Mature Beech Trees Research Articles

40 Jahre Umweltmonitoring im Einflussgebiet einer Kehrichtverbrennungsanlage

40 years of environmental monitoring in the area of influence of a waste incineration plant The waste incineration plant (WIP) of Niederurnen (canton of Glarus, Switzerland) was opened at the end of 1973. It is situated in a plain at the foot of a mountain slope covered with beech trees. In the context of the licensing procedure, the local community requested a monitoring program to document the effects the plant would have on the environment. As a consequence, starting in 1971, three examples of sampling were carried out before the WIP came into operation at the end of 1973 and a monitoring program on the basis of the analysis of chloride, heavy metals and other elements in the leaves of mature beech trees was started. At 22 sites around the plant, leaves were harvested annually over a period of 40 years. Initially, the plant system had only simple flue-gas cleaning. Following Swiss air pollution control legislation, the cleaning system was improved in several steps. These improvements resulted in marked decreases in the concentrations of foliar chloride and zinc. Foliar chloride (and zinc) concentration may be considered as a good bioindicator for the environmental effects of a WIP.

Subcellular nutrient element localization and enrichment in ecto- and arbuscular mycorrhizas of field-grown beech and ash trees indicate functional differences.

Mycorrhizas are the chief organ for plant mineral nutrient acquisition. In temperate, mixed forests, ash roots (Fraxinus excelsior) are colonized by arbuscular mycorrhizal fungi (AM) and beech roots (Fagus sylvatica) by ectomycorrhizal fungi (EcM). Knowledge on the functions of different mycorrhizal species that coexist in the same environment is scarce. The concentrations of nutrient elements in plant and fungal cells can inform on nutrient accessibility and interspecific differences of mycorrhizal life forms. Here, we hypothesized that mycorrhizal fungal species exhibit interspecific differences in mineral nutrient concentrations and that the differences correlate with the mineral nutrient concentrations of their associated root cells. Abundant mycorrhizal fungal species of mature beech and ash trees in a long-term undisturbed forest ecosystem were the EcM Lactarius subdulcis, Clavulina cristata and Cenococcum geophilum and the AM Glomus sp. Mineral nutrient subcellular localization and quantities of the mycorrhizas were analysed after non-aqueous sample preparation by electron dispersive X-ray transmission electron microscopy. Cenococcum geophilum contained the highest sulphur, Clavulina cristata the highest calcium levels, and Glomus, in which cations and P were generally high, exhibited the highest potassium levels. Lactarius subdulcis-associated root cells contained the highest phosphorus levels. The root cell concentrations of K, Mg and P were unrelated to those of the associated fungal structures, whereas S and Ca showed significant correlations between fungal and plant concentrations of those elements. Our results support profound interspecific differences for mineral nutrient acquisition among mycorrhizas formed by different fungal taxa. The lack of correlation between some plant and fungal nutrient element concentrations may reflect different retention of mineral nutrients in the fungal part of the symbiosis. High mineral concentrations, especially of potassium, in Glomus sp. suggest that the well-known influence of tree species on chemical soil properties may be related to their mycorrhizal associates.

Differential responses of herbivores and herbivory to management in temperate European beech.

Forest management not only affects biodiversity but also might alter ecosystem processes mediated by the organisms, i.e. herbivory the removal of plant biomass by plant-eating insects and other arthropod groups. Aiming at revealing general relationships between forest management and herbivory we investigated aboveground arthropod herbivory in 105 plots dominated by European beech in three different regions in Germany in the sun-exposed canopy of mature beech trees and on beech saplings in the understorey. We separately assessed damage by different guilds of herbivores, i.e. chewing, sucking and scraping herbivores, gall-forming insects and mites, and leaf-mining insects. We asked whether herbivory differs among different forest management regimes (unmanaged, uneven-aged managed, even-aged managed) and among age-classes within even-aged forests. We further tested for consistency of relationships between regions, strata and herbivore guilds. On average, almost 80% of beech leaves showed herbivory damage, and about 6% of leaf area was consumed. Chewing damage was most common, whereas leaf sucking and scraping damage were very rare. Damage was generally greater in the canopy than in the understorey, in particular for chewing and scraping damage, and the occurrence of mines. There was little difference in herbivory among differently managed forests and the effects of management on damage differed among regions, strata and damage types. Covariates such as wood volume, tree density and plant diversity weakly influenced herbivory, and effects differed between herbivory types. We conclude that despite of the relatively low number of species attacking beech; arthropod herbivory on beech is generally high. We further conclude that responses of herbivory to forest management are multifaceted and environmental factors such as forest structure variables affecting in particular microclimatic conditions are more likely to explain the variability in herbivory among beech forest plots.

