Petraea Trees Research Articles

Quercus petraea (Matt.) Liebl. from the Thayatal National Park in Austria: Selection of Potentially Drought-Tolerant Phenotypes

The increasing demand for climate-adapted seeds and planting material poses a challenge due to the limited availability, particularly for tree species such as oaks. National parks, known for their large-standing diversity and a wide range of habitats, can serve as valuable sources for identifying trees suitable for both the initiation of tree breeding and conservation strategies. This study aimed to identify valuable forest genetic resources of the Thayatal National Park in Austria by selecting potentially drought-tolerant phenotypes. For this purpose, we selected 404 mature trees of Quercus petraea (Matt.) Liebl. from eight populations growing on medium to dry sites in eight populations. Further, we characterized them for autochthony, genetic structure, genetic diversity using genetic markers (plastid- and nuclear-SSRs) and estimated their age. Finally, we applied wood core analysis to estimate tree response to historical drought events to identify the possible drought-tolerant phenotypes. The age of the trees ranged from 29 to 245 years (as of the year 2023). All Q. petraea trees were inhabiting a plastid haplotype 17a, autochthonous for this area. Nevertheless, the genetic structure estimated by ten nuSSRs revealed a pronounced structure in the dataset, largely caused by young trees exhibiting lower genetic diversity. A total of 85 elite potentially drought-tolerant trees were finally selected based on their morphological response (resistance, recovery ability, resilience, and relative resilience) to three historical drought events (1992–1994, 1947, 1917). The intrinsic water use efficiency and its difference (iWUE and DWiWUE), estimated by isotope analysis of δ13C of latewood in wet (1987) and dry (1994) years, did not correlate with any of the drought response traits (Rt, Rc, Rs, rRs). We discuss the further use of the selected oak trees for the establishment of seed stands and orchards to enhance seed production and the integration of other omics approaches, such as large-scale high-throughput plant phenotyping (HTPP) and transcriptomics, for in-depth analyses of drought tolerance of selected phenotypes.

First dendrochronological studies of Quercus protoroburoides

Quercus protoroburoides Donchev and Bouzov ex Tashev and Tsavkov (Rila oak) is a species with extremely limited and localized distribution. It is found only on several locations on slopes above Rila Monastery in Rila Mountains (Bulgaria) at elevations between 1500 m and 1750 m a.s.l. The trees are in small groups or scattered, usually situated on ridges slightly higher than the local population of sessile oak (Quercus petraea (Matt.) Liebl.) and above mixed fir-beech forests. The species was first discovered and described in 1968 by Boris Buzov, but was officially validated in 2017 by Tashev and Tsavkov. Up to this moment there were no dendrochronological studies of the species and there is general lack of data on how climate affects its growth. Our aim was to contribute to filling this knowledge gap. In our study we analyzed 42 series (22 trees) from Q. protoroburoides from two locations (Drushlyavitsa and Brichebor) and compared them to cores from Q. petraea from the same region. The Rila oak trees varied in age from 30 to 170 years. Nearly half of them were about 50 years old. The composed tree-ring chronology spans from 1856 to 2019 with more than 5 included series after 1870. The sessile oak trees were generally older and the chronology spanned from 1743, having more than 4 series after 1786. The climate-growth analysis with local and gridded data revealed positive effects on growth of previous August and current April-June precipitation, positive correlations with previous May-June temperatures and negative with August temperatures. Most of the pointer years with low growth were characterized by extreme climate conditions, such as summer droughts, unusually cold summers or delayed start of the vegetation period due to late frost events at the end of May or early June. Our data indicate that Q. protoroburoides and Q. petraea trees at this unusually high location for oaks are sensitive to climate conditions including summer droughts.

