Beech Stands Research Articles

Effects of diversity of tree species on nutrient cycling and soil-related processes

The long-term consequences of changing beech abundance by admixture of valuable broad-leaved species and its effects on nutrient cycling and soil-related processes are not sufficiently investigated. Four different forest types [i.e., beech-hornbeam-maple-alder (Fagus orientalis-Carpinus betulus-Acer velutinum-Alnus glutinosa), beech-hornbeam-maple (Fagus orientalis-Carpinus betulus-Acer velutinum), beech-hornbeam (Fagus orientalis-Carpinus betulus), and pure beech (Fagus orientalis)] in northern Iran were evaluated. Litter samples were collected via litter traps, and topsoil samples were taken and analyzed for selected properties. It was found that litter quality and turnover time improved with decreasing beech abundance. Soil pH, total N, nutrient pools (i.e., P, K, Ca, and Mg), C and N stock, fine root biomass, earthworm and nematode activities, respiration, microbial biomass N, C and N mineralization, and dissolved organic N were significantly higher under mixed beech stands. However, water content, C/N ratio, and dissolved organic C were found to be significantly higher under pure beech forest type. Greater amount of soil organic C was found under beech and beech-hornbeam-maple-alder, but the microbial biomass C was not significantly different among different forest types. The stands with higher tree diversity enhanced the level of soil qCO2 and particulate organic N. A higher value of microbial entropy was recorded under beech-hornbeam stands, whereas soil particulate organic C increased under beech and beech-hornbeam forest types. Based on the result, the abundance of beech influenced nutrient cycling via litter quality and turnover time. This led to an increase in soil fertility through the admixture of broadleaf species into beech forests.

Evaluation of Harvesting and Marketing Activities with GIS in Beech Log Production Areas (İnebolu Forest Sub-District Sample)

In this study focuses on the planning of harvesting-production and marketing process in beech stands. İnebolu Forest Management District (FMD) has been designated as the study area. Potential beech timber forest with high economic values were identified, and estimated log production quantities were determined. In the marketing phase of the products obtained from harvesting, the best-optimum marketing place points for Forest Sub-district Directorates were determined with the help of geographic information systems. In this study, as the potential for beech timber areas of the Inebolu FMD, a total of 1482.2 hectares of land could be operated with timber production-harvesting oriented. According to the results, 82% of the pure and mixed beech forests could be directed to the stumpage and ramp sale and 18% to depot sales. In this respect, during the production-harvesting and after production, the periods of encountering abiotic and biotic pests of beech logs are reduced. So degradation and economical losses could be minimized.

Admixing Fir to European Beech Forests Improves the Soil Greenhouse Gas Balance

Research highlights: The admixture of fir to pure European beech hardly affected soil-atmosphere CH4 and N2O fluxes but increased soil organic carbon (SOC) stocks at a site in the Black Forest, Southern Germany. Background and objectives: Admixing deep-rooting silver fir has been proposed as a measure to increase the resilience of beech forests towards intensified drying-wetting cycles. Hence, the goal of this study was to quantify the effect of fir admixture to beech forests on the soil-atmosphere-exchange of greenhouse gases (GHGs: CO2, CH4 and N2O) and the SOC stocks by comparing pure beech (BB) and mixed beech-fir (BF) stands in the Black Forest, Germany. Materials and methods: To account for the impact of drying-wetting events, we simulated prolonged summer drought periods by rainout shelters, followed by irrigation. Results: The admixture of fir to pure beech stands reduced soil respiration, especially during autumn and winter. This resulted in increased SOC stocks down to a 0.9 m depth by 9 t C ha−1 at BF. The mixed stand showed an insignificantly decreased sink strength for CH4 (−4.0 under BB and −3.6 kg C ha−1 year−1 under BF). With maximal emissions of 25 µg N m−2 h−1, N2O fluxes were very low and remained unchanged by the fir admixture. The total soil GHG balance of forest conversion from BB to BF was strongly dominated by changes in SOC stocks. Extended summer droughts significantly decreased the soil respiration in both BB and BF stands and increased the net CH4 uptake. Conclusions: Overall, this study highlights the positive effects of fir admixture to beech stands on SOC stocks and the total soil GHG balance. In view of the positive impact of increased SOC stocks on key soil functions such as water and nutrient retention, admixing fir to beech stands appears to be a suitable measure to mitigate climate change stresses on European beech stands.

