Juvenile Beech Research Articles

Characteristics of beech mixed forest distributed at low elevations on Mt. Toishi, northern Kyushu, in the upper warm‐temperate zone of Japan

AbstractThe aim of this study was to clarify the structure and regeneration status of mixed beech (Fagus crenata) forest on Mt. Toishi in the Sangun mountain range in northern Kyushu, a relatively low‐latitude region in Japan, with emphasis on forests at lower elevations. We focused on a mixed beech forest at a low elevation of Mt. Toishi and compared the forest structure of the target stands, including tree species and size, with the forest structure near the peaks of Mt. Toishi and Mt. Sangun. Deciduous broad‐leaf trees were dominant near the peaks, while evergreen broad‐leaf trees dominated at lower elevations, whereas the relative dominance of beech trees was not significantly different. Near the peaks, the number of large‐diameter beech trees forming the canopy decreased, and small‐diameter trees were present. The proportion of small‐sized trees was lower in the low‐elevation forest area than in the forest area near the peak. Even at lower elevations, juvenile beech trees grew in limited areas on steep slopes along forest roads. These sites suggested that regeneration of beech populations is possible even at low elevation.

Leaf Phenological Responses of Juvenile Beech and Oak Provenances to Elevated Phosphorus

The few studies dealing with leaf phenological responses to elevated nutrients in forest trees have given ambiguous results, i.e., while some reported delayed leaf-out and autumn leaf senescence, others reported advanced leaf phenology caused by increased nutrition. This study aimed to determine the effects of experimentally increased phosphorus (+P treatment) on the leaf phenologies of two juvenile provenances of common beech and sessile oak. Other objectives were to determine whether there were interspecific differences as well as intraspecific variations. Saplings were excavated in two mixed beech–oak stands and transplanted into four wooden boxes filled with a commercial soil substrate. Phosphorus fertilizer was added to two of the boxes, while the remaining boxes served as controls. Both species responded to +P treatment with advanced autumn leaf senescence in the first year of the experiment. Leaf senescence in common beech began significantly earlier, while in both species, the process was accelerated compared to that in the control. In the second year, the leaf senescence response to +P treatment was even more pronounced in both species. The +P effect on leafing phenology was absent in both common beech provenances and in an oak provenance. However, the other oak provenance showed advanced leafing, indicating the existence of intraspecific differences.

Evidence of a Climate-Change-Induced Shift in European Beech Distribution: An Unequal Response in the Elevation, Temperature and Precipitation Gradients

Climate is a strong predictor of the geographic distribution of tree species, and thus climate change may trigger shifts in the distribution of a tree species and/or its demographic structure. In the study, we aim to comprehensively compare the distributions of four life stages of European beech (Fagus sylvatica) (i.e., regeneration, recruitment, young trees and mature trees) in forests in Slovenia, Central Europe, which are characterized by strong gradients of elevation (ELV), temperature (TEMP) and precipitation (PREC) to detect possible shifts in distribution and demography. Beech life stages were surveyed on 3366 plots. To depict disparities between ELV, TEMP and PREC distributions of beech life stages, we applied several non-parametric methods: basic statistical tests to study differences in medians, means, and 1st and 9th deciles; generalized additive models to study shifts in the optimum; and extreme value analysis to study shifts at the trailing and leading edges. A substantial shift in juvenile beech stages upward and toward colder sites was detected. However, the shift was not uniform along the distributions; the most significant shift was detected at the leading edge of ELV (+73 m) and TEMP (−2.6 °C), but surprisingly there was no beech movement identified at the trailing edge. The observed shift may be a result of the interplay between climate change, high spatial variability in microclimate, unexceptional droughts in the recent past, changes in forest use and possible limitations in the migration ability of beech and its adaptation capacity.

