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Abstract: Pairings were carried out between isolates of the ash dieback pathogen Hymenoscyphus pseudoalbidus (Chalara fraxinea) to determine whether vegetative incompatibility (mycelial self–nonself recognition) reactions could be discriminated. On malt agar (MA) and ash sapwood agar (ASA) distinct compatible and incompatible reactions were observed. Compatible (C- or c-) reactions were characterised by full or partial colony intermingling along the junction line. Incompatible (G- or g-) reactions were characterised by a gap ca. 1–3 mm wide along the junction line. On MA a distinct narrow brown line or L-reaction was observed with some gap reactions, often comprising reticulate mycelium and conidia-producing phialides. When eleven isolates from a dieback site at Lower Wood, Norfolk were paired on ASA 53 of 54 reactions between different isolates gave incompatible reactions. A similar result was obtained with smaller samples from two further sites in Norfolk and Kent. This indicates that for local populations in the UK most genetic individuals of H. pseudoalbidus are likely to be vegetatively incompatible. The implications for the ecology and genetics of H. pseudoalbidus are discussed. [Copyright &y& Elsevier]

European ash ( Fraxinus excelsior) is threatened by Hymenoscyphus pseudoalbidus, the agent of ash dieback disease. Beside ordinary ash dieback symptoms, collar rots have been reported on declining ashes as an additional problem of increasing severity. Since 2009, ash dieback has been surveyed annually in a provenance trial on four different sites in southwest Germany (Metzler et al. in Ger J For Res 183:168–180, 2012 ). The trial was established in 2005. Data of tree growth, ash dieback symptoms and collar rot prevalence were collected by surveying the trial in summer 2012 and compared with previously published data of the trial. Evaluations revealed a continuous and considerable increase in dieback severity since 2009. The results suggest that the infection process has not come to a standstill yet. Up to 2012, 6 % of the trees remained symptomless, whereas mortality added up to 9 %. There were significant differences in ash dieback severity between the investigated provenances. Collar rot prevalence ranged from 19 to 59 % between study sites. Moreover, high spatial dependency of collar rot prevalence could be detected within sites. Collar rots were more abundant on trees of severe ash dieback intensity, but could also be detected on 15 % of otherwise healthy trees. Mycelium from collar rots could be identified by means of RFLP analyses and sequencing of the ITS region as most likely belonging to Armillaria gallica. The possible roles of Armillaria spp. and H. pseudoalbidus in collar rot formation are discussed. [ABSTRACT FROM AUTHOR]

European ash ( Fraxinus excelsior) is threatened by Hymenoscyphus pseudoalbidus, the agent of ash dieback disease. Beside ordinary ash dieback symptoms, collar rots have been reported on declining ashes as an additional problem of increasing severity. Since 2009, ash dieback has been surveyed annually in a provenance trial on four different sites in southwest Germany (Metzler et al. in Ger J For Res 183:168–180, 2012 ). The trial was established in 2005. Data of tree growth, ash dieback symptoms and collar rot prevalence were collected by surveying the trial in summer 2012 and compared with previously published data of the trial. Evaluations revealed a continuous and considerable increase in dieback severity since 2009. The results suggest that the infection process has not come to a standstill yet. Up to 2012, 6 % of the trees remained symptomless, whereas mortality added up to 9 %. There were significant differences in ash dieback severity between the investigated provenances. Collar rot prevalence ranged from 19 to 59 % between study sites. Moreover, high spatial dependency of collar rot prevalence could be detected within sites. Collar rots were more abundant on trees of severe ash dieback intensity, but could also be detected on 15 % of otherwise healthy trees. Mycelium from collar rots could be identified by means of RFLP analyses and sequencing of the ITS region as most likely belonging to Armillaria gallica. The possible roles of Armillaria spp. and H. pseudoalbidus in collar rot formation are discussed. [ABSTRACT FROM AUTHOR]

Descripció de l'estructura, la composició florística i l'ecologia dels boscs mesòfils de les Muntanyes Catalanídiques septentrionals. És analitzada la variabilitat d'aquest bosc a les diverses panes de la serralada. Són estudiats els sintàxons Doronico-Fraxinetum, re presentat per les subassociacions doranicetosum, melampyretosum. vincetosum.festucetosum, luzuletosum i aretosum.

Das Eschentriebsterben nimmt in Deutschland unter den bedeutsamen Baumkrankheiten gegenwärtig eine zentrale Rolle ein. In den Baumschulen sind die wirtschaftlichen Schäden besonders groß, wenngleich auch Wälder in zunehmendem Maße betroffen sind. Die hier vorgestellten mykologischen und histologischen Untersuchungen wurden an dreijährigen Baumschulpflanzen durchgeführt. Dabei ist die durch Chalara fraxinea (Teleomorphe: Hymenoscyphus albidus) verursachte Infektionsrate in der Rinde, im äußeren und inneren Holzteil sowie im Mark für die Organe Spross und Wurzel ermittelt worden. Die Invasions- und Ausbreitungsstrategie des Pilzes wurde im verholzten Spross untersucht. Zudem wurde überprüft, ob bodenbürtige Oomyceten (Phytophthora- bzw. Pythium-Arten) als primäre oder maßgebliche Schädigungsursache in Frage kommen. Die Ergebnisse bestätigen die dominante Rolle von C. fraxinea als Verursacher des Eschentriebsterbens und schließen zugleich die Bedeutung von Oomyceten im Krankheitsprozess aus. Die Autoren kommen zu dem Schluss, dass der Pilz den verholzten Spross sehr effektiv aus zentralen Bereichen heraus dreidimensional zu erschließen vermag und dabei nicht vorrangig endophytisch lebt. Die zunächst den oberirdischen Teil der Pflanze schädigende Infektion kann sich nachfolgend auf alle Bereiche im Wirt ausdehnen.

Some common ash trees (Fraxinus excelsior) show tolerance towards shoot dieback caused by the invasive ascomycete Hymenoscyphus fraxineus. Leaf petioles are considered to serve as a pathogen colonization route to the shoots. We compared four common ash clones with variation in disease tolerance, and included the native host, Manchurian ash (Fraxinus mandshurica), as a reference. Tissue colonization, following rachis inoculation by H. fraxineus, was monitored by histochemical observations and a quantitative polymerase chain reaction (qPCR) assay specific to H. fraxineus. Axial spread of the pathogen towards the petiole base occurred primarily within the phloem and parenchyma, tissues rich in starch in healthy petioles. In inoculated petioles, a high content of phenolics surrounded the hyphae, presumably a host defense response. There was a relationship between field performance and susceptibility to leaf infection in three of the four studied common ash clones, i.e., good field performance was associated with a low petiole colonization level and vice versa. Low susceptibility to leaf infection may counteract leaf-to-shoot spread of the pathogen in common ash, but the limited number of clones studied warrants caution and a larger study. The Manchurian ash clone had the highest petiole colonization level, which may suggest that this native host has evolved additional mechanisms to avoid shoot infection. [ABSTRACT FROM AUTHOR]

