Towards an understanding of the Holocene distribution of Fagus sylvatica L.

Aim Understanding the driving forces and mechanisms of changes in past plant distribution and abundance will help assess the biological consequences of future climate change scenarios. The aim of this paper is to investigate whether modelled patterns of climate parameters 6000 years ago can account for the European distribution of Fagus sylvatica at that time. Consideration is also given to the role of non‐climatic parameters as driving forces of the Holocene spread and population expansion of F. sylvatica. Location Europe. Methods European distributions were simulated using a physiologically‐based bioclimatic model (STASH) driven by three different atmospheric general circulation model (AGCM) outputs for 6000 years ago. Results The three simulations generally showed F. sylvatica to have potentially been as widespread 6000 years ago as it is today, which gives a profound mismatch with pollen‐based reconstructions of the F. sylvatica distribution at that time. The results indicate that drier conditions during the growing season 6000 years ago could have caused a restriction of the range in the south. Poorer growth conditions with consequently reduced competitive ability were modelled for large parts of France. Main conclusions Consideration of the entire European range of F. sylvatica showed that no single driving force could account for the observed distributional limits 6000 years ago, or the pattern of spread during the Holocene. Climatic factors, particularly drought during the growing season, are the likely major determinants of the potential range. Climatic factors are regionally moderated by competition, disturbance effects and the intrinsically slow rate of population increase of F. sylvatica. Dynamic vegetation modelling is needed to account for potentially important competitive interactions and their relationship with changing climate. We identify uncertainties in the climate and pollen data, as well as the bioclimatic model, which suggest that the current study does not identify whether or not climate determined the distribution of F. sylvatica 6000 years ago. Pollen data are better suited for comparison with relative abundance gradients rather than absolute distributional limits. These uncertainties from a study of the past, where we have information about plant distribution and abundance, argue for extreme caution in making forecasts for the future using equilibrium models.     

Storage and remobilisation of sulphur in beech trees (Fagus sylvatica)

Three-year-old beech trees were fed ³⁵S-sulphate in August 1993 via a flap in a mature leaf of an upper branch. Harvest of beech trees was performed 24 h after feeding ³⁵S-sulphate, before leaf senescence, after leaf abscission, in early winter (January 1994). in late winter (March 1994). before bud break and after bud break. Twenty-four h after feeding ³⁵S-sulphate, 0.7 ± 0.5% of the ³⁵S-radioactivity taken up was exported out of the fed leaf. When trees were analysed 2 months later, i.e., before leaf senescence, this value had increased to 22 ± 7%. The exported ³⁵S-radioactivity was located in the branch containing the fed leaf (2.8 ± 13%). in basipetal parts of the trunk (41 ± 77%) and in the main rool (21 ± 6%). Leaves and apical parts of the trunk were no sink organs for the exported sulphur. Along the tree axis the main proportion of the radiolabel was located in the wood, predominantly in the acid soluble fraction. In the bark the greater portion of the radiolabel was found in the acid insoluble fraction. In both tissues the bulk of the ³⁵S of the soluble fraction was sulphate together with small amounts of glutathione. This pattern did not change until bud break. After bud break, basipetal parts of the trunk lost part of its ³⁵S-radioactivity. Of the ³⁵S-radioactivity which had been exported out of the fed leaf during the previous autumn, 16 ± 2% remained in the trunk, whereas 47 ± 7% of the ³⁵S was found in branches, mainly in the newly developed leaves. The present results show that sulphur, mainly in the form of sulphate, is stored along the tree axis in both bark and wood of beech trees and is re-mobilised during leaf development in spring.     

