Background and aims <p>Ecological niche construction by ectomycorrhizal <i>Tuber</i> species (truffles) was described in alkaline soils in Mediterranean ecosystems but its variability depending on fungal species and soil environment is poorly known. The objective was to determine whether <i>Tuber</i> species construct niches in environments with low carbonate content or under acidic conditions, and how this niche construction can be observed at both the rhizosphere and brûlé scales.</p> Methods <p>A total of 213 soil samples associated with four <i>Tuber</i> species were analyzed at rhizosphere and brûlé/patch scales across seven geographical regions, ranging from highly alkaline to moderately and highly acidic soils.</p> Results <p>All 4 <i>Tuber</i> species raised soil pH when comparing soils inside and outside their brûlés/patches: <i>T. oregonense</i> in very acidic soils, <i>T. melanosporum</i> and <i>T. brumale</i> in neutral to slightly alkaline soils, and <i>T. aestivum</i> in alkaline soils. Concomitantly, <i>T. melanosporum</i> and <i>T. brumale</i> increased exchangeable Ca²⁺, thereby further alkalising slightly calcareous soils. <i>Tuber melanosporum</i> increased Ca²⁺ by decalcifying highly calcareous soils. At the rhizosphere scale, the mycelium of <i>T. aestivum</i> was negatively correlated with soil pH in decalcified and neutral soils. The mycelium of <i>T. melanosporum</i> was positively correlated with exchangeable Ca²⁺/Mg²⁺ and negatively with P and exchangeable Mg²⁺ availability in alkaline soils, thereby modifying soil fertility in the host plant rhizospheres.</p> Conclusions <p>We infer that <i>Tuber</i> species control the abundance and chemical forms of soil Ca by regulating soil pH (through changes in the fungal-plant excretions of low-molecular-weight organic anions and their complex effect on soil pH, inorganic components and microorganisms), a mechanism likely shared by other ectomycorrhizal fungi and one that could affect the nutrition of host plants.</p>