Mycorrhizal fungal spore community structure in a manipulated prairie

Most plant communities support a diverse assemblage of arbuscular mycorrhizal fungi (AMF). AMF communities have the potential to affect plant community structure and vice versa. We examined AMF sporulation in a 4.5-ha reconstructed prairie in Eau Claire County, Wisconsin. In fall 2003, the site was planted with varied numbers and combinations of native prairie species from four functional guilds: C₃ grasses/sedges, C₄ grasses, legume, and nonleguminous forbs. We hypothesized that more diverse plant seeding mixtures would promote AMF diversity. To examine the interaction between plant and fungal communities, plots were divided and subplots treated with the fungicide chlorothalonil to suppress AMF, enriched with ammonium nitrate fertilizer, treated with both fungicide and nitrogen, or remained untreated (control). Soil samples were collected during the summers of 2004, 2006, and 2007 from each subplot. Spores of AMF were extracted, identified to species, and enumerated. Initial plant seeding diversity did not significantly influence spore abundance, fungal diversity, plant productivity, or plant richness 4 years after establishment. Fungal species richness was positively, but weakly, correlated with plant productivity (r² = 0.11) and plant richness (r² = 0.09). Fungal community composition changed significantly over time; nitrogen addition, fungicide application, and site characteristics also shaped community composition. After 4 years of treatment, nitrogen and fungicide reduced AMF richness, changed sporulation patterns among AMF taxa, and reduced diversity and productivity in plant communities. Divergence in AMF community is being mirrored by changes in the plant community independent of initial seeding treatments, though causation could not be determined.