Multiple dimensions of plant diversity predict microbial community composition in grassland soils

Soil microbial communities play important roles in regulating ecosystems, but understanding the factors that shape their composition is challenging, in part because of their high diversity. Plants can influence soil communities through environmental effects and the introduction of organic material through litter and root exudates. This suggests that plant diversity may promote soil microbial diversity, but these patterns may depend on how diversity is measured. Here, we used two multi‐year datasets to examine relationships between plant and microbial (bacterial and archaeal, excluding fungi) communities in managed grasslands. At a management‐relevant scale, we examined both alpha and beta diversity components and described plant diversity through taxonomic, trait, and phylogenetic dimensions. We found consistent relationships between plant and microbial beta diversity, but not alpha diversity. These patterns occurred for taxonomic, trait, and phylogenetic plant diversity, indicating that plant communities sharing many species, or comprising plants with similar trait distributions or evolutionary histories, supported soil communities that also exhibited wide taxonomic overlap. That these patterns occurred over large areas suggests that management strategies focused on landscape‐scale plant diversity have the potential to promote microbe‐driven soil functional diversity in grassland ecosystems. Further studies that focus on finer spatial scales and incorporate fungal diversity may further clarify these relationships and their underlying mechanisms.