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The Mirambel woodland on the margins of the Millevaches plateau (Massif Central) is one of the few ancient broad-leaved woodlands in France. Historical sources show that it has occupied the same surface area for the past 250 years, despite being in a region that underwent considerable anthropogenic changes during this period. We explored the Mirambel's Holocene history and ancientness by means of soil charcoal analysis, chosen because of its high accuracy on a local scale. We excavated five pedoanthracological pits in the woodland and its open marginal spaces. The 29 radiocarbon dates ranged from the Atlantic (8700–5500 cal yr. BP) – Subboreal transition to the Subboreal (5500–2800 cal yr. BP) and Subatlantic (2800–0 cal yr. BP, i.e. AD 1950) periods, revealing the existence of fire events corresponding to six contemporaneous cultural periods: Neolithic (ca. 3877–2991 cal yr BC), Neolithic-Chalcolithic transition (ca. 2528–2525 cal yr BC), Protohistory (ca. 147 cal yr BC), Roman period (ca. 326–579 cal AD), Middle Ages (ca. 732–1187 cal AD), and contemporary times (ca. 1781 cal AD to present day). Three Tilia charcoal fragments dating from ca. 3717–2919 cal yr BC indicated the presence of a diversified Mid-Holocene deciduous woodland featuring Tilia and Acer nowadays-absent taxa in this area. Deciduous Quercus and Fagus sylvatica dominated most of the soil profiles, as they do nowadays in the woodlands. Other taxa (Salix, Corylus avellana, Betula) were identified, as well as in the current vegetation. The occurrence of Cytisus-type (Fabaceae) and Calluna vulgaris suggested that there were forest clearing phases at all the points sampled. Widely varying levels of abundances may reflect differences in the duration of these open phases.

The wood species of 18th- and 19th-century Italian historic berlines (gala carriages mainly made of wood) housed in the Palazzo Pitti museum in Florence were investigated using non-destructive techniques based on the use of portable digital microscopes. Overall, thirteen wood taxa were identified. Among those, walnut (Juglans regia) was the most abundant species in berlines commissioned by noblemen of high rank, such as kings, princes and grand dukes, whereas in the other carriages of lower lineage, the walnut was replaced by elm (Ulmus sp.) wood, a species commonly used for carriages. Some species were typically present in specific parts of the structures, such as elm and ash (Fraxinus sp.) in the transoms and struts of the undercarriage, oak (Quercus sp.) in the wheel's spokes, poplar (Populus sp.) in the seats, panels and mouldings of the body and European beech (Fagus sylvatica) in the light frames. Species found only occasionally, including chestnut (Castanea sativa), fir (Abies alba) and spruce (Picea abies), may have been introduced in occasions of restoration or substitution. The results also showed a preference for the use of local species, which is different from carriages in other European countries where exotic species were already used.

Radiocarbon (14C) concentrations of annual tree rings from an European beech tree (Fagus sylvatica) from Woods Hole, MA, USA were analyzed at National Ocean Sciences Accelerator Mass Spectrometry facility (NOSAMS) to construct a 14C bomb curve record from northeastern North America. The 14C concentration rises from a pre-bomb (1895–1955) average of Fraction Modern (F14C) = 0.9764 to a peak of 1.8639 in 1964. After 1964, F14C gradually decreases to 1.0611 in 2014. The annual tree-ring radiocarbon content agrees with the atmospheric radiocarbon content of the Northern Hemisphere and is very similar to the radiocarbon concentration of a red oak (Quercus rubra) tree located in Bear Mountain State Park in New York, USA. Intra-annual tree-ring pairs did not produce evidence of a seasonal effect on the radiocarbon concentration, but there were few samples and more study is warranted.

Knowledge regarding tree species dynamics is essential to understand forest responses to the environment, and to evaluate management options in adapting forest ecosystems to future climates. As maintaining tree species diversity and promoting structural stand heterogeneity are among the strategic elements in adapting forest management to climate change, the monitoring tree diversity is an ongoing challenge. Large-scale forest inventories have been proposed as a suitable basis for forest diversity analysis on large spatial and temporal scales. We used Swiss forest inventory data (NFI) to analyse temporal changes in tree species richness on small plots from 1983 to 2006. For two size groups of trees (‘small’ trees with dbh from 12 to 35 cm from plots with 200 m2 area, and ‘large’ trees with dbh ≥ 36 cm from plots with 500 m2 area), we identified the number and the tree species appearing (‘gains’) or disappearing (‘losses’) from each plot during the study period, and related these changes to site, stand and management characteristics. We found that species richness change was size-dependent and varied largely due to regional differences in the past land-use history of the Swiss forests. ‘Gains’ of ‘small’ trees were higher in stands with diverse vertical structure, with less competitive pressure as well as in warm environments, whereas ‘gains’ of ‘large’ trees were mostly related to climate and were highest in warm and moderately moist habitats. ‘Losses’ in both tree-size groups were mainly promoted by management. Our analysis suggests high vulnerability of Picea abies and high competitiveness of Fagus sylvatica, and underlines the potential of Abies alba in forming future Swiss forests. Despite of the silvicultural paradigm to create more species rich forests, most silvicultural interventions decreased small-scale species richness. This calls for further studies on the effect of management on tree species diversity.

The European beech (Fagus sylvatica L.) is a competitive and shade-tolerant species, with its natural regeneration in closed-canopy stands affected by a number of variables. The study aimed to identify factors related to beech regeneration by focusing on two main questions: (1) can we identify environmental and stand structural characteristics that promote beech regeneration or indicate suitable conditions for regeneration under closed canopy conditions, and (2) do environmental and stand structural characteristics favorable for beech regeneration differ among the ontogeny of seedlings and saplings? To answer these questions, we sampled four beech-dominated forest complexes in northern and southern Poland. Study plots were established in sites with varying overstory composition, including beech-dominated, mixed, and conifer-dominated stands. In the analyzed forest complexes, regeneration consisted mostly of beech seedlings and saplings with admixture of shade tolerant or intermediate light-tolerant species—Norway spruce (Picea abies (L.) Karst.), silver fir (Abies alba Mill.), hornbeam (Carpinus betulus L.), and sycamore maple (Acer pseudoplatanus L.). The average density of beech regeneration was 9047, 10,305, 5198 and 8972 trees ha−1 in forest complexes 1, 2, 3 and 4, respectively; however, the inter-plot variation of the regeneration density was high. Beech regeneration occurrence were determined by stand structural characteristics. Beech regeneration decreases as stand density increases and increases with stand basal area and the percentage of beech in the dominant canopy layer. The ecological prerequisites favorable for beech regeneration abundance differ with the ontogeny of seedlings and saplings—the smallest seedlings regeneration was determined by stand structural variables to a greater extent, while more advanced regeneration abundance was also associated with light-demanding species regeneration abundance. Under closed canopy conditions, beech regeneration abundance was weakly influenced by intra/interspecific competition from surrounding vegetation; however, canopy openings may increase it, therefore, competition aspects should be taken into account in the selection of forest management practices.

Norway spruce (Picea abies), European beech (Fagus sylvatica), silver fir (Abies alba) and Scots pine (Pinus sylvestris) typically co-occur in European forests, but show contrasting response to climate and environmental change. Sustainable forest management therefore depends on species- and regional-specific information. Here, we use tree-ring width measurements of 334 beech, 280 fir, 144 spruce and 63 pine trees from 75 inventory plots in Slovakia to assess the predominant factors that control radial stem growth of Europe’s economically most important forest species. All four species exhibit significant shifts in stem growth over the past 100 years. Ring width patterns were, however, not significantly affected by tree species diversity and site elevation. The resistance, resilience and recovery of all species to the extreme summer droughts between 1950 and 2003 suggest that spruce is the species most unsuitable for the predicted warmer and drier future. Silver fir may benefit from warmer conditions, although we cannot conclude that it will not suffer from predicted increased frequency of climate extremes. Forest management in this locality should aim to avoid significant loss of forest cover by replacing Norway spruce monocultures with mixed stands of silver fir and European beech.

We studied the effect of coarse woody debris (CWD) on the soil nutrient status in two beech (Fagus sylvatica) dominated forest reserves in Flanders, Belgium: Wijnendale Forest, on a sandy soil and Kersselaerspleyn in Sonian Forest, on a loamy soil. More specifically, we looked at the chemical composition of beech logs of different stages of decay. In addition, we examined the chemical composition of the organic and the mineral soil at five distances from the decomposing logs. We considered the concentrations of the following elements: C, N, P, S, Ca, K, Mg, Mn, Fe, and Al. The results indicate a difference in wood and soil chemical composition between the two forest sites. The soil and the aboveground biomass of Wijnendale had the highest total N concentration and the lowest concentrations of P and base elements (Ca, K, Mg, and Mn). There is an increase in element concentrations in CWD of both forests during the decomposition, except for K and C. The higher N concentration in Wijnendale, explained by high atmospheric nitrogen deposition in this forest, persisted during decomposition. By contrast, the concentrations of P, Ca, K, and Mg in dead wood of both forests became similar when decomposition proceeded. The effect of CWD was more pronounced in the organic soil layer than in the mineral soil. The organic soil in the proximity of CWD had a higher pH and higher concentrations of C, N, P, Ca, Mg, and Mn (in Sonian forest) and a lower Al concentration (in Wijnendale forest) and this is highly significant for Ca, a limiting nutrient in moderate to highly acidic forests. The percentage of the soil surface impacted by the logs is 0.92% and 0.36% for Sonian and Wijnendale respectively, which is expected to increase with time, considering the fact that both reserves are only recently left unmanaged. The results of this study highlight the contribution of CWD in sustaining the nutrient status and buffering capacity of forest sites, in particular on soils sensitive to acidification and exposed to high nitrogen deposition.