Impact of Gene Flow and Introgression on the Range Wide Genetic Structure of Quercus robur (L.) in Europe

As for most other temperate broadleaved tree species, large-scale genetic inventories of pedunculate oak (Quercus robur L.) have focused on the plastidial genome, which showed the impact of post-glacial recolonization and manmade seed transfer. However, how have pollen mediated gene flow and introgression impacted the large-scale genetic structure? To answer these questions, we did a genetic inventory on 1970 pedunculate oak trees from 197 locations in 13 European countries. All samples were screened with a targeted sequencing approach on a set of 381 polymorphic loci (356 nuclear SNPs, 3 nuclear InDels, 17 chloroplast SNPs, and 5 mitochondrial SNPs). In a former analysis with additional 1763 putative Quercus petraea trees screened for the same gene markers we obtained estimates on the species admixture of all pedunculate oak trees. We identified 13 plastidial haplotypes, which showed a strong spatial pattern with a highly significant autocorrelation up to a range of 1250 km. Significant spatial genetic structure up to 1250 km was also observed at the nuclear loci. However, the differentiation at the nuclear gene markers was much lower compared to the organelle gene markers. The matrix of genetic distances among locations was partially correlated between nuclear and organelle genomes. Bayesian clustering analysis revealed the best fit to the data for a sub-division into two gene pools. One gene pool is dominating the west and the other is the most abundant in the east. The western gene pool was significantly influenced by introgression from Quercus petraea in the past. In Germany, we identified a contact zone of pedunculate oaks with different introgression intensity, likely resulting from different historical levels of introgression in glacial refugia or during postglacial recolonization. The main directions of postglacial recolonization were south to north and south to northwest in West and Central Europe, and for the eastern haplotypes also east to west in Central Europe. By contrast, the pollen mediated gene flow and introgression from Q. petraea modified the large-scale structure at the nuclear gene markers with significant west–east direction.

Tree Shape Variability in a Mixed Oak Forest Using Terrestrial Laser Technology: Implications for Mating System Analysis

The accuracy of the description regarding tree architecture is crucial for data processing. LiDAR technology is an efficient solution for capturing the characteristics of individual trees. The aim of the present study was to analyze tree shape variability in a mixed oak forest consisting of four European white oak species: Quercus petraea, Q. frainetto, Q. pubescens, and Q. robur. Moreover, we tested for association between tree shape and individual heterozygosity and whether oak trees identified as pollen donors in a previous genetic study have a larger size in terms of crown and trunk characteristics than non-donors. The woody structure of a tree was defined by the quantitative structure model (QSM) providing information about topology (branching structure), geometry, and volume. For extracting the 3D point clouds a high-speed 3D scanner (FARO FocusS 70) was used. The crown variables were strongly correlated to each other, the branch volume being influenced by branch length, maximum branch order, and the number of branches but not influenced by diameter at breast height (DBH), trunk length, trunk volume, or tree height. There was no relationship between the individual heterozygosity based on nuclear microsatellite genetic markers and crown and trunk characteristics, respectively. Branch volume, total area, DBH, trunk volume, and the total volume of tree were significantly larger in pollen donors compared to non-donor Q. petraea trees. Thus, the mean branch volume was more than three times higher. Pollen donors had nearly two and half times larger total area in comparison to non-donor individuals. Our results suggest that a thorough characterization of tree phenotype using terrestrial laser scanning may contribute to a better understanding of mating system patterns in oak forests.

Decreasing stand density favors resistance, resilience, and recovery of Quercus petraea trees to a severe drought, particularly on dry sites

Key message Decreasing stand density increases resistance, resilience, and recovery ofQuercus petraeatrees to severe drought (2003), particularly on dry sites, and the effect was independent of tree social status. Context Controlling competition is an advocated strategy to modulate the response of trees to predicted changes in climate. Aims We investigated the effects of stand density (low, medium, high; relative density index 0.20, 0.53, 1.04), social status (dominant, codominant, suppressed), and water balance (dry, mesic, wet; summer water balance - 182, - 126, - 96 mm) on the climate-growth relationships (1997-2012) and resistance (Rt), resilience (Rs), and recovery (Rc) following the 2003 drought. Methods Basal area increments were collected by coring (269 trees) in young stands (28 +/- 7.5 years in 2012) of sessile oak (Quercus petraea) in a French permanent network of silvicultural plots. Results We showed that the climate-growth relationships depend on average site-level water balance with trees highly dependent on spring and summer droughts on dry and mesic sites and not at all on wet sites. Neither stand density nor social status modulated mean response to climate. Decreasing stand density increased Rt, Rs, and Rc particularly on dry sites. The effect was independent of tree social position within the stand. Conclusion Reducing stand density mitigates more the effect of extreme drought events on drier sites than on wet sites.