Plant Species Turnover on Forest Gaps after Natural Disturbances in the Dinaric Fir Beech Forests (Omphalodo-Fagetum sylvaticae)

We studied species turnover and changes of ecological conditions and plant strategies on forest gaps created by natural disturbances (sleet, windthrow). We studied five forest gaps and a control plot within in the Dinaric silver fir-beech forest in the southern part of Slovenia. Forest gaps varied in age and size. The total number of recorded species in gaps was 184, with the highest number (106) at the largest forest gap and with the 58 species at the control locality in a juvenile beech forest. Forest gaps were predominantly colonised mostly by species of understory, forest margins, and forest clearings. The species presented in all forest gaps are representatives of the understory of beech forests. Species colonising forest gaps prefer habitats with more sunlight, medium wet to dry soil, and are tolerant to high daily and seasonal temperature fluctuations. In gaps, the community of plant species has a competitive strategy, which is also complemented with a stress-tolerator strategy. We determined that a forest gap represents a significant habitat patch, especially for those plant species which were not present there before.

Growth Recovery and Phenological Responses of Juvenile Beech (Fagus sylvatica L.) Exposed to Spring Warming and Late Spring Frost

Global change increases the risk of extreme climatic events. The impact of extreme temperature may depend on the tree species and also on the provenance. Ten provenances of Fagus sylvatica L. were grown in a common garden environment in Belgium and subjected to different temperature treatments. Half of the one year old seedlings were submitted to a high thermal stress in the spring of the first year, and all plants were exposed to a late spring frost in the second year. The high-temperature treated plants displayed reduced growth in the first year, which was fully compensated (recovery with exact compensation) in the second year for radial growth and in the third year for height growth. Frost in the spring of the second year damaged part of the saplings and reduced their growth. The frost damaged plants regained the pre-stress growth rate one year later (recovery without compensation). The high temperature treatment in the first year and the frost damage in the second year clearly influenced the phenological responses in the year of the event and in the succeeding year. Little population differentiation was observed among the provenances for growth and for phenological responses. Yet, a southern provenance, a non-autochthonous provenance (original German provenance that was planted in Belgium about a century ago) and a more continental provenance flushed earlier than the local Atlantic provenances in the year of the frost event, resulting in more frost damage. Some caution should therefore be taken when translocating provenances as an anticipation of the predicted climate warming.

Growth and resource allocation of juvenile European beech and sycamore maple along light availability gradients in uneven-aged forests

The success of tree regeneration in forests strongly depends on light availability. In structured uneven-aged deciduous forests with continuous cover, radiation regimes in the understorey are typically characterized by low and heterogeneous light transmittance. The competitive ability of juvenile trees in these forests is therefore linked to their shade tolerance and expressed by different growth strategies. The related growth traits result in different morphological responses to light availability and shape recruitment dynamics. In the different light availability niches created by continuous-cover forestry, assessing tree growth patterns is crucially important towards silvicultural optimization, which aims to promote species diversity and the sustainable provision of forest ecosystem services. However, information on growth rates of small trees below the caliper limit of typical inventories or monitoring plots is relatively scarce. In an extensive field campaign, we sampled juvenile European beech (Fagus sylvatica L.) and sycamore maple (Acer pseudoplatanus L.) along light availability gradients and analyzed stem discs to quantify primary and secondary growth. We used linear mixed effects models to explain the annual increments of height, basal area and volume as well as allometric exponents. Beech growth rates were explained well by diffuse light availability and ontogeny. Models predicting sycamore growth were slightly less accurate, as indicated by a higher root mean square error. Compared to beech, light availability had a stronger influence on secondary growth of sycamore stems, and height increment decreased with tree age. Trajectories of height and diameter growth of the two species were different at low light availability, where sycamore invested more in height growth and thus was generally slender than beech. At light availability above 20%, similar growth trajectories but different allocation patterns were observed. Overall, we found markedly different growth strategies and different competitive abilities of beech and sycamore in small gaps in uneven-aged mixed deciduous forests. From a management perspective, sycamore should not be left suppressed in shaded conditions as it loses its height growth potential with increasing age. Tending measures may be needed for sycamore to maintain its stability and low height to diameter ratio, but not for juvenile beech, which benefits from positive effects of crowding on height growth.

