Despite a large body of studies investigating soil organic carbon (SOC) stocks and potential influencing factors, the impact of contrasting parent material, particularly in the subsoil, has received ...little attention. To reveal potential effects varying parent materials exert on SOC stocks, we investigated chemical (14C content and overall chemical composition via 13C NMR spectroscopy) and plant/microbial related parameters (root mass, amino sugars) of bulk soil and soil organic matter fractions from topsoil, subsoil, and rhizosphere soil at three European beech stands (Fagus sylvatica L.) only differing in parent material (Tertiary sand, Quaternary loess, and Tertiary basalt).
The results suggest that the clay fraction, its amount being largely dependent on the respective parent material, took a central role in shaping differences in SOC stocks among the investigated sites by affecting soil organic matter stabilization via organo-mineral association and aggregation. This fraction was particularly relevant in the subsoil, where it accounted for up to 80% of the bulk soil SOC stocks that decreased with decreasing amounts of the clay fraction (basalt > loess > sand site). Determining the soil's nutrient composition, parent material likely also indirectly affected SOC stocks by changing rhizosphere traits (such as fine root density or mortality) and by attracting root growth (and thus organic matter inputs) to subsoil with higher nutrient contents, where in situ root inputs in the form of rhizodeposits were likely the prime source of plant-derived SOC. However, root inputs also contributed in large part to topsoil SOC stocks and were associated with higher abundance of microbial compounds (amino sugars), whose relative importance increased with increasing soil depth.
Independent of soil depth and site, amino sugars and the amount of the clay fraction, combined with parameters related to the input of organic matter (root mass and amount of the particulate organic matter fraction) explained more than 90% of the variability in SOC stocks, indicating a key role of these measures in impacting SOC stocks. Because parent material directly or indirectly influenced these parameters, we demonstrate the necessity to consider differences in parent material when estimating and predicting SOC stocks.
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•The clay fraction, particularly in the subsoil, shaped differences in SOC stocks.•In the topsoil, the relevance of the clay fraction was attenuated by root inputs.•Microbial residues were constant or slightly increased with soil depth.•Amino sugars, root mass, clay and POM explained ∼90% of variation in SOC stocks.
Extreme weather events are increasing in frequency and intensity due to global climate change. We hypothesized that tree carbon reserves are crucial for resilience of beech, buffering the source-sink ...imbalance due to late frosts and summer droughts, and that different components of non-structural carbohydrates (NSCs) play specific roles in coping with stressful situations. To assess the compound effects on mature trees of two extreme weather events, first a late frost in spring 2016 and then a drought in summer 2017, we monitored the phenology, radial growth and the dynamics of starch and soluble sugars in a Mediterranean beech forest. A growth reduction of 85% was observed after the spring late frost, yet not after the drought event. We observed a strong impact of late frost on starch, which also affected its dynamic at the beginning of the subsequent vegetative season. In 2017, the increase of soluble sugars, associated with starch hydrolysis, played a crucial role in coping with the severe summer drought. NSCs helped to counteract the negative effects of both events, supporting plant survival and buffering source-sink imbalances under stressful conditions. Our findings indicate a strong trade-off between growth and NSC storage in trees. Overall, our results highlight the key role of NSCs on beech trees response to extreme weather events, confirming the resilience of this species to highly stressful events. These insights are useful for assessing how forests may respond to the potential impacts of climate change on ecosystem processes in the Mediterranean area.
Heat-induced weight loss (WL) and chemical and dimensional changes of small specimens of beech (
Fagus sylvatica L.), Scots pine (
Pinus sylvestris L.) and Norway spruce (
Picea abies L.) wood were ...examined after thermal modification in the 190–245 °C temperature range. Treated specimens exhibited reductions in their oven-dry weight in line with the severity of the treatment, with the effect of increasing the temperature of exposure being greater than extending the period of treatment. Wood polysaccharides were found to be distinctly more labile than the lignin constituent; the latter increased possibly as a result of repolymerisation reactions trapping some degradation products in the process. Specimens shrank in the transversal plane in a tangential to radial ratio of 2:1 regardless of the treatment regime, while their length increased marginally for WL < 10–12%. It is proposed that the thermal modification leaves the cell wall material in a permanent strained state.
