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At least 127 records · Page 7Linked to original sources
PubMed2006

Carbon isotopic composition and oxygen isotopic enrichment in phloem and total leaf organic matter of European beech (Fagus sylvatica L.) along a climate gradient.

This study investigated the influence of climate on the carbon isotopic composition (sigma13C) and oxygen isotopic enrichment (delta18O) above the source water of different organic matter pools in European beech. In July and September 2002, sigma13C and delta18O were determined in phloem carbohydrates and in bulk foliage of adult beech trees along a transect from central Germany to southern France, where beech reaches its southernmost distributional limit. The data were related to meteorological and physiological parameters. The climate along the transect stretches from temperate [subcontinental (SC)] to submediterranean (SM). Both sigma13Cleaf and delta18Oleaf were representative of site-specific long-term environmental conditions. sigma13C of leaves collected in September was indicative of stomatal conductance, vapour pressure deficit (VPD) and radiation availability of the current growing season. delta18O was mainly correlated to mean growing season relative humidity (RH) and VPD. In contrast to the leaves, sigma13Cphloem varied considerably between July and September and was well correlated with canopy stomatal conductance (Gs) in a 2 d integral prior to phloem sampling. The relationship between sigma13C and delta18O in both leaves and phloem sap points, however, to a combined influence of stomatal conductance and photosynthetic capacity on the variation of sigma13C along the transect. delta18Ophloem could be described by applying a model that included 18O fractionation associated with water exchange between the leaf and the atmosphere and with the production of organic matter. Hence, isotope signatures can be used as effective tools to assess the water balance of beech, and thus, help predict the effects of climatic change on one of the ecologically and economically most important tree species in Central Europe.

Carbon Isotopes↗
PubMed2000

Winter North Atlantic oscillation effects on the tree rings of the Italian beech (Fagus sylvatica L.).

Climatic signals in beech tree-ring width series from Central Italy have been studied over different periods of time. Prewhitened tree-ring chronologies respond mainly to summer precipitation and they do not correlate in a significant manner with the winter North Atlantic oscillation (NAO) index. In this high-frequency pattern the NAO signs are only found on a small number of rings characterized by being very narrow or wide. By contrast, tree-ring width chronologies in which all the frequency components are conserved were significantly related to the NAO. The significant inverse correlation between actual measurements of ring width and NAO is a consequence of the availability of water in the soil at the beginning of the growing season. In fact, in the Mediterranean area the recharging of soil moisture depends on the amount of winter precipitation, which is inversely correlated with the NAO. Strong signals of winter precipitation and NAO are found in the low-frequency components of tree-ring growth.

Climate↗
PubMed2000

Ozone exposure-response relationships for biomass and root/shoot ratio of beech (Fagus sylvatica), ash (Fraxinus excelsior), Norway spruce (Picea abies) and Scots pine (Pinus sylvestris).

Current-year seedlings of beech, ash, Norway spruce and Scots pine were exposed during one growing season to different, but moderate, ozone (O(3)) scenarios representative for Switzerland (50, 85, 100% ambient, 50% ambient+30 nl l(-1)) in open-top chambers (OTCs) and to ambient O(3) concentrations in the field. Biomass significantly decreased with increasing O(3) dose in all species except for spruce. Losses of 25.5% (ash), 17.4% (beech), 9.9% (Scots pine) were found per 10 microl l(-1) h accumulated O(3) exposure over a threshold concentration of 40 nl l(-1) during daylight hours (AOT40). Ratios of root/shoot biomass (RSR) also significantly decreased with increasing AOT40 levels in beech and ash, but not in Norway spruce and Scots pine. The data show that the deciduous species beech and ash were more susceptible to O(3) with respect to RSR and biomass than the coniferous species Norway spruce and Scots pine.

Journal Article↗
PubMed1978

[Ultrastructural study of the biodegradation processes. I. Beech (Fagus sylvaticus L.) leaf white rot].

An electron microscopic study of beech leaf white rot shows a certain number of characteristic developmental stages which are identical whether the material is from in vitro experimentation or from natural incubation. Endowed with a cellulolytic properly seemingly localized in the apical region only, hyphae of the white rot agent only traverse the plant cell walls. Subsequently, hyphae penetrate condensed protoplasmic residues and make them progressively transparent to electrons. During this discoloring process, a lethal factor of as yet unknown nature appears, affecting other microorganisms already present in the leaves. Phloem and xylem vascular bundles do not present notable ultrastructural modifications. Therefore, leaf discoloration is not due to an alteration of the xylem constituents but to changes having occurred in the condensed cytoplasmic residues of the dead tissues.

Bacteria↗
PubMed2006

13C labelling reveals different contributions of photoassimilates from infructescences for fruiting in two temperate forest tree species.

