Beech Sites Research Articles

Phytogeographical and biological spectrum of vascular flora as an indicator of ecological changes following clear-cutting in Eastern Serbian beech forest sites

Extreme weather events caused considerable harm to the forest ecosystems in Eastern Serbia over a few hard winters, resulting in widespread ice breaks and ice uprooting. Certain forest stands were severely impacted during the winter of 2014-2015, necessitating clear-cutting measures. This research was conducted in the Timok forest area, through examination of the floristic composition in areas subjected to clear-cutting, including natural beech forests and artificially established conifer stands within beech sites (Helleboro odori-Fagetum moesiacae). A phytogeographical and bioecological analysis was conducted five years after clear-cutting. Changes in ecosystems were assessed by analysing the spectra of area-types and plant life forms, with comparisons drawn to the “Vinatovača” old-growth forest, situated in the submontane beech forest of Eastern Serbia. Descriptive analysis of the phytogeographical and bioecological spectra of vascular flora, alongside multinomial correspondence analysis, revealed an increased presence of species from Eurasian, Mediterranean-sub-Mediterranean, and Pontic area-types, as well as hemicryptophytic, phanerophytic, and therophytic life forms in the clear-cut areas. In contrast, the old-growth forest was colonised by species of Central European and Holarctic area-types, along with geophytic life forms. These findings suggest a shift towards xerothermic microclimates in the clear-cut areas and the stronger influence of the continental climate of Eastern Serbia with its extremes on deforested areas, as well as on the processes of forest ecosystem degradation.

Mixed signals of environmental change and a trend towards ecological homogenization in ground vegetation across different forest types

Forest ground vegetation may serve as an early warning system for monitoring anthropogenic global-change impacts on temperate forests. Climate warming may induce a decline of cool-adapted species to the benefit of more thermophilous plants. Nitrogen deposition has been documented to potentially result in soil eutrophication or acidification, which can increase the proportion of species with higher nutrient requirements and species impoverishment caused by competitive exclusion. Abiotic forest disturbances are changing the light conditions in the forest understorey environment. In this resurvey study, we tested the magnitude and direction of change in alpha (species richness) and beta (within-site dissimilarity) diversity and composition of forest ground vegetation in forests of different types in Slovenia over fifteen years. Using plant-derived characteristics (Ellenberg-type indicator values) and by testing a priori predictions concerning expected effects of environmental drivers, we show that the magnitude and direction of forest ground vegetation diversity and floristic changes varies greatly between forest sites. Divergent responses at different sites resulted in low net change of alpha and beta diversity and a weak overall environmental signal. The largest decrease in species number was observed in lowland oak-hornbeam forests, which were also among the sites with the greatest compositional shifts. Changes in beta diversity did not show any consistent trend, and anticipated floristic convergence was not confirmed when all sites were considered. Thermophilization was mainly detected in montane beech sites and alpine spruce forests whereas eutrophication signal was most significant on nutrient-poor sites. Vegetation responses were strongly dependent on initial site conditions. Shrinkage of ecological gradients (process of ecological homogenization) suggests that sites positioned at the ends of the gradients are losing their original ecological character and are becoming more similar to mid-gradient sites that generally exhibit smaller changes. Our results point to the importance of local stand dynamics and overstorey disturbances in explaining the temporal trends in forest ground vegetation. Ground vegetation in Slovenian forests is changing in directions also dictated by multiple regional and global change drivers.

Different patterns of inter-annual variability in mean vessel area and tree-ring widths of beech from provenance trials in Slovenia and Hungary

