Genetic diversity of sessile oak populations in the Czech Republic

The sessile oak is a broadleaved tree species of great ecological and silvicultural importance. Oaks are the second most widespread deciduous tree species in the Czech Republic, and ongoing climate change negatively affects the abundant and often monocultural Norway spruce. Therefore, a proportional increase of more resilient tree species such as sessile oak has emerged. This study aimed to depict population genetic diversity when analysing 272 individuals from 10 subpopulations selected across the Czech Republic. Targeted populations were chosen based on the minimal expected human impact on the stand (presumably autochthonous stands). All individuals were genotyped using 18 polymorphic microsatellite markers (SSRs) assembled into two amplification multiplexes. The high discriminatory power of SSR markers was tested and confirmed by the probability of identity analysis. The genetic differentiation of the subpopulations was low yet significant, quantified by Wright’s F-statistics within the range from 0.012 to 0.029. Based on discriminant analysis of principal components (DAPC), we detected two populations with geographic genetic correlation (the 15^th meridian east being a north-south boundary line) and one with a distinct genetic pattern. We assume that the population might previously be established from seed sources outside the Czech Republic. Moreover, to some extent, our findings advocate the legitimacy of the legislative rules for forest reproductive material (FRM) transfer.

Diversity of ectomycorrhizal fungi associated with Quercus petraea in the national park Fruška gora in the Republic of Serbia

Although sessile oak is one of the most important deciduous forest tree species in Europe, data on the diversity of ectomycorrhizal (ECM) fungi on sessile oaks in the Republic of Serbia are scarce. The aim of this study was to provide the first insight into the diversity of ECM fungi on sessile oak in Serbia. Two sites Info center and Brankovac, located in National Park Fruška gora were chosen. ECM fungi were identified combining morphological and anatomical characterization with molecular analysis of nuclear rDNA internal transcribed spacer (ITS) region. All vital ECM root tips were counted, diversity indices were calculated, and ECM fungi were classified into the exploration types. The granulometric and chemical composition of soil were analyzed as well. At both sites, 26 different ECM fungal taxa were recorded in total, 17 taxa were observed at the site Info center and 12 taxa at Brankovac. ECM communities consisted of a few abundant taxa and a larger number of rare taxa. Lactarius quietus, Cenococcum geophilum, and Tomentella sublilacina were recorded at both sites. High abundance of contact and short-distance exploration types recorded in studied stands suggests that soils are sufficiently rich in total nitrogen and organic matter. Values of diversity indices recorded in studied sessile oak stands from Fruška gora were lower in comparison to those obtained in stands of different oak species across Europe which is likely induced by drought. To get a more thorough insight into the diversity of ECM fungi on sessile oak, research should be continued at more sites and seasonal dynamics should be included.

Significance of current weather conditions for foliar traits of old-growth sessile oak (Quercus petraea Liebl) trees

Key message Sessile oak leaves showed a high degree of plasticity to atmospheric and pedospheric conditions. Abstract The aim of the present study was to elucidate the significance of current weather conditions for foliar traits of adult sessile oak (Quercus petraea), one of the most valuable forest tree species in Central Europe. For this purpose, structural and functional traits were analysed in fully expanded, sun exposed leaves collected in south-west Germany from five old-growth forest stands, representing the meteorological and pedospheric conditions in the growing region, but differing in aridity during the 12 days before harvest in two consecutive years. Across the forest stands, most foliar traits differed significantly between wet and dry weather conditions before harvest as indicated by partial least square discriminant analysis (PLS-DA). These traits included fresh weight/dry weight ratio, leaf hydration, leaf-C content, leaf-C/N ratio, structural N, soluble protein-N, total amino acid-N, cell wall composition, numerous specific amino acids as well as soluble sugar content. Structural biomass, δ13C signature, total N and total C as well as H2O2 contents were not affected by the weather before harvest. These results indicate a high plasticity of the foliar metabolism of drought-tolerant sessile oak to current weather conditions. They also suggest that sessile oak is characterized by a high potential to cope with the growth conditions expected as a consequence of future climate change.

EMPIRICAL USE OF THREE OAK SPECIES IN AFFORESTATION: LESSONS FROM SOWING AND TRANSPLANTING EXPERIMENTS

The effects of different factors on the growth in height and diameter of oak saplings in comparative cultures were estimated: progeny from autumn and spring sowing of acorns (1); growing conditions of pedunculate oak (Quercus robur L.) mother plants (2); the initial planting density of sessile oak (Q. petraea Liebl.) (3); natural lightening level of downy oak (Q. pubescens Willd.) mother plants (4). The pedunculate oak seedlings obtained after spring sowing were characterized by faster growth compared with those obtained from the autumn sowing. The lower growth rate observed in seedlings sown in autumn was due to the prolonged frosty weather during winter, which led to a decrease in acorn viability and progeny vigour. Due to the higher genetic diversity of the progeny obtained from the free-pollinated pedunculate oaks, it is possible that their growth was more intense and stable in comparison to those of saplings obtained from the acorns of isolated trees. The planting under the forest canopy had a clear influence on the growth in height of saplings. At low density levels (1.0 x 1.0 m), the sessile oak saplings benefited from larger availability of soil nutrients and displayed the highest growth, contrasting with those planted at high density (0.5 x 0.5 m). The deep and moderate shading caused a substantial reduction in the growth of downy oak saplings. Therefore, when planting, it is recommended to avoid using fast-growing species, which, due to asymmetric competition, could drastically reduce the growth in height of the downy oak saplings. Prolonged regeneration of the pruned root system following the transplantation process of sessile and downy oak seedlings determined their very slow growth in the first years of life.

