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European beech is an ecologically and commercially important species, which is expected to decline in several regions because of heat and drought stress associated with climate change. Knowledge of the genetic basis of the adaptation to climate is needed to guide assisted migration. Genetic variation at 1704 single-nucleotide polymorphisms (SNPs) resulting from ddRAD sequencing, primarily located in gene exons, was studied in 181 specimens representing 123 populations distributed over most of the whole range. Bayesian analysis of population structure yielded two clusters exhibiting a clear longitudinal cline and correlated with indicators of low temperatures and temperature fluctuation. Five SNPs were significantly associated with climatic variables related primarily to heat and temperature ranges. Two alternative explanations are offered for the observed response patterns: (i) differential sensitivity to heat and (ii) response mediated by vegetative phenology. [ABSTRACT FROM AUTHOR]

The complex of beech taxa in western Eurasia (Fagus sylvatica L. s.l.) represents one of the most widespread broad-leaved trees in the temperate forests of the northern hemisphere. Two subspecies are generally recognized, F. sylvatica ssp. sylvatica in Europe and F. sylvatica ssp. orientalis in southwestern Asia, but several strongly differentiated regional populations were identified within this complex. To reveal geographical and genomic patterns of hybridization and introgression, genetic variation at 6789 single-nucleotide polymorphisms (SNP) resulting from ddRAD sequencing was studied in 288 specimens representing 207 populations distributed across the whole range. Two clusters resulting from a Bayesian analysis of population Structure well coincided with the subspecies, while increasing the number of clusters allowed to distinguish divergent lineages within subspecies. Two zones of potential hybridization between such lineages were analyzed: western Balkans at the contact of both subspecies and the Alpine area at the contact of populations coming from different glacial refugia. Geographical distribution of hybrid indices in the Balkan hybrid zone indicates asymmetric gene flow preferentially directed from F. orientalis to F. sylvatica. Eight SNPs showed a significant shift of genomic cline centers, seven of them toward excess F. orientalis ancestry, suggesting that introgression irregularly affects different regions of the beech genome. On the other hand, no genomic cline outliers were found in the Alpine hybrid zone. Implications for assisted gene flow are shortly discussed. [ABSTRACT FROM AUTHOR]

European beech is one of the most common tree species in Europe and is generally suggested to play even more of a prominent role in forestry in the future. It seems to have the potential to partially replace Norway spruce, as it is less sensitive to expected warmer and drier conditions. It is, however, not well known in which regions these new plantings would be particularly favourable and if specific provenances may be better adapted to the new conditions than others. Therefore, we estimated the potential early height growth under climate conditions in 2040–2060 for 20 beech provenances across a region covering the Czech Republic and Slovakia. This Central European region is expected to experience considerably drier and warmer conditions in the future. For this exercise, we implemented a new neural network model developed from height growth information obtained from the open-access BeechCOSTe52 database. The simulations are driven by past and future climate data obtained from the WorldClim database of historical climate data and future climate projections. Simulations revealed that provenances originating from drier regions performed on average significantly better than those from regions with good water supply. Moreover, provenances originating from drier regions had a particularly large advantage in the relatively arid regions of Central Czechia and Southern Slovakia. We can also confirm that all provenances showed a high phenotypic plasticity of height growth across the whole investigated region. [ABSTRACT FROM AUTHOR]

Several decades ago, many former pastures in Central Europe were afforested or colonized by trees after being abandoned. Knowledge of the effects of tree species on soil properties is important for planning of the composition of future forests. In this regard, a research location in Vrchdobroč (Central Slovakia), which is former agricultural land used as pasture, enables the exploration of ecosystem processes and properties in stands of different tree species after afforestation. The goal of our study was to find out whether changes in soil properties, including soil microbial activity and diversity among different stands, were already observable 45 years after the afforestation, and how the effects differed among stands of different tree species. The study was conducted in the pure stands of Norway spruce (Picea abies L. Karst.), Douglas fir (Pseudotsuga menziesi (Mirb.) Franco), European beech (Fagus sylvatica L.) and sycamore maple (Acer pseudoplatanus L.). Multivariate analyses of physico-chemical soil properties indicated an overlap between the soils under the Douglas fir and the spruce, but a clear separation of beech from sycamore. In general, both microbial activity and diversity were, surprisingly, highest under the Douglas fir, followed by the sycamore, with the beech and the spruce showing mostly lower values. [ABSTRACT FROM AUTHOR]

