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Climate warming advances the onset of tree growth in spring, but above- and belowground phenology are not always synchronized. These differences in growth responses may result from differences in root and bud dormancy dynamics, but root dormancy is largely unexplored. We measured dormancy in roots and leaf buds of Fagus sylvatica and Populus nigra by quantifying the warming sum required to initiate above- and belowground growth in October, January and February. We furthermore carried out seven experiments, manipulating only the soil and not air temperature before or during tree leaf-out to evaluate the potential of warmer roots to influence budburst timing using seedlings and adult trees of F. sylvatica and seedlings of Betula pendula. Root dormancy was virtually absent in comparison with the much deeper winter bud dormancy. Roots were able to start growing immediately as soils were warmed during the winter. Interestingly, higher soil temperature advanced budburst across all experiments, with soil temperature possibly accounting for c. 44% of the effect of air temperature in advancing aboveground spring phenology per growing degree hour. Therefore, differences in root and bud dormancy dynamics, together with their interaction, likely explain the nonsynchronized above- and belowground plant growth responses to climate warming.

Producción Científica, Rear-edge tree populations are experiencing a combination of higher temperatures and more intense droughts that might push individuals beyond their tolerance limits. This trend towards rising atmospheric [CO2] is concurrent with an increase in intrinsic water use efficiency (iWUE), which theoretically enhances photosynthesis and decrease evapotranspiration rates, consequently improving tree resistance to drought. However, it remains unclear whether iWUE is favouring tree growth under current climate conditions, particularly when climate and iWUE legacy effects are simultaneously considered. We evaluated this question with an extensive sampling along Iberian rear-edge (dry) populations comprising four mountain ranges and two distinct altitudes. We simultaneously examined the effects of climate and iWUE on secondary growth using annually resolved basal area increments (BAIs) for the period 1901–2017. We used linear mixed models including second-order autocorrelation and 1-year legacy effects of iWUE and summer drought. BAI and iWUE increased across the studied period. iWUE increase was driven by changes in atmospheric CO2 concentration and water availability during the growing season. Climate and iWUE exerted direct and lagged effects on beech growth. Water availability during growing season was the main driver of tree growth, combining direct and indirect effects through its impact on iWUE. Legacy effects of water availability and iWUE were more important than growing season conditions. The net effect of iWUE shifted when lagged effects were considered, resulting in a net negative impact on tree growth. Synthesis: Our results reveal that climate and iWUE legacy effects must be considered to assess the net iWUE effect on secondary growth. Considering lagged effects, the current increase in iWUE is constraining tree growth. Modelling efforts of tree growth response to climate warming should include climate and iWUE legacy effects to adequately assess terrestrial ecosys, EU Feder Funds; EU LIFE, Grant/Award Number: LIFE Soria Forest Adapt (LIFE19 CCA/ES/001181), Junta de Castilla y León - Consejería de Educación (Grant/Award Number: IR2020-1- UVA08; VA171P20), Ministerio de Ciencia e Innovación (Grant/Award Number: LAUREL PID2019-109906RA-I00 MCIN/AEI/10.13039/5011); (PROWARM PID2020-118444GA-100 MCIN/AEI/10.13039/50); (Postdoctoral grant IJC2019-040571-I MCIN/AEI/10.13); (Predoctoral grant PRE2018-084106 funded by MCIN/AE); and (spRING CGL2017-87309-P MCIN/AEI/10.13039/501100011)

Producción Científica, Healthy soils are the second C sink on Earth, and this sink could last for hundreds or even thousands of years as stable soil organic matter (SOM). Forest soils, in particular, have the potential to store significant amounts of C, however, the amount of C sequestered and the carbon-to-nitrogen (C/N) ratio of soil organic matter (SOM) depend on the vegetation influencing the soil. In the last decades, mixed stands have aroused great interest among the scientific community, but it is still necessary to intensify research on its effect on soils and their C storage capacity. In this study, we assess soil C sequestration potential in soil and litter of mixed and pure stands of Scots pine and beech (Pinus sylvestris–Fagus sylvatica). Three triplets (9 forest plots), two located in Southern Poland and one in Southern Germany were studied. A total of 40 circular subplots of 5 m radius were selected within the triplets, covering a wide range of species mixture, and soil and litter were sampled. Data were analyzed at two scales (plot-level and microsite-level) to determine which option is more appropriate when studying the mixing effect on SOM. Cstock in forest floor ranged between 2.5 and 11.1 Mg C ha−1 and in mineral soil between 39.6 and 337.8 Mg ha−1. According to our findings, the percentage of species mixture primarily impacted the forest floor rather than the mineral soil. On the forest floor, stands with 25–50% pine in the mixture were found to have a C/N ratio between 20 and 30, which indicates an equilibrium state between mineralization and immobilization. In the mineral soil, total organic C was the only variable affected by mixture percentage (p < 0.1). Finally, microsite-level scale proved to be the most appropriate when studying tree stand composition effect on SOM, as the plot-level scale diluted or masked some effects., Junta de Castilla y León - projects "Servicios ecosistémicos de los suelos bajo masas forestales mixtas versus masas puras. Efecto del tipo de masa en la fertilidad edáfica, retención de agua y secuestro de carbono" (REF. V096G19), (CLU-2019-01) and (CL-EI-2021-05), Ministerio de Ciencia e Innovación - project “IMFLEX: gestión forestal integrada por gradientes de complejidad”(FPU 2016-BOE 17-01-2017), Publicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCLE, European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no.778322

vorgelegt von Markus Finner, in englischer Sprache, Masterarbeit Universität Innsbruck 2023

The extent of the potassium (K) limitation of forest productivity is probably more widespread than previously thought, and K limitation could influence the response of forests to future global changes. To understand the effects of K limitation on forest primary production, we have developed the first ecophysiological model simulating the K cycle and its interactions with the carbon (C) and water cycles. We focused on the limitation of the gross primary productivity (GPP) by K availability in tropical eucalypt plantations in Brazil. We used results from stand-scale fertilisation experiments as well as C flux measurements in two tropical eucalypt plantations to parameterise the model. The model was parameterised for fertilised conditions and then used to test for the effects of contrasting additions of K fertiliser. Simulations showed that K deficiency limits GPP by more than 50 % during a 6-year rotation, a value in agreement with estimations in K-limited eucalypt stands. Simulations showed a decrease of modelled canopy transpiration of around 50 % and a decrease in modelled water-use efficiency WUEGPP of 10 %. Through a sensitivity analysis, we used the model to identify the most critical processes to consider when studying K limitation of GPP. The inputs of K to the stands, such as the atmospheric deposition and weathering fluxes, and the regulation of the cycle of K within the ecosystem were critical for the response of the system to K deficiency. Litter leaching processes were of lower importance, since residence time of K in litter was low. The new forest K-cycle model developed in the present study includes multiple K processes interacting with the carbon and water cycles, and strong feedbacks on GPP were outlined. This is a first step in identifying the source or sink limitation of forest growth by K.

[EN] Effects of climate change on water use efficiency (WUE) and its components, measured at different temporal and spatial scales in Fagus sylvatica.