•Structural and environmental patterns were analysed in beech forests in NW Spain.•Young beech forests are spatially clustered and become more regular as they mature.•Stands are overstocked, ...monospecific, with low plant richness and standing deadwood.•Complex relationships between environmental variables influence beech structure.•Increased diversity, stocking level and standing deadwood are expected under climate change.•The changes may indicate a shift in the beech-dominated forest to mixed stands.
The European beech (Fagus sylvatica L.) occurs in the Cantabrian Range (NW Spain), at the southwestern limit of the wide distribution area of the species in Europe, forming relatively unmanaged forests of high biodiversity value. In this study, we measured three-dimensional positions, diameter at breast height and height of all the trees present in 112 inventory plots established in beech-dominated forests in the north-western Cantabrian Range, in which hemispherical photographs were taken and a detailed floristic inventory was carried out. In addition, we measured 56 spatially continuous environmental variables in each plot to enable examination of environmental patterns in structural features and prediction of the effects of climate change. Forest structure was analyzed by using indices that evaluated spatial tree distribution, plant richness and tree species diversity, diversity of tree dimensions and vertical structure, stand density and average tree size, standing deadwood, canopy geometry and light regime. The stands exhibited a moderate clustered spatial arrangement at young stages, becoming more regular as they matured. The stands are generally monospecific, with low plant richness, never monostratified, with very close canopies, greater variation in diameter than in height and are usually overstocked. Only 25% of the stands included some standing dead trees. Random Forest models were used to describe structural features as a function of environmental variables. Although some of the models were complex and included many predictor variables, they revealed some interesting patterns. Thus, we found that spatial tree distribution was only related to lithostratigraphy, and tree species richness and vertical structure were related to isothermality. Shrub and herbaceous richness were related to soil pH and several thermal variables, while intermingling of tree species was mainly explained by soil-related variables. Climatic variables explained differences in tree diameter, whereas edaphic variables were more important for predicting differences in tree height. Stocking degree was mainly related to soil variables, while dominant height was related to thermal variables and standing dead wood to climatic variables. Projections under the moderate RCP 4.5 and pessimistic RCP 8.5 climate change scenarios predict a shift in beech forests towards increased shrub and plant richness and species diversity, but also increased stocking degree and standing deadwood basal area. These findings appear to confirm a drastic reduction in the suitable habitat for beech in the region (deterioration of future growth conditions), which could anticipate a loss of competitive advantage over other species and indicate a shift in this beech-dominated forest to more resilient mixed stands.
The release of biochar (BC) on forest soil is a strategy aimed at increasing carbon reserves and forest productivity. The effect of BC amendments on the decomposition of different quality litter is, ...however, poorly understood. With this study we investigate the effects of wood-derived BC applications on early decomposition in a European beech (Fagus sylvatica L.) forest through the burial of standard material, i.e. green tea and rooibos tea (high- and low-quality litter surrogates, respectively). Two main questions were addressed: 1) Do BC applications influence the decomposition of high- and low-quality standard litter and, if so, in what way? and 2) Does this effect (if measurable) depend on where the sample is placed with respect to the BC application layer? To test BC amendment effects, four application percentages were employed (0, 10, 20, and 100 %), after which standard litter mass loss was recorded. To investigate the effects of sample position, only three BC application percentages were used (0, 10 and 20 %), with teabags buried at three different depths - within the BC amended layer, between this layer and the unamended soil, and below the latter. Results show that early decomposition of high-quality standard litter was not influenced by BC applications, while a significant reduction in mass loss of low-quality standard litter was observed when the percentage of BC application was higher, specifically of litter within the 20 % and 100 % BC amended layers. Decomposition was also affected by sample position relative to the BC layer, exhibiting higher levels of mass loss when samples were placed within the BC amended layer. Overall, BC applications on beech forest soils not only seems to produce negligible effects on the early decomposition rate of high-quality standard litter, but such applications also seem to have the ability to reduce carbon loss following plant material degradation.
