Growth response of advanced planted European beech (Fagus sylvatica L.) after storm-caused loss of shelterwood

European Journal of Forest Research - Outcomes after an abrupt, storm-caused loss of spruce shelterwood (Picea abies L. Karst.) overstories on advanced planted beech (Fagus sylvatica L.) were...     

Genetic structure and variability of phenological forms in the European beech (Fagus sylvatica L.)

? Microsatellite markers were used to describe the genetic structure and variability of early, intermediate and late phenological forms of European beech (Fagus sylvatica L.). Two hundred and seventy individuals from three populations located in southern Poland were divided into three forms according to the phenological criterion — bud burst, and analyzed for allelic variation at five highly polymorphic microsatellite loci.

? Population differentiation was moderate and differed significantly among phenological forms. Average values of F _ST and R _ST decreased across phenological forms and amounted to F _ST values of 0.135, 0.110 and 0.108 and R _ST values of 0.365, 0.231 and 0.098 for early, intermediate and late forms of beech, respectively.

? Analysis of Molecular Variance (AMOVA) revealed different genetic structures characteristic of respective phenological forms of beech. The amount of within-population variability increased with the delay of the beginning of vegetation and amounted to 64%, 77% and 90% of total variability, depending on phenological form. A similar trend was found in average pairwise genetic distance between individuals belonging to a given phenological form (11.78, 11.85 and 12.22, from early to late forms).

? Our results demonstrate the importance of late spring frosts as a factor influencing the genetic structure of beech, and as a cause of the decrease in genetic variability as well as the increase in population differentiation proportional to the degree of phenological earliness.

     

Use of thermal imaging to determine leaf conductance along a canopy gradient in European beech (Fagus sylvatica)

Using an infrared camera, we measured the leaf temperature across different canopy positions of a 23-m-tall deciduous forest tree (Fagus sylvatica L.) including typical sun and shade leaves as well as intermediate leaf forms, which differed significantly in specific leaf area (SLA). We calculated a temperature index (I(G)) and a crop water stress index (CWSI) using the surface temperatures of wet and dry reference leaves. Additional indices were computed using air temperature plus 5 °C (I(G)?+?5, CWSI?+?5) as dry references. The minimum temperature of the wet leaf and the maximum temperature of the dry leaf proved to be most suitable as reference values. We correlated the temperature indices with leaf area-related conductance to water vapor (g(L)) using porometry at the leaf level and using xylem sap flow at the branch level. At the leaf and at the branch level, I(G) and CWSI were equally well suited as proxies of g(L), whereas the relationships of I(G)?+?5 and CWSI?+?5 with g(L) were only weak or even insignificant. At the leaf level, the correlations of I(G) and CWSI with g(L) were significant in all parts of the crown. The slopes of g(L) vs. I(G) and CWSI did not differ significantly among the crown parts; this indicates that they were not influenced by SLA or irradiance. At the branch level, close correlations (r?>?0.8) were found between temperature indices and g(L) across the crown. These results demonstrate that satisfactory relationships between temperature indices and g(L) can be established in tall trees even in those canopy parts that are exposed to relatively low levels of irradiance and exhibit relatively low values of g(L).     

Genetic structure of populations of beech (Fagus sylvatica L.) in Denmark

The genetic structure in Danish indigenous and introduced provenances of beech (Fagus sylvatica L.) is described. Ten stands are analysed based on variation revealed by seven enzyme systems. The present study reveals significant allele frequency differences between populations with a small absolute amount of genetic differentiation, with no pattern related to geographic distance. The genetic differentiation between indigenous populations measured by Wright's F _ST‐statistic does not deviate significantly from zero, and only 2.9% of the total genetic variation in the foreign populations was due to interpopulation differences, The allele frequencies in relatively small and isolated populations do not differ from the frequencies found in larger areas with beech forest. The low genetic differentiation of isozyme level between indigenous and foreign populations was opposed by significant differences in foliation performance measured on three pairs of neighbouring stands. Foliation performance in adjacent stands of indigenous and introduced beech indicates that quantitative characteristics must be considered separately from neutral variation at single loci.     

Radial distribution of carbohydrate reserves in the trunk of declining European beech trees (Fagus sylvatica L.)

Context

European beech (Fagus sylvatica L.) is considered threatened by anticipated climate change, but the physiological causes of potential beech decline or mortality remains poorly understood.

Aims

The purpose of the present study was to fuel debate about the assumption that carbohydrate depletion is involved in the decline of mature European beech.