Non-chemical treatments to improve the seeds germination and plantlets growth of sessile oak

The current study aimed to investigate the effect of different treatments applied to sessile oak seeds in order to improve the germination features, development and growth of seedlings. The seeds were subjected to electric field, electromagnetic field and γ rays’ treatments. For the electric field study three distinct voltages (10V, 30V and 50V) and three values of exposure time (15 min., 35 min. and 60 min.) were considered. Displaying the seeds in an electric field for 60 minutes increased the germination rate with 58.89%. The highest value for the seedling’s height was obtained when seeds were exposed for 15 minutes at an intensity of 30V. The interaction between the intensity and the timing showed that treating seeds with 30V for 35 minutes improved significantly the seedlings peculiarities. In regard to the electromagnetic field, the seeds were subjected to a single value of electromagnetic field (B=0,4mT; i=0,680 A) and three values of exposure time: 10 min., 20 min. and 30 min. The sessile oak seeds subjected to the electromagnetic field for 20 minutes induced the highest value of germination percentage (90.00%) and germination index (1.81) and those seeds produced plantlets with high diameter (2.69 mm) and with significant differences towards non-treated plants. For γ rays treatments a dosage of 2 Gy induced the highest value of germination percentage (86.67%), of germination index (2.02); of germination energy (7.7); and of germination speed (7.24). A dosage of 6 Gy decreased the values of the same parameters. Our results showed that a dosage of 2 Gy improved also the growth parameters such as plantlets diameter (2.65 mm) and height (11.25 cm). In short, the physical treatments represent an ecological substitute approach towards the chemical substances presently used to improve seeds germination. Using physical treatments for seeds germination and growth of seedlings might be a harmless alternative for environment.

Molecular plasticity to soil water deficit differs between sessile oak (Quercus Petraea (Matt.) Liebl.) high and low water use efficiency genotypes

Background: Water use efficiency (WUE) is an important adaptive trait for soil water deficit. The molecular and physiological bases of WUE regulation in crops have been studied in detail in the context of plant breeding. Knowledge for most forest tree species lags behind, despite the need to identify populations or genotypes able to cope with the longer, more intense drought periods likely to result from climate warming. Results: We aimed to bridge this gap in knowledge for sessile oak (Quercus Petraeae Matt. L.), one of the most ecologically and economically important tree species in Europe, using a factorial design including two genotypes (low and high WUE) and two watering regimes (control and drought). By monitoring the ecophysiological response, we were able to identify groups of genotypes with high and low WUE. We then performed RNA-seq to quantify gene expression for the most extreme genotypes exposed to two watering regimes. By analyzing the interaction term, we were able to capture the molecular strategy of each group of plants for coping with drought. Regardless of water availability, the high WUE genotypes overexpressed genes associated with drought responses, and the control of stomatal density and distribution, and displayed a downregulation of genes associated with early stomatal closure and high transpiration rate. High-WUE genotypes, thus, coped with drought by fine-tuning the expression of genes with known functions in the regulation of stomatal size, density, movement or aperture and transpiration rate. Conclusion: Fine physiological screening of sessile oaks with contrasting WUE, and their molecular characterization i) highlighted subtle differences in transcription between low and high WUE genotypes, identifying key molecular players in the genetic control of this trait, and ii) revealed the genes underlying the molecular strategy that had evolved in each group to cope with water deficit, providing new insight into the value of WUE for adaptation to drought.

Modeliranje višinske in debelinske rasti dominantnih dreves ter ocenjevanje indeksov produkcijske sposobnosti gozdnih rastišč

Modeling the height and diameter growth of trees is an important part of forest management. Growth models provide the basis for determining the thinning regime, target tree dimensions and optimal proportions of developmental phases of forest stands. We developed individual height growth models for dominant Norway spruce (Picea abies (L.) Karst) and European beech (Fagus sylvatica L.) in two forest types (sessile oak-European beech forests and pre-Alpine silver fir-European beech forests). Based on the models, the site productivity index (SPI), defined as the dominant tree height at a diameter of 45 cm, was determined for spruce and beech in both forest types. Based on the diameter increment of the dominant trees, the age of trees in regard to their diameter was calculated, which was the basis for Height-Age modeling. The site productivity index (SPI) of spruce in sessile oak-beech forests and pre-Alpine silver fir-European beech forests is higher than that of beech: 31.3 and 29.7 vs 28.7 and 27.9, respectively. Estimated site indices (SI; dominant tree height at the age of 100 years) in sessile oak- European beech forests and pre-Alpine silver fir-European beech forests were 33.4 and 32.0 for spruce, and 29.0 and 27.0 for beech, respectively. Using the described procedure, it is possible to determine indices of site productivity of spruce and beech (SI and SPI) in the selected forest habitat types. Testing the procedure in other forest types and for other tree species is suggested.

SESSILE OAK FOREST ECOSYSTEMS FROM TRANSYLVANIA IN THE CONTEXT OF CLIMATIC CHANGES

Climatic modelling software was used in order to measure future changes in climatic conditions. The software HYPE can realize prognosis for certain climatic factors responsible for causing extreme climatic phenomena in forest ecosystems. It was applied to study sessile oak forest ecosystems from Transylvania. Sample surfaces were installed, inventoried and followed by simulations of two future climatic scenarios. Two such scenarios were chosen, namely the climatic scenario in which the gas effect concentration will increase moderately (rcp-4.5) and the climatic scenario in which the gas effect concentration will be accentuated (rcp-8.5). The data was then processed and which led to an analysis of the way in which future climatic changes will affect forest ecosystems located in the studied area. After analyzing all three sessile oak stands, we can conclude that the Mediaș stand is the most vulnerable one to both climatic parameters. Future climatic scenarios are necessary for other surfaces located in our country for the same species, as well as for others in order to have a bigger picture of future implications. The best management measures and decisions regarding the installment of future stands can consequently be taken based on these results.