Comparative Studies Of Oak (Quercus Petraea L.) Reservations Within Cluj Forestry

In Romania it is necessary a sustained effort to extend the forest areas through artificial regeneration. The purpose of this study is to show the correlation between the heights and diameters of Quercus petraea trees from seed reserves and their seed production. They were chosen 80 trees situated in four Quercus petraea seed reserves of Cluj County. The trees selected were located at a distance of 30 meters from each other. It has been found that the two measured variables (core diameter and trees height) are direct positive correlated, in the sense that increasing the value of a variable and thus leads to an increase in the other. Choosing trees with special qualities have great importance when it comes to transmitting genetic gain new generations. Comprehensive analysis of stationary and vegetation characteristics result in reproductive material with significant values as seeds quality and adaptability.

Physiological significance of forest tree defoliation: Results from a survey in a mixed forest in Tuscany (central Italy)

A survey of tree crown defoliation and leaf physiological traits (chlorophyll a fluorescence, nitrogen content, and stable carbon isotope composition) was carried out in the thermophilous deciduous forests in Tuscany (central Italy). In contrast to large scale surveys, where variation in defoliation can be associated with the change in environmental conditions, in a limited homogenous area the defoliation of co-existing tree species may have different significance and depends on the interaction between the characteristics of each individual species with biotic stress and environmental conditions. The survey included measurements of structural and vegetational characteristics of the forest stands, such as Leaf Area Index (LAI), basal area and tree diversity, which is expressed as the Shannon diversity index. The five tree species studied (Castanea sativa, Quercus cerris, Quercus ilex, Quercus petraea and Ostrya carpinifolia) showed species-specific crown conditions and physiological features relative to stand structure and diversity. The shape of the crowns and their area (LAI) affected forest defoliation. Tree diversity reduced defoliation in C. sativa, which was the tree species most affected by defoliation, and likewise for Q. ilex. Chlorophyll a fluorescence parameters showed lower photosynthetic efficiency in defoliated C. sativa, O. carpinifolia and Q. petraea trees. Similarly, foliar nitrogen content decreased in defoliated C. sativa and O. carpinifolia trees, whereas δ13C was higher in defoliated C. sativa. These responses may be related to the health status of C. sativa, since it was subjected to pathogen damages and insect attacks. In contrast, the mast year in O. carpinifolia may have diverted the nutrient resources from leaves to fruits, and consequently explaining the physiological effects on the tree crown. These results suggest that the combined analysis of defoliation with foliar features and stand characteristics can provide insights into tree health and vitality.

Elliptic Fourier analysis of crown shapes in Quercus petraea trees.

Shape is a fundamental morphological descriptor, significant in taxonomic research as well as in ecomorphology, one method of estimation being from digitally processed images. In the present study, were analysed shapes of Q. petraea crowns, pertaining to five different stem diameter classes, from three similar stands. Based on measurements on terrestrial digital vertical photos, crown size analysis was performed and correlations between crown and stem variables were tested. Linear regression equations between crown volumes and dbh, and crown volumes and stem volumes were derived, explaining more than half of data variability. Employment of elliptic Fourier analysis (EFA), a powerful analysis tool, permitted the extraction of the mean shape from crowns, characterized by high morphological variability. The extracted, most important, coefficients were used to reconstruct the average shape of the crowns, using Inverse Fourier Transform. A mean shape of the crown, corresponding to stand conditions in which competition is added as influential shaping factor, aside genetic program of the species, is described for each stem diameter class. Crown regions with highest shape variability, from the perspective of stage development of the trees, were determined. Accordingly, the main crown shape characteristics are: crown elongation, centroid position, asymmetry with regard to the main axis, lateral regions symmetrical and asymmetrical variations.

