Showing papers by "Swiss Federal Institute for Forest, Snow and Landscape Research published in 1997"

Phylogeographic structure of white oaks throughout the European continent

Abstract: Patterns of chloroplast DNA (cpDNA) variation were studied in eight white oak species by sampling 345 populations throughout Europe. The detection of polymorphisms by restriction analysis of PCR-amplified cpDNA fragments allowed the identification of 23 haplotypes that were phylogenetically ordered. A systematic hybridization and introgression between the eight species studied is evident. The levels of subdivision for unordered (GST) and ordered (NST) alleles are very high and close (0.83 and 0.85). A new statistical approach to the quantitative study of phylogeography is presented, which relies on the coefficients of differentiation GST and NST and the Mantel's test. Based on pairwise comparisons between populations, the significance of the difference between both coefficients is evaluated at a global and a local scale. The mapped distribution of the haplotypes indicates the probable routes of postglacial recolonization followed by oak populations that had persisted in southern refugia, especially in the Iberian peninsula, Italy and the Balkans. Most cpDNA polymorphisms appear to be anterior to the beginning of the last recolonization. A subset of the preexisting haplotypes have merely expanded north, while others were left behind in the south.

Tree-ring based reconstruction of summer temperatures at the Columbia Icefield, Alberta, Canada, AD 1073-1983:

Abstract: April-August temperatures are reconstructed from maximum latewood density and ring-width data for a tree-line site in the Canadian Rockies of Alberta close to Athabasca Glacier. The chronology primarily utilizes Picea engelmannii with some Abies lasiocarpa snags. This reconstruction (AD 1073-1983) is the longest densitometrically based summer temperature record from boreal North America. Mean temperatures from 1101- 1900 were 0.71°C below the 1961-1990 reference period and 0.33°C below the 1891-1990 mean of the instru mental record. The coldest interval was the first half of the nineteenth century and the major cold intervals, c. 1200-1350, 1690s and the nineteenth century, coincide with local and regional periods of glacier expansion. Warmer periods, c. 1350-1440 and in the present century, are also periods of higher tree-line or tree-line advance at the site. The 1961-1990 reference period is clearly warmer than any equivalent-length period over the last 800 years. This record of summer warmth reinforce...

Stable carbon isotopes in tree rings of beech : climatic versus site-related influences

Abstract: Stable carbon isotopes in tree rings are a promising tool in palaeoclimate research, provided attempts are made to disentangle climatic from local effects (e.g. soil properties, competition, light). The 13C/12C variations in cellulose of tree rings of beech (Fagus sylvatica) were determined at several sites in the Swiss Central Plateau covering the last 50 years. We chose sites which differ in moisture conditions and sampled cores from four to six trees per site. The mean 13C/12C series from the different dry sites (distant by up to 40 km) are closely interrelated suggesting a common external cause. Correlation analysis with climate data proved the total precipitation in the months May, June and July to have the strongest effect on the carbon isotopes (r = – 0.73). This result is in agreement with the commonly used model which relates the isotope discrimination to the water use efficiency. On the other hand, the isotope series of the wet sites are not as well correlated to the climate. At two of the sites (a dry and a humid) tree ring width suddenly increased. We used this effect as a test-case to study the influence of local growth conditions on the climate-isotope relationship.

