This study investigated the effects of urbanization on the spatial distribution, sources, and levels of heavy metals pollution in urban soils of the city of Belgrade. A total of 126 composite topsoil (0–10 cm) and subsoil (10–40 cm) samples was collected within four urban zones (central, suburban, external, and rural) of Belgrade and analysed for content, spatial distribution, sources, and pollution indices using statistical methods including descriptive statistics, correlation matrix, and Principal Component Analysis (PCA). Concentration levels of zinc (Zn), copper (Cu), cadmium (Cd), chromium (Cr), and nickel (Ni) in the soil of urban zones in Belgrade were found to be significantly higher in the central and suburban zones compared to the external and rural ones. The spatial variance and the general trend of heavy metals accumulation in the soil were found to be along the urban–rural gradient. The topsoil concentration levels for the same elements were higher compared to the subsoil concentration levels for the same elements in all urban zones, except for the external and the rural zones. These results indicate the need for the implementation of urban soils pollution monitoring according to specific urban zones to provide an applicable basis for the development of plans and strategies concerning urban soil use management for the purpose of the sustainable urban development.

The species Aster lanceolatus occupies a significant position in the world and European lists of invasive species. Its spreading potential is a hazardous factor to the biodiversity in many countries. There are no relevant data on the wider proportion of this species in the area of Belgrade. The sites of Aster lanceolatus are annual or pioneer communities along the water courses, abandoned and neglected areas, forest margins, moist meadows. The study areas are located near a choice of water courses in Belgrade. The aim of the study was to assess the species ecology and population density, synecological interrelationships among the coenobionts of the communities in which it occurs, and also to map its the habitats. The study of population density was performed on the supplemented and partially modified 'CPS SKEW' form, applied in West European countries, by the principle of squares. The species was determined by standard floristic method, and the species location by GPS system. It was concluded that Aster lanceolatus was dominant and wild at all study sites. The individuals and populations are especially numerous on the river islands Ada Ciganlija and Veliko Ratno Ostrvo, along the stream Kumodrsaki Potok and the Danube left bank, where the number of individuals per squares is above 1300 and the degree of coverage is 100%. Its spreading potential is conditioned by the species biology, and the expansiveness by climate changes, anthropogenic impacts and the competitive interrelationships.

The aim of this paper was to examine how the heavy metals cadmium (Cd) and lead (Pb) influence the germination and early growth of seedlings of the fast-growing tree species Ulmus pumila L. Seeds were germinated and seedlings were hydroponically grown in a solution with Cd-nitrate and Pb-nitrate at concentrations of 20 ?M, 50 ?M and 90 ?M. Our results show that seeds can germinate in the presence of these two heavy metals at all of the applied concentrations with no significant reduction in qualitative (germination capacity, germination energy) or quantitative (germination intensity, mean germination period) germination parameters as compared to the controls. Early seedling development was also possible at higher concentrations of both heavy metals. Cd reduced hypocotyl length, but not significantly the length of radicles. Pb did not influence hypocotyl length and stimulated radicle length significantly (95%). These results could mark a step forward in defining the tolerance of U. pumila to the presence of Cd and Pb, and to the possibility of using this fast-growing tree which is resistant to different abiotic and biotic stresses, for phytoremediation or soil reclamation purposes.

Invasive species Aster lanceolatus grows on moist habitats on the whole territory of Serbia. In Belgrade, this species is recorded with a higher degree of presence at a number of localities. With the aim to investigate the community in which this species is dominant, the wide area of Serbia was researched, and 8 localities on the territory of Belgrade were chosen for the analysis of the community. Floristic structure of the community was determined by the standard Braun-Blanquet method (1964), phytogeographical analysis was performed according to Gajic (1980, 1984), and determination of life forms according to Raunkier (Ellenberg, Mueller-Dombois, 1967). pH soil analysis and electric conductivity (EC) were performed at all investigated localities. It was established that the community dominates the moist habitats of Belgrade. It is composed of 104 species and among them Aster lanceolatus Willd., Cichorium intybus L., Agropyrum repens (L.) Beauv., Calystegia sepium (L.) R. Br., Cirsium arvense (L.) Scop., Symphytum officinale L. and Rumex obtusifolius L. are the most frequent. In relation to life forms, the community has hemicriptophytes character, and in relation to phytogeography Euroasian and Middle Europaean floral elements are dominant, with a high presence of cosmopolitan and adventive floral elements. On the locialities Veliko Ratno ostrvo (island) and Makis, EC values point to the fact that the amount of nutrient in the soil is higher than at other localities.