Rear-edge tree populations are experiencing a combination of higher temperatures and more intense droughts that might push individuals beyond their tolerance limits. This trend towards rising atmospheric [CO] is concurrent with an increase in intrinsic water use efficiency (iWUE), which theoretically enhances photosynthesis and decrease evapotranspiration rates, consequently improving tree resistance to drought. However, it remains unclear whether iWUE is favouring tree growth under current climate conditions, particularly when climate and iWUE legacy effects are simultaneously considered. We evaluated this question with an extensive sampling along Iberian rear-edge (dry) populations comprising four mountain ranges and two distinct altitudes. We simultaneously examined the effects of climate and iWUE on secondary growth using annually resolved basal area increments (BAIs) for the period 1901–2017. We used linear mixed models including second-order autocorrelation and 1-year legacy effects of iWUE and summer drought. BAI and iWUE increased across the studied period. iWUE increase was driven by changes in atmospheric CO concentration and water availability during the growing season. Climate and iWUE exerted direct and lagged effects on beech growth. Water availability during growing season was the main driver of tree growth, combining direct and indirect effects through its impact on iWUE. Legacy effects of water availability and iWUE were more important than growing season conditions. The net effect of iWUE shifted when lagged effects were considered, resulting in a net negative impact on tree growth. Synthesis: Our results reveal that climate and iWUE legacy effects must be considered to assess the net iWUE effect on secondary growth. Considering lagged effects, the current increase in iWUE is constraining tree growth. Modelling efforts of tree growth response to climate warming should include climate and iWUE legacy effects to adequately assess terrestrial ecosyste

Extreme climate events such as late spring frosts (LSFs) negatively affect productivity and tree growth in temperate beech forests. However, detailed information on how these forests recover after such events are still missing. We investigated how LSFs affected forest cover and radial growth in European beech (Fagus sylvatica L.) populations located at different elevations at four sites in the Italian Apennines, where LSFs have been recorded. We combined tree-ring and remote-sensing data to analyse the sensitivity and recovery capacity of beech populations to LSFs. Using daily temperature records, we reconstructed LSF events and assessed legacy effects on growth. We also evaluated the role played by elevation and stand structure as modulators of LSFs impacts. Finally, using satellite images we computed Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and LAI (Leaf Area Index) to evaluate the post-LSF canopy recovery. The growth reduction in LSF-affected trees ranged from 36 % to 84 %. We detected a negative impact of LSF on growth only during the LSF year, with growth recovery occurring within 1–2 years after the event. LSF-affected stands featured low vegetation indices until late June, i.e. on average 75 days after the frost events. We did not find a clear relationship between beech forest elevation and occurrence of LSFs defoliations. Our results indicate a high recovery capacity of common beech and no legacy effects of LSFs.

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)

Wood growth phenology of temperate deciduous trees is less studied than leaf phenology, hindering the understanding of their interaction. In order to describe the variability of wood growth and leaf phenology across locations, species and years, we performed phenological observations of both xylem formation and leaf development in three typical temperate forest areas in Western Europe (Northern Spain, Belgium and Southern Norway) for four common deciduous tree species (Fagus sylvatica L., Betula pendula Roth., Populus tremula L. and Quercus robur L.) in 2018, 2019 and 2020, with only beech and birch being studied in the final year. The earliest cambial reactivation in spring occurred at the Belgian stands while the end of cambial activity and wood growth cessation generally occurred first in Norway. Results did not show much consistency across species, sites or years and lacked general patterns, except for the end of cambial activity, which occurred generally first in birch. For all species, the site variation in phenophases (up to three months) was substantially larger than the inter-annual variability (up to six weeks). The timeline of bud-burst and cambium reactivation, as well as of foliar senescence and cessation of wood growth, were variable across species even with the same type of wood porosity. Our results suggest that wood growth and leaf phenology are less well connected than previously thought. Linear models showed that temperature is the dominant driver of wood growth phenology, but with climate zone also having an effect, especially at the start of the growing season. Drought conditions, on the other hand, have a larger effect on the timing of wood growth cessation. Our comprehensive analysis represents the first large regional assessment of wood growth phenology in common European deciduous tree species, providing not only new fundamental insights but also a unique dataset for future modelling applications.

Aim of study: Although beech (Fagus sylvatica L.) forests in north-western Spain constitute c.a. 40% of the total area occupied by the species in the whole country, no growth or yield studies have been carried out regarding these forests. The specific objective of this study was to elaborate yield tables and stand density management diagrams for the beech forests. Area of study: Asturias and León provinces (NW Spain). Material and methods: Sample plots (n=112) were established in natural beech forests, and 60 dominant trees were felled for sampling. The Asturias Government Forest Service provided data on another 351 felled trees. Yield tables and stand density management diagrams (SDMDs) were elaborated to estimate tree volume and biomass in the study area for the first time. Main results: These forests are more productive than expected. Although they are currently not managed for forestry purposes, they could be managed again in the future and the tools are now available for this purpose. Research highlights: The study generates new user-friendly tools to manage beech forests in northwestern Spain. These tools will also enable simulations to be conducted to determine the potential carbon storage or the capacity of the stands to sequester atmospheric carbon.

The increasing disturbances in monocultures around the world are testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increase with species richness, although the ecological fundaments have mainly been investigated through diversity experiments. To adequately manage forest ecosystems, it is necessary to have a comprehensive understanding of the effect of mixing species on the temporal stability of productivity and the way in which this it is influenced by climate conditions across large geographical areas. Here, we used a unique dataset of 261 stands combining pure and two-species mixtures of four relevant tree species over a wide range of climate conditions in Europe to examine the effect of species mixing on the level and temporal stability of productivity. Structural equation modelling was employed to further explore the direct and indirect influence of climate, overyielding, species asynchrony and additive effect (i.e. temporal stability expected from the species growth in monospecific stands) on temporal stability in mixed forests. We showed that by adding only one tree species to monocultures, the level (overyielding: +6%) and stability (temporal stability: +12%) of stand growth increased significantly. We identified the key effect of temperature on destabilizing stand growth, which may be mitigated by mixing species. We further confirmed asynchrony as the main driver of temporal stability in mixed stands, through both the additive effect and species interactions, which modify between-species asynchrony in mixtures in comparison to monocultures. Synthesis and applications. This study highlights the emergent properties associated with mixing two-species, which result in resource efficient and temporally stable production systems. We reveal the negative impact of mean temperature on temporal stability of forest productivity and how the stabilizing effect of mixing two species can counterbalance thi

Increasing species diversity is considered a promising strategy to mitigate the negative impacts of global change on forests. However, the interactions between regional climate conditions and species-mixing effects on climate-growth relationships and drought resistance remain poorly documented. In this study, we investigated the patterns of species-mixing effects over a large gradient of environmental conditions throughout Europe for European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.), two species with contrasted ecological traits. We hypothesized that across large geographical scales, the difference of climate-growth relationships and drought resistance between pure and mixed stands would be dependent on regional climate. We used tree ring chronologies derived from 1143 beech and 1164 pine trees sampled in 30 study sites, each composed of one mixed stand of beech and pine and of the two corresponding pure stands located in similar site conditions. For each site and stand, we used Bootstrapped Correlation Coefficients (BCCs) on standardized chronologies and growth reduction during drought years on raw chronologies to analyze the difference in climate-tree growth relationships and resistance to drought between pure and mixed stands.We found consistent large-scale spatial patterns of climate-growth relationships. Those patterns were similar for both species. With the exception of the driest climates where pure and mixed beech stands tended to display differences in growth correlation with the main climatic drivers, the mixing effects on the BCCs were highly variable, resulting in the lack of a coherent response to mixing. No consistent species-mixing effect on drought resistance was found within and across climate zones. On average, mixing had no significant effect on drought resistance for neither species, yet it increased pine resistance in sites with higher climatic water balance in autumn. Also, beech and pine most often differed in the timing

The number of species classified as red-listed has increased by 11% between 2015 and 2020, with beetles and butterflies being especially affected. Among these are the vulnerable longhorned beetle (Stictoleptura scutellata) and the endangered false blister beetle (Ischnomera sanguinicollis). Forty percent of all known species in Sweden are dependent on hostplants, indicating the value in mapping potential habitats, including food sources for those species. Both Stictoleptura scutellata and Ischnomera sanguinicollis are dependent on dead wood from beech (Fagus sylvatica) for sheltered housing and flowering bushes in close proximity (e.g. edge vegetation) for pollen and nectar. The management technique in beech forest used in the mid-1800s and early 1900s have resulted in homogenous beech forests, lacking dead wood, old trees and tree structures such as cracks, cavities and torn branches (Maser & Trappe, 1984; Nilsson & Baranowski, 1995; Serup, 2005). These structures are vital habitat for many associated species, including Stictoleptura scutellate and Ischnomera sanguinicollis (Serup, 2005; Siitonen, 2001). Eight Natura 2000 classified beech forests (Asperulo-Fagetum and Luzulo-Fagetum types) were visited, with the forest edge being closely analysed and mapped using a Garmin GPSMAP 64 and ArcGIS Pro. Both edges with existing edge vegetation and areas suitable for plantation of edge vegetation were of interest and shown in maps overlying orthophotos of each area. Additional work was done on developing a method suitable for finding areas remotely suitable for plantation of edge vegetation. All areas visited included some form of edge vegetation, although many areas lacked the space or environment for plantations of more flowering bushes along the edge of the Natura 2000 classified beech forests. Suggestions of plantations of edges was made for all areas, although not always along beech forest edges, as edge vegetation can benefit other species as well, not only Stictole