Key messageStudied beech provenances showed different patterns of inter-annual variability in mean vessel area and ring widths, indicating influence of intraspecific variability and diverse environment on hydraulic conductivity and carbon storage potential.International provenance trials of ecologically and economically important tree species are crucial to deciphering the influence of environmental factors and intraspecific variability on tree growth and performance under climate change to guide assisted gene flow and assisted migration of tree provenances and species. In this context, we compared inter-annual trends in tree-ring widths (carbon sequestration potential) and vessel characteristics (conductivity optimisation) of four beech provenances in two international provenance trials, one in Slovenia (Kamenski hrib, a core beech growing site) and one in Hungary (Bucsuta, a marginal beech site) in 2009–2019. We found different patterns of inter-annual variability in mean vessel area and tree-ring widths among provenances and sites, pointing to diverse genetic background and environmental influence on these two wood-anatomical traits. The average values of the vessel area varied less between provenances at Kamenski hrib than at Bucsuta. Weather conditions differently affected tree-ring width and mean vessel area. Furthermore, the length of the period of response of vessel area to the analysed weather conditions differed in summer and winter periods. The differences in the mean vessel area within the tree ring were more pronounced in the weather-wise extreme years, regardless of the provenance. Consistent with previous studies, we confirmed that site conditions affect the climate sensitivity of trees, which is more pronounced at marginal sites or in extreme years. The findings on how different environmental conditions affect the radial growth of young beech trees of different origin are very important for future forest management.

Vyhodnocení provenienční plochy IUFRO s jedlí obrovskou na lokalitě Drahenice ve středních Čechách ve věku 41 let

The paper deals with growth and prosperity of 25 provenances of grand fir from Washington, Oregon, Idaho and Montana (USA), and from Vancouver (British Columbia, Canada) tested in the international provenance research trial No. 212 – Drahenice (Czech Republic; N49° 31‘ 10‘‘, E13° 57‘ 20‘‘, 570 m a.s.l., acidic beech site). Biometric measurements took place at the age of 41 years; qualitative features were visually assessed according to the IUFRO methodology. The best overall assessment of both production and quality shows provenance 12041 – Oyster Bay (BC). Other provenances with high growing stocks, i.e. 12005 – Bear Mountain (WA), 12038 – Clearwater (ID), 12043 – Sproat Lake (BC) and 12044 – Kaye Road (BC) showed some qualitative shortcomings (lower vitality, worse stem shape or thicker branches). The worst both in production and quality were provenances 12020 – Crescent Creek (OR) and 12011 – Clear Lake (WA). The results confirm the suitability of the current setting of the rules for the transfer of reproductive material from North America to the Czech Republic.

Through eagle eyes—the potential of satellite-derived LAI time series to estimate masting events and tree-ring width of European beech

Masting is a well-known phenomenon in forest science in which trees recurrently produce exceptional high seed amounts throughout their lifespan. Occurring simultaneously across wide regions, masting may impact carbon sequestration and carbon cycling of forest ecosystems. To identify masting-induced changes in tree canopies, remote sensing methods may offer a suitable tool, though so far only few studies have used RS methods to investigate the relationship between masting and tree-ring width (TRW). Therefore, we employed a regional network of 19 European beech sites along a precipitation gradient in north-eastern Germany, providing time series of TRW (1961–2017) and categorical masting data (1992–2020). Combined with leaf area index (LAI) from the medium-resolution satellite sensors SPOT-VGT/PROBA-V and MODIS, we assessed the relationship between all three parameters by correlation analysis. Furthermore, we identified common climatic drivers and spatial masting patterns along gradients of water availability. We found negative relationships for both TRW and LAI with masting and a positive correlation for TRW with LAI for SPOT-VGT/PROBA-V data. Contrary, MODIS LAI provided no significant relationships. Water availability did not impact masting occurrence or intensity. The climate correlations showed that masting and TRW are commonly driven by summer climate in June and July, while we found no correlations between climate and LAI. We conclude that medium-resolved SPOT-VGT/PROBA-V LAI is suitable to observe masting but not to estimate TRW. Nonetheless, the results should be thoroughly interpreted in the context of uncertainties of RS measurements and complex interactions of different environmental drivers.

Tracing the origin of Oriental beech stands across Western Europe and reporting hybridization with European beech – Implications for assisted gene flow

