Hardwood floodplain forests in Slovakia: syntaxonomical revision

Hardwood floodplain forests in Slovakia have been traditionally classified within the class Querco-Fagetea, order Fagetalia, alliance Alnion incanae, suballiance Ulmenion. Five main syntaxonomical studies on this topic come from the years 1958–1972 and were published by several authors from different regions. Each author described several new geographically delimited subassociations which were considered to be confined to single lowland region. This resulted in unclear classification scheme of hardwood floodplain forests in Slovakia with numerous floristically poorly differentiated units, especially at the subassociation level. We used 404 relevés ordered to the suballiance Ulmenion in the Slovak national database (http://ibot.sav.sk/cdf/) and analysed the dataset by cluster analysis and detrended correspondence analysis. We distinguished four groups of relevés which represents four subassociations within one association Fraxino pannonicae-Ulmetum: Fraxino pannonicae-Ulmetum caricetosum acutiformis Soó in Aszód 1936 corr. Soó 1964, Fraxino pannonicae-Ulmetum populetosum Jurko 1958 (D?atko 1972), Fraxino pannonicae-Ulmetum carpinetosum (Simon 1957) D?atko 1972 and Fraxino pannonicae-Ulmetum convallarietosum Jurko 1958. Associations Querco pedunculiflorae-Populetum tremuli ?om?ák et Háberová 1979, Arunco-Salicetum capreae Hada? et al. 1969 and Filipendulo-Salicetum capreae Hada? et al. 1969 we propose to exclude from the suballiance Ulmenion.