The raccoon (Procyon lotor) has been a part of German fauna since the 1920s, following a number of releases and escapes from captivity. This study intends to investigate the distribution and activity patterns of this non-native mesopredator in Hainich National Park, which lies in Central Germany, in-between 3 core areas of established raccoon populations. I analysed metadata from over 12,000 camera trap pictures of raccoons, which were sampled by 120 camera traps distributed over Hainich National Park. I compared this to meteorological data covering the same area and spatial variables within a 4-km-buffer around the National Park. The study period covered winter and early spring during each of the 3 consecutive years 2017 to 2019. A total of 2,300 raccoons were recorded by all camera traps across all study periods during 2,095 trigger events. Being highly mobile, the large majority of raccoons stayed not even one minute inside the camera frame. Over 99 % of recordings showed adults which might be explained by the study periods being temporally placed in-between reproductive cycles. Raccoons, both in their native and their new range, are known to be nocturnal animals, thus it was predictable that they were significantly more active during the night, defined as the period between one hour after sunset until one hour before sunrise. Activity during the rest of the day, especially during dusk, increased steadily with each month of the study period. General raccoon activity followed the same pattern until a sudden decrease in April. Ground temperature was the only climate variable for which a significant (positive) correlation could be shown. This was in accordance with studies on original and new raccoon range expansion. However, a dormant period, as shown for raccoons in a similar habitat in Germany, could not be seen. Habitat preferences differed depending on the testing method: A considerable proportion of raccoons were sampled in mixed deciduous forest, while most r

The increasing disturbances in monocultures around the world are testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increase with species richness, although the ecological fundaments have mainly been investigated through diversity experiments. To adequately manage forest ecosystems, it is necessary to have a comprehensive understanding of the effect of mixing species on the temporal stability of productivity and the way in which this it is influenced by climate conditions across large geographical areas. Here, we used a unique dataset of 261 stands combining pure and two-species mixtures of four relevant tree species over a wide range of climate conditions in Europe to examine the effect of species mixing on the level and temporal stability of productivity. Structural equation modelling was employed to further explore the direct and indirect influence of climate, overyielding, species asynchrony and additive effect (i.e. temporal stability expected from the species growth in monospecific stands) on temporal stability in mixed forests. We showed that by adding only one tree species to monocultures, the level (overyielding: +6%) and stability (temporal stability: +12%) of stand growth increased significantly. We identified the key effect of temperature on destabilizing stand growth, which may be mitigated by mixing species. We further confirmed asynchrony as the main driver of temporal stability in mixed stands, through both the additive effect and species interactions, which modify between-species asynchrony in mixtures in comparison to monocultures. Synthesis and applications. This study highlights the emergent properties associated with mixing two-species, which result in resource efficient and temporally stable production systems. We reveal the negative impact of mean temperature on temporal stability of forest productivity and how the stabilizing effect of mixing two species can counterbalance thi, The increasing disturbances in monocultures around the world are testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increase with species richness, although the ecological fundaments have mainly been investigated through diversity experiments. To adequately manage forest ecosystems, it is necessary to have a comprehensive understanding of the effect of mixing species on the temporal stability of productivity and the way in which this it is influenced by climate conditions across large geographical areas. Here, we used a unique dataset of 261 stands combining pure and two-species mixtures of four relevant tree species over a wide range of climate conditions in Europe to examine the effect of species mixing on the level and temporal stability of productivity. Structural equation modelling was employed to further explore the direct and indirect influence of climate, overyielding, species asynchrony and additive effect (i.e. temporal stability expected from the species growth in monospecific stands) on temporal stability in mixed forests. We showed that by adding only one tree species to monocultures, the level (overyielding: +6%) and stability (temporal stability: +12%) of stand growth increased significantly. We identified the key effect of temperature on destabilizing stand growth, which may be mitigated by mixing species. We further confirmed asynchrony as the main driver of temporal stability in mixed stands, through both the additive effect and species interactions, which modify between-species asynchrony in mixtures in comparison to monocultures. Synthesis and applications. This study highlights the emergent properties associated with mixing two-species, which result in resource efficient and temporally stable production systems. We reveal the negative impact of mean temperature on temporal stability of forest productivity and how the stabilizing effect of mixing two species can counterbalance thi

Legacies of past climate conditions and historical management govern forest productivity and tree growth. Understanding how these processes interact and the timescales over which they influence tree growth is critical to assess forest vulnerability to climate change. Yet, few studies address this issue, likely because integrated long-term records of both growth and forest management are uncommon. We applied the stochastic antecedent modelling (SAM) framework to annual tree-ring widths from mixed forests to recover the ecological memory of tree growth. We quantified the effects of antecedent temperature and precipitation up to 4 years preceding the year of ring formation and integrated management effects with records of harvesting intensity from historical forest management archives. The SAM approach uncovered important time periods most influential to growth, typically the warmer and drier months or seasons, but variation among species and sites emerged. Silver fir responded primarily to past climate conditions (25–50 months prior to the year of ring formation), while European beech and Scots pine responded mostly to climate conditions during the year of ring formation and the previous year, although these responses varied among sites. Past management and climate interacted in such a way that harvesting promoted growth in young silver fir under wet and warm conditions and in old European beech under drier and cooler conditions. Our study shows that the ecological memory associated with climate legacies and historical forest management is species-specific and context-dependent, suggesting that both aspects are needed to properly evaluate forest functioning under climate change.

Soil pollution by mercury (Hg) is a global problem that poses risks to natural ecosystems and to human health. Forests represent an important recipient of Hg deposition, however, so far, very little is known about the tree species identity effects on the distribution of Hg in forest soils and its accumulation in edible mushrooms. To clarify the effect on the two main Central-European commercial forest tree species, soil samples were collected from organic F+H horizons and from mineral soil depths of 0-2, 2-10, 10-20, and 20-30 cm in mature Norway spruce (Picea abies (L.) H. Karst.) and European beech (Fagus sylvatica L.) dominated stands. Mushroom samples of the Boletaceae family were also collected at each sampling site. The highest Hg contents were found in the F+H layer and were significantly higher in spruce- (mean 0.46 +/- 0.03 mg/kg) than in beech- (mean 0.29 +/- 0.10 mg/kg) dominated stands. The variation in Hg contents in F+H was best predicted by pH, the overall lower soil pH in strongly acidic spruce stands might induce Hg immobilization in the F+H layer to cause a decrease in the bioavailability of Hg for Xerocomellus chrysenteron (Bull.) Sutara. In mineral soil, the Hg contents did not differ significantly between the spruce- and beech-dominated stands. The Hg content strongly correlated with the S, N, and C contents only in mineral soil; at the depths of 2-10, 10-20, and 20-30 cm, significantly also with the silt vs. sand, Al-o, and Fe-o contents. Studied mushroom species were not Hg-contaminated and, therefore, their consumption does not pose serious health risks regardless of the forest type. The results suggest that species-related soil chemistry and mineral associations, rather than different atmospheric Hg interception by spruce vs. beech, drive the vertical distribution and accumulation of Hg in forest soils.

Trees have a strong influence on the chemical properties of the soil in which they grow. Establishing plantations with different tree species combinations thus potentially leads to divergence in soil chemistry. To study the degree to which differentiation already occurs during the first years after establishment, we made use of a biodiversity– ecosystem functioning experiment in Belgium, FORBIO. The multi-site experiment replicates tree species richness (1–4 species) and composition in three sites. The sites represent contrasting site contexts, mostly land-use history, soil, and climate. Soil samples (0–10 cm) were taken at the time of planting and approximately 8 years later. We measured the total C and N concentration, the Olsen P, the pHH2O, and the concentration of base and Al cations. The change in chemical composition was strongly dependent on site conditions including former land use. Afforestation on former cropland had a positive impact on totalCand Olsen P and a negative effect on base cations and pH. On sites reforested after clearcut, soil texture and particular site preparation played an important role. On top of that, we found several significant effects of species composition. Strongest composition effects were detected in the reforested site on loamy soil with little soil disturbance. This study highlights that species choice can already affect soil chemistry in early stages of forest development, but that the nature of the effects may strongly depend on the context in which the plantations are established. Further research is needed to identify the most important contextual factors.

