ERP131301 PRJEB47058 ena-STUDY-INRES Molecular Biology of the Rhizosphere-18-08-2021-11:38:52:088-1225 Land use and geomorphology-induced soil heterogeneity controls biogeographic patterns of the soil microbiota of a kettle hole Kettle hole are small lentic wetlands < 1 ha usually embedded in agricultural used land in Northern Germany. Due to highly dynamic water tables, environmental conditions in soils are alternating within few meters within kettle holes which aggravates the estimation of the ecological function of these systems as carbon sink or source. In this study we collected soils from one kettle hole in the radius of 30 m. The taken soil cores were sliced due to visible criteria to take different development of soils into account, which leads to a distinction into sandy, peaty, colluvial and top soils. Additional soil samples from the surrounding landscape were collected for comparison. Basic soil characteristics (total carbon, total nitrogen content, pH, water content) were determined in the lab to further characterize the collected soils. Microbial community analysis was performed via 16S rRNA sequencing and qPCR. Our results show, that kettle hole soils harbor a highly variable microbiota. At drier kettle hole sites microbial communities more similar to acre soils were found, indicating a gradual change due to the landscape element. In contrast, colluvial and peaty soils form more distinct clusters. Visible soil traits were found to be mainly responsible for shifts within the microbial community composition (ADONIS, R2 =0.17, P=0.001), with a higher correlation compared to soil location (R2 =0.09, P=0.001) and pH (R2 =0.08, P=0.001). However, these correlations are relatively low, suggesting that the spatial heterogeneity of the microbiota overrides these factors and/or depends on other variables not analyzed, such as the duration of flooding. Our results further indicate that colluvial soil horizons are likely a hot spot of biogeochemical cycling which is indicated by significant higher relative abundances of e.g. Geobacteraceae, Nitrosomonadaceae, Methylomirabilaceae and Desulfocapsaceae. These compositional changes might indicate, that these layers might be important for controlling the release of green gases like nitrous oxide or methane from kettle holes. Therefore, further studies addressing small-scale changes of microbiota in connection with green house gas fluxes are needed. Kettlehole Kettle hole are small lentic wetlands < 1 ha usually embedded in agricultural used land in Northern Germany. Due to highly dynamic water tables, environmental conditions in soils are alternating within few meters within kettle holes which aggravates the estimation of the ecological function of these systems as carbon sink or source. In this study we collected soils from one kettle hole in the radius of 30 m. The taken soil cores were sliced due to visible criteria to take different development of soils into account, which leads to a distinction into sandy, peaty, colluvial and top soils. Additional soil samples from the surrounding landscape were collected for comparison. Basic soil characteristics (total carbon, total nitrogen content, pH, water content) were determined in the lab to further characterize the collected soils. Microbial community analysis was performed via 16S rRNA sequencing and qPCR. Our results show, that kettle hole soils harbor a highly variable microbiota. At drier kettle hole sites microbial communities more similar to acre soils were found, indicating a gradual change due to the landscape element. In contrast, colluvial and peaty soils form more distinct clusters. Visible soil traits were found to be mainly responsible for shifts within the microbial community composition (ADONIS, R2 =0.17, P=0.001), with a higher correlation compared to soil location (R2 =0.09, P=0.001) and pH (R2 =0.08, P=0.001). However, these correlations are relatively low, suggesting that the spatial heterogeneity of the microbiota overrides these factors and/or depends on other variables not analyzed, such as the duration of flooding. Our results further indicate that colluvial soil horizons are likely a hot spot of biogeochemical cycling which is indicated by significant higher relative abundances of e.g. Geobacteraceae, Nitrosomonadaceae, Methylomirabilaceae and Desulfocapsaceae. These compositional changes might indicate, that these layers might be important for controlling the release of green gases like nitrous oxide or methane from kettle holes. Therefore, further studies addressing small-scale changes of microbiota in connection with green house gas fluxes are needed. ENA-FIRST-PUBLIC 2021-12-14 ENA-LAST-UPDATE 2021-12-14