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.

Effects of forest management on herbivorous insects in temperate Europe

Herbivorous insects play an important role in forest ecosystems, but their response to forest management is not well known. We tested how various aspects of forest management affect the abundance and species richness as well as the community composition of herbivorous insects in temperate European forests, applying a large scale approach that included 126 forests in three regions, two forest strata (understory and canopy), and three herbivorous guilds (xylophages, leaf chewers, plant suckers). Forest management was characterized by a recently developed silvicultural management index, stand developmental stage, and dominating tree species. We sampled more than 44,710 individuals of 698 species of herbivorous Coleoptera and Hemiptera. Overall, forest management caused shifts in herbivore community composition. Responses of abundances and species richness varied between feeding guilds and forest strata. Forest management intensity had opposing effects on herbivores in the two forest strata, with abundances tending to be negatively affected in the canopy layer but positively in the understory. Effects on species richness were weak overall and only significant in plant suckers, with slightly higher species richness at high management intensities. Stand developmental stage of beech forests mainly impacted plant suckers, with abundance increasing with stand age. However, a general positive effect of stand age on forest herbivores can be suggested, as abundances of all feeding guilds responded positively to stand biomass. Oak forests were found to harbor a significantly higher species richness of leaf chewers and the highest abundance of plant suckers compared to all other stands. And while canopies of pine stands exhibited low abundances of leaf chewers, they were found to have positive effects on plant sucker species richness compared to pure beech stands. Our results show that management intensity significantly alters the species composition and abundances of forest herbivores, albeit effects vary depending on forest stratum. This strongly suggests that the forest canopy needs to be considered for a reliable estimation of the consequences of forest management on herbivorous insects. Decisions on tree species composition should be made diligently, as they have significant impact on the abundance and species richness of some forest herbivores and, consequently, also on the ecosystem processes they shape.

Effect of auxins on the native proteolytic activity of forest soils

AbstractThe soil proteolytic complex plays an important role within mineral nutrient cycling in ecosystems. Both auxins and proteases are produced by soil microbiota, and reciprocally, their activities affect the metabolic role of biota in soil. The objective of this study was to find out whether auxins (indole‐3‐acetic acid, indole‐3‐butyric acid, 1‐naphthaleneacetic acid and 2‐naphthoxyacetic acid) have a stimulatory or inhibitory effect on the activity of native proteases in soil. The results presented here demonstrate the positive effect of auxins on the native proteolytic forest soil activity. For example, in organic Oe horizons synthetically produced auxins stimulated native proteolytic activity in the European beech stands, where NOA led to the highest increase in L‐tyrosine production (from 564.02 µg at 0 µg auxin to 645.19 µg at the auxin dose of 100 µg). Comparing organic and organomineral horizons, auxins promote a higher stimulation of protease activity in the organic horizons. Comparing the different forest stands, auxins promote a high stimulation of protease activity in European beech stands. In the organomineral soil horizons, auxins promote a high stimulation of protease activity in Leptosols in European beech stands and Cambisols in pedunculate oak stands. The results confirmed the interrelationships between auxins and the native proteolytic forest soil activity from the viewpoint of dead organic matter decomposition. Furthermore, the general importance of substances produced in the rhizosphere for nitrogen cycling was verified.