The objective of this study was to assess the chemical characteristics of cold-pressed beech nut oil. The nuts, gathered from the forest, comprised 25.35% water, 13.19% oil, and 19.40% protein. The ...predominant fatty acid was linoleic acid (40.5%), followed by oleic acid (35.0%) and gondoic acid (7.7%). All four tocopherols were present in the oil, with γ-tocopherol being the dominant form at 99.38 mg per 100 g of oil. The total sterol content was 2708.73 mg per kg of oil, with β-sitosterol constituting 80.5% of all sterols. The main characteristics of the oil included its relatively high tocopherol and gondoic acid content, a dominant oleic–linoleic fatty acid profile, and elevated levels of carotenoids.
Fagus sylvatica L. (Fagaceae), European beech, is one of the most important deciduous tree species in Central Europe and the most common broadleaved tree species in Germany. We investigated the ...leaves of six individual Fagus sylvatica trees growing in a beech forest in Kiel, Schleswig-Holstein, Germany, for seasonal variations in the content of phenolic natural products over three consecutive growing seasons. The investigated compound classes comprised hydroxycinnamic acid and flavonoid derivatives. The content of phenolic compounds showed clear trends in all years. A sharp decline in the total content of phenolic substances was observed from mid-April to the end of May. During the summer months, the content of phenolic compounds remained stable with only slight fluctuations until fall. The values for individual trees deviated more pronouncedly from one another in spring, but converged during the course of the growing period. These trends, despite differences in absolute values, were identical in three consecutive growing seasons (2016–2018). Our results contribute to a better understanding of the dynamics of plant natural products of deciduous trees in temperate climates caused by seasonal variations.
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•Phenolic natural products were monitored over three consecutive growing seasons.•Hydroxycinnamic acid and flavonoid derivatives were assessed separately.•After a sharp decline in spring, contents of phenolics compounds remained stable until fall.•Sharp decreases of phenolics in spring were observed in all three years.•The observed fluctuations are discussed in comparison to literature data.
•Oriental beech is a potential candidate for assisted migration in European forests.•Monitoring introduced (sub)species is expensive based on genetic analysis.•Leaf spectroscopy is an effective tool ...to discriminate Oriental and European beech.•Top canopy leaf lignin and nitrogen are traits most differing between subspecies.•The approach could be scaled to large forest areas using airborne remote sensing.
European beech (Fagus sylvatica L.) forests have recently experienced severe diebacks that are expected to increase in future. Oriental beech (Fagus sylvatica spp. orientalis (Lipsky) Greut. & Burd) is a potential candidate for assisted migration (AM) in European forests due to its greater genetic diversity and potentially higher drought resistance. Yet AM entails not only benefits, but also risks, and it is therefore important to monitor the progression of introduced (sub)species. Here, we demonstrate the potential of leaf spectroscopy to replace resource-intensive genetic analysis and field phenotyping for the discrimination and characterization of these two beech subspecies.
We studied two European beech forests, one in France and one in Switzerland, where Oriental beech from the Greater Caucasus was introduced over 100 years ago. During two summers (2021, 2022), we measured leaf spectral reflectance, leaf morphological and biochemical traits from genotyped adult trees. Subspecies prediction models were developed separately for top-of-canopy leaves (amenable to remote sensing) and bottom-of-canopy leaves (easier to harvest) using partial least squares discriminant analysis (PLS-DA) and different sets of spectral predictors.
Morphological, biochemical and spectra-derived leaf traits indicated that Oriental beech trees at the sites studied were characterized by higher lignin and nitrogen per unit leaf area than European beech, suggesting more protein-rich leaves on a per-area basis. The model based on top-of-canopy leaf reflectance spectra in the short-wave-infrared region (SWIR I: 1450–1750 nm) most accurately distinguished Oriental from European beech (BA = 0.86 ± 0.08, k = 0.72 ± 0.15), closely followed by models based on SWIR II, and on spectra-derived traits (BA ≥ 0.84, k ≥ 0.67).
