15N Distribution in Wheat and Chemical Fractionation of Root-Borne 15N in the Soil

Abstract

Spring wheat plants were grown in split-root containers and labelled with ¹⁵N by fertilizing one compartment of the container with ¹⁵NH₄ ¹⁵NO₃ (95 at.-% ¹⁵N exc.). After the harvest, approx. 90% of the ¹⁵N incorporated by the plants were found in the shoots and 3% in the roots; approx. 7% had been released into the soil of the unlabelled compartment. The ¹⁵N in the soil of the unlabelled compartment was extracted with KCl and hydrolysed with HCl. Approx. 60% of the ¹⁵N was found in the hydrolysable organic N pool of the soil and 9% in the fraction of the soluble and exchangeable inorganic nitrogen.     

Split-root labelling to investigate 15N rhizodeposition by Pinus sylvestris and Picea abies*

We investigated the transfer of ¹⁵N into the soil via ¹⁵N uptake and release by tree roots, which involves the principles of the split-root technique. One half of the root system received an injection of (¹⁵NH₄)₂SO₄ and the other half equivalent amounts of (NH₄)₂SO₄ at ¹⁵N natural abundance level. ¹⁵N was transferred from one side of the root system (¹⁵N side) to the other side (¹⁴N side) and released into the soil. The method was conducted with Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst). Two concentration levels of (NH₄)₂SO₄ were used, corresponding with annual N deposition in the Netherlands (30 kg N ha^–1) and a twelfth of that (2.5 kg N ha^?1). Samples were taken 3 and 6 weeks after labelling and divided into needles?+?stem, roots, rhizosphere and bulk soil. Already 3 weeks after labelling, Scots pine took up 23.7?% of the low and 9.1?% of the high amounts of ¹⁵N, while Norway spruce took up 21.5 and 32.1?%, respectively. Both species transported proportions of ¹⁵N to the rhizosphere (0.1–0.2?%) and bulk soil (0.3–0.9?%). The method is a useful tool to investigate the fate of root-derived N in soils, for example, for the formation of stable forms of soil organic matter.     

Distribution of Externally Applied 15NH4 + or 15NO3 − in White Lupins at Different Developmental Stages

White lupins (Lupinus albus L., var. Kievsky mutant) were grown in Mitscherlich pots. ¹⁵NH₄NO₃ or NH₄ ¹⁵NO₃ (10 or 95 at% ¹⁵N exc.) was applied at the late vegetative stage (14–16 leaves) or at the generative stage (end of bloom), respectively. Dry weight increase (ΔDW) of the plants as well as the ¹⁵N distribution in different organs and N fractions (NO_{3 ?}-N, NH₂-N, protein N) were investigated after 5 days and 50 days (maturity). The following results were obtained:

1. In comparison with the ¹⁵N derived from NO₃ ^?, the ¹⁵N derived from NH₄ ⁺ was more strongly retained in the roots. When transported into the shoot, it was more strongly translocated into the tip.

2. More ¹⁵N derived from NH⁴ ₊ was incorporated into proteins and reduced soluble N compounds than ¹⁵N derived from NO₄ ^?. Even in the above-ground plant tissues, a considerable proportion of the latter was found as NO₃ ^?.

3. In the long-term experiment (harvest at maturity 50 days after application), no difference in translocation and incorporation could be found between the two offered ¹⁵N sources.     

Lysimeter Investigations on the Effect of Winter Catch Crops and Weeded Fallow on the N-Dynamics in a Sandy Treposol Soil of Northeast Germany

Abstract

Lysimeter experiments (soil: sandy treposol, from the region “Havelländisches Luch”, Brandenburg, Germany) with application of ¹⁵N labelled fertilizer (80 kg N per ha as ¹⁵NH₄ ¹⁵NO₃, 10 at.-%¹⁵N exc.; for simulating mineralization in the early autumn period) were carried out to determine to what extent the amount of mineral- N was temporary conserved by winter catch crops, taken up subsequently in the vegetation periods by following crops, taken by subsequently in the vegetation periods by following crops, or percolated in the leaching water, respectively. The results were as follows:

1) Until winter or spring respectively, the catch crop uptake rates of applied mineral-N were 32% for phacelia (Phacelia tanacetifolia BENTH.), 25% for winter rape (Brassica napus L. cv. ‘AKELA’), and 16% for white mustard (Sinapis alba L.).

2) In the year after, following maize incorporated from 2.1 to 4.5% of the fertilizerborne N. The following plant community of fallow took up from 0.2 to 0.5% N originating from the fertilizer-N.

3) In comparison with the catch crops, N-leaching losses under fallow conditions were highest and equivalent to 17% of the applied fertilizer-N amount. In contrast to 3% of white mustard, phacelia and winter rape reduced N-leaching losses to 0.2 and 0.3% of the applied fertilizer-N amount.

4) In spring of the first year after the beginning of investigations, N-leaching losses were highest under fallow conditions and white mustard cultivation. Thus, the amounts of nitrate losses would exceed the EU limit for drinking water.