This review summarizes the development of population genetics and population genomics studies of forest trees in Slovakia during the past 40 years. Various protein and DNA markers have been applied during this period to address several topics in evolutionary genetics and biogeography of trees: allozymes, uniparentally inherited chloroplast and mitochondrial markers, simple sequence repeats and single nucleotide polymorphisms. The main object of studies of phylogeny and postglacial migration were Fagus sylvatica s.l. and eastern-Mediterranean firs (Abies Mill. section Abies), where the divergence of genetic lineages (species and subspecific taxa) in time, as well as colonization of the current ranges during the Holocene were reconstructed. The studies on intraspecific gene flow and homoploid hybridization focused on hybrid swarms Pinus sylvestris/P. mugo and firs. Unusual maternal inheritance of chloroplast DNA was revealed in P. mugo × P. sylvestris crosses. Contrasting geographical structures of hybrid zones were revealed in wind-dispersed vs. animal-dispersed trees. Within the studies of adaptation, signals of selection were identified both in field observations and common-garden experiments on Picea abies, F. sylvatica and A. alba. Perspectives of ongoing research employing next-generation sequencing were shortly outlined. [ABSTRACT FROM AUTHOR]

The assisted migration of resistant seeds and seedlings may be a key to mitigating the effects of climate change on the productivity and composition of forest ecosystems. These efforts require an understanding of the intraspecific variability in the response of trees to extreme weather events such as heat waves. In this study, we assessed the geographical patterns of photosystem II (PSII) performance and thermostability in European beech (Fagus sylvatica L.) and whether intraspecific differences are associated with climate of origin. Two provenance trials with starkly contrasting climates were used for this study. Leaves were sampled both before and after natural heat stress exposure. Rapid chlorophyll fluorescence kinetics was used to evaluate PSII performance and PSII thermostability after simulated heat stress. The performance of PSII at 30 °C, which is still considered a non-damaging temperature, was generally slightly better at the warmer location than at the colder location. The populations originating closer to the Slovenian refugium, as well as those growing closer to their site of origin, showed better performance of PSII but not greater thermostability. The effect of simulated heat stress was much stronger in the colder plots compared to the warmer plots, but only for previously stressed trees. Likewise, we found indicators of geographical patterns of thermotolerance as well as relationships between thermotolerance and climate of origin mostly for trees exposed to natural heat. While the origin of provenances partly explained the variation among provenances, acclimation driven by climate played a major role in the response to heat stress. In beech, PSII seems to have a potential for coping with high temperature. [ABSTRACT FROM AUTHOR]

The Fagus sylvatica L. species complex in Europe and Western Asia comprises two commonly recognized subspecies, F. sylvatica subsp. sylvatica [= F. sylvatica sensu stricto (s. str.)] and F. sylvatica subsp. orientalis (= F. orientalis), and two putatively hybridogenous or intermediate taxa, "F. moesiaca" and "F. taurica". The present study aimed to examine the demographic history of this species complex using 12 allelic loci of nine allozymes scored in 279 beech populations in western Eurasia. Three sets of phylogenetic scenarios were tested by approximate Bayesian computation: one dealing with the divergence of subspecies and/or regional populations within the whole taxonomical complex, and two others focusing on the potential hybrid origin of "F. moesiaca" and "F. taurica". The best-supported scenario within the first set placed the time of divergence of regional populations of F. orientalis in the Early Pleistocene (1.18-1.87 My BP). According to this scenario, the Iranian population was the ancestral lineage, whereas F. sylvatica s. str. was the lineage that diverged most recently. "Fagus taurica" was found to have originated from hybridization between the Caucasian population of F. orientalis and F. sylvatica s. str. at 144 ky BP. In contrast, there was no evidence of a hybrid origin of "F. moesiaca". The bestsupported scenario suggested that the Balkan lineage is a part of F. sylvatica s. str., which diverged early from F. orientalis in Asia Minor (817 ky BP), while both the Italian and Central-European lineages diverged from the Balkan one later, at the beginning of the last (Weichselian) glacial period. [ABSTRACT FROM AUTHOR]

Interpopulation variation of relative and absolute genome size was studied in Fagus sylvatica subsp. sylvatica and subsp. orientalis. The study included 18 populations of beech planted in a common-garden experiment in central Slovakia and three additional populations from the Caucasus. Nuclear DNA content was determined by means of flow cytometry using the AT-specific fluorochrome 4′,6-diamidino-2-phenylindole and non-specific propidium iodide, and its associations with climate, growth, phenology and physiological traits were assessed. The approximate average nuclear DNA content (2C) across all samples was 1.178 ± 0.020 pg. The lowest mean relative genome sizes were observed in the Alpine range, whereas they increased toward the range margins; no clear trend was observed for 2C values. Temperature seasonality and temperature annual range were found to be negatively associated with genome size. Among phenotypic traits, the maximum chlorophyll a fluorescence yield (Fv/Fm) was found to be negatively correlated with relative genome size, whereas phenology and some photosynthetic parameters were correlated with the 2C values. [ABSTRACT FROM AUTHOR]