Reconstructing Soil Recovery from Acid Rain in Beech (Fagus sylvatica) Stands of the Vienna Woods as Indicated by Removal of Stemflow and Dendrochemistry

Our goal was to reconstruct soil recovery from Acid Rain based upon removal of stemflow at beech (Fagus sylvatica) stands of known historic and recent soil status. Fourteen beech stands in the Vienna Woods were selected in 1984 and again in 2012 to study changes in soil and foliar chemistry over time. A part of those stands had been strip cut, and to assess reversibility of soil acidification, we analyzed soils around beech stumps from different years of felling, representing the years when acidic stemflow ceased to affect the soil. Furthermore, it was hypothesized that changes of soil chemistry are reflected in the stemwood of beech. Half-decadal samples of tree cores were analyzed for Ca, Mg, K, Mn, Fe, and Al. Soil analyses indicated recovery in the top soil of the stemflow area but recovery was delayed in the between trees areas and deeper soil horizons. Differences in soil pH between proximal and distal area from beech stumps were still detectable after 30 years indicating that soils may not recover fully from acidification or do so at a rather slow rate. Stemwood contents indicated mobilization of base cations during the early 80s followed by a steady decrease thereafter. Backward reconstructions of soil pH and soil nutrients, building on regressions between recent stemwood and soil chemistry, could not be verified by measured soil data in 1984, but matched with declining cation foliar contents from 1984 to 2012. Dendrochemical reconstructions showed highest values in the 1980s, but measured soil exchangeable cation contents were clearly lower in 1984. Hence, we conclude that our reconstructions mimicked soil solution rather than soil exchanger chemistry.

Landscape-Scale Mixtures of Tree Species are More Effective than Stand-Scale Mixtures for Biodiversity of Vascular Plants, Bryophytes and Lichens

Tree species diversity can positively affect the multifunctionality of forests. This is why conifer monocultures of Scots pine and Norway spruce, widely promoted in Central Europe since the 18th and 19th century, are currently converted into mixed stands with naturally dominant European beech. Biodiversity is expected to benefit from these mixtures compared to pure conifer stands due to increased abiotic and biotic resource heterogeneity. Evidence for this assumption is, however, largely lacking. Here, we investigated the diversity of vascular plants, bryophytes and lichens at the plot (alpha diversity) and at the landscape (gamma diversity) level in pure and mixed stands of European beech and conifer species (Scots pine, Norway spruce, Douglas fir) in four regions in Germany. We aimed to identify compositions of pure and mixed stands in a hypothetical forest landscape that can optimize gamma diversity of vascular plants, bryophytes and lichens within regions. Results show that gamma diversity of the investigated groups is highest when a landscape comprises different pure stands rather than tree species mixtures at the stand scale. Species mainly associated with conifers rely on light regimes that are only provided in pure conifer forests, whereas mixtures of beech and conifers are more similar to beech stands. Combining pure beech and pure conifer stands at the landscape scale can increase landscape level biodiversity and conserve species assemblages of both stand types, while landscapes solely composed of stand scale tree species mixtures could lead to a biodiversity reduction of a combination of investigated groups of 7 up to 20%.

Variation of leaf angle distribution quantified by terrestrial LiDAR in natural European beech forest

Leaf inclination angle and leaf angle distribution (LAD) are important plant structural traits, influencing the flux of radiation, carbon and water. Although leaf angle distribution may vary spatially and temporally, its variation is often neglected in ecological models, due to difficulty in quantification.In this study, terrestrial LiDAR (TLS) was used to quantify the LAD variation in natural European beech (Fagus Sylvatica) forests. After extracting leaf points and reconstructing leaf surface, leaf inclination angle was calculated automatically. The mapping accuracy when discriminating between leaves and woody material was very high across all beech stands (overall accuracy = 87.59%). The calculation accuracy of leaf angles was evaluated using simulated point cloud and proved accurate generally (R2 = 0.88, p < 0.001; RMSE = 8.37°; nRMSE = 0.16). Then the mean (θmean), mode (θmode), and skewness of LAD were calculated to quantify LAD variation.Moderate variation of LAD was found in different successional status stands (θmean∈ [36.91°, 46.14°], θmode∈ [17°, 43°], skewness ∈ [0.07, 0.48]). Rather than the previously assumed spherical distribution or reported planophile distribution, here we find that LAD tended towards a uniform distribution in young and medium stands, and a planophile distribution in mature stands. A strong negative correlation was also found between plot θmean and plot median canopy height, making it possible to estimate plot specific LAD from canopy height data.Larger variation of LAD was found on different canopy layers (θmean∈ [33.64°, 52.97°], θmode∈ [14°, 64°], skewness ∈ [−0.30, 0.71]). Beech leaves grow more vertically in the top layer, while more obliquely or horizontally in the middle and bottom layer.LAD variation quantified by TLS can be used to improve leaf area index mapping and canopy photosynthesis modelling.