We studied the fine root system of Fagus sylvatica in six mature stands on different bedrock down to the rock surface (or to 2 m) to investigate whether (1) the stand total of fine root biomass (FRB) increases, while the fine root live:dead ratio decreases, with decreasing soil base richness, (2) specific root area (SRA) and root tip frequency increase with a decrease in base richness, and (3) FRB is related to profile depth. The three beech stands on deep soil (>2 m profile depth) had on average by 38% larger FRB totals than the stands on shallow soil (60–80 cm), suggesting that limited root space is an important determinant of fine root system size in F. sylvatica. Despite large variation among sites, soil chemistry influenced root morphology only little: fine root diameter depended on soil C/N ratio and root tip frequency on base saturation in a few soil horizons. Much larger morphological differences were found between topsoil and subsoil roots within a profile. We conclude that the fine root system of F. sylvatica varies under similar climatic conditions remarkably little between base-poor and base-rich sites, in contrast to the pronounced topsoil-subsoil differences in root morphology and fine root density.

Despite improvements of dendrochronological techniques in many forest ecosystems, studies describing the growth responses of trees following disturbance events including comprehensive data on factors and processes behind tree-growth release are rare, especially for European temperate forests, limiting the interpretation and generalization of dendroecological studies. Here we examine the effect of key factors on the growth reaction of Fagus sylvatica L. to disturbances in 8 old-growth forests in the Czech Republic, independently dated using three different data sources – tree censuses, dendrochronology and historical aerial photographs. Using 117 increment cores, we studied four parameters of radial tree-growth surrounding canopy gaps: magnitude, duration, abruptness and response shift, in relation to factors of different spatial scales, i.e. tree-, gap- and stand-level variables. Our results indicate that the beech growth response to gap formation strongly differs across a complex of factors at diverse spatial levels, frequently occurring in noteworthy interactions. A positive trend for the gap size * radiation interaction in the analysis of magnitude was found, suggesting that the effect of gap area differs among topographical features. As for duration and abruptness, the interaction of distance and mortality mode was identified, indicating a longer and more gradual reaction along with increasing distance of the cored tree from the gap centre, varying by the type of the gap maker’s death. In addition, an altitudinal gradient was found to predict the magnitude of growth changes and the time interval between the disturbance and the reaction of nearby trees. Surprisingly, the diameter of the surviving trees was not a good predictor of radial growth, with a significant positive relationship to just abruptness. An effect of locality was not observed, facilitating the broad applicability of our findings across a wide range of beech-dominated temperate forests. Our results emphasize the general limits of dendrochronological data in disturbance spatial pattern studies, as indicated by the considerable variability in the responses of neighbouring trees to identical disturbance event. A detailed examination of the growth reaction, considering not only the response magnitude but also other important parameters, plays a key role in the precision of detecting growth releases as well as in reducing the sample size required for summary disturbance history evaluations. In focusing on this issue we believe we contribute to future dendroecological research by demonstrating the need for more precise disturbance history evaluations.

To better understand natural regeneration of trees and forest dynamics it is important to gain insight into the drivers of invertebrate herbivory. In mature forests, associational resistance of trees resulting from a high diversity of neighbouring trees is common, and can have cascading effects on tree growth through resource concentration effects or through changes in top-down control. While the underlying biological processes are known to be influenced by the forest’s spatial properties, we lack insights on how resource concentration, top-down control and fragmentation jointly affect sapling performance in fragmented landscapes. We therefore experimentally quantified effects of the proportion of conspecific trees in the overstorey (resource concentration), avian top-down control (natural enemies) and distance to the forest edge on invertebrate herbivory levels and sapling growth. The assessments were made on planted saplings of Fagus sylvatica, Quercus robur and Quercus rubra in 53 experimental plots and birds were excluded by means of exclosures from a subset of these saplings. Excluding avian top-down control increased herbivory on each tree species. Increased herbivory led to decreased sapling growth in F. sylvatica and Q. rubra. On Q. robur saplings, top-down control was stronger closer to the forest edge. Furthermore, in this species, herbivory inside the exclosures increased with an increasing proportion of conspecific trees in the overstorey, while such a resource concentration effect was not observed outside the exclosures. Our results show the importance for forest management of conserving insectivorous birds and promoting a mixed overstorey, which can decrease sapling herbivory when bird abundance is low. More generally, our study provides insight into the complex, multitrophic interactions that drive sapling growth in forest stands located within fragmented landscapes.

Monitoring forest soil carbon dioxide efflux (FCO2) is important as it contributes significantly to terrestrial ecosystem respiration and is hence a major factor in global carbon cycle. FCO2 monitoring is usually conducted by the use of soil chambers to sample various point positions, but this method is difficult to replicate at spatially large research sites. Satellite remote sensing is accustomed to monitoring environmental phenomenon at large spatial scale, however its utilisation in FCO2 monitoring is under-explored. To this end, this study explored the potential of LANDSAT-8 to estimate FCO2 with the specific aims of deriving land surface temperature (LST) from LANDSAT-8 and then develop FCO2 model on the basis of LANDSAT-8 LST to account for seasonal and inter-annual variations of FCO2. The study was conducted over an old European beech forest (Fagus sylvatica) in Czech Republic. In the end, two kinds of linear mixed effect models were built; Model-1 (inter-annual variations of FCO2) and Model-2 (seasonal variations of FCO2). The difference between Model-1 and Model-2 lies in their random factors; while Model-1 has ‘year’ of FCO2 measurement as a random factor, Model-2 has ‘season’ of FCO2 measurement as a random factor. When modelling without random factors, LANDSAT-8 LST as the fixed predictor in both models was able to account for 26% (marginal R2 = 0.26) of FCO2 variability in Model-1 whereas it accounted for 29% in Model-2. However, the parameterisation of random effects improved the performance of both models. Model-1 was the best in that it explained 65% (conditional R2 = 0.65) of variability in FCO2 and produced the least deviation from observed FCO2 (RMSE = 0.38 μmol/m2/s). This study adds to the limited number of previous similar studies with the aim of encouraging satellite remote sensing integration in FCO2 observation.

Fine-scale spatial point-pattern analysis can give insights into the underlying pattern-creating biological processes in an environmental context. However, there are few studies comparing the spatial distribution of trees in managed stands and unmanaged forests that take into account their developmental stage. The main aim of this study was to assess and model the spatial patterns of Abies alba Mill. and Fagus sylvatica L. trees in managed and unmanaged forest patches in the early developmental stage. This study investigated tree communities dominated by A. alba and F. sylvatica in the Świetokrzyskie Mountains in Central Europe. From 2016 to 2018, 60 sample plots representing the growing-up developmental stage were randomly selected: 30 from managed stands and 30 from unmanaged forests. Models of the fine-scale spatial distributions of the trees were distinguished using hierarchical cluster analysis (HCA), analysis of group similarities (ANOSIM), and multiple response permutation procedures (MRPP). Indices based on the K-function and the O-ring statistic, I L r and I O r , respectively, were developed and used as clustering variables. The proposed indices assume values from −1 to 1 for random patterns; values > 1 indicate aggregation, and values Models of the fine-scale spatial distributions of the trees differed only slightly between the managed and unmanaged patches. These models suggest that in the investigated sample plots, the fine-scale spatial patterns (with distances among the trees not exceeding 10 m) were usually random. Only in a few patches were the tree distributions found to be aggregated, from 5 to 10 m and from 7 to 10 m in the managed stands and the unmanaged forests, respectively. The relatively similar models of the fine-scale spatial distributions of the trees in the managed and unmanaged forest patches in the growing-up developmental stage show that early successional forest dynamics follow a parallel trajectory of recovery. The long-term application of the shelterwood system as well as self-regeneration and self-regulation natural processes led to the creation of the similar spatial structures of the trees. This observation may be helpful in the design of planting patterns and/or harvesting schedules.

Late spring frost plays a major role in the structure and function of forest ecosystems with potential consequences on species distribution at both local and regional scales. Paradoxically, in a warmer world the incidence and impact of frost is increasing because of earlier leaf unfolding and flowering as a response to warmer temperatures. In this regard, European Beech (Fagus sylvatica L.), a native tree species widely distributed in European forests, is considered particularly sensitive to changes in spring temperature regimes associated with climate change and thus especially subject to the risk of frost damage. Although several studies concerning F. sylvatica frost damage have been conducted in northern and central Europe, no extensive studies are available for the southern part of its range, i.e. central and southern Italy as well as Greece. In this paper the effect of a late spring frost occurring at the end of April 2016 is extensively documented with high spatial detail all along the Apennine Chain through satellite image data. Three different remote-sensing greenness indexes, namely the normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and the greenness index (GI) derived from Landsat-8 satellite images acquired from May to July in the years 2014, 2015, and 2016 at a spatial resolution of 30 m, were used to gauge the spatial response of common beech forests to this late frost event with relation to latitude, altitude and slope exposure. Frost damage was evaluated as a difference (Δ) of NDVI, GI and EVI between the mean of years 2014 and 2015 (i.e. MRY, mean of reference years), and 2016 (i.e. FEY, frost reference year). The three satellite remote-sensing indexes were efficient at detecting leaf damage with detailed spatial resolution and proved consistent with one another. The greatest damage occurred in the middle altitudinal range between 1500 and 1700 m a.s.l. with a decreasing trend toward both lower and higher elevations due to warmer temperatures below, and delayed phenology above. Exposure also influenced frost injury, with south-facing slopes of the mountain more damaged than the north. This difference was due to earlier spring leaf phenology of southern beech trees in response to a greater heat sum in the warm weeks preceding. Less damage in the northern Apennines is consistent with the spatial extent of minimum freezing temperatures. To sum up, frost damage is strongly related to site-specific conditions, i.e. on the one hand to minimum temperatures, and on the other to the phenological stage of the trees involving both altitude and exposure. Hence focusing on detailed sub-regional studies can be helpful for predicting future consequences of climate change on forests.