Environmental fluctuations are a common occurrence in an ecosystem, which have an impact on organismic diversity and associated ecosystem services. The aim of this study was to investigate how a natural and a species richness-reduced wood decaying community diversity were capable of decomposing Fagus sylvatica dead wood under a constant and a fluctuating temperature regime. Therefore, microcosms with both diversity levels (natural and species richness-reduced) were prepared and incubated for 8 weeks under both temperature regimes. Relative wood mass loss, wood pH, carbon dioxide, and methane emissions, as well as fungal and bacterial community compositions in terms of Simpson‘s diversity, richness and evenness were investigated. Community interaction patterns and co-occurrence networks were calculated. Community composition was affected by temperature regime and natural diversity caused significantly higher mass loss than richness-reduced diversity. In contrast, richness-reduced diversity increased wood pH. The bacterial community composition was less affected by richness reduction and temperature regimes than the fungal community composition. Microbial interaction patterns showed more mutual exclusions in richness-reduced compared to natural diversity as the reduction mainly reduced abundant fungal species and disintegrated previous interaction patterns. Microbial communities reassembled in richness-reduced diversity with a focus on nitrate reducing and dinitrogen-fixing bacteria as connectors in the network, indicating their high relevance to reestablish ecosystem functions. Therefore, a stochastic richness reduction was followed by functional trait based reassembly to recover previous ecosystem productivity. © Copyright © 2021 Muszynski, Maurer, Henjes, Horn and Noll.

Soil pollution by mercury (Hg) is a global problem that poses risks to natural ecosystems and to human health. Forests represent an important recipient of Hg deposition, however, so far, very little is known about the tree species identity effects on the distribution of Hg in forest soils and its accumulation in edible mushrooms. To clarify the effect on the two main Central-European commercial forest tree species, soil samples were collected from organic F+H horizons and from mineral soil depths of 0-2, 2-10, 10-20, and 20-30 cm in mature Norway spruce (Picea abies (L.) H. Karst.) and European beech (Fagus sylvatica L.) dominated stands. Mushroom samples of the Boletaceae family were also collected at each sampling site. The highest Hg contents were found in the F+H layer and were significantly higher in spruce- (mean 0.46 +/- 0.03 mg/kg) than in beech- (mean 0.29 +/- 0.10 mg/kg) dominated stands. The variation in Hg contents in F+H was best predicted by pH, the overall lower soil pH in strongly acidic spruce stands might induce Hg immobilization in the F+H layer to cause a decrease in the bioavailability of Hg for Xerocomellus chrysenteron (Bull.) Sutara. In mineral soil, the Hg contents did not differ significantly between the spruce- and beech-dominated stands. The Hg content strongly correlated with the S, N, and C contents only in mineral soil; at the depths of 2-10, 10-20, and 20-30 cm, significantly also with the silt vs. sand, Al-o, and Fe-o contents. Studied mushroom species were not Hg-contaminated and, therefore, their consumption does not pose serious health risks regardless of the forest type. The results suggest that species-related soil chemistry and mineral associations, rather than different atmospheric Hg interception by spruce vs. beech, drive the vertical distribution and accumulation of Hg in forest soils.

Soil pollution by mercury (Hg) is a global problem that poses risks to natural ecosystems and to human health. Forests represent an important recipient of Hg deposition, however, so far, very little is known about the tree species identity effects on the distribution of Hg in forest soils and its accumulation in edible mushrooms. To clarify the effect on the two main Central-European commercial forest tree species, soil samples were collected from organic F+H horizons and from mineral soil depths of 0-2, 2-10, 10-20, and 20-30 cm in mature Norway spruce (Picea abies (L.) H. Karst.) and European beech (Fagus sylvatica L.) dominated stands. Mushroom samples of the Boletaceae family were also collected at each sampling site. The highest Hg contents were found in the F+H layer and were significantly higher in spruce- (mean 0.46 +/- 0.03 mg/kg) than in beech- (mean 0.29 +/- 0.10 mg/kg) dominated stands. The variation in Hg contents in F+H was best predicted by pH, the overall lower soil pH in strongly acidic spruce stands might induce Hg immobilization in the F+H layer to cause a decrease in the bioavailability of Hg for Xerocomellus chrysenteron (Bull.) Sutara. In mineral soil, the Hg contents did not differ significantly between the spruce- and beech-dominated stands. The Hg content strongly correlated with the S, N, and C contents only in mineral soil; at the depths of 2-10, 10-20, and 20-30 cm, significantly also with the silt vs. sand, Al-o, and Fe-o contents. Studied mushroom species were not Hg-contaminated and, therefore, their consumption does not pose serious health risks regardless of the forest type. The results suggest that species-related soil chemistry and mineral associations, rather than different atmospheric Hg interception by spruce vs. beech, drive the vertical distribution and accumulation of Hg in forest soils.

Soil pollution by mercury (Hg) is a global problem that poses risks to natural ecosystems and to human health. Forests represent an important recipient of Hg deposition, however, so far, very little is known about the tree species identity effects on the distribution of Hg in forest soils and its accumulation in edible mushrooms. To clarify the effect on the two main Central-European commercial forest tree species, soil samples were collected from organic F+H horizons and from mineral soil depths of 0-2, 2-10, 10-20, and 20-30 cm in mature Norway spruce (Picea abies (L.) H. Karst.) and European beech (Fagus sylvatica L.) dominated stands. Mushroom samples of the Boletaceae family were also collected at each sampling site. The highest Hg contents were found in the F+H layer and were significantly higher in spruce- (mean 0.46 +/- 0.03 mg/kg) than in beech- (mean 0.29 +/- 0.10 mg/kg) dominated stands. The variation in Hg contents in F+H was best predicted by pH, the overall lower soil pH in strongly acidic spruce stands might induce Hg immobilization in the F+H layer to cause a decrease in the bioavailability of Hg for Xerocomellus chrysenteron (Bull.) Sutara. In mineral soil, the Hg contents did not differ significantly between the spruce- and beech-dominated stands. The Hg content strongly correlated with the S, N, and C contents only in mineral soil; at the depths of 2-10, 10-20, and 20-30 cm, significantly also with the silt vs. sand, Al-o, and Fe-o contents. Studied mushroom species were not Hg-contaminated and, therefore, their consumption does not pose serious health risks regardless of the forest type. The results suggest that species-related soil chemistry and mineral associations, rather than different atmospheric Hg interception by spruce vs. beech, drive the vertical distribution and accumulation of Hg in forest soils.

Symbiotic foliar fungal endophytes can have beneficial effects on host trees and might alleviate climate-induced stressors. Whether and how the community of foliar endophytes is dependent on the tree neighborhood is still under debate with contradicting results from different tree diversity experiments. Here, we present our finding regarding the effect of the tree neighborhood from the temperate, densely planted and 12-years-old Kreinitz tree diversity experiment. We used linear models, redundancy analysis, Procrustes analysis and Holm-corrected multiple t-tests to quantify the effects of the plot-level tree neighborhood on the diversity and composition of foliar fungal endophytes in Fagus sylvatica, Quercus petraea and Picea abies. Against our expectations, we did not find an effect of tree diversity on endophyte diversity. Endophyte composition, however, was driven by the identity of the host species. Thirteen endophytes where overabundant in tree species mixtures, which might indicate frequent spillover or positive interactions between foliar endophytes. The independence of the diversity of endophytes from the diversity of tree species might be attributed to the small plot size and the high density of tree individuals. However, the mechanistic causes for these cryptic relationships still remain to be uncovered.

