Beech Seedlings Research Articles

Changes in susceptibility of beech ( Fagus sylvatica) seedlings towards Phytophthora citricola under the influence of elevated atmospheric CO 2 and nitrogen fertilization

The growth-differentiation balance hypothesis (GDBH) predicts changes in susceptibility of plants against herbivores with changing resource availability. In the presented study we tested the validity of the GDBH for trees infected with a root pathogen. For this purpose Fagus sylvatica seedlings grown under different atmospheric CO 2- and soil nitrogen regimes were infected with the root pathogen Phytophthora citricola. High nitrogen supply increased total biomass of beech regardless of the CO 2-treatment, whereas elevated CO 2 enhanced biomass only in the high nitrogen treatment. The responses of beech under the different growing regimes to the Phytophthora root infection were not in line with the predictions of the GDBH. Enhanced susceptibility of beech against P. citricola was found in seedlings grown under elevated CO 2 and low nitrogen supply. Fifteen months after inoculation these plants were characterized by enhanced water use efficiency, by altered root–shoot ratios, and by enhanced specific root tip densities.

Effect of water availability on leaf water isotopic enrichment in beech seedlings shows limitations of current fractionation models

Current models of leaf water enrichment predict that the differences between isotopic enrichment of water at the site of evaporation (Delta(e)) and mean lamina leaf water enrichment (Delta(L)) depend on transpiration rates (E), modulated by the scaled effective length (L) of water isotope movement in the leaf. However, variations in leaf parameters in response to changing environmental conditions might cause changes in the water path and thus L. We measured the diel course of Delta(L) for (18)O and (2)H in beech seedlings under well-watered and water-limited conditions. We applied evaporative enrichment models of increasing complexity to predict Delta(e) and Delta(L), and estimated L from model fits. Water-limited plants showed moderate drought stress, with lower stomatal conductance, E and stem water potential than the control. Despite having double E, the divergence between Delta(e) and Delta(L) was lower in well-watered than in water-limited plants, and thus, L should have changed to counteract differences in E. Indeed, L was about threefold higher in water-limited plants, regardless of the models used. We conclude that L changes with plant water status far beyond the variations explained by water content and other measured variables, thus limiting the use of current evaporative models under changing environmental conditions.

Response of ectomycorrhizal community structure to gap opening in natural and managed temperate beech-dominated forests

Data on the impact of forest management practices on ectomycorrhizal community structure remains fragmentary and mainly originates from studies in northern coniferous forests. This study focuses on a comparison of ectomycorrhizal communities between canopy gaps and closed canopy areas within natural and managed beech-dominated forests at four locations in Europe. We used high resolution rDNA techniques to identify ectomycorrhiza-forming fungi and attempted to extract potential stand-, gap-, soil-, and selected environmentally derived variables by applying multivariate analysis and ordination for pooling of ecological groups of ectomycorrhiza. A significant reduction of diversity indices, ectomycorrhizal and fine root dynamics, in gaps in comparison with closed canopy stands indicates an effect of forest management practice and the high importance of maintaining and protecting natural forest areas for conservation of soil biodiversity and forest genetic resources. The ordination analysis revealed three groups of ectomycorrhiza correlated with changing environmental conditions. The litter and soil pH, number of beech seedlings, and presence of a gap had a pronounced effect on the ectomycorrhizal community. Combined analysis of ectomycorrhiza and environmental factors using correspondence analysis provided an insight into the ecological preferences of the analysed species and confirmed that environmental factors drive ectomycorrhizal community changes.

Natural regeneration of senescent even-aged beech (Fagus sylvatica L.) stands under the conditions of Central Bohemia

The natural regeneration of beech (<I>Fagus sylvatica</I> L.) was studied under various shelterwood densities and silvicultural treatments in senescent beech stands in Central Bohemia. Four permanent research plots differed in shelterwood density, crown cover and average relative light intensities. Between 2003 and 2007, seed production, seedling emergence and survival were followed. The mean density of beech seeds (full and empty) per 1 m<sup>2</sup> was estimated in another forest stand. In the autumn of 2003 the values were distinctly higher than those indicated for full mast years of beech. Despite high losses during the wintering of seeds, relatively low germination and high first-season mortality, the high density of 1-year-old beech seedlings indicates that these elements are not the factors which hinder natural regeneration. The thickness of the humus horizons influenced the density of young beech seedlings during all the three years. Ground vegetation was more frequent outside the crown projections of parent trees and increased with distance from the nearest tree. A reduction of crown cover to the level of 80% was an appropriate measure that assured the high survival of beech regeneration during the observed four-year period. Border cutting with the outer face oriented towards the east has to be considered as less suitable for beech regeneration than shelterwood systems and group selection harvesting.