Detecting differential viability selection between environments by analysis of compositional differentiation at different levels of genetic integration

Abstract Viability selection can be detected directly in an environment when the genotypes of the individuals at one ontogenetic stage (e.g. seeds) and the genotypes of the survivors at a later stage are both known, but genotypes at the earlier stage often cannot be determined. In this case, differential viability selection between environments can be detected as differences in the distributions of genetic types among survivors growing in different environments, provided that the survivors stem from random samples of seeds from the same base population (e.g. seed lot). Since common FST -outlier methods for detecting selected gene loci use only allele frequencies, selection that affects the higher hierarchical levels of genetic integration (single- or multi-locus genotypes) without changing allele frequencies is not noticed. A new method for detecting differential viability selection at any level of genetic integration enables discovery of elementary mechanisms of selection that older methods miss. It is based on two measures of compositional differentiation between environments. δSD measures qualita-tive differences between distributions of genetic types at any given integration level without regarding differences in their constituent alleles, while ΔSD measures quantitative differences between the same distributions by additionally considering the genic differences. The difference between these measures expresses the degree to which the patterns of gene association in the genotypes differ between environments. The P-values of all measures are estimated by permutation analysis under the assumption that survivors were randomly assigned to environments. Significance indicates the occurrence of differential viability selection at the loci. As a case study, a field study of viability in juvenile beech (Fagus sylvatica L.) for twelve enzyme loci is reanalyzed. It turns out that the significant differential selection for genotypes detected at three loci can be attributed to three combinations of selective effects: on alleles only (SKDH-A), mostly alleles but also association patterns (LAP-A); interaction of effects on alleles and association patterns that are non-significant when viewed separately (AAT-B).

Contrasting carbon allocation responses of juvenile European beech (Fagus sylvatica) and Norway spruce (Picea abies) to competition and ozone

Allocation of recent photoassimilates of juvenile beech and spruce in response to twice-ambient ozone (2 × O3) and plant competition (i.e. intra vs. inter-specific) was examined in a phytotron study. To this end, we employed continuous 13CO2/12CO2 labeling during late summer and pursued tracer kinetics in CO2 released from stems. In beech, allocation of recent photoassimilates to stems was significantly lowered under 2 × O3 and increased in spruce when grown in mixed culture. As total tree biomass was not yet affected by the treatments, C allocation reflected incipient tree responses providing the mechanistic basis for biomass partitioning as observed in longer experiments. Compartmental modeling characterized functional properties of substrate pools supplying respiratory C demand. Respiration of spruce appeared to be exclusively supplied by recent photoassimilates. In beech, older C, putatively located in stem parenchyma cells, was a major source of respiratory substrate, reflecting the fundamental anatomical disparity between angiosperm beech and gymnosperm spruce.

An approach to multiscale modelling with graph grammars.

Functional-structural plant models (FSPMs) simulate biological processes at different spatial scales. Methods exist for multiscale data representation and modification, but the advantages of using multiple scales in the dynamic aspects of FSPMs remain unclear. Results from multiscale models in various other areas of science that share fundamental modelling issues with FSPMs suggest that potential advantages do exist, and this study therefore aims to introduce an approach to multiscale modelling in FSPMs. A three-part graph data structure and grammar is revisited, and presented with a conceptual framework for multiscale modelling. The framework is used for identifying roles, categorizing and describing scale-to-scale interactions, thus allowing alternative approaches to model development as opposed to correlation-based modelling at a single scale. Reverse information flow (from macro- to micro-scale) is catered for in the framework. The methods are implemented within the programming language XL. Three example models are implemented using the proposed multiscale graph model and framework. The first illustrates the fundamental usage of the graph data structure and grammar, the second uses probabilistic modelling for organs at the fine scale in order to derive crown growth, and the third combines multiscale plant topology with ozone trends and metabolic network simulations in order to model juvenile beech stands under exposure to a toxic trace gas. The graph data structure supports data representation and grammar operations at multiple scales. The results demonstrate that multiscale modelling is a viable method in FSPM and an alternative to correlation-based modelling. Advantages and disadvantages of multiscale modelling are illustrated by comparisons with single-scale implementations, leading to motivations for further research in sensitivity analysis and run-time efficiency for these models.

