Assessing Taphrorychus bicolor (Coleoptera: Curculionidae) as a forest pest in central Europe: ecology, monitoring, and management strategies

European beech (Fagus sylvatica L.) trees are becoming vulnerable to drought, with a warming climate. Existing studies disagree on how radial growth varies in European beech in response to droughts. We aimed to find the impact of multiple droughts on beech trees’ annual radial growth at their ecological drought limit created by soil water availability in the forest. Besides, we quantified the influence of competition and canopy openness on the mean basal area growth of beech trees. We carried out this study in five near-natural temperate forests in three localities of Germany and Switzerland. We quantified available soil water storage capacity (AWC) in plots laid in the transition zone from oak to beech dominated forests. The plots were classified as ‘dry’ (AWC < 60 mL) and ‘less-dry’ (AWC > 60 mL). We performed dendroecological analyses starting from 1951 in continuous and discontinuous series to study the influence of climatic drought (i.e., precipitation-potential evapotranspiration) on the radial growth of beech trees in dry and less-dry plots. We used observed values for this analysis and did not use interpolated values from interpolated historical records in this study. We selected six drought events to study the resistance, recovery, and resilience of beech trees to drought at a discontinuous level. The radial growth was significantly higher in less-dry plots than dry plots. The increase in drought had reduced tree growth. Frequent climatic drought events resulted in more significant correlations, hence, increased the dependency of tree growth on AWC. We showed that the recovery and resilience to climatic drought were higher in trees in less-dry plots than dry plots, but it was the opposite for resistance. The resistance, recovery, and resilience of the trees were heterogeneous between the events of drought. Mean growth of beech trees (basal area increment) were negatively impacted by neighborhood competition and positively influenced by canopy openness. We emphasized that beech trees growing on soil with low AWC are at higher risk of growth decline. We concluded that changes in soil water conditions even at the microsite level could influence beech trees’ growth in their drought limit under the changing climate. Along with drought, neighborhood competition and lack of light can also reduce beech trees’ growth. This study will enrich the state of knowledge about the ongoing debate on the vulnerability of beech trees to drought in Europe.

Recent extreme drought events in Central Europe have caused widespread forest dieback with detrimental effects on forest functioning and carbon and water balance. This impact has been notable on European beech (Fagus sylvatica L.), particularly at the core of its distribution, causing concern among forest stakeholders and questions about the resilience capacity of beech trees. The objective of this study is to investigate the physiological processes linked to water and carbon constraints involved in the resilience of beech cambial growth to drought. We selected 56 beech trees distributed in four plots in north‐eastern France with different soil water deficits characterized retrospectively by a water balance model. Functional traits including tree ring width, wood anatomical traits and stable isotopes (e.g. δ13C and δ18O) were measured to retrospectively assess the effect of recent recurrent drought in 2015, 2018–2020, and 2022. Decreased tree growth and increased δ18O and intrinsic water use efficiency (iWUE) were observed due to soil water shortage, whereas xylem vessel size and theoretical specific xylem hydraulic conductivity (Kth) did not show obvious changes. Vessel density was negatively correlated with annual ring width index and was highly sensitive to drought. δ13C, δ18O and iWUE were not significantly related to tree ring width index. The plot that experienced the most severe drought intensity in 2018–2020 showed a significant decrease in tree growth resistance and resilience compared to its resistance and resilience during the 2015 drought event. Surprisingly, growth resilience was not associated with tree anatomical and isotopic traits. Synthesis. Our results demonstrate that beech xylem structure responds to drought by adjusting the radial growth of tree rings with a relatively stable vessel diameter. Our study also highlights the impact of consecutive or recurrent drought in reducing beech tree resistance and resilience, particularly at sites with higher drought intensity. Tree resilience does not seem to involve changes in traits that would promote the hydraulic functioning to better cope with future soil water shortages.