Evaluation of different approaches for modelling individual tree seedling height growth

We compared different approaches for modelling height growth of individual beech seedlings in a controlled factorial experiment as well as in field data from naturally regenerated beech seedlings under the canopy of overstorey mature beech trees. Several competition indices, a model of overstorey fine root density, relative photosynthetically active radiation (PAR) values, and soil water values were used in these approaches. In the factorial experiment relative PAR and soil water content were measured and used for the prediction of seedlings height growth. In the field experiment this was done by using relative PAR and estimated fine root biomass as a surrogate for below ground resource availability. The latter approach was compared with a model where we used various competition indices representing the impact of overstorey trees on beech seedlings. Our results suggested that (1) models which combine resource based growth functions are suitable for the prediction of individual height growth of beech seedlings. Resource based models offer the opportunity to investigate on the independent multiplicative effect of irradiance and water supply and their interactions on tree seedlings. It was (2) shown that a combined model could be used not only to predict individual height growth of beech seedlings in a controlled experiment but also in the field. The model parameters of a pure light response function for the controlled factorial experiment are comparable to those obtained in the field study. The results showed (3) that the precision of predicting beech seedlings height growth is comparable between the model types tested within this study. Approximately half of the observed variation in seedlings relative height growth rate could be explained. However, the simple competition index approach provides no information on the environmental factors constraining tree seedlings growth; whereas the multiplicative combined models can be used to get a better understanding of growth dynamics in the field.

Temporal Occurrence of Dead Seedlings of Japanese Beech and Associated Fungi

Temporal Occurrence of Dead Seedlings of Japanese Beech and Associated Fungi

The effects of cutting regimes on natural regeneration in submountain beech forests: species diversity and abundance

The paper summarizes the results of 15-year natural regeneration for beech of five plots with different densities situated in the Western Carpathians Mts. Three of the plots were subjected to differently intensive shelterwood cuttings (plots L, M, H), one plot was clear-cut (CC), and one was left without intervention – as a control (C). The number of one-year-old seedlings decreased proportionally with increasing cutting intensity. The ANOVA results document a significant influence of cutting intensity on the abundance of both one-year-old and older seedlings. The abundance of beech seedlings was initially increasing with increasing cutting intensity, and, having reached the peak on plot M (medium intensity), there followed a decrease in the seedling abundance. Lower numbers of beech seedlings on plots subjected to less intensive cutting (C, L) result from less favourable growth conditions in comparison with plot M. On the other hand, cutting of higher intensity (H, CC) resulted in lower numbers of fructifying parent trees. The medium cut intervention having provided the plot M with stocking of 0.5 (50% of the stand) resulted in a lower number of seed resources (limiting factor for natural regeneration). However, for the other factor – seedling establishment (survival and recruitment) this plot (M) represents an ecological optimum in beech regeneration in the given conditions.

Summer drought impedes beech seedling performance more in a sub-Mediterranean forest understory than in small gaps

Refugia of mixed beech forest persist in the central mountains of the Iberian Peninsula at the south-western limit of European beech (Fagus sylvatica L.) distribution. The lack of beech regeneration is a concern in this region that has experienced reduced rainfall and higher temperatures over the past 30 years. Beech is considered especially susceptible to climate change because of its conservative shade-tolerant growth strategy; hence seedling responses to drought stress in gaps and in the understory are of particular interest. During the summer of 2007, a watering treatment raised the soil water content by up to 5% in gap and understory plots of beech seedlings in a mixed beech forest. Root-collar diameter was increased by our watering treatment in understory seedlings. Neither drought-avoidance through stomatal closure nor physiological drought-tolerance mechanisms were able to mitigate the effects of water stress in the understory seedlings, whereas osmotic adjustment enhanced the ability of the gap seedlings to tolerate water stress. Overall, high photosynthetic rates in the gaps, despite the photoinhibitory effects of high radiation, allowed gap seedlings to survive and grow better than the understory seedlings irrespective of water availability. Our results indicate that further intensification of summer drought, predicted for the Iberian Peninsula, will hinder the establishment of a beech seedling bank in the understory because of the conflicting seedling trait responses to simultaneously withstand water stress and to tolerate shade.