Growth of juvenile beech (Fagus sylvatica L.) upon transplant into a wind-opened spruce stand of heterogeneous light and water conditions

Climate models predict increasing frequency and intensity of summer drought events for Central Europe. In a field experiment, we investigated the response of young beech (Fagus sylvatica L.) to extreme and repeated summer drought and the modulation of drought response patterns along the natural gradient of light availability at the study site. In autumn 2008, two-year-old, nursery derived beech – as used for forest conversion practices – was planted under a Norway spruce stand primarily opened through winter storm. Precipitation was manipulated in the growing seasons of 2009 through 2011, inducing a pronounced gradient of water availability. Individual drought-stress doses (DSD) and light doses (LD) were calculated for each beech sapling during the three growing seasons. Plant growth, CO2-assimilation rate and stomatal conductance were reduced with increasing drought stress, but facilitated by increasing light availability. Progressive acclimation to water and light limitation during the three years of the experiment led to a decreased drought and shade sensitivity of diameter growth. Water-use efficiency, root/shoot ratio and rooting depth, were increased with decreasing water availability. Mean fine root diameter and specific fine root length correlated positively with both DSD and LD. Proceeding low-light acclimation was indicated by progressively increasing specific leaf area and reduced leaf dark-respiration. Present results suggest that nursery-induced high-light acclimation of the beech saplings, exacerbated light limitation upon transplant and hence productivity decline under co-occurring water limitation.

Mode of competition for light and water amongst juvenile beech and spruce trees under ambient and elevated levels of O3 and CO2

Our study provides evidence that neither elevated CO 2 nor elevated O 3 alters the positive asymmetric competition for light and the symmetric competition for water among beech and spruce individuals grown in monoculture. We conclude that the mechanism of competition (i.e. symmetric/asymmetric) above (e.g shading or overtopping effect) and belowground (e.g. non-preemption or foraging) rather than abiotic treatments such as elevated CO 2 , O 3 and CO 2 /O 3 regimes, plays a dominant role for ensuring competitive success among tree saplings. Despite numerous studies conducted on plant responses to increasing CO2 and O3 concentrations, there is still a gap in understanding on how these gasses would affect the mode of competition (e.g., the ability by which larger and smaller plants capture resources) at the individual level of intra-specific beech and spruce saplings. Using empirical data and simulations from the plant-growth model PLATHO, we analyzed underlying mechanisms of competition and extrapolated effects beyond the time span of the experiment. We hypothesized that among juvenile beech and spruce trees planted in monoculture, +CO2 would diminish the positive asymmetric competition for light. Conversely, +O3 would enhance this outcome. In addition, we hypothesized that the symmetric mode of competition belowground for water would remain unchanged, irrespective of +CO2 and/or +O3 treatments. Our results showed that +CO2 and/or +O3 treatments did not alter the mode of competition aboveground for light. Conversely, we accepted our hypothesis that the mode of competition for water would remain unchanged under both treatments. Overall, we conclude that neither +CO2 nor +O3 alters the positive asymmetric competition for light and the symmetric competition for water among beech and spruce individuals grown in monoculture. We further conclude that competitive mechanism above (e.g., shading or overtopping effect) and belowground (e.g., non-preemption or foraging) rather than abiotic treatments, such as elevated CO2, O3 and CO2/O3 regimes, plays a dominant role for ensuring competitive success among tree saplings.

Evaluation of a ray-tracing canopy light model based on terrestrial laser scans

The local light regime within the tree canopy is crucial information for modeling water, carbon and nutrient cycling, and vegetation–atmosphere interactions. We tested the performance of a new model to simulate the light environment in the canopy of a juvenile beech stand under controlled light conditions. The canopy architecture was determined using a terrestrial laser scanner to derive a three-dimensional voxel representation. Depending on whether a voxel represents stem biomass, leaf biomass, or air, different attributes of light are assigned to the voxel. The model combines a representation of the canopy as three-dimensional cells (voxels) with a fast ray tracing algorithm that calculates the absorbed fraction of incoming photosynthetic active radiation (PAR). The simulated light regime of the stand was compared with measurements of the PAR regime inside the canopy (model efficiency Nash–Sutcliffe efficiency (NSE) = 0.88, root mean square error (RMSE) = 124 µmol m−2 s−1) and at the soil surface (NSE = 0.65, RMSE = 22 µmol m−2 s−1). The model needs two input parameters, the edge length of the voxels and the light attenuation coefficient of the voxels. The best simulation results were achieved at a voxel size of 0.03 m. For model calibration, only measurements of the light fraction that reaches the soil surface are needed. The good agreement of the simulated and the measured light regime together with the fast computation by the ray tracing algorithm suggest that the model is also applicable to simulate the light regime of natural forests under variable light conditions.

