Flora of the tram tracks of Bratislava

Tram and railway tracks represent specific urban habitats, which host a specific type of flora. This study aims to compile the information about species composition of flora of tram tracks in the city of Bratislava (Slovakia, Central Europe), to compare the representation of alien and native plant taxa growing both directly in the rail yard and at a greater distance from the tracks, and to analyse the differences among flora growing on various soil types of the tram tracks. Cluster analysis, the Mann-Whitney U test and Kruskal-Wallis non-parametric ANOVA were used for the analyses. The majority of the recorded taxa (51.9%) were native, 28.9% were archaeophytes and 19.3% were neophytes. Among the alien species, 16 were invasive; the most abundant being Ailanthus altissima (juvenile), Amaranthus retroflexus, Conyza canadensis, and Echinochloa crus-galli. The most frequent taxa growing on tram tracks were Achillea millefolium agg., Cichorium intybus, Eragrostis minor, Plantago lanceolata, Polygonum arenastrum, Portulaca oleracea, and Taraxacum sect. Ruderalia. The endangered plant species Misopates orontium, Petrorhagia saxifraga, and Senecio vernalis were also recorded on the tram tracks of Bratislava. Analyses revealed statistically significant differences in the number of taxa among the different soil types and significant differences in flora found strictly within the rail yard and those growing at a greater distance from the tracks (i. e. tracksides). The number of alien species recorded directly in the rail yard was higher than on the tracksides.