Ispitivanje prisustva u zemljištu, vijabilnosti i infektivnog potencijala azigospora entomopatogene gljive Entomophaga maimaiga

Entomophaga maimaiga is one of the best-known gypsy moth pathogens with increasing importance in the biological control aimed at reducing the population of this defoliator. The territory of the Republic of Serbia is a very favorable gypsy moth habitat, and the problems caused by its larvae during the periods of outbreaks are so great that they can lead to forest defoliation and forest health deterioration. In the Republic of Serbia, E. maimaiga was first recorded in 2011 (as a new species in the microflora of Serbia) during the gypsy moth outbreak (2009-2014), which was the last to date. In 2011, numerous dead caterpillars were found on and around trees in oak and beech stands of the Belgrade and Valjevo regions in Serbia. Subsequent laboratory analyses revealed that they contained azygospores and conidia of this fungus. The assisted introduction of E. maimaiga was carried out in Compartments 28 and 30 of the FMU Avala on Mt. Avala in 2011. It led to an epizootic in the following year and stopped the outbreak of the gypsy moth in the area. Since it has been seven years since the outbreak, we tested the viability and infectivity of E. maimaiga azygospores obtained from the soil samples from Avala Mountain where its assisted introduction was carried out. We used larvae from the laboratory gypsy moth population and applied the bioassay method. The results show that azygospores are present in the given soil samples, they are viable and their infectivity is conserved. It can be concluded that in the case of an outbreak of gypsy moth populations in the future, they will exhibit their entomopathogenic effect

Ertragskundliche Aspekte und Strukturdynamik der Buchen-Lichtwuchsdurchforstung

Effects of heavy selective thinnings in beech stands with regard to stand productivity and structural diversity Based on thinning trials in beech stands initiated in the early 1970s, the effects of selective thinnings in favour of 100 to 120 future crop trees were analysed with regard to volume productivity and the stands' structural diversity. The results show that these kinds of thinnings reduce volume productivity by approximately 6% compared to the maximum volume growth. The reduction in volume growth is mostly caused by the fact that the strongly released crop trees have reduced their height growth for the benefit of a lateral crown expansion, while basal area growth was not affected. Calculations indicate that silvicultural systems working with only 50 future crop trees per hectare may decrease the maximum volume production by about 12%. Furthermore, the results show that the intense crown releases caused by selection thinnings increase the horizontal and vertical diversity of beech stands, since the trees in the understorey profit from better light conditions. The indices calculated for diameter and height diversity of the selection thinning plots approach the values being typical for single tree selection forests (“Plenterwälder”). Already after three to four consecutive selection thinnings, the beech stands' diameter distributions displayed an exponentionally decreasing shape typical for single tree selection forests close to equilibrium. Growth simulations revealed that it might even be possible to directly transform beech stands by selection thinnings into single tree selection structures. However, presumably negative effects on timber quality to be expected under single tree selection structures should be considered as a critical aspect with regard to theoretically possible transformation.

