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This study investigates the impact of organic matter from Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) on the amount and composition of humus in acid brown soil in a climatoregional beech forest (Fagetum moesiacae montanum B. Jov. 1967 s.l.) on Mt. Maljen. To accomplish this objective, we performed a one-year litterbag decomposition experiment with litterfall from Fagus moesiaca and Pseudotsuga menziesii. The quantitative and qualitative content of humus and the intensity of the decomposition process of organic mat­ter from beech and Douglas fir were analysed. Less humus was found during the experiment under Douglas fir than under autochthonous beech at the control site, as well as a decreasing trend for humus levels and quality (unfavourable chemical composition). It was concluded that these changes, caused by the effects of the clearcutting of beech and, in the future, of Douglas fir, and the slower decomposition of organic matter from Douglas fir will contribute to further degradation of the beech habitat on Mt. Maljen in terms of productivity. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 451-03-68/2020-14/200007]

The content of radionuclides (40K, 238U, 226Ra, 232Th, and 137Cs) and heavy metals (As, Cd, Cu, and Pb) was determined in samples of soil, vegetables and medicinal plants collected in the period 2007-2017, from two suburban areas of Belgrade – the municipalities of Palilula and Surčin, and Pančevo – the 'Dr Josif Pančić' Institute for the Study of Medicinal Herbs. During the research period, activity concentration of 137Cs in soil decreased from 16 Bqkg–1 to 3.9 Bqkg–1 (Palilula, Belgrade) and from 18 Bqkg–1 to 12 Bqkg–1 (Surčin, Belgrade). Mean activity concentrations of natural radionuclides in the soil were higher than the global aver- age. Trend for heavy metal levels, according to the average concentrations found in the soil, were as follows: Cu >Pb >As >Cd for Palilula, Pb >Cu >As >Cd for Surčin and Dr Josif Pančić' Institute, Pančevo. The obtained results indicate that the industrial pollution has no impact on food production in the study area and that the main anthropogenic source of radionuclides and heavy metals in soil are mineral phosphorous fertilizers, often used in agricultural fields. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR31003 and Grant no. 173018]

Segetal vegetation was studied in the cultivated areas of southern Srem with the aim of analyzing its taxonomy, phytocoenology, syntaxonomy and phytogeography, as well as determining to what extent ecological factors influenced the differentiation of segetal plant communities among row crops, small grain crops and in alfalfa fields. Segetal flora was comprised of 124 plant species, classified into 38 families, of which Asteraceae (28), Fabaceae (10) and Poaceae (10) contained the greatest number of species. Three associations were selected based on phytocoenological analysis: Polygonetum convolvulo-avicularis, Consolido-Polygonetum avicularis and Lolio-Plantaginetum majoris, as well as five lower syntaxa (subassociations and facies). Crop type, moisture, habitat acidity (pH), temperature and anthropogenic factors had the greatest impact on the ecological differentiation of the studied vegetation. The significant presence of non-native species (18) was another consequence of the anthropogenic effects and geographic position of southern Srem, and these, as coenobionts of segetal plant communities and undesirable species, had a significant impact on crop yield. [Projekat Ministarstva nauke Republike Srbije, br. 173018 and III46008]