Upon the occurrence of acidic deposition-driven damage to forests at the beginning of the 1980s, large-scale liming has been applied to acidic forest sites in Germany. Due to possible negative consequences on soil chemistry and on (soil) fauna and flora, this measure was discussed highly controversially right from the beginning and is disputed until today. In investigations of liming effects on the forest understory vegetation, very few studies covered a time period of more than two decades with intermittent releves. We analyzed releves of the herbal understory on limed and control plots in one pine (Pinus sylvestris), one oak (Quercus robur), two European beech (Fagus sylvatica) and five Norway spruce (Picea abies) stands at permanent observation sites in south-western Germany. These releves had been repeatedly conducted during approximately 25 years. The number of herbal plant species was generally low. An increase in the herb layer's plant cover with time was found at six out of the nine study sites and was mainly due to spreading of two grass species (Milium effusum, Deschampsia flexuosa) and of the subshrub Vaccinium myrtillus, which might have benefitted from continuous nitrogen deposition. Only two species (Agrostis stolonifera, Stellaria media) with a main distribution in open landscapes were found in the years of investigation and their occurrence was restricted to only four sites and some few years. Across all sites, the average Ellenberg indicator values of nutrient (nitrogen) supply (N-values) were significantly increased on the limed plots ten years after liming, and at Year 10, the N-values of the limed plots were significantly higher than that of the control, presumably due to increased decomposition rates after liming. At the spruce sites, the average Ellenberg indicator values of soil reaction (R-values) of the limed plots 10 years after liming were significantly higher than at the beginning (Year 0) and at the end of the investigation (2013). We found no significant differences among the Ellenberg indicator values of light condition (L-values). In conclusion, liming had a significant, but only transient effect on the composition of the understory species. Therefore, our results do not support arguments against liming of acidic forests that are based on long-term changes in the herbal flora. In managed forests for wood production on acidic soils, liming can continue contributing to buffer the soils against ongoing acidification and accompanying cation leaching caused by anthropogenic deposition of nitrogen.

Long-term changes in climate substantially affect the tree growth and species distribution in Europe. In the presented study, the radial growth of Fagus sylvatica (L.) and Picea abies ((L.) Karst.) has been studied along an altitudinal gradient covering six vegetation formations characteristic for sub-montane, montane and high-montane conditions of the western Carpathians. Tree growth responses to temperature and precipitation changes have been analysed based on the sample of increment cores and standard dendroclimatic methods in two time periods, the reference period 1961–1990 and the recent period 1991–2012. The growth responses of spruce and beech to recent changes in climate were similar up to high-montane zones, where the beech shows significantly larger improvements of radial increments in comparison to spruce. The growth responses were mainly temperature driven. In the sub-montane area, the increased effect of precipitation in the recent period was overridden by the negative effects of warming, and the alleviated temperature limitation had an evidently supportive effect on tree growth in montane and high-montane areas. In the near future, the warming will likely cause decline in radial increments of beech and spruce in sub-montane areas due to expected landscape drying. At the same time, the improved competitive ability of beech in the high-montane zones suggests a shift in the leading edge of beech distribution into higher altitudes in East-Central Europe.

Temperate forests with shade-tolerant canopy tree species can develop vertical structures of varying complexity. Forests with Abies alba Mill. and Fagus sylvatica L. can be composed of one-, two-, and multi-storied patches and selection patches. A dominant view in forest ecology is that unmanaged forests tend to have greater structural heterogeneity than managed stands. Structural integrity, however, may differ among forest developmental stages. The main objective of this study was to compare the tree diameter complexity in managed and unmanaged patches during the early developmental stage. Data were collected between 2016 and 2018 in the Świetokrzyskie Mountains in Central Europe. The investigated tree communities were dominated by A. alba and F. sylvatica. Sample plots representing the growing-up developmental stage were randomly selected; of these, 30 plots were in managed stands, and 30 plots were in unmanaged forests. The diameter at breast height (DBH) distribution patterns were determined using hierarchical cluster analysis (HCA), clustering indices, and finite mixture models. Three main DBH distribution patterns were identified for the managed stands (K-A, K-B, and K-C). These patterns consisted of three or two sub-populations. The patterns represented structurally diversified patches composed of trees of all ages with multi-, three- or two-layered canopies and with intensive natural processes of regeneration. Two main DBH distribution patterns were identified for the unmanaged forests (S-A, and S-B). These patterns consisted of two clearly separated sub-populations. They are typical in patches with two-layered canopies, and the trees from the upper layer had a large share (40–60%). The distinguished DBH distribution patterns indicated there was greater tree size diversity in the managed stands than in the unmanaged forests. When comparing managed versus unmanaged patches, it is important to consider the developmental stage.

Litter fall and the associated nutrient return are a significant supply of resources in forest ecosystems. In mixed stands both litter quantity and quality can change under different species compositions. Spatial heterogeneity inherent in mixed stands, defined by stand structure and the present species, will affect the litter composition around a tree of interest. Therefore spatially explicit information will be needed to determine how neighbourhood characteristics in a mixed stand have an effect on litter composition and nutrient return. Using a leaf dispersal model, we determined litter production and leaf shedding parameters of four different tree species. Results from this model indicated that the proportion of litter that originated from the neighbourhood was 86% and 77% at the local tree level for oak and beech respectively. Using this information we found that the presence of accompanying species birch or hornbeam had beneficial effects on local return of N, P, Ca, Mg and Mn. Return of K was optimal with only beech trees in the neighbourhood. These results could give an indication on how to use stand establishment, structure and management to optimize nutrient return.

Tree mortality is caused by complex interactions between multiple biotic and abiotic factors. Processes of tree mortality that are not induced by natural disturbances are often reflected in distinct radial growth patterns of trees, which typically serve as reliable indicators of impending tree mortality. However, it remains unclear whether empirical mortality models that are based on tree size and growth result in more realistic projections of forest succession in dynamic vegetation models (DVMs). We used a combination of tree-ring and inventory data from unmanaged Swiss natural forest reserves to derive species-specific survival models for six Central European tree species (Abies alba, Fagus sylvatica, Larix decidua, Picea abies, Pinus cembra and Quercus spp.). We jointly used 528 tree-ring samples and inventory data from eight forest reserves. We implemented the estimated parameters of the survival models into the DVM ForClim and performed simulations of forest succession that were validated using the inventory data of the forest reserves. Size- and growth-dependent variables (i.e., diameter at breast height and mean ring width) over the last few years prior to tree death were reliable predictors to distinguish between dying and living trees. Very low mean ring widths over several preceding years as well as small and large trees, respectively, reflected low survival probabilities. However, the small sample sizes of small and large trees resulted in considerable uncertainty of the survival probabilities. The implementation of these survival models in ForClim yielded plausible projections in short-term simulations and for some sites improved the predictions compared to the current ForClim version. Stand basal area, however, tended to be overestimated. Long-term simulations of ForClim based on the empirical survival models resulted in realistic predictions only if the uncertainty of the predicted survival probabilities was considered. We conclude that the combination of different data sources in combination with the consideration of intra-specific trait variability yields robust predictions of tree survival probabilities, thus paving the way towards better tree mortality models and more reliable projections of future forest dynamics.