The benefits and risks of human-aided translocation of individuals within the species range, assisted gene flow (AGF), depend on the genetic divergence, on the rate and direction of hybridization, and on the climate transfer distance between the host and donor populations. In this study, we explored the use of Oriental beech (Fagus sylvatica subsp. orientalis), growing from Iran to the Balkans, for AGF into European beech populations (F. sylvatica subsp. sylvatica) that increasingly suffer from climate warming. Using samples from natural populations of Oriental and European beech and microsatellite loci, we identified 5 distinct genetic clusters in Oriental beech with a divergence (FST) of 0.15 to 0.25 from European beech. Using this knowledge, we traced the origin of 11 Oriental beech stands in Western Europe established during the 20th century. In two stands of Greater Caucasus origin, we found evidence for extensive hybridization, with 18% and 41% of the offspring having hybrid status. Climate data revealed higher seasonality with warmer and drier summers across the native Oriental beech sites in comparison to the planting sites in Western Europe. Accordingly, we found that bud burst of Oriental beech occurred four days earlier than in European beech. Overall, our results suggest that AGF of Oriental beech could increase the genetic diversity of European beech stands and may foster introgression of variants adapted to expected future climatic conditions. Our study showcases the evaluation of the benefits and risks of AGF and call for similar studies on other native tree species.

Floristički sastav bukovih staništa pet godina nakon čiste seče i sindinamika biljnih zajednica na sečinama u Timočkom šumskom području

In the winter of 2014/2015, an impactful natural disaster hit the eastern region of Serbia, leading to substantial forest tree damage due to ice breaks and falls. This catastrophe resulted in the near-complete destruction of artificial conifer stands established on beech sites, and varying degrees of damage to natural stands. In response, approximately 2000 hectares of land had to be clear-cut, inducing significant ecosystem transformations that may have altered the floristic composition. This study involved the inventarisation of vascular flora within the clear-cut areas, which was then compared to the floristic composition at similar site condition on location "Vinatovača" beech primeval forest. The key objectives of this research were to assess the extent of degradation experienced by natural beech sites and explore the prospects and courses for establishing natural, indigenous forest ecosystems through natural succession. Following clear-cutting, beech sites exhibited notably greater floristic diversity in contrast to the natural beech primeval forests. Considerable area of beech sites turned into meadows or were weed covered. The study identified 176 taxa of vascular flora on the clearcut sites (107 taxa in the premival forest). In addition to plants from mesophilic beech communities, plants from the aliance of thermophilic communities are also present. The identified plants were categorised into two groups: Pteridophyta, with only 2 species, and Spermatophyta, encompassing 174 species (in contrast, the premival forest had 10 species of Pteridophyta and 97 species of Spermatophyta). The Spermatophyta plants were further classified into two classes: Dicotyledons, represented by 149 species, and Monocotyledons, represented by 25 species (in the premival forest, Dicotyledons accounted for 76 species, and Monocotyledons 21 species).

Dynamics of Soil CO2 Efflux and Vertical CO2 Production in a European Beech and a Scots Pine Forest

The conversion of coniferous forest to deciduous forest is accompanied by changes in the vertical distribution of fine roots and soil organic carbon (SOC) content. It is unclear how these changes affect soil CO2 efflux and vertical soil CO2 production, considering changing climate. Here, we present the results of a 6-year study on CO2 efflux, covering relatively warm-dry and cool-wet years. A combination of the flux-gradient method and closed chamber measurements was used to study the CO2 efflux and the vertical distribution of soil CO2 production in a beech (Fagus sylvatica L.) and a pine (Pinus sylvestris L.) forest in northeast Germany. We observed, on average, similar CO2 efflux with 517 (±126) and 559 (±78) g C m–2 a–1 for the beech site and the pine site, respectively. CO2 efflux at the beech site exceeded that at the pine site during the wet year 2017, whereas in dry years, the opposite was the case. Water availability as indicated by precipitation was the primary determining long-term factor of CO2 efflux, whereas seasonal variation was mainly affected by soil temperature, and—in the case of beech—additionally by soil water content. CO2 efflux decreased more dramatically (-43%) at the beech site than at the pine site (-22%) during the warm-dry year 2018 compared to the cool-wet year 2017. We assumed that drought reduces heterotrophic respiration (Rh) at both sites, but additionally decreases autotrophic respiration (Ra) at the beech stand. Soil CO2 production at the beech site ranged over a greater soil depth than at the pine site, attributed to different fine root distribution. The organic layer and the A horizon contributed 47 and 68% of total CO2 efflux at the beech site and the pine site, respectively. The seasonal patterns of different CO2 efflux between both sites were assumed to relate to different phases of tree physiological activity of deciduous compared to evergreen tree species.