Methods

The health status of beech trees from a severely declining stand was visually assessed by examining their crown condition. Content and radial distribution of non-structural carbohydrates (starch and soluble carbohydrate) were analyzed in the trunks and compared to those reported earlier in trunks of healthy beech trees.

Results and discussion

The distribution of carbohydrate in the beech trunks recorded here seemed affected by decline. We found a stronger radial decrease of starch content than those reported earlier for healthy beech trees. Carbohydrate reserves appear partially maintained in the outermost rings while starch depletion occurred in older wood rings in declining trees that may be able to mobilize carbohydrate reserves from older wood rings in response to successive climatic constraints.     

Identification of viruses from European beech (Fagus sylvatica L.) of declining forests in Northrhine-Westfalia (FRG)

Five different viruses isolated from degenerating European beech of different forest sites of West Germany could be identified as cherry leaf roll virus, brome mosaic virus, potex and potyviruses.     

Xylem sap composition of beech (Fagus sylvatica L.) trees: seasonal changes in the axial distribution of sulfur compounds

During different phases of the annual growth cycle, xylem sap was collected from trunk segments of adult beech (Fagus sylvatica L.) trees by the water displacement technique. Irrespective of the height of the trunk, both sulfate and reduced sulfur compounds were detected in the xylem sap throughout the year. Sulfate was the predominant sulfur compound in all samples analyzed. Its concentration in the xylem sap varied between 10 and 350 micro mol l(-1), with highest concentrations in April, shortly before bud break. In contrast to other tree species, cysteine and not glutathione was the predominant thiol transported in the xylem sap of beech trees. The cysteine concentration ranged between 0.1 and 1 micro mol l(-1). As observed for sulfate, maximum cysteine concentrations were found in April. Apparently, both sulfate and cysteine transport contribute to the sulfur supply of the developing leaves. Seasonal changes in the axial distribution of cysteine and sulfate differed, indicating differences in the source-sink relations of these sulfur compounds. High, but uniform, xylem sap sulfate concentrations in April may originate from balanced sulfate uptake by the roots, whereas high cysteine concentrations in April, increasing with increasing height of the trunk, may originate in part from protein breakdown in the trunk. Reversal of the axial distribution of xylem sap cysteine in late summer-early fall to higher concentrations in the lower part of the trunk than in the upper part of the trunk suggests that the upper part of the trunk becomes a sink for cysteine as a result of the synthesis of storage proteins at this time of the year.     

Natural regeneration of beech (Fagus sylvatica L.) with respect to canopy density,soil moisture and soil carbon content

The purpose of the present study is to model the regeneration success using quantifiable growth factors. The hypothesis is that the regeneration success can be predicted from a model that incorporates canopy and ground flora leaf area indexes (LAI), soil water content and soil carbon content. In April 1992, 10 plots (1 m²) were established in each of 22 Danish beech stands with natural regeneration originating from the 1989 seed fall. The regeneration success was investigated until autumn 1994. In each of the 220 plots the light conditions, soil water supply and soil carbon content were quantified. The survival was high during the study period. From spring 1992 to autumn 1993 the mean number of saplings decreased from 58 m⁻² to 54 m⁻². The sapling number was reduced by increased canopy density but it was neither influenced by water supply nor by soil carbon content. The height growth variation was evident. After the fifth growing season (autumn 1994) the height of the tallest sam3pling per plot ranged from 7 to 120 cm. Generally, an increased canopy opening increased the potential for and variance of height growth. Increased soil water content caused a significant increase in the growth of the saplings; whereas, a significant reduction in growth occurred with increased soil carbon content. The shading from the competing ground flora had no significant effect. However, the contribution to the total sum of squares from the quantitative variables of the relevant statistical models was only 3%–13%. Therefore, the models were unable to predict regeneration success satisfactorily and it was not possible to establish the causal effects underlying silvicultural treatments and site. It is concluded that the beech saplings probably were so well established at the beginning of the study that they had become tolerant to poor growing conditions, such as the drought in 1992. This indicates that the growing conditions during the early phases of seedling establishment may be crucial for the regeneration success. For silviculturists, these conclusions stress the importance of creating favourable growth conditions prior to the first growing season. Future research should examine the early phases of seedling establishment by quantifying growth factors in more detail than was done in the present study.     

