ERP022217 PRJEB20098 ena-STUDY-Barta-22-03-2017-10:29:13:847-92 Distinct effects of cotton-grass and blueberry on belowground microbial community structures and functions in spruce swamp forest Spruce swamp forests (SSF) are unique ecosystems lying between open peatlands and mineral soil forests and share functioning of both ecosystems. In SSF, Sphagnum mosses are accompanied with cotton-grass or blueberry dominated understorey, creating heterogeneous patchy environment. We hypothesized that the presence of vascular plants affects microbial community structure and functions in peat soil. Additionally, seasonal dynamics of microbial communities and selected functional guilds were investigated. The results revealed that the composition of prokaryotic and fungal communities in the peat soil is vegetation specific. Fungal communities were dominated by Agaricomycetes and Archaeorhizomycetes in cotton-grass and blueberry sites, respectively. The presence of both vascular plants lowered relative proportion of anaerobic bacteria (Clostridiales, Bacteroidales, Chloroflexi) within prokaryotes. The presence of vascular plants affected extracellular enzymatic activity, fungal and methanotrophic biomass, however, it did not affect respiration rates, potential methane production or methanogenic biomass. Seasonality further affected ß-glucosidase and phosphatase activities as well as bacterial, methanotrophic and methanogenic abundance. All these changes might be attributed to altered water regime, O2 availability, and soil chemistry as affected by dominant vascular plants, its rhizodeposition and mycorrhizal interactions. To conclude, vascular plants significantly affect soil microbial community composition and shift microbial functional guilds, thus driving functional diversity within SSF system, especially in methane cycling and peat decomposition rate. Microbial communities in spruce swamp forest Spruce swamp forests (SSF) are unique ecosystems lying between open peatlands and mineral soil forests and share functioning of both ecosystems. In SSF, Sphagnum mosses are accompanied with cotton-grass or blueberry dominated understorey, creating heterogeneous patchy environment. We hypothesized that the presence of vascular plants affects microbial community structure and functions in peat soil. Additionally, seasonal dynamics of microbial communities and selected functional guilds were investigated. The results revealed that the composition of prokaryotic and fungal communities in the peat soil is vegetation specific. Fungal communities were dominated by Agaricomycetes and Archaeorhizomycetes in cotton-grass and blueberry sites, respectively. The presence of both vascular plants lowered relative proportion of anaerobic bacteria (Clostridiales, Bacteroidales, Chloroflexi) within prokaryotes. The presence of vascular plants affected extracellular enzymatic activity, fungal and methanotrophic biomass, however, it did not affect respiration rates, potential methane production or methanogenic biomass. Seasonality further affected ß-glucosidase and phosphatase activities as well as bacterial, methanotrophic and methanogenic abundance. All these changes might be attributed to altered water regime, O2 availability, and soil chemistry as affected by dominant vascular plants, its rhizodeposition and mycorrhizal interactions. To conclude, vascular plants significantly affect soil microbial community composition and shift microbial functional guilds, thus driving functional diversity within SSF system, especially in methane cycling and peat decomposition rate. amplicon sequencing peatland soil ENA-FIRST-PUBLIC 2017-05-21 ENA-LAST-UPDATE 2017-03-22