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Wood density is a fundamental functional trait influencing ecological adaptation, hydraulic safety, and timber utilisation in temperate hardwoods. This study investigated variation in wood density (12% moisture) across mature stands of two economically and ecologically vital European oak species, sessile oak [Quercus petraea (Matt.) Liebl.] and English oak (Quercus robur L.), growing in their characteristic vegetation zones in the Czech Republic. We assessed wood density at two heights (at 1.3 m and at the crown base) across six trees per plot and examined its relationship with tree-ring width and height. Results demonstrated statistically significant interspecific differences, with Q. petraea consistently exhibiting higher wood density (721 kg·m−3) than Q. robur (662 kg·m−3) at 1.3 m. Q. petraeashowed a statistically nonsignificant higher density of 710 kg·m−3 at the crown base and an overall average of 717 kg·m−3, whileQ. roburhad densities of 701 kg·m−3 and 669 kg·m−3, respectively. Radial density profiles revealed species-specific patterns, with Q. roburshowing a more uniform density distribution than the pronounced pith-to-bark gradients observed in Q. petraea. Regression analysis indicated that tree-ring width explained only 12–13% of the variance in density, so other anatomical factors, such as latewood proportion and tree-ring structure (number and cell size), should be examined as anatomical drivers of wood-density variation.

Background Expressed Sequence Tags (ESTs) are a source of simple sequence repeats (SSRs) that can be used to develop molecular markers for genetic studies. The availability of ESTs for Quercus robur and Quercus petraea provided a unique opportunity to develop microsatellite markers to accelerate research aimed at studying adaptation of these long-lived species to their environment. As a first step toward the construction of a SSR-based linkage map of oak for quantitative trait locus (QTL) mapping, we describe the mining and survey of EST-SSRs as well as a fast and cost-effective approach (bin mapping) to assign these markers to an approximate map position. We also compared the level of polymorphism between genomic and EST-derived SSRs and address the transferability of EST-SSRs in Castanea sativa (chestnut). Results A catalogue of 103,000 Sanger ESTs was assembled into 28,024 unigenes from which 18.6% presented one or more SSR motifs. More than 42% of these SSRs corresponded to trinucleotides. Primer pairs were designed for 748 putative unigenes. Overall 37.7% (283) were found to amplify a single polymorphic locus in a reference full-sib pedigree of Quercus robur . The usefulness of these loci for establishing a genetic map was assessed using a bin mapping approach. Bin maps were constructed for the male and female parental tree for which framework linkage maps based on AFLP markers were available. The bin set consisting of 14 highly informative offspring selected based on the number and position of crossover sites. The female and male maps comprised 44 and 37 bins, with an average bin length of 16.5 cM and 20.99 cM, respectively. A total of 256 EST-SSRs were assigned to bins and their map position was further validated by linkage mapping. EST-SSRs were found to be less polymorphic than genomic SSRs, but their transferability rate to chestnut, a phylogenetically related species to oak, was higher. Conclusion We have generated a bin map for oak comprising 256 EST-SSRs. This resource constitutes a first step toward the establishment of a gene-based map for this genus that will facilitate the dissection of QTLs affecting complex traits of ecological importance.

In trees, water and sugars are transported by xylem and phloem conduits which are hydraulically linked. A simultaneous study of both flows is interesting, since they concurrently influence important processes such as stomatal regulation and growth. A few mathematical models have already been developed to investigate the influence of both hydraulically coupled flows. However, none of these models has so far been tested using real measured field data. In the present study, a comprehensive whole-tree model is developed that enables simulation of the stem diameter variations driven by both the water and sugar transport. Stem diameter variations are calculated as volume changes of both the xylem and the phloem tissue. These volume changes are dependent on: (i) water transport according to the cohesion–tension theory; (ii) sugar transport according to the Münch hypothesis; (iii) loading and unloading of sugars; and (iv) irreversible turgor-driven growth. The model considers three main compartments (crown, stem, and roots) and is verified by comparison with actual measured stem diameter variations and xylem sap flow rates. These measurements were performed on a young oak (Quercus robur L.) tree in controlled conditions and on an adult beech (Fagus sylvatica L.) tree in a natural forest. A good agreement was found between simulated and measured data. Hence, the model seemed to be a realistic representation of the processes observed in reality. Furthermore, the model is able to simulate several physiological variables which are relatively difficult to measure: phloem turgor, phloem osmotic pressure, and Münch's counterflow. Simulation of these variables revealed daily dynamics in their behaviour which were mainly induced by transpiration. Some of these dynamics are experimentally confirmed in the literature, while others are not.