Sediment transport in Swiss torrents

Abstract: Sediment loads have been measured in six Swiss mountain torrents over several decades. Most of these torrent catchments are situated in the prealpine belt. They have catchment areas of between 0·5 and 1·7km 2. Bedslopes at the measuring sites vary between 5 and 17 per cent, and peak discharges up to 12m 3 s−1 have been recorded. Geophone sensors installed in the Erlenbach stream allow bedload transport activity to be monitored and sediment volumes associated with each flood event to be determined. A detailed analysis of the measurements in this stream results in an empirical equation in which the sediment load per flood event is expressed as a function of the effective runoff volume (discharges above the threshold for bedload motion) and of the normalized peak discharge. For the total of 143 investigated flood events in the Erlenbach stream, the deviation of the predicted from the measured value is within a factor of two for more than two-thirds of all events. A distinction can be made between summer and winter events in analysing the bedload transport events. The summer events, mainly caused by thunderstorms, transport comparatively larger sediment loads than the winter events. For the other investigated streams, the periods of the deposited sediment volume surveys cover in general several flood events. An analysis is performed analogous to that for the Erlenbach stream. The sediment loads show a similar dependency on the two factors effective runoff volume and normalized peak discharge. However, the exponents of these factors in the power law expressions differ from stream to stream. A comparison of the investigated stream shows that some of the variation can be explained by considering the bedslope above the measuring site. The inclusion of a bedslope factor is in agreement with laboratory investigations on bedload transport.  1997 by John Wiley & Sons, Ltd. Earth surf. process. landforms, 22, 937–951 (1997) No. of figures: 12 No. of tables: 2 No. of refs: 30

Climatic change and debris flows in high mountain regions: the case study of the ritigraben torrent (swiss alps)

Abstract: Debris flows in the region of Ritigraben (Valais, Swiss Alps), which generally occur in the months of August and September, have been analyzed in relation to meteorological and climatic factors. The principal trigger mechanisms for such debris flows are abundant rain on the one hand, and snow-melt and runoff on the other hand, or a combination of both. Debris flows linked to rain are likely to be triggered when total rainfall amount over a three-day period exceeds four standard deviations, i.e., a significant extreme precipitation event. An analysis of climatological data for the last three decades in the region of Ritigraben has highlighted the fact that the number of extreme rainfall events capable of triggering debris flows in August and September has increased. Similar trends are observed for the 20th Century in all regions of Switzerland. The general rise in temperature in a region of permafrost may also play a role in the response of slope stability to extreme precipitation. At the foot of the Ritigraben, warming trends of both minimum and maximum temperatures have been particularly marked in the last two decades.

Regionalization of precipitation in Switzerland by means of principal component analysis

Abstract: The technique of principal component analysis and of cluster analysis has been applied to two sets of precipitation data in Switzerland, one containing 47 stations (1961-80), and the other 101 stations (1981-1993), with the aim of understanding more fully the spatial distribution of precipitation regimes. Seven regions were highlighted in the first case and 13 in the second. The high spatial coherence which appeared is quite remarkable and confirms the usefulness of these techniques for the analysis of the spatial distribution of meteorological variables, even in a topographically complex area such as Switzerland. The two regional distributions obtained not only correspond fairly well to the large, well-known physical regions of Switzerland, but also go much further, separating the Swiss Plateau into 3 clearly differentiated regions, for example. Regional distributions such as those discussed here can have value for climate change issues, and in particular numerical modeling of climate or climate change impacts on forests.

Effect of fertilization on ozone‐induced changes in the metabolism of birch (Betula pendula) leaves

Abstract: summary Cloned cuttings of Betula pendula Roth were grown in field fumigation chambers at Birmensdorf throughout one growing season in filtered air with either < 3 (control) or 90/40 nl l−1O3(day/night; ozone generated from pure oxygen). Each ozone regime was split into high and low soil nutrient regimes by watering plants with either a 0.05 % or a 0.005% solution of a fertilizer which contained macronutrients and micronutrients. Fertilization had a strong effect on plant growth, enzyme activities and the expression of ozone-induced effects at the biochemical level. The activities of PEPC and Rubisco were enhanced about threefold in the plants with high fertilization (HF). Significant effects of ozone were in most cases found only in the older leaves of the plants with low fertilization (LF), There, sucrose, glucose and fructose levels were enhanced. In both fertilization treatments, the number of starch granules along the minor veins was increased. These ozone effects point to a decreased or inhibited phloem loading. The increased PEPC activity and the enhanced malate levels in the ozone-exposed plants might be the result of a redirection of carbon flow from sucrose synthesis and translocation towards anapleurotic processes, which can feed detoxification and repair of ozone injury as indicated by enhanced respiration. These findings agree well with the observed effects of ozone in lowering the root: shoot biomass ratio. Although there was a marked reduction in the O3/LF plants, O3/HF plants showed no significant response. Inositol was decreased under ozone exposure in both fertilizer treatments, contrasting with the pattern for carbohydrates. These results demonstrate the role of fertilization as an important modifier of ozone-induced effects at the plant biochemical level. Well fertilized plants appear to cope better with the impact of ozone on metabolism.