Abstract: We investigated Fraxinus excelsior breeding system using field data collected in a natural population and in a seed orchard. First, we attested functional trioecy (co-occurrence of males, hermaphrodites and females), with males producing pollen, hermaphrodites producing both pollen and seeds simultaneously, and females producing seeds. Second, we found that the reproductive system of F. excelsior was not labile, as sex expression seemed to be stable through time. Third, gender is genetically determined since different trees belonging to the same clone in the orchard exhibit similar sexual phenotypes. [Copyright &y& Elsevier]

• Context: Tree species differ largely in their capability to produce characteristic shade leaves with effective morphological and physiological acclimation to low light. • Aims: By examining the sun/shade leaf differentiation in leaf morphology, foliar nitrogen and photosynthetic capacity in five temperate tree species of different successional status, we aimed at identifying those leaf traits that determine the development of a typical shade crown with low light-acclimated leaves. • Methods: Leaf morphology, foliar N content, photosynthetic capacity ( V, J and A) and leaf dark respiration ( R) were measured in the canopies of 26 adult trees of Fraxinus, Acer, Carpinus, Tilia and Fagus species. • Results: Six traits (the sun/shade leaf differentiation in specific leaf area, leaf size, A per leaf area or per mass, photosynthetic N use efficiency and R) were found to characterise best the degree of low light acclimation in shade leaves. All five species exhibited certain modifications in leaf morphology and/or physiology in response to low light; Fagus sylvatica showed the highest and Fraxinus excelsior the lowest shade leaf acclimation. • Conclusions: Our results indicate that the five early/mid- to late-successional species have developed species-specific low light acclimation strategies in their shade crowns which differ in terms of the relative importance of leaf morphological and physiological acclimation. [ABSTRACT FROM AUTHOR]

This study encompassed 137 cultures of Diplodia mutila isolated from necrotic tissue of 3- to 20-year-old trees of Fraxinus excelsior with decline symptoms, originating from three geographic regions of Poland differing by climatic conditions. Fungus identification was conducted on the basis of morphological traits of cultures and confirmed by analysis of ribosomal DNA sequences. The structure and genetic variation of D. mutila populations was determined with the use of RAMS markers. Neighbor Joining analysis of ITS sequences of the examined isolates showed the greatest similarity to sequences of D. mutila isolated from F. excelsior and deposited in GenBank. Intra-population variation expressed by Dice coefficient and Shannon index was high and increased along with the shifting of a population's location from mild climate (northern Poland) to more severe climate, characteristic for upland and mountainous areas (southern Poland). The smallest genetic distance was shown by pairs of populations close to one another, inside individual regions. AMOVA showed great share (91%) of genetic variation inside a population, whereas variation was very small between populations (6.4%) and regions (2.6%). Principal component analysis showed grouping of fungus populations in accordance with their geographic location. [ABSTRACT FROM AUTHOR]

The functional role of internal water storage is increasingly well understood in tropical trees and conifers, while temperate broad-leaved trees have only rarely been studied. We examined the magnitude and dynamics of the use of stem water reserves for transpiration in five coexisting temperate broad-leaved trees with largely different morphology and physiology (genera Fagus, Fraxinus, Tilia, Carpinus and Acer). We expected that differences in water storage patterns would mostly reflect species differences in wood anatomy (ring vs. diffuse-porous) and wood density. Sap flux density was recorded synchronously at five positions along the root-to-branch flow path of mature trees (roots, three stem positions and branches) with high temporal resolution (2 min) and related to stem radius changes recorded with electronic point dendrometers. The daily amount of stored stem water withdrawn for transpiration was estimated by comparing the integrated flow at stem base and stem top. The temporal coincidence of flows at different positions and apparent time lags were examined by cross-correlation analysis. Our results confirm that internal water stores play an important role in the four diffuse-porous species with estimated 5–12 kg day−1 being withdrawn on average in 25–28 m tall trees representing 10–22% of daily transpiration; in contrast, only 0.5–2.0 kg day−1 was withdrawn in ring-porous Fraxinus. Wood density had a large influence on storage; sapwood area (diffuse- vs. ring-porous) may be another influential factor but its effect was not significant. Across the five species, the length of the time lag in flow at stem top and stem base was positively related to the size of stem storage. The stem stores were mostly exhausted when the soil matrix potential dropped below −0.1 MPa and daily mean vapor pressure deficit exceeded 3–5 hPa. We conclude that stem storage is an important factor improving the water balance of diffuse-porous temperate broad-leaved trees in moist periods, while it may be of low relevance in dry periods and in ring-porous species. [ABSTRACT FROM PUBLISHER]

Abstract: A sound knowledge of the soil properties required by tree species is a prerequisite for addressing many practical and scientific issues such as forest management or the predictive mapping of tree species. To date, such knowledge has been derived mainly from laboratory experiments and from case studies in the field. The importance of soils for the distribution of tree species has, however, hardly been tested systematically with comprehensive data including climate, soil and vegetation inventories. In our study, we analysed a comprehensive database to explore how soil and topo-climatic properties relate to the abundance of regenerating and mature beech (Fagus sylvatica L.), ash (Fraxinus excelsior L.) and sycamore (Acer pseudoplatanus L.) in mature forests across Switzerland. From 806 forest plots distributed all over strong environmental gradients, we used soil and topo-climatic data as predictors and the abundances of tree species in the herb and in the tree layer as response variables. To test the explanatory power of the predictors, we conducted variation partitioning analyses with generalized linear models. Soil predictors involved nutrients, potentially toxic elements, soil aeration and water availability. The explanatory power of most soil predictors was tested in different soil layers to a depth of 1m. Ash and sycamore were much more sensitive to soil variables than beech. The most relevant soil variables for the competitive ability of the three species were C/N-ratio, humus form, aluminium content, base saturation, magnesium content, and soil aeration. Shortage of nutrients limited the distribution of ash and sycamore and excess of toxic elements the distribution of ash. For beech, no soil-induced distribution limits were detectable. Ash was absent if the C/N-ratio in the topsoil was greater than 20. On such sites, sycamore was absent too or reached heights of at most 15–20m, i.e. well below the upper canopy. Ash was absent or reached a maximum height of 15m on acidic soils including at least one soil layer with a base saturation less than 20% in the upper 1m of the soil. The soil properties relevant for the competitive ability of ash and sycamore were more apparent for mature than for regenerating trees. In most cases, the topsoil influenced tree abundances more than the subsoil did. [Copyright &y& Elsevier]