Extreme drought events are responsible for widespread forest dieback and large-scale tree mortality events across the globe, which can have detrimental effects on both short-term forest functioning and long-term ecosystem dynamics. An unprecedented decline of European beech (Fagus sylvatica L.) has been observed in central Europe following the 2018-2020 drought event, and beech trees may have reached a tipping point where many individuals are no longer able to survive. A better understanding of the physiological mechanisms that allow beech trees to resist and to cope with severe water deficits and those that lead to the tree death is essential.The main objective of this study is to gain insight into the physiological properties involved in the resilience or death trajectories of the beech trees in response to an extreme and prolonged drought episode. We retrospectively analysed multi-proxy traits including tree ring width, a proxy for tree cambial growth, wood anatomical traits, a proxy for the xylem hydraulic performance, and tree ring isotopic composition, a proxy for water use efficiency (WUE).A total of 60 trees were selected which are distributed in four stands in North-eastern France with different levels of soil water deficit which were quantified retrospectively by the BILJOU© water balance model. Tree cores at 1.3m were taken for radial growth analysis and retrospective xylem anatomical measurements in the last 10 tree rings (rings before, during and after drought). Stable carbon (δ13C) and oxygen (δ18O) isotopes were also measured in these rings to determine, respectively, the annual WUE and the water and carbon constrains on WUE variation. Tree resistance, recovery and resilience to drought were quantified for cambial growth, specific hydraulic conductivity and WUE.Over the past 10 years, we determined that 2015 and 2018-2020 were drought years by calculating annual soil water deficits at the stand level. Decreased tree growth and increased WUE were observed due to soil water shortage, whereas xylem vessel size and specific hydraulic conductivity did not show obvious changes. Vessel density was negatively correlated with annual ring width and was highly sensitive to drought. In severe drought sites, recurrent drought severely affected resistance of tree growth and the post-drought recovery of hydraulic conductivity and water use efficiency. Furthermore, growth resilience of beech trees could not be explained by vessel-related anatomical traits and isotopic composition. Overall, our study shows that beech xylem structure responds to drought by adjusting the number, rather than the size, of vessels, and highlights the impact of prolonged or recurrent drought on xylem hydraulic and WUE recovery. This work contributes to the understanding of how drought-sensitive trees cope with extreme drought events in terms of their carbon-water relations in the context of climate change.

We examined the occurrence of carabid beetles (Coleoptera, Carabidae) at the edges of oak (Quercus pyrenaica) and beech (Fagus sylvatica) forests in Leon, NW Spain. Pitfall traps were used to collect beetles from April to October 2002, and leaf litter cover and depth were measured. Traps were placed at three distances (0, 50 and 100 m) from the edges of eight forest patches. A total of 5436 carabids belonging to 43 species were collected. We found no statistically significant edge effect at the carabid assemblage level, i.e. the number of species and individuals was not higher at the edge compared to the forest interior. However, individual species were affected by distance from the edge. Five of the 14 species analysed responded predictably to the edge, three of them statistically significantly so. Four species did not respond in the predicted direction, two of them statistically significantly so. We found a considerable difference between forest types in terms of carabid assemblage composition and response to the edge. Oak forests were species richer and beech forests had a higher number of individuals. These differences were probably due to small- scale habitat heterogeneity in the oak forest patches, caused by man, and the homogeneous structure of beech forests. Leaf litter appeared to be one possible factor influencing the distribution of some species from the interior to the edge of forests.

