Agnieszka Kompała-Bąba1, Wojciech Bąba2, Agnieszka Błońska1 and Robert Hanczaruk1
1University of Silesia in Katowice, Faculty of Biology and Environmental Protection, Department of Botany and Nature Protection, Jagiellonska 28, 40-032 Katowice, Poland
2Jagiellonian University, Institute of Botany, Department of Plant Ecology, Gronostajowa 3, 30-387 Kraków, Poland
We studied urban and rural communes situated in the Silesian Uplands (southern Poland). In total, 2227 vegetation and soil samples were obtauned in ruderal habitats located in towns in habitats such as built-up and industrial areas, abandoned fields, gardens, cemeteries, urban parks, lawns, road, tram and railway tracks. The aim of this study was to (i) show the participation of alien species in the floristic composition of distinguished vegetation patches, and (ii) to determine how species traits are selected along environmental gradients. As a result of classification, 26 repeated vegetation units were delimited. The floristic composition of these units significantly differed in reference to participation of native and alien species. Native synanthropic species (apophytes) prevailed in the floristic composition in almost all of the examined plant communities. Some alien species, such as Solidago canadensis, Conyza canadensis, Solidago gigantea, Matricaria maritima subsp. inodora, and Erigeron annuus, occurred most frequently in vegetation patches (i.e. more than 300 patches and at least in 20 plant communities). Alien species whose origin dates back to 15th century (i.e. archaeophytes), such as Berteroa incana and Ballota nigra, had a higher abundances in phytocoenoses that developed on trampled places (e.g. on unmowned lawns, roadsides, near the fences, along park edges, allotments or cemeteries), and well-developed patches with Leonurus cardiaca were found near fences and in previous rural habitats. In some patches, alien species (Solidago canadensis, S. gigantea, Helianthus tuberosus or Reynoutria japonica) that arrived in Poland after the 15th century and became permanently established in natural and seminatural habitats (kenophytes) had a relative abundance of more than 50%.
The RLQ analysis enabled us to distinguish five responsive groups of species that reflects fertility (N, P, K, MgO, N tot) and disturbance gradients. The first group comprised perennial plants with larger leaf surfaces which connected them with fertile habitats and these species started to flower late during the growing season. Some species could produce fewer but heavier seeds, whereas others could produce more diaspores that are lighter and these species had the ability to spread laterally which enabled them to acquire more space. Species such as Solidago canadensis, S. gigantea, Reynoutria japonica, Asterx salignus, and Helianthus tuberosus resemble this group. In contrast, the second group comprised species with more retentive/conservative traits which was connected with lower fertility and a later disturbance. These species had a smaller stature and leaf surface area, flowered earlier during the year, and produced many light diaspores. The third group comprised some annuals, e.g. Conyza canadensis, Sisymbrium officinale and Hordeum murinum, which germinate in late summer or autumn and they produce vegetative rosettes and accumulate over a wide range of climatic conditions. They can grow rapidly during spring and thus take advantage of the available environmental resources. The fourth group contained perennial species, some of which can form a persistent seed bank that produces large numbers of light diaspores with a low terminal velocity. This selection facilitates species to find suitable conditions for establishment and maintenance in urban areas. These species colonized former wastes dumps and sites that are susceptible to erosion. Lastly, the fifth group comprised annual and biennial species that produce a large number of seeds with a high terminal velocity or they possess the ability to spread laterally (e.g. Artemisia annua, Atriplex patula, Impatiens parviflora).