Ash dieback damage was assessed and analysed on 16–22 year-old grafts in two ash seed orchards (Fraxinus excelsiorL.). The grafts originated from 106 plus-tree clones selected from 27 stands in southern Sweden based on their phenotypes. The results obtained indicate that ash dieback disease is strongly genotypically controlled. There was considerable genotypic variation among individuals. None of the clones seemed to be totally resistant, but some exhibited reduced susceptibility and retained this resistance after 6 years under heavy infection pressure. Autumn phenology based on leaf coloration was subject to moderate genetic control (H2= 0.19). The genetic correlation between autumn phenology and damage was weak to moderate (rGfrom 0.38 to 0.60) and positive, indicating that susceptible clones have a prolonged growing season. There was no evidence suggesting that stands differed in susceptibility. Together with the high heritability of resistance, strong age×age correlations and weak genotype×environment interactions, this suggests there is good scope for breeding less susceptible trees for the future. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study performed in 28 ash stands located in Myślenice and Dynów Forest Districts in southern Poland. The intensity of Fraxinus excelsior disease process was estimated based on the disease symptoms analysis of 1400 trees. The amount of infectious material of Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea) was estimated by the leaf litter examination on 166 square (0.5 × 0.5 m) plots. The total number of ash leaf rachises and apothecia were counted. The analysis shows that the estimated number of H. pseudoalbidus apothecia may reach from 370 thousand to over 13 million per hectare at a time. [ABSTRACT FROM AUTHOR]

Abstract: Through their leaf litter and throughfall water, tree species can have a pronounced influence on soil chemistry. However, there is little knowledge of species-specific root effects on greenhouse gas fluxes between forest soils and the atmosphere. By growing saplings of beech (Fagus sylvatica) and ash (Fraxinus excelsior) in monoculture or mixture at defined atmospheric and soil conditions in rhizotrons, we tested four hypotheses related to potential root-induced tree species effects on the uptake of CH4 and the emission of N2O and CO2 from the soil. This design excluded putative effects of leaf litter mineralisation on trace gas fluxes. Gas fluxes were measured biweekly using the closed chamber technique; the CO2 derived from root respiration was estimated, and the concentration of organic acids in the rhizosphere solution was analysed. Rhizotrons planted with ash took up significantly more CH4 and emitted less N2O than control rhizotrons without plants. CH4 and N2O fluxes from beech rhizotrons did not differ from the root-free control but were significantly smaller (CH4) or higher (N2O) than the fluxes from the ash treatment. While root respiration of ash was higher than of beech, root-induced soil respiration was higher in the rhizosphere of beech roots. The concentration of organic acids tended to be higher in the rhizosphere of beech and also the composition was different from that of ash. We conclude that tree species identity may substantially alter the soil source/sink strength for greenhouse gases through root-related processes. [Copyright &y& Elsevier]

Background: Soil samples were taken from a depth of 0-10 cm under the Quercus cerris and Fraxinus excelsior at an altitude of 1300-1500 m from the Kullin site at Gulnar-Mersin and were compared for their pH, CaCO3, nitrogen (N) %, and carbon (C) % contents. Balanced soils in natural forest ecosystems are known to be very rich in carbon content which increases with latitude and altitude and that the C/N ratio varies greatly between the soils of different plant species. We determined the values of the C/N rates in Q. cerris and F. excelsior soils of the Gulnar Gezende forest for the first time at this altitude. Material and Methods: A pH meter and Scheibler calcimeter were used to determine the soil pH and lime contents respectively. Percentage C was determined using the Anne method and the N% with the Kjeldahl method. Results: There was no difference in the pH values and nitrogen percentage contents between the two soils. Q. cerris soil was found to have medium levels of CaCO3, while the level of CaCO3 in F. excelsior soils was low. The C/N rates and carbon contents were higher in Q. cerris soil than F. excelsior soil (P<0.05). Conclusions: The higher carbon content of Q. cerris soil can be explained by higher amounts of organic matter compared with F. excelsior, which might depend on factors such as microclimate and their specific characteristics. [ABSTRACT FROM AUTHOR]

A dynamic branch enclosure system was used to measure emission rates of biogenic volatile organic compounds (BVOCs) from two common European tree species: Fraxinus excelsior and Quercus robur under ambient conditions in Flanders (Belgium). Both tree species were studied for seasonal variability of BVOC emission rates under natural biotic stress (infestations). Emissions were normalized at standard conditions of temperature and photosynthetic active radiation (PAR) (30°C and 1000 µmol m−2 s−1, respectively). Emission rates from Fraxinus excelsior were highest in May (9.56 µg gDW −1 h−1) and lowest in October (1.17 µg gDW −1 h−1). This tree species emitted (Z)-β-ocimene, (E)-β-ocimene and α-farnesene during the entire measurement period and additionally isoprene only in May. Quercus robur showed isoprene emission variations according to the seasonal cycle with rates of 30, 106 and 29 µg gDW −1 h−1 in May, August and October, respectively. Apart from isoprene, (E)-β-ocimene and β-caryophyllene were emitted through the entire experimental period. [ABSTRACT FROM AUTHOR]

Chalara fraxinea, the cause of ash dieback, is present in many European countries and constitutes a severe threat to Fraxinus spp. in forests, urban areas and nurseries. This study investigated tissue colonisation strategies of the parasite in Common ash at ultrastructural level and demonstrated that C. fraxinea develops intracellularly, moving through the cells and easily colonising the phloem, paratracheal parenchyma and parenchymatic rays. However, damage to either the plasmalemma or cell walls was not observed under our experimental conditions. Furthermore, the presence of intrahyphal hyphae was frequently detected, which are likely associated with a regeneration mechanism. [ABSTRACT FROM AUTHOR]

• Context: It has been estimated that about half of a plant's total hydraulic resistance is located belowground, but it is not well known how temperate tree species differ in root hydraulic properties and how these traits vary with the species' drought tolerance. • Aims: We examined root anatomical and hydraulic traits in five broad-leaved tree species with different drought tolerance, analyzed the relation between root anatomy and hydraulic conductivity and root embolism, and investigated the relation of these traits to the species' drought tolerance. • Methods: In small-diameter roots (2-6 mm), we measured vessel diameters and vessel density, specific hydraulic conductivity, and the percental loss of conductivity ('native' embolism) during summer in a mixed forest. • Results: Specific conductivity was positively related to vessel diameter but not to vessel density. Drought-tolerant Fraxinus showed the smallest mean vessel diameters and drought-sensitive Fagus the largest. Specific conductivity was highly variable among different similar-sized roots of the same species with a few roots apparently functioning as 'high-conductivity roots'. • Conclusion: The results show that coexisting tree species can differ largely in root hydraulic traits with more drought-sensitive trees apparently having larger mean vessel diameters in their roots than tolerant species. However, this difference was not related to the observed root conductivity losses due to embolism. [ABSTRACT FROM AUTHOR]