During the vegetation periods 1994 and 1995, net uptake of nitrate and ammonium by roots of adult spruce (Picea abies (L.) Karst) and beech (Fagus sylvatica L.) trees was studied at a field site exposed to high loads of N ('Höglwald', Germany). In addition, uptake experiments were carried out under controlled conditions with young spruce and beech trees grown at normal N supply. In the field, nitrate was not taken up by the roots of spruce trees in appreciable amounts. This was also true for beech except during September 1995. Apparently, beech trees was capable of taking up nitrate, but the environmental condition prevailing at the field site usually prevented net uptake. Net uptake of ammonium in both tree species showed a seasonal course, with maximum rates in mid summer. Rates of ammonium uptake by both species correlated with soil temperature at the field site. Laboratory experiments on the influence of root temperature on uptake of nitrate indicated that uptake rates at temperatures found in the field were low compared with the uptake capacity at optimum temperature. At temperatures of 10 and 15°C, frequently found in the soil at the field site, net uptake of nitrate by spruce and beech amounted to c. 16% and 11%, respectively, of maximum uptake at 25°C. By contrast, net uptake of ammonium at 10°C reached 73% and 31% of the maximum uptake for spruce and beech trees, respectively. Independent of temperature, rates of nitrate uptake were considerably lower than those of ammonium. In young spruce and beech trees, net uptake of nitrate was significantly inhibited by ammonium at nitrate∶ammonium ratios found in the soil solution at the forest site. Preincubation of roots of both species, with amino acids present in the phloem of adult trees at the field site, led to an increase in the amino acid pool in the roots. For spruce trees a correlation between inhibition of uptake of nitrate and enrichment of the roots with the amino compounds Glu, γ-amino butyric acid (Gaba), Gln, and Asn was observed. In beech trees, enrichment of Asp and Gln in the roots correlated with a decrease in net uptake of nitrate. The results of laboratory experiments on the effects of temperature, the nitrate to ammonium ratio in the nutrient solution, and amino acid enrichment in the roots are discussed with special emphasis on the patterns of net uptake of ammonium and nitrate observed in the field.

Tsiripidis, I. & Athanasiadis, N.: Contribution to the knowledge of the vascular flora of NE Greece: Floristic composition of the beech (Fagus sylvatica L.) forests in the Greek Rodopi. — Willdenowia 33: 273–297. — ISSN 0511-9618; © 2003 BGBM Berlin-Dahlem.The first Floristic inventory of the beech forests in the Greek Rodopi is presented. The investigation included pure beech (Fagus sylvatica L. s.l.) stands as well as mixed stands of beech with Pinus sylvestris, P. nigra, Picea abies, Abies ×borisii-regis, Quercus petraea subsp. medwediewii and Q. frainetto. The floristic catalogue is based on the floristic data of 584 phytosociological beech forests relevés and on a supplementary floristic inventory. Published information of records from inside beech forests has also been taken into account. For each taxon information is given about its spatial and altitudinal distribution and constancy in the Greek Rodopi as well as about its ecological preferences. The floristic catalogue is divided in two parts. The first part includes the taxa that constitute the beech forest community. The second part includes taxa that appear randomly in the beech forests. Three species, Hieracium praecurrens, Pyrola media and Verbascum lanatum, are recorded for the first time from Greece.

In mountainous or hilly areas, the slope aspect affects the amount of solar radiation, with direct consequences on species distribution and tree growth. However, little is known on how the tree shape and volume allometry may be affected by contrasting environmental conditions driven by the slope aspect. This study aims to investigate whether the slope aspect affects the aboveground tree shape and volume allometry of European beech (Fagus sylvatica L.) trees. We used the data of scanned trees from two plots located on south- and respectively north-facing slopes and, additionally, an inventory dataset containing measurements of diameter at breast height (D) and tree height (H). To investigate the differences in tree shape, we used analysis of covariance. However, to assess the differences in volume allometry, we first predicted the volume of each individual tree within the inventory dataset using either the south- or the north-facing slope volume model, and then performed a paired t-test on the plot estimates based on the two volume models. Since the uncertainty originating from allometric volume model predictions was likely to affect the results of the paired t-test, we performed a Monte-Carlo simulation to assess the rate of null hypothesis acceptance with the paired t-test. The results showed that trees growing on the north-facing slope were significantly thinner (p < 0.001), with a significantly longer branching system (p < 0.001) compared to those on the south-facing slope. Correspondingly, the volume estimates per unit of forest area based on the south- vs. north-facing slope allometric volume models were significantly different (p < 0.001). The estimates of total aboveground volume per unit of forest area based on the north-facing slope allometric models were significantly larger compared to those based on the south-facing slope volume models, a difference driven by the significantly larger branch and stem volume for the north-facing slope. These differences in estimates per unit of forest area were larger when based on allometric models that only used D as a predictor of aboveground tree volume. The rates of null hypothesis acceptance within the paired t-test were generally low. For total aboveground volume estimated by D and H, the acceptance rate was 1.79%. Nevertheless, only using D to predict tree volume, the rates of null hypothesis acceptance were lower (i.e., 0.1%), suggesting that addition of H as a predictor of tree volume partly explains the differences caused by the slope aspect on volume allometry, but not enough to offset the differences entirely. In conclusion, slope aspect has significantly affected the tree shape and volume allometry of European beech trees.