Leaching of inorganic and organic phosphorus and nitrogen in contrasting beech forest soils – seasonal patterns and effects of fertilization

Abstract. Leaching is one major pathway of phosphorus (P) and nitrogen (N) losses from forest ecosystems. Using a full factorial N×P fertilization and irrigation experiment, we investigated the leaching of dissolved organic and inorganic P (DOP and DIP) and N (DON and DIN) from organic layers (litter, Oe/Oa horizons) and mineral A horizons at two European beech sites of contrasting P status. Leachates showed the highest DIP and DIN concentrations in summer and lowest in winter, while dissolved organic forms remained rather constant throughout seasons. During the dry and hot summer of 2018, DOC:DOP and DOC:DON ratios in leachates were particularly narrow, suggesting a release of microbial P due to cell lysis by drying and rewetting. This effect was stronger at the low-P site. The estimated annual mean fluxes from the Oe/Oa horizons in the non-fertilized treatment were 60 and 30 mgm-2yr-1 for dissolved total P and 730 and 650 mgm-2yr-1 for dissolved total N at the high-P and the low-P site, respectively. Fluxes of P were highest in the organic layers and decreased towards the A horizon likely due to sorption by minerals. Fertilization effects were additive at the high-P but antagonistic at the low-P site: at the high-P site, fertilization with +N, +P, and +N+P increased total P fluxes from the Oe/Oa horizon by +33 %, +51 %, and +75 %, while the respective increases were +198 %, +156 %, and +10 % at the low-P site. The positive N effect on DIP leaching possibly results from a removed N limitation of phosphatase activity at the low-P site. Fluxes of DOP remained unaffected by fertilization. Fluxes of DIN and DON from the Oe/Oa horizons increased upon +N and +N+P but not upon +P fertilization. In conclusion, the estimated P fluxes from the A horizons were comparable in magnitude to reported atmospheric P inputs, suggesting that these systems do not deplete in P due to leaching. However, a particularly high sensitivity of DIP leaching to hotter and drier conditions suggests accelerated P losses under the expected more extreme future climate conditions. Increases in P leaching due to fertilization and drying–rewetting were higher in the low-P system, implying that the low-P system is more susceptible to environmental future changes.

Influence of vegetation type and soil properties on soil water dynamics in the Šumava Mountains (Southern Bohemia)

This study focuses on the description of soil water dynamics at four sites with different land cover types, namely beech forest, conifer forest, meadow and clipped grass. The analysis was based on soil tensiometer measurements from five consecutive vegetation seasons (comprising both wet and dry years). We investigated both column average pressure heads and also their vertical distribution. The soil water balance was studied by the HYDRUS-1D model.The highest pressure heads were observed at the grassland site, followed by the meadow site. The forested sites were generally reaching lower pressure head values, which was a result of higher evapotranspiration and different soil properties. The differences between the spruce forest (Picea abies (L.)) and beech forest (Fagus sylvatica L.) were evident namely in dry periods, when the beech site was experiencing lower pressure heads. Contrarily, the spruce site was drier (with recorded lower pressure heads) in wet periods and at the beginning of each season. Compared to the conifer forest, lower pressure heads were observed in beech forest, namely at the bottom of the inspected soil column (down to 100 cm). The inspection of the soil water balance revealed different rates of evapotranspiration and drainage at all sites. The evapotranspiration was highest in the beech canopy followed by spruce and both grass covered sites. The differences between spruce and beech forest were based namely on the water consumption efficiency and differences in interception rates, vertical distribution of the roots, and soil hydraulic properties.

Available Energy Partitioning During Drought at Two Norway Spruce Forests and a European Beech Forest in Central Europe