This study provides a proof-of-principle for the development of spectroscopy-based approaches when monitoring introduced species, subspecies or provenances. Our findings hold promise for upscaling to large forest areas using airborne remote sensing.
•Forest characteristics from two sample plot inventories in a primeval beech forest.•Species composition is characterized by a pronounced dominance of beech of over 97%.•Main structural ...characteristics remained stable despite ample demographic change.•Volume lost between inventories was replaced by volume increment of surviving trees.•Ingrowing trees compensated for trees that died or decayed regarding tree density.
Quantitative estimates of change of primeval European beech (Fagus sylvatica L.) forests at the landscape scale over time are scarce due to both the few remnants of such forests and the absence of repeated sample plot inventories. This forest ecosystem is thought to be relatively stable over time, but it remains unclear what drivers contribute to this stability. Here, we studied temporal change in one of the largest primeval beech forests. Our analysis is based on two consecutive inventories on 238 permanent sample plots in the Uholka-Shyrokyi Luh forest in Transcarpathia, Ukraine, covering 102.8 km2. The inventories were carried out in 2010 and 2019.
This data allowed us to derive quantitative estimates for the main structural characteristics tree density, basal area and volume on a landscape scale and to characterize the demographic processes that shape this forest ecosystem. The structural characteristics tree density (2010: 441 N ha1, 2019: 458 N ha−1), basal area (2010: 35.9 m2 ha−1, 2019: 35.4 m2 ha−1), and standing volume (2010: 578 m3 ha−1, 2019: 584 m3 ha−1) of the living trees remained stable between the two inventories. The species composition, characterized by a pronounced dominance of beech, remained virtually unchanged as well, with 97.9% of the stems being beech trees in the first and 97.1% in the second inventory. In contrast, we observed a relatively high dynamic when looking at the demographic processes more closely. About 11% of the trees found alive in 2010 died until 2019, resulting in an annual mortality rate of 1.3%. Ingrowing trees compensated for trees that died or decayed regarding tree density, but only to a small extent regarding volume. The volume lost was largely compensated by the growth (8.0 m3 ha−1 year−1) of the surviving trees.
This work characterizes the change of forest attributes in a primeval beech forest at the landscape scale over a time of period of nine years and provides baseline indicators on the development and dynamics of primeval beech forests. It broadens our understanding about the contribution of the main demographic processes to the pronounced structural and compositional continuity of primeval beech forests.
•Space filling of European beech stands increased with management intensity.•Increased filling in the shaded crown resulted in higher productivity.•Measures of structural diversity were not sensitive ...to silvicultural activities.•No relationship between structural diversity indices and stand productivity.
Silvicultural success in achieving, among other management goals, maximum productivity strongly depends on knowledge of the relationship between stand density and the resulting growth response of a stand. However, there are still controversial discussions whether wood production can be enhanced by silvicultural thinning or reaches its maximum in unmanaged forest stands if time plays no role. Moreover there is no universal answer whether structural diversity promotes or reduces productivity. In the present study we applied terrestrial laser scanning (TLS) to investigate the relationship between three-dimensional space filling, forest management intensity, productivity and conventional measures of structural diversity. We examined 35 beech-dominated forest plots along a gradient of management intensity in three regions of Germany. We found that space filling in leaf-on condition increased with management intensity, particularly in the shaded crown. Increased space filling in the shaded crown due to tree removals also resulted in higher stand productivity. We conclude that an increased space filling in the shaded canopy of managed European beech stands is responsible for the compensation of production losses in the upper canopy due to thinning activities. Conventional measures of structural diversity were not sensitive to the applied silvicultural activities. We also found no relationship between structural diversity described by conventional measures and stand productivity.
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