Mature beech trees (Fagus grandifolia; Fagaceae) are persistently clonal in coves and beech gaps in the Great Smoky Mountains

Angiosperms frequently have mixed sexual and asexual reproductive strategies, which can have significant consequences for population and community structure. Many tree species respond to disturbance by vegetative sprouting over sexual reproduction, but the ability to do so varies within and among species and is poorly studied. We tested the hypothesis that root sprouting in Fagus grandifolia is more important in high-elevation beech forests (extreme environmental conditions), relative to lower-elevation cove hardwood forests (optimal environmental conditions), in Great Smoky Mountains National Park. Four cove hardwood and two high-elevation beech gap forests were sampled. Fagus grandifolia trees were tagged, mapped, and genotyped at each site using six nuclear microsatellite loci. A subset of trees was cored to determine minimum ages of identified clonal lineages. Relationships between measures of clonal richness, diameter, forest type, and elevation were compared by nonparametric analyses. Five of six sites were highly dependent on sprouting; one site was entirely dependent on reproduction by seed. Clonal richness did not differ significantly by forest type or elevation, but differed significantly from previously published work. Tree diameter was significant by elevation and significant between the present study and previously published work. The results of this study in the context of previously published work suggest that relatively recent recruits may be more likely to reflect both sexual and asexual strategies, whereas mature F. grandifolia may be more likely to be the result of persistent clonal lineages.

Competition for nitrogen between adult European beech and its offspring is reduced by avoidance strategy

Plant growth, reproduction, and biomass allocation may be affected differently by nitrogen availability depending on tree size and age. In this context, competition for limited N may be avoided by different strategies of N acquisition between different vegetation components (i.e., seedlings, mature trees, other woody and herbaceous understorey). This study investigated in a field experiment whether the competition for N between different vegetation components in beech forests was prevented via seasonal timing of N uptake and affected by microbial N use. For this purpose, a removal approach was used to study the seasonal effects on N uptake and N metabolites in adult beech trees and beech natural regeneration, as well as soil microbial processes of inorganic N production and utilisation. We found that the competition for N between beech natural regeneration and mature beech trees was reduced by seasonal avoidance strategies (“good parenting”) of N uptake regardless of the N sources used. In spring, organic and inorganic N uptake capacity was significantly higher in beech seedlings compared to adult beech trees, whereas in autumn mature beech trees showed the highest N uptake rates. Removal of vegetation components did not result in changes in soil microbial N processes in the course of the growing season. Thus, N resources released by the removal of vegetation components were marginal. This consistency in soil microbial N processes indicates that competition between plants and soil microorganisms for N was not avoided by timing of acquisition during the vegetation period, but existed during the entire growing season. In conclusion, N nutrition in the studied forest ecosystem seems to be optimally attuned to European beech.

Leaf traits, shoot growth and seed production in mature Fagus sylvatica trees after 8 years of CO2 enrichment.