It is a common belief that feral honey bee colonies (Apis mellifera L.) were eradicated in Europe through the loss of habitats, domestication by man and spread of pathogens and parasites. Interestingly, no scientific data are available, neither about the past nor the present status of naturally nesting honeybee colonies. We expected near-natural beech (Fagus sylvatica L.) forests to provide enough suitable nest sites to be a home for feral honey bee colonies in Europe. Here, we made a first assessment of their occurrence and density in two German woodland areas based on two methods, the tracing of nest sites based on forager flight routes (beelining technique), and the direct inspection of potential cavity trees. Further, we established experimental swarms at forest edges and decoded dances for nest sites performed by scout bees in order to study how far swarms from beekeeper-managed hives would potentially move into a forest. We found that feral honey bee colonies regularly inhabit tree cavities in near-natural beech forests at densities of at least 0.11–0.14 colonies/km2. Colonies were not confined to the forest edges; they were also living deep inside the forests. We estimated a median distance of 2,600 m from the bee trees to the next apiaries, while scout bees in experimental swarms communicated nest sites in close distances (median: 470 m). We extrapolate that there are several thousand feral honey bee colonies in German woodlands. These have to be taken in account when assessing the role of forest areas in providing pollination services to the surrounding land, and their occurrence has implications for the species’ perception among researchers, beekeepers and conservationists. This study provides a starting point for investigating the life-histories and the ecological interactions of honey bees in temperate European forest environments.

Many fungi live intimately associated with plants and may benefit or harm the host plant. Improved knowledge of such interactions is needed for increasing plant health and crop productivity by implementation of fungal inoculants. Co-inoculations of different beneficial fungi offer the possibility to understand complex plant–microbe interactions that may be functionally complementary for improved plant production and protection. Here, we studied the individual and combined effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae with three isolates of entomopathogenic fungi (EPF), representing Metarhizium brunneum, M. robertsii and Beauveria bassiana, on protection against the foliar phytopathogen Botrytis cinerea and on plant growth. Seedlings of tomato (Solanum lycopersicum L. var. Moneymaker) were inoculated in the substrate with AMF or EPF alone and in dual combinations under greenhouse conditions. Inoculation with the different EPF isolates reduced lesion sizes of B. cinerea on inoculated tomato leaves, but only in the experimental repetition that showed highest level of disease severity. The AMF F. mosseae had no additional effect on B. cinerea lesion size in combinations with EPF. In the experimental repetition with least disease severity, the AMF treatment led to limited increase of B. cinerea lesion sizes. In general, F. mosseae caused an increase in plant biomass, and the co-inoculations of AMF and EPF did in some combinations increase plant growth. Below-ground interactions between AMF and EPF were observed, as the presence of AMF in the roots was associated with a decrease of EPF root colonization densities. However, AMF colonization rates were unaffected by EPF presence. The study indicated a functional complementarity between EPF and AMF by suppressing phytopathogens and increasing plant growth, respectively. However, it further revealed the challenge of obtaining consistent results of plant–microbe-phytopathogen interactions, which must be overcome for future implementation of beneficial fungi as inoculants in plant production.