Tree ring analysis investigates growth processes at time horizons of several weeks to millennia, but lacks the detail of shortterm fluctuation in cambial activity. This study used electronic high-precision dendrometry for analyzing the environmental factors controlling stem diameter variation and radial growth in daily resolution in five co-existing temperate broad-leaved tree species (genera Fraxinus, Acer, Carpinus, Tilia and Fagus) with different growth and survival strategies. Daily stem radius change (SRCd) was primarily influenced by the atmospheric demand for water vapor (expressed either as vapor pressure deficit (D) or relative air humidity (RH)) while rainfall, soil matrix potential, temperature and radiation were only secondary factors. SRCd increased linearly with increasing RH and decreasing D in all species. The positive effect of a low atmospheric water vapor demand on SRCd was largest in June during the period of maximal radial growth rate and persisted when observation windows of 7 or 21 days instead of 1 day were used. We found a high synchronicity in the day-to-day growth rate fluctuation among the species with increment peaks corresponding to air humidity maxima, even though the mean daily radial growth rate differed fivefold among the species. The five species also differed in the positive slope of the growth/RH relationship with the steepest increase found in Fraxinus and the lowest in Fagus. We explain the strong positive effect of high RH and low D on radial stem increment by lowered transpiration which reduces negative pressure in the conducting system and increases turgor in the stem cambium cells, thereby favoring cell division and expansion. The results suggest that mechanistic models of tree growth need to consider the atmospheric water status in addition to the known controlling environmental factors: temperature, soil moisture and precipitation. The results further have implications for sensitivity analyses of tree growth to climatic changes. [ABSTRACT FROM AUTHOR]

Cambial injury has been reported to alter wood structure in broad-leaved trees. However, the duration and extension of associated anatomical changes have rarely been analysed thoroughly. A total of 18 young European ash (Fraxinus excelsior L.) trees injured on the stem by a spring flood were sampled with the aim of comparing earlywood vessels and rays formed prior to and after the scarring event. Anatomical and hydraulic parameters were measured in five successive rings over one-quarter of the stem circumference. The results demonstrate that mechanical damage induces a decrease in vessel lumen size (up to 77%) and an increase in vessel number (up to 475%) and ray number (up to 115%). The presence of more earlywood vessels and rays was observed over at least three years after stem scarring. By contrast, abnormally narrow earlywood vessels mainly developed in the first ring formed after the event, increasing the thickness-to-span ratio of vessels by 94% and reducing both xylem relative conductivity and the index for xylem vulnerability to cavitation by 54% and 32%, respectively. These vessels accumulated in radial groups in a 30° sector immediately adjacent to the wound, raising the vessel grouping index by 28%. The wound-induced anatomical changes in wood structure express the functional need of trees to improve xylem hydraulic safety and mechanical strength at the expense of water transport. Xylem hydraulic efficiency was restored in one year, while xylem mechanical reinforcement and resistance to cavitation and decay lasted over several years. [ABSTRACT FROM PUBLISHER]

The phenolic composition of heartwood extracts from Fraxinus excelsior L. and F. americana L., both before and after toasting in cooperage, was studied using LC-DAD/ESI-MS/MS. Low-molecular weight (LMW) phenolic compounds, secoiridoids, phenylethanoid glycosides, dilignols and oligolignols compounds were detected, and 48 were identified, or tentatively characterized, on the basis of their retention time, UV/Vis and MS spectra, and MS fragmentation patterns. Some LMW phenolic compounds like protocatechuic acid and aldehyde, hydroxytyrosol and tyrosol, were unlike to those for oak wood, while ellagic and gallic acid were not found. The toasting of wood resulted in a progressive increase in lignin degradation products with regard to toasting intensity. The levels of some of these compounds in medium-toasted ash woods were much higher than those normally detected in toasted oak, highlighting vanillin levels, thus a more pronounced vanilla character can be expected when using toasted ash wood in the aging wines. Moreover, in seasoned wood, we found a great variety of phenolic compounds which had not been found in oak wood, especially oleuropein, ligstroside and olivil, along with verbascoside and isoverbascoside in F. excelsior, and oleoside in F. americana. Toasting mainly provoked their degradation, thus in medium-toasted wood, only four of them were detected. This resulted in a minor differentiation between toasted ash and oak woods. The absence of tannins in ash wood, which are very important in oak wood, is another peculiar characteristic that should be taken into account when considering its use in cooperage. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Several studies have demonstrated a range of effects of outdoor UV-B supplementation during the growing season on leaf chemistry including carbohydrate extractability and on the subsequent decomposition of leaf litter. However, this study investigates the effects of several levels of UV radiation on leaf carbohydrate chemistry and subsequent decomposition using filtration of ambient sunlight. Fraxinus excelsior seedlings were grown outdoors in the UK under ambient solar irradiation and under filtration treatments which excluded either UV-B or both UV-A and UV-B. After one year of decomposition in the litter layer of a mixed semi-natural woodland, the loss of dry mass was 10% greater, relative to starting mass, in the leaves which had received no UV at all or no UV-B throughout the growing season (P <0.05). Analysis of the cell wall material before decomposition revealed no significant trends in total carbohydrate and lignin content with UV exclusions, no change in foliar nitrogen and C-to-N ratio and a 2% increase in foliar carbon (P <0.05) only with the combined exclusion of UV-A and UV-B. A sequential extraction of carbohydrate with a series of extractants (phosphate buffer, ammonium oxalate, urea, sodium hydroxide and formic acid) showed no trends with UV exclusions but digestion with the fungal enzyme mixture Driselase revealed that exclusion of UV-B only caused rhamnose and mannose residues of the cell-wall polysaccharides to resist Driselase digestion whist exclusion of all UV had the opposite effect. Whereas some studies have reported that elevated UV-B radiation from lamp supplementation can increase rates of subsequent leaf decomposition, the higher UV-B levels in the ambient controls of this filtration study resulted in 29% lower decomposition rates than the filtered-UV treatments. [Copyright &y& Elsevier]

Abstract: The ascomycete fungus Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea) is responsible for ash dieback currently expanding over large parts of Europe. Our objective was to investigate the genetic structure of H. pseudoalbidus and to examine its relationship to the species H. albidus, known as a saprotroph. The study comprised 181 isolates of H. pseudoalbidus collected within the diseased area, 17 H. albidus isolates from six apothecia, collected outside the diseased area in Norway, and nine apothecia of H. pseudoalbidus collected in Sweden. By analysis of microsatellite markers developed for this study, combined with AP-PCR using the M13 primer, we demonstrated sexual heterothally in H. pseudoalbidus, detected high gene flow and low geographic structure of the H. pseudoalbidus population and found indications of a founder effect. Also, substantial genetic differences were detected between the two species of fungi; only four of seven microsatellite markers developed for H. pseudoalbidus were amplified for H. albidus, and no alleles were shared among the species. Furthermore, AP-PCR banding patterns were distinctly different for the two species. We conclude that even though the two fungi have a similar habitat and are morphologically virtually identical, they do not share a recent common ancestor. [Copyright &y& Elsevier]