Quercus robur L., also referred to as “summer oak” or “English oak”, is an esthetically pleasing species, making it an excellent choice for street trees and gardens. Raising Quercus presents several challenges, including its long growth period, delayed germination, and inconsistent emergence. The shoot proliferation and adventitious root formation of Q. robur are crucial for establishing a tissue culture regeneration system and are vital for the successful transplantation of seedlings. To address this, experiments were conducted to assess shoot proliferation and adventitious root formation in Q. robur using various media. The shoot proliferation time, shoot proliferation coefficient, number of rooting strips, and length indicators of roots were recorded. The results indicated that a combination of 0.3 mg/L 6-Benzylaminopurine (6-BA) and 100 mg/L cefotaxime (Cef) was optimal for shoot propagation, while a solution of 0.1 mg/L 1-Naphthaleneacetic acid (NAA) and 1/2 Murashige and Skoog Medium (1/2MS) medium was most effective for root induction. This study has identified the optimal conditions for adventitious root formation and shoot proliferation in Q. robur, providing a basis for further research into propagation, germplasm conservation and genetic transformation techniques.

The present work sheds light on the potentiality of proteins extracted from oak (Quercus robur) leaves to treat both drinking water and industrial oily wastewater. The work was structured in three steps: firstly, oak leaves in powder form were analyzed by FTIR, XRD and SEM, thus showing the presence of proteins acting as bio-coagulants; secondly, an experimental design was conducted. According to the design of experiences based on fractional design (28−4), the highest protein concentration (4.895 mg/g) was obtained for the following operating parameters: no filtration, pH of 12, temperature of 20 °C, stirring speed of 300 rpm, stirring time of 60 min, maceration time of 4 h, centrifugation speed of 400 rpm, centrifugation time of 10 min. Finally, a jar test apparatus was used to study the effects of proteins from oak leaves on the characteristics of both drinking water and industrial oily wastewater. In drinking water, the turbidity was reduced from 15.7 to 4.82 NTU when 0.098 mg/L of oak leaves protein was added, thus satisfying the requirements of the national drinking water standards; whereas, in industrial oily wastewater turbidity, total suspended solids, chemical oxygen demand and organic matter were reduced by 96.87, 89.86, 96.39 and 46.28%, respectively, when 0.538 mg/L of oak leaves protein was added. This study opens new perspectives related to the research and development of organic coagulants applicable to industrial wastewater treatment.

In trees, stem diameter variations are related to changes in stem water content, because internally stored water is depleted and replenished over a day. To confirm this relationship, non-invasive magnetic resonance imaging (MRI) was combined with point dendrometer measurements in three actively transpiring oak (Quercus roburL.) trees. Two of these oak trees were girdled to study the stem increment above the girdling zone. MRI images and micrographs of stem cross-sections revealed a close link between the water distribution and the anatomical features of the stem. Stem tissues with the highest amount of water were physiologically the most active ones, being the youngest differentiating xylem cells, the cambium and the youngest differentiating and conductive phloem cells. Daily changes in stem diameter corresponded well with the simultaneously MRI-measured amount of water, confirming their strong interdependence. MRI images also revealed that the amount of water in the elastic bark tissues, excluding cambium and the youngest phloem, contributed most to the daily stem diameter changes. After bark removal, an additional increase in stem diameter was measured above the girdle. This increase was attributed not only to the cambial production of new cells, but also to swelling of existing bark cells. In conclusion, the comparison of MRI and dendrometer measurements confirmed previous interpretations and applications of dendrometers and illustrates the additional and complementary information MRI can reveal regarding water relations in plants.

Very little is known about the impact of flooding and ground saturation on ectomycorrhizal fungi (EcM) and increasing flood events are expected with predicted climate change. To explore this, seedlings inoculated with the EcM species Tuber aestivum were exposed to a range of flood durations. Oak seedlings inoculated with T. aestivum were submerged for between 7 and 65 days. After a minimum of 114-day recovery, seedling growth measurements were recorded, and root systems were destructively sampled to measure the number of existing mycorrhizae in different zones. Number of mycorrhizae did not display correlation with seedling growth measurements. Seven days of submersion resulted in a significant reduction in mycorrhizae numbers and numbers reduced most drastically in the upper zones. Increases in duration of submersion further impacted mycorrhizae numbers in the lowest soil zone only. T. aestivum mycorrhizae can survive flood durations of at least 65 days. After flooding, mycorrhizae occur in higher numbers in the lowest soil zone, suggesting a mix of resilience and recovery. The results will aid in furthering our understanding of EcM but also may aid in conservation initiatives as well as providing insight for those whose livelihoods revolve around the collection of EcM fruiting bodies or cropping of the plant partners.

