Localization of chitinolytic activities in Fagus sylvatica mycorrhizas

 Localization of chitinolytic activities in Fagus sylvatica (beech) mycorrhizas was examined using a range of fluorogenic 4-methylumbelliferyl [4-MU-(GlcNAc)_1–4] substrates in order to distinguish between exochitinase, endochitinase and β-N–acetylglucosaminidase activities. The validity of the technique was confirmed using onion epidermis cells. In the beech mycorrhiza, endochitinase activity was not detectable above background fluorescence. Exochitinase activity was detected in the fungal sheath and the Hartig net. β-N–Acetylglucosaminidase activity was also mainly associated with the fungal sheath and Hartig net. Individual fungal hyphae extending from these structures also showed substantial β-N–acetylglucosaminidase activity. The cortical cell walls of the host in the Hartig net region also fluoresced brightly. The localization of β-N–acetylglucosaminidase activity was confirmed using a chromogenic histochemical reagent, 5-bromo-4-chloro-3-indolyl-N–acetyl-β-d-glucosaminide (X-GlcNAc). Accepted: 5 December 1995     

Characterization of microsatellite markers in Fagus sylvatica L. and Fagus orientalis Lipsky

Using an enrichment procedure, we cloned microsatellite repeats from European beech (Fagus sylvatica L.) and developed primers for the amplification of microsatellite markers. Six polymorphic loci were characterized which produced 3–21 alleles in 70 individuals from one Italian population, with an observed heterozygosity between 0.58 and 0.85. All six loci amplified fragments which were polymorphic in the closely related species, Fagus orientalis, also. Owing to their very high degree of variation, these markers should be very useful in gene flow studies of these species.     

Seasonal activity of non-specific acid and alkaline phosphatases in beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis>) leaves

The activities of acid and alkaline phosphatases along with phosphorus content in leaves of European beech (Fagus sylvatica L.) were studied for a period from April to October. The phosphorus content of beech leaves was highest in April, at the beginning of the vegetation period; from May to October it was twofold lower than in April. Acid phosphatase activity (per unit fresh weight) in leaves collected from the middle part of the crown decreased significantly in May and July compared to the enzyme activity in April. In both the low and middle parts of the crown, the acid phosphatase activity had a peak in August, and thereafter decreased in September and October. No correlations between acid phosphatase activity and phosphorus concentrations were found. Alkaline phosphatase activity was very low and in some cases near the detection limit during the whole observation period.     

Frost sensitivity of Fagus sylvatica and co-occurring deciduous tree species at exposed sites

In Central-European forest stands on southerly to south-westerly exposed slopes of hills with shallow soil, European beech (Fagus sylvatica L.) loses its predominance over other deciduous tree species such as oak (Quercus spp.) or whitebeam (Sorbus aria [L.] Cr.) due to limited availability of water. To test whether winter frost is an additional factor affecting the performance of beech at such exposed sites, we measured the minimum air temperatures between the sampling dates, and determined the frost sensitivity of F. sylvatica and of co-occurring tree species (Quercus petraea [Matt.] Liebl., Quercus pubescens Willd., Quercus robur L., S. aria [L.] Cr.) eight times during the winter months, from October to March, at two sites in the low mountain ranges of Central Germany, which share the same climatic, topographic and edaphic conditions. At each site, two localities (stand margins and the interior of the stands) were compared. The frost sensitivity was determined in twigs of the trees using the electrolyte leakage method.Throughout the winter, frost sensitivity of F. sylvatica was higher at the stand margin than in the forest interior at one of the sites. At the other one, the frost sensitivity of S. aria was lower at the stand margin than within the stand. No consistent differences between the localities were detected in the Quercus species. Generally, the differences in frost sensitivity between the localities were only small; this was probably due to the slight differences in the minimum air temperature. Thus, it appears unlikely that, in exposed localities, the performance of the investigated tree species is limited by winter frost. More consistent differences were found among species, with F. sylvatica proving to be the most frost-sensitive, and S. aria, the least frost-sensitive species, particularly at the stand margins. The role of frost for the occurrence and performance of F. sylvatica should be further studied at the limit of its distribution along the boundary to the semihumid areas of Central Europe.     

The influence of mycorrhizal colonization on growth in the greenhouse and on catechin, epicatechin and procyanidin in roots of Fagus sylvatica L.