Modelling natural drying of European beech (Fagus sylvatica L.) logs for energy based on meteorological data

A key factor for improving the whole fuel wood supply chain is moisture management. Moisture affects material quality, transport costs and revenue. The aim of this study was to develop a drying model for piled European beech (Fagus sylvatica L.) logs based on meteorological data, employing the continuous weighing approach. Two drying cycles with three piles altogether were conducted. In the first one (February to October 2013) the moisture content of the pile dropped from 43.5% to 22.5%, whereas in the second one (December 2013 to March 2015), the moisture content of the 2 piles dropped from 42.1% and 40.5% to 20.6% and 19.8%, respectively. Model performance (R² adj?=?0.41) was validated by applying the model developed from the second cycle's data on the first cycle's data. Model's mean deviation in moisture content from the observed curve was ?0.41%?±?0.72%. Economic benefits and environmental impact were highlighted. Calorific value increased from 2.65 to 3.57?kWh?kg^–1 from February to October 2013. Truckload volume utilization increased by 25.1% and transported calorific value by 48.0%. The number of truck trips for transportation was reduced from nine to seven.     

Biomass, basic density and biomass expansion factor functions for European beech (Fagus sylvatica L.) in Denmark

The objective of this study was to analyse the within-tree allocation of biomass and to develop biomass functions for above- and below-ground components of European beech in Denmark. Separate functions were developed for stem, branches, below-ground stump and root system, total above-ground biomass and total tree biomass. For each of these components or aggregate components, models were also developed for the average basic density of wood and bark. To enhance the versatility of the models, a function for estimating the biomass expansion factor (BEF) was also developed. The functions were based on 66 trees measured for total biomass. Model performance was evaluated based on 74 trees measured only for above-ground biomass. The trees were sampled in 18 different forest stands covering a wide range of tree sizes and stand treatments. Models were estimated using a linear mixed-effects procedure to account for within-stand correlations. The functions for biomass and BEFs included only diameter at breast height and total tree height for individual trees as predictor variables. Inclusion of additional variables reflecting site quality or stand density did not improve model performance. The functions for basic density included individual tree diameter, tree height and quadratic mean diameter as predictor variables, indicating an effect of stand density on the basic density of wood and bark.     

Transformation of even-aged European beech (Fagus sylvatica L.) to uneven-aged management under changing growth conditions caused by climate change

Transformation from even-aged to uneven-aged forest management is currently taking place throughout Europe. Climate change is, however, expected to change growth conditions—possibly quite radically. Using a deterministic approach, it was the objective of this study to investigate the influence of such changes on optimal transformation strategies for an even-aged stand of European Beech in Denmark. For a range of growth change scenarios, represented by changes in site index, optimal harvest policies were determined using a matrix modelling approach and a differential evolution algorithm. Transition probabilities were updated continuously based on stand level variables and the transition matrix was thus dynamic. With optimal transformation policies, stand development followed similar pathways during the transformation phase irrespective of climate change scenario. Optimal transformation policies were thus robust, suggesting that a good policy would work well under different outcomes of climate change, i.e., acting under erroneous assumptions about change would not lead to major economic loss. For the chosen case stand, the net present value (NPV) of the transformation phase (first 100 years) contributed 80–90 % of the total expectation value at a 2 % discount rate. To assess the robustness of the optimisation procedure and understand the nature of the response surface, 100 replications per scenario were carried out. Variation between replications peaked during the later stages of the transformation phase indicating several pathways for transformation, which were characterised by almost identical levels of profitability.     

DNA sequence variation and development of SNP markers in beech (Fagus sylvatica L.)

European beech (Fagus sylvatica L.) is one of the most important deciduous tree species in Central Europe. The potential of beech to adapt to climate change, higher temperatures, and less precipitation in the summer months is still unknown. Most studies in beech used microsatellite, AFLP (amplified fragment length polymorphism), or isozyme markers, which have only a restricted potential to analyze adaptation. Only few studies investigated genes probably involved in the adaptation to drought stress and bud phenology in beech. In this study, SNP (single nucleotide polymorphisms) markers were developed in order to analyze adaptation and their technical advantages compared to microsatellites and AFLPs were discussed. Partial sequences of ten candidate genes probably involved in drought stress and/or bud phenology were identified at the genomic level, and SNPs and indels (insertions/deletions) in coding and non-coding regions were analyzed. Plant material was sampled along a precipitation gradient in Germany. In total, 8,145?bp were sequenced and analyzed, 4,038?bp were located in exon and 4,107?bp in intron regions. 63 SNPs and 11 indels were detected, which are differently distributed over the studied gene regions. The nucleotide diversity ranged from 0 to 6.62 (π?×?10^?3) and is comparable to other tree species, whereas the mean nucleotide diversity (2.64) for F. sylvatica is comparatively low. These results will help to investigate the genetic basis of drought stress and bud burst and to conduct association mapping in natural populations. Furthermore, the detected SNPs can also be used for population genetic studies.     