Stable isotope signatures reflect competitiveness between trees under changed CO 2/O 3 regimes

Here we synthesize key findings from a series of experiments to gain new insight on inter-plant competition between juvenile beech ( Fagus sylvatica) and spruce ( Picea abies) under the influence of increased O 3 and CO 2 concentrations. Competitiveness of plants was quantified and mechanistically interpreted as space-related resource investments and gains. Stable isotopes were addressed as temporal integrators of plant performance, such as photosynthesis and its relation to water use and nitrogen uptake. In the weaker competitor, beech, efficiency in space-related aboveground resource investment was decreased in competition with spruce and positively related to Δ 13C, as well as stomatal conductance, but negatively related to δ 18O. Likewise, our synthesis revealed that strong belowground competition for water in spruce was paralleled in this species by high N assimilation capacity. We suggest combining the time-integrative potential of stable isotopes with space-related investigations of competitiveness to accomplish mechanistic understanding of plant competition for resources.

Erratum to: Do chronic aboveground O3 exposure and belowground pathogen stress affect growth and belowground biomass partitioning of juvenile beech trees (Fagus sylvatica L.)?

Erratum to: Do chronic aboveground O3 exposure and belowground pathogen stress affect growth and belowground biomass partitioning of juvenile beech trees (Fagus sylvatica L.)?

Transcript responses in leaves of ozone-treated beech saplings seasons at an outdoor free air model fumigation site over two growing seasons

The still most abundant air pollutant, tropospheric ozone, leads to severe oxidative stress in plants. To investigate the ozone responsiveness of trees, we carried out a microarray analysis of beech saplings, grown around a free air lysimeter station in the years 2005 and 2006. The microarrays revealed ozone-responsive expressed sequence tags (ESTs), derived from a suppression subtractive hybridisation cDNA library. Chronic ozone exposure effects were investigated at different time points throughout the whole vegetation period in 2005 and 2006. Significantly regulated ESTs were calculated with R-packages. Different transcript patterns in both years could be related to weather conditions and consequential a different ozone uptake. Fewer transcriptome changes were found in 2005 compared to 2006. Induction of ESTs involved in cell structure, related to stress response and cell walls, signal transduction, as well as disease and defence in July and August indicated ozone-related stress responses in both years. An early response to ozone on primary metabolism, or, more precisely, on plant growth and photosynthesis, was observed in July and August particularly in the year 2006. This study demonstrated a clear transcriptional ozone response of juvenile beech, the most important deciduous tree in Central Europe, under free air conditions.

Analysing the role of soil properties, initial biomass and ozone on observed plant growth variability in a lysimeter study

This simulation study is based on a lysimeter experiment with juvenile beech trees (Fagus sylvatica L.) which were grown under ambient or doubled ambient atmospheric ozone concentrations. The aim of the study was to analyze the role of differences in soil properties, differences in initial biomass and ozone impacts on observed plant growth variability at the eight lysimeters of this experiment. For this purpose, we established a new simulation model based on the model system Expert-N by coupling soil water and nitrogen transport models with the plant growth model PLATHO, which was already tested and applied for juvenile beech. In order to parameterize the soil model, for all lysimeters soil hydraulic parameters as well as carbon and nitrogen stocks were measured. Simulation results reveal that the observed decreased growth rates under elevated ozone are due to ozone impacts on plant growth, whereas the high plant growth variability between lysimeters is to a major part the consequence of differences in soil hydraulic properties. Differences in initial biomass are of minor importance to explain plant growth variability in this experiment.

Do chronic aboveground O3 exposure and belowground pathogen stress affect growth and belowground biomass partitioning of juvenile beech trees (Fagus sylvatica L.)?

The impact of chronic free air ozone (O3) exposure and belowground pathogen stress on growth and total biomass development of young beech trees (Fagus sylvatica L.) was investigated in a lysimeter study. Plants were growing during four years under ambient or elevated atmospheric O3 concentrations. Additionally, in the last vegetation period the root rot pathogen Phytophthora citricola was introduced to study the interaction of ozone exposure and pathogen stress in the soil-plant system. A complete harvest at the end of the experiment enabled for the first time the assessment of fine and coarse root biomass of individual trees with a high vertical resolution down to two meter depth. Plant growth was significantly reduced by elevated ozone but not affected by P. citricola. Biomass partitioning between fine and coarse roots as well as vertical root distribution were significantly affected by both factors, whereas changes in root/shoot biomass ratio were not observed.