Nutrition and the ozone sensitivity of birch ( Betula pendula )

Abstract: Cuttings of a single birch clone (Betula pendula) were grown in field fumigation chambers throughout the growing season in either filtered air (control) or 90/40 nl O3 l–1 (day/night). Both regimes were split into plants under high and low nutrient supply (macro- and micronutrients). The stomatal density of leaves was increased by ozone but was lowered at high nutrition, while the inner air space was hardly affected by the treatments. Ozone induced macroscopic leaf injury regardless of nutrition, but leaf shedding was delayed in the low-fertilized plants, despite O3 uptake being similar to that in high-fertilized plants. The leaf turn-over was enhanced in the O3-exposed high-fertilized plants, but length growth and leaf formation of stems were not affected by ozone in either nutrient regime. Leaves of high-fertilized plants showed O3-caused decline in photosynthetic capacity, water-use efficiency, apparent carbon uptake efficiency and quantum yield earlier as compared with low-fertilized plants, whereas chlorophyll fluorescence (FV/FM) and leaf nitrogen concentration were rather stable. CO2 uptake rate and rubisco activity of young leaves compensated for the O3 injury in the ageing leaves of the low-fertilized plants. In 8-week-old leaves, however, the O3-induced decline in CO2 uptake did not differ between the nutrient regimes and was associated with increased dark respiration rather than changed photorespiration. The balance between CO2 supply and demand was lost, as was stomatal limitation on CO2 uptake. High nutrition did not help leaves to maintain a high photosynthetic capacity and life span under O3 stress.

Atmospheric Lead Deposition from 12,400 to ca. 2,000 yrs BP in a Peat Bog Profile, Jura Mountains, Switzerland

Abstract: The bog at Etang de la Gruere (Jura Mountains, Switzerland) consists of 420 cm of Sphagnum-dominated bog peat overlying 230 cm of Carex-dominated fen peat. One hundred cm below the bog surface, there is a pronounced peak in lead (Pb) concentration (approx. 10 µg/g) which has been dated at 2110 ± 30 BP and can be attributed to Roman Pb mining and smelting.

Migration in spruce bark beetles (Ips typographus L.) and the efficiency of pheromone traps.

Abstract: Mark-release-recapture experiments with both newly emerged and flight experienced Ips typographus L. were performed in a pine forest near Prague. Three concentric trap circles around the release site with a radius of 5 m, 200 m and 500 m, and intertrap distances of 6 m, 16 m and. maximally, 40 m, were installed with the intention of collecting all dispersing bark beetles ready to respond to pheromone lures. The results show that even without wind and no potential host trees in the surroundings, only about one-third (35.4%) of the emerging beetles in an infested site can be eliminated locally with phermomone traps. At least 12.2% of the emerging beetles (25.7% of the recaptures), perform an adaptive migration flight, which brings them beyond the range of local pheromone traps. The estimated proportion of emigrants can rise over 50%, if most of the freshly emerged beetles that have never been recaptured are assumed to have left the experimental area. Electroantennograms recorded in the laboratory at different times after emergence indicate that the delayed response to aggregation pheromones in migrating bark beetles is not the result of a delayed maturation of the antennal receptor cells, but obviously governed by the central nervous system. The notion of precopulatory migration in 25–50% of the individuals in an I. typographus population can explain why pheromone traps can never eliminate all emerging beetles, and why so many bark beetles can be collected far away from any breeding sites.