Background: Treatment of rheumatic or musculoskeletal disorders (MD) is multi-disciplinary and includes herbal analgesics. Although already reviewed, no quantitative evaluation of efficacy and safety of the herbal combination Phytodolor® (STW1) is available. Methods: We searched in databases and contacted authors and the manufacturer to identify randomized controlled trials (RCTs) examining STW1 in patients with MD. We made a reanalysis of raw data of eligible published and unpublished RCTs and pooled the results for meta-analysis according to Cochrane guidelines and intention-to-treat. Primary outcome measure was patient global assessment of efficacy, secondary outcome measure was pain at rest and on movement. Results were stratified according to treatment groups. Results: Patient data of 11 RCTs were eligible for pooling. In the entire population, STW1 was significantly superior compared to placebo in patients' global assessment of efficacy (group difference for rating very good/good: 20%; placebo 48.9% and STW1 69.1%; p < 0.001; OR 0.43; 95% CI 0.28-0.65) and in the subpopulation 'other rheumatic diseases' (placebo 45.4%; STW1 72.3%; p < 0.001; OR 0.32; 95% CI 0.2-0.52), but not in the subpopulation 'gonarthrosis'. STW1 did not differ significantly compared to non-steroidal anti-inflammatory drugs (NSAIDs), neither in the entire population nor the subpopulations. Similar results were found for pain at rest and on movement. No serious adverse events (AE) but minor AE were reported (placebo 8.1%; STW1 14.2%; NSAIDs 18.9%). Conclusion: According to the analysed data, STW1 showed a better pain reduction than placebo in patients with pain due to MD, probably equivalent to NSAIDs, and was well tolerated. Copyright © 2011 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Fraxinus excelsior, common ash native to Europe, is threatened by a recently identified pathogenic fungus Chalara fraxinea, which causes extensive damage on ash trees across Europe. In Denmark, most stands are severely affected leaving many trees with dead crowns. However, single trees show notably fewer symptoms. In this study, the impact of the emerging infectious disease on native Danish ash trees is assessed by estimating presence of inherent resistance in natural populations. Disease symptoms were assessed from 2007 to 2009 at two different sites with grafted ramets of 39 selected clones representing native F. excelsior trees. A strong genetic variation in susceptibility to C. fraxinea infections was observed. No genetic or geographic structure can explain the differences, but strong genetic correlations to leaf senescence were observed. The results suggest that a small fraction of trees in the Danish population of ash possess substantial resistance against the damage. Though this fraction is probably too low to avoid population collapse in most natural or managed ash forests, the observed presence of putative resistance against the emerging infectious disease in natural stands is likely to be of evolutionary importance. This provides prospects of future maintenance of the species through natural or artificial selection in favour of remaining healthy individuals. [ABSTRACT FROM AUTHOR]

Wooded meadows with a history of traditional land use over thousands of years support a great diversity of various taxa. Today, however, high-species-rich communities in wooded meadows are threatened because of the cessation of traditional management in large areas. We studied lichen communities on 136 deciduous trees (Betula spp., Fraxinus excelsior and Quercus robur) in 12 wooded meadows in three regions of Estonia, and assessed the effect of habitat change due to the abandonment of traditional management on epiphytic lichen species composition, considering factors on three spatial scales: regional, habitat and individual tree. The variation partitioning approach in partial Canonical Correspondence Analysis (pCCA) revealed that most of the variation in species composition is described by the species of host tree and tree bark pH. Other tree level variables, foremost tree diameter, described as much of the compositional variation as geographic location (region) or environmental conditions in wooded meadows. Of the environmental factors studied, woodland canopy cover is the strongest predictor of the change in epiphytic lichen species composition from the community type of semi-open wooded meadows to species-poor communities characteristic of secondary forest. General Linear Model (GLM) analysis of the abundance of the 35 most frequently observed lichen species revealed that more than half of them (21) are influenced by site openness (canopy cover and/or undergrowth density), showing that increasing canopy cover has a negative effect on the abundance of epiphytic lichen species characteristic of traditionally managed semi-open wooded meadows. The results emphasize that the preservation of large old deciduous trees of various species and the maintenance of the semi-open structure of stands are vitally important for the protection of epiphytic lichen communities in wooded meadows. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: The aim of this study was to determine whether a Fraxinus excelsior L. seed extract, FraxiPure™ (0.5% in the diet), limits weight gain and hyperglycemia in mice. In a previous report, we identified several secoiridoids in FraxiPure™, some of which activated peroxisome proliferator-activated receptor alpha (PPARα) in vitro and inhibited the differentiation of 3T3-L1 preadipocyte cells. In a separate study, FraxiPure™ reduced glycemia in healthy volunteers, following an oral glucose tolerance test. These findings suggest that FraxiPure™ has antiobesity and antihyperglycemia effects. Materials and methods: FraxiPure™ was tested in mice that were fed a high-fat diet over 16 weeks and compared with low-fat and high-fat diet controls. Weight gain, omental and retroperitoneal fat, fasting blood glucose, and fasting blood insulin were measured. Results: FraxiPure™ reduced gains in body weight by 32.30% (p <0.05), omental fat by 17.92%, and retroperitoneal fat by 17.78%. FraxiPure™ also lowered fasting blood glucose levels by 76.52% (p <0.001) and plasma insulin levels by 53.43% (p <0.05) after 16 weeks. Moreover, FraxiPure™ lowered liver weight gains by 63.62% (p <0.05) and the incidence of fatty livers by 66.67%. Conclusions: Our novel results demonstrate the antiobesity effects of chronic administration of an F. excelsior seed extract and confirm its ability to regulate glycemia and insulinemia. In addition, this extract, which is rich in secoiridoid glucosides, protects against obesity-related liver steatosis. [Copyright &y& Elsevier]

Dieback of Fraxinus excelsior L. associated with Chalara fraxinea is observed in Europe, and in some areas dying trees exhibit symptoms of root and butt rot. Our study was conducted (1) to estimate the impact of the rot on F. excelsior dieback severity; (2) to identify fungi colonizing roots of dieback-affected trees; (3) to check their pathogenicity to F. excelsior; and (4) to estimate sprouting incidence and sprout health condition in relation to presence/absence of rot. The extent of rot was measured in 33 trees with different dieback intensity, 150 fungal isolations were attempted from roots of 50 trees, 26 fungi were tested for pathogenicity to 286 saplings, and sprouting was evaluated for 328 stumps on three clear-felled sites. Root rot was mainly caused by Armillaria cepistipes, and the extent of rot correlated positively with dieback severity although it played a secondary role in tree decline. Four years after tree felling, root rot had a negative impact on sprouting frequency, yet rot did not enter sprouts from stumps, and when experimentally inoculated, fungi associated with root rot in mature ash had no visible impact on tree vigor, showing that after formation of sprouts, rot does not affect the subsequent phytosanitary condition. Sprouts on investigated sites exhibited Chalara dieback symptoms on leaves and bark irrespectively of presence/absence of rot, indicating that vigorous natural regeneration of F. excelsior in dieback-affected areas could not be expected. [ABSTRACT FROM AUTHOR]

