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Czechowski and Pisarski (1990) described the species composition and structure of ant communities of wooded patches (originally Tilio-Carpinetum) in Warsaw, situated along the Vistula river escarpment within the city. The paper was immediately succeeded by S eifert’s (1991, 1992) taxonomic revision, where one of the most abundant species there, Lasius niger, was split into two sibling species: L. niger (L.) and L. platythorax Seifert, which clearly differ in their ecological requirements. Re-examination of the old material in the light of the present taxonomic knowledge showed that only L. niger, a polytope of moderately dry open habitats, was present in the study habitat. L. platythorax, a polytope of moderately wet forests, was lacking from urban wooded areas.
In total 273 stands of the invasive species Fallopia (Reynoutria) japonica in Oświęcim valley (southern Poland) were examined, in terms of cover, area, abundance, height and width of shoots, and presence of coexisting species. F. japonica occurred more frequently in wastelands and was the rarest in forests. Statistical analyses revealed some significant differences among habitats with particular traits. The most abundant populations, occupying the largest area, were recorded in wetlands and along railway lines. Populations were very diverse in terms of their percentage of flowering shoots within a particular type of habitat, however, the highest percentage was again observed in wetlands and along railways. In forests, gardens and in wastelands the contribution of flowering shoots was lower. The presence of accompanying species in the studied populations was generally low, most frequently stands of F. japonica were mono-specific with a slightly higher cover of accompanying species being recorded in F. japonica populations in forests. The highest proportion of the tallest shoots within a patch of F. japonica was observed in wetlands, while the lowest was in wastelands and in railways. The individuals with the thickest shoots were present in forests and wetlands and the thinnest in wastelands. Despite the simplified nature of the data collection the study demonstrated that F. japonica is more vigorous and forms larger stands occupying larger areas in some of the analyzed habitats. The study showed that in manmade habitats the considered species has favourable conditions for its development and further spread and this is of concern to conservationists and land managers as it can pose a threat to native biodiversity.
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 Stellarietea mediae, Artemisietea vulgaris, and Galio-Urticetea, and a decrease in the average percentage cover of archaeophytes in the class Artemisietea vulgaris, compared to the past. On the contrary, a statistically significant increase in the average percentage number and cover of neophytes in the classes Artemisietea vulgaris and Galio-Urticetea was recorded. Some rare species of archaeophytes were only recorded 30 years ago (e.g., Kickxia elatine, Silene gallica). Furthermore, several species of neophytes (including some invasive taxa, e.g., Fallopia japonica, Helianthus tuberosus, Juncus tenuis) occur only currently in the ruderal vegetation of Bratislava.
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