Producción Científica, The response of European beech (Fagus sylvatica L.) to climate warming will depend on the ability of their populations to adjust tree performance to water shortage. By exploring inter- and intra-annual variations in secondary growth and mean vessel area (MVA), we assessed the effects of precipitation on cambial activity and hydraulic control during the vessel expansion phase along tree lifes. We sampled beech populations at low and high altitude from four mountain ranges across its southwestern distribution edge. We measured a total of 45,897 rings from 126 trees and 5.5 million vessels from 76 trees. We built chronologies for ring width and MVA between 1950 and 2017, calculated their climate responses and evaluated the effects of region, altitude and chronology type (ring-width vs. MVA) by means of ordinations (PCA) and constrained ordinations (pRDA). Precipitation controlled ring width and MVA along beech's southwestern distribution range, but at different time domains. Ring width responded primarily to summer precipitation during the previous growing season, whereas MVA responded to water availability during the vessel expansion phase, with timing shifting along the ring, according to the moment of vessel expansion. Regional differences were significant, but low, compared with the effect of chronology type. A large part of the variance explained by region was due to the strong difference between Western Pyrenees forests –growing under hyperhumid conditions– and the rest of forests under drier and warmer climate. Only minor differences between altitudes were found for the climate control of ring width and vessel size at annual scale, and no intra-annual effect on climate control of MVA. The stronger effect of chronology type on climatic response compared to the role of geographical location or altitude suggests common climate constraints on secondary growth and xylem anatomy along beech dry edge., Ministerio de Ciencia, Innovación y Universidades (grants CGL2017-87309-P, PID2020-118444GA-100, PID2019-109906RA-I00 and PRE2018-084106), Ministerio de Economía, Industria y Competitividad (grant IJC2019-040571-I), Junta de Castilla y Leon (grants IR20201-UVA08 and VA171P20), EU LIFE Soria Forest Adapt (grant LIFE19 CCA/ES/001181)

Background Organic carbon stored in forest soils (SOC) represents an important element of the global C cycle. It is thought that the C storage capacity of the stable pool can be enhanced by increasing forest productivity, but empirical evidence in support of this assumption from forests differing in tree species and productivity, while stocking on similar substrate, is scarce. Methods We determined the stocks of SOC and macro-nutrients (nitrogen, phosphorus, calcium, potassium and magnesium) in nine paired European beech/Scots pine stands on similar Pleistocene sandy substrates across a precipitation gradient (560–820 mm∙yr− 1) in northern Germany and explored the influence of tree species, forest history, climate, and soil pH on SOC and nutrient pools. Results While the organic layer stored on average about 80% more C under pine than beech, the pools of SOC and total N in the total profile (organic layer plus mineral soil measured to 60 cm and extrapolated to 100 cm) were greater under pine by about 40% and 20%, respectively. This contrasts with a higher annual production of foliar litter and a much higher fine root biomass in beech stands, indicating that soil C sequestration is unrelated to the production of leaf litter and fine roots in these stands on Pleistocene sandy soils. The pools of available P and basic cations tended to be higher under beech. Neither precipitation nor temperature influenced the SOC pool, whereas tree species was a key driver. An extended data set (which included additional pine stands established more recently on former agricultural soil) revealed that, besides tree species identity, forest continuity is an important factor determining the SOC and nutrient pools of these stands. Conclusion We conclude that tree species identity can exert a considerable influence on the stocks of SOC and macronutrients, which may be unrelated to productivity but closely linked to species-specific forest management histories, thus masking weaker climate and soil chemistry effects on pool sizes.

Background Equatorward, rear-edge tree populations are natural monitors to estimate species vulnerability to climate change. According to biogeographical theory, exposition to drought events increases with increasing aridity towards the equator and the growth of southern tree populations will be more vulnerable to drought than in central populations. However, the ecological and biogeographical margins can mismatch due to the impact of ecological factors (topography, soils) or tree-species acclimation that can blur large-scale geographical imprints in trees responses to drought making northern populations more drought limited. Methods We tested these ideas in six tree species, three angiosperms (Fagus sylvatica, Quercus robur, Quercus petraea) and three gymnosperms (Abies alba, Pinus sylvestris and Pinus uncinata) by comparing rear-edge tree populations subjected to different degrees of aridity. We used dendrochronology to compare the radial-growth patterns of these species in northern, intermediate, and southern tree populations at the continental rear edge. Results and conclusions We found marked variations in growth variability between species with coherent patterns of stronger drought signals in the tree-ring series of the southern populations of F. sylvatica, P. sylvestris, and A. alba. This was also observed in species from cool-wet sites (P. uncinata and Q. robur), despite their limited responsiveness to drought. However, in the case of Q. petraea the intermediate population showed the strongest relationship to drought. For drought-sensitive species as F. sylvatica and P. sylvestris, southern populations presented more variable growth which was enhanced by cool-wet conditions from late spring to summer. We found a trend of enhanced vulnerability to drought in these two species. The response of tree growth to drought has a marked biogeographical component characterized by increased drought sensitivity in southern populations even within the species distribution rear edge. Nevertheless, the relationship between tree growth and drought varied between species suggesting that biogeographical and ecological limits do not always overlap as in the case of Q. petraea. In widespread species showing enhanced vulnerability to drought, as F. sylvatica and P. sylvestris, increased vulnerability to climate warming in their rear edges is forecasted. Therefore, we encourage the monitoring and conservation of such marginal tree populations.

The partitioning of bulk precipitation (PR) in forest ecosystems and its chemical composition depends on both meteorological factors, such as precipitation amount and intensity, evaporation rate, and wind speed, and stand structural factors, such as stand density, canopy structure, bark texture, and spatiotemporal distribution and density of foliage. We analysed fluxes of water and element contained therein of a mature European beech (Fagus sylvatica L.) forest stand on sandy soils in northeastern Germany. We applied a radially symmetrical setup within a stem distance gradient to measure stand precipitation (SP) with its components of throughfall (TF) and stemflow (SF), as well as to measure soil moisture, the chemical composition of the soil solution, the soil chemistry, and the fine root distribution. The chemical analysis of the constituents covered the macroelements (Ca, Mg, K, Na, Al, Fe, Mn, Si, S, P), the cations and anions NH4+, NO3-, Cl-, SO42-, and a few heavy metals (Cu, Pb, Zn). With an average PR of 620 mm a-1, the partitioning resulted in 79% TF, 6% SF, and 15% canopy evaporation. TF volume increased with distance to stem during summer, but decreased during winter. Clear spatial gradients with increasing concentrations from PR, to different classes of TF as the distance from the trunk decreased, to SF were observed for nearly all elements. The contact of precipitation with leaves and the canopy structures alters the chemical composition of TF and SF by transferring elements from dry deposition or leaching of intracellular materials from the canopy and leads to the input of larger amounts of macroelements and heavy metals with the SP into the soil. Spatial patterns of canopy structures thus affect the spatial variation of TF and its constituents, which also affects the spatial distribution of roots and, at least in phases, the chemical composition of the topsoil solution.

Instituto de Ciencias Forestales (ICIFOR), The important role that forests play in the global carbon cycle has led to the implementation of management practices to enhance long-term carbon storage in forests. Obtaining information about how forest biomass varies at different successional stages is therefore essential. In this study, we aimed (i) to determine the relationship between stand live biomass and the degree of naturalness (i.e. the degree to which forests dynamics are driven by natural processes in the absence of anthropogenic influences) in undisturbed, mature forests, and (ii) to establish the upper threshold of live biomass stock that is dependent on site quality, by using the site form (SF) index (dominant height-diameter relationship). We assessed live biomass stocks in a total of 10 undisturbed mixed and pure mature silver fir (Abies alba Mill.) and European beech (Fagus sylvatica L.) stands across the Spanish Pyrenees. We used dendrochronology and chrono-functional indicators to assess the degree of naturalness and to detect growth releases as proxies for past disturbance. We compared data from the mature plots and data from the Spanish National Forest Inventory (NFI), for similar forest types and SF values, to determine whether maximum live biomass values were reached in the plots. We observed that live biomass stock was generally independent of naturalness. The forests characterized by the lowest degrees of naturalness held similar amounts of live tree biomass as those characterized by the highest degrees of naturalness, including old-growth forests. Although some stands had undergone severe disturbance in the past, in all but two plots the live biomass stocks reached maximum values at the respective SF values, unlike in the NFI plots. The study findings contribute to the body of evidence supporting the existence of an upper threshold of live biomass stock represented by undisturbed mature stands. Maximum live carbon stock appears to be reached at earlier stages than the old-growth stage. This finding has consequences for biomass and carbon management and may be useful for developing forest policies involving carbon sequestration aimed at mitigating climate change., This work was supported by the Spanish Ministry of Science, Innovation and Universities (projects AGL2016-76769-C2-2-R, RTI2018-096884-B-C31 (JJC), and RTI2018-096884-B-C33 (RSS)). The authors received financial support from the following organizations: the Spanish Ministry of Education through the FPU program ( FPU16/03057 ) (JAMV); the Spanish Secretariat of State for Research, Development and Innovation through a JdC-I fellowship (CPC); the VULBOS project [ UPO - 1263216 , FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020 ] (RSS); the PinCaR project ( UHU - 1266324 , FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020 ) (AH); Marche Polytechnic University through the Campus World project (MC); and projects AGL2015-73190-JIN , PID2019-110273RB-I00 and RYC-2017-23389 from the Spanish Ministry of Science and Innovation (DMB).

Background Forests are an important component of the global carbon (C) cycle and can be net sources or sinks of CO2, thus mitigating or exacerbating the effects of anthropogenic greenhouse gas emissions. While forest productivity is often inferred from national-scale yield tables or from satellite products, forest C emissions resulting from dead organic matter decay are usually simulated, therefore it is important to ensure the accuracy and reliability of a model used to simulate organic matter decay at an appropriate scale. National Forest Inventories (NFIs) provide a record of carbon pools in ecosystem components, and these measurements are essential for evaluating rates and controls of C dynamics in forest ecosystems. In this study we combine the observations from the Swiss NFIs and machine learning techniques to quantify the decay rates of the standing snags and downed logs and identify the main controls of dead wood decay. Results We found that wood decay rate was affected by tree species, temperature, and precipitation. Dead wood originating from Fagus sylvatica decayed the fastest, with the residence times ranging from 27 to 54 years at the warmest and coldest Swiss sites, respectively. Hardwoods at wetter sites tended to decompose faster compared to hardwoods at drier sites, with residence times 45–92 and 62–95 years for the wetter and drier sites, respectively. Dead wood originating from softwood species had the longest residence times ranging from 58 to 191 years at wetter sites and from 78 to 286 years at drier sites. Conclusions This study illustrates how long-term dead wood observations collected and remeasured during several NFI campaigns can be used to estimate dead wood decay parameters, as well as gain understanding about controls of dead wood dynamics. The wood decay parameters quantified in this study can be used in carbon budget models to simulate the decay dynamics of dead wood, however more measurements (e.g. of soil C dynamics at the same plots) are needed to estimate what fraction of dead wood is converted to CO2, and what fraction is incorporated into soil.