Research Strategies in Dendroecology and Dendroclimatology in Mountain Environments

Abstract: Tree-ring series from living trees near the timberline or timbers buried in the surroundings are exceptionally valuable both for climate reconstruction and investigations of the consequences of climate change to ecosystems. This paper is a critical assessment of the past and potential contributions of dendroecology and dendroclimatology in mountain environments. Problems addressed are the spatial variability of both climate and tree sites, the temporal variability of ecological growth conditions and the reconstruction of signals other than high frequency ones. A synoptic approach appears to be the only way to take into account both the spatial and temporal variability of tree-growth, allowing for a better comparison of spatial climatological patterns with spatial growth patterns.

Cryptopodzolic soils in Switzerland.

Abstract: Summary Cryptopodzolic Soils are characterized by a thick blackish-brown mineral horizon rich in organic matter, the dark colour of which masks the morphological characteristics of podzolization. Little is known about the specific site factors that lead to the formation of these soils. Four representative soil profiles from a typical toposequence between 1700 and 500 m above sea level in southern Switzerland, embracing Haplic Podzols, Humic Cambisols and Cryptopodzolic Soils, are described morphologically, chemically and physically. The Cryptopodzolic Soils in this region are characterized by weak to moderate A1 and Fe translocation, and by a uniform incorporation of organic matter deep into the soil. The most prominent feature is the exceptional stability of the soil organic matter with a maximum in the spodic horizon. All these characteristics can be explained by the unique combined effect of a mild, wet climate, an Fe- and Al-rich acid bedrock and a litter layer providing dissolved organic matter rich in polyphenolic substances with strong metal-binding properties.

Frequency, diversity and ecological strategies of epiphytic lichens in the swiss central plateau and the pre-alps

Abstract: To identify representative quantitative criteria for the creation of a future Red List of epiphytic lichens, 849 trees in 132 long-term ecological observation plots in the Swiss Central Plateau and the Pre-Alps were surveyed by standard sampling. Based on the trees, frequency data of the lichen taxa observed are described by the log series model, indicating the controlling effect of few ecological factors. Based on the plots, four classes of scarcity, each comprising 25% of the species, were established. As a contribution to the development of a national, representative survey of lichens, α-diversity (species richness, species density) andβ-diversity (dissimilarity) were calculated in terms of region, vegetation formation, vegetation belt and for their combinations. Differences in lichen diversity between the Central Plateau and the Pre-Alps were caused by the bigger elevational range in the Pre-Alps, which resulted in a higher species richness. α-Diversity of forest and non-forest were similar, whereas each vegetation formation showed one third of its species restricted to it. The contributions to the total lichen diversity of crustose, foliose and fruticose as well as of generative and vegetative species was calculated. Specific features along the altitudinal gradient of vegetation belts emerged: the percentage of crustose and generative lichens declined with every altitudinal step, increased in fruticose and vegetative lichens, and was the same in foliose species.

Ozone‐induced accumulation of carbohydrates changes enzyme activities of carbohydrate metabolism in birch leaves

Abstract: summary Birch cuttings (Betula pendula Roth) were grown in a sand-culture system with two concentrations (0.05, HF and 0.005%, LF) of fertilizer containing macronutrients and micronutrients, and were exposed to 90/40 nl 1−1 O3(day/night) and < 3 nl 1−1 O3 (control) for one growing season in the field fumigation chambers at Birmensdorf (Switzerland). Leaves of different ages were analysed for gas exchange, contents of chlorophyll, protein, and for metabolites as well as enzyme activities of carbohydrate metabolism. Ozone reduced net photosynthesis and chlorophyll contents in mature leaves of both fertilization treatments, whereas that of protein was only reduced in high-fertilized plants (HF). However, net photosynthesis, chlorophyll, and protein increased in young leaves of low-fertilized plants (LF). The effects of ozone on enzyme activities of carbohydrate metabolism were most pronounced in leaves of LF plants. Specific activities of the sucrose-cleaving enzymes, sucrose synthase and alkaline invertase, were induced, whereas acid invertase was unchanged. Extractable activity of sucrose phosphate synthase, which is a key enzyme of sucrose synthesis, was reduced. Levels of fructose 2,6-bisphosphate, an inhibitor of sucrose synthesis, were increased in leaves of O3/LF plants, but reduced in O3/HF plants. In addition, activities of enzymes involved in starch metabolism, ADP-glucose pyrophosphorylase and starch phosphorylase, were lowered in ozone-treated samples and the ratio of ATP: ADP was increased. It is concluded that chronic ozone exposure leads to an inhibition of sucrose synthesis and favours sucrose degradation. This effect is modulated by the nutrient status of the plants, indicating higher O3 tolerance in HF plants. Furthermore, as the metabolic responses in the ozone-treated samples resemble very closely those observed under end-product inhibition of photosynthesis, we assume that the O3 effect is mainly due to reduced photosynthate export.