Masting, i.e. synchronous but highly variable interannual seed production, is a strong sink for carbon and nutrients. It may, therefore, compete with vegetative growth. It is currently unknown whether increased atmospheric CO(2) concentrations will affect the carbon balance (or that of other nutrients) between reproduction and vegetative growth of forest species. In this study, reproduction and vegetative growth of shoots of mature beech (Fagus sylvatica) trees grown at ambient and elevated atmospheric CO(2) concentrations were quantified. It was hypothesized that within a shoot, fruiting has a negative effect on vegetative growth, and that this effect is ameliorated at increased CO(2) concentrations. Reproduction and its competition with leaf and shoot production were examined during two masting events (in 2007 and 2009) in F. sylvatica trees that had been exposed to either ambient or elevated CO(2) concentrations (530 µmol mol(-1)) for eight consecutive years, between 2000 and 2008. The number of leaves per shoot and the length of terminal shoots was smaller or shorter in the two masting years compared with the one non-masting year (2008) investigated, but they were unaffected by elevated CO(2) concentrations. The dry mass of terminal shoots was approx. 2-fold lower in the masting year (2007) than in the non-masting year in trees growing at ambient CO(2) concentrations, but this decline was not observed in trees exposed to elevated CO(2) concentrations. In both the CO(2) treatments, fruiting significantly decreased nitrogen concentration by 25 % in leaves and xylem tissue of 1- to 3-year-old branches in 2009. Our findings indicate that there is competition for resources between reproduction and shoot growth. Elevated CO(2) concentrations reduced this competition, indicating effects on the balance of resource allocation between reproduction and vegetative growth in shoots with rising atmospheric CO(2) concentrations.

Seasonal ultrastructural changes in the cambial zone of beech (Fagus sylvatica) grown at two different altitudes

Seasonal structural changes of cambial cells in mature beech (Fagus sylvatica L.) trees growing at elevations of 400 m a.s.l. (lowland) and 1200 m a.s.l. (mountains) are presented on the basis of light (LM) and electron microscopy (TEM). For LM, samples from trees were collected at weekly intervals and for TEM at two-month intervals from March till September, 2008. LM enabled us to follow the production of new xylem and phloem cells that lasted for 16.5 ± 3.7 weeks at the lowland site and for 10.7 ± 1.3 weeks in the mountains. TEM revealed differences in ultrastructure of cambial cells in the phases of dormancy, reactivation, activity and transition to dormancy. The seasonal patterns of ultrastructural changes in cambial cells were similar at both sites but their timing was different. TEM revealed changes in the fine structure of cambial cells, indicating their activation in spring and the earliest stages of cell divisions and development of new cell walls. When using LM, the onset of cambial activity could be observed one month later, compared with TEM. LM therefore enabled us to follow cambial productivity but not the activity and related cytoplasmic modifications during reactivation.

Effects of abiotic and biotic stress on gene transcription in European beech ( Fagus sylvatica L.): From saplings to mature beech trees

Effects of abiotic and biotic stress on gene transcription in European beech ( Fagus sylvatica L.): From saplings to mature beech trees

Below-ground carbon allocation in mature beech and spruce trees following long-term, experimentally enhanced O 3 exposure in Southern Germany

Canopies of adult European beech ( Fagus sylvatica) and Norway spruce ( Picea abies) were labeled with CO 2 depleted in 13C to evaluate carbon allocation belowground. One-half the trees were exposed to elevated O 3 for 6 yrs prior to and during the experiment. Soil-gas sampling wells were placed at 8 and 15 cm and soil CO 2 was sampled during labeling in mid-late August, 2006. In beech, δ 13CO 2 at both depths decreased approximately 50 h after labeling, reflecting rapid translocation of fixed C to roots and release through respiration. In spruce, label was detected in fine-root tissue, but there was no evidence of label in δ 13CO 2. The results show that C fixed in the canopy rapidly reaches respiratory pools in beech roots, and suggest that spruce may allocate very little of recently-fixed carbon into root respiration during late summer. A change in carbon allocation belowground due to long-term O 3 exposure was not observed.