First Report of Phytophthora cactorum Associated With Beech Decline in Italy.

During 2006 and 2007, declining mature beech trees (Fagus sylvatica) were recorded in two stands in the Natural Park of Monti Cimini in central Italy. Symptoms included crown thinning and the presence of bleeding lesions on the main roots and lower stem. Incidence of decline was approximately 5%. Samples of necrotic bark tissue were collected, cut into 5 mm long segments, plated on PARPNH, and incubated at 20°C (1). Phytophthora isolates were obtained from necrotic tissues of 25% of the sampled declining trees. Colonies were rosaceous on potato dextrose agar (PDA) and homothallic. Papillate, ovoid-to-obpyriform, caducous sporangia (mean 38 × 26.2 μm) were produced in soil extract. Oospores were plerotic (mean diameter of 22 to 32 μm) and antheridia paragynous. Optimum growth temperature was 23 to 25°C, minimum 6 to 8°C and maximum 30 to 33°C. A portion of the internal transcribed spacer sequence has been deposited in the NCBI database (GenBank Accession No. FJ183724). A BLAST search of the NCBI database revealed Phytophthora cactorum, Accession No. EU194384, as the closest match with 100% sequence similarity. Pathogenicity of two isolates, PFE3 and IFB-CAC 38, collected from distressed beech trees was tested using a soil infestation test (10 beech seedlings per isolate and control) and an under the bark inoculation method (10 twigs per isolate and controls, wounded and noninoculated taken from a declining beech tree) (2). After 2 weeks at 20°C, twigs and seedlings inoculated with each isolate developed extensive necrotic lesions around the inoculation sites and the collar, respectively, and P. cactorum could be reisolated from all lesions. Controls showed no symptoms. P. cactorum is widespread in declining beech forests in central Europe (1). In Italy, P. cactorum occurs in soils of chestnut and oak forests and was isolated from collar and root lesions of declining walnut trees (3). To our knowledge, this is the first report of P. cactorum being associated with declining beech trees in Italy.

Biomass and nutrients allocation in pot cultured beech seedlings: influence of nitrogen fertilizer

Allocation of biomass and nutrient elements including Nitrogen to above and belowground compartments of beech seedlings (Fagus sylvatica L.) treated by labeled nitrogen fertilizer in the form of 15NH4 and 15NO3 were investigated at the end of two successive growing seasons. Pot cultured beech seedlings were grown at a green house on intact soil cores sampled from three adjacent stands including beech, Norway spruce and mixed beech-spruce cultures of Solling forest, Germany. Comparing biomass allocation and nutrients concentrations of the seedlings between the control and 15N-fertilized treatments revealed no significant effect of N fertilization on nutrients uptake by seedlings over the experiment. The form of N input influenced its movement into plant pools. It was demonstrated that beech seedlings take up nitrogen mainly in the form of nitrate, which is then reduced in the leaves, although the differences between the retention of NO3−-N and NH4+-N in plants were not statistically significant. Percent recoveries of 15N in trees were typically greater after 15NO3 than after 15NH4 additions. It was indicated that immobilization of 15N tracer in fine roots was a slower process comparing other plant compartments such as stem and coarse roots, but a powerful sink for N during the course of study.

Intensively fertilised seedlings of the beech (Fagus sylvaticaL.) for artificial regeneration of the spruce stands in the process of conversion

Artificial regeneration of autochthonous target tree species plays an important role in the process of conversion of forest stands. The European beech is one of the most suitable and most frequently used tree species in this process. Modern technologies of intensive methods of the cultivation of the European beech seedlings provide, among others, a possibility to increase the proportion of this tree species in reforestation more quickly. It is however necessary to test at what types of sites this planting material can be used. The health status and growth of intensively grown beech seedlings in the first years after planting were studied on 2 research plots. Proper intensive fertilisation of the beech seedlings affected positively both the initial height and growth. Even the slow-release fertiliser did not negatively influence the beech after planting. The health status of the beech is excellent after 4 years, the average height of plants with different fertilisation treatments having become equal. It is to conclude from the hitherto obtained results that a slow-release fertiliser in the substrate has a positive effect on the plant growth, and that different fertilisation variants did not cause any serious root deformations of the beech planting stock samples taken 4 years after planting. The impacts of prior nursery fertilisation upon the beech planted under the conditions of extreme sites are further investigated.