Element localization in ultrathin cryosections of high-pressure frozen ectomycorrhizal spruce roots

Abstract: We present, for the first time, elemental mapping of ultra-thin cryosections from high-pressure frozen ectomycorrhizal roots of Picea abies–Hebeloma crustuliniforme. The maps provide interpretable information on the relationship between elements and the structure of inhomogeneous objects. Cryoultramicrotomy together with energy dispersive X-ray microanalysis (EDX) offers the potential to study the subcellular localization of specific ions and ecologically important tracers (Cs and Sr) in ectomycorrhizal roots under conditions resembling the natural slate as closely as possible. Structural changes of the ectomycorrhizal roots, in particular the absence of a Hartig net at high NH4+ levels in the nutrient solution, were accompanied by elemental modification of Ca in cortical cell walls, where markedly higher concentrations of Ca were found. Cs and Sr applied to the nutrient solution were localized in root and fungal cells of the Hartig net. Cs accumulated mainly in the vacuoles of the Hartig net hyphae and its distribution was very similar to the distribution of K. In contrast to Cs, Sr was found to occur mainly in electron-opaque and P-rich granules. From this study, (here is no indication that Ca is the only ion accompanying P in the P-rich granules. Several elements including Ca, K, Cl, S, Cs and Sr, with highest concentrations for S, can occur together with P in these granules. The occurrence of the P-rich electron-opaque deposits in fungal cells might be the first evidence of polyphosphate granules in the native state, since our specimen preparation technique did not include chemical fixation.

Morphology and ecological significance of intra-annual radial cracks in living conifers

Abstract: Intra-annual radial cracks were studied on 294 cross-sections of Norway spruce sampled at two forest sites in the eastern Alps (Italy) and from seven isolated trees in the Jura region (Switzerland). Cracks were occasionally accompanied by traumatic resin canals in the wood that was formed after the cracking. Most of the cracks, however, were without such canals. Traumatic resin canals are not significantly more abundant in tree rings formed after cracking, and their occurrence is not related to the cracking. Cracks developed when the cambium was inactive. Water imbalances during the early spring, due to transpiration losses and inadequate moisture supply from very cold roots, are the likely cause of these cracks.

Growth responses to elevated CO2 and soil quality in beech-spruce model ecosystems

