences in community composition and network structure were plant-specific. Soils under perennial plants were enriched in microbial groups positively correlated with aggregate stability; the study identified 61 bacterial and 8 AMF 'architect' taxa for future research. Within- and cross-kingdom co-occurrence network analysis revealed greater complexity under perennial plants, including 1.9-fold more network links in miscanthus bacteria-bacteria networks than in maize and 1.7-fold more in turfgrass AMF-AMF networks.

These results indicate that miscanthus fundamentally shapes microbial interactions—particularly among bacteria—in ways that relate to improved soil physical structure. Understanding these soil-plant-microbe feedbacks could aid in developing biomass feedstocks with a portfolio of soil health benefits for next-generation biofuels and bioproducts.