Under the conditions of ongoing climate change, terrestrial ecosystems will be simultaneously exposed to a permanent rise in atmospheric CO2 concentration and increasing variability of such environmental factors as temperature, precipitation, and UV radiation. This will result in numerous interactions. The interactive effects caused by exposure to such multiple environmental factors are not yet well understood. We tested the hypotheses that enhanced UV radiation reduces the stimulatory effect of elevated CO2 concentration on plant biomass production and that it alters biomass allocation in broadleaved European beech (Fagus sylvatica L.) saplings. Our results after 2 years of exposure confirmed interactive effects of CO2 concentration and UV radiation on biomass production, and particularly on biomass allocation to roots and aboveground biomass. The strongest stimulatory effect of elevated CO2 on aboveground biomass and roots was found under ambient UV radiation, while both low and high UV doses reduced this stimulation. Nitrogen content in the roots and the distribution of nitrogen among leaves and roots were also significantly affected by interaction of CO2 concentration and UV radiation. The observed changes in leaf and root C:N stoichiometry were associated with altered morphological traits, and particularly with a change in the proportion of fine roots. As the biomass allocation and especially the proportion of fine roots can play an important role in effective water and nutrient use and acclimation to future climates, it is essential to obtain a deeper understanding of the links between C:N stoichiometry and biomass accumulation.

Despite its dominance in Central Europe, beech cultivation is not without risks, because drought periods and direct solar radiation of the stem are suspected of causing branch dieback, sunburn and predisposition to attack by the European beech splendour beetle Agrilus viridis. Outbreaks of this beetle occurred in Germany in the early 1950s and in Hungary between 2003 and 2006 following severe precipitation deficiencies and extraordinary high temperatures. Leaf loss and an unusual accumulation of dead branches at the top of the crown of beech trees prompted us to initiate in 2010 a three-year study to investigate whether and to what extent A. viridis infestations are involved in this damage pattern. In eight differently damaged beech stands in Bavaria (south-eastern Germany) we measured the prevalence of A. viridis with flight interception traps in relation to the vitality status of beech, checked the oviposition behaviour of females on trap trees, and investigated the infestation frequency of beech trees depending on stand structure. The prevalence of A. viridis was significantly enhanced in sample plots with more heavily damaged beech trees. At lying trap trees, females preferred parts of the bark for oviposition which had been exposed to south or west when the trees had been standing. Particularly, trees in open stands, distant to neighbours in the south and west as well as damaged by sunburn are predisposed to attack by A. viridis. It was proved that survival of A. viridis occurred in branches at the top of live beech trees from where outbreak situations may be initiated due to climatic conditions like drought and/or extreme temperatures. Prevention of A. viridis infestation consists of avoiding sudden exposure to intense solar radiation of the beech trunk by silvicultural measures.

This study investigated the response patterns of aboveground macrofungal communities to different management stages representing a forest conversion from Norway spruce (Picea abies) to European beech (Fagus sylvatica) in the Eifel National Park, Germany. We used a space-for-time substitution approach with three replicate study sites for each forest conversion stage: (I) even-aged single species Norway spruce, (II) unmanaged Norway spruce windthrow, (III) salvage-logged Norway spruce windthrow, (IV) single Norway spruce tree selection cutting (close-to-nature managed) with European beech underplanting and (V) old-growth, uneven-aged European beech (as reference). We assessed environmental variables and macrofungal sporocarps, while the latter were categorized into functional groups to link taxonomic information to potential ecosystem functions. Overall, we observed 235 macrofungal species. The highest species richness was found in the European beech reference stage, followed by the close-to-nature managed spruce/beech stage, while the Norway spruce stage showed approximately half the species richness, similar to the species level of both windthrow stages. Non-metric multidimensional scaling (NMDS) ordination separated each forest conversion stage into distinct fungal communities, while both windthrow stages could not be distinguished from each other. Beside tree species composition change and forest management, nutrient availability and microclimate were the main drivers of fungal community changes among the five differently-managed stages. Further, different functional groups responded in different patterns to forest management and to explanatory environmental variables. We reinforced the assumption, that old-growth, uneven-aged European beech forests (>120 years) can act as a refugium for unique forest type specific fungal communities with a higher functional structure, especially contrary to non-native, even-aged Norway spruce forests (∼70 years). Single Norway spruce tree selection cutting with further introduction of European beech trees can be an adequate strategy to allow a spruce forest conversion without necessarily reducing the macrofungal species richness and its functional structure. We displayed that ecological consequences of windthrow events can be a depression of fungal species richness and a collapse for the functional structure of fungi, especially after salvage logging. Our study underlines the need of including fungal conservation in forest conversion plans to optimize forest ecosystem integrity and resilience against biotic and abiotic agents, such as windstorm events.

In the past few decades, high nitrogen emissions have reversed the nitrogen limitation of trees. Meanwhile, phosphorus (P) appears as a primary limiting nutrient of many forests in Europe. However, a simple and economic standard method for the determination of the plant-available phosphorus in forest soils, which drives the P supply of the trees, is not yet available. Therefore, we tested two soil extraction methods [citric-acid extract (Pcit), according to Hoffmann et al. (1991) and sodium bicarbonate extract (PHCO3), referring to Olsen et al. (1954)] for analyzing all Bavarian soil samples of the second German National Forest Soil Inventory (NFSI), resulting in a big data set with 342 forest sites and 2232 samples. We combined these results with the standardly gathered soil parameters and tested them as predictors for P nutrition indicated by the foliar P concentrations of the four most important tree species: Norway spruce (Picea abies), European beech (Fagus sylvatica), Scots pine (Pinus sylvestris) and pedunculate/sessile oak (Quercus robur/petraea). During the statistical process, we stepwise reduced the complexity of the prediction models. In our analyses, we achieved the best prediction of foliar P using soil information from the organic layer and mineral soil down to depths of 10 cm and 20 cm. Pcit stocks provided by far the best predictions in nearly all cases. Based on this parameter, we derived parametric regression functions to estimate the P nutrition (spruce: R2 = 0.52∗∗∗; beech: R2 = 0.49∗∗∗; pine: R2 = 0.39∗∗∗; oak: R2 = 0.35∗∗∗). Based on logistic regressions, threshold values were deduced for Pcit stocks down to 10 cm soil depth (spruce: 33 kg ha−1; beech: 43 kg ha−1; pine: 32 kg ha−1; oak: 41 kg ha−1), above which P deficiency becomes unlikely. Since these models are based on a large number of sites with diverse geologies and soil conditions, they can be used to estimate the P availability of most forests in Bavaria. Furthermore, the applied methods can be extended to other soil inventories. Estimated P availability based on such functions and thresholds can support sustainable nutrient management of temperate forests.

Mast seeding, the synchronised occurrence of large amounts of fruits and seeds at irregular intervals, is a reproductive strategy in many wind-pollinated species. Although a series of studies have investigated mast year (MY) patterns in European forest tree species at the regional scale, there are few recent evaluations at a European scale on the impact of weather variables (weather cues) and resource dynamics on mast behaviour. Thus the main objective of this study is to investigate the impact of specific weather conditions, as environmental drivers for MYs, on resources in Fagus sylvatica L., Quercus petraea ( Matt.) Liebl. , Quercus robur L., Picea abies (L.) Karst . and Pinus sylvestris L. at a European level and to explore the robustness of the relationships in smaller regions within Europe. Data on seed production originating from the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) were analysed. Three beta regression models were applied to investigate the impact of seasonal weather variables on MY occurrence, as well as the influence of fruiting intensity levels in the years prior to MYs. Resource dynamics are analysed at three different spatial scales (continent, countries and ecoregions). At a European scale, important weather cues for beech MYs were a cold and wet summer two years before a MY, a dry and warm summer one year before a MY and a warm spring in the MY. For spruce, a cold and dry summer two years prior to a MY and a warm and dry summer in the year before the MY showed the strongest associations with the MY. For oak, high spring temperature in the MY was the most important weather cue. For beech and spruce, and to some extent also for oak species, the best fitting models at European scale were well reflected by those found at smaller scales. For pine, best fitting models were highly diverse concerning weather cues. Fruiting levels were high in all species two years before the MY and also high one year before the MY in the oak species and in pine. In beech, fruiting levels one year before the MY were not important and in spruce, they were inconsistent depending on the region. As a consequence, evidence of resource depletion could only be seen in some regions for spruce.