Drought events weaken trees and make them vulnerable to attacks by diverse plant pathogens. Here, we propose a molecular method for fast screening of microorganisms associated with European beech decline after an extreme drought period (2018) in a forest of Thuringia, Germany. We used Illumina sequencing with a recent bioinformatics approach based on DADA2 to identify archaeal, bacterial, and fungal ASVs (amplicon sequence variants) based on bacterial and archaeal 16S and fungal ITS genes. We show that symptomatic beech trees are associated with both bacterial and fungal plant pathogens. Although the plant pathogen sequences were detected in both discolored and non-discolored wood areas, they were highly enriched in the discolored wood areas. We show that almost each individual tree was associated with a different combination of pathogens. Cytospora spp. and Neonectria coccinea were among the most frequently detected fungal pathogens, whereas Erwinia spp. and Pseudomonas spp. were the dominant bacterial plant pathogens. We demonstrate that bacterial plant pathogens may be of major importance in beech decline.

A recent paper by Schall et al. (2020) concluded that beech forests managed in even-aged (EA) rotation systems were more efficient than unmanaged (UNM) forest and forest managed in uneven-aged (UEA) selective cutting systems in supporting landscape-scale biodiversity in Germany. The authors based their conclusion on a comprehensive multitaxon survey and a promising resampling model for assessing gamma diversity at landscape scale. Here, we challenge their conclusions and evaluate the importance of UNM forests for conservation of forest biodiversity. The average amount of dead wood reported from EA stands (27.8 m3/ha) was almost 30% higher than reported from UNM stands (21.6 m3/ha) in the study. Averages from long UNM temperate forests in Europe are typically six to seven times higher (131–157 m3/ha). We therefore conclude the UNM studied stands to reflect legacies of former management, and to be poorly representative of UNM forests. Data from our own studies, including long UNM beech stands in Denmark, demonstrate how this shortcoming seriously undermines the general validity of the presented results to conservation of forest biodiversity. Synthesis and applications. Preservation and restoration of intact forest ecosystems remains essential to biodiversity conservation. We show that the findings of Schall et al. (2020) do not contradict this important notion. Schall and colleagues identified UEA management systems as potentially inferior to more traditional EA management systems for conserving forest biodiversity at the landscape scale. The paper also provides insight into the limited short-term conservation value of simply abandoning forest management in intensively managed landscapes. Based on this, we call for discarding the current orthodox view of non-intervention when new forest reserves are created in temperate Europe. Active reinforcement of natural disturbance regimes and active habitat creation may lead to faster recover

Resource allocation to different plant tissues is likely to be affected by high investment into fruit production during mast years. However, there is a large knowledge gap concerning species-specific differences in resource dynamics. We investigated the influence of mast years on stem growth, leaf production, and leaf carbon (C), nitrogen (N), and phosphorus (P) concentrations and contents in Fagus sylvatica, Quercus petraea, and Q. robur at continental and climate region scales using long-term data from the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and similar datasets. We discussed the results in the light of opposing resource dynamics hypotheses: (i) resource accumulation before mast years and exhaustion after mast years (resource storage hypothesis), (ii) shifting resources from vegetative to generative compartments (resource switching hypothesis), and (iii) investing resources concurrently in both vegetative and generative compartments (resource matching hypothesis). Linear mixed-effects modelling (LMM) showed that both stem growth and leaf production were negatively influenced by weather conditions which simultaneously lead to high fruit production. Thus, the impact of generative on vegetative growth is intermixed with effects of environmental factors. Superposed epoch analyses and LMM showed that for mast behaviour in F. sylvatica, there are indicators supporting the resource storage and the resource switching hypotheses. Before mast years, resources were accumulated, while during mast years resources switched from vegetative to generative tissues with reduced stem and leaf growth. For the Quercus species, stem growth was reduced after mast years, which supports the resource storage hypothesis. LMM showed that leaf C concentrations did not change with increasing fruit production in neither species. Leaf N and P concentrations increased in F. sylvatica, but not in Quercus species. Lea

Dieback in temperate forests is understudied, despite this biome is predicted to be increasingly affected by more extreme climate events in a warmer world. To evaluate the potential drivers of dieback we reconstructed changes in radial growth and intrinsic water-use efficiency (iWUE) from stable isotopes in tree rings. Particularly, we compared tree size, radial-growth trends, growth responses to climate (temperature, precipitation, cloudiness, number of foggy days) and drought, and changes in iWUE of declining and non-declining trees showing contrasting canopy dieback and defoliation. This comparison was done in six temperate forests located in northern Spain and based on three broadleaved tree species (Quercus robur, Quercus humilis, Fagus sylvatica). Declining trees presented lower radial-growth rates than their non-declining counterparts and tended to show lower growth variability, but not in all sites. The growth divergence between declining and non-declining trees was significant and lasted more in Q. robur (15–30 years) than in F. sylvatica (5–10 years) sites. Dieback was linked to summer drought and associated atmospheric patterns, but in the wettest Q. robur sites cold spells contributed to the growth decline. In contrast, F. sylvatica was the species most responsive to summer drought in terms of growth reduction followed by Q. humilis which showed coupled changes in growth and iWUE as a function of tree vigour. Low growth rates and higher iWUE characterized declining Q. robur and F. sylvatica trees. However, declining F. sylvatica trees became less water-use efficient close to the dieback onset, which could indicate impending tree death. In temperate forests, dieback and growth decline can be triggered by climate extremes such as dry and cold spells, and amplified by climate warming and rising drought stress.

A growing number of field studies report isotopic offsets between stem water and its potential sources that prevent the unambiguous identification of plant water origin using water isotopes. We explored the causes of this isotopic offset by conducting a controlled experiment on the temperate tree species Fagus sylvatica. We measured d2H and d18O of soil and stem water from potted saplings growing on three soil substrates and subjected to two watering regimes. Regardless of substrate, soil and stem water d2H were similar only near permanent wilting point. Under moister conditions, stem water d2H was 11 ± 3 more negative than soil water d2H, coherent with field studies. Under drier conditions, stem water d2H became progressively more enriched than soil water d2H. Although stem water d18O broadly reflected that of soil water, soil stem d2H and d18O differences were correlated (r = 0.76) and increased with transpiration rates indicated by proxies. Soil stem isotopic offsets are more likely to be caused by water isotope heterogeneities within the soil pore and stem tissues, which would be masked under drier conditions as a result of evaporative enrichment, than by fractionation under root water uptake. Our results challenge our current understanding of isotopic signals in the soil plant continuum. © 2020 The Authors. New Phytologist © 2020 New Phytologist Trust

The relationship between trees and root-associated fungal communities is complex. By specific root deposits and other signal cues, different tree species are able to attract divergent sets of fungal species. Plant intraspecific differences can lead to variable fungal patterns in the root’s proximity. Therefore, within the Beech Transplant Experiment, we analyzed the impact of three different European beech ecotypes on the fungal communities in roots and the surrounding rhizosphere soil at two time points. Beech nuts were collected in three German sites in 2011. After one year, seedlings of the different progenies were out-planted on one site and eventually re-sampled in 2014 and 2017. We applied high-throughput sequencing of the fungal ITS2 to determine the correlation between tree progeny, a possible home-field advantage, plant development and root-associated fungal guilds under field conditions. Our result showed no effect of beech progeny on either fungal OTU richness or fungal community structure. However, over time the fungal OTU richness in roots increased and the fungal communities changed significantly, also in rhizosphere. In both plant compartments, the fungal communities displayed a high temporal turnover, indicating a permanent development and functional adaption of the root mycobiome of young beeches.