Abstract: Nous avons etudie, dans des chambres decouvertes, les reponses de croissance de hetres (Fagus sylvatica L.) et d'epiceas (Picea abies Karst.) a une elevation du CO 2 atmospherique (366 et 550 μl CO 2 l -1 ) et a une augmentation de l'apport d'azote par precipitation (2.5 et 25 kg N ha -1 a -1 ) sur deux types de sols. Huit jeunes hetres et epiceas ont ete installes, en meme temps que 5 especes de sous-bois, dans chacun des 32 ecosystemes modeles. Nous presentons les reponses de croissance initiales des arbres au cours de la premiere annee de traitement, ce qui peut donner des tendances pour des reponses plus long terme a une augmentation du CO 2 . La production de biomasse epidee au niveau du systeme (donnees biometriques) au cours de la premiere annee et la biomasse de racines (donnees de carottage) ne presentent pas de reponses significatives a une elevation du CO 2 , independamment d'autres traitements associes. L'augmentation de l'apport d'azote (traitement debute en milieu de saison) n'a pas non plus d'effet sur la biomasse epigee, alors que la biomasse de racines en fin de saison a augmente significativement dans le sol acide peu fertile fort traitement en azote (74 g m 2 pour le traitement fort en azote et 49 g m 2 pour le traitement faible en azote), mais pas dans le sol calcaire plus fertile. L'augmentation du diametre du tronc des hetres s'accroit significativement (+ 9 %>) sous CO 2 eleve sur sol calcaire mais non sur sol acide. L'inverse a ete trouve pour les troncs d'epiceas qui repondent positivement a une elevation du CO 2 sur sol acide (+ 11 %; P < 0.05) mais non sur sol calcaire. Ces resultats suggerent que le type de sol determine egalement la reponse au CO 2 de jeunes arbres forestiers et que ces interactions sont specifiques. Ces differences initiales sont susceptibles d'affecter les reponses a long terme de la structure de la communaute et du fonctionnement de l'ecosysteme. Le type de sol apparait comme un facteur cle pour les predictions de reponses des forets a un enrichissement continu du CO 2 atmospherique.

MES [2-(N-morpholine)-ethane sulphonic acid] buffer promotes the growth of external hyphae of the arbuscular mycorrhizal fungus Glomus intraradices in an alkaline sand

Abstract: In this work we investigated the hypothesis, suggested by unpublished experiments carried out previously, that application of MES [2-(N-morpholino)-ethane sulphonic acid] buffer to the substrate of plants hosting the arbuscular mycorrhizal fungus Glomus intraradices might favour the growth of external hyphae. The substrate of Trifolium pratense plants, with or without G. intraradices inoculum, was treated twice weekly, between weeks 5 and 11 of growth, plant with distilled water, P-supplemented 10% Hewitt nutrient solution (H+P), 51mM in H+P or 1mM TRIS-HCl in H+P. MES buffer increased the length of external G. intraradices hyphae and the density of propagules in the substrate, but plant growth was not affected. Although both TRIS-HCl and MES caused substrate pH to fall (from 8.51 to 7.35 and 7.17, respectively), only MES induced a significant increase in external hypha length. We conclude that the effect of MES on external hypha length was not due to plant growth or to substrate pH per se.

Combined magnetic, spectroscopic, and analytical-chemical approach to infer genetic information for a Vertisol

Abstract: A Vertisol from a floodplain in southern Mali was investigated by a combination of magnetic and spectroscopic methods in addition to classical soil chemical and physical analyses. This combined approach allowed us to deduce the genesis of the soil. The Ustic Endoaquert profile extended to a water table at 1.2 m and was subdivided into four horizons, Ap (0-0.1 m), A2 (0.1-0.4 m), A3 (0.4-0.6 m), and Ag (0.6-1.2 m). Redoximorphic features were found at a depth between 0.6 and 0.8 m. Prevailing reducing conditions in the Ag horizon were documented by a maximum concentration of exchangeable Mn(II). High redox dynamics were indicated by minimum concentrations of total and extractable Fe in the A3 horizon as well as by minimum susceptibility and saturation isothermal remanent magnetization in the A3 and Ag horizons. The latter minimum was most likely caused by the reductive dissolution of lithogenic magnetite. Soil organic matter (SOM) was generally characterized by a high amount of aromatic compounds and a high degree of lignin decomposition with maxima in the Ag horizon as indicated by solution and solid-state 13 C nuclear magnetic resonance as well as fluorescence spectroscopies. These characteristics of SOM suggested formation under highly oxidative conditions. The presence of such characteristics, in particular in the lower part of the Vertisol with prevailing reducing conditions, suggests an allochthonous origin of the SOM. Pedoturbation in the upper part of the profile was documented by a higher contribution of primary resources such as lignin, cellulose, and hemicellulose in the Ap and A2 horizons.