Abstract: The deposition of atmospheric elements on and into the bark of 4-year-old Fraxinus excelsior L. was studied. The elemental composition of the suber tissue was established through ICP-MS analysis and the presence of solid mineral particles included in this suber was established and described through SEM-EDX. Fractionation of the suber elements mixture was obtained after ashing at 550°C through successive water (C fraction) and HNO3 2M (D fraction) extraction, leading to an insoluble residue mainly composed of the solid mineral particles (E fraction). The triplicated % weight of C, D and E were respectively 34.4 ±2.7, 64.8±2.7 and 0.8±0.1% of the suber ashes weight. The main component of C was K, of D was Ca. Noticeable amounts of Mg were also observed in D. The E fraction, composed of insoluble particles, was mostly constituted of geogenic products, with elements such as Si, Al, K, Mg, representing primary minerals. E also contained Ca3(PO4)2 and concentrated the main part of Pb and Fe. Moreover, The SEM-EDX analysis evidenced that this fraction also concentrated several types of fly ashes of industrial origin. The study of the distribution between C, D and E was analysed through ICP-MS with respect to their origin. The origin of the elements found in such bark was either geogenic (clay, micas, quartz…), anthropogenic or biogenic (for instance large amounts of solid Ca organic salts having a storage role). As opposed to the E fraction, the C fraction, mainly composed of highly soluble K+ is characteristic of a biological pool of plant origin. In fraction D, the very high amount of Ca++ corresponds to two different origins: biological or acid soluble minerals such as calcite. Furthermore, the D fraction contains the most part of pollutants of anthropic origin such as Zn, Cu, Ni, Co, Cd. As a whole, the fractionation procedure of the suber samples allows to separate elements as a function of their origin but also gives valuable information on distribution and speciation of trace elements. [Copyright &y& Elsevier]

Under natural conditions pollen vectors act stochastically, and the order in which pollen arrives can influence seed paternity. In a number of wind-pollinated taxa, however, fertilization does not occur immediately. It has been proposed that delayed fertilization promotes pollen competition by providing a "fair start" for pollen tubes. To test this hypothesis we compared paternity after simultaneous and consecutive pollinations with multiple donors in Fraxinus excelsior. Additionally, we investigated pollen tube growth in naturally pollinated flowers. Under natural conditions pollen grains arrived on the stigma one by one, and their mean number reached 6 after 10 d of anthesis. A pollen tube from the first-arriving pollen grain entered the style after 24 h and reached the base on the second day following pollination. Fertilization by nuclei from the same firstarriving pollen tube occurred after stigma necrosis about 3 wk later. Paternity tests confirmed that pollen applied first in the experimental pollinations had an overwhelming advantage over pollen applied 24 h later. As delayed fertilization does not play a role in prezygotic selection in this species, flowering phenology might be more important for paternity success than pollen tube growth performance. [ABSTRACT FROM AUTHOR]

Abraxas pantaria (L.) (Lepidoptera: Geometridae), the spotted ash looper (Light Magpie), is recognized as a new pest of common ash, Fraxinus excelsior (L.) in the eastern part of Turkey. Description of different developmental stages of A. pantaria is given. Its development, biology, damage, and parasitoids were studied in the field (Aras Valley, Karakurt, Sarıkamış, Kars Province) and partly in the laboratory during 2004-2006. In the field adults started to appear at the end of June and were seen until the middle of August. The eggs were laid mostly on the lower sides of leaves adjacent to the midrib in single layer batches. The newly hatched caterpillars fed on lower epidermis and parenchyma tissue till becoming third instar, leaving a network of veins on the upper epidermis. Then the caterpillars dispersed and started feeding on the edges of the leaves. The full grown caterpillars hanged down by means of silky threads and entered the soil to pupate. Abraxas pantaria had one generation per year in the ecological conditions of Karakurt, and overwintered as pupa in the soil. As the parasitoid Cotesia callimone (Nixon) (Braconidae) was reared from the caterpillar of A. pantaria. Coelichneumon sp. and Cratichneumon fabricator F. (Ichneumonidae) emerged from overwintered pupae. Pales pavida (Meigen) [Tachinidae] was reared from the pupae in the fall. Both braconid and ichneumonid species were reared from A. pantaria for the first time. [ABSTRACT FROM AUTHOR]

This study provides a unique large dataset of total epiphytic lichen diversity (fruticose, foliose and crustose species) and composition on 1,294 trees of 17 tree species in wooded meadows in Sweden and Estonia, the Baltic region. The inventory (25,380 observations and 246 lichen taxa) clearly illustrated that Ulmus minor, Quercus robur and Fraxinus excelsior contributed most significantly to epiphytic lichen richness and number of red-listed species. In Sweden, average single tree α richness was 22.2 on Ulmus (only in Sweden), 21.6 on Quercus (25.0 in Estonia) and 19.8 on Fraxinus (16.7 in Estonia), respectively. Ulmus hosted on average one red-listed species per tree, compared with 0.7 on Fraxinus (0.6 in Estonia), 0.4 on Quercus (0.7 in Estonia) and only 0.05 on Betula (same in Estonia). Lichen species composition and the average number of red-listed lichens were influenced by tree diameter on Fraxinus and Quercus, whilst no such pattern was evident on Ulmus. Randomized species accumulation curves of the dominating tree species illustrated that Fraxinus, Quercus and Ulmus supported α dominated lichen communities where individual trees hosted a substantial part of the total richness. Betula, on the other hand, supported β dominated communities where individual trees tended to be dissimilar and, therefore, more of the total richness existed as species turnover among host trees. Lichen species composition was influenced by tree species, and most notably, lichen species on Ulmus had a strong consistent clumping in ordination graphs, with many rare and red-listed lichens. The broadleaved deciduous trees within the wooded meadows clearly contribute greatly to the biodiversity of the Baltic region. [ABSTRACT FROM AUTHOR]