Denna studie fokuserar på en sedimentsekvens som hämtats från Odensjön, i Söderåsens nationalpark i Skåne, södra Sverige. Den undersökta sekvensen, som täcker de översta 86 cm av sedimenten, är unik på grund av dess väldigt tydliga årsvarv, som har möjliggjort en precis datering (Hertzman in prep.). Tilläggsvis, den stora mängden välbevarade Fagus sylvatica-blad synliga i sedimenten yngre än cirka 1930 v.t., tyder på att en stor vegetationsförändring inträffade i sjöns omgivning omkring denna tid. Med en redan definierad kronologi undersöktes sedimentssekvensen utifrån dess paleoekologiska arkiv (pollen och plantmakrofossil). Målet var att uttyda hur skogssammansättningen och öppenheten har förändrats i sjöns omgivning från 1500 v.t., med fokus på utvecklingen från 1930 v.t., och undersöka hur sådana förändringar kan vara kopplade till förändringar i markanvändning, liksom andra faktorer som förändrat landskapet, i det omgivande området. En dendrokronologisk studie utfördes även för att ytterligare fastställa etableringen av den lokala Fagus-populationen som finns runt Odensjön. Kartmaterial och fotografier användes i kombination med de paleobotaniska metoderna för att underlätta tolkningen av skogens sammansättning och öppenhet. De insamlade data antyder att en initial nedgång av bokskog inträffade i mitten av 1500-talet på grund av en kombination av faktorer som överexploatering, överbetning samt genomförande av markreformer. Det studerade området tros nå sitt mest öppna stadium under mitten av 1700- till mitten av 1800-talet, vilket indikeras av låga värden på trädtaxa i pollen- och makrofossilarkiven, tillsammans med höga pollenprocentandelar av Juniperus, örter och graminider. Under andra hälften av 1800-talet antas skogen växa tätare, vilket indikeras av en ökning av träd taxa-värden i pollen- och makrofossilarkiven, i synnerhet Fagus, och en minskning av Juniperus, örter och graminider. Övergången till en tätare skog antas bero på en förändring i mänsklig akt, This study focuses on a sediment sequence retrieved from Lake Odensjön, positioned within Söderåsen National Park in Scania, southern Sweden. The investigated sequence, covering the uppermost 86 cm of sediments, is unique due to its very distinct annual varves, which have allowed for precise dating (Hertzman in prep.). In addition, the large amount of well-preserved Fagus sylvatica leaves visible in the sediments younger than ca. 1930 CE suggesting that a major vegetational change occurred in the lake surroundings around this time. With an already constrained chronology, the sediment sequence was investigated based on its palaeoecological record (pollen and plant macrofossils). The aim was to decipher how the forest composition and openness have changed in the lake surroundings from 1500 CE, with a focus on the development from 1930 CE, and investigate how such changes may be connected to shifts in land usage, as well as other landscape changing factors, in the surrounding area. A dendrochronological study was also carried out to further determine the establishment of the local Fagus population present around Lake Odensjön. Map material and photographs were used in combination with the palaeobotanical methods to help facilitate the interpretation of the forest composition and openness. The collected data suggests that an initial decline of Fagus forests occurred in the mid-16th century, due to a combination of factors such as overexploitation, overgrazing, and implementation of land reforms. The studied area is believed to have reached its most open stage during the mid-18th to mid-19th century, indicated by sparse macrofossil and pollen records of tree taxa along with high pollen percentages of Juniperus and herbs and graminids. During the second half of the 19th century, the forest is believed to have grown denser, indicated by an increase in tree taxa in the macrofossil and pollen records, in particularly Fagus, and a decrease in shrubs, herbs and graminids. The, För att undersöka hur vegetationen, och särskilt bokskogen, har utvecklats från 1500-talet till nutid i området kring Odensjön i Söderåsens nationalpark har innehållet av pollen och större växtrester studerats i en sedimentborrkärna från sjön. Antalet årsringar i borrkärnor från tio bokträd runt sjön har även räknats, vilket gav information om när den nuvarande bokpopulationens etablerades. Resultaten visar att den nuvarande bokskogen var betydligt öppnare än idag under mitten av 1700-talet fram till mitten av 1800-talet. Kunskap om tidigare ekologiska förändringar och klimatförändringar är avgörande för att förstå dynamiken i de ekosystem vi har idag. Sediment i sjöar utgör ett av de viktigaste arkiven för att studera förändringar i ekosystem och klimat som har skett över hundratals och tusentals år. Sjösediment bildas genom organisk produktion inom sjöns ekosystem samt genom tillförsel av material från sjöns avrinningsområde. Pollenkorn, sporer och makrofossil (löv, rötter, frön, insektsrester m.m.) bevaras i sjösediment och är viktiga biologiska lämningar för studier av ekologiska förändringar. Denna fossila flora och fauna kan ge information om både lokala och regionala ekologiska förändringar omkring den studerade sjön, inklusive förändringar i vegetationens sammansättning, som kan återspegla såväl naturliga som mänskliga processer. Syftet med denna studie var att klarlägg hur skogens sammansättning och öppenheten har förändrats i Odensjöns omgivningar sedan 1500-talet, samt hur sådana förändringar kan ha varit kopplade till förändringar i markanvändningen i det omgivande området. När borrkärnan togs upp noterades det av den del som är yngre än 1930-talet är väldigt rik på synliga boklöv, och därför lades extra fokus på att studera vad som skett i vegetationen kring denna tidpunkt. Kartmaterial och gamla fotografier av området har även använts för att ge indikationer på hur landskapet sett ut bakåt i tiden. Dessutom räknades årsringarna i borrkärnor från tio bo

Tree pathogenic Phytophthora species have been identified as a threat to health and stability of forests und urban trees. In Sweden most Phytophthora species are non-native and potentially invasive, and thus it is important to control their spread. To identify the presence of Phytophthora species in soil from symptomatic forest stands, urban trees and commercial soils, laboratory analyses using a polymerase chain reaction (PCR) with the internal transcript spacers (ITS) pair ITS1oo/ITS4 were conducted. The results revealed that Phytophthora cambivora was present across all habitats and in commercial soils. Furthermore, P. plurivora was detected in one soil sample from an urban area. Indications of other Phytophthora species were found as well but could not be confirmed on species level. The results suggest that Phytophthora are widely present in southern Sweden and provide new evidence that commercial soil can be an important pathway spreading these pathogens. Biolog EcoPlate (Biolog, Inc., Hayward, CA, USA) is a tool recently developed for characterization of functional aspects (enzymatic capacity) in soil microbial communities and were used to study a subset of soil samples. Four soil samples from forests and one from an urban area were used. Clear patterns to categorize the soil microbial activity in different habitats were not detected, which is likely to be due to the low number of biological replicates. The test illustrates the apparent heterogeneity of soil as a substrate and underlines the importance of adequate number of replicates across habitats and the need to take care of standardized sampling and implementation of the method.

eingereicht von Helmut Heinzl, Universität Innsbruck, Diplomarbeit, 2019, (VLID)4481836

Climate warming has lengthened the growing season by advancing leaf unfolding in many temperate tree species. However, an earlier leaf unfolding increases also the risk of frost damage in spring which may reduce tree radial growth. In equatorward populations of temperate tree species, both late frosts and summer droughts impose two constraints to tree growth, but their effects on growth are understudied. We used a tree-ring network of 71 forests to evaluate the potential influence of late frosts and summer droughts on growth in two tree species that reach their southern distribution limits in north-eastern Spain: the deciduous European beech (Fagus sylvatica L.) and the evergreen Silver fir (Abies alba Mill). The occurrence of late frost events and summer drought was quantified by using a high-resolution daily temperature and precipitation dataset considering the period 1950 2012. Late frosts were defined as days with average temperature below 0 °C in the site-specific frost-free period, whereas drought was quantified using the 18 month-long August Standardized Precipitation Evapotranspiration Index (SPEI). The growth of European beech and Silver fir was reduced by the occurrence of both late frost events and summer drought. However, we did not find a significant interaction on growth of these two climate extremes. Beech was more negatively impacted by late frosts, whereas Silver fir was more impacted by summer drought. Further studies could use remote-sensing information or in situ phenological records to refine our frost index and better elucidate how late frosts affect growth, whether they interact with drought to constrain growth, and how resilience mechanisms related to post-frost refoliation operate in beech. © 2019 Elsevier B.V.