After the durability of wood against wood decay fungi, its water performance is the next most important factor that influences the performance of wood in outdoor, above-ground applications. It is therefore of major importance to optimize methods that are able to predict the moisture behaviour of wood in outdoor applications. In order to elucidate these questions, samples were prepared from European oak (Quercus robur/Q. petraea), sweet chestnut (Castanea sativa), European larch (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris), Norway spruce (Picea abies) and beech (Fagus sylvatica). The moisture performance of the samples was altered by thermal modification, wax, oil and biocide treatment. Two types of specimens were prepared; smaller specimens (1.5 × 2.5 × 5.0 cm) were exposed to natural weathering for three periods (9, 18 and 27 months) and subsequently analyzed in the laboratory with various methods (contact angle, short- and long-term water uptake and water vapor uptake). In parallel, bigger specimens (2.5 × 5.0 × 50 cm) were exposed outdoors in a monolayer exposure and equipped with moisture monitoring sensors for 18 months. Water performance of wood could change as a result of weathering, being the most evident at thermally modified wood, where the decrease of the moisture performance was the most evident. The results of the study clearly showed that the water performance of the majority of the materials decreased with natural weathering. These results indicate that in order to elucidate the moisture performance of wood fully, a variety of laboratory tests needs to be applied, relating to both liquid water performance and water vapour interactions with wood.

Forest stand growth dynamics in Central Europe have accelerated since 1870 due to a rise in temperature, extended growing seasons, and other components of climate change. Based on wood samples from the oldest existing experimental plots in Central Europe, we show that the dominant tree species Norway spruce (Picea abies (L.) H.Karst. ), Scots pine (Pinus sylvestris L.), European beech (Fagus sylvatica L.), and sessile oak (Quercus petraea ( Mattuschka ) Liebl .) exhibit a significant decrease in wood density since more than 100 years. While stand and trees grow faster with respect to wood volume, we can show that wood density decreased by 8–12% since 1900. These results object a naive direct transformation of volume growth trends into an accelerated biomass production. Since 1900, stand biomass increment increased 9–24 percentage points less compared to volume increment (29–100% increase reduces to 20–76%). For a given stem diameter and annual ring width, tree stability against windthrow, wood strength, energy content and C sequestration are even reduced under recent conditions. The generally decreased late wood density, partly going along with an increased early wood fraction, suggests the observed extension of the growing season and fertilization effect of dry deposition as the main causes. Our results indicate that current increased wood volume growth rates must not be straightforwardly converted into sequestrated C and biomass harvest potentials assuming historic values for wood density. This should be taken into account in monitoring, modeling, and utilization of carbon and biomass in forests under global change.

International audience; Tree-related microhabitats (TreMs) are important features for the conservation of biodiversity in forest ecosystems. Although other structural indicators of forest biodiversity have been extensively studied in recent decades, TreMs have often been overlooked, either due to the absence of a consensual definition or a lack of knowledge. Despite the increased number of TreM studies in the last decade, the role of drivers of TreM profile in primary forests and across different geographical regions is still unknown. To evaluate the main drivers of TreM density and diversity, we conducted the first large-scale study of TreMs across European primary forests. We established 146 plots in eight primary forests dominated by European beech (Fagus sylvatica L.) in the Carpathian and Dinaric mountain ranges. Generalized linear mixed effect models were used to test the effect of local plot characteristics and spatial variability on the density and diversity (alpha, beta, and gamma) of TreMs. Total TreM density and diversity were significantly positively related with tree species richness and the proportion of snags. Root mean square tree diameters were significantly related to alpha and gamma diversity of TreMs. Both regions reached similarly high values of total TreM densities and total TreM densities and diversity were not significantly different between the two regions; however, we observed between the two regions significant differences in the densities of two TreM groups, conks of fungi and epiphytes. The density and diversity of TreMs were very high in beech-dominated mountain primary forests, but their occurrence and diversity was highly variable within the landscapes over relatively short spatial gradients (plot and stand levels). Understanding these profile provides a benchmark for further comparisons, such as with young forest reserves, or for improving forest management practices that promote biodiversity.

This study estimates the present and future distribution potential of 12 thermophilic and rare tree species for Europe based on climate-soil sensitive species distribution models (SDMs), and compares them to the two major temperate and boreal tree species (Fagus sylvatica and Picea abies). We used European national forest inventory data with 1.3 million plots to predict the distribution of the 12 + 2 tree species in Europe today and under future warming scenarios of +2.9 and +4.5 °C. The SDMs that were used to calculate the distributions were in a first step only given climate variables for explanation. In a second step, deviations which could not be explained by the climate models were tested in an additional soil variable-based model. Site-index models were applied to the found species distribution to estimate the growth performance (site index) under the given climate. We find a northward shift of 461 km and 697 km for the thermophilic species over the regarded time period from 2060 to 2080 under a warming scenario of 2.9 °C and 4.5 °C, respectively. Potential winners of climatic warming have their distribution centroid below 48°N. Fagus sylvatica and Picea abies will lose great parts of their potential distribution range (approx. 55 and 60%, respectively). An index of area gain and growth performance revealed Ulmus laevis, Quercus rubra, Quercus cerris and Robinia pseudoacacia as interesting alternatives in managed temperate forests currently dominated by F. sylvatica and P. abies. The 12 investigated species are already in focus in forestry and it has been shown that the changing climate creates conditions for a targeted promotion in European forests. Nevertheless, area winners exhibited lower growth performances. So, forest conversion with these warm-adapted species goes hand in hand with loss of overall growth performance compared to current species composition. So, the results are a premise for a further discussion on the ecological consequences and the consistency with forest socio-economic goals and conservation policies.

The effects of structural diversity on the carbon dioxide exchange (CO2) of forests has become an important area of research for improving the predictability of future CO2 budgets. We report the results of a paired eddy covariance tower study with 11 years of data on two forest sites of similar mean stand age, near-identical site conditions, and dominated by beech trees (Fagus sylvatica), but with a very different stand structure (incl. age, diameter distribution, stocks of dead wood and species composition) because of different management regimes. Here we address the question of how management and related structural diversity may affect CO2 fluxes, and tested the hypothesis that more structurally diverse stands are less sensitive to variations in abiotic and biotic drivers. Higher annual net ecosystem productivity (NEP) was observed in the managed, even-aged, and homogenous forest (585 ± 57.8 g C m−2 yr−1), than in the unmanaged, uneven-aged, and structurally diverse forest (487 ± 144 g C m−2 yr−1). About two-third of the difference in NEP between the sites was contributed by a higher annual gross primary productivity (GPP, 1627 ± 164 vs 1558 ± 118 g C m−2 yr−1) and one-third by a lower annual ecosystem respiration (Reco, 1042 ± 60 vs 1071 ± 96 g C m−2 yr−1) in the homogenous forest. Spring (April – May) and summer (June – July) were the two main seasons contributing to the overall annual differences between the sites, also, the sensitivities of seasonal NEP and GPP to environmental variables were stronger in the homogenous forest during those periods. Inter-annual variation of NEP was higher in the homogenous forest (coefficient of variation (CV) = 25%) compared to the heterogeneous forest (CV = 12%). At annual time scale, the higher variability of NEP in the homogenous forest is attributed to biotic factors such as fruit production and a time-dependent growth trend, outweighing differences in environmental sensitivities.

The high structural heterogeneity of primary forests is assumed to positively affect various ecosystem traits and functions, e.g. biodiversity, resilience and adaptability. Against this background, old-growth forest structures are emulated in many managed forests. To properly emulate such structures, quantitative reference values are required, through which primary forests are characterized. In this study, we used the stand structural complexity index (SSCI), derived from terrestrial laser scanning (TLS), to characterize and compare the structures in European beech (Fagus sylvatica L.) dominated forests along a management gradient, ranging from differently managed stands, over formerly managed but now unmanaged stands to primary forests, which have never been managed. The study objective was to quantify and compare the structural complexity of these forests to give insight into possible reference points for an improved prospective handling of managed forests. The highest stand structural complexity was found in primary forests. While there were no significant structural differences between the managed forests, they were more complex in structure than formerly managed forests that have been set aside as National Parks now. The results also showed that structural complexity significantly differed between the investigated stand age classes. Next to primary forests, thickets growing below sheltering overstory trees in managed forests resulted in high structural complexity values. The findings suggest that specific silvicultural management practices can increase the structural complexity in beech forests. This study may facilitate a ‘management for complexity’ in silvicultural practice and might lead the way towards a more precise promotion of three dimensional forest structures that are associated with specific forest functions as part of the stand management objectives.

Production of wood charcoal is a traditional form of forest use that lasted for millennia in most temperate regions, vanishing only some decades ago in the Mediterranean countries. Here, the abandoned charcoal hearths form a network of microhabitats with peculiar vegetation and soil conditions. Previous observational studies showed that establishment of woody species at these sites is severely hindered for unknown reasons. To test the effects of charcoal hearth soil on tree growth we used a common garden experiment with three major Euro-Mediterranean forest trees with different traits and ecology, one evergreen (Quercus ilex, holm oak) and two deciduous (Fagus sylvatica, beech, and Quercus cerris, Turkey oak). These were sown on control and charcoal-enriched soil collected in forest hearths abandoned since decades. Seed germination, seedling growth, photosynthetic efficiency and mortality were measured over a period of two years. Some responses were species-specific, while others were possibly associated to key traits such as evergreen vs. deciduous habit. Although charcoal soil effects were mainly positive on growth rate (height increase), they were mostly negative on germination of beech seeds, survival of holm oak seedlings, and photosynthetic efficiency. Although total biomass was not significantly affected, the root:shoot ratio was increased as a possible effect of physiological drought on hearth soil. These results support field-based evidence that the long persistence of charcoal remains in the soil may be not a favourable condition for forest regeneration. Management implications concern the use of biochar practices to promote forest restoration, which should be further tested on a wide range of species in different life-stages before applications in the field, also considering its long-term consequences.

