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AbstractThis study is focused on the evaluation of the values of the diversity indices of semi-natural dry calcareous grasslands of the Festuco-Brometea class in the area of Devínska Kobyla National Nature Reserve 50 years after abandonment of traditional management (grazing and mowing). The values of the species richness, the Shannon–Wiener index of diversity, the Simpson index, and Pielou’s measure of species evenness in the communities in the old and recent data, and the values of the environmental variables based on the Ellenberg indicator values of species were analyzed. For most of these analyses, we used Kruskal–Wallis in R 3.5.1. Compared to the past, we have recorded a significant lower values of the species richness, biodiversity, and species evenness in some communities. In some communities, no significant changes were recorded. Only in one community—Poo badensis-Festucetum pallentis, the higher values of Shannon–Wiener index was recorded compared to the past. The analysis of the Ellenberg indicator values revealed a statistically significant higher Ellenberg indicator values for moisture and nutrients and lower values for light in more recent period compared to the old period. The recorded results could be caused by the changes in the management after the year 1965, after abandonment of grazing and the gradual overgrowing by woody species took place in the area. The frequency of occurrence of some woody species (e.g., Populus alba, P. nigra, and Robinia pseudoacacia) in some communities increased compared to the past.

This study reports the results of the evaluation of changes in the species diversity and composition of ruderal vegetation of three Slovak and one Czech city over the time. The dataset of 1489 relevés from five ruderal syntaxa from the cities Bratislava, Malacky, Trnava and Brno was used. Data were from two different time periods, the older dataset from the years 1960–1982, the more recent dataset from the years 2005–2016. The statistical analysis revealed the decrease of Shannon–Wiener diversity index of all (native + alien) species in the majority of classes of ruderal vegetation of cities. The analysis of the changes in the Pielou’s measure of species evenness showed that in some of the classes and cities, the species evenness remained unchanged, in the other ones it decreased. The percentage of native species in the ruderal vegetation did not change over the time, but the percentage of invasive alien species in the majority of syntaxa and cities increased significantly. In total, 38 invasive taxa were recorded in the ruderal vegetation of cities. Most of them are neophytes, therophytes and belong to the family Asteraceae. The majority of invasive taxa were recorded in both time periods. Some of the invasive species, e.g. Fallopia japonica and Juncus tenuis were recorded only in the more recent time period. Our results contribute to the knowledge about biological invasions in the cities.

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.