Bryophytes of the Loess Cliffs in the Pannonian Area of Austria

Austrian loess cliffs represent unique habitats supporting a rich bryophyte flora, including numerous rare and endangered species. We conducted a comprehensive survey of 86 loess cliff sites in the Pannonian area of Lower Austria, Burgenland, and Vienna, recording 79 bryophyte species. The results highlight that Austrian loess cliffs, despite their small spatial extent, are key refugia for light-demanding, desiccation-tolerant bryophytes. Hilpertia velenovskyi, a critically endangered species, was recorded at six new sites, expanding its known Austrian distribution. Our study also documents the first Austrian occurrences of several Pterygoneurum species. Seven bryophyte communities were distinguished: Aloinetum rigidae, Hilpertio velenovskyi–Pterygoneuretum compacti, and the newly described subassociations Didymodontetum glauci didymodontetosum cordati and Eurhynchietum schleicheri didymodontetosum cordati, as well as Pterygoneuro–Acaulonetum triquetri ass. nov. Multivariate analyses suggest carbonate content as the most consistent environmental driver. Despite their ecological significance, loess cliffs are increasingly threatened by habitat loss, overgrowth by vascular plants, and shading from invasive trees. Our study provides a detailed syntaxonomic and ecological framework for bryophyte communities on loess cliffs, underlining their role as refugia for rare species and the urgent need to protect remaining sites in the Pannonian region.