A recent growth increase of European beech (Fagus sylvatica L.) at its Mediterranean distribution limit contradicts drought stress

Future changes in tree growth, associated with a warmer and drier climate, are predicted for many species and locations across the European Mediterranean Basin. However, quantification of the intensity and severity of related consequences for forest ecosystem functioning and productivity remains challenging. Species-specific distribution limits that are particularly sensitive to small changes in the ambient climate may provide an ideal test bed to assess the nature of past growth trends and extremes and their responsible controls. Here, we seek to understand how twentieth century climate change affected the growth of European beech (Fagus sylvatica L.) nearby its south-eastern distribution limit in Albania and Macedonia on the Balkan Peninsula. We sampled 93 living trees from undisturbed mixed forest stands at ~1,450 m a.s.l. and 29 timbers from nearby historical buildings. Application of different tree-ring detrending techniques allowed robust composite chronologies with varying degrees of high- to low-frequency variability to be developed back to 1648 ad. Comparison with local meteorological station measurements and continental grid-box climate indices revealed spatiotemporal instability in growth–climate response patterns. Nevertheless, year-to-year and decadal-long fluctuations in radial beech growth were significantly (P < 0.001) negatively correlated at ?0.61 with June–September temperature over the 1951–1995 period. This (inverse) relationship between increased beech growth and decreased summer temperature is somewhat indicative for the importance of plant-available soil moisture, which likely controls ring width formation near the species-specific south-eastern distribution limit. Significant positive correlations between beech growth and drought (scPDSI; r = 0.57) confirm metabolistic drought constraints. However, an unexpected late twentieth century growth increase not only contradicts the previously observed growth dependency to summer soil moisture, but also denies any putative drought-induced forest ecosystem suppression in this part of the Mediterranean Basin.     

Identification of moisture-induced stresses in cross-laminated wood panels from beech wood (Fagus sylvatica L.)

The crosswise bonding of the layers in laminated solid wood panels results in internal stresses when the humidity varies. The layers hinder one another as a result of the anisotropy of wood. The purpose of this study was to determine the internal stress state in free and constrained swelling. The expansion properties in the three panel directions were measured. Furthermore, the swelling of samples was constrained while the resulting forces were recorded. Hygroscopic warping experiments were carried out inducing a climate gradient within the panels. Afterwards the stresses were calculated from released deformations and non-destructive measurements of the Young’s modulus. The materials used were untreated and heat-treated beech wood, the latter modified in two levels. In addition to homogenously structured panels, treated top layers were combined with an untreated middle layer. Swelling, swelling pressure, warping and internal stresses considerably decreased from untreated to treated wood. If layers from treated and untreated material were combined, stresses and deformations increased as compared to the variants produced only from treated wood. It was concluded that the lower equilibrium moisture content of heat-treated beech wood improves its dimensional stability, which results in smaller deformation differences between the layers. Hence, the stresses were less distinctive.     

Soluble N compound profiles and concentrations in European beech (Fagus sylvatica L.) are influenced by local climate and thinning

We assessed seasonal changes of total soluble nonprotein nitrogen compounds (TSNN) in adult European beech trees (Fagus sylvatica, L.) growing under different local climate during the growing season immediately following a thinning treatment and 3 years later. In both years, samples of leaves, xylem sap and phloem exudates from beech trees growing in thinned and unthinned (control) stands on a dry, warm SW exposed and a cooler, moist NE exposed site were collected in May, July and September. In May of both years, asparagine (Asn) and glutamine (Gln) were most abundant in leaves and xylem, respectively, whereas arginine (Arg) dominated in the phloem. In July, TSNN concentrations decreased in all tissues and sites, but differences in water availability between aspects were reflected in TSNN concentrations. In September, differences in the increase of Arg concentration in the phloem were related to differences in the onset of senescence between treatments. Thinning treatment increased amino compound concentrations of beech tissues in July on both aspects, particularly at the NE thinned site. It is supposed that, the N balance of adult beech is favoured by both, the thinning treatments as well as the cool-moist climate prevailing at the NE aspect.     

