On the other hand, variation in soil pH may reflect differences in the availability of simple organic PACA substrates for which Bacteria are more competitive. It is generally considered that fungal communities are less sensitive to soil pH than bacterial communities due to their wider pH range for optimal growth. However, arbuscular mychorrizal fungi biomass has been reported to co-vary with soil pH. This might explain why we also found significant covariation between Fungi and soil pH. In this study, we used variation partitioning to disentangle the relative contribution of the different drivers of microbial diversity. We found that the pure effect of plant species composition was always significant regardless of microbial taxa. Plants may affect microbial assemblages either through specific mutualistic/pathogenic interactions, soil structure changes via varying root architectures, specific root exudates, or through differences in competition intensity for nutrients. The combined effect of environmental variables and plant community composition noticeably explained bacterial and fungal community variation, implying that soil pH and/or SOM indirectly affect these communities. This latter result shows that the plant-soil feedbacks strongly act on microbial community assemblages, mainly through variations in mutualistic associations with plants for Fungi, and plant-mediated modification of soil properties for Bacteria. Crenarchaeal communities were rather explained by environmental conditions, mainly due to the soil pH effect as reported previously for autotrophic ammonia oxidizer Crenarachaeota. Finally, none of the microbial beta diversity patterns were due to BIHC geographic distances, neither at the landscape scale, nor for different classes of spatial distances. This result provides evidence that geographic distances do not account for microbial community changes across the landscape. This opposes previous findings for Bacteria and Fungi at large spatial scales, or for individual bacterial taxa at local scales. Possibly, these contradictory observations result from differences in taxonomic resolution.