 The influence of mycorrhizal colonization on beech (Fagus sylvatica L.) root tannin (procyanidin polymer) and its putative precursors catechin and epicatechin was investigated by high performance liquid chromatography. Seedlings planted in a sterile mixture of litter, compost, soil and sand were inoculated with brown beech ectomycorrhizas collected from a woodland (Lactarius subdulcis Bull ex Fr. ×  F. sylvatica). The seedlings were not fertilized during the first year of growth. Nonmycorrhizal control plants showed severe nutrient-deficiency symptoms on their leaves and grew less well than mycorrhizal plants. Mycorrhizal roots contained significantly less catechin, epicatechin and procyanidin polymer than nonmycorrhizal roots. In the second year of growth, the plants were fertilized and procyanidin formation in roots was investigated. None of the fertilized plants showed mineral-deficiency symptoms. Fertilized mycorrhizal roots consistently contained significantly less catechin and epicatechin than nonmycorrhizal controls, but procyanidin polymer content varied between replicate experiments. The possible function of catechin and epicatechin in ectomycorrhizal formation is discussed. Accepted: 11 July 1997     

Factors controlling micropropagation of mature Fagus sylvatica

The influence of several endogenous factors on micropropagation of mature elite trees of beech (Fagus sylvatica L.) has been investigated. February was the most beneficial month for explantation of dormant buds, since infection with endogenous bacteria was still low and in vitro growth of the plant material was the highest. The genotypes tested gave different results concerning their growth on various tissue culture media. Out of 51 mature grafted genotypes only seven could be established in vitro. Grafting of branches of mature stock plants on juvenile rootstocks resulted in a high increase of multiplication rate compared with corresponding mature material, which could not be subcultured in vitro. Apical buds, larger than 20 mm, from 1-year-old shoots proved to be the most suitable explant source. Plant material could be subcultured for several years and rooted successfully.Abbreviations BA benzyladenine - BTM Broad-leaved Tree Medium - GD Gresshoff Doy Medium - IBA indole-3-butyric acid - MS Murashige Skoog Medium - PVP polyvinylpyrrolidone - SH Schenk Hildebrandt Medium - WPM Woody Plant Medium     

Callus formation from mesophyll protoplasts of Fagus sylvatica L.

Viable protoplasts of European beech (Fagus sylvatica L.) were isolated from sterilized young leaves of juvenile (3–5 years) and mature (40 years) trees. Isolation in a saline solution containing 0.5% (w/v) Pectinol and 2% (w/v) Cellulase R-10 yielded 3×10⁷ protoplasts per gram fresh weight. Protoplast culture in modified Kao and Michayluk (1975) medium resulted in cell wall regeneration and sustained cell divisions with the formation of colonies and microcalli.Abbreviations KM Kao and Michayluk (1975) - LS Linsmaier and Skoog (1965) - MES 2(N-morpholino)-ethane-sulfonic acid - NAA 1-naphthalene acetic acid - PVP Polyvinylpyrrolidone - Tween 80 Polyoxy-ethylene-sorbitan-monooleate Dedicated to Landesforstmeister Prof. Dr. Hans-Joachim Fröhlich on the occasion of his 65th birthday.     

Is the spatial distribution of European beech (Fagus sylvatica L.) limited by its potential height growth?

Aim To improve our understanding of species range limits by studying how height growth, a trait related to plant survival, varies throughout the geographic range of Fagus sylvatica L. in France. Location The geographic range of beech in France, representing the western area of its European distribution, within which this species exhibits range distribution limits in both plains and mountainous areas. Methods A generalized linear regression model was used to link beech growth performance to environmental variables using data from 819 plots of the French National Forest Inventory (IFN) database. This model was applied to predict potential growth on 97,281 IFN plots covering the geographic range of beech in France. A kriging technique was used to interpolate estimated growth potential. Finally, the performance of plot‐based predictions of potential growth from the map (i.e. map quality) was evaluated against an independent data set. Results The beech growth performance model highlighted the major impact of climate on potential tree growth at a broad spatial scale. The relevant climatic factors were related mainly to spring cold, summer heat, and winter temperatures and rainfall. The study also revealed the predictive power of soil parameters, which explained a large proportion of the variation in potential beech growth (c. 30%). Analyses of height growth patterns near the boundary of the species range in France showed that the limit only partly coincides with the growth decline caused by climatic and soil factors. Along parts of the range limit, the predicted potential for growth was high, suggesting that in these areas the limit of the range could be explained by other factors, such as competition or constraints on reproduction. Main conclusions The spatial variation in the potential height growth of Fagus sylvatica can be explained by environmental factors and is partly correlated with its regional range limits. By identifying areas where growth potential constrains the geographic range of species, environmental growth models can help to improve our knowledge of the spatial drivers of species geographic range limits and shed light on their response to future environmental changes.     

