Mountain ecosystems and cold deserts are especially rich in lichens and are excellent field laboratories to study them under various stress conditions. Ecosystems of these types, namely the European Alps and Antarctica with their lichen biota, have also been in the focus of interest by Roman Türk in the last four decades. We took the occasion of Roman Türk's 65th birthday to invite a number of his colleagues and friends to contribute papers on aspects of lichens in mountain and polar ecosystems for this volume of Bibliotheca Lichenologica. The 17 reviewed contributions cover lichens from the European Alps, tropical Africa, on La Soufrière volcano to Dronning Maud Land, Antarctica. This volume addresses the public interested in lichenology, and the editors are pleased to offer these contributions as further steps towards a better knowledge of taxonomy, diversity, distribution and ecology of lichens. The volume was carefully edited by three prominent and active members of the lichenological community, Josef Hafellner, University of Graz, Austria, Ingvar Kärnefelt, University of Lund, Sweden, and Volkmar Wirth, Natural History Museum, Karlsruhe, Germany.