Growth and development of silver fir (Abies alba Mill.) regeneration and restoration of the species in the Karkonosze Mountains

The main task of the study was to investigate the growth conditions of silver fir natural regeneration in the Karkonosze Mts. (Poland). The paper examines the quantity and quality of light reaching the forest floor in stands of different canopies. The aim of the study was also to define the optimal site conditions for silver fir planting under stand canopy. Data on the natural regeneration and stand structure of each investigated stand were collected on circular plots in a grid of 15 × 15 m in 1999 and 2000. Biometric measurements of fir plants planted under various stand canopies were done three times (May 1999, autumn 2000 and 2001). It was found that the fir was not a dominant tree in all size classes from seedlings to saplings. Seedlings (both phases) of spruce, beech, sycamore and rowan occurred in all studied stands. The optimal conditions for fir development were found under larch canopy. That was demonstrated by the highest increment of height, diameter and offshoots. The worst conditions for fir growth were under beech and spruce canopy, which was indicated by the lowest diameter and height. The highest PAR was recorded under pine canopy, whereas the lowest one under beech canopy. Beech stand induced a lower R:FR ratio than the other tree species both on sunny and cloudy days. The highest R:FR ratio was found under the canopy of larch and pine stands.

Fine root growth of beech (Fagus sylvatica L.) seedlings during the first outplanting years in Western Bohemia (Czech Republic)

The study analyses the growth of beech seedling fine roots and their development in the first five years. The research plots were established in 1997–2003 in community forests of Starý Plzenec (Western Bohemia, Czech Republic). The data are based on annual reviews of beech samplings extracted from surveyed plots. The whole root volume as well as the fine root volume is significantly (on a 95% significance level) growing during the first years after outplanting and there is not any disruption of growth immediately after outplanting.

Ontogenetic variation in the relative influence of light and belowground resources on European beech seedling growth

We used height growth data from a 7-year field experiment with European beech (Fagus sylvatica L.) seedlings to test the hypothesis that the effects of above- and belowground resources on height growth depend on seedling size and age. Photosynthetically active radiation (PAR) was determined by hemispheric photography, and estimates of fine root biomass of the overstory trees were used as an inverse proportional surrogate for belowground resource availability. For recently germinated seedlings growing under the canopy of Picea abies (L.) Karst., belowground resource availability affected height growth more than light. During subsequent stages of seedling development, apart from initial seedling size, PAR increasingly determined seedling growth. Besides initial size, seedling age determined the effects of above- and belowground resources on seedling height growth. In seedlings identical in initial size but differing in age, the increase in height growth with increasing PAR was greater in older seedlings than in younger seedlings. The ranking of seedling height by year showed that small differences in size at the end of the first growing season resulted in continuously increasing differences during the following years. Mortality data indicated that the chances of a seedling surviving intraspecific competition was strongly determined by its dominance ranking within the first 5 years after establishment.

Beech regeneration of seed and root sucker origin: A comparison of morphology, growth, survival, and response to defoliation

