In vitro microcosm study of Morchella eximia mycelial growth on post-wildfire burnt soil and charcoal fragments

This study investigates the in vitro growth dynamics of the mycelium of the pyrophilous mushroom Morchella eximia on substrates composed of burnt soil and charcoal fragments. Soil samples were collected one month after a wildfire from a Pinus pinaster forest on Monte Pisano (Italy). These samples were inoculated with M. eximia mycelium, and fungal colonization and development under controlled microcosm conditions were subsequently assessed. The chemical analysis was performed on the burnt soil to quantify macro- and micronutrients. After the mycelial growth, the charcoal structure was examined using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. Additionally, Scanning Electron Microscopy (SEM) was applied to visualize and confirm hyphal colonization of the charcoal. Morchella eximia colonization elicited significant structural alterations in charcoal structure. Spectroscopic analysis demonstrated an increased relative intensity of the primary charcoal band concomitant with a pronounced decrease in the secondary band, indicative of modifications within the charcoal’s structural matrix. Furthermore, reduced spectral signals observed near 1169 cm⁻¹, corresponding to C–O functional groups in lignin-derived phenolic compounds, provide evidence for chemical transformations occurring in the charcoal. These results highlight the potential involvement of pyrophilous fungi in the degradation of charcoal and emphasize the necessity for further investigations to clarify their ecological functions and long-term effects on fungal community dynamics.