Effects of weather conditions on mast year frequency in beech (Fagus sylvatica L.) in Sweden

During the last two decades, an increase of the frequency ofnaturally regenerated beech seedlings has been reported. Thismay be due to an increased masting. In this investigation insouthern Sweden, mast year frequency, mast crop size and therelationships between mast year and climatic variables werestudied. Our analysis shows that while the average mast yearinterval was 4–6 years from the end of the seventeenthcentury up to the 1960s, the mean interval has decreased to2.5 years during the most recent 30 years, and there have beentwo consecutive mast years on two occasions during this laterperiod. Mast years have often followed years in which the temperaturein July and September was higher than the 30-year mean. However,there were significant variations in the amounts of beechnutsproduced between different mast years, and beechnut productionincreased with increasing site index. Climatic changes, especiallyincreases in temperature, may have been responsible for thehigher frequency of mast years, but increased atmospheric nitrogendeposition may also have been a contributory factor.     

Bud dormancy in beech (Fagus sylvatica L.). Effect of chilling and photoperiod on dormancy release of beech seedlings

Two-year-old Fagus sylvatica L. seedlings were subjected to natural winter chilling or were overwintered in a heated greenhouse. Plants were then grown in controlled environment chambers with photoperiods of 9 or 13 h. Renewal of bud growth was found to be mainly determined by winter chilling. There was a slight interaction between chilling and photoperiod. Sprouting of apical buds took two to three times as long in unchilled plants as in chilled plants. Shoot elongation was influenced by chilling and was also greater in the 13-h photoperiod than in the 9-h photoperiod, but this may have been due at least in part to the higher irradiance. Chilling resulted in rapid dormancy loss and changed the growth pattern from basitonal to acrotonal.     

Effects of drought and canopy ozone exposure on antioxidants in fine roots of mature European beech (Fagus sylvatica)

We quantified ascorbate, glutathione and alpha-tocopherol in fine roots of mature Fagus sylvatica L. under free-air canopy ozone (O(3)) exposure (twice ambient O(3) concentration, 2x[O(3)]) during two growing seasons that differed in the extent of summer drought (exceptional drought year 2003, average year 2004). This design allowed us to test whether O(3) exposure or drought, or both, affected root antioxidants during the growing season. In both years, root ascorbate and alpha-tocopherol showed a similar relationship with volumetric soil water content (SWC): ascorbate concentrations on a root dry mass basis increased from about 6 to 12 micromol g(-1) when SWC dropped from 25 to 20%, and a-tocopherol increased from 100 to 150 nmol g(-1) at SWC values below 20%. Root glutathione showed no relationship with SWC or differences between the dry and the average year, but it was significantly and consistently diminished by 2x[O(3)]. Our results were inconclusive as to whether shoot-root translocation of glutathione or glutathione production in the roots was diminished. Phloem glutathione concentrations in the canopy remained constant, but reduced transport velocity in the phloem and, as a consequence, reduced mass flow of glutathione cannot be ruled out.     

Ring width and element concentrations in beech (Fagus sylvatica L.) from a periurban forest in central Belgium

The Forêt de Soignes is a beech high forest located near Brussels (Belgium), established on a strongly acidic soil and subjected to atmospheric pollution and recreational pressure. We investigated variations in ring width and mineral element concentrations (N, P, K, Ca, Mg, Mn, Al) over the last 95 years in five 135-year-old trees, variations in ring width in four 40-year-old trees and tested associations with climatic parameters. Growth curves showed a striking increase in mean sensitivity in the last 20 years in the old trees but not in the young ones, starting with the 1976 summer drought. Mean sensitivity is a statistical measure of the mean relative variability between adjacent ring widths within a tree, which is correlated to susceptibility to climatic stress (Fritts, H.C., 1976. Tree Rings and Climate, Academic Press, London, 567pp). May rainfall and, to a lesser extent, soil water recharge (i.e. pooled rainfall from October to May) correlated significantly with ring width. However, two of the five growth depressions in the last 20 years could not readily be accounted for by adverse climatic conditions. Element concentration profiles were suggestive of a decrease in the availability of Mn, Mg and Ca, but no trend of increasing N was obvious. The possible causes of the recent increase in sensitivity of old beech trees are discussed in terms of interactions between ageing and extreme climatic events, aggravated by soil compaction due to logging traffic.