AbstractPartitioning of the available energy at the Earth's surface into the latent heat (LE) and sensible heat (H) fluxes has important climatological, hydrological, and physiological implications. With the prediction of more frequent droughts in central Europe in the near future, there is a particular need to understand variability in available energy partitioning under drought stress conditions at forest ecosystems that are common in the region, such as Norway spruce and European beech. Using eddy covariance measurements from two Norway spruce sites with contrasting wet and dry climates and one European beech site in the Czech Republic, it was found that the proportion of energy partitioned into H was greater at the spruce sites than at the beech site in all conditions during the growing season. The difference between the mean midday (09:00–15:00) β values for low stress conditions and drought stress conditions was much smaller at the European beech site (β = 1.04 vs. 1.11) than at the wet (β = 1.52 vs. 2.50) and dry Norway spruce (β = 1.80 vs. 2.70) sites, indicating that β was not as sensitive to drought stress at the European beech site as at the Norway spruce sites. The high β values and enhancement of drought conditions through positive feedback processes at Norway spruce stands mean that the potential substitution of Norway spruce monocultures with mixed broadleaf‐coniferous stands in central Europe will likely lessen the severity of droughts and heat waves in the region.

Gas Diffusivity in the Forest Humus Layer

While several diffusivity models have been developed for mineral soils, there are few data for the forest humus layers that overlie, and are distinct from, the mineral soil. We measured soil gas diffusivity of the organic layer of spruce and beech stands. Total pore space and relative soil gas diffusivity were much higher in the humus layer than in mineral soil. An exponential diffusivity function was used to describe relative soil gas diffusivity in the humus layer of all spruce sites using one parameter set. The best-fit parameters exceeded the range recommended for mineral soil, indicating the distinctness in pore structure of mineral soil and the organic layer. Different model parameter sets were required to describe the different types of humus at the beech sites. As a consequence, traditional predictive models developed for mineral soil should not be used to derive diffusivity values to interpret the aeration status of the forest humus layer. Specific parameter sets should be used for calculating soil gas fluxes through these layers using the gradient flux approach.

Intra- and interannual variability in diameter increment of Fagus sylvatica L. and Picea abies L. Karst. in relation to weather variables

We examined the effect of weather variables on radial growth of Norway spruce and European beech at the intra- and interannual level. We used database of regular growth measurements at 9 forest sites distributed along an altitudinal and spatial gradient within the Slovakia and Czech Republic. In the period of 2010–2017, we analysed data from 213 dendrometers with manual reading in monthly or biweekly interval. The mean daily and annual diameter increments were analysed in relation to air temperatures and precipitation observed during the respective growing seasons. The general intra-annual diameter increment was modelled using a log-normal function. Results of modelling suggest that precipitation was a better predicting factor of the increment in spruce, while air temperature enhanced predictions of increments in beech. The highest, eight-year-cumulative increment of spruce (31.1 mm) and beech (22.8 mm) was found in the mixed mountainous forest at Poľana site, where both species occur in their growth optimum. The interspecific comparison of radial growth at this site revealed earlier culmination of increment in spruce compared to beech. The growth-limiting weather conditions for spruce occurred especially during the dry season 2015, while in beech sites the slight decrease of annual increment was observed in 2016. In the lowest altitudes of studied forest sites (beech 350 m a.s.l., spruce 440 m a.s.l.) the radial growth was reduced due to high summer temperatures. In the context of further predicted increase of air temperatures, these altitudinal limits for tree growth should be considered in the future forest management in Central Europe.

Phytosociological analysis of European larch forests in the Southeastern Alps

Abstract Using the (unweighted) average linkage clustering (UPGMA) method we classified 458 phytosociological relevés of Larix decidua forests in the Southeastern Alps into 25 clusters. Based on their analysis we described the following new subassociations: Rhodothamno-Laricetum deciduae geetosum rivalis, sorbetosum chamaemespili, piceetosum abietis, adoxetosum moschatellinae, cystopteridetosum fragilis, cyclaminetosum purpurascentis, dryadetosum octopetalae and sorbetosum ariae. The selected method proved adequate in identifying the differences between larch stands on potential subalpine spruce and beech sites, and larch forests on the upper forest line, as well as the differences between initial larch stages on the upper forest line and more stable development stages on better developed soils on promontories and ledges above the upper beech forest line. Larch forests occur mainly in the altitudinal belt between (1,500) 1,600 and 1,800 (1,900) m, on shady aspects and slopes that are steeper than 30°. They are some of the best preserved forest types in the Southeastern Alps, on smaller surface areas (Macesnje above the Beli Potok valley in the Julian Alps) even virgin forests, and their role as biotopes is exceptional.