Epicormiques chez le chêne sessile âgé de 13 ans : un faible effet provenance et un effet légèrement plus fort du nombre de branches et d’unités de croissance

• The provenance effect on epicormics is poorly documented and restricted to epicormic shoots. Our objective was to characterize the relationship between epicormics and provenance on 13-year-old Quercus petraea trees, taking into account their growth traits. • On the growth units (GU) studied, epicormics were essentially isolated buds (95%) and they were mainly located at branch bases, secondarily on GU limits and marginally on lateral position. Provenance effect was very small on the number of epicormics and slightly larger on the number of branches and GU limits. On the contrary, the growth situation-independently from provenance-proved to have a larger effect on the 2 latter growth traits. • Altogether, these results clearly show the predominant effect of morphological traits and thus of ontogeny. This opens important research perspectives: how growth conditions and genetics (at progeny and individual levels) influence height growth, setting and fate of axillary buds on the one hand and fate of epicormic buds inserted directly on the stem, or at branch bases on the other hand.

Does root competition asymmetry increase with water availability?

Background: Below-ground competition as a major structuring force in plant communities can be either symmetric or asymmetric with important consequences for the coexistence of plants. It is a matter of controversy whether asymmetry in competition increases with resource availability or not. Aims: This study tested the hypotheses that root competition between mature Fagus sylvatica and Quercus petraea trees is asymmetric and that asymmetry is more pronounced in non-water-limited environments. Methods : Initially equal-sized tree fine roots were grown for 365–390 days in root growth chambers in situ and exposed to competition by either a conspecific or an allospecific root. Relative root growth rate was used to determine asymmetry in root competition. Different soil moisture regimes were considered by conducting a throughfall reduction experiment and by including data from earlier experiments with contrasting moisture regimes. Results: The competitive interaction between Fagus and Quercus fine roots is asymmetric; root morphology appears to depend on the presence of a competitor; and asymmetry in root competition increases with increasing soil moisture availability. Conclusions: Below-ground competition in temperate broad-leaved mixed forests can be as asymmetric as competition for light, with asymmetry decreasing with increasing water shortage.

Hybridization between Quercus robur and Q. petraea in a mixed oak stand in Denmark

• Hybridization and mating pattern between Quercus robur and Q. petraea was studied in a 5.8 ha mixed forest stand in Jutland, Denmark which comprises in total 135 Quercus robur and 230 Q. petraea trees. Classification of the oak trees into species was performed using canonical discriminant analysis of a range of leaf morphological traits. Adult trees (365) and offspring (582) were genotyped with eight microsatellite markers. Seedlings were sampled in 2003 and acorns were collected in 2004. • Mating patterns of Q. robur and Q. petraea are expected to be different in the northern range of the distribution area and a larger hybridization rate is expected. It is further expected, that pollination from outside sources will be relatively less in small fragmented forest management systems compared to large scale oak forest. The conclusions should be verified through repeated year to year analysis of the mating pattern. • Phenological studies revealed that there was no difference in flowering time between species. Data for the adult trees revealed no significant departures from Hardy-Weinberg proportions and there was weak, but significant spatial genetic structure, which supports the idea that the stand is of natural origin. Spatial genetic structure in the first distance class is stronger for Q. petraea. The genetic composition of the offspring was remarkably consistent from year to year. Paternity analysis revealed that, on average, 85% pollination came from fathers within the stand. The direction of the pollen flow varied from year to year. Inter-specific hybridization was high and ranged from 15–17% and from 48–55% for Q. petraea and Q. robur mothers respectively. Paternity analysis revealed that the population was basically outcrossing and only 3.7% of the analysed progeny were the product of selfing. Over the two years of study, approximately 200 trees contributed to the paternity of the next generations. • The study confirms earlier studies with a greater tendency for Q. robur mothers to produce hybrid seeds than Q. petraea mothers. The rate of hybridization is higher in this Danish stand than in comparable studies elsewhere in Europe. Gene flow from outside sources are relatively low.