Current climate changes can led to a decline of local beech populations fully adapted to previous climate conditions. In this context, the issue of variation in adaptive traits becomes important. A field experiment with 18-year-old trees of Fagus sylvatica L. was conducted on provenance plot located in Tále (Central Slovakia), where physiological responses of five beech provenances originating from contrasting sites along an altitudinal gradient from 55 to 1100 m a.s.l. across the range of the natural beech distribution were studied. Stomatal characteristics, parameters of chlorophyll a fluorescence and gas exchange parameters were determined. Overall, we observed a significant increase in physiological performance at the leaf level with increasing altitude of origin. Provenances from the higher altitudes showed higher CO2 assimilation rate, stomatal density, potential conductance indices and photochemical efficiency, and lower capability for dissipation of energy by heat. A similar pattern of response was recorded in relation to the precipitation regime of sites of origin. Moreover, in the context of the temperature regime, several negative trends were observed. [ABSTRACT FROM AUTHOR]

• • We present a unique network of 11 Oriental beech planting sites across Western Europe. • • Plantings were established during the 20th century next to native European beech forests. • • We track the geographic origin of planted Oriental beech. • • Genetic and phenological data show extensive hybridization between the two beech subspecies. • • We estimate the expected gain in genetic diversity upon assisted gene flow. The benefits and risks of human-aided translocation of individuals within the species range, assisted gene flow (AGF), depend on the genetic divergence, on the rate and direction of hybridization, and on the climate transfer distance between the host and donor populations. In this study, we explored the use of Oriental beech (Fagus sylvatica subsp. orientalis), growing from Iran to the Balkans, for AGF into European beech populations (F. sylvatica subsp. sylvatica) that increasingly suffer from climate warming. Using samples from natural populations of Oriental and European beech and microsatellite loci, we identified 5 distinct genetic clusters in Oriental beech with a divergence (F ST) of 0.15 to 0.25 from European beech. Using this knowledge, we traced the origin of 11 Oriental beech stands in Western Europe established during the 20th century. In two stands of Greater Caucasus origin, we found evidence for extensive hybridization, with 18% and 41% of the offspring having hybrid status. Climate data revealed higher seasonality with warmer and drier summers across the native Oriental beech sites in comparison to the planting sites in Western Europe. Accordingly, we found that bud burst of Oriental beech occurred four days earlier than in European beech. Overall, our results suggest that AGF of Oriental beech could increase the genetic diversity of European beech stands and may foster introgression of variants adapted to expected future climatic conditions. Our study showcases the evaluation of the benefits and risks of AGF and call for similar studies on other native tree species. [ABSTRACT FROM AUTHOR]

The knowledge of the extent of local adaptation is essential for forest reproductive material transfer, designing gene conservation programs and measures for mitigation of the ongoing climate change. A common methodology for assessing selection underlying local adaptation is the comparison of differentiation at neutral markers (measured by F) against quantitative traits (measured by Q). We investigated differentiation in phenology, height and diameter growth, and parameters of photosynthesis and water regime in a widespread European broadleaved tree, European beech ( Fagus sylvatica L.). As the assessment of Q requires known pedigree structure of the tested populations, it was approximated by the coefficient of phenotypic differentiation P. For all phenology traits, especially budburst timing, there is a strong and reliable evidence of local adaptation as indicated by P > F. On the other hand, P was generally smaller than F for most growth and physiological traits, but the evidence for uniform selection or canalization acting at genes underlying these traits is generally absent or weak. Possible heritable basis of phenological differentiation is discussed, and implications for the current EU legislation on forest reproductive material are drawn. [ABSTRACT FROM AUTHOR]

The unimodal species richness-altitude distribution pattern seems to be universal. To investigate the validity of this phenomenon in homogeneous substrate and vegetation conditions, we sampled beech-dominated forests in five volcanic mountain ranges in the Western Carpathians. European beech ( Fagus sylvatica L.) formed monodominant closed-canopy stands at altitudes from 300 to 1,200 m. Along this gradient, the influence of beech on understory plant species richness was expected to be strong and uniform. The shape of the species richness-altitude relationship was analyzed for three datasets: herb layer, shrub layer, and both layers merged together. Contrary to prediction, the studied species richness-altitude relationship was inversely unimodal, with a minimum at intermediate altitudes. Quadratic regression models were statistically significant for all three datasets ( P<0.001) and the explained variability ranged from 12 % to 20 %. The possible explanation for the observed pattern is twofold. In the central part of the altitudinal gradient, low species richness is due to strong competition by monodominant beech with accumulation of leaf litter and uptake soil resources, mainly water. This influence is somewhat released towards the margins of the gradient. Secondly, the species pool from the neighbouring communities increases species richness only in the lower parts of the altitudinal gradient. [ABSTRACT FROM AUTHOR]