REGENERATION OF FIR IN DIFFERENTLY STRUCTURED STANDS OF BEECH AND FIR FORESTS (WITH SPRUCE) ON BJELAŠNICA

UDK: 630*23:582.475(234.422 Bjelašnica) This document includes research in regeneration of fir in differently structured stands of beech and fir forests (with spruce) on mountain Bjelašnica near Sarajevo. Analysis of fir regeneration in differently structured stands was done by comparison of numbers of units of young fir, per growth category, and by total number of young fir at canopy density degree of 0.7 (0.60 – 0.79) and 0.9 (0.80 – 1.00), and by mixture ratio – share of fir (spruce) 0.7 (60 – 79 %) and 0.9 (80 – 100 %). Comparisons were done between virgin forest stands of beech and fir (with spruce) on ‘Ravnavala’, than, two-storied stand where we recorded transition of tree species (beech is dominant in upper growth, while fir is mainly dominant in young growth) on location ‘Medvjeđalokva’ and stands of typical uneven aged production forest of beech and fir (with spruce) in direct vicinity of virgin forest stand. Data gathering was done using total measurement method on permanent experimental plots of 1ha in virgin forest stand and two-storied stand on location ‘Medvjeđalokva’ and on circular plots in diameter of 12.62 m. Positions of circular experimental plots were determined by systematic sample in form of grid on intersections of Gauss-Krueger system, in intervals of 100 meters. Grid is laid in three transects of 27 plots each that is spread across forest compartments number: 111, 113, 114 and 115 of Management unit „Igman“, location ‘Ravnavala’. We have placed two experimental square plots of 1ha; one in virgin forest reservation ‘Ravnavala’ for preservation of assortment, status without human impact (compartment 106, MU „Igman“), and the other in management forest of this area “Medvjeđalokva” (compartment 117, MU „Igman”) for specific structure of assortment. Square 1ha plots were divided by grid of squares 10 x 10 m into 100 small plots.

Nitrogen Nutrition of European Beech Is Maintained at Sufficient Water Supply in Mixed Beech-Fir Stands

Research highlights: Interaction effects of coniferous on deciduous species have been investigated before the background of climate change. Background and objectives: The cultivation of European beech (Fagus sylvatica L.) in mixed stands has currently received attention, since the future performance of beech in mid-European forest monocultures in a changing climate is under debate. We investigated water relations and nitrogen (N) nutrition of beech in monocultures and mixed with silver-fir (Abies alba Mill.) in the Black Forest at different environmental conditions, and in the Croatian Velebit at the southern distribution limit of beech, over a seasonal course at sufficient water availability. Material and methods: Water relations were analyzed via δ13C signatures, as integrative measures of water supply assuming that photosynthesis processes were not impaired. N nutrition was characterized by N partitioning between soluble N fractions and structural N. Results: In the relatively wet year 2016, water relations of beech leaves, fir needles and roots differed by season, but generally not between beech monocultures and mixed cultivation. At all sites, previous and current year fir needles revealed significantly lower total N contents over the entire season than beech leaves. Fir fine roots exhibited higher or similar amounts of total N compared to needles. Correlation analysis revealed a strong relationship of leaf and root δ13C signatures with soil parameters at the mixed beech stands, but not at pure beech stands. While glutamine (Gln) uptake capacity of beech roots was strongly related to soil N in the monoculture beech stands, arginine (Arg) uptake capacities of beech roots were strongly related to soil N in mixed stands. Conclusions: Leaf N contents indicated a facilitative effect of silver-fir on beech on sites where soil total N concentrations where low, but an indication of competition effect where it was high. This improvement could be partially attributed to protein contents, but not to differences in uptake capacity of an individual N source. From these results it is concluded that despite similar performance of beech trees at the three field sites investigated, the association with silver-fir mediated interactive effects between species association, climate and soil parameters even at sufficient water supply.

Pre-commercial thinning in naturally regenerated stands of European beech (Fagus sylvaticaL.): effects of thinning pattern, stand density and pruning on tree growth and stem quality