The pathways of currently fixed carbon in fruit bearing branchlets were investigated in two temperate forest tree species (CARPINUS BETULUS and FAGUS SYLVATICA), which differ in texture of their vegetative infructescence tissues (leaf-like in CARPINUS vs. woody in FAGUS). During late spring, (13)C pulse-labelling was conducted on girdled, defoliated, girdled plus defoliated and untreated fruiting branchlets of mature trees IN SITU, to assess changes in C relations in response to the introduced C source-sink imbalances. At harvest in early August, 75 - 100 % of the recovered (13)C label was bound to infructescences (either fruits or vegetative infructescence tissue), revealing them as the prime C sinks for current photoassimilates. Leaves on girdled branchlets were not stronger labelled than on ungirdled ones in both species, indicating no upregulation of the leaves' photosynthetic capacity in response to the prevention of phloemic transport, which was also supported by measurements of light saturated photosynthesis. In contrast, (13)C labels tended to be higher after complete defoliation in the vegetative infructescence tissues of CARPINUS, suggesting enhanced net photosynthesis of green infructescence parts as compensation for the loss of regular leaves. The total labelling-derived (13)C content of whole infructescences was very similar between foliated and defoliated CARPINUS branchlets. Cupulae of FAGUS, on the other hand, remained almost unlabelled on defoliated branchlets, indicating the photosynthetic inactivity of this woody infructescence tissue. Consequently, CARPINUS still produced relatively high fruit masses on girdled plus defoliated branchlets, while in FAGUS fruit development ceased almost completely at this most severe treatment. Our results highlight that green vegetative infructescence tissue assimilates substantial amounts of C and can partly substitute regular leaves as C sources for successful fruit development.

Betulaceae↗
PubMed2006

Coordination of crown structure, leaf plasticity and carbon gain within the crowns of three winter-deciduous mature trees.

We examined the vertical profiles of leaf characteristics within the crowns of two late-successional (Fagus crenata Blume and Fagus japonica Maxim.) and one early-successional tree species (Betula grossa Sieb. et Zucc.) in a Japanese forest. We also assessed the contributions of the leaves in each crown layer to whole-crown instantaneous carbon gain at midday. Carbon gain was estimated from the relationship between electron transport and photosynthetic rates. We hypothesized that more irradiance can penetrate into the middle of the crown if the upper crown layers have steep leaf inclination angles. We found that such a crown has a high whole-crown carbon gain, even if leaf traits do not change greatly with decreasing crown height. Leaf area indices (LAIs) of the two Fagus trees (5.26-5.52) were higher than the LAI of the B. grossa tree (4.50) and the leaves of the F. crenata tree were more concentrated in the top crown layers than were leaves of the other trees. Whole-crown carbon gain per unit ground area (micromol m(-2) ground s(-1)) at midday on fine days in summer was 16.3 for F. crenata, 11.0 for F. japonica, and 20.4 for B. grossa. In all study trees, leaf dry mass (LMA) and leaf nitrogen content (N) per unit area decreased with decreasing height in the crown, but leaf N per unit mass increased. Variations (plasticity) between the uppermost and lowermost crown layers in LMA, leaf N, the ratio of chlorophyll to N and the ratio of chlorophyll a to b were smaller for F. japonica and B. grossa than for F. crenata. The light extinction coefficients in the crowns were lower for the F. japonica and B. grossa trees than for the F. crenata tree. The leaf carbon isotope ratio (delta(13)C) was higher for F. japonica and B. grossa than for F. crenata, especially in the mid-crown. These results suggest that, in crowns with low leaf plasticity but steep leaf inclination angles, such as those of F. japonica and B. grossa trees, irradiance can penetrate into the middle of the crowns, thereby enhancing whole-crown carbon gain.

Betula↗
PubMed2004

Airborne pollen calendar of Lublin, Poland.

Pollen concentration in the atmosphere of Lublin (eastern Poland) was studied by means of volumetric method using Hirst sampler (VPPS 2000, Lanzoni) in 2001-2002. The pollen trap was mounted at the height of 15 m in the centre of Lublin. On the basis of analysis of mean daily values of pollen concentration, the pollen calendar was constructed for 16 taxa producing the allergenic pollen: Alnus, Corylus, Populus, Ulmus, Fraxinus, Betula, Carpinus, Quercus, Fagus, Pinaceae, Poaceae, Rumex, Plantago, Chenopodiaceae, Artemisia, Urticaceae. Great differences referring to the course of pollen seasons for most of the studied taxa of trees within the 2 years of study were found. They were associated with the beginning and end of the pollen season, the amount and the date of maximum pollen concentration occurrence, as well as annual sums of pollen grains. Much lower differentiation was observed in the case of herbaceous plants. This referred mainly to maximum concentration occurrence dates (Urtica, Poaceae) and the length of pollen season (Chenopodiaceae). The most similar course of pollen seasons during 2 years was recorded for Artemisia. Among trees, the highest pollen concentrations were recorded for Betula, Pinaceae and Alnus; the lowest for Ulmus, Fagus and Corylus. Very high concentration of herbaceous plant's pollen was observed for Poaceae and Urtica; Plantago and Chenopodiaceae showed the lowest level. Annual sums of pollen grains for Alnus, Populus, Quercus, Betula and Pinaceae were much higher in 2001, but in the case of Ulmus, Fraxinus, Carpinus, Fagus the annual sums of pollen grains in 2002 were almost twice as high as in 2001. For 5 among 7 herbaceous taxa, annual sums of pollen grains in both years were similar.