In den Jahren 1998-2001 wurden im südwestlichen\n Harzvorland in windgeworfenen Buchen-Wäldern auf\n Zechstein und auf Unterem Buntsandstein\n vegetationsökologische und gehölzkundliche Erhebungen\n auf Dauerflächen durchgeführt, um die\n Sukzessionsdynamik und Regeneration dieser\n Waldökosysteme nach dem lokalen Orkan von 1997 in\n Abhängigkeit von Standort, ehemaliger\n Nutzungsgeschichte, aktueller forstlicher\n (Nicht-)Behandlung und Störungsflächengröße zu\n studieren. Die untersuchten Bestände lassen sich grob\n in basenreich-flachgründige (Gips/Dolomit, Rendzina,\n Carici-Fagetum),\n basenreich-tiefgründige (Dolomit, Rendzina-Braunerde,\n Hordelymo-Fagetum) und\n basenärmere Standorte (Buntsandstein, lössüberdeckte\n Braun- oder Parabraunerde, Galio\n odorati-, Luzulo-Fagetum) einteilen.\n Gemeinsamkeiten zwischen den Varianten ergaben sich\n hinsichtlich der über die ersten vier Jahre\n kontinuierlich, aber auf unterschiedlichem Niveau\n ansteigenden Artenzahlen. Dabei waren basenreiche\n Standorte artenreicher als basenarme, geräumte\n artenreicher als belassene sowie flachgründige\n artenreicher als tiefgründige. Auf den produktiveren\n Dolomit- bzw. Buntsandstein-Standorten kam zu einer\n sehr starken Strauchschichtexpansion (Gehölze über 50\n cm Wuchshöhe), auf den flachgründigen\n Gipskarst-Standorten dagegen vorerst nicht.\n Bei Unterteilung des Arteninventars in\n ökologisch-funktionale Artengruppen zeigte sich bei\n qualitativer Betrachtung überall eine große Konstanz\n der entsprechenden Spektren im Untersuchungszeitraum,\n bezüglich der Dominanzverhältnisse kam es jedoch\n standortsabhängig zu teilweise massiven Verschiebungen\n zugunsten von Pioniervegetation. Die\n basenreich-flachgründigen Standorte waren durch meist\n krautige Schlagflur- und Ruderalarten und eine\n mittelstarke Naturverjüngung (Esche, Berg- und\n Spitz-Ahorn, Buche) dominiert, die\n basenreich-tiefgründigen Standorte durch hohe Anteile\n der alten Waldbodenflora sowie eine sehr starke\n Naturverjüngung (Esche, Buche) und die basenärmeren\n Standorte durch ausgedehnte Pionierstrauchfluren\n (Himbeere, Holunder, Brombeere) bei relativ schwacher\n Naturverjüngung (v.a. Buche). Pionierbaumarten kamen\n kaum vor. Insgesamt ließ sich ein Überdauern\n Laubwald-typischer Arten beobachten (im Zechstein\n ausgeprägter als im Buntsandstein), was sich in den\n konstanten oder zunehmenden absoluten Deckungssummen\n entsprechender Artengruppen zeigte. Offenbar werden\n sich relativ günstige Standorte mit guter Wasser-,\n Basen- und Nährstoffversorgung und tiefgründigen Böden\n (hier: Hordelymo-Fagetum)\n sehr schnell in Richtung Klimaxgesellschaft entwickeln,\n während Standorte mit geringerer Basenversorgung (hier:\n Galio odorati-,\n Luzulo-Fagetum) dafür etwas länger brauchen\n werden. Die flachgründigen Gipskarst-Standorte (hier:\n Carici-Fagetum) nehmen\n diesbezüglich vermutlich eine Mittelstellung ein.\n Während auf tiefgründigen Dolomit-Standorten die\n Waldregeneration weitestgehend unabhängig von der\n Störungsflächengröße verläuft, wurde auf Buntsandstein\n mit zunehmender Störungsflächengröße (d.h. abnehmender\n Überschirmung) Pioniervegetation immer dominanter,\n sanken die Sämlingszahlen der Laubbaumarten\n beträchtlich und verlor die Buche Anteile an der\n Naturverjüngung, ohne jedoch ihre Dominanz einzubüßen.\n In kleineren Windwurflücken auf Buntsandstein scheint\n die Waldregeneration hin zur standortstypischen\n Buchen-Waldgesellschaft unmittelbar gewährleistet, im\n Flächenwurf wird sie konkurrenzbedingt verzögert.\n Unterschiede zwischen geräumten und belassenen Flächen\n ließen sich durch unterschiedlich starke Präferenzen\n einzelner Arten in einer der beiden Nutzungsvarianten\n feststellen. Im Buntsandstein gehören hierzu generell\n Stör- und Verlichtungszeiger (sowohl im belassenen als\n auch im geräumten Windwurf), im Zechstein betraf dies\n auf belassenen Flächen v.a. Laubwaldarten, auf\n geräumten eine Mischung aus verschiedenen\n Gruppen.\n Obwohl sich das Arteninventar aufgeklappter\n Wurzelteller und das ihrer Umgebungsfläche in allen\n Fällen erstaunlich ähnlich war, fungierten die\n Wurzelteller besonders auf den produktiveren und\n Strauchschicht-reichen Dolomit- bzw.\n Buntsandstein-Standorten als bevorzugter\n Ausbreitungsort für Pioniersträucher, aber auch für\n licht- und und stickstoffzeigende Hemikryptophyten\n sowie für Arten ohne vegetatives Ausbreitungsvermögen.\n Typische Laubwaldarten, Geophyten und Baumjungwuchs\n waren dort nur relativ schwach verbreitet. Dagegen\n verlief auf den flachgründigen, Strauchschicht-armen\n Gips/Dolomit-Standorten die Vegetationsentwicklung auf\n Wurzeltellern und ihrer Umgebungsfläche auch\n quantitativ recht ähnlich und äusserst dynamisch.\n Standortsunabhängig veränderten sich die anfangs\n überwiegend vegetationsarmen Wurzelteller floristisch\n stärker als ihre Umgebungsfläche. Die daraus\n resultierende Angleichung erfolgt auf flachgründigen\n Standorten schneller als auf tiefgründig-produktiven.\n Ebenfalls standortsunabhängig war jeweils ein Drittel\n des Gesamtarteninventars der Untersuchungsflächen nicht\n auf Wurzeltellern zu finden.\n Die im Harzvorland beobachteten\n Windwurf-Sukzessionsmuster können als zwischenzeitliche\n und unterschiedlich stark ausgeprägte Überlagerung der\n alten Waldbodenflora, weniger als zeitliche Abfolge\n floristisch streng unterscheidbarer Artenkombinationen\n aufgefasst werden. Dieser Prozess ist hauptsächlich vom\n Standort, mit zunehmender standörtlicher Ungunst auch\n von der Störungsflächengröße abhängig und schließt eine\n teilweise massive Verschiebung in den\n Dominanzverhältnissen der Arten mit ein. Von einer\n generellen Ablösung des standortstypischen\n Buchen-Waldes ist aber weder im Harzvorland noch in\n vergleichbaren Windwurfgebieten auszugehen.