Transcriptional signatures in leaves of adult European beech trees ( Fagus sylvatica L.) in an experimentally enhanced free air ozone setting

Tropospheric ozone causes severe oxidative stress in plants. To investigate the transcriptional responsiveness of adult trees to ozone, fully-expanded sun and shade leaves of mature beech trees were harvested at four time points over the entire vegetation period in 2005 and 2006. Microarray analyses were conducted on leaves from trees grown in the field under ambient and twice-ambient ozone concentrations at Kranzberger Forst (Bavaria). Beech trees changed their transcript levels in response to ozone. In the years 2005 and 2006 different transcription patterns were observed; this may have been a result of different weather conditions and ozone uptake. Furthermore, we obtained differences in mRNA expression patterns between shade and sun leaves. In the ozone-treated sun leaves of 2005, slightly up- and down-regulated transcript levels were detected, particularly in the spring and autumn, whereas shade leaves clearly exhibited reduced mRNA levels, particularly at the end of the vegetation period. In 2006, this pattern could not be confirmed, and in the autumn, four other transcripts were slightly up-regulated in ozone-treated shade leaves. In addition, two other transcripts were found to be influenced in sun leaves in the spring/summer. While we detected changes in the levels of only a few transcripts, the observed effects were not identical in both years. In conclusion, elevated ozone exhibited very small influence on the transcription levels of genes of mature beech trees.

Theoretical and experimental study of a mechanical model describing the trunk behaviour of mature beech trees (Fagus sylvatica L.) under the static loading of the crown

The effect of the self-weight increment, caused by annual growth, can be one of the principal processes affecting the development of growth stresses linked to the formation of reaction wood. This paper presents a preliminary study focusing on the relationship between the whole weight of the crown and the trunk displacement it creates. A mechanical beam model is proposed and tested theoretically, as well as experimentally, on three mature beech trees. Once the suitability of the model has been established, a simple sensitivity test in proposed that highlights the principal parameters involved in displacement.

Nutrient concentrations in roots, leaves and wood of seedling and mature sugar maple and American beech at two contrasting sites

Differences in sensitivity to soil conditions across tree species and developmental stage are important to predicting forest response to environmental change. This study was conducted to compare elemental concentrations in leaves, stems, and roots of (1) sugar maple ( Acer saccharum Marsh.) seedlings vs. mature trees and (2) mature sugar maple vs. mature American beech ( Fagus grandifolia Ehrh.) in two sites that differ in soil base saturation and pH. Both sites are located in Huntington Forest, NY, USA; one site (hereafter ‘H’) has higher soil pH and Ca, Mg, and Mn concentrations than the other site (hereafter ‘L’). Sugar maple growth at H (14.8 cm 2 year −1 per tree) was much greater than at L (8.6 cm 2 year −1 per tree), but the growth of beech was not different between the two sites. Leaves, roots, and stem wood of mature beech trees and sugar maple seedlings and mature trees were sampled for nutrient analysis. Foliar Ca, K, and Al concentrations were positively correlated with soil elements, but Mn concentrations were negatively correlated. Sugar maple differed more than beech between sites in foliar K and Mn concentrations. Root Mg and P concentrations reflected soil chemistry differences, in contrast to foliar concentrations of Mg and P, which were indistinguishable between the sites. In sugar maple, seedlings differed more than in mature trees in nutrient concentrations in roots, especially for Mg and Mn. Although beech was not as responsive to nutrient availability as sugar maple in foliar and root nutrient concentrations, Ca and Mg concentrations in beech wood were higher in H (52% higher for Ca and 68% higher for Mg), while sugar maple did not differ between sites. Sugar maple regeneration failure on acidic soils in the same region is consistent with our finding that sugar maple seedlings were very sensitive to nutrient availability. This sensitivity could ultimately contribute to the replacement of sugar maple by American beech in regions of low pH and base cations if base cation leaching by anthropogenic deposition and tree harvesting continues.

Topochemical investigations of cell walls in developing xylem of beech (Fagus sylvatica L.)

