Abstract
The study is focused on evaluating changes in the presence of alien species in ruderal vegetation. Two datasets comprising phytosociological relevés of ruderal communities during two time periods within the Bratislava City (in southwestern Slovakia) were analyzed. The old dataset consisted of 387 relevés recorded in the years 1975–1982, and the more recent dataset consisted of 308 relevés from the years 2011–2014. The relevés from both time periods were assigned to phytosociological classes via the same procedure – numerical classification (hierarchical clustering) using HIERCLUS software. The average values of the percentage number and percentage cover of the archaeophytes and neophytes as groups in the earlier and more recent relevés of each class were compared by the main effects ANOVA analysis in the STATISTICA 7.0 software. The proportion of each taxon of archaeophytes and neophytes in both datasets was also calculated. The invasive status, origin, and life forms of alien species in both datasets were compared. In total, both datasets comprised 120 archaeophytes and 71 neophytes. The old dataset contained more archeaophytes than the more recent dataset. On the contrary, the more recent dataset contained more neophytes than the old dataset. In the years 2011–2014, more invasive neophytes were recorded than in the past. The results revealed a statistically significant decrease in the average percentage number of archaeophytes in the classes <em>Stellarietea mediae</em>, <em>Artemisietea vulgaris</em>, and <em>Galio-Urticetea</em>, and a decrease in the average percentage cover of archaeophytes in the class <em>Artemisietea vulgaris</em>, compared to the past. On the contrary, a statistically significant increase in the average percentage number and cover of neophytes in the classes <em>Artemisietea vulgaris</em> and <em>Galio-Urticetea</em> was recorded. Some rare species of archaeophytes were only recorded 30 years ago (e.g., <em>Kickxia elatine</em>, <em>Silene gallica</em>). Furthermore, several species of neophytes (including some invasive taxa, e.g., <em>Fallopia japonica</em>, <em>Helianthus tuberosus</em>, <em>Juncus tenuis</em>) occur only currently in the ruderal vegetation of Bratislava.
Highlights
Human activity is presently an important factor which significantly impacts ecosystems and individual coenoses
Human activities and changes in city environments are closely related to the diversity, frequency, and distribution of alien plant species, which are notably represented in ruderal communities [3]
We studied the dynamics of alien species in ruderal vegetation within the city over the time period of approximately 30 years
Summary
Human activity is presently an important factor which significantly impacts ecosystems and individual coenoses. Cities are places where human activity significantly influences an ecosystem [1,2]. Rendeková et al / Changes in presence of alien species in ruderal vegetation conditions reflected by well-adapted organisms and unique communities. Environmental conditions change very rapidly in urban areas, which has a significant effect on phytocoenoses. Human activities and changes in city environments are closely related to the diversity, frequency, and distribution of alien plant species (archaeophytes and neophytes), which are notably represented in ruderal communities [3]. The degree of impact of alien species in each group of plant communities varies [4,5]. The study of alien species dynamics in various ruderal habitats is very important
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