Frequency of inversions affects senescence phenology of Acer pseudoplatanus and Fagus sylvatica

In mountainous regions, inversion situations with cold-air pools in the valleys occur frequently, especially in fall and winter. With the accumulation of inversion days, trees in lower elevations experience lower temperature sums than those in middle elevations. In a two-year observational study, deciduous trees, such as Acer pseudoplatanus and Fagus sylvatica, on altitudinal transects responded in their fall leaf senescence phenology. Phenological phases were advanced and senescence duration was shortened by the cold temperatures in the valley. This effect was more distinct for late phases than for early phases since they experienced more inversion days. The higher the inversion frequency, the stronger the signal was. Acer pseudoplatanus proved to be more sensitive to cold temperatures compared to Fagus sylvatica. We conclude that cold-air pools have a considerable impact on the vegetation period of deciduous trees. Considering this effect, trees in the mid hillside slopes gain advantages compared to lower elevations. Our findings will help to improve knowledge about ecological drivers and responses in mountainous forest ecosystems.     

Culturable microfungi inhibitory to Armillaria rhizomorph formation from Fagus sylvatica stump roots and soil

Culturable fungi from 28 fungal communities were isolated from soil, rhizosphere and thick (1 cm diam.) roots of living beech (Fagus sylvatica) trees and their stumps 1–3 years after felling. All fungi were morphotyped and identified morphologically. The frequency of fungi was 2–5× greater in stumps than in living trees. The diversity of fungi was similar in living trees and stumps. The majority of fungal species that occurred at greater frequency on/in roots of stumps reduced the growth of Armillaria ostoyae and to a smaller extent of A. gallica rhizomorphs in a soil substrate in vitro. It is suggested that the mycobiota of roots may constrain the colonization of F. sylvatica by A. ostoyae rather than by A. gallica. The significance of these findings in the epidemiology of Armillaria in beech forests is discussed.     

The effect of shoot architecture on hydraulic conductance in beech (Fagus sylvatica L.)

 Shoot hydraulic conductance was measured in beech (Fagus sylvatica L.) that had previously been exposed to high levels of nitrogen input. Whole-shoot hydraulic conductance, conductance per unit pressure gradient and leaf specific conductance were negatively correlated with the number of bud scars per unit length, a morphological parameter of tree decline. We propose a negative feedback mechanism by which stress induced alterations in shoot morphology can cause a lasting reduction of tree vigour. Received: 2 July 1997 / Accepted: 25 June 1998     

The greater seedling high-light tolerance of <Emphasis Type="Italic">Quercus robur</Emphasis> over <Emphasis Type="Italic">Fagus sylvatica </Emphasis>is linked to a greater physiological plasticity

The responses of Quercus robur (oak) and Fagus sylvatica (beech) seedlings to four different light environments (full, 50%, 40% and 15% sunlight) and to a rapid increase in irradiance were explored during the summer, after 2 years of growth in a forest nursery at Nancy (France). Significant differences between the two species were found for most variables. Phenotypic plasticity for morphological variables (root-shoot ratio, leaf size, leaf weight ratio) was higher in beech than in oak, while the reverse was true for anatomical (stomatal density, epidermis thickness, exchange surface area of the palisade parenchyma) and physiological (maximum photosynthetic rate, stomatal conductance, Rubisco activity) variables. Predawn photochemical efficiency (F_v/F_m) was higher in oak than in beech in all light environments except in 15% sunlight. F_v/F_m was significantly lower in 100% sunlight than in the other light environments in beech but not in oak. Maximum photosynthetic rates (A_max) increased with increasing light availability in the two species but they were always higher in oak than in beech. Oak exhibited higher Rubisco activity than beech in full sunlight. The transfer of shade-adapted seedlings to the open caused a decrease of F_v/F_m, which was larger for beech than for oak. Transferred oak but not beech plants recovered gradually to the control F_v/F_m values. The decreased chlorophyll content and the increased non-photochemical quenching observed in high-light beech seedlings were not enough to avoid photoinhibition. The results suggest that a greater tolerance of strong irradiance is linked to an enhanced physiological plasticity (variables related to photosynthesis), while shade tolerance relies on an enhanced plasticity in light-harvesting variables (crown morphology and chlorophyll content).     