The periodic production of large seed crops by trees (masting) and its interaction with stem growth has long been the objective of tree physiology research. However, very little is known about the effects of masting on stem growth and total net primary productivity (NPP) at the stand scale. This study was conducted in an old-growth, mixed deciduous forest dominated by Fagus sylvatica (L.) and covers the period from 2003 to 2007, which comprised wet, dry and regular years as well as two masts of Fagus and one mast of the co-dominant tree species Fraxinus excelsior (L.) and Acer pseudoplatanus (L.). We combined analyses of weather conditions and stem growth at the tree level (inter- and intra-annual) with fruit, stem and leaf production, and estimates of total NPP at the stand level. Finally, we compared the annual demand of carbon for biomass production with net canopy assimilation (NCA), derived from eddy covariance flux measurements, chamber measurements and modelling. Annual stem growth of Fagus was most favoured by warm periods in spring and that of Fraxinus by high precipitation in June. For stem growth of Acer and for fruit production, no significant relationships with mean weather conditions were found. Intra-annual stem growth of all species was strongly reduced when the relative plant-available water in soil dropped below a threshold of about 60% between May and July. The inter-annual variations of NCA, total NPP and leaf NPP at the stand level were low (mean values 1313, 662 and 168 g C m−2 year−1, respectively), while wood and fruit production varied more and contrarily (wood: 169–241 g C m−2 year−1; fruits: 21–142 g C m−2 year−1). In all years, an annual surplus of newly assimilated carbon was calculated (on average 100 g C m−2 year−1). The results suggest that stem growth is generally not limited by insufficient carbon resources; only in mast years a short-term carbon shortage may occur in spring. In contrast to common assumption, stem growth alone is not a sufficient proxy for total biomass production or the control of carbon sequestration by weather extremes. [ABSTRACT FROM PUBLISHER]

The demand for hardwood seedlings has increased in recent years in Italy, particularly for tree farming programmes oriented towards quality wood production; the availability of high-quality seedlings is a crucial step towards being successful in establishing such productive plantations. The aim of this work was to identify the most important morphological seedling quality attributes. Nursery stock consisting of 1-year-old bareroot Fraxinus excelsior seedlings was evaluated for field performance at the end of the first growing season on a plantation site in the Po Valley, northern Italy, in relation to the objective of producing high-quality timber plantations. The approach consisted of (1) morphological characterization (i.e. stem height, root collar diameter, shoot and root architecture) of the seedlings before outplanting; (2) morphological assessment (including root excavations) of the plants after the first year of field growth; (3) relating attributes observed during phases (1) and (2); and (4) identifying those morphological characteristics that effectively predict outplanting success. The results indicate that the highest quality seedlings are best selected on the basis of initial shoot height and root system morphological type (i.e. stem heights 40-50 cm with a fasciculate root system of at least 40 cm length and rich in fine roots). Planting these seedling morphological types may dramatically improve field performance (i.e. more than 100% increase of height increment in this case), which will help to promote the development of afforestation plantations oriented towards high-quality wood production. [ABSTRACT FROM AUTHOR]

Current forestry policy promotes the use of local seed for new plantings, on the assumption that local material may be better adapted to local conditions. However, landscape-scale genetic studies which are necessary to underpin conservation and breeding strategies are often lacking. We investigated molecular diversity in common ash ( Fraxinus excelsior L .) sampled from 42 British and six French sites with microsatellites. Chloroplast haplotype H04 was the most common and widespread in Britain, although rare and localized individuals with H02 and H09 were also detected. In addition, three new chloroplast haplotypes were identified, and these were rare and highly localized. In terms of nuclear microsatellite markers, allelic richness differed between sites and decreased in an east to west direction. Differentiation between sites was often very low (mean FST 0.025), indicating few differences between the majority of sites. There was a clear excess of homozygotes (mean HO 0.669, mean HE 0.818) and a relatively high FIS (mean 0.182), suggests a consistent level of inbreeding or a widespread Wahlund effect in many F. excelsior sites. Gene pool ancestry analysis suggested that the majority of British F. excelsior belongs to a single meta-population which covers mainland western and central Europe. Three northern and western sites diverged markedly from the dominant population, and may represent remnants of two late potential Ice Age refugia in northern Britain. The data provide new information which will aid development of appropriate conservation policies for ash and other wind pollinated tree species. [ABSTRACT FROM AUTHOR]

The structure andd ynamics of a submontane alluvial forest, with structural attributes of old-growth, in the Sudety Mts, Central Europe were examined. Stand structure was measured in circular sampling plots, and the distribution of gaps in belt transects. Past dynamic was reconstructed on the basis of analysis of events of release from suppression by inspection of growth pattern. The age distribution of canopy trees was also surveyed. The stand was dominated by ashes (Fraxinus excelsior) aged77-151 years, which created the upper layer, whereas the lower layer was dominated by dense hazel (Corylus avellana) shrubs. The analysedstandwas developedin site which was usedas a grasslandin first quarter of XIX century, but its history include several fine-scale disturbances when canopy trees were established. Recent dynamic was related to low intensity gap formation. The light conditions at the forest floor were good, and the average percentage of PPFD was 13%. Seedlings of ash and sycamore (Acer pseudoplatanus) were abundant throughout the stand. However, continuous browsing by game prevented growth of seedlings; in the sapling layer sycamore had disappeared and the number of ash saplings was strongly reduced. Regeneration was dominated by hazel of vegetative origin both in gaps and under the canopy. [ABSTRACT FROM AUTHOR]

Background: In general, females of woody dioecious plants are expected to grow more slowly than males because of the high cost associated with fruit bearing. Yet wind-pollinated species may invest relatively heavily in male reproduction, and various compensatory mechanisms can offset incurred costs, therefore the apparent growth of genders might be similar over a longer period of time. Any cost-related disparities are expected to be most pronounced in mast flowering years, when female reproductive resource demand is highest. Aims: We aimed to investigate gender-related response in relation to the cost of reproduction, and as a function of climate. Methods: Using dendrochronology techniques and analysing growth parameters at the branch level, we compared long-term and seasonal growth of male and female Fraxinus excelsior trees. Results: There was no observed decline in trunk growth of either of the genders over a 55-year period, but male and female trees had distinguishable annual growth patterns. The tree-ring widths of both genders were smaller in masting years than in other years. The difference between genders could be explained by their response to different climatic variables: females are more sensitive to spring frost and drought in early summer, while male growth depends more on late summer conditions. Conclusions: Vegetative development and flowering create a feedback system that minimises the cost of reproduction and assures that expenses are covered. Hence, growth differences between genders may be related to their phenological and physiological disparities rather than reproductive cost differences per se. [ABSTRACT FROM AUTHOR]

The article focuses on a study on the presence of bacteria associated with mixed woodland of English oak and common ash on a trichloreothylene (TCE)-contaminated ground water plume. The researchers found sharp decreases in TCE concentrations in the area, while transects outside the area did not show the decrease. The researchers investigated bacterial communities of both the tree species to assess their use in common native tree species and their associated bacteria for phytoremediation.