Abstract Formation and lignification of xylem cells in mature beech (Fagus sylvatica L.) trees growing in a forest site in Slovenia (46° N, 14°40′ E, 400 m a.s.l.) were studied on the cellular and subcellular level. Samples containing the cambial zone and developing xylem were taken from six beech trees every week throughout the 2006 vegetation period. Cell wall thickening and lignification in individual cell wall layers and cell types were determined by light microscopy, cellular UV-microspectrophotometry and transmission electron microscopy, respectively. Cell division started between the 18th and the 24th of April 2006. Lignification began in the newly formed xylem tissue on the 2nd of May. After 1 month, the developing earlywood portion contained fully differentiated vessels with completed wall deposition and lignification, and differentiated fibres and axial parenchyma became visible after 2 months. At the end of cambial cell division on the 9th August, the differentiation of the most recently formed fibres in the terminal zone of the growth ring continued for approximately 4 weeks. This indicates that the process of lignification in earlywood is slower than in latewood. The high temporal resolution of the investigated processes and the combination of the above-mentioned microscopic techniques provides a detailed insight into the process of cell wall thickening and lignification of woody tissue in beech.

Are Bavarian Forests (southern Germany) at risk from ground-level ozone? Assessment using exposure and flux based ozone indices

Exposure and flux-based indices of O 3 risk were compared, at 19 forest locations across Bavaria in southern Germany from 2002 to 2005; leaf symptoms on mature beech trees found at these locations were also examined for O 3 injury. O 3 flux modelling was performed using continuously recorded O 3 concentrations in combination with meteorological and soil moisture data collected from Level II forest sites. O 3 measurements at nearby rural open-field sites proved appropriate as surrogates in cases where O 3 data were lacking at forest sites (with altitude-dependent average differences of about 10% between O 3 concentrations). Operational thresholds of biomass loss for both O 3 indices were exceeded at the majority of the forest locations, suggesting similar risk under long-term average climate conditions. However, exposure-based indices estimated higher O 3 risk during dry years as compared to the flux-based approach. In comparison, minor O 3-like leaf injury symptoms were detected only at a few of the forest sites investigated. Relationships between flux-based risk thresholds and tree response need to be established for mature forest stands for validation of predicted growth reductions under the prevailing O 3 regimes.

Evaluation of different approaches for modelling individual tree seedling height growth

We compared different approaches for modelling height growth of individual beech seedlings in a controlled factorial experiment as well as in field data from naturally regenerated beech seedlings under the canopy of overstorey mature beech trees. Several competition indices, a model of overstorey fine root density, relative photosynthetically active radiation (PAR) values, and soil water values were used in these approaches. In the factorial experiment relative PAR and soil water content were measured and used for the prediction of seedlings height growth. In the field experiment this was done by using relative PAR and estimated fine root biomass as a surrogate for below ground resource availability. The latter approach was compared with a model where we used various competition indices representing the impact of overstorey trees on beech seedlings. Our results suggested that (1) models which combine resource based growth functions are suitable for the prediction of individual height growth of beech seedlings. Resource based models offer the opportunity to investigate on the independent multiplicative effect of irradiance and water supply and their interactions on tree seedlings. It was (2) shown that a combined model could be used not only to predict individual height growth of beech seedlings in a controlled experiment but also in the field. The model parameters of a pure light response function for the controlled factorial experiment are comparable to those obtained in the field study. The results showed (3) that the precision of predicting beech seedlings height growth is comparable between the model types tested within this study. Approximately half of the observed variation in seedlings relative height growth rate could be explained. However, the simple competition index approach provides no information on the environmental factors constraining tree seedlings growth; whereas the multiplicative combined models can be used to get a better understanding of growth dynamics in the field.

