Drivers of fungal and bacterial communities in ectomycorrhizospheres of birch, oak, and pine in a former uranium mining site, Ronneburg, Germany

The impact of soil and tree species on fungal and bacterial communities was investigated in a former uranium mining area with field and pot studies of the mycorrhizospheres of birch (Betula pendula), oak (Quercus robur), and pine (Pinus sylvestris). At the initial stages of succession re-created in the pot experiment, tree-species-specific microbial communities were detected. The pot microbiomes showed lower diversity and evenness of fungi and bacteria as compared to field-grown trees. In the natural field setting, the fungal community both in bulk and rhizosphere soil consisted of mainly Thelephoraceae, Inocybaceae and Russulaceae. They contributed with Leotiaceae and Herpotrichiellaceae to 52–85% of overall abundances, showing the soil hyphae impact of ectomycorrhiza in the tree stand. The fungal communities and their distribution patterns reflected host tree specificity and successional stage of the ectomycorrhizosphere. In the bacterial community, the most abundant bacterial classes were Alphaproteobacteria, Acidobacteria, Ktedonobacteria, Bacteroidia, Gammaproteobacteria, and Phycisphaerae representing about 59–80% of all bacterial sequences. The bacterial communities correlated with soil chemical parameters, particularly the content of toxic metals, total nitrogen and C/N ratio. This study allowed to identify drivers for microbial community composition, which might be helpful to develop afforestation strategies in post-mining landscapes.