Fungal community dynamics and growth promoting effects on Leymus chinensis in Leucocalocybe mongolica fairy rings

Leucocalocybe mongolica is an endemic and culturally significant edible mushroom in the temperate grasslands of Inner Mongolia, China, which typically forms conspicuous fairy rings with distinct vegetation zonation. However, its ecological effects on soil fungal communities, nutrient cycling, and plant growth remain poorly understood. In this study, six typical fairy rings were investigated, and high-throughput sequencing was employed to characterize soil fungal communities across the inner area (IA), fruiting area (FA), and outer area (OA). Soil physicochemical properties, enzyme activities, and plant growth promotion assays were integrated to assess their ecological functions. Fungal α-diversity in the fruiting area (FA) was significantly lower than in IA and OA, with Basidiomycota dominated by Leucocalocybe (> 70%). FA soils were more acidic and enriched in ammonium, nitrate, cellulase, and laccase, while IA and OA had higher chitinase, sucrase, and moisture. Network analysis showed FA had the simplest structure dominated by Leucocalocybe, whereas OA exhibited the greatest complexity and stability. Inoculation experiments demonstrated that L. mongolica and its associated fungus Trichoderma harzianum significantly increased plant height, aboveground biomass, photosynthetic rate, and chlorophyll content of Leymus chinensis. These findings indicate that the center of L. mongolica fairy rings functions as a core zone for nitrogen cycling and plant growth promotion, achieving a “high-efficiency center–diverse periphery” spatial organization through reshaping the soil microenvironment and fungal networks. The study provides new perspectives for improving grassland soil fertility and restoring degraded land.