Temporal changes in the ectomycorrhizal community in two soil horizons of a temperate oak forest

The species structure of an ectomycorrhizal (ECM) community was assessed monthly for 15 months in the two horizons (A1 and A2) of an oak temperate forest in northeastern France. Ectomycorrhizal species were identified each month by internal transcribed spacer sequencing. Seventy-five fungal symbionts were identified. The community was dominated by Tomentellaceae, Russulaceae, Cortinariaceae, and Boletales. Four species are abundant in the study site: Lactarius quietus, Tomentella sublilacina, Cenococcum geophilum, and Russula sp1. The relative abundance of each species varied depending on the soil horizon and over time. Some species, such as L. quietus, were present in the A1 and A2 horizons. C. geophilum was located particularly in the A2 horizon, whereas T. sublilacina was more abundant in A1. Some species, such as Clavulina sp., were detected in winter, while T. sublilacina and L. quietus were present all year long. Our results support the hypothesis that a rapid turnover of species composition of the ECM community occurs over the course of a month. The spatial and temporal unequal distribution of ECM species could be explained by their ecological preferences, driven by such factors as root longevity, competition for resources, and resistance to environmental variability.