Background: Environmental change has resulted in changes in forest growth in Europe during the last century. This has consequences for the products and services delivered by forest. Mixing tree species is often proposed as a strategy to deal with the consequences of climate change. Diversifying forests is believed to result in higher productivity and increased growth stability. Tree species diversity is therefore expected to affect long-term trends in tree radial growth. However, this has not yet been studied. In this paper we study the effect of diversity on the radial growth and its long-term trends for beech and oak trees growing along a gradient of tree species diversity in the loamy region of central Belgium (from monocultures to mixed forests patches up to three species). Results: We found that beech trees have a higher radial growth whereas oak trees have a lower one when growing in mixtures. The contrasting diversity-productivity relationship observed for beech and oak is in agreement with their ranking in shade tolerance, where oaks suffer increased competition in mixed oak patches. Overall, in monocultures and mixtures, an increasing radial growth trend of + 2% for the period 1927–2015 and 21% for the period 1899–2015 was found for beech and oak, respectively. Tree species diversity did not alter the shape of this detected long-term radial growth trend. Nevertheless, for oak a lower year-to-year variability in radial growth is found in mixtures indicating a higher resilience. Conclusion: We conclude that diversity impacts the average radial growth and its variability (only in the case of oak) but not the shape of the long-term trend in radial growth of beech and oak trees growing in the loamy region of central Belgium.

Assisted migration – the intended movement of species and populations to facilitate range expansion – has recently received considerable attention in the face of climate change, since it could serve as a tool to reduce the threats posed to ecosystems and species. Particularly, it is generally expected that trees will not be able to adapt or migrate quickly enough in response to the expected climate change without human help. The topic is, however, controversially discussed, because introducing foreign species to an ecosystem can also have disadvantages, such as displacement of native species, especially when a species becomes invasive. Hybridization between introduced and native plant species is one important factor in the evaluation of invasive plants and can be a threat to biodiversity. European beech (Fagus sylvatica) is one of the economically most important broadleaved trees in Europe and is expected to experience a major shift in its natural area as a consequence of climate change. Therefore, its close relative F. orientalis (Fagus orientalis) has been proposed as an alternative for the future. But it has to be taken into consideration that these two species are known to hybridize in their contact zone in Eastern Europe., Unterstützte Migration - die Bewegung von Arten und Populationen zur Erleichterung der natürlichen Arealausdehnung - hat in letzter Zeit angesichts des Klimawandels grosse Aufmerksamkeit erregt, da es als Instrument zur Verringerung vieler Bedrohungen für Ökosysteme und Arten dienen könnte. Es wird insbesondere erwartet, dass sich Bäume nicht schnell genug anpassen oder migrieren können, um ohne menschliche Hilfe auf den erwarteten Klimawandel zu reagieren. Das Thema wird jedoch kontrovers diskutiert, da die Einführung fremder Arten in ein Ökosystem auch Nachteile mit sich bringen kann. Zum Beispiel die Verdrängung einheimischer Arten, welche insbesondere wenn eine Art invasiv wird auftritt. Die Hybridisierung zwischen fremden und einheimischen Pflanzenarten ist ein wichtiger Faktor bei der Bewertung invasiver Pflanzen und kann eine Bedrohung für die Biodiversität darstellen. Die Rotbuche (Fagus sylvatica) ist einer der wirtschaftlich bedeutendsten Laubbäume Europas und wird voraussichtlich durch den Klimawandel eine starke Veränderung ihres natürlichen Areals erfahren. Daher wurde die nahe verwandte Orientbuche (Fagus orientalis) als Alternative für die Zukunft vorgeschlagen. Dabei ist jedoch zu berücksichtigen, dass diese beiden Arten in ihrer Kontaktzone in Osteuropa bekanntlich hybridisieren.

Ziel dieser Arbeit ist es die Resistenz und Resilienz von Misch- und Reinbuchenwäldern in europäischen Bergregionen gegenüber Störungen und Stressfaktoren in vergangenen Jahren sowie der Gegenwart zu untersuchen und zu analysieren, um daraus auf die Zukunft schließen zu können. Häufiger auftretende Wetterextreme und andere Störfaktoren sind die Konsequenz des Klimawandels, wobei die Auswirkungen in Bergregionen durchschnittlich intensiver sind als anderswo. Die Ziele waren es, herauszufinden ob und wie sich die Resistenz und Resilienz gegenüber den Beeinträchtigungen über die Jahre verändert hat und welchen Einfluss die Baumartenzusammensetzung und die strukturelle Vielfalt in diesen Wäldern darauf hat. Außerdem wurden mögliche Auswirkungen von Höhe, sowie der geografische Standort des Forstes berücksichtigt. Mit den Einzelbaumdaten, die in 51 Standorten vom europaweiten Forschungsnetzwerk CliMo gesammelt wurden, wurden Wachstumsresistenz und -resilienz Indices ausgerechnet. Diese Indices wurden dann als abhängige Variablen in einem generalisierten linear gemischten Modell verwendet. Die Mischung (gemischt oder monospezifisch), die Verteilung (aggregiert, normal oder zufällig), die Bodenfeuchtigkeit (PDSI - trocken, normal oder nass), die Spezies (Buche, Tanne, Fichte) und das Jahr (1987, 2000 und 2013 - Jahre mit auffällig negativem Wachstum) waren feste Faktoren in dem statistischen Modell. Die Höhe, der Standort und das Kambialalter wurden als zufällige Faktoren benützt. Mit zwei verschiedenen Modellen wurde der Einfluss dieser Faktoren auf die Resistenz und Resilienz analysiert. Der geographische Standort war nicht signifikant. Die Höhe hatte Auswirkungen auf die Resistenz der Buche gegenüber Störeinflüssen. Je höher der Forst desto niedriger ist die Resistenz. Die Buche zeigt außerdem eine Steigerung der Resistenz in Mischwäldern von 1987 bis 2013. Reine Buchenwäldern verzeichnen eine umgekehrte Entwicklung. Die Fichte ist heute auch weniger widerstandsfähig al, The main aim of this thesis is to investigate and analyze the resistance and resilience of mixed and pure European beech forests in mountain environments to disturbances in the past and the present to be able to make assumptions for the future. More frequent and extreme disturbances are the consequence of climate change and the effects of this ongoing change are especially strong in mountain regions. The objectives were to find out if the response to disturbances has changed over the years and what kind of influence the species composition and the structural diversity in these forests have on the resistance and resilience. Furthermore, a possible impact of the elevation and/or geographic location of the forest on the growth performance during such disturbances was examined. With the single tree data that was gathered in 51 plots by the European-wide research network CliMo, indices for growth resistance and resilience using the basal area increment were calculated. These indices served as dependent variables in a generalized linear mixed model. The mixture (pure or mixed), the distribution (clumped, regular or random), the soil moisture (PDSI - dry, normal or wet), the species (European beech, silver fir and Norway spruce) and the year (1987, 2000 and 2013 - years with particularly negative growth) were used as fixed factors in the model. The altitude, the plot and the cambial age were used as random factors. By applying two different modeling approaches the impact of these factors on the resistance and resilience could be statistically analyzed. The latitude and longitude of the forest are not significant. A higher altitude implies a lower resistance to stressors and disturbances for beech. There is the tendency to an improvement of the ability to withstand disturbances over time regarding beech in mixed conditions and to a deterioration in monospecific ones. Also spruce shows a lower resistance in more recent years. Fir has higher resilience than Spruce. At dry sit, Lukas Matthias Huss, Arbeit an der Bibliothek noch nicht eingelangt - Daten nicht geprüft, Masterarbeit Universität Innsbruck 2019

Knowledge of the current status of Fagus sylvatica in the Western Pyrenean Region (Northern Iberian Peninsula) is based on its widespread presence in mountain areas. However, the past evolution of this taxon and its links to natural and anthropogenic activities is not well defined. We have compiled all the published palaeobotanical data (macro and micro remains) on this region, including both natural and archaeological deposits and with particular emphasis on available radiocarbon dates. To support our analysis of the evolution of F. sylvatica, we present the palynological study of a new sequence (Gesaleta, Navarre), covering the last 11,400 cal yr BP. The main results of this paper suggest the ancient presence of F. sylvatica in the Western Pyrenean Region from at least the Late Pleistocene and Early and Middle Holocene, with a clear expansion from ca 4,500–3,500 cal yr BP, although with some regional differences. This was the point when European beech became one of the main actors in mountain forests, where it has been exploited for a variety of anthropogenic activities