During the growing session of 1995, the total soluble non‐protein nitrogen (TSNN) composition and contents of mycorrhizal fine roots, xylem sap and phloem exudates of roots from a coniferous (Picea abies L.(Karst)) and a deciduous (Fagus sylvatica L.) tree species were analysed at a field site (‘Höglwald’, Germany) exposed to high loads of N. In April, TSNN in fine roots of spruce and beech trees amounted to 16 μmol N g−1 f. wt and 23·3 μmol N g−1 f. wt, respectively. It decreased to 9·2 μmol N g−1 f. wt and 18·1 μmol N g−1 f. wt, respectively, after bud break in June. The seasonal maximum of TSNN in fine roots of spruce was observed in July (32·7 μmol N g−1 f. wt) followed by a decline of c. 30% until the end of the growing season in September. TSNN in fine roots of beech trees showed a further decline between June and July, when its seasonal minimum was determined (15·6 μmol N g−1 f. wt), and increased to c. 29 μmol N g−1 f. wt until September. In spruce roots Gln and Arg were the most abundant TSNN compounds during the entire growing season. In roots of beech Asn played an important role alongside Gln and Arg, especially in April, when it was the most abundant TSNN compound. Other proteinogenic and non‐proteinogenic N compounds comprised c. 20–30% of TSNN. Nitrate made up <1%, and ammonium <7% of TSNN in the fine roots of both species.In April, TSNN in the xylem sap of roots of spruce and beech trees amounted to 3·4 and 8·6 μmol N ml−1, respectively. In roots of spruce trees xylem sap TSNN increased after bud break up to 12·7 μmol N ml−1 in July. At the end of the growing season TSNN had declined again to 3·9 μmol N ml−1. TSNN in the root xylem sap of beech trees decreased after bud break until July (2·4 μmol N ml−1 in July) followed by a slight increase until September (2·9 μmol N ml−1). Arg, Gln and Asp were the most abundant TSNN compounds in the xylem sap of spruce trees contributing together c. 90% to TSNN. The same TSNN compounds prevailed in the root xylem sap of beech trees in April and July, whereas in June and September Asp was replaced by Asn comprising 57% of TSNN in June. In addition to the N compounds mentioned above, a number of other proteinogenic and non‐proteinogenic amino compounds were found in root xylem sap of both species. In either species, nitrate and ammonium were present in small amounts, contributing <1% and <4% to TSNN, respectively. Apparently, inorganic N taken up by the mycorrhizal roots is mainly assimilated in root tissues or by the mycorrhiza and N uptake by the roots is largely adapted to the assimilatory capacity of this organ.In phloem exudates of spruce roots, TSNN amounted to 10·7 μmol N g−1 f. wt in April, increased in June to 23·4 μmol N g−1 f. wt and decreased again until September to a seasonal minimum of 4·8 μmol N g−1 f. wt. In contrast to spruce, TSNN content in phloem exudates of beech roots showed a seasonal maximum (c. 20 μmol N g−1 f. wt) in April with a subsequent decrease in June after bud break (c. 2 μmol N g−1 f. wt). A fourfold increase in July was followed by a decrease in September, when TSNN in phloem exudates of beech roots amounted to 4·3 μmol N g−1 f. wt. Arg was the most abundant N compound in the phloem of roots from spruce trees and made up c. 60–85% of TSNN during the entire growing season. In beech trees the seasonal course of TSNN correlated with the relative abundance of Arg. Arg comprised 69 and 57% of TSNN in April and July, respectively, but contributed <20% in June and September. Besides Arg, other proteinogenic and non‐proteinogenic amino compounds could be detected in the phloem of both species. In addition, nitrate and ammonium were present in considerable amounts.From these results and a previous report on TSNN in above‐ground parts of spruce and beech at the same site, a whole‐plant model for the cycling of TSNN in both species is proposed. Differences in the location of storage pools are assumed to be responsible for the differences in the seasonal course of TSNN composition and contents observed between the two tree species.