Abstract: This paper discusses determinants of the historical and current spatial extent of the floodplain forest in Leipzig as well as its tree species composition using a GIS-data based delineation model and historical forest inventories for the floodplain forest in the district of Leipzig in Germany from the 19th to the 20th century. We found that the spatial extent of the floodplain forest remained considerably stable in spite of an overall decline in the entire floodplain area from the period where the city first experienced industrialisation in the 19th century to now. However, with river regulations and the alteration of forest management from coppice-with-standards forest to high forest in the 19th century, major changes can be found in the tree species composition of the floodplain forest. Comparing these findings with references from other European floodplain forests we discuss the impact of historical and current forest management as well as the city location''s influence on the extent and tree species composition of urban floodplain forests. For urban forest management in particular there is a great need to integrate biophysical, historical and forestry knowledge when predicting future developmental trends. [Copyright &y& Elsevier]

This paper compares vegetation composition, light availability, carbon and nutrient pools and Ellenberg indicator values among four old-field successional permanent plots that have received an initial treatment (ploughing, herbicide or sterilisation) prior to being left undisturbed in 1969, a second set of six plots received additional treatments (continued ploughing or mulching until 1982). On all plots species rich pioneer forests developed. Vegetation still varies among plots with different initial treatments: Sterilised plots can be distinguished from the others by dominance of Betula pendula, ploughed plots by Fraxinus excelsior, whereas herbicide-treated plots are intermediate with proportions of both species. By affecting light availability at the ground, tree species in turn influences ground vegetation and soil properties. Light availability turned out to be the dominant factor determining the composition of the vegetation in old-field succession. [ABSTRACT FROM AUTHOR]

Abstract: In Europe, remnants of formerly widespread natural mixed forests are rare. We analyzed an exceptionally tall tree stand with a very high wood volume in Hrončokovský grúň reserve, covering 55.2ha in Slovenské Rudohorie Mountains in central Slovakia (48°43′N and 19°35′E) between 730 and 1050m a.s.l. We compared our data to other natural stands to see if the growing stock and tree height were higher in Hrončokovský grúň. Fifty-four circular plots of 0.05ha each and spaced at 100m×100m distance sampled the entire reserve. Within each plot, live and dead trees were measured. Number, basal area and volume of live trees and volume of CWD were calculated. Moreover, measurements of the tallest trees were conducted in the whole reserve area. Total volume of live trees and CWD in the studied reserve was 1030m3 per hectare. It is the second highest value ever recorded in an area of several hectares or larger in European forests. The feature that makes the stand in Hrončokovský grúň a unique one is the height of trees. In the whole reserve, about 600 trees exceeded the height of 45m. Individuals of three deciduous species (Acer pseudoplatanus, Fraxinus excelsior, Ulmus glabra) are the tallest ones found in unmanaged forests in the whole Europe. Those of Fagus sylvatica reached height near the maximum value ever recorded. In Europe, stands of average total live and dead wood volume above 1000m3 ha−1 with numerous trees above 40m tall were probably very rare even several centuries ago, when virgin forests were widespread. Most likely, they were confined to rather small mountain areas, where rich soils supporting high stand productivity occurred along with wind-protected slopes, where natural disturbances were rare and stand turnover rate was low. [Copyright &y& Elsevier]

Abstract: Plant–plant and plant–soil interactions play a key role in determining plant community structure and ecosystem function. However, the effects of global change on the interplay between co-occurring plants and soil microbes in successional communities are poorly understood. In this study, we investigated competition for nitrogen (N) between soil microorganisms, grass plants and establishing tree seedlings under factorial carbon dioxide (CO2) and N treatments. Fraxinus excelsior seedlings were germinated in the presence or absence of grass competition (Dactylis glomerata) at low (380μmolmol−1) or high (645μmolmol−1) CO2 and at two levels of N nutrition in a mesocosm experiment. Pulse 15N labelling was used to examine N partitioning among plant and soil compartments. Dactylis exerted a strong negative effect on Fraxinus biomass, N capture and 15N recovery irrespective of N and CO2 treatment. In contrast, the presence of Dactylis had a positive effect on the microbial N pool. Plant and soil responses to N treatment were of a greater magnitude compared with responses to elevated CO2, but the pattern of Fraxinus- and microbial-N pool response to N and CO2 varied depending on grass competition treatment. Within the Dactylis competition treatment, decreases in Fraxinus biomass in response to N were not mirrored by decreases in tree seedling N content, suggesting a shift from below- to above-ground competition. In the Dactylis-sown pots, 15N recovery could be ranked Dactylis >microbial pool> Fraxinus in all N and CO2 treatment combinations. Inequalities between Fraxinus and soil microorganisms in terms of 15N recovery were exacerbated by N addition. Contrary to expectations, elevated CO2 did not increase plant–microbe competition. Nevertheless, microbial 15N recovery showed a small positive increase in the high CO2 treatment. Overall, elevated CO2 and N supply did not interact on plant/soil N partitioning. Our data suggest that the competitive balance between establishing tree seedlings and grass plants in an undisturbed sward is relatively insensitive to CO2 or N-induced modifications in N competition between plant and soil compartments. [Copyright &y& Elsevier]

The species richness and composition of lichens was quantified for four temperate broad-leaved tree species (Acer platanoides, Fraxinus excelsior, Tilia cordata and Ulmus glabra) in boreo-nemoral forests on the talus slope of the North-Estonian limestone escarpment (North-Estonian Klint). Thirteen study sites were distributed along the klint on a west to east gradient. The effects of tree and stand characteristics and geographical location of a stand on composition and diversity of epiphytic lichens were evaluated by multivariate analyses (DCA, CCA, pCCA) and by general linear mixed models (GLMM). Tree level variables (e.g. bark pH, bryophytes cover and host tree species) explained the largest fraction of the variation in lichen species composition. However, species richness and composition were significantly influenced also by the unique habitat conditions of klint forest (length of the forest fragment, proximity of the stand to the sea and height of the escarpment). A significant correlation between stand locality and lichen diversity on the tree bole was found which is most likely related to local air pollution gradients caused by alkaline cement dust and acid pollutants in the north-eastern part of Estonia. [ABSTRACT FROM AUTHOR]

Development of effective biocontrol procedures using ash endophytes to combat an ash pathogen Hymenoscyphus fraxineus would be an appropriate contribution to the ongoing effort to protect European ash stands against ash decline. In this study we investigated the biocontrol potential of two ash endophytes, Thielavia basicola and Minimidochium sp., against H. fraxineus using in vitro plant-fungus and fungus-fungus dual cultures approach in three biocontrol models. The tests aimed to determine whether the endophytes show antagonism toward Fraxinus excelsior and F. pennsylvanica, to assess the level of antagonism of the endophytes toward H. fraxineus and to identify potential secondary metabolites induced by the presence of H. fraxineus. The results that dual culture experiments modeled according to our design may be a very useful tool to precisely study biocontrol potential of fungi, i.e., without the impact of environmental factors. Such experiments also enable the selection of most resistant ash genotypes and rapid propagation, producing large numbers of pathogen-free seedlings. It should be noted, however, that both of the endophytes tested in the dual cultures strongly inhibited the growth of H. fraxineus. Their growth under the influence of callus/seedlings was also inhibited. Comparison of HPLC profiles showed that the presence of H. fraxineus in the post-culture medium induced the production of an unknown secondary metabolite in this species. Such results suggest that some of the plant–fungus combinations examined in this study may have potential to be developed as biocontrol methods, thus increasing the survivability of ash stands under natural conditions. [ABSTRACT FROM AUTHOR]