Plant-mediated nitrous oxide emissions from beech (Fagus sylvatica) leaves

Nitrous oxide (N2O) emission estimates from forest ecosystems are based currently on emission measurements using soil enclosures. Such enclosures exclude emissions via tall plants and trees and may therefore underestimate the whole-ecosystem N2O emissions. Here, we measured plant-mediated N2O emissions from the leaves of potted beech (Fagus sylvatica) seedlings after fertilizing the soil with 15N-labelled ammonium nitrate (15NH4(15)NO3), and after exposing the roots to elevated concentrations of N2O. Ammonium nitrate fertilization induced N2O + 15N2O emissions from beech leaves. Likewise, the foliage emitted N2O after beech roots were exposed to elevated concentrations of N2O. The average N2O emissions from the fertilization and the root exposure experiments were 0.4 and 2.0 microg N m(-2) leaf area h(-1), respectively. Higher than ambient atmospheric concentrations of N2O in the leaves of the forest trees indicate a potential for canopy N2O emissions in the forest. Our experiments demonstrate the existence of a previously overlooked pathway of N2O to the atmosphere in forest ecosystems, and bring about a need to investigate the magnitude of this phenomenon at larger scales.     

Competition for nitrogen sources between European beech (Fagus sylvatica) and sycamore maple (Acer pseudoplatanus) seedlings

To investigate the short‐term consequences of direct competition between beech and sycamore maple on root N uptake and N composition, mycorrhizal seedlings of both tree species were incubated for 4 days (i.e. beech only, sycamore maple only or both together) in an artificial nutrient solution with low N availability. On the fourth day, N uptake experiments were conducted to study the effects of competition on inorganic and organic N uptake. For this purpose, multiple N sources were applied with a single label. Furthermore, fine roots were sampled and analysed for total amino acids, soluble protein, total nitrogen, nitrate and ammonium content. Our results clearly show that both tree species were able to use inorganic and organic N sources. Uptake of inorganic and organic N by beech roots was negatively affected in the presence of the competing tree species. In contrast, the presence of beech stimulated inorganic N uptake by sycamore maple roots. Both the negative effect of sycamore maple on N uptake of beech and the positive effect of beech on N uptake of sycamore maple led to an increase in root soluble protein in beech, despite an overall decrease in total N concentration. Thus, beech compensated for the negative effects of the tree competitor on N uptake by incorporating less N into structural N components, but otherwise exhibited the same strategy as the competitor, namely, enhancing soluble protein levels in roots when grown under competition. It is speculated that enhanced enzyme activities of so far unknown nature are required in beech as a defence response to inter‐specific competition.     

Genetic variation of European beech (Fagus sylvatica L.) along an altitudinal transect at Mount Vogelsberg in Hesse, Germany

Allelic and genotypic variation at 13 different enzyme loci of autochthonous European beech (Fagus sylvatica L.) was investigated in six 110-160-year-old stands growing at elevations between 150 and 660 m above sea level on the western slope of mount Vogelsberg in central Germany. The highest elevated population showed the highest number of effective alleles (Ne), the highest total heterozygosity (He) and the highest population differentiation deltaT. Also, the genotype SKD-A2A3 of shikimate dehydrogenase was significantly more frequent at the two highest elevated stands (P = 11%) than at the three lowest elevated stands (P = 1%). Further differences in genotype frequencies between 11 of 15 stand pairs were elevation independent.     

Dormancy release in beech buds (Fagus sylvatica) requires both chilling and long days

Chilling and daylength requirements for dormancy release and budburst in dormant beech ( Fagus sylvatica L.) buds have been studied in cuttings flushing in controlled environments after different durations of outdoor chilling. Non-chilled buds sampled in mid October required long days (LD) only for budburst. Buds chilled until March still required LD for normal budburst, whereas buds sampled in November and December were unable to sprout regardless of daylength conditions and would do so only after a substantial period of chilling. Four ecotypes of distant latitudinal and altitudinal origin responded very similarly with a typical quantitative photoperiodic response. In fully chilled shoots sampled in March only 13 to 40% budburst took place in 8-h SD and only after three times as long time as in continuous light. It is concluded that this dual dormancy control system ensures optimum winter stability in trees under conditions of climatic warming. In the closely related Carpinus betulus L. budburst was unaffected by daylength.     