Exploratory analysis of structural diversity indicators at stand level in three Italian beech sites and implications for sustainable forest management

The present study introduces an exploratory data analysis based on structural indicators with the aim to assess the effect of silvicultural practices on tree stand structure. The study was carried out in three Italian beech forests of different ages with stand structures that originated from dissimilar regeneration and cultivation techniques (Cansiglio, northern Italy, Chiarano, central Italy, and Mongiana, southern Italy). Ten structural indicators were considered when investigating the latent multivariate relationship between stand structure attributes before and after thinning operations by using a multiway factor analysis (MFA). The MFA results identified the older stand at Cansiglio as more homogeneous for cultivation regimes, and more stable to practices when compared with the younger sites (Chiarano and Mongiana). Heterogeneous stands were sensitive to silvicultural practice thus suggesting their possible impact on forest attributes. The proposed approach proved to be an operational tool to evaluate comprehensively the response of forest structure to planned interventions.

Phytosociological description of mesophilous colline-submontane Fagus sylvatica and Carpinus betulus forests in Slovenian Istria

A phytosociological analysis of 46 relevés of mesophilous colline and submontane Fagus sylvatica as well as (or) Carpinus betulus forests was conducted in Slovenian Istria. It was established that they are frequently syndynamically interrelated: in places, common hornbeam stands are merely a degradation stage on beech sites, and can be classified into the subassociation Ornithogalo pyrenaici-Fagetum fraxinetosum orni (its locus classicus is in the Goriška Brda Hills) and into the new subassociation Ornithogalo pyrenaici-Carpinetum betuli seslerietosum autumnalis. Compared with similar submontane stands from other parts of the western and southwestern Slovenia they are slightly poorer in species, with fewer diagnostic species of alliances Erythronio-Carpinion, Aremonio-Fagion and Tilio-Acerion, order Fagetalia sylvaticae and class Vaccinio-Piceetea, and with more diagnostic species of the order Quercetalia pubescenti-petraeae. Geographically, they are characterised by the taxon Helleborus odorus subsp. istriacus. Although they cover small areas these forests generate high yields and are therefore important both economically and as biotopes of protected species.

European beech in its northeasternmost stands in Europe: Varying climate-growth relationships among generations and diameter classes

Age, genetics and social status of trees affect their sensitivity to environmental factors, and information about such effects is needed for comprehensive assessment of growth potential. Climatic sensitivity of radial increment (i.e., tree-ring width) of introduced European beech (Fagus sylvatica L.) of different generations and social status, growing in its northeasternmost stands in Europe, was studied by dendroclimatological methods. At present, the studied stands occur outside of the natural distribution area of the species, providing opportunity to study adaptability and potential growth of beech in novel environments under changing climate. The sensitivity of radial growth to climatic factors was modulated by the generation and social status (size) of trees. The first generation trees, which were propagated from the material transferred from the northern Germany, were highly sensitive to climatic factors and showed wide spectrum of responses. The dominant trees were particularly sensitive to June precipitation, indicating sensitivity to water deficit in summer. The suppressed trees were mainly sensitive to temperature in the dormant period. Tree-ring width of the second generation trees, which were propagated from the first generation stands, was mainly affected by water deficit in summer, yet the local factors, modulated the mechanisms of response. In one stand, tree-ring width was affected by conditions during the formation of tree-ring, indicating direct influence of weather conditions on xylogenesis. In the other stand, tree-ring width was correlated to weather conditions in the preceding year, suggesting influence via carbohydrate reserves. The effect of social status on climatic sensitivity in the second generation stands was considerably weaker, likely due to the natural and anthropogenic selection of the material best adapted for local conditions. The effect of climatic factors on radial growth of beech has shifted during the 20th century. The effect of autumn temperature has weakened, likely due to warming; the effect of factors related to water deficit in summer has intensified that could be related to both, changes in climate and ageing. The observed climate-growth relationships suggested that conditions in winter have become suitable for beech, yet careful selection of sites/regions with appropriate hydrological conditions appear necessary to counteract the increasing effect of water deficit, hence to ensure productivity of future beech sites in Latvia.

