This paper presents research results on forest decline in Serbia. The results were obtained through monitoring defoliation of 34 tree species at 130 sample plots during the period from 2004 to 2018. This research aimed to determine whether the occurrence of defoliation and tree mortality were caused by drought. Defoliation was assessed in 5% steps according to the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) methodology. All the trees recorded as dead were singled out, and annual mortality rates were calculated. To determine changes in air temperature and precipitation regimes during the study period, we processed and analysed climatic data related to air temperature and precipitation throughout the year and in the growing season at 28 main weather stations in Serbia. Tree mortality patterns were established by classifying trees into three groups. The first group of trees exhibited a gradual increase in defoliation during the last few years of monitoring, with dying as the final outcome. The second group was characterised by sudden death of trees. The third group of trees reached a higher degree of defoliation immediately after the first monitoring year, and the trees died after several years. Tree mortality rates were compared between years using the Standardised Precipitation Evaporation Index (SPI) and the Standardised Precipitation Evapotranspiration Index (SPEI), the most common methods used to monitor drought. The most intensive forest decline was recorded during the period from 2013 to 2016, when the largest percentage of the total number of all trees died. According to the annual mortality rates calculated for the three observation periods (2004–2008, 2009–2013, and 2014–2018) the highest forest decline rate was recorded in the period from 2014 to 2018, with no statistically significant difference between broadleaved and coniferous tree species. As the sample of coniferous species was small, the number of sample plots should be increased in order to achieve better systematic forest condition monitoring in Serbia. The analysis of the relationship between defoliation and climatic parameters proved the correlation between them. It was noted that the forest decline in Serbia was preceded by an extremely dry period with high temperatures from 2011 to 2013, supporting the hypothesis that it was caused by drought. We therefore conclude that these unfavourable climatic conditions had serious and long-term consequences on forest ecosystems in Serbia.

In the second half of the twentieth century, the concept of indeterminacy in architecture emerged to address the realities of chance and change, with the megastructure representing a critical point of this ambition. As the aims of indeterminate architectural approaches align with current sustainable development goals, this study hypothesises this design concept as the basis for the sustainability of structures built within its framework. Through a case study of Spens, a socialist megastructure in Novi Sad, Serbia, the paper explores the potentials of megastructures in relation to requirements for more sustainable cities. Firstly, it evaluates Spens’ current social sustainability through focus group discussions analysing sense of community, place, and wellbeing. Findings demonstrate a clear recognition of Spens’ spatial qualities among users. Secondly, the paper examines the future environmental sustainability of Spens, focusing on strategies that enhance user wellbeing and urban life as a point of overlap between social and environmental sustainability, using the Green Space Factor (GSF) and Urban Greening Factor (UFG). Results reveal the significant yet underutilised potential for greening. The paper highlights the long-term societal value of such structures and strategies for leveraging their concepts for their sustainable adaptation rather than replacement amid ongoing retrofit or replacement debates.

The paper presents the results of the analysis dealing with the impact of plant fertilisation in the first year after planting on the leaf morphological characteristics. The analysis was conducted within the research into the potential introduction and adaptation of paulownia to different sites in Serbia. The results related to the effects of fertilisation on the quality of plant leaves are useful for the cultivation of certain types of soil where the morphometric analysis of leaves reveals structure-function relationships, i.e., more detailed indicators of the species' adaptability. The research was conducted in two localities. Sample plots with Paulownia elongata S. Y. Hu. and Paulownia fortunei Seem. Hemsl. were established in Obrenovac and Pambukovica, where leaf material was collected for laboratory analysis. The following morphometric leaf characteristics were measured: leaf area, leaf perimeter, leaf lamina length, central nerve length, maximum leaf width, leaf width at 1 cm from the base of the leaf, petiole length, distance between the 3rd and 4th nerve, the number of nerves to the left side of the midrib, and the number of veins to the right side of the midrib. The obtained results of leaf morphometric measurements were statistically processed in the Statgraphics software. Based on the results of measuring the leaf morphometric characteristics, fertilisation has a positive effect on the size of the leaves of the studied paulownia species.

A visual assessment of tree conditions is essential for public safety and health because urban trees increase attractiveness and provide other benefits, including reducing global warming and air filtration. Unhealthy or damaged trees pose a concern, emphasizing the importance of comprehensive inspections to identify hazards such as decay or dead branches. The assessment of the trees within the green infrastructure of the brownfield in Belgrade, Serbia, indicated that 35.1% of the examined trees failed to satisfy the basic preservation standards, emphasizing the necessity for proactive strategies for management.

Urban greenery, consisting of tree lines, parks and park forests, plays an important role in improving the aesthetics and general well-being of the urban environment. This study focuses on Stromovka Park in České Budejovice and examines the health status of various tree species. The research spans the period from 2021 to 2022 and uses the route method to monitor the occurrence of biotic pests and pathogens, especially mites and insects. Several economically important organisms were identified in the study, including Aceria fraxiniflora (Felt, 1906), Byctiscus betulae (Linnaeus, 1758), Curculio glandium Marsham, 1802, Eriophyes inangulis Nalepa, 1919, Fomes fomentarius (L.) Fr. 1849, Halyomorpha halys (Stål, 1855), Ips typographus (Linnaeus, 1758), Lymantria dispar (Linnaeus, 1758), Loranthus europaeus Jacq., Oxycarenus lavaterae (Fabricius, 1787), Pemphigus spyrothecae Passerini, 1856, Phyllonorycter issikii (Kumata, 1963), Polygraphus poligraphus (Linnaeus, 1758), Prociphilus fraxini (Fabricius, 1777), Rhytisma acerinum Schwein., (1832), Sacchiphantes viridis (Ratzeburg, 1843) and Tetraneura ulmi (Linnaeus, 1758). While most of these organisms showed normal, natural abundance values, increased values were observed in A. fraxiniflora, E. inangulis and O. lavaterae. The application of holistic plant protection principles, from proper cultivation and species selection to monitoring and control measures, remains crucial for maintaining the vitality and longevity of urban green spaces exposed to various biotic and abiotic stress factors.