Distinct roles of prokaryotes and fungi in belowground networks and predicting plant diversity and productivity in a North American grassland

Interactions among plants and belowground microbes form complex networks that underpin ecosystem functions, yet the specific roles of prokaryotes and fungi and their links to plant diversity and productivity remain unclear. In a North American grassland, we examined biomass, diversity, and community composition across four communities-plants, root fungi, soil fungi, and soil prokaryotes-along a water-driven edaphic gradient. Drier habitats had lower plant biomass but higher diversity and more complex belowground networks. All communities, except soil fungi, varied significantly across habitats, producing distinct network structures. Bacterial biomass was more strongly correlated with plant biomass than fungal biomass, and bacterial families had greater predictive power for plant productivity. However, many keystone taxa with high network degrees and betweenness were fungi, and the proportion of fungal network hubs increased in wetter habitats. Core fungal families such as Glomeraceae and Herpotrichiellaceae consistently showed high richness and degree across habitats, while core prokaryotic families differed between wet and dry sites, suggesting more localized roles. These findings enhance our understanding of the relationships between the biomass and diversity of plants and belowground microbial communities, highlighting the importance of distinguishing microbial functional roles to better understand belowground ecological processes.