Ectomycorrhizal competition as a driver of root-zone niche partitioning: insights from Tuber aestivum and Tuber rufum

Understanding how ectomycorrhizal (ECM) fungi interact is essential for both general mycorrhizal ecology and for practitioners in fields such as truffle cultivation. We investigated competitive interactions between Tuber aestivum (the summer truffle) and Tuber rufum under controlled conditions, testing two soil pH conditions (6.5 and 7.5) and two commonly accepted host species ( Quercus robur and Corylus avellana ). While T. rufum is often reported in mildly acidic soils, we found it formed significantly more mycorrhizae under alkaline conditions— a trait it shared with T. aestivum . However, under co-inoculation, T. aestivum consistently outperformed T. rufum , yet both species performed better in isolation. Strikingly, competition promoted spatial niche partitioning in hazel root systems, with T. aestivum dominating mid-root zones and T. rufum the lower zones— an effect absent in sub-optimal (pH 6.5) conditions. From an applied perspective, these findings highlight that host tree choice may influence truffle orchard outcomes when competitive ECM species co-occur. More broadly, our results suggest that root-zone niche partitioning may represent an important, underexplored mechanism of ECM coexistence. Together, this underscores the ecological complexity of truffle systems and the need for integrated lab–field approaches to advance both applied and fundamental mycorrhizal research.