Pre-commercial thinning in naturally regenerated stands of European beech is often expensive and must be justified by improved development of the remaining crop. Based on a field experiment established in two 14-year-old naturally regenerated beech stands in Denmark, we investigated some effects of pre-commercial thinning and pruning on future crop tree growth and stem quality. The treatments included (1) no thinning, (2) moderate to heavy strip thinning, with or without subsequent selective thinning, and (3) extremely heavy strip thinning in two perpendicular directions (checkerboard thinning), with or without subsequent selective thinning and with or without pruning. The resulting residual stand densities ranged from 10⁵ to only 200 ha⁻¹. Treatment effects were evaluated on one potential future crop tree for every 100 m². Potential future crop trees were selected 32 years after germination based on spatial distribution, growth potential and stem quality. Total crop tree height was unaffected by strip thinning, but reduced by checkerboard thinning. Stem diameter at 1.30 m above ground level increased with decreasing stand density but, for checkerboard thinning, was reduced by pruning. The lower live branch was located at a lower position with heavy strip thinning and with checkerboard thinning without pruning. The frequency of crop trees with a forked stem was largest with checkerboard thinning and these forks were located at a lower position. Stem tilt and stem bend (stem straightness) were essentially unaffected by thinning practice. However, pruned trees tilted less and had straighter stems. The initial formation of epicormic branches on crop trees was unrelated to thinning and pruning practice, but crop trees that had been pruned for these were less prone to subsequently develop epicormic branches. In summary, moderate to heavy pre-commercial thinning had no effect on stem quality, while extremely heavy thinning without pruning resulted in unacceptably low stem quality. The no-thinning option resulted in acceptable growth and stem quality of the crop trees and this remains a viable management alternative for young beech.

Long-Term Abandonment of Forest Management Has a Strong Impact on Tree Morphology and Wood Volume Allocation Pattern of European Beech (Fagus sylvatica L.)

The three-dimensional (3D) morphology of individual trees is critical for light interception, growth, stability and interactions with the local environment. Forest management intensity is a key driver of tree morphology, but how the long-term abandonment of silvicultural measures impacts trunk and crown morphological traits is not fully understood. Here, we take advantage of a long management intensity gradient combined with a high-resolution terrestrial laser scanning (TLS) approach to explore how management history affects the 3D structure of mature beech (Fagus sylvatica L.) trees. The management gradient ranged from long-term (&gt;50 years) and short-term (&gt;20 years) unmanaged to extensively and intensively managed beech stands. We determined 28 morphological traits and quantified the vertical distribution of wood volume along the trunk. We evaluated the differences in tree morphological traits between study stands using Tukey’s HSD test. Our results show that 93% of the investigated morphological traits differed significantly between the study stands. Significant differences, however, emerged most strongly in the stand where forest management had ceased &gt;50 years ago. Furthermore, we found that the vertical distribution of trunk wood volume was highly responsive between stands with different management intensity, leading to a 67% higher taper top height and 30% lower taper of beech trees growing in long-term unmanaged stands compared to those in short-term unmanaged or managed stands. These results have important implications for management intensity decisions. It is suggested that the economic value of individual beech trees from long-term unmanaged forests can be expected to be very high. This might also translate to beech forests that are extensively managed, but we found that a few decades of implementation of such a silvicultural system is not sufficient to cause significant differences when compared to intensively managed stands. Furthermore, TLS-based high-resolution analyses of trunk and crown traits play a crucial role in the ability to better understand or predict tree growth responses to the current drivers of global change.

Effect of Species Complementarity on Financial Return in Mixed Stands of European Beech and Scots Pine in Northern Spain

The research on mixed-species forestry has rapidly increased in recent decades because there is a growing interest in these types of stands for environmental reasons. Their positive influence on ecosystem biodiversity, stability and resilience, as well as their role in the new challenge brought up by the adaptation to global change, have been the object of many research works. However, the economic implications of mixed-species forest management have not deserved the same attention. The objective of this work is to study the effect of species interactions on productivity, and to economically assess this effect. This research is focused on the analysis of financial return and risk in even aged mixed stands of Pinus sylvestris and Fagus sylvatica in Northern Spain. Growth and yield projections for monospecific and mixed stands of Scots pine and European beech were made by means of a previous model developed from a set of the Spanish National Forest Inventory plots in the region of Navarre. Data from yield tables for both species were used. The effect of species proportion on total stand yield was assessed and transgressive overyielding was found for some mixing ratios. A data series on average stumpage price for both species in Spain over a 29-year period was compiled and the joint probability distribution of price data was used to generate 500 price scenarios. Different management alternatives based on species proportion and rotation age were considered and evaluated in terms of profitability and risk. Some management recommendations can be derived from the results obtained, which point at an optimum mixing ratio from 30% to 40% Scots pine and 70% to 60% European beech.

Mapping Forest Structure Using UAS inside Flight Capabilities.

