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

Author: mycolabadmin
4/1/2025
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Summary

Fairy rings created by the mushroom Agaricus urinascens dramatically transform Mediterranean grasslands. These fungal rings create zones of dead plants and altered soil conditions, killing vegetation and reducing plant species diversity by 40% at the fungal front. The fungi coat their mycelium with calcium oxalate crystals and create water-repellent soil conditions that essentially drown plants by preventing water absorption, ultimately favoring fast-growing grasses over diverse wildflower communities.

Background

Fungal fairy rings (FFRs) significantly influence plant communities and soil microbiota in grassland ecosystems. This study investigated the development of Agaricus urinascens fairy rings in a species-rich montane Mediterranean grassland by integrating vegetation analysis, soil chemistry, and molecular microbiome techniques. The research aimed to understand how FFRs function as ecosystem engineers affecting multiple ecosystem components simultaneously.

Objective

To assess the mechanisms and impacts of A. urinascens fairy rings on soil properties, plant communities, and microbial composition in a montane Mediterranean grassland. The study combined vegetation surveys, soil chemical analyses, next-generation sequencing of bacterial and fungal communities, and SEM-EDS analysis of fungal mycelium structure to provide comprehensive understanding of FFRs as ecosystem engineers.

Results

At the FF, plant biomass decreased slightly while increasing threefold in the belt zone. Species richness dropped 40% at the FF. Soil properties showed dramatic changes: phosphorus increased 534%, electrical conductivity rose 210%, and hydrophobicity increased 36% at the FF compared to external grassland. Clay content tripled at the FF. Bacterial diversity declined at FF with Actinobacteria dominating (85%), while fungal diversity was lowest inside the ring. SEM-EDS revealed calcium oxalate crystals exclusively on mycelium at the FF, potentially enhancing hydrophobicity and contributing to plant mortality.

Conclusion

Agaricus urinascens fairy rings function as ecosystem engineers, fundamentally reshaping soil chemistry, plant community composition, and microbial diversity in Mediterranean grasslands. The fungal-driven transformation is mediated by increased soil hydrophobicity, nutrient alterations, and calcium oxalate crystal formation on mycelium, which collectively reduce plant biodiversity and favor fast-growing grasses over long-lived perennials. These findings demonstrate that FFRs create complex ecological trade-offs between nutrient cycling benefits and significant plant mortality through hydrophobic soil conditions.

Published in:FEMS Microbiology Ecology,
Study Type:Field Study,
Source: PMID: 40169382, DOI: 10.1093/femsec/fiaf034