Unraveling spatio‐temporal variability of arbuscular mycorrhiza fungi in a temperate grassland plot

Soils provide a heterogeneous environment varying in space and time; consequently, the biodiversity of soil microorganisms also differs spatially and temporally. For soil microbes tightly associated with plant roots, such as arbuscular mycorrhiza fungi (AMF), the diversity of plant partners and seasonal variability in trophic exchanges between the symbionts introduce additional heterogeneity. To clarify the impact of such heterogeneity, we investigated spatio‐temporal variation in AMF diversity on a plot‐scale (10 × 10 m) in a grassland managed at low intensity in southwest Germany. AMF diversity was determined using 18S rDNA pyrosequencing analysis of 360 soil samples taken at six time points within a year. We observed high AMF alpha‐ and beta‐diversity across the plot and at all investigated time points. Relationships were detected between spatio‐temporal variation in AMF OTU richness and plant species richness, root biomass, minimal changes in soil texture, and pH. The plot was characterized by high AMF turnover rates with a positive spatio‐temporal relationship for AMF beta‐diversity. However, environmental variables explained only ~20% of the variation in AMF communities. This indicates that the observed spatio‐temporal richness and community variability of AMF was largely independent of the abiotic environment, but related to plant properties and the co‐occurring microbiome.