The oaks Quercus robur L. and Quercus rubra L. are grown worldwide. The oak fruits (acorns) fallen on the ground during the autumn are usually considered as unusable, although some possible applications have been reported. In the present study, the possible recovery of tocopherols from acorns of two oak species Q. rubra (n = 14) and Q. robur (n = 15) was evaluated. Four tocopherols (Ts) (α-T, β-T, γ-T, and δ-T) in the oak fruits of Q. rubra and Q. robur were identified. The Q. robur acorns had abundant γ-T (28.18 ± 6.7 mg/100 g dw), while in Q. rubra β-T was predominant (17.28 ± 2.91 mg/100 g dw), nearly 95 and 90% of total detected tocopherols, respectively. The variability of tocopherol levels within the same species was lower for Q. rubra (16.5%) and higher for Q. robur (23.4%). The principal component analysis, applied to four tocopherol homologues, confirmed their feasibility to distinguish two strictly separated groups: one for species Q. rubra and the other for Q. robur. The predominance of β-T in Q. rubra acorns is a unique finding in the plant world; therefore, acorns of this oak species can be used as an unconventional natural source of this rare tocopherol homologue.

Failed oak regeneration is widely reported in temperate forests and has been linked in part to changed disturbance regimes and land‐use. We investigated if the North American fire–oak hypothesis could be applicable to temperate European oaks (Quercus robur, Quercus petraea) using a replicated field experiment with contrasting canopy openness, protection against ungulate browsing (fencing/no fencing), and low‐intensity surface fire (burn/no burn). Survival, relative height growth (RGRH), browsing damage on naturally regenerated oaks (≤300 cm tall), and changes in competing woody vegetation were monitored over three years. Greater light availability in canopy gaps increased oak RGRH (p = .034) and tended to increase survival (p = .092). There was also a trend that protection from browsing positively affected RGRH (p = .058) and survival (p = .059). Burning reduced survival (p < .001), nonetheless, survival rates were relatively high across treatment combinations at the end of the experiment (54%–92%). Most oaks receiving fire were top‐killed and survived by producing new sprouts; therefore, RGRH in burned plots became strongly negative the first year. Thereafter, RGRH was greater in burned plots (p = .002). Burning altered the patterns of ungulate browsing frequency on oaks. Overall, browsing frequency was greater during winter; however, in recently burned plots summer browsing was prominent. Burning did not change relative density of oaks, but it had a clear effect on competing woody vegetation as it reduced the number of individuals (p < .001) and their heights (p < .001). Our results suggest that young, temperate European oaks may respond similarly to fire as their North American congeners. However, disturbance from a single low‐intensity fire may not be sufficient to ensure a persistent competitive advantage—multiple fires and canopy thinning to increase light availability may be needed. Further research investigating long‐term fire effects on oaks of various ages, species‐specific response of competitors and implications for biodiversity conservation is needed. We investigated if the North American fire–oak hypothesis could be applicable to temperate European oaks. Although a low‐intensity fire reduced oak seedling survival, survival rates were relatively high across treatment combinations (54%–92%) and relative height growth was greater in burned plots after 2 years. Burning did not change relative density of oaks, but it had a clear effect on competing woody vegetation as it reduced the number of individuals and their heights, especially for conifers.

Key messageExtremely high fine root mortalities were observed under drought in 2018, increasing fine root mortality in young trees could be explained by differences in root distribution compared to old trees.Juvenile trees in floodplains are prone to high mortality leading to a low success in reforestation in these habitats. One of the reasons contributing to high mortality of juvenile trees could be limited water and nutrient uptake due to a high level of fine root mortality, especially during summer droughts on higher terraces of floodplains. Strategies of different tree species in hardwood floodplain forests (HFFs) on keeping fine roots alive are still poorly understood. During the record-breaking summer drought of 2018, we examined the relationship between tree age and fine root dynamics of Quercus robur and Ulmus laevis along the Elbe River in Germany. Root area index (RAI), live root density (LRD) and relative root mortality (RRM) of young and old Q. robur and U. laevis were analysed by taking soil cores three times during the progression of a summer drought. Old oaks had a lower RAI in the upper soil than young oaks, while RAI of elms did not differ between young and old trees. RRM was very high during summer reaching more than 100% on average. RRM of young trees of both species increased with increasing drought during summer, while RRM of old trees did not change. We argue that differences in the response of RAI between oaks and elms reflect the sink competition between growing deep roots and shallow roots, which is pronounced in oaks due to their characteristic tap root system. Differences in root distribution patterns and the ability to perform hydraulic redistribution may explain the differences in RRM between trees of different species and ages.