American beech ( Fagus grandifolia Ehrh.) reproduces sexually, and vegetatively by root suckers. Although many studies have investigated its regeneration response, most did not account for differences that may exist between its two modes of reproduction. This study was performed in an old-growth Acer - Fagus forest in southern Quebec, where beech bark disease had only a minor effect at the time of the study. We compared the density and frequency of occurrence of beech seedlings and root suckers (height < 30 cm), as well as their morphology, growth, survival, and response to experimental defoliation. Root suckers accounted for ∼13% of beech regeneration at our site. Density and frequency of occurrence were greater for seedlings than suckers, but did not vary with light availability, which was low at our study site (mean: 2.9%). Seedlings and suckers did not differ in leaf characteristics, but several differences were observed in terms of plant morphology, growth, and survival. Root suckers showed more lateral growth than height growth, and had a lower leaf area index than seedlings. Root suckers had both a greater growth in height and diameter, and a higher survivorship than seedlings (height and diameter growth were, respectively, five and two times greater for suckers than seedlings, and 74% of suckers survived more than 1 year, compared to 52% for seedlings). Defoliation treatments, which included levels of defoliation of 50% and 100% (1) did not affect current-year extension growth of seedlings and suckers; (2) did not affect seedling diameter growth, but had a negative impact on sucker diameter growth; and (3) affected survivorship for both origins, but had a much greater negative impact on seedling survivorship (none of the completely defoliated seedlings survived over one year, while 55% of the suckers did). This study showed that several differences exist between small beech seedlings and root suckers in traits that are important determinants of a species’ competitive ability. We therefore expect that variation in the relative importance of root suckering among sites might have several community-level implications.

Growth and survivorship of American beech (Fagus grandifolia Ehrh.) seedlings in a northern hardwood forest following a mast event1

Despite the recognized importance of root sprout production in northern populations of American beech (Fagus grandifolia Ehrh.), further consideration of the relative role of regeneration from seed in this species appears warranted and timely. A careful examination of the literature revealed that seed- and sprouts-origin individuals co-occurred within all published study sites where the two were differentiated and that presence of a seedling bank may be the rule rather than the exception for American beech. We compared the effects of canopy gaps and root trenching on the growth and survival of a cohort of beech seedlings in Hubbard Brook Experimental Forest (HBEF) in northern New Hampshire, USA. Seedlings in gap plots became larger both above- and belowground. Foliar nitrogen concentrations were affected by both above- and belowground treatments and increased the most for seedlings in trenched gap plots. Seedling height and canopy treatment were important predictors of seedling survivorship with the highest survival in gap locations. The relationship between seedling height and survival was more complex. In the first two years, taller seedlings had a higher probability of dying, while after the second year taller seedlings were more likely to survive to be four-years old. The relatively high survivorship of seedlings at HBEF and their response to gap openings taken together with literature documentation of the long-term presence of seed-origin beech stems in the understory strongly suggest the presence of a beech seedling bank in this forest. This is one of a few manipulative studies on naturally regenerating American beech seedlings, and the first study to relate the likelihood of survival to seedling traits for this important species in the northern hardwood forest.

Growth and physiological responses of beech seedlings to long-term exposure of acid fog

Seven-year-old beech seedlings ( Fagus crenata) were exposed to simulated acid fog (SAF) at pH 3 or pH 5 (as control) prepared by adding a 2:1:1 mixture (molar ratio) of nitric acid, ammonium sulfate, and sodium chloride to ultrapure water from September 2004 to July 2006 in a mobile fog chamber. In comparison to control seedlings, seedlings from the pH 3 treatment displayed inferior plant height, stem diameter, number of leaves, and dry matter production, but greater leaf area. Furthermore, exposure to SAF induced early falling of leaves with a nearly two-times-greater normalized leaf number index than control. The starch levels in the stems of seedlings of the pH 3 treatment were much lower than those of control at the harvest. The acid fog-induced reduction of the starch accumulation is considered to occur mainly because of fewer leaves during the growth phase. Results of laboratory experiments demonstrate that the amount of base cations leached from the beech leaves increased with decreasing pH of SAF; the leaching amount of calcium ion from the beech was high relative to that of conifers such as fir and cedar. These results imply that chronic acid fog exposure suppresses growth and physiological activity of beech seedlings.

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

Summary During the last two decades, an increase of the frequency of naturally regenerated beech seedlings has been reported. This may be due to an increased masting. In this investigation in southern Sweden, mast year frequency, mast crop size and the relationships between mast year and climatic variables were studied. Our analysis shows that while the average mast year interval was 4 – 6 years from the end of the seventeenth century up to the 1960s, the mean interval has decreased to 2.5 years during the most recent 30 years, and there have been two consecutive mast years on two occasions during this later period. Mast years have often followed years in which the temperature in July and September was higher than the 30-year mean. However, there were signifi cant variations in the amounts of beechnuts produced between different mast years, and beechnut production increased with increasing site index. Climatic changes, especially increases in temperature, may have been responsible for the higher frequency of mast years, but increased atmospheric nitrogen deposition may also have been a contributory factor.