Differential reaction of Pinus sylvestris, quercus robur and Q. petraea trees to nitrogen and sulfur pollution

Establishment of the Nitrogen Fertilizer Factory in Pulawy, Poland (NFFP) in 1966 resulted in contamination of the environment with nitrogen and sulfur compounds. As a result, radial stem growth declined in Pinus sylvestris and increased in Quercus robur. In this study we explored possible causal agents responsible for differences in pollution response among P. sylvestris, Q. robur and Q. petraea species, including differential uptake of nitrogen oxide pollutants by foliage and nutrient imbalances. We compared trees growing in the vicinity of the NFFP and a control area and found that Q. robur leaves were characterized by a relatively smaller N increase than those of P. sylvestris. It is possible that relatively high accumulation of N by pine could cause metabolic dysfunction in that species. However, differences in the concentration of nitrogen or activity of nitrate reductase did not sufficiently explain observed growth differences among the studied species. It is likely that among the factors contributing to the increased growth of oaks after the establishment of NFFP there is the rapid decline and mortality of pollution-sensitive Scots pine trees, easing competition for light and nutrients in the remaining Quercus trees.

The process-based SIM–BIM model: towards more realistic prediction of isoprene emissions from adult Quercus petraea forest trees

The seasonal isoprene synthase model–biochemical isoprenoid biosynthesis model (SIM–BIM) is a recently developed process-based model to simulate isoprene emissions from vegetation. This model was validated using isoprene emission measurements from adult Quercus petraea (Mattuschka) Liebl. trees growing in a natural forest. Temperature and photosynthetic photon flux density (PPFD) data from a 120-year-old forest stand at Hofstetten in NW Switzerland were used to run SIM–BIM. Experimental isoprene synthase activity and isoprene emission rates from adult Q. petraea trees were compared to the model outputs for the years 2000 and 2001. High correlation (16.5% average deviation for isoprene synthase activity and 28% average deviation for isoprene emission factors) was observed between modelled and experimental data. In addition, a comparison was performed of the modelled values of SIM–BIM to values calculated using the algorithm ISOG97 of Guenther (Ecol. Appl. 7 (1997) 34). On the basis of the temperature and PPFD data from Hofstetten, this comparison clearly displayed the capability of SIM–BIM to simulate dynamic isoprene emission capacities during warm and sunny periods, and thus to model isoprene emission rates in a realistic manner for these conditions.

Drought responses at leaf, stem and fine root levels of competitive Fagus sylvatica L. and Quercus petraea (Matt.) Liebl. trees in dry and wet years

Abstract The inter-annual variability of four growth-related parameters (light-saturated photosynthesis Amax, leaf area index L, annual stem diameter growth S, and fine root production P) was investigated together with various leaf water status parameters in adult Fagus sylvatica and Quercus petraea trees during five summers with weak, moderate or severe soil water deficit. Study aims were (i) to identify differences in drought sensitivity among the tree organs (leaf, stem or root) and between the tree species, and (ii) to test the hypothesis that differences in whole-tree drought response are relevant for competition between Fagus and Quercus in Central European mixed stands. Drought had only weak or no influence on Amax and L of the two species during the 5 years; the only exception being a severe drought in 1990 with an Amax reduction of Fagus by 30%. Stem diameter growth of Fagus was significantly smaller in dry than in wet summers; in contrast, no clear stem growth/moisture relationship was detected for Quercus during the study period. Soil water deficits apparently stimulated fine-root growth of Fagus during the dry mid-summer 1995, thus compensating for root biomass losses due to high root mortalities in this period. Quercus fine-root biomass and productivity were not significantly influenced by this drought. A higher drought sensitivity of stem diameter growth, fine-root production and photosynthesis in Fagus corresponded to a larger inter-annual variability of the predawn leaf water potential between wet and dry summers and generally smaller leaf conductances of this species compared to Quercus. Quercus was less sensitive to drought in its growth processes, but showed larger inter-annual variabilities of the osmotic potentials of the leaf symplasm and of the seasonal minima of bulk leaf turgor compared to Fagus. Thus, Fagus is competitively superior in mixture with Quercus despite its higher sensitivity to soil water deficits. It is concluded that a whole-plant perspective rather than a leaf-centred view of drought response is needed to predict the consequences of water shortage for ecosystem-level processes, such as tree competition and succession driven by climate change.

