Modelling environmental drivers of Tuber melanosporum extraradical mycelium in productive holm oak plantations and forests

The black truffle (Tuber melanosporum Vittad.) is a highly appreciated edible ectomycorrhizal fungus. It grows belowground and the mycelium and sporocarp production greatly depends on the abiotic environmental conditions. Although there is some evidence about the variables influencing the truffle mycelium at local scale, there is still a lack of knowledge on the soil and climatic patterns driving mycelium growth at broader scales. We aimed to decipher the potential environmental drivers of T. melanosporum mycelium across its westernmost natural distribution area. A paired-design experiment with truffle productive plantations and forests was set up across 10 sites. Mycelium biomass was qPCR-quantified, physicochemical soil analyses were done, and climatic data were collected to perform generalised additive modelling. Mycelium dynamics was driven by a combination of soil and climatic variables that accounted for 65.7% of mycelium variance in plantations and 53.4% in forests. Longitude, CaCO3, Na and Zn were related, either positively or negatively, with soil mycelium distribution in forests, while elevation, organic matter, P, Mg and B, were the main potential drivers of truffle mycelium biomass in plantations. These results strengthen our knowledge on black truffle ecology and can be applied to design management strategies for optimization of truffle mycelial biomass and sporocarp production.