Air Pollutants↗
PubMed2003

Elevated CO2 reduces sap flux in mature deciduous forest trees.

We enriched in CO2 the canopy of 14 broad-leaved trees in a species-rich, ca. 30-m-tall forest in NW Switzerland to test whether elevated CO2 reduces water use in mature forest trees. Measurements of sap flux density (JS) were made prior to CO2 enrichment (summer 2000) and throughout the first whole growing season of CO2 exposure (2001) using the constant heat-flow technique. The short-term responses of sap flux to brief (1.5-3 h) interruptions of CO2 enrichment were also examined. There were no significant a priori differences in morphological and physiological traits between trees which were later exposed to elevated CO2 (n=14) and trees later used as controls (n=19). Over the entire growing season, CO2 enrichment resulted in an average 10.7% reduction in mean daily JS across all species compared to control trees. Responses were most pronounced in Carpinus, Acer, Prunus and Tilia, smaller in Quercus and close to zero in Fagus trees. The JS of treated trees significantly increased by 7% upon transient exposure to ambient CO2 concentrations at noon. Hence, responses of the different species were, in the short term, similar in magnitude to those observed over the whole season (though opposite because of the reversed treatment). The reductions in mean JS of CO2-enriched trees were high (22%) under conditions of low evaporative demand (vapour pressure deficit, VPD <5 hPa) and small (2%) when mean daily VPD was greater than 10 hPa. During a relatively dry period, the effect of elevated CO2 on JS even appeared to be reversed. These results suggest that daily water savings by CO2-enriched trees may have accumulated to a significantly improved water status by the time when control trees were short of soil moisture. Our data indicate that the magnitude of CO2 effects on stand transpiration will depend on rainfall regimes and the relative abundance of the different species, being more pronounced under humid conditions and in stands dominated by species such as Carpinus and negligible in mono-specific Fagus forests.

Betulaceae↗
PubMed1989

Effect of ambient ozone and acid mist on aphid development.

The effect of ambient air with increased ozone concentrations and artificial acid mist on the population growth of two different aphid species was studied: Aphis fabae on Phaseolus vulgaris and Phyllaphis fagi on seedings of Fagus sylvatica. Whereas the ambient air inhibited growth of Aphis fabae, it stimulated population growth of Phyllaphis fagi. In Fagus, analysis of a phloem exudate revealed that the amino acid/sugar ratio was significantly increased by the ambient air compared to filtered air. In Phaseolus, no significant differences in amino acid or sugar content of the phloem exudate could be found. Acid mist inhibited population development in both aphid species; the strongest effect was observed in the first weeks after artificial infestation.

Journal Article↗
PubMed2001

Variation of gas exchange within native plant species of Switzerland and relationships with ozone injury: an open-top experiment.

Gas exchange and ozone-induced foliar injury were intensively measured during a 6-day period in mid-August 1998 on leaves of Acer pseudoplatanus, Betula pendula, Corylus avellana, Fagus sylvatica, Fraxinus excelsior, Morus nigra, Prunus avium, Prunus serotina, Rhamnus cathartica, and Viburnum lantana at a forest nursery site in Canton Ticino, Switzerland. Plants were grown in four open plots (AA), four open-top chambers receiving carbon-filtered (CF) air, and four receiving non-filtered (NF) air. Significant variation in gas exchange (F > 12.7, P < 0.001) was detected among species with average net photosynthesis and average stomatal conductance differing by a factor of two. Species also varied significantly in foliar injury for those leaves for which we measured gas exchange (F = 39.6, P < 0.001). Fraxinus excelsior, M. nigra, P. avium, P. serotina, R. cathartica, and V. lantana showed more injury than A. pseudoplatanus, B. pendula, C. avellana, and Fagus sylvatica. Plants grown in CF chambers had significantly higher net photosynthesis (A) and stomatal conductance to water vapor (gwv), and lower foliar injury than plants grown in NF chambers and AA plots; interactions between species and ozone treatments were significant for all variables (F > or = 2.2, P < 0.05) except gwv (F = 0.7, P > 0.1). Although A and gwv decreased and foliar injury increased with leaf age, the magnitude of these changes was lower for plants grown in CF chambers than for plants grown in NF chambers and AA plots. Neither ozone uptake threshold (r = 0.26, P > 0.20) nor whole-plant injury (r = -0.15, P > 0.41) was significantly correlated with stomatal conductance across these species. It appears that the relationships between stomatal conductance and foliar injury are species-specific and interactions between physiology and environments and leaf biochemical processes must be considered in determining species sensitivity to ambient ozone exposures.

Air Pollution↗