Ontogeny of the proventitious epicormic buds in Quercus petraea.

In the present work, we described the fate of proventitious epicormic buds on the trunks of 40-year-old Quercus petraea trees and in parallel the vascular trace they produced in the wood. Our results show that small and large individual epicormic buds can survive as buds for 40 years and that both are composed of a terminal meristem and scales. Meristematic areas are detected in the scale axils of small buds; in addition to these meristems the large buds also have secondary bud primordia. The small buds are connected to the pith of the main stem by a unique trace, whereas the large buds are connected by one or multiple traces. A single trace might imply that the whole bud is still alive and multiple traces might indicate that the terminal meristem has died. In the latter case, each trace is connected to a secondary bud of the large bud. The buds found in a cluster are composed of a terminal meristem and scales with axillary meristems in the scale axils. A cluster is connected to the pith of a stem either by a unique trace when it seems to be the result of partial abscission of an epicormic shoot or multiple traces when it might have originated from an epicormic bud in which the terminal meristem has died. Whatever the type of the bud, the vascular trace in the bark is composed of a cambium, secondary xylem and parenchyma cells and the trace present in the wood had parenchyma cells with vestiges of secondary xylem. Each year, the vascular trace should be produced in the bark by the cambium of the tree but not by the bud itself. On 40-year-old Q. petraea, we observed a proliferation of epicormic buds and in parallel a multiplication of the number of vascular traces in the trunk, but the knots caused by the traces of epicormic buds in the wood, either as individuals or in clusters, are minor since their colours are only slightly darker than those of woody rays and they are less than 2 mm in diameter. The knots will appear when epicormic buds develop into shoots.

Sap-flow velocities and distribution of wet-wood in trunks of healthy and unhealthy Quercus robur, Quercus petraea and Quercus cerris oak trees in Hungary

Sap-flow of Quercus robur, Quercus petraea and Quercus cerris oak trees were studied. 43K radioisotope tracing, the heat pulse velocity technique and the Granier-method were employed. Numerous intense pulses were observed in healthy Quercus petraea superposing onto the usual diurnal change. Only a few pulses were observed in unhealthy Quercus petraea, in healthy Quercus cerris and healthy and unhealthy Quercus robur trees. Proportion of wet-wood assessed by γ- and X-ray computer tomography and magnetic resonance imaging was significantly less in healthy Quercus petraea trees than in healthy Quercus cerris trees. Proportion of wet-wood was higher in healthy trees than unhealthy trees of both species.

Variation of heartwood phenolics and oak lactones between the species and phenological types of Quercus petraea and Q. robur

Summary Pressler cores were taken of Quercus petraea and Q. robur trees from young German provenance stands and mature mixed plantations in England. The concentration of total phenolics extracted from the outer heartwood was measured and significant differences found between the two species. Concentrations of oak lactones, measured from provenance samples, also varied significantly between the species. However, the difference in total phenolics between species was much lower among the trees from the mixed plantations than from the provenance trials. Q. petraea was characterized by lower levels of total phenolics but greater concentrations of oak lactones than Q. robur. A comparison between late and early flushing Q. petraea trees found no significant difference in total phenolics between these phenological types.

Tyloses Formation and the State of Health of Quercus Petraea Trees in Hungary

In a 76-year-old sound and in a 77-year-old diseased trunk of Quercus petraea the number of earlywood vessels with and without tyloses were counted along a 1 cm tangential segment of the annual rings, in four directions at four heights (0.16, 1.35, 12.0, 24.0 m). At all heights of the sound stem, the percentage of earlywood vessels sealed by tyloses is low (2.57-4.13-5.94%). In the diseased stem, the percentage of earlywood vessels sealed by tyloses is higher (7.40- 13.08-19.86%) than it is in the sound stem. This demonstrates a decreased hydraulic capacity in the diseased stem. In both trees, the percentage of earlywood vessels sealed by tyloses increased from the stump (at 0.16 m trunk height = 5.02 %) upwards (at 12.0 m = 12.58%).