A multi‐layer, closed‐loop system for continuous measurement of soil CO2 concentration

AbstractWe present a setup of measurement devices that allow the continuous measurement of CO2 concentrations at different soil depths using small nondispersive infrared (NDIR) sensors within a 16‐channel closed‐loop system. Hydrophobic, gas‐permeable polypropylene membrane tubes allow an equilibrium of CO2 concentration of circulating air, driven by peristaltic pumps, with soil air. The advantage of this system over other systems is the option to measure up to 16 channels without a time shift between individual measurements, as occurs when using a multiplexer system. Furthermore, the system prevents carry‐over effects. A 16‐position multiplexer provides a connection to an isotopic CO2 analyzer for measurement campaigns. This approach aimed to detect vertical concentration profiles and temporal variation of soil CO2 concentration and δ13C‐CO2 signature in soils and to determine the impact of underlying environmental drivers based on concurrent measurements of soil temperature and moisture. The system was tested by applying it in a beech and a pine forest stand during a period of 15 d. Soil CO2 concentrations were mostly determined by soil temperature as well as by soil moisture at a biweekly scale. At diel scale, the dynamic of soil CO2 concentrations followed the shape of soil temperature, sometimes with some time shift. The observed values of δ13C‐CO2 at 10–30 cm soil depths ranged between –22.0 and –19.0‰ at the beech site and –22.4 and –21.8‰ at the pine site, with a distinct vertical gradient at the beech site. Our results show that the system is reliable in practical application, capable of continuously detecting soil CO2 concentrations and its isotopic signature (δ13C‐CO2) with high temporal resolution.

Importance of the first thinning in young mixed Norway spruce and European beech stands

Experimental results from the first thinning in mixed stands are not broadly experienced by forestry practice. To extend the experience with the thinning of a mixed stand, we studied thinned and unthinned mixtures of Norway spruce with European beech on two study sites in the Czech Republic, which represented different conditions: Všeteč (age of 19–35 years) – originally beech dominated site at 440 m a.s.l. and Deštné (age of 17–33 years) – originally spruce with beech site at 990 m a.s.l. Spruce and beech were mixed individually or in small groups. As the for number of trees, mixtures were 35–54% beech and 46–65% spruce at a lower altitude and 7–30% beech and 70–93% spruce at a higher altitude. In the period 1997–2013, we observed annually: mortality, diameter at breast height of all trees and height of trees (minimum 30 individuals) that represented diameter distribution. Results showed that the growth and development of young mixed spruce/beech stands were positively influenced by the first pre-commercial thinning on both locations. The most pronounced effect of thinning consisted in a decreased amount of basal area of dead trees. On control plots, salvage cut accounted for 34 and 46%, while on thinned plots it reached only 7–8% (thinned from above) and 18% (thinned from below) of basal area periodic increment during the 16-year study period. In contrast, diameter distribution was still relatively wide (i.e. an important amount of thin trees was left) at the end of observations on all plots of both study sites. Thinned stands also showed the better static stability (expressed as an h/d ratio) of dominant spruces compared to unthinned stands on both locations. Additionally, thinning supported the spruce share at a lower altitude and the beech share at a higher altitude.

Five-year volume growth of European beech does not respond to ozone pollution in Italy.

A unique database of stand volume growth, estimated as periodic annual volume increment (in m3ha-1 per year over the period 2001-2005) from 728 European beech (Fagus sylvatica L.) sites distributed across Italy, was used to assess the effects of ambient ozone (O3), expressed as annual average (M24), accumulated exposure above a 40ppb hourly threshold (AOT40), and total stomatal ozone flux (POD0). Growth data were from the National forest inventory of Italy, while climate data and ozone concentrations were computed by the WRF and CHIMERE models, respectively. Results show that the growth increased with increasing solar radiation and air temperature and decreased with increasing number of cold days, while effects of soil water content and O3 were not significant. In contrast, the literature results suggest that European beech is sensitive to both drought and O3. Ozone levels resulted to be very high (48ppb M24, 51,200ppb h AOT40, 21.08mmolm-2 POD0, on average) and thus able to potentially affect European beech growth. We hypothesize that the high-frequency signals of soil water and O3 got lost when averaged over 5years and recommended finer time-resolution investigations and inclusion of other factors of variability, e.g., thinning, tree age, and size.