Numerical classification of alder carr and riparian alder forests in Slovakia

Abstract

Syntaxonomy and ecology of the alder carr (alliance Alnion glutinosae) and riparian alder forests (suballiance Alnenion glutinoso-incanae) of Slovakia have not yet been critically revised. Application of numerical approach allowed us to disentangle and resolve syntaxonomical affinities among vegetation units previously reported in Slovakia. The present synthesis was based on analysis of 918 recent and historical phytosociological relevés originating from the Slovak Vegetation Database and available unpublished sources. Three floristically and ecologically interpretable associations of the Euro-Siberian alder carr forests of Alnion glutinosae (Thelypterido palustris-Alnetum glutinosae Klika 1940, Carici elongatae-Alnetum glutinosae Tüxen 1931, Carici acutiformis-Alnetum glutinosae Scamoni 1935) and seven of the European ash-alder riparian forests of Alnenion glutinoso-incanae (Carici remotae-Fraxinetum excelsioris Koch ex Faber 1936, Stellario nemorum-Alnetum glutinoase Lohmeyer 1957, Pruno padiFraxinetum excelsioris Oberdorfer 1953, Matteuccio struthiopteridis-Alnetum glutinosae Magic et Kliment in Kliment et Watzka 2000, Cardamino amarae-Alnetum incanae Šomšák 1961, Piceo abietis-Alnetum glutinosae Mráz 1959, Alnetum incanae Lüdi 1921) have been identified using unsupervised numerical classification. Each association was characterized by list of synonyms, diagnostic, constant and dominant species, overall floristic description, site requirements and chorological aspect. Main environmental gradients responsible for vegetation changes were determined in detrended correspondence analysis and interpreted using the Ellenberg indicator values (EIV) and altitude. Variation in species composition pattern corresponded to the altitudinal gradient and EIV for moisture, nutrients and soil reaction.