Roots can considerably alter soil pH – up to several units – over short spatial and temporal scales as a result, primarily, of their nutrition (cation/anion balance across the root/soil interface) and, in some instances, respiration. We will briefly review how these root-induced pH changes have a dramatic effect on key biogeochemical processes such as: (i) dissolution/precipitation of soil minerals and (ii) adsorption/desorption of ions, and hence bioavailability of either anions (e.g. phosphate) or cations (e.g. copper). Further understanding the resulting, rather unique rhizosphere biogeochemistry is thus pivotal to quantifying the driving role of higher plants in ecosystem services, especially support services such as soil formation and nutrient cycling. In addition, soil pH has been recently shown to be a major ecosystem property governing the biogeography of soil microbial communities across spatial scales, from continental to local (plot) scales. Here we report the first evidence of the role of root-induced pH changes on the distribution of microbial communities at a centimetric scale, in the rhizosphere of ectomycorrhizal plants. This finding challenges the view of a carbon-based rhizosphere effect and suggests that, beside rhizodeposition of carbon compounds, rhizosphere pH may be the clue for shaping microbial ecology in the root environment.