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The study focuses on geographical patterns of genetic variation at allozyme loci common for four main tree species of Central Europe (Norway spruce, silver fir, common beech and sessile oak). Moving-window averaging of four indicators of allelic richness and diversity (proportion of polymorphic loci, mean number of alleles per locus, effective number of alleles and expected heterozygosity) with window size of 50 × 50 km was used to identify the patterns. Moreover, local genetic divergence was assessed using the G ST (Nei, Molecular population genetic and evolution, Amsterdam and Oxford, North-Holland, ) and D j (Gregorius and Roberds, Theor Appl Genet 71:826–834, ) statistics for common beech and silver fir, where raw genotype data were available. Spatial patterns of diversity and allelic richness were quite similar. Romanian Carpathians were identified as the most important hotspot of genetic diversity and evolutionary divergence in Central Europe. Implications for genetic conservation are briefly discussed. [ABSTRACT FROM AUTHOR]

• Here, palaeobotanical and genetic data for common beech ( Fagus sylvatica) in Europe are used to evaluate the genetic consequences of long-term survival in refuge areas and postglacial spread. • Four large datasets are presented, including over 400 fossil-pollen sites, 80 plant-macrofossil sites, and 450 and 600 modern beech populations for chloroplast and nuclear markers, respectively. • The largely complementary palaeobotanical and genetic data indicate that: (i) beech survived the last glacial period in multiple refuge areas; (ii) the central European refugia were separated from the Mediterranean refugia; (iii) the Mediterranean refuges did not contribute to the colonization of central and northern Europe; (iv) some populations expanded considerably during the postglacial period, while others experienced only a limited expansion; (v) the mountain chains were not geographical barriers for beech but rather facilitated its diffusion; and (vi) the modern genetic diversity was shaped over multiple glacial–interglacial cycles. • This scenario differs from many recent treatments of tree phylogeography in Europe that largely focus on the last ice age and the postglacial period to interpret genetic structure and argue that the southern peninsulas (Iberian, Italian and Balkan) were the main source areas for trees in central and northern Europe. [ABSTRACT FROM AUTHOR]

The timing of foliar budburst is an important component of the fitness of trees. Adaptation of budburst to local temperatures and phenotypic plasticity in the date of budburst to changes in temperature can therefore be expected. In this study, we analysed provenance trials of European beech ( Fagus sylvatica L.) established over a wide geographic and climatic range in Europe. The analysis was based on a phenological model that represents the key processes at budburst phenology of temperate- and boreal zone deciduous trees. We conclude that adaptive differences exist between provenances in the critical chilling- and forcing requirements triggering budburst. Moreover, it is likely that these provenances show a plastic response to local environmental conditions for these two factors. Chilling- and forcing temperature requirements are key traits determining a tree’s response of the date of foliar budburst to temperature. We infer from our results that trees would be able to adjust this response when climatic conditions change. Implications for climate change assessment studies and suggestions to incorporate this second order phenotypic plasticity in phenological models are discussed. [ABSTRACT FROM AUTHOR]

The photosynthetic responses to the combined effect of drought and heat stress were studied in leaves of 19-years-old European beech ( Fagus sylvatica L.) trees originating from five provenances in Central Europe differing by altitude (55–1250 m), and grown in the same experimental plot. The measurements were conducted at the beginning of heat waves, under two different conditions: during a dry period (middle of July) and after recovery in wetter period, at the beginning of August. The decreases of stomatal conductance ( g s ) and net photosynthesis rate ( A CO2 ) during drought and heat wave stress were very similar in all provenances. However, we observed distinct response of PSII photochemistry on combined drought and high temperature stress, well associated with altitude of origin of the beech provenances. Measurements of pulse amplitude modulated (PAM) fluorescence identified maintenance of a high electron transport rate in beech provenances from high altitudes under drought and heat wave conditions, associated with some decrease of excitation pressure on PSII. This can be explained by enhanced capacity of alternative electron sinks to utilize the excess of electrons as a photoprotective mechanism. The analyses of fast chlorophyll fluorescence kinetics confirmed the differences in responses of PSII photochemistry between provenances originating from different altitudes. Compared with provenances at higher altitudes, we found more sensitive response (i.e. more limited electron transport at the PSII acceptor side and changes in the size of light harvesting complexes) to drought and heat stress, in those growing at low altitudes. Our results support the hypothesis that the provenances originating from higher altitudes possess enhanced phenotypic plasticity related to photoprotective responses, resulting from the long-term adaptation to marginal mountain conditions. [ABSTRACT FROM AUTHOR]