Phosphate and calcium uptake in beech (Fagus sylvatica) in the presence of aluminium and natural fulvic acids

In the present study we examine the effects of Al on the uptake of Ca²⁺ and H₂PO^-₄ in beech (Fagus sylvatica L.) grown in inorganic nutrient solutions and nutrient solutions supplied with natural fulvic acids (FA). All the solutions used were chemically well characterized. The uptake of Al by roots of intact plants exposed to solutions containing 0, 0.15 or 0.3 mM AlCl₃ for 24 h, was significantly less if FA (300 mg l⁻¹) were also present in the solutions. The Ca²⁺(⁴⁵Ca²⁺) uptake was less affected by Al in solutions supplied with FA than in solutions without FA. There was a strong negative correlation between the Al and Ca²⁺ uptake (r²=0.98). When the Al and Ca²⁺ (⁴⁵Ca²⁺) uptake were plotted as a function of the Al³⁺ activity (or concentration of inorganic mononuclear Al), almost the same response curves were obtained for the -FA and +FA treatments. We conclude that FA-complexed Al was not available for root uptake and therefore could not affect the Ca²⁺ uptake. The competitive effect of Al on the Ca²⁺ uptake was also shown in a 5-week cultivation experiment, where the Ca concentration in shoots decreased at an AlCl₃ concentration of 0.3 mM. The effect of Al on H₂PO⁻₄ uptake was more complex. The P content in roots and shoots was not significantly affected, compared with the control, by cultivation for 5 weeks in a solution supplied with 0.3 mM AlCl₃, despite a reduction of the H₂PO⁻₄ concentration in the nutrient solution to about one-tenth. At this concentration Al obviously had a positive effect on H₂PO⁻₄ uptake. The presence of FA decreased ³²P-phosphate uptake by more than 60% during 24 h, and the addition of 0.15 or 0.3 mM AlCl₃ to these solutions did not alter the uptake of ³²P-phosphate.     

Influence of aluminium on phosphorus and calcium localization in roots of beech (Fagus sylvatica)

Beech plants ( Fagus sylvatica L. provenance Maramures) were grown in nutrient solution at low pH (4.2) and exposed to different concentrations of AlCl₃. Uptake and leakage of Ca²⁺(⁴⁵Ca²⁺) and H²PO₄-(³²P) were studied. A high external aluminium concentration (1.0m M ) reduced the uptake and export to the shoot of both calcium and phosphate, while 0.1 m M Al increased the phosphorus level in the roots. To determine the impact of aluminium on the localization of calcium and phosphate, leakage of the elements from both intact plants and plants frozen prior to the leakage experiment was studied. The leakage of Ca²⁺ from intact plants was not affected by prior exposure to 0.1 m M Al. Freezing of the beech plants before the leakage experiment increased leakage of calcium slightly more from roots of control plants than for roots exposed to 0.1 m M Al, indicating that even low concentrations of alminium may impede the influx of calcium across the plasma membrane in the roots. The patterns of Ca²⁺ leakage from roots previously exposed to 1.0 m M Al indicated that very little Ca²⁺ was located extracellularly. The extracellular fraction of phosphate increased with increasing Al concentration in the nutrient solution. Low Al concentration (0.1 m M ) only reduced the intracellular phosphate concentration to a minor extent, while 1.0 m M Al profoundly decreased it. It is concluded that 0.1 m M AlCl₃ has a limited effect upon the localization of Ca²⁺ and phosphate in the roots. At higher levels of Al, 0.1–1.0 m M , there is a more dramatic change in nutrient localization in the free space and uptake over the plasma membrane.     