The paper describes various methods which may be used in determining the deformation energy in the plastic region of bent wood. The present work focuses on various definitions of the plastic work of wood as well as the influence of various factors on its value. Approximated plastic work and total plastic work were determined for beech ( Fagus Sylvatica L.) and aspen ( Populus Tremula L.) wood. We took into consideration the following factors: wood species ( WS ) ( Fagus Sylvatica L. and Populus Tremula L.), material thickness ( MT ) (4, 6, 10, and 18 mm), degree of densification ( DOD ) (10% and 20% of the original thickness), and the number of stressing cycles ( NC ) (0 versus 10,000). The study brings a new quantitative expression of an approximated plastic work “ A W ”, and total plastic work “ B W ” and the values of approximation error “ ΔW ”, which are made due the applied approximation.

The effect of plant cover on soil microbial community structure and activity was investigated in forest ecosystems dominated by holm oak (Quercus ilex), Turkey oak (Quercus cerris) and beech (Fagus sylvatica), in two seasons (autumn and early summer). Microbial community structure was investigated by phospholipid fatty acid (PLFA) profile and ergosterol determination. Microbial community activity was assessed by fluorescein diacetate hydrolisys, β-glucosidase and cellulase activities. The Turkey oak forest showed the lowest soil microbial biomass, both as total and specific PLFA markers. PLFA profile showed a different microbial community structure among forest soils, mainly between the two oak systems. Enzyme activities were affected by soil organic carbon content, with the lowest values measured in Turkey oak. A seasonal effect both on microbial biomass and on enzyme activity was generally observed. Among the investigated forest systems, the beech forest appeared to store more carbon both in aboveground biomass and in soil.

This study presents morphological and phylogenetic characterizations of Nia vibrissa specimens detected on Fagus sylvatica baits, after six months of incubation in moist chambers at the laboratory. The baits had been submerged at Cascais marina, Portugal, during a survey carried out in 2006–2008. Morphological observations evidenced differences in basidiocarp color and in the morphology of the peridial hairs, varying from straight to curved and with bifurcate to non-bifurcate ends. Morphological variability has often been reported, associated to the suggestion that N. vibrissa is a species complex. We addressed this subject through the evaluation of pairwise distances and phylogenetic analyses applying Bayesian and Maximum Likelihood methods, to multi-sequence alignments involving the large subunit (LSU) of the nuclear ribosomal DNA. Even though the six N. vibrissa isolates under analysis consistently clustered together with high support values and most of their pairwise distances ranged between 0 and 3%, one of them presents a higher distance value (4%) relative to other two isolates. These results recommend the need of further genetic evaluations, involving more isolates and gene regions, to answer the question addressed in this study: is N. vibrissa a species complex?

Phosphorus (P) deficiency of beech (Fagus sylvatica L.) is widespread in Europe. However, it is difficult to determine at which sites trees are prone to P deficiency, since foliar analysis is the only tool widely accepted for assessing the P nutritional status of beech. Our central objective was to identify the main influencing factors on organic P in forest soils and to test its usefulness as a predictor of the foliar P content of beech. Our hypotheses were: (1) stocks of total organic P (TOP) and microbial biomass P (MBP) in the mineral soil are higher at mull than at moder/mor sites, (2) the TOP content and the soil organic carbon (SOC):TOP ratio are affected by soil mineralogical characteristics, such as oxalate-extractable iron and aluminum (Feox, Alox) and clay, (3) multiple regression models that include the TOP stock, soil mineralogical parameters and the humus form as predictors are useful to explain the variability of the foliar P content of beech. We sampled the mineral soils of 9 mull and 11 moder/mor sites at 0–50 cm depth and took foliar samples of beech trees in three subsequent years. In contrast to our hypothesis (1), we did not find significantly higher TOP or MBP stocks, but determined lower SOC:TOP ratios at mull compared to moder/mor sites. In line with our hypothesis (2), the TOP content was positively related to Feox, Alox and clay contents, while the SOC:TOP ratio was negatively related to Feox, Alox and clay contents, suggesting strong effects of clay, Al and Fe on the accumulation of TOP. In partial agreement with our hypothesis (3), the TOP stock was included as a positive and the clay content as a negative predictor in a multiple regression model of the foliar P content, suggesting decreasing bioavailability of TOP with increasing clay content. Across all sites, the model consisting of these two parameters better explained the foliar P content (R2 = 0.60) than the stocks of Bray-II- (R2 = 0.37) or Olsen-extractable P (R2 = 0.53) as single predictors. Overall, our results suggest that the accumulation of TOP in forest mineral soils and its potential availability to beech are strongly affected by soil mineralogical parameters, which may be included in statistical models to improve the predictability of P availability to trees.

The photosynthetic responses to the combined effect of drought and heat stress were studied in leaves of 19-years-old European beech (Fagus sylvatica L.) trees originating from five provenances in Central Europe differing by altitude (55–1250 m), and grown in the same experimental plot. The measurements were conducted at the beginning of heat waves, under two different conditions: during a dry period (middle of July) and after recovery in wetter period, at the beginning of August. The decreases of stomatal conductance (gs) and net photosynthesis rate (ACO2) during drought and heat wave stress were very similar in all provenances. However, we observed distinct response of PSII photochemistry on combined drought and high temperature stress, well associated with altitude of origin of the beech provenances. Measurements of pulse amplitude modulated (PAM) fluorescence identified maintenance of a high electron transport rate in beech provenances from high altitudes under drought and heat wave conditions, associated with some decrease of excitation pressure on PSII. This can be explained by enhanced capacity of alternative electron sinks to utilize the excess of electrons as a photoprotective mechanism. The analyses of fast chlorophyll fluorescence kinetics confirmed the differences in responses of PSII photochemistry between provenances originating from different altitudes. Compared with provenances at higher altitudes, we found more sensitive response (i.e. more limited electron transport at the PSII acceptor side and changes in the size of light harvesting complexes) to drought and heat stress, in those growing at low altitudes. Our results support the hypothesis that the provenances originating from higher altitudes possess enhanced phenotypic plasticity related to photoprotective responses, resulting from the long-term adaptation to marginal mountain conditions.

The study aims to assess variability in leaf water isotopic enrichment occurring in the field under natural conditions. We focused on seasonal variation and difference between sun-exposed and shaded leaves. Isotopic composition (δ18O, δ2H) of leaf water was monitored in a beech tree (Fagus sylvatica L.) growing in the forest-meadow ecotone together with δ18O (2H) of water compartments which are in close relation to this signal, namely twig and soil water. The sampling was carried out in approximately two-week intervals during five consecutive vegetation seasons. The δ18O (2H) data showed a distinct seasonal pattern and a consistency in relative differences between the seasons and sample categories. Leaf water was the most isotopically enriched water compartment. The leaf water enrichment decreased toward the autumn reflecting the change in δ18O (2H) of source water and evaporative demands. The soil and twig water isotopic signal was depleted against current precipitation as it partly retained the isotopic signature from winter precipitation however the seasonal pattern of soil and twig water followed that of precipitation. No significant differences between sun-exposed and shaded samples were detected. Nevertheless, the observed strong seasonal pattern of isotope composition of leaf, twig and soil water should be taken into account when using leaf water enrichment for further calculations or modeling.

Links between biodiversity and ecosystem functioning are well established. Beyond biodiversity per se, community composition can have strong effects on ecosystem functioning. Furthermore, spatial processes including edge effects, can impact the diversity-functioning relationship. These spatial processes are especially relevant within a food web context, such as the transfer of plant biomass across the food chain through herbivory. The relative importance of diversity, community composition and spatial context on herbivory pressure at the community and the species level is, however, poorly understood. To fill this gap in our understanding, we studied to what degree herbivory in temperate forest plots varies according to edge distance, tree diversity and forest composition. In contrast to the prevailing view of tree herbivory increasing at forest edges, we found that the effects of forest edge and tree diversity on leaf herbivory were masked by effects of forest composition, i.e. the specific contributions of the tree species. The strongest composition effect found was increased herbivory on Quercus robur in the presence of Fagus sylvatica. Our findings highlight that neither edge distance, tree diversity, nor the interaction affected one ecosystem function, namely herbivory, whilst tree community composition did. This warrants consideration of identity and composition effects in future studies if we are to deepen our understanding of the determinants of ecosystem functions across systems.

Lateral vehicle impact tests on moulded wooden tubes were performed to estimate the suitability for infrastructure equipment like lighting poles. Initial speeds of the impacting vehicle of 35, 50 and 100 km/h were tested. Both the tested unreinforced tubes and a glass fibre reinforced tube were classified in energy absorption category NE according to EN 12767. A numerical model was developed in the finite element software LS-DYNA to establish a simulation tool for infrastructure equipment made of moulded wooden tubes. The simulations confirmed the experimental results regarding the failure behaviour and the quantitative deceleration of the vehicle during the crash.