Long-term changes in vegetation and site conditions in beech and spruce forests of lower mountain ranges of Central Europe

As currently framed, the forest cycle model that underlies close-to-nature management in temperate beech forests throughout the globe specifies an orderly sequence of temporal development within even-aged patches comprising the forest mosaic. Although this model has been widely applied to European beech (Fagus sylvatica L.) forests, the underlying assumptions of disturbance-induced even-agedness (i.e., within-patch age homogeneity) and competition-induced size differentiation (i.e., within-patch size heterogeneity) have not been tested in natural beech forests due to prohibitions on tree coring in primeval forest reserves. In a rare and unprecedented test dataset of spatially explicit tree ages in an old-growth European beech forest, we employed triangulated irregular networks of Delaunay triangles to objectively identify natural tree neighborhoods to determine if neighboring (i.e., within-patch) trees were even- or, at most, two-aged. Age differences among neighboring trees (summarized in 25-yr age classes) were rarely <25 yrs and mostly >50 yrs, while the few "even-aged" patches were very small (100 m2) and relatively young (<150 yrs). In this first assessment of the assumptions underlying the forest cycle model in European beech, we observed neither the even-aged cohorts expected for disturbance-induced patches in different phases of development, nor the size differentiation among similarly aged trees that should arise from the neighborhood dynamics of competition, self-thinning, and growth. The lack of patches indicating demographic turnover is fundamentally inconsistent with the forest cycle model as it is currently framed. We call for further exploration of spatially-explicit tree age datasets to determine the generality of these observations.