Effects of Elevated CO2 Concentration and N Deposition on Spruce — Beech Model Ecosystems

Abstract: The Swiss ICAT project, currently underway at the Birmensdorf open-top chamber facility, aims at investigating the biological effects of both elevated CO2 and nitrogen deposition on model ecosystems composed of provenances and clones of young spruce and beech trees as well as an understory of four herbaceous species and ivy. The plants are growing in natural unfertilized forest soils taken from two sites (acidic and calcareous) and transferred into 32 lysimeters, each with a ground area of 3 m2. The model ecosystems were established in fall 1994. Beginning at the end of January 1995, these communities were exposed to either ambient or elevated CO2 (ambient + 200 µl 1−1) concentrations and 5 or 50 kg N ha−1a−1 wet deposition. Emphasis is on understanding ecosystem level responses and their explanation by downscaling to plant and cell level reactions. The multidisciplinary project team will investigate the carbon, water and nutrient cycle.

The effect of elevated CO2 and soil type on non-structural carbohydrates in beech leaves and norway spruce needles growing in model ecosystems

Abstract: Young beech and Norway spruce trees from two Swiss provenances were both planted in an acidic and calcareous soil in 16 open-top chambers. Half of the plants were exposed to elevated CO 2 (ambient, ambient+200 μl l −1 , 24 hrs/day, 365 days/year) and enhanced nitrogen deposition (2.5, 25 kg ha −1 yr −1 ) throughout a single growing season. Leaf and needle samples from all 64 trees were collected (2 provenances×2 soil types×4 treatments×4 replications) at the end of July and September. These were analysed for starch, soluble carbohydrates and total non-structural carbohydrates (TNC). Increased starch and TNC levels were found in plants under elevated CO 2 and those growing on the acidic soil. These effects were not consistent in both species or on both sampling dates. Soluble carbohydrates were only effected significantly by soil type. So far no interactions have been found between CO 2 , N or soil type on any date and in any fraction. It is concluded that soil type should be considered when discussing the effects of elevated CO 2 on starch, soluble carbohydrate or TNC contents in beech and spruce trees.

Leaf and shoot formation of young spruce and beech exposed to elevated CO2

Abstract: Seize chambres a ciel ouvert (divisees en deux moities, l'une contenant un sol calcaire et l'autre un sol acide)onteteexposees 366 ou 550 μl de CO 2 l -1 et irriguees avec 2.5, ou 25 kg N de nitrate d'ammonium ha -1 a -1 en quatre combinaisons. Le developpement de jeunes epiceas (Picea abies) et de jeunes hetres (Fagus sylvatica) plantes dans les chambres a ciel ouvert avec des « herbages » (understory plants) sera etudie pendant quatre ans. Les donnees presentees ici sont le resultat preliminaire de la premiere annee de cette experience. Ils se rapportent a deux provenances suisses, 64 epiceas et 64 hetres. Leurs echantillons ont ete preleves en juillet et en septembre sur chaque type de sol dans chaque chambre. La longueur specifique des aiguilles d'epiceas (longueur/poids a sec) a diminue sous l'influence de concentrations elevees de CO 2 . Ce resultat est du au fait que le poids a sec a augmente. En ce qui concerne les feuilles de hetre, leur surface specifique n'a diminue que temporairement en juillet. Un taux eleve de CO 2 provoqua une ternissure automnale precoce. La longueur totale des pousses de l'annee des epiceas et le nombre total de feuilles de hetres n'ont pas ete influences de facon significative apres l'exposition des concentrations elevees de CO 2 . L'apport d'azote n'a eu aucun effet sur ces parametres. Par contre, le type de sol a influence la couleur des aiguilles d'epicea. Les premiers resultats de ces essais ont ainsi montre que les epiceas, contrairement aux hetres, pourraient profiter de l'elevation du taux de CO 2 , les autres ressources etant illimitees; en effet, le poids sec des pousses et des aiguilles d'epicea a augmente.