Influence of aluminium on biomass, nutrients, soluble carbohydrates and phenols in beech (Fagus sylvatica)

The effects of aluminium on biomass, nutrients and soluble carbohydrates and phenols were studied in beech ( Fagus sylvatica L.) seedlings. After germination, seedlings with cotyledons and the buds of the first leaf-pair developed, were preconditioned for two weeks and then grown for 31 days in nutrient solutions containing 0.1, 0.5, 1.0 or 2.0 m M A1C1₃. Aluminium did not affect the dry weights of roots but at Al concentrations ≥ 1.0 m M the development of the terminal shoot above the first leaf pair, was reduced by 80% or more. The concentrations of most nutrients (P, Ca, Mg, Zn, Cu) in the plant tissues decreased strongly even at the lowest Al levels, but K increased in the shoots. The tissue concentration of N was not affected of Al. but the distribution between the organs was changed to a higher content of N in the roots. At ≥1.0 m M Al the concentrations of starch in both the shoots and the roots were significantly increased, and at ≥ 0.5 m M the roots contained more of total phenols than untreated seedlings. The elevated concentrations and contents of starch and phenols in the seedlings may partly be related to the reduced shoot growth. The observed effects of Al were marked already at Al levels found in soil waters from beech forests in southern Sweden.     

Gene Flow in European Beech (Fagus sylvatica L.)

Three relatively isolated stands were used to study gene flow in European beech (Fagus sylvatica L.) in Northern Germany. Nine allozyme loci (Got-B, Idh-A, Lap-A, Mdh-B, Mdh-C, Mnr-A, 6-pgdh-A, Pgi-B and Pgm-A) were utilized for multilocus-genotyping adult trees and seeds. Expected heterozygosity (He) ranged from 0.325 to 0.351 for the three stands. F(ST) revealed that there was small differentiation among stands (mean F(ST) = 0.013). The indirect estimates of gene flow (Nm) based on the mean F(ST) were high and the average Nm was 19.14. External gene flow by pollen ranged from 0.7 to 1.2% inferred from new alleles in seed samples. Moreover, paternity analysis was used to assess effective pollen dispersal by inferring paternity of offspring. The weighted mean distances of pollen dispersal for these three stands were 36.8 and 37.1 m based on simple exclusion procedure and most-likely method, respectively. Two of the trees in one stand had rare allozyme alleles (Lap-A1 and Idh-A4, respectively), which were used to directly measure pollen movement away from those trees. The frequency of the rare Lap and Idh alleles in seeds declines as the distance from the source tree increases. The weighted mean distance of pollen dispersal with rare allele Lap-A1 or Idh-A4 was 26.3 m.     

Long-distance transport of 35S-sulphur in 3-year-old beech trees (Fagus sylvatica)

³⁵S-L-cysteine was fed to a mature leaf of 3-year-old beech trees via a flap. After 1 to 4 h the distribution of ³⁵S-radioactivity was analysed in the leaves as well as the bark and wood of the trunk and the main root. Transport of ³⁵S out of the fed leaf amounted to 0.3–1.2% of the total ³⁵S taken up. The branches of the trees did not act as sink organs for the exported radioactivity. The main portion of the ³⁵S-radioactivity transported out of the fed leaf was found in basipetal parts of the trunk. Only a small portion of ³⁵S-radioactivity was transported in acropetal direction. The distribution of the ³⁵S-radioactivity within the trunk showed a higher portion of ³⁵S in the bark than in the wood. In both tissues, bark (70 to 80%) and wood (60 to 70%), the ³⁵S was predominantly found in the HCl soluble fraction. However, ³⁵S-cysteine, the compound fed to the leaves was not exported out of the fed leaf. Along the trunk ³⁵S-cysteine was neither determined in bark nor in wood sections. The only low molecular mass S-compounds found was ³⁵S-glutathione (GSH). The ³⁵S-sulphate detected in bark and wood origined from cysteine oxidation in the leaf tissue and from contamination of the ³⁵S-cysteine feeding solution. The ratio of GSH to sulphate decreased with increasing distance from the fed leaf. Apparently, ³⁵S-radioactivity was transported as sulphate and GSH in the phloem in basipetal direction, but GSH was removed preferentially out of the phloem along the transport path. ³⁵S-radioactivity exported out of the phloem and transported into the wood of the trunk was not retranslocated in the xylem. It may therefore be assumed that part of the ³⁵S translocated was stored in ray cells, medullary sheath cells and/or pith parenchyma cells. Girdling experiments in which the bark of the trunk was peeled off basipetal to the branch containing the fed leaf support these assumptions.     