Forest ecosystems significantly contribute to the global organic carbon (OC) pool, exhibiting high spatial heterogeneity in this respect. Some of the components of the OC pool in a forest (woody aboveground biomass (wAGB), coarse root biomass (CRB)) can be relatively easily estimated using readily available data from land observation and forest inventories, while some of the components of the OC pool are very difficult to determine (fine root biomass (FRB) and soil organic matter (SOM) stock). The main objectives of our study were to: (1) estimate the SOM stock; (2) estimate FRB; and (3) assess the relationship between both biotic (wAGB, forest age, foliage, stand density) and abiotic factors (climatic conditions, relief, soil properties) and SOM stocks and FRB in temperate forests in the Western Carpathians consisting of European beech, Norway spruce, and silver fir (32 forest inventory plots in total). We uncovered the highest wAGB in beech forests and highest SOM stocks under beech forest. FRB was the highest under fir forest. We noted a considerable impact of stand density on SOM stocks, particularly in beech and spruce forests. FRB content was mostly impacted by stand density only in beech forests without any discernible effects on other forest characteristics. We discovered significant impacts of relief-dependent factors and SOM stocks at all the studied sites. Our biomass and carbon models informed by more detailed environmental data led to reduce the uncertainty in over- and underestimation in Cambisols under beech, spruce, and fir forests for mountain temperate forest carbon pools.

Глобальні зміни клімату вже зараз суттєво змінили умови ведення лісового господарства в Українських Карпатах. Зокрема внаслідок масового всихання ялини багато підприємств змушені переорієнтовувати свої лісівничі заходи на вирощування товарної деревини інших порід. Виявлено два основних напрями кліматогенних змін у лісах регіону: зміна едафотопів лісових ділянок у напрямі покращення їхньої родючості з одночасним зменшенням вологості, зміна конкурентоздатності різних деревних видів, зміна породного складу лісів. Найбільші зміни відбуваються в ялинових лісах, де місце ялини, що всихає, природним шляхом займають ялиця і бук, однак під час створення лісових культур вибір головної породи може бути й іншим. Тому актуальним є виявлення закономірностей цих змін для правильного вибору головних порід за типами лісу і висотними рослинними смугами. Тенденції динаміки лісорослинних умов і породного складу лісів регіону були ідентифіковані за відомчими даними метеостанцій та лісовпорядкування. Встановлено, що кліматогенні зміни лісів Українських Карпат відбуваються у таких напрямах: а) дубово-букові ліси трансформуються в буково-дубові зі зміною гігротопу зі «свіжого» на «сухий»; б) буково-ялицеві ліси – в ялицево-букові зі зміною гігротопу з «вологого» на «свіжий»; в) грабово-букові ліси – в грабово-дубово-букові зі зміною гігротопу з «вологого» на «свіжий»; г) смереково-буково-ялицеві ліси – в смереково-ялицево-букові або ялицево-букові зі зміною гігротопу з «вологого» на «свіжий»; д) буково-ялицево-смерекові ліси – в смереково-ялицево-букові або ялицево-букові зі зміною гігротопу з «сирого» і «вологого» на «свіжий»; е) щільнодернинні луки та полонини інтенсивно заростають смерековими, ялівцевими та душекієвими угрупованнями. Констатується нагальна потреба в лісотипологічному картуванні лісогосподарських підприємств Карпатського регіону під час проведення їх повторного лісовпорядкування.