Bacterial community structure and colonization patterns of Fagus sylvatica L. ectomycorrhizospheres as determined by fluorescence in situ hybridization and confocal laser scanning microscopy

) grown in natural forest soil in southern Germany was examined by fluorescence in situ hybridization (FISH) using fluorescent oligonucleotide probes, targeting phylogenetic relevant sequences of the 16S and 23S rRNA. Lactarius subdulcis, L. vellereus, L. rubrocinctus and Laccaria amethystina were found to be the prevalent fungi forming ectomycorrhizae with F. sylvatica. For FISH studies using confocal laser scanning microscopy, oligonucleotide probes labeled with carboxymethylindocyanine-succinimidyl ester allowed detection of associated bacteria, because the autofluorescence of ectomycorrhiza samples could be overcome in the infrared. Bacteria of the α-, β and γ-subclasses of the proteobacteriawere detected in high numbers on mantle surfaces, while members of other phylogenetically defined groups were found in smaller numbers. This contrasts with previous published results on the cultivation of mycorrhiza-associated bacteria. Hybridizing bacteria were also found within damaged cells of the hyphal mantle of L. rubrocinctus, as well as on emanating hyphae of L. amethystina. Using a newly developed extraction protocol for bacteria associated with ectomycorhizas, the two most common fungi on F. sylvatica, L. vellereus and L. subdulcis, were mostly associated with members of the α- and β-subclasses of the proteobacteria. The proportion of hybridizing bacteria varied between the two ectomycorrhizae, which were thus host to distinct populations of bacteria.     

Fine root biomass in a beech (Fagus sylvatica L.) stand on Paiko Mountain,NW Greece

Abstract

Fine roots represent a small proportion of total plant biomass however they represent the most dynamic component of the root systems of woody plants. There is limited information on the beech fine root production in Mediterranean ecosystems and especially in Greece. We measured live, dead and total fine root biomass (d<2 mm) (LFRB, DFRB and TFRB, respectively) over a growing season in a beech (Fagus sylvatica L.) stand on Paiko mountain, NW Greece, in order to contribute to the generally scarce knowledge of the fine root biomass of beech stands. It was found that TFRB and LFRB increased from May to July and then decreased. LFRB decreased with soil depth while there was no pattern at the change of DFRB with soil depth.     

Growth of Fagus sylvatica saplings in an old-growth forest as affected by soil and light conditions

Abstract. Studies were conducted on 41 five yr-old common beech (Fagus sylvatica) saplings collected in an old-growth beech wood (Fontainebleau forest, biological reserve of La Tillaie, France), under varying humus and light conditions, following gypsy moth (Lymantria dispar) caterpillar injuries. Aerial and subterranean parts of each sapling were described by means of 34 parameters and environmental conditions at the microsite, where each sapling was excavated, were characterized by 23 parameters. The development of beech saplings is strongly affected by microsite conditions. An increase in sapling size was associated with darkness of the A-horizon, typical of zones with poor mineralization of organic matter. Light conditions were more important in influencing the development of the root system than that of the aerial parts. Rooting depth was shallower and rate of mycorrhiza development by the black ascomycete Cenococcum geophilum was lower in microsites receiving incident light during the morning than in those never receiving incident light during this period. Results are discussed in the frame of survival of young beech individuals in varying environmental conditions, when submitted to competition by other vegetation and adverse climate conditions.     

