Pannonian sand grasslands represent a prominent nature conservation value, for the maintenance of which knowledge of appropriate grassland management practices is indispensable. Our research investigated the complex effects of a phenomenon known as fairy rings – specifically, rings formed by Agaricus xanthodermus – which transform both the soil and the vegetation. In the different zones of a 14 m diameter fairy ring, we performed detailed botanical surveys using a total of 288 quadrats, each 0.5 m×0. 5m in area. These were evaluated using Borhidi's ecological indicators and the Balázs method for estimating yield and fodder value.
The fairy ring exerts a dual, spatially distinct effect on the vegetation. Intensive nitrogen mobilisation occurred at the fungal front, leading to the rapid dominance of the nitrogen-demanding, ruderal species Elymus repens. The characteristics of this zone included a steep increase in total cover, a drastic decrease in diversity, and a decline in the vegetation's naturalness value. Moving inwards from the ring, the effect weakened; regeneration was taking place, where the fodder-valuable Poa angustifolia dominated, resulting in the highest fodder value (K-value) in the central part of the ring. However, diversity remained low here as well, due to monodominance.
In summary, it can be concluded that the A. xanthodermus fairy ring functions as an ecosystem engineer, generating significant spatial heterogeneity in the grassland. Based on our results, a comprehensive assessment of the effects of fairy rings is essential to develop sustainable management and conservation practices for Pannonian grasslands, with particular regard to the balance between forage production and biodiversity.