Ozone effects on visible foliar injury and growth of Fagus sylvatica and Viburnum lantana seedlings grown in monoculture or in mixture

Seedlings of Fagus sylvatica (beech) and Viburnum lantana (Viburnum) grown in monoculture and mixture were exposed to ambient and sub-ambient (charcoal-filtered) ozone concentrations in open-top chambers over the course of the 2003 and 2004 growing seasons at the WSL Lattecaldo open-top chamber facility in southern Switzerland. The aim of the study was to determine how the sensitivity to ozone in ambient air of these two species would differ between monocultures and mixtures in terms of growth and visible foliar injury development. Ambient ozone concentrations were consistently higher from the end of April to the middle of October in 2003 than in 2004 with seasonal peaks and means reaching 147 and 50 parts-per-billion (ppb) in 2003 compared to 124 and 40 ppb in 2004. Ambient AOT40 (ozone concentration accumulated over a threshold of 40 ppb during daylight hours with global radiation >50 W m −2) values from the end of April to the middle of October reached 48.3 and 26.8 parts-per-billon hours (ppm h) in 2003 and 2004, respectively. In general, Viburnum was a stronger competitor than beech over the course of this 2-year study. Seedlings of Viburnum benefited from interspecific competition in terms of both height growth and above-ground biomass accumulation at the expense of beech seedlings, which showed significantly reduced growth in the mixture as compared to the monoculture. However, as this was only the case for Viburnum growing in the charcoal-filtered treatment, ozone seemed to counteract the beneficial effect of interspecific competition on above-ground biomass accumulation in Viburnum, while at the same time decreasing relative biomass allocation to roots. Foliar sensitivity of the two species was also altered under interspecific competition suggesting that results based on seedlings of single species grown in monocultures may significantly over- or under-estimate foliar sensitivity to ozone. These results demonstrate that competition is an important factor affecting plant responses to ozone stress, but the direction and severity of these effects depend on the interacting species.

Gap regeneration patterns in relationship to light heterogeneity in two old-growth beech fir forest reserves in South East Europe

Summary Gap regeneration in two old-growth forest reserves in Slovenia (Rajhenavski Rog) and Croatia ( C orkova Uvala) was analysed in relation to within gap light heterogeneity. Both reserves were located in the Dinaric mountain range in south-central Europe and were dominated by beech ( Fagus sylvatica L.) – silver fi r ( Abies alba Mill.) forest communities with similar growing conditions. In total, the two largest gaps (700 – 2000 m 2 ) in each reserve were included in the study ( n = 4), plus a further four gaps in Rajhenavski Rog and three in C orkova Uvala (200 – 500 m 2 ). All the gaps were ~ 10 years old and originated from one or two successive events, mostly due to a combination of fungi attack and windthrow. Consequently, all gaps had complex geometry and were covered by a well-developed regeneration layer. Each gap was mapped, followed by establishment of a N – S oriented 5 × 5 m grid within and around the area of the canopy opening. At the grid intersections 773, 1.5 × 1.5 m plots were established. On each plot, the coverage of tree regeneration and ground vegetation, seedling density in different height classes and browsing damage were recorded. In addition, the total stretched length and last growing season increment of the leading stem was measured on selected seedlings in each plot. Relative diffuse and direct radiation were estimated using digital hemispherical photographs. All plots were classifi ed into four microsites according to direct and diffuse radiation levels, and microsites were tested for differences in regeneration height and density. While there was more woody regeneration and an almost fi vefold higher (6.2 vs 1.3 m − 2 ) average total regeneration density in Rajhenavski Rog, mainly due to a high (5.5 vs 0.6 m − 2 ) density of beech, there was more ground vegetation and a higher density of silver fi r seedlings in C orkova Uvala. The within-gap regeneration patterns proved to be similar in both forest reserves and showed that 1-year-old seedlings of beech and silver fi r and small beech seedlings preferably recruit on microsites under closed canopy or close to gap edges with lower levels of direct and diffuse radiation. There was no signifi cant difference in density of large-beech seedlings among the microsites, yet height and height increment were higher on microsites receiving the highest levels of direct and diffuse radiation. Within-gap heterogeneity in light conditions appears to signifi cantly