Leaf litter decomposition in temperate deciduous forest stands with a decreasing fraction of beech (Fagus sylvatica)

We hypothesised that the decomposition rates of leaf litter will increase along a gradient of decreasing fraction of the European beech (Fagus sylvatica) and increasing tree species diversity in the generally beech-dominated Central European temperate deciduous forests due to an increase in litter quality. We studied the decomposition of leaf litter including its lignin fraction in monospecific (pure beech) stands and in stands with up to five tree genera (Acer spp., Carpinus betulus, Fagus sylvatica, Fraxinus excelsior, Tilia spp.) using a litterbag approach. Litter and lignin decomposition was more rapid in stand-representative litter from multispecific stands than in litter from pure beech stands. Except for beech litter, the decomposition rates of species-specific tree litter did not differ significantly among the stand types, but were most rapid in Fraxinus excelsior and slowest in beech in an interspecific comparison. Pairwise comparisons of the decomposition of beech litter with litter of the other tree species (except for Acer platanoides) revealed a “home field advantage” of up to 20% (more rapid litter decomposition in stands with a high fraction of its own species than in stands with a different tree species composition). Decomposition of stand-representative litter mixtures displayed additive characteristics, not significantly more rapid than predicted by the decomposition of litter from the individual tree species. Leaf litter decomposition rates were positively correlated with the initial N and Ca concentrations of the litter, and negatively with the initial C:N, C:P and lignin:N ratios. The results support our hypothesis that the overall decomposition rates are mainly influenced by the chemical composition of the individual litter species. Thus, the fraction of individual tree species in the species composition seems to be more important for the litter decomposition rates than tree species diversity itself.     

Effects of ozone and Phytophthora citricola on non-structural carbohydrates of European beech (Fagus sylvatica) saplings

A lysimeter study was performed to monitor long term effects of chronic ozone enrichment on saplings of European beech (Fagus sylvatica L). After 3 years of ozone exposure a root infection with Phytophthora citricola Swada was established in the fourth year to study the interaction between elevated ozone and the root infection on the carbon budget of beech saplings. By using quantitative PCR no differences in root infection with P. citricola were observed between the ozone treatments. In contrast to the first 3 years of ozone exposure, sucrose and starch concentrations in leaves were diminished in ozone treated plants in the fourth year. The root infection reduced sucrose concentrations in leaves. Starch reserves of the heterotrophic biomass were not affected by any treatments. Thus 4 years of ozone exposure and 1 year of P. citricola root infection had only limited effect on carbohydrate metabolism in beech saplings.     

Assessment of genetic relationships and population discrimination among Fagus sylvatica L. by RAPD

 We assessed the genetic relationships between members of the Fagaceae family by RAPDs in order to better ascertain the taxonomic status of a very particular population of Fagus sylvatica, the ‘tortuosa’ variety. Intra- and inter-population Nei and Li’s mean genetic distances were compared, and the genetic relationships between individuals were clarified on dendrograms by the Neighbor joining method. RAPD analysis was first conducted on three species from three genera, Quercus petraea, Castanea sativa, and Fagus sylvatica, in order to develop an efficient RAPD protocol. The variety level was then studied, and a general tendency of the individuals to cluster by variety was observed. Individuals also clustered by geographic locations, but the genetic distances between populations were not correlated to the distances between sites. Finally, we compared the common beech and ‘tortuosa’ varieties from two different locations, Verzy and Süntel. Both populations from one location were closer than the same variety from two sites. This last result is in agreement with those previously obtained with isozymes. Hypotheses concerning the origin of the ‘tortuosa’ variety are discussed. Received: 9 January 1998 / Accepted: 25 February 1998     

The effects of food availability and distance to protective cover on the winter foraging behaviour of tits (Aves: Parus)

To maximize fitness, many animals must trade off their need to forage efficiently against their need to avoid predators. We studied such a trade-off in four species of tits (Paridae) in a forest near Oxford, UK. During winter, tits form flocks which increase feeding efficiency and reduce predation risk. These flocks feed extensively on beech (Fagus sylvatica) seeds, the abundance of which may be critical for winter survival. Because these seeds drop to the ground, where birds are exposed to sparrowhawk (Accipiter nisus) attack, tits need to trade off their need to find seeds against the proximity to protective cover, provided by dense clusters of hawthorn (Crataegus spp.). The quality of the beech crop differs markedly between trees and years. During a year of abundant beechmast, most tits searched for seeds close to protective cover. This 'safety-first' strategy precluded visits to superabundant food patches if they were too far from protective cover. Among beech trees near to cover, tits tended to prefer those with high seed density. Tits benefited from foraging under trees with high seed density because this correlated significantly with seed mass per square metre and because mean search times decreased with increasing seed density. Finally, we show experimentally that great tits, Parus major, can discriminate between edible (viable) and inedible (empty) seeds.