Railways as a source of alien plants

Railways have served as a pathway in the introduction of many alien species. The majority are introduced mainly as contaminants of commodities or are hitchhikers, but some are ornamentals and utility taxa planted near railway buildings that escape from cultivation. A field survey was carried out along the freight railway corridor Břeclav – Kolín – Praha – Děčín (central Europe, Czech Republic) at 39 localities, such as railway stations, railway yards and important railway junctions, in 2020–2022. Each locality was divided into three zones reflecting the type of management and land use: (i) tracks and embankments, (ii) wider surroundings and (iii) surroundings of buildings. The aim of this study was to produce a list of taxa that occurred in railway stations and yards and their surroundings, determine the incidence in these floras of alien species, and, by comparing historical and recent records, identify species whose distributions have changed over time. A total of 11,139 records belonging to 764 taxa, including 403 (53%) native, 309 (40%) alien species and 85 (11%) Red-Listed taxa of various threat categories were recorded. The tracks and embankments were generally richer in species, including aliens, and the zones and location of railway lines affected the species composition; the effect of zones on both species richness and composition was stronger than that of sections of railway lines. Compared to the historical records, 109 new aliens were recorded, while 112 previously reported were absent. Our results indicate that the tracks and embankments, and close surroundings of buildings constitute a similar habitat with the same alien flora, whereas the wider surroundings host different alien species. Therefore, it can be concluded that for the majority of the alien species the surroundings of railway stations and yards are not a stepping stone for the spread away from railway tracks. One of the reasons why alien species associated with railways do not spread into the wider surroundings is most likely the presence there of many competitively stronger species.