Vegetation diversity of salt‐rich grasslands in S outheast E urope

Question How does the plant species composition of P ontic– P annonian salt‐rich habitats vary on a large geographical scale? Do the floristic differences between P annonia and the B alkans correspond to the current phytosociological classification? Location Pannonia ( H ungary, S lovakia, A ustria, C zech R epublic, C roatia, S erbia, R omania) and the B alkans ( B ulgaria, M acedonia, G reece). Methods Two thousand four hundred and thirty‐seven relevés from halophytic and sub‐halophytic habitats were classified using a modified TWINSPAN . The crispness of classification was checked. DCA and CCA with climate data as explanatory variables were applied. Results The classification was best interpreted at the level of 15 clusters. The vegetation changed along the salinity gradient from sub‐halophytic grasslands (including T rifolion resupinati alliance of the M olinio‐ A rrhenatheretalia class and B eckmannion eruciformis and F estucion pseudovinae p. p. alliances of the F estuco‐ P uccinellietea class) and reed beds ( B olboschoenion maritimi p. p. alliance; the P hragmito‐ M agnocaricetea class), through steppe and wet inland halophytic vegetation ( F estucion pseudovinae p. p. , P uccinellion limosae, P ucinellion convolutae, B olboschoenion maritimi p. p. and J uncion gerardii of the F estuco‐ P uccinellietea class) towards the extreme halophytic vegetation of the T hero‐ S alicornietea, C rypsietea and J uncetea maritimi classes. This gradient was longer in the B alkan region, where it spanned from the sub‐mediterranean salt‐rich grasslands to the extremely halophytic vegetation at the B lack S ea coast. The second most important gradient coincided with the water regime. Some vegetation types appeared to be confined to either the P annonian or the B alkan region (especially within dry sub‐halophytic and steppe halophytic grasslands), while others were distributed across the entire study area. The above‐mentioned pattern did not always correspond with current classification systems. Conclusions Variation in salt‐rich vegetation predominantly follows the salinity and water regime gradients. Geographical variation, generally coinciding with climatic and historical effects, is also important, especially in drier salt‐rich habitats. Our large‐scale analysis of the floristic variation of salt‐rich habitats might be useful for the unification of classification systems that differ substantially between the countries involved. In addition, the analysis may be useful for adjustment of a classification system in the poorly explored B alkan region, where particular vegetation types were identified with, or delimited from, C entral E uropean vegetation types without detailed comparative analysis until now.