Temporal dynamics of ectomycorrhizal fungi: Leaf habit and exploration strategy explain seasonal variation in community abundance and composition

Ectomycorrhizal (EcM) fungi are well-recognized symbionts impacting tree health and ecosystem functioning globally, yet understanding of their timing of proliferation in soils across seasons and years remains limited. We analyzed monthly patterns of EcM fungal abundance and community structure over two years in five temperate monodominant forest plots via quantitative PCR and Illumina sequencing. We found that the phenological dynamics of EcM fungi differed significantly by host tree leaf habit, fungal exploration type, fungal genus, and soil moisture. Overall, total EcM fungal abundances based on qPCR consistently peaked in autumn, and were more dynamic in evergreen than deciduous plots, supporting ideas of surplus carbon and asymmetric above-belowground dynamics. Longer-distance exploration types peaked earlier and were more stable than shorter-distance types, suggesting an independent and supportive role in releasing spring nutrients. About half of 20 focal taxa consistently peaked in either autumn, summer, or spring, while others were either host- and/or year-dependent. Our findings highlight that phenology is a key EcM fungal trait best explained by both host and fungal contributions, and future studies across biomes should consider seasonal shifts and sampling to elucidate phenological traits. Summary - The timing of belowground production and seasonal community dynamics remain poorly understood for ectomycorrhizal (EcM) fungi. - We collected soils monthly for two years from five temperate monodominant forest plots. - Fungal production peaked in autumn, shorter-distance and evergreen-associated spanned wider ranges, and half of focal fungal genera showed seasonal preference, emphasizing autumn surplus carbon and spring nutrients from long-distance types. - Future studies should consider seasonal shifts when sampling EcM fungal communities, and forest carbon models should include asymmetric above-belowground phenology. Translated Summary (Spanish) - La fenología de la producción y composición de comunidades de hongos ectomicorrízicos (EcM) es poco estudiada. - Recolectamos suelos mensualmente por dos años de cinco parcelas mono-dominantes templados. - Producción máxima de hongos ocurrió en otoño, hongos asociados con árboles siempreverdes y de exploración de corta-distancia observaron rangos más amplios, y la mitad de géneros de hongos focales observaron preferencia estacional, enfatizando extra carbono en otoño y nutrientes en primavera de tipos larga-distancia. - Estudios deben considerar cambios estacionales para el muestreo de hongos EcM, y modelos de carbono deben incluir fenología asimétrica entre hojas y hongos. Plain language summary Ectomycorrhizal fungi are critical for the global carbon cycle, but their seasonal and inter-annual growth patterns remain unclear. We sample soil DNA monthly over two years across five different monodominant temperate forest stands. We find an overall belowground peak in autumn, with significantly later growth under wetter conditions, more dynamism with evergreen trees, and distinct spring growth by longer-distance fungi.