Initial differentiation of vertical soil organic matter distribution and composition under juvenile beech (Fagus sylvatica L.) trees

In a lysimeter experiment with juvenile beech trees (Fagus sylvatica L.) we studied the development of depth gradients of soil organic matter (SOM) composition and distribution after soil disturbance. The sampling scheme applied to the given soil layers (0–2 cm, 2–5 cm, 5–10 cm and 10–20 cm) was crucial to study the subtle reformation of SOM properties with depth in the artificially filled lysimeters. Due to the combination of physical SOM fractionation with the application of 15N-labelled beech litter and 13C-CPMAS NMR spectroscopy we were able to obtain a detailed view on vertical differentiation of SOM properties. Four years after soil disturbance a significant decrease of the mass of particulate OM (POM) with depth could be found. A clear depth distribution was also shown for carbon (C) and nitrogen (N) within the SOM fractions related to bulk soil. The mineral fractions <63 µm clearly dominated C storage (between 47 to 60% of bulk soil C) and N storage (between 68 to 86% of bulk soil N). A drastic increase in aliphatic C structures concomitant to decreasing O/N-alkyl C was detected with depth, increasing from free POM to occluded POM. Only a slight depth gradient was observed for 13C but a clear vertical incorporation of 15N from the applied labelled beech litter was demonstrated probably resulting from faunal and fungal incorporation. We clearly demonstrated a significant reformation of a SOM depth profile within a very short time of soil evolution. One important finding of this study is that especially in soils with reforming SOM depth gradients after land-use changes selective sampling of whole soil horizons can bias predictions of C and N dynamics as it overlooks a potential development of gradients of SOM properties on smaller scales.

Experimental setup of field lysimeters for studying effects of elevated ozone and below-ground pathogen infection on a plant-soil-system of juvenile beech (Fagus sylvatica L.)

An experiment, focusing on the effects of chronically enhanced O3 regimes on young beech (Fagus sylvatica) and on the microbial rhizosphere community structure, was conducted from November 2002 to August 2006 in eight field lysimeters at the Helmholtz Zentrum Munchen. The instrumentations of the lysimeters enabled the establishment of the water balance in the unsaturated zone and the assessment of the water uptake by plants. Further, the containment provided by the lysimeters made it possible to apply a root rot pathogen infection without contaminating the surrounding soil. A free-air fumigation system allowed to double the O3 concentration in the air above four lysimeters relative to the ambient air. To avoid damage of the leaves the maximum O3 concentration was limited to 150 nL L−1. For nearly 70% of the time the set-point concentration was reached within 10%. In the final harvest the whole soil column was retrieved and a nearly complete data-set of above-ground and below-ground parameters became available.

Plant and Soil System Responses to Ozone After 3 Years in a Lysimeter Study with Juvenile Beech (Fagus sylvatica L.)

A lysimeter study was performed to monitor effects of elevated ozone on juvenile trees of Fagus sylvatica L. as well as on the plant–soil system. During a fumigation period over almost three growing seasons, parameters related to plant growth, phenological development and physiology as well as soil functions were studied. The data analyses identified elevated ozone to delay leaf phenology at early and to accelerate it at late developmental stages, to reduce growth, some leaf nutrients (Ca, K) as well as some soluble phenolics (hydroxycinnamic acid derivatives, total flavonol glycosides). No or very weak ozone effects were found in mobile carbon pools of leaves (starch, sucrose), and other phenolic compounds (flavans). Altered gene expression related to stress and carbon cycling corresponded well with findings from leaf phenology and chemical composition analyses indicating earlier senescence and oxidative stress in leaves under elevated ozone. Conversely in the soil system, no effects of ozone were detected on soil enzyme activities, rates of litter degradation and lysimeter water balances. Despite the fact that the three reported years 2003–2005 were climatically very contrasting including a hot and dry as well as an extremely wet summer, and also mild as well as cold winters, the influence of ozone on a number of plant parameters is remarkably consistent, further underlining the phytotoxic potential of elevated tropospheric ozone levels.