Drought tolerance is becoming an increasingly important criterion for the selection of tree species, especially in urban areas characterized by low water availability. Apart from drought tolerance, the introduction of non-native species should be considered for new planting programs under such conditions to enhance the resilience of urban forests. The present study is aimed at evaluating the in situ physiological responses of Magnolia grandiflora and Magnolia × soulangeana to severe drought that frequently occurs in urban environments in the Southeastern Europe. Transpiration rate, stomatal conductance, intercellular CO2 concentration, water-use efficiency and intrinsic water-use efficiency showed notable differences both between species and between the measured periods (wet and dry). Among the chlorophyll a fluorescence parameters, effective photochemical quantum yield of PS II, quantum yield of light-induced non-photochemical fluorescence quenching, quantum yield of non-regulated heat dissipation, fluorescence emission and index of susceptibility of leaves to light stress revealed significant differences both between the two species and the periods of measurements. The reduction of net photosynthesis in both magnolia species occurs as the result of non-stomatal limitation obtained by the reduction of electron transport rate coupled with simultaneous increase in intercellular CO2 concentration. Moreover, M. grandiflora was the species less vulnerable to water shortage conditions, while M. soulangeana exhibited a photosynthetic capacity sensitive to drought-induced stress. M. grandiflora can therefore be considered as a promising alternative to M. soulangeana for urban sites under the predicted climate change scenarios.

Quercus robur L. is one of the most valued tree species of deciduous temperate forests. However, in the last decade, serious oak declines and loss of adaptation plasticity have been reported throughout Europe as a consequence of drought. Therefore, the aim of the present study was to define the adaptation potential of five Q. robur half-sib lines from the UNESCO Biosphere Reserve Mura-Drava-Danube to drought, using physiological, anatomical and biometrical traits. Half-sib lines that exhibited drought tolerance had particular suites of trait expression regarding biometrical traits (seedling height, root length, root to shoot ratio of dry mass and specific leaf area), leaf stomatal traits (stomatal density per mm², stomata guard cell length and width, stomatal aperture length and width) and leaf structural traits (adaxial epidermis thickness, palisade parenchyma thickness, spongy parenchyma thickness, lamina thickness). All of the observed parameters of chlorophyll a fluorescence were shown to be good indicators of short-term and severe drought. For the selection of drought-tolerant half-sib lines, all studied chlorophyll a fluorescence parameters associated with the heat dissipation of light energy (coefficient of non-photochemical quenching, quantum yield of regulated energy dissipation, Stern-Volmer type non-photochemical fluorescence quenching) and one parameter related to photochemical dissipation of light energy (effective quantum yield (efficiency) of PS II photochemistry) were proven to be suitable. On the other hand, the coefficient of photochemical quenching, coefficient of photochemical fluorescence quenching assuming interconnected photosystem II antennae and electron transport rate were not suitable for distinguishing the different responses of the studied half-sib lines under drought. The importance of results of the present study is in the selection of drought-tolerant Q. robur half-sib lines for future reforestation programs, particularly in protected areas with sensitive forest management and restricted activities for mitigation of the adverse effects of climate changes.

Aim of study: In the present paper the nature and level of co-dependence between leaf functional traits and intrinsic water-use efficiency (WUEi) were studied in one-year-old Quercus robur L. seedlings, grown in a common garden experiment under moderate drought conditions. The study was established to identify those traits that might potentially be utilized to improve leaf-level WUEi, and therefore be used in breeding programmes to enhance drought adaptation of Q. robur.Area of study: The study was carried out at the common garden site within the UNESCO Biosphere Reserve Mura-Drava-Danube.Material and methods: The study involved one-year-old seedlings of eight half-sib lines of Q. robur. Eighteen leaf parameters were analyzed; i.e. physiological, biochemical, morphological and anatomical. The data were processed using multivariate statistical methods: a) principal component analysis, b) stepwise regression analysis, and c) path coefficient analysis.Main results: The results showed that leaf stomata traits, particularly stomatal density (SD), and leaf dry mass per unit leaf area (LMA) were the most important traits, closely associated with WUEi. Stomatal density achieved the highest score on PC1 (0.825), in which WUEi had the highest loading (0.920), as well. SD was also included first in stepwise regression model.Research highlights: These results demonstrate that under moderate water stress WUEi in Q. robur half-sib lines were mainly the result of the plants’ structural acclimation to surrounding environmental conditions. Keywords: Quercus robur L.; half-sib line; intrinsic water-use efficiency; leaf functional traits.

Key message: This genomic dataset provides highly variable SNP markers from georeferenced natural Quercus petraea (Matt.) Liebl. populations collected in Bulgaria, Hungary, Romania, Serbia, Bosnia and Herzegovina, Kosovo* and Albania. These SNP loci can be used to assess genetic diversity, differentiation, and population structure, and can also be used to detect signatures of selection and local adaptation. The dataset can be accessed at https://doi.org/10.5281/zenodo.3908963/ (Tóth et al.2020). Associated metadata available at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/b6fee4fa-01e9-44d0-92f5-ad19379f9693.

The aim of the present study was to evaluate the effect of one of the most important foliar diseases, powdery mildew, on the leaf physiological traits of Quercus robur L. using chlorophyll a fluorescence parameters in combination with parameters of leaf gas exchange. For this purpose, greenhouse semi-controlled experiment was conducted with 25 one-year-old seedlings kept in optimal conditions, and the same number of seedlings infected with the mentioned pathogen. Measurements were carried out when the coverage of epiphytic micelia visually reached more than 75% of the surface of leaves in the infected seedlings. The results of gas exchange measurement showed that Erysiphe alphitoides (Griffon and Maubl.) U. Braun and S. Takam caused a significant reduction of net photosynthesis (A) and a significant increase in substomatal CO2 concentration (Ci). Furthermore, considering the fast kinetics of chlorophyll a fluorescence, all of the observes parameters were significantly affected by oak powdery mildew. On the other hand, pulse amplitude modulated fluorescence parameters were mildly affected, with only minimal (Fo?) and maximal (Fm?) fluorescence of dark adopted leaves showing significant difference. This study presented the possibility of usage and the effectiveness of chlorophyll a fluorescence parameters in detection the severe stress conditions, on the example of leaves infected with oak powdery mildew over 75%. Some additional studies should be conducted in the future to determine the possibility of usage and the effectiveness of the observed fluorescence parameters of fast kinetics in detection of mild and early stress.

European beech (Fagus sylvatica L.) forests are one of the largest natural renewable reservoirs of stored carbon in Europe, as well as in the Balkans and Serbia. A number of factors have been identified which influence the state of stored carbon, but a unique influence can be expected from the degree of stand preservation and the history of forest management. In the present paper, the influence of the preservation of stands and management methods on the state of ecosystem carbon (biomass carbon and soil carbon) were analyzed in beech forests situated at the Fruška Gora Mountain, Serbia. The research was conducted in three stands that were managed in the past in three different ways: a virgin forest without any management, a high stand and a coppice stand. The stored biomass carbon and soil carbon was estimated using standard methods that have been previously proven useful in Europe for the last decades. Above-ground biomass was also assessed using remote sensing. The results show a significant impact of conservation and management history on the stock of stored biomass carbon and soil carbon, but also on their mutual relationship. This research initiates that moderate management measures and the application of management systems based on the principles of continuous cover forestry (selective and group cutting) are, in addition to their well-known advantages, more efficient in carbon storage than the application of systems with surface management (clear and shelterwood cutting).