Soil Chemistry and Microbial Community Patterns Across Tricholoma matsutake Fairy-Ring Developmental Stages in Yeongju, South Korea

This study investigates how shiro developmental stages, soil physicochemical properties, and seasonal variation shape fungal and bacterial communities associated with Tricholoma matsutake in a Pinus densiflora forest in Yeongju, South Korea. Seasonal soil samples from past, present, and future shiro zones were analyzed using ITS and 16S rRNA metabarcoding together with soil chemical measurements. Shiro-driven spatial heterogeneity, rather than seasonality, was the dominant factor structuring microbial communities. Fungal assemblages differed significantly among shiro stages, with exchangeable potassium (K+) emerging as the primary driver and a strong predictor of T. matsutake abundance. Elevated K+ in active shiro zones corresponded to reduced fungal diversity, suggesting competitive exclusion by dominant ectomycorrhizal taxa. In contrast, bacterial communities were shaped mainly by water-soluble iron (Fe), shifting from Acidobacteria-rich assemblages in past zones to Proteobacteria in active zones. The enrichment of siderophore-associated taxa suggests a potential role of Fe acquisition processes, broadly consistent with mechanisms proposed in the mycorrhiza helper bacteria hypothesis, though not directly tested here. Overall, T. matsutake development generates nutrient-specific biogeochemical gradients-K+ for fungi and Fe for bacteria-that reorganize soil microbial communities. These findings underscore tightly linked biotic-abiotic interactions in shiro ecology and highlight microbial and chemical features that may serve as indicators of shiro activity.