In some regions of Slovakia, black alder forest vegetation has not been documented appropriately yet. This paper is the first vegetation study presenting the phytosociological data and measured environmental parameters from the western part of central Slovakia. The data set was classified by using a modified TWINSPAN algorithm, which allowed us to discern floristically and ecologically distinctive plant communities. They correspond to the associations Stellario nemorum-Alnetum glutinosae Lohmeyer 1957 (riparian alder vegetation on mesic to humid sites along small brooks) and Carici acutiformis-Alnetum glutinosae Scamoni 1935 (eutrophic black alder carr forests in the colline zone) with the variants of Ligustrum vulgare and Galium palustre. The community Carici elongatae-Alnetum glutinosae Schwickerath 1933 (mesotrophic to eutrophic alder carr vegetation growing on permanently waterlogged soils), documented only with two phytosociological relevés, was distinguished following expert knowledge. A floristic and ecological pattern of these associations is presented. The major compositional gradients were interpreted based on Ellenberg’s indicator values and the values of environmental variables recorded during the field sampling in the growing season 2011. The principal component analysis revealed the importance of soil moisture, light availability, portion of open water and soil surface for species composition variability at the association level, whereas the variants of Carici acutiformis-Alnetum glutinosae were sorted along the acidity gradient. Gozdna vegetacija črne jelše dosedaj v nekaterih predelih Slovaške še ni bila dovolj raziskana. Članek predstavlja prvo vegetacijsko raziskavo fitocenoloških popisov in merjenih rastiščnih dejavnikov iz zahodnega dela osrednje Slovaške. Podatkovni niz smo klasificirali z modificiranim TWINSPAN algoritmom, s čemer smo lahko floristično in ekološko ločili značilne rastlinske združbe. Ugotovili smo asociaciji: Stellario nemorum- -Alnetum glutinosae Lohmeyer 1957 (obvodna črnojelševja na srednje do vlažnih rastiščih ob manjših potokih) in Carici acutiformis-Alnetum glutinosae Scamoni 1935 (evtrofna črnojelševja v kolinskem pasu) z dvema variantama Ligustrum vulgare in Galium palustre. Asociacijo Carici elongatae-Alnetum glutinosae Schwickerath 1933 (mezotrofni do eutrofni črnojelševi grezi, ki uspevajo na tleh stalno prepojenih z vodo), ki je dokumentirana samo z dvema popisoma smo določili na podlagi strokovnega poznavanja. Prikazali smo floristični in ekološki vzorec pojavljanja teh asociacij. Glavni gradienti so pojasnjeni na podlagi Ellenbergovih indikatorskih vrednosti, ekološki dejavniki pa so bili merjeni med terenskim vzorčenjem v vegetacijski sezoni 2011. Analiza glavnih komponent je razkrila pomen vlažnosti tal, svetlobe, deleža odprtih vodnih in talnih površin za variabilnost vrstne sestave na nivoju asociacij, medtem ko se varianti asociacije Carici acutiformis-Alnetum glutinosae ločita na gradientu kislosti.