Context Climate change is expected to have a large impact on the distribution, composition and functioning of forest ecosystems worldwide as trees have only little opportunities to migrate and adaptation via natural selection happens very slowly. Hence, creating resistant and resilient forests is a key challenge for forest management. More insight into the adaptive capacity of trees and forests in their consecutive life and development stages, respectively, and the potential buffering effect of tree species admixing to climate change is thus urgently needed. Objectives FORBIO Climate aimed at scrutinizing the adaptive capacity of pedunculate and sessile oak (Quercus robur and Q. petraea, respectively) and European beech (Fagus sylvatica) and at predicting the future performance of these tree species in Belgium under climate change. More specifically, the project aimed at testing the following hypotheses: (1) epigenetic inheritance mechanisms can increase the adaptive capacity of trees to climate change during the reproduction stage; (2) across subsequent tree development stages, tree performance is more resistant and resilient to climate change in more biodiverse forests. Conclusions Belgian’s future climate is projected to be warmer, with a higher frequency of extreme precipitation events. Parental temperature influenced the germination success, bud phenology and growth of oak and beech seedlings, but we did not observe DNA methylation that could help to explain the phenological change mediated by the parental temperature. Studies on both saplings and mature trees suggested that drought may influence ecosystem processes in young and mature forests, affecting the growth and vitality of trees. Despite the high awareness of climate change as an issue in forest management and the need to adjust management practices, we found a lack of knowledge on how to adapt forest management in order to mitigate the vulnerability of forests under changing climate conditions. The res

Provides information about the physical features, growth requirements, and landscaping functions of American Beech (Fagus grandifolia) and European Beech (Fagus sylvatica)

Se realiza una reconstrucción dendroclimática a partir de los datos de nueve cronologías del taxón Fagus sylvatica repartidas en Polaciones, un valle de la montaña central cantábrica. El trabajo se basa en una relación estadística fiable y replicable entre los datos climáticos de referencia de la Climatic Research Unit y las cronologías de anillos de crecimiento. Los resultados obtenidos en la relación crecimiento-clima para la precipitación resultan estadísticamente significativos para los meses entre abril a agosto, lo que permite reconstruir las variaciones interanuales de ésta entre 1798 y 2011, cubriendo así un periodo en el que no se dispone de registros instrumentales. Por otro lado, se elabora una serie de referencia para el área de análisis y se calculan los años favorables y desfavorables en el crecimiento de la especie. La búsqueda de coincidencias que ayuden a comprender el comportamiento de Fagus sylvatica en respuesta al clima en su ámbito meridional de distribución en Europa, lleva a estimar los años secos y húmedos obtenidos de la reconstrucción, que son puestos en relación con los crecimientos., A dendroclimatic reconstruction is carried out using the data from nine chronologies of the Fagus sylvatica taxon spread out in Polaciones, a valley of the central Cantabrian Mountains. The paper is based on a reliable and replicable statistical relationship between the climatic reference data of the Climatic Research Unit and the growth ring chronologies. The results obtained in the growth-climate relationship for the precipitation are statistically significant for the months of April to August, which helps reconstruct the interannual variations of this between 1798 and 2011, thus covering a period in which instrumental records are not available. Moreover, a reference series for the analysis area is drawn up and the favourable and unfavourable years in the growth of the species are calculated. The search for coincidences that help understand the behavior of Fagus sylvatica in response to the climate in its southern area of distribution in Europe calls for the estimation of the dry and wet years obtained from the reconstruction, which are related to the growth.

The role of climatic extremes on forest dynamics is still not fully understood. This is the case for droughts in temperate forests where growth of tree species is more driven by tree-to-tree competition than by climate. In this study we examine whether droughts shape growth trends and forest dynamics in a temperate forest of beech, oak and birch located in the “Picos de Europa” National Park in northern Spain. We used a dendroecological approach to quantify climate-growth associations and to evaluate growth resilience after droughts. We detected growth releases and quantified the increase in the number of trees established following each drought. Beech was the dominant tree species. Tree growth was only weakly related to climate variables in the three species studied. Oak was more resistant to drought than the other two species in terms of growth, with beech displaying higher vulnerability to drought. A significant association is displayed by all three species among droughts, growth releases and tree establishment pulses. After 1923 and following the dry 1940s, beech presented a peak of growth releases, whereas growth releases in oak and birch were concentrated in the 1960s and 1990s, respectively. Drought-induced growth releases probably reflect gap formation, these gaps being filled by recruitment of the three species.

Over recent decades, forest management in Europe has increasingly moved towards the emulation of natural dynamics. Natural dynamics in beech-oak forests leads to the formation of monospecific beech stands, the oak usually being excluded or restricted to sites with poor growing conditions. However, beech is more vulnerable than oak to drought and high temperatures. In this study, we examine whether climate change could attenuate the dominance of beech and improve the competitive capacity of oak in an old-growth temperate forest located in the “Picos de Europa” National Park, northern Spain. We used a dendroecological approach to reconstruct the competitive capacity of beech and oak and developed a projection for the 21st century based on forecasted climate conditions under three different emission scenarios. Beech is the dominant tree species in the studied forest, where the disturbance regime has favored the replacement of oak by beech. In general oaks are older than beeches and most of the small trees are beeches. Our results show that this substitution process may weaken due to the vulnerability of beech to warmer and drier conditions. Climate change will benefit oak growth over beech over the course of the 21st century, as was observed in the late 20th century. However, the natural gap dynamic benefits beech due to its greater shade-tolerance. Therefore, if the resilience of the ecosystem is to be increased, management strategies favoring oak regeneration are necessary given the better adaptation of oak to climate change.

Climatically controlled allocation to reproduction is a key mechanism by which climate influences tree growth and may explain lagged correlations between climate and growth. We used continent-wide datasets of tree-ring chronologies and annual reproductive effort in Fagus sylvatica from 1901 to 2015 to characterise relationships between climate, reproduction and growth. Results highlight that variable allocation to reproduction is a key factor for growth in this species, and that high reproductive effort (‘mast years’) is associated with stem growth reduction. Additionally, high reproductive effort is associated with previous summer temperature, creating lagged climate effects on growth. Consequently, understanding growth variability in forest ecosystems requires the incorporation of reproduction, which can be highly variable. Our results suggest that future response of growth dynamics to climate change in this species will be strongly influenced by the response of reproduction.

The role of climatic extremes on forest dynamics is still not fully understood. This is the case for droughts in temperate forests where growth of tree species is more driven by tree-to-tree competition than by climate. In this study we examine whether droughts shape growth trends and forest dynamics in a temperate forest of beech, oak and birch located in the “Picos de Europa” National Park in northern Spain. We used a dendroecological approach to quantify climate-growth associations and to evaluate growth resilience after droughts. We detected growth releases and quantified the increase in the number of trees established following each drought. Beech was the dominant tree species. Tree growth was only weakly related to climate variables in the three species studied. Oak was more resistant to drought than the other two species in terms of growth, with beech displaying higher vulnerability to drought. A significant association is displayed by all three species among droughts, growth releases and tree establishment pulses. After 1923 and following the dry 1940s, beech presented a peak of growth releases, whereas growth releases in oak and birch were concentrated in the 1960s and 1990s, respectively. Drought-induced growth releases probably reflect gap formation, these gaps being filled by recruitment of the three species.

Over recent decades, forest management in Europe has increasingly moved towards the emulation of natural dynamics. Natural dynamics in beech-oak forests leads to the formation of monospecific beech stands, the oak usually being excluded or restricted to sites with poor growing conditions. However, beech is more vulnerable than oak to drought and high temperatures. In this study, we examine whether climate change could attenuate the dominance of beech and improve the competitive capacity of oak in an old-growth temperate forest located in the “Picos de Europa” National Park, northern Spain. We used a dendroecological approach to reconstruct the competitive capacity of beech and oak and developed a projection for the 21st century based on forecasted climate conditions under three different emission scenarios. Beech is the dominant tree species in the studied forest, where the disturbance regime has favored the replacement of oak by beech. In general oaks are older than beeches and most of the small trees are beeches. Our results show that this substitution process may weaken due to the vulnerability of beech to warmer and drier conditions. Climate change will benefit oak growth over beech over the course of the 21st century, as was observed in the late 20th century. However, the natural gap dynamic benefits beech due to its greater shade-tolerance. Therefore, if the resilience of the ecosystem is to be increased, management strategies favoring oak regeneration are necessary given the better adaptation of oak to climate change.