Current climate change scenario, with continuously rising temperature and more frequent and severe drought episodes severely threatens the maintenance of forests at the rear end of their climatic distribution limit. Symbiotic associations between tree roots and ectomycorrhizal fungi (ECM) can contribute to maintain forest functionality by enhancing root uptake of water and nutrients. In this project, funded by the regional Basque Government, we aim to quantify the functional role of ECM in beech forests in northern Spain, where this species finds its driest distribution limit.