Competition in mixed stands of beech and spruce: effects of climate and ozone

The “Growth-DiVerentiation Balance Theory” assumes a trade-oV between parasite defense and increases in growth and competitiveness (Herms and Mattson 1992). Accordingly, increasing resource availability would induce a decrease in secondary metabolites, and hence defense capacity, relative to primary production. Since 1998, about 20 research teams have examined this theory in the interdisciplinary research center “Sonderforschungsbereich 607” (SFB 607), being conducted in Munich and FreisingWeihenstephan (Germany; Matyssek et al. 2005). In this issue, they present results from studies focusing on the eVects of ozone and drought stress on beech and spruce competing in mixed stands. The mature stand as one research object of the reported studies is “Kranzberger Forst”, a 55-year-old Norway spruce stand near Freising/Germany with groups of 62year-old beech. From the year 2000 on, a group of beech and spruce trees has been exposed to experimentally enhanced free-air ozone fumigation (Karnosky et al. 2001). Ozone was applied, through a novel methodological approach, via more than 100 PTFE tubes into the stand canopy in such a way that Wve spruce and Wve beech trees were exposed to a twice-ambient ozone regime, with ozone levels being restricted to below 150 nl li1 (Nunn et al. 2002; Werner and Fabian 2002; Karnosky et al. 2007). The Wrst paper introduces a novel approach to study the hydraulic architecture of coarse roots. Nikolova et al. (2008b, this issue) combined computer tomography, light microscopy, and sap Xow measurements in order to anatomically and functionally compare the conductive sapwood area of coarse roots between beech and spruce. Cumulative sapwood lumen area was 12% of the total coarse root cross-sectional area in both species. Normalized by that parameter, sap Xow rate increased with root diameter. Haberle et al. (2008, this issue) tested a conceptual approach to assess the amount of carbon available for trade-oVs between defense and growth. They monitored the variation in levels of nine defense-related metabolite groups within and between four consecutive growing seasons in mature beech and spruce trees. The diVerence between minimum and maximum metabolite levels was assumed to be dispensable between growth and defenserelated metabolism, ranging between 2 and 5% of gross primary production. A set of papers describes the eVects of ozone and drought, especially during the extreme summer of 2003. Betz et al. (2008, this issue) investigating the shikimate pathway in the greenhouse and in the Weld, caution against uncritical comparisons between greenhouse-grown saplings and mature forest trees. Rodenkirchen et al. (2008, this issue) studied the eVects of ozone and CO2 on the competitiveness of beech and spruce saplings under standardized phytotron conditions. Ozone stress reduced nutrient eYciencies in beech, suggesting a higher demand for N and P in defense at the expense of competitiveness. Elevated CO2 counteracted the eVects of ozone. In mature ozonefumigated trees, the extreme summer of 2003 had no eVect on the concentrations of P and K in the leaves, whereas the control trees had signiWcantly lower levels of these nutrients in 2004 (Gottlein et al. 2008, this issue). Although ozone fumigation reduced absolute tree diameter increment at breast height in spruce, there was no such eVect in beech S. Rust · A. RoloV (&) Institut fur Forstbotanik und Forstzoologie, TU Dresden, Postfach 1117, 01735 Tharandt, Germany e-mail: roloV@forst.tu-dresden.de

Nutritional effects triggered by the extreme summer 2003 in the free air ozone fumigation experiment at the Kranzberger Forst

Since the year 2000 mature beech and spruce trees were treated in a field experiment with double ambient ozone concentrations. Elevated ozone had no influence on average single leaf biomass and there were also no ozone effects on leaf nutrient concentrations in climatic normal years. However, the extraordinary dry summer 2003 triggered significant differences between the fumigated and control trees. For beech in the year after the drought event the control trees surprisingly had significantly lower foliar levels of K and P than in former years, whereas the ozone exposed trees showed no significant nutritional effects. There are indications, that the trees exposed to double ambient ozone were already adapted to higher ozone values, whereas the control trees experienced extraordinary high ambient ozone concentrations in the dry and sunny summer 2003. For spruce in autumn 2003 and 2004 ozone treated trees had significantly higher foliar levels of K in current year needles than control trees, an effect which cannot be thoroughly interpreted yet on the basis of the dataset available.

