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Mechanisms and impacts of Agaricus urinascens fairy rings on plant diversity and microbial communities in a montane Mediterranean grassland

Summary

Fairy ring fungi create circular patterns in grasslands by forming dense underground networks that dramatically change soil properties and plant communities. The study found that these fungal rings reduce plant diversity by 40% at their advancing edge while boosting grass growth inside the ring, creating a stark ecological shift. The fungi produce calcium oxalate crystals that make soil very water-repellent, causing nearby plants to dry out and die. This research shows how a single fungus species can reshape entire ecosystems through physical and chemical changes in the soil.

Background

Fungal fairy rings (FFRs) significantly influence plant communities and soil microbiota in grassland ecosystems. While their impact on soil chemistry is well-established, comprehensive understanding of their simultaneous effects on vegetation, soil properties, and microbial communities remains limited. This study investigated FFRs formed by Agaricus urinascens in a species-rich montane Mediterranean grassland.

Objective

To assess the mechanisms and impacts of A. urinascens fairy rings on plant diversity, soil properties, and microbial communities by integrating vegetation analysis, soil chemistry measurements, and next-generation sequencing. The study aimed to characterize how fungal mycelium structures and their elemental composition contribute to ecosystem engineering effects.

Results

At the fungal front (FF), plant biomass decreased slightly but increased over threefold inside the ring, favoring grasses over forbs. Species richness dropped 40% at the FF, with significant soil alterations including 534% increase in phosphorus, 210% rise in electrical conductivity, and 36% increase in soil hydrophobicity. Microbial diversity shifted markedly, with Actinobacteria dominating at the FF (85%) and Ascomycota reaching 97%, while calcium oxalate crystals were uniquely present on mycelium at the fungal front.

Conclusion

Fairy ring fungi act as ecosystem engineers, reshaping soil properties, plant communities, and microbial composition through hydrophobicity and structural modifications. The presence of calcium oxalate crystals at the fungal front represents a novel mechanism potentially enhancing pathogenicity and hydrophobicity. These findings demonstrate that FFRs significantly reduce biodiversity while favoring fast-growing grass species over long-lived perennials in Mediterranean grasslands.
  • Published in:FEMS Microbiology Ecology,
  • Study Type:Field Study,
  • Source: PMID: 40169382, DOI: 10.1093/femsec/fiaf034
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