Predicting porcini: a decade of sporocarp monitoring reveals the meteorological triggers of Boletus edulis fruiting in central European beech forests

Despite recent molecular and genomic advances, the reproductive biology of ectomycorrhizal fungi (EMF) remains poorly understood. In particular, the meteorological cues triggering sporocarp formation remain largely unknown, limiting our ability to induce fruiting in the laboratory. To address this knowledge gap, we analysed a decade-long (2015-2024) dataset of daily, near-exhaustive sporocarp observations from an intensively monitored population of Boletus edulis in a central European beech forest near Bielefeld, Germany. Using generalised linear mixed-effect models, we estimated the lagged effects of temperature and precipitation on sporocarp formation and identified the conditions associated with peak fruiting. Although sporocarps formed across a broad range of conditions, peak fruiting was associated with a mean temperature of approximately 13{degrees}C averaged over the preceding 20 days and increased linearly with precipitation accumulated over a 26-day window. Under projected warmer and drier autumn conditions, B. edulis sporocarp formation in European beech forests is likely to decline.