Spatial variability of xylem sap flow in mature beech (Fagus sylvatica) and its diurnal dynamics in relation to microclimate

The spatial and diurnal variability of sap flow in a mature beech tree ( Fagus sylvatica L.) was investigated on days with different climatic conditions (sunny, cloudy, rainy), during the summer. Sap flux density (v) was measured with six heat field deformation probes placed around the stem circumference. Each probe measured v at six sapwood depths. Daily v exhibited clear radial variation, and the shape of the radial profile of v differed substantially among circumferential positions. At some positions, daily v decreased monotonically towards the stem centre, whereas at others it showed an almost monotonic increase. Hence, the conducting sapwood area of the beech was highly asymmetrical. At all positions, conducting sapwood reached beyond the deepest sampled sapwood depth, precluding correct estimations of total sap flow. The radial profile of v also differed among measuring days. A general trend was that the inner sapwood contributed relatively more to total sap flow under better weather conditions. Besides variations among days, the shape of the radial profile of v also showed within-day variations. The contribution of the inner sapwood to total sap flow increased in the afternoon, with increasing vapour pressure deficit and photosynthetic active radiation. Because of large circumferential and temporal variability, no general function for the radial profile of v could be developed.

First Report of Phytophthora cactorum Associated With Beech Decline in Italy.

During 2006 and 2007, declining mature beech trees (Fagus sylvatica) were recorded in two stands in the Natural Park of Monti Cimini in central Italy. Symptoms included crown thinning and the presence of bleeding lesions on the main roots and lower stem. Incidence of decline was approximately 5%. Samples of necrotic bark tissue were collected, cut into 5 mm long segments, plated on PARPNH, and incubated at 20°C (1). Phytophthora isolates were obtained from necrotic tissues of 25% of the sampled declining trees. Colonies were rosaceous on potato dextrose agar (PDA) and homothallic. Papillate, ovoid-to-obpyriform, caducous sporangia (mean 38 × 26.2 μm) were produced in soil extract. Oospores were plerotic (mean diameter of 22 to 32 μm) and antheridia paragynous. Optimum growth temperature was 23 to 25°C, minimum 6 to 8°C and maximum 30 to 33°C. A portion of the internal transcribed spacer sequence has been deposited in the NCBI database (GenBank Accession No. FJ183724). A BLAST search of the NCBI database revealed Phytophthora cactorum, Accession No. EU194384, as the closest match with 100% sequence similarity. Pathogenicity of two isolates, PFE3 and IFB-CAC 38, collected from distressed beech trees was tested using a soil infestation test (10 beech seedlings per isolate and control) and an under the bark inoculation method (10 twigs per isolate and controls, wounded and noninoculated taken from a declining beech tree) (2). After 2 weeks at 20°C, twigs and seedlings inoculated with each isolate developed extensive necrotic lesions around the inoculation sites and the collar, respectively, and P. cactorum could be reisolated from all lesions. Controls showed no symptoms. P. cactorum is widespread in declining beech forests in central Europe (1). In Italy, P. cactorum occurs in soils of chestnut and oak forests and was isolated from collar and root lesions of declining walnut trees (3). To our knowledge, this is the first report of P. cactorum being associated with declining beech trees in Italy.

Tree-ring variation, wood formation and phenology of beech (Fagus sylvatica) from a representative site in Slovenia, SE Central Europe

Long-term variation in tree-ring widths (1873–2006) and intra-annual dynamics of cambial activity and tree-ring formation in 2006 were studied in mature beech (Fagus sylvatica L.) trees at a typical forest site near Ljubljana (46°N, 14°40′E, 400 m a.s.l.) and related to leaf phenology and climate data. Tree-ring widths were negatively affected by minimum March and maximum August temperatures and favoured by May and July precipitation. Precipitation of the previous August and temperature of the previous November also had a positive effect. Leaf unfolding was affected by March and April temperatures, occurring later if they were low. Leaf yellowing was positively affected by minimum July temperatures and negatively by September precipitation. In 2006, leaf unfolding occurred on 16 April and was immediately followed by reactivation of cambium at breast height of the trees. One week later, the cambium obtained its maximum width (around 11 cell layers) and the rate of division increased until the end of May/beginning of June. By the end of June, 75% of the tree-ring was formed. Cambial cell divisions stopped from the end of July to mid-August. The average time of cambial activity was 100 days. Leaf yellowing occurred at the end of October, i.e. nearly 2 months after the cessation of cambial cell division. We discuss the usefulness of a combination of long-term (tree-ring width and phenology) and short-term (wood formation at a cellular level) data to understand better the environmental signals registered by a tree during growth.