Natálie Čeplová

Which traits influence the frequency of plant species occurrence in urban habitat types

Plants in cities must cope with various anthropogenic environments that differ from surrounding landscapes. Moreover, the differences in biotic and abiotic conditions among these habitats filter species with suitable traits and niche requirements. Here we aim to identify those attributes that promote species occurrence across and within urban habitat types of large cities. Species composition of spontaneously occurring vascular plant species was recorded in 1-ha plots in seven different urban habitat types in each of 32 European cities. Each species was characterized in terms of dispersal type, growth form, height, seed bank longevity, seed mass, selected leaf traits and ecological indicators including Ellenberg indicator values, Grime’s life strategies, and immigration pathways using information from available species-trait databases. For each species, total frequency of occurrence across all plots and habitat frequency of occurrence across plots of given habitat types were calculated and regression trees were used to relate them to traits and ecological indicators. The most frequently occurring species in the cities tended to be human-dispersed, nutrient-demanding plants that prefer drier to mesic soil conditions. These species do not possess the S-strategy and usually produce seeds of low mass forming short-term persistent seed banks. Habitat-specific responses were also revealed, indicating the effects of between- and within-habitat heterogeneity on trends in species performance in cities. Such patterns can be overlooked when differences in species occurrences in particular urban habitat types are not considered; thus, habitat-specific responses can resolve inconsistencies found when whole urban floras are analysed as a whole.

Urban ornamental trees: a source of current invaders; a case study from a European City

Human made habitats are considered to be important hotspots of biodiversity of native as well as alien plant species. Due to high propagule pressure caused by human activities they serve as a source of introduction of alien plant species. We used the database of planted ornamental trees and shrubs for Brno, Czech Republic, to determine the significance of introduction effort given by intensity of planting as a factor in woody plant naturalization. Of all planted woody taxa, 15% were recognized as spontaneously growing in the urban area and there was a significant relationship between the number of planted individuals and the ability of a species to spontaneously occur in the urban area. The most often spontaneously escaping species originated in Europe (55%), followed by neophytes from North America (21%) and Central and Eastern Asia (14%). Although only a minor portion of planted woody species is able to escape from cultivation, this still could represent a potential risk for the native vegetation.