Annual Vegetation of Saline Seasonal Wetlands (Crypsietea aculeatae) in Europe

Aims: The class Crypsietea aculeatae comprises pioneer ephemeral dwarf-graminoid vegetation occurring in periodically flooded saline habitats. Although numerous regional studies have described this vegetation, a unified classification across Europe has been lacking. This study aims to establish a formalized, continent-wide classification at the association level, identify its biogeographical patterns, and assess relationships between species composition and environmental gradients. Location: Europe (except Armenia, Azerbaijan, Georgia, and Russia). Methods: We compiled a dataset of 2538 vegetation plots from the European Vegetation Archive (EVA), private databases, and literature. A hierarchical expert system was developed using formal definitions of syntaxa based on species cover. Nonmetric multidimensional scaling (NMDS) was applied to evaluate compositional differences and reveal biogeographical patterns. Distance-based redundancy analysis (db-RDA) and unweighted community means of Ellenberg-type indicator values (EIVs) were used to assess environmental drivers. Results: We present a revised syntaxonomic framework for the class Crypsietea aculeatae and propose updates to the EuroVegChecklist. One alliance (Cypero-Spergularion marinae) and four associations (Crypsietum aculeatae, Crypsietum schoenoidis, Cyperetum pannonici, and Oxybasio chenopodioidis-Crypsietum aculeatae) were formally defined, with basic descriptions of their species composition, ecological characteristics, and geographical distribution. The main gradients in vegetation variability within the class Crypsietea aculeatae are driven by climatic gradient and edaphic factors, including soil moisture, soil acidity, salinity, and nutrient availability. Conclusions: We established the first formal classification of annual vegetation in European saline seasonal wetlands. The syntaxonomic nomenclature was revised, and modifications to the EuroVegChecklist were proposed. The resulting classification system, accompanied by an expert system, enables consistent application in nature conservation and ecological research.