We evaluated two unmanned aerial systems (UASs), namely the DJI Phantom 4 Pro and DJI Mavic Pro, for 3D forest structure mapping of the forest stand interior with the use of close-range photogrammetry techniques. Assisted flights were performed within two research plots established in mature pure Norway spruce (Picea abies (L.) H. Karst.) and European beech (Fagus sylvatica L.) forest stands. Geotagged images were used to produce georeferenced 3D point clouds representing tree stem surfaces. With a flight height of 8 m above the ground, the stems were precisely modeled up to a height of 10 m, which represents a considerably larger portion of the stem when compared with terrestrial close-range photogrammetry. Accuracy of the point clouds was evaluated by comparing field-measured tree diameters at breast height (DBH) with diameter estimates derived from the point cloud using four different fitting methods, including the bounding circle, convex hull, least squares circle, and least squares ellipse methods. The accuracy of DBH estimation varied with the UAS model and the diameter fitting method utilized. With the Phantom 4 Pro and the least squares ellipse method to estimate diameter, the mean error of diameter estimates was −1.17 cm (−3.14%) and 0.27 cm (0.69%) for spruce and beech stands, respectively.

Drought modifies tree competitiveness in an oak-beech temperate forest

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.

The interactions between tree-herb layer diversity and soil properties in the oriental beech (Fagus orientalis Lipsky) stands in Hyrcanian forest.

This study investigated the interactions between tree-herb layer diversity and some physico-chemical and eco-physiological characteristics of soil in natural oriental beech stand in western Guilan, Iran. The data were collected from nine research sites (50m × 50m) which were described as a gradient from pure oriental beech (Fagus orientalis Lipsky) stands to mixed stands with up to nine deciduous tree species (n= 27) in Hyrcanian forest. Herbaceous plants were sampled within ten 1m × 1m sub-plots in two plots of 400m2 which were installed randomly in each research site. Composite soil samples were taken at five positions in each research site. We found that the increase in tree diversity in mature oriental beech stands brought about an increase in microbial biomass carbon, soil carbon content, and the ratio of microbial biomass carbon to the organic carbon (Cmic/Corg). Increased soil organic carbon raised microbial biomass carbon through creating suitable environment for microorganisms. The findings also indicated that the ratio of microbial biomass carbon to the organic carbon (Cmic/Corg) increased as a quantitative indicator of soil carbon dynamics that finally benefits soil fertility of mixed oriental beech stands compared to pure oriental beech stands. The results showed that humus layer and litter thickness were negatively correlated with tree layer richness. Generally, it can be stated that maintaining a mixture of tree layer species in natural oriental beech stands results in an increase in richness and diversity values of herb plants as well as carbon content and microbial biomass carbon of soil.

Changes in Topsoil Properties after Centennial Scots Pine Afforestation in a European Beech Forest (NE Spain)

In this work, we studied the effects of centenary Scots pine (Pinus sylvestris L.) afforestation on topsoil properties conducted in a deforested area that was previously occupied by a natural European beech (Fagus sylvatica L.) forest. Organic layers and topsoil Ah mineral horizons (0–10 cm) were sampled in the Scots pine and European beech forests of Moncayo Natural Park (north-eastern Spain). The physical (stoniness, aggregate stability, and water repellency persistence and intensity), chemical (total organic C, total N, C/N, pH, and exchangeable Ca2+, Mg2+, Na+, K+, Al3+, and Fe3+), and physicochemical (cation exchange capacity) properties of soil were analyzed. Total organic C and N were also obtained for litter samples. The studied topsoils shared a series of common properties, such as a high stoniness and aggregate stability, very low base content, high cation exchange capacity, and extreme acidity. Soils that developed under the pinewood showed a higher soil water repellency intensity. However, K+ content was significantly higher in the beechwood soil. In both forest types, total organic C and N were similar in topsoil and litter (Hemimoder type), although C and N were pooled in different O-layers. Results indicate that pine afforestation in a deforested area was an adequate measure for soil protection since it did not show significant differences in the long term (ca. 100 years) compared to the nearby natural beech stands.