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.     

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     

Influence of aluminium on phosphate and calcium uptake in beech (Fagus sylvatica) grown in nutrient solution and soil solution

The effects of AICI₃ on uptake of Ca²⁺ and phosphate in roots of intact beech ( Fagus sylvatica L. provenance Maramures) plants were studied in nutrient solution and soil solution. Aluminium reduced the concentrations of Ca, Mg and P in plants and increased that of K. In short term experiments, uptake of Ca²⁺(⁴⁵Ca) was reduced by exposure of the roots to Al. The effect of aluminium on Ca²⁺(⁴⁵Ca) uptake was immediate and primarily of a competitive nature, preventing Ca²⁺ from being adsorbed. Uptake of ³²P-phosphate increased with increasing Al concentration up to 0.1 m M and then decreased at higher Al concentrations. The effect of Al on ³²P-phosphate uptake was most pronounced during the first hours of exposure. Growth of plants for 15 days in soil solution, collected from the upper A horizon of a beech forest soil, had no effect on uptake of Ca²⁺(⁴⁵Ca) and ³²P-phosphate, probably because of a low concentration of labile bound monomeric Al and binding of Al to organic compounds. Soil solution from the deeper B horizon reduced Ca²⁺(⁴⁵Ca) uptake and increased ³²P-phosphate uptake in a manner similar to that with Altreatment in nutrient solution. It is concluded that in soil solution from the deeper regions of the soil, mineral uptake by roots was affected by Al.     

Responses to ozone in 12 provenances of European beech (Fagus sylvatica): genotypic variation and chamber effects on photosynthesis and dry-matter partitioning

Seedlings of 12 provenances of European beech ( Fagus sylvatica ) were exposed to ambient, non-filtered air (NF) or NF+50 nl l⁻¹ ozone (NF50) for 8 h d⁻¹ in open-top chambers (OTCs), from 1 June to 4 October 1995. In 1996 exposure was continued from 31 May to 1 October at four levels: charcoal-filtered air (CF), NF, NF50 and NF+100 nl l⁻¹ ozone (NF100). Provenances were grown for both seasons in outside reference plots. All treatments were replicated. Ozone did not affect gas exchange in the provenances until late in the second season. NF100 reduced photosynthesis by 18% in August 1996 compared to CF. In September, photosynthesis was reduced by 22% in NF50 and by 29% in NF100. After two seasons, ozone reduced the root:shoot ratio by 24% when comparing CF and NF100; this was caused by reductions in the root biomass. Ozone did not affect height growth or stem diameter, and there were no ozone×provenance interactions for any growth parameter. There was, however, a significant ozone×provenance interaction for photosynthesis, showing northwest European provenances to be more sensitive to ozone than southeast European provenances when comparing dose–response estimates. This is interpreted in terms of genetic adaptation of the photosynthetic apparatus to regional growing conditions. Seedlings in the chambers grew 45% taller, and had 28% more shoot biomass and 29% smaller root biomass, resulting in a 44% reduction of root:shoot ratios compared to seedlings outside. Increased temperature and decreased PAR inside the chambers relative to the outside were probably the main causes for the differences. The magnitude of the chamber effects in OTCs raises doubts about conclusions drawn from ozone exposures in such chambers. This and previous ozone experiments with OTCs may have reached inaccurate conclusions concerning the size of ozone responses due to chamber effects.