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Introduction and objective. The invasive alien species Ambrosia artemisiifolia cause environmental, agronomical and medical problems in many regions of the world, including Slovakia. The purpose of this study was to survey the spread and distribution of this species in Slovakia and to analyse its airborne pollen pattern. Materials and methods. To evaluate the spatiotemporal dynamics of Ambrosia invasion in the territory of Slovakia, herbarium specimens, published databases and field investigations were considered. Aerobiological sampling was based on the analysis of pollen records at five aerobiological stations in Slovakia. For Bratislava and Banská Bystrica Monitoring stations, trends in Ambrosia pollen seasons were determined using Mann-Kendall test and Sen's slope estimator. Results. Since the first record of A. artemisiifolia in Slovakia, the number of its colonies and its spread rate has increased considerably, and the colonisation of this species has been successful mainly in the southwestern part of the country. Highest airborne pollen counts were recorded in Nitra, Trnava and Bratislava Monitoring Stations situated in the areas most infested by A. artemisiifolia in Slovakia. However, high pollen counts were also noted in Banská Bystrica and Košice Monitoring Stations situated in areas where the source species was less abundant. During the study period, the number of days on which the pollen concentration exceeded the threshold of sensitivity increased significantly (+1.33 days/year) in Banská Bystrica, whereas the peak value decreased significantly (-13.37 pollen/year) in Bratislava. Conclusion. The number of the populations of A. artemisiifolia has increased considerably in recent years. Besides the most infested areas, high airborne pollen counts were also recorded in territories where the plant species was less abundant. During the study period, the intensity of Ambrosia pollen seasons decreased in Bratislava, probably due to changes in landuse practices, while the increasing trend in the pollen seasons intensity in Banská Bystrica mainly reflects the situation in the ragweed-infested remote areas due to long-range pollen transport.

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Invasive species pose one of the most serious global environmental threats. Our study aimed to examine the correlation between the proportion of invasive alien taxa and species diversity of ruderal vegetation in the urban ecosystem of Bratislava, located in Central Europe. Ruderal habitats serve as the means of spread of invasive species to seminatural and natural habitats. Twenty-six invasive taxa were recorded among the ruderal vegetation of Bratislava. The majority of the recorded invasive species were neophytes, which came from North America and represent the Asteraceae family. Half of them were introduced accidentally, whereas the remaining species were introduced deliberately. Correlation and regression analyses showed that the proportion of invasive taxa has a negative effect on the species diversity of all the analyzed syntaxa in the ruderal vegetation of Bratislava.

Green infrastructure (GI) brings many benefits to urban ecosystems. Green tram tracks can be considered to be a part of GI. The presented study is focused on the comparison of the species’ frequency and composition between conventional tram tracks and green tram tracks in Bratislava, Slovakia, Central Europe. This comparison also provides an insight into the changes of the flora of tram tracks over time, as we compare the results of the older research with recent research on green tram tracks. The results revealed significant differences in the composition of flora between conventional tram tracks and green tram tracks. In particular, the total number of species has decreased over time, as green tram tracks host fewer spontaneously growing taxa than conventional ones. The frequency of occurrence of archaeophytes and neophytes has decreased on the strict rail yard while on the tracksides it has increased. Green tram tracks deliver positive features to ecosystems, but may also have negative aspects because they present a pool of alien, potentially invasive plants.