Many non-native tree species have been introduced to Europe to improve forest productivity. It is assumed that some of these species are better able than native species to mitigate negative effects of climate change. A high growth-related tolerance to climatic extremes is essential to qualify a tree species’ suitability for cultivation and must be quantified before initiating adaptation measures. This study investigated basal area and volume increment (BAI and VI) data at various stem height positions to evaluate inter-annual growth variation (mean sensitivity) and drought tolerance of seven alien tree species (Acer rubrum L., Betula maximowicziana Regel, Castanea sativa Mill, Cryptomeria japonica D. Don, Metasequoia glyptostroboides Hu et Cheng, Thuja plicata Donn and Tsuga heterophylla Sarg.) which are considered stress tolerant, and two native species (Fagus sylvatica L., Picea abies H. Karst.) in the Arboretum Burgholz in West Germany. We found that mean sensitivity and response to drought (resistance, recovery, resilience) were related; i.e., sensitive species exhibited greater drought response than less sensitive species. In the drought years 2003, 2006 and 2010/2011, VI of the highly sensitive species C. japonica and P. abies and rather moderate sensitive A. rubrum decreased most strongly (36%), while less sensitive C. sativa and T. heterophylla were the most resistant tree species (25% decrease). B. maximowicziana, F. sylvatica, M. glyptostroboides and T. plicata were moderately sensitive to drought events (growth depression by 29%). Recovery after drought showed mainly a reverse response pattern; species with lower resistance recovered faster, but this trade-off was not uniform among species. Across drought events, we observed high variation in the response of individual trees and between different tree species. This finding indicates that species’ drought sensitivity depends strongly on the drought’s onset, duration and frequency. Along tree stems, mean sensitivity and response to drought in 2003 decreased species-specifically from lower to upper stem section height. Thus, quantifying drought sensitivity based solely on breast height measures may result in biased estimates of production declines.

Canopy gaps play a crucial role for forest dynamics processes, as they largely determine light transmission to lower canopy strata, thereby controlling the turnover of tree individuals in the stand. Even though their functional importance is undisputed, quantitative data on the rate of gap creation and gap closure, and the temporal change in gap size distribution patterns in temperate virgin forests are scarce. We used a repeated inventory (line-intercept sampling) of gap size frequency and fraction in a virgin beech (Fagus sylvatica) forest in the Slovakian Carpathians over a 10-year interval (2003–2013) to test the hypotheses that (i) disturbance intensity and thus gap creation and gap closure rate change only little over time, (ii) gaps persist or even expand, until they are filled primarily by vertical ingrowth of trees from lower strata, and (iii) gap creation promotes the height growth of released saplings and sub-canopy trees. In the 2003 and 2013 inventories, 37 and 30 gaps >20 m2 size were mapped along a total of 3217 m transect line investigated. The large majority of gaps was 500 m2 were very rare. Gap fraction decreased significantly from 13.6% in 2003 to 8.2% in 2013 (associated with a reduction in mean gap size from 261 to 96 m2), indicating considerable variation in disturbance intensity in the past decades. Before 2003, both large gaps (probably caused by wind throw) and small gaps (from dying trees) have been formed, while only small gaps developed in the period 2003–2013. Small gaps were closed within a few years through rapid horizontal canopy expansion of neighboring beech trees, while vertical gap filling through ingrowth of lower canopy layers and regeneration was the dominant process in larger gaps. Saplings and trees in lower canopy layers formed a heterogeneous understory in large parts of recently formed gaps and responded to this process with increased height growth. We conclude that, despite considerable variation in disturbance intensity over time, this beech virgin forest responds to gap formation with high resilience through rapid lateral canopy expansion in small gaps and ingrowth of saplings and sub-dominant tree layers in larger gaps.

The frequent occurrence of very large trees (diameter at breast height DBH ≥ 80 cm) is a typical element of both primary and secondary old-growth forests. We analyzed the characteristics of very large trees in one of the few stands of lowland old-growth beech forest in Northwestern Europe, regenerated around 1775 and left unmanaged since 1986. We examined their density, diameter range, increment, mortality rate and spatial distribution, based on repeated full dendrometric surveys. In order to evaluate the results, we compared them to original datasets from primary and secondary old-growth beech forests in Europe, and an extensive reference table, compiled from inventories and literature. In our study site, the density of very large trees increased from 31.5 to 34.3 trees ha−1 over the last 25 years, reaching a median DBH of 97 cm (mean 98.9), with the largest tree attaining a DBH of 159 cm. Although the trees were over 240 years old, they still showed an average DBH increment of 4.75 mm year−1 and a low mortality rate (0.89% year−1), indicating that they were still vital. These figures are remarkably high compared to other old-growth beech forest reference sites, where the density of very large trees generally varies between 5 and 20 trees ha−1 (median value 13.1), with a median diameter of 85–90 cm and maximum DBH for beech trees rarely exceeding 100–130 cm. The regular spatial distribution pattern of the very large trees in the studied stand clearly differed from a typical old-growth stand, in which very large trees are randomly distributed. Over the last 25 years though, because of random mortality and ingrowth, the spatial distribution gradually became more random. The extraordinary densities and sizes of the very large trees in our study site can be explained by the favorable climate and site conditions that promote high increments, in combination with the former management interventions of tending and thinning that resulted in continuous non-suppressed growth. Although derived from a very specific case with particular conditions, our observations may be relevant to other beech forests, as they tend to reset certain baseline assumptions for tree size and longevity potential of beech in Northwestern Europe.

The light environment of trees is a strong driver for their growth and morphology. Manipulating the light regime in forests is one of the main tools available to control the forest development. This study analysed the effect of a drastic light addition through gap creation on beech saplings (Fagus sylvatica L.) that had initially established under the canopy of mature trees. Altogether 6 gaps of varying size were created on an area of 4 ha. A total of 51 saplings were incorporated in this study. The saplings’ above- and belowground biomass compartments were destructively harvested along a light gradient. Relationships between light availability and growth increment, stress relief, biomass allocation, and growth morphology were analysed. Along the gradient of increasing light availability, beech saplings responded with an increased diameter growth, whereas the height growth remained unaffected. Also the root mass fraction increased at the expense of the leaf mass fraction. Other biomass compartments showed no significant trend. The mean branch weight also increased and the specific leaf area decreased. Other morphological traits were not affected by the light availability. The results lead to the conclusion that the morphological plasticity of the beech saplings towards light was not as high as initially expected. Furthermore, the sudden increase of light availability did not impose stress on the saplings. Finally, managing the light regime is appropriate to achieve specific goals.

Old-growth beech (Fagus sylvatica L.) forests in Europe show a structural heterogeneity, which distinguish from managed ones. Recent investigations revealed that facilitative belowground interactions might counteract aboveground competition for light. However, the exact interaction of these mechanisms is unclear. We developed the BEEchPlasticity (BEEP) model to investigate whether the mere focus on the aboveground competition for canopy space with subsequent modeling of the light transmittance through the forest canopy suffices to reproduce the observed structural attributes. The BEEP model is individual-based, and explicitly describes the plasticity of tree crowns in a three-dimensional space through a geometric approach. This conceptual design allows tracing neighborhood effects to the forest stand level. We ran 10 simulation experiments with 1000 time steps on a simulation area of 0.5oha. We analyzed the emerging spatial point patterns, gap dynamics as well as distributions of tree age, tree height, tree crown projection area, and tree diameter. By applying various indices that revealed the emergent horizontal and vertical forest structure, we were able to show a strong mutual link between beech crown plasticity and forest heterogeneity. The crown plasticity enabled the trees to close small gaps, which resulted in a highly dynamic tree regeneration, which in turn led to a small-scale heterogeneous forest structure. We found that, over long periods, crown centroids of canopy trees taller than 20om were more regularly distributed than stem foot points. Absolute crown displacements were greater than reported from beech stands in North-Germany and the Sudetes in the Czech Republic. This indicates a need to restrain the model crown growth in order to recognize tree architecture and stability. We could simulate an increasing forest structural heterogeneity. Starting with a structural homogeneous layer of tree saplings, we showed that forest structures similar to those in unmanaged beech forests took several tree generations or approximately 700 time steps to emerge. We recommend enhancing this model approach with spatial explicit modeling of the leaf-area distribution, which has already been done for single beech trees.

Tree growth is a key ecosystem function supporting climate change mitigation strategies. However climate change may induce feedbacks on radial growth and wood density, affecting the carbon sequestration capacity of forests. Using a mixed modeling technique long-term trends in radial growth, wood density and above-ground biomass, defined as the product of the annual basal area growth with the wood density, of common beech (Fagus sylvatica) and sessile oak (Quercus petraea) in the Belgian Ardennes, were determined and explained using climate drivers of change. This modeling strategy allowed us to determine if the same conclusions can be drawn when only BAI is considered, as is assumed in most carbon sequestration studies, when looking at long-term trends in carbon sequestration. The models indicate that above-ground biomass increment changes over time are more driven by changes in radial growth than by changes in wood density. Nevertheless, the assumption of constant wood density in most carbon sequestration studies is incorrect. Ignoring wood density results in an underestimation of long-term trends in above-ground biomass increment for beech, and an overestimation of above-ground biomass increment for oak. Interesting is that radial growth is mostly driven by climate variables of the current year, whereas wood density is more driven by the climate variables of the previous year. Beech radial growth and wood density is found to be negatively influenced by drought and positively by water availability. Oak radial growth and wood density is negatively affected by late frost and positively by water availability. The findings of this study suggest that radial growth in combination with wood density should be used in carbon sequestration studies as different climate driven long-term trends in radial growth and wood density are found.