5) Three years after the investigations had been started, 10% (white mustard) and 20% (fallow) of the applied fertilizer-N was still found in th lysimeter soil.     

Assessing the subsequent effect of nitrogen released from tobacco-waste on maize crop using a 15N isotope technique

The investigation of the residual effect of nitrogen (N) released from tobacco-waste (TW) using isotope techniques will provide valuable data for sustainable organic farming. For this aim, a pot experiment was conducted using the ¹⁵N isotope technique. The experiment was based on a completely randomised design with four replications and was conducted on a calcareous ustochrepts soil. TW at levels of 0, 10, 20, 30 and 40 t ha^?1 and N fertiliser as (NH₄)₂SO₄ at levels of 0, 20, 40, 60 and 80 kg N ha^?1 were used for the Bezostaja-1 wheat variety. Concerning mineral N fertilisation with 20 and 80 kg N ha^?1, additional treatments with ¹⁵N-labelled (NH₄)₂SO₂ (10 at.% exc.) have been applied. Following harvesting wheat plants, the Pioneer 3377 maize variety was used to see the residual effect of TW. After harvesting, dry matter yields were recorded and total N concentrations were determined. ¹⁵N determinations and calculations were also made for ¹⁵N treatments separately. TW had a significant residual effect on the growth of corn plant under the pot condition. Increasing rates of TW significantly increased the dry matter yield of corn plant following wheat from 3.31 t ha^?1 (at control) to 7.89 t ha^?1 (at the TW treatment of 40 t ha^?1). The ¹⁵N values derived from the ¹⁵N fertiliser decreased with increasing TW application. The average values of N derived from N fertiliser (Ndff) varied from 2.14 to 3.09% at the rates of 20 and 80 kg N ha^?1, respectively. However, N derived from TW (Ndftw) significantly increased from 16.93 to 24.59% (at 20 kg N ha^?1), and it also increased from 23.06 to 28.15% (at 80 kg N ha^?1) with increasing TW applications from 20 to 40 t ha^?1, respectively.     

15N-Labelled Ammonium and Nitrate Uptake by the Grass Calamagrostis villosa

Abstract

Calamagrostis villosa dominates the understory vegetation in declining spruce forests at higher elevations of the Central European mountain areas which show symptoms of needle yellowing and associated magnesium (Mg) deficiency. It was hypothesized that grasses would preferentially take up nitrate-nitrogen (NO₃-N) over ammonium-nitrogen (NH₄-N) which would support the cation balance in Mg deficient soils. In order to test this hypothesis, growth experiments were carried out in the greenhouse using plants which were cultivated in sand for nine weeks with full nutrient solution containing 0.2 or 2 mmol of N with different NH₄ ⁺ to NO₃ ^? ratios (1:0, 0.5:0.5, 0:1). In a short term experiment with labelled ¹⁵NH₄ ⁺ and ¹⁵NO₃ ^?, uptake of NH₄ ⁺ and NO₃ ^? was measured. When NO₃ ^? was the only N source it was taken up at similar rate per g dry mass as in the experiment in which NH₄ ⁺ was the only N source. However, at high supply pure NO₃ ^? nutrition resulted in higher biomass. In contrast, supply of only NH₄ ⁺ caused accumulation of N in the roots but growth remained restricted. If NH₄ ⁺ and NO₃ ^? were supplied at equal amounts, NH₄ ⁺ was the preferred form for N uptake. Biomass of the plants with mixed supply did not differ from the plants with pure NO₃ ^? nutrition.

The results point to an interesting interaction of carbon and nitrogen relation, but they do not support the initial hypothesis that grasses may prefer NO₃ ^? over NH₄ ⁺.     

Conference Reports

Abstract

One purpose of new land use concepts for degraded fens (organic soils with high N content) is the reduction of the mineralization process due to very high groundwater levels. However, knowledge of nitrogen mineralization process (net and gross) in degraded fen soils affected by reflooding is very small. Therefore, the objectives of our study were (a) to evaluate the suitability of ¹⁵N pool dilution method for measurements of gross mineralization rates in degraded fen soils and (b) to investigate how the reflooding of a degraded fen affects the net and gross nitrogen mineralization in a short-term incubation experiment. The usability of the ¹⁵N pool dilution method was diminished by the low recovery of the applied ¹⁵NH₄ ^? at time zero. The recovery of the added ¹⁵NH₄ ^? in the extractable soil NH₄ ^? pool was only 13.5% for the drained soil and 59.6% for the reflooded soil. However, the gross mineralization rates were similar for both soils and exceeded always the net rates substantially. The cumulative net mineralization rate was higher for the reflooded soil (1.58 μg N?cm^?3?d^?1) than for the drained soil (-0.67 μg N?cm^?3?d^?1). Differences between the two soils were also found in the nitrification intensity and the loss of ¹⁵N. This was probably one reason for the higher net mineralization rate in the reflooded soil.     

Uptake of 15NH3 by Picea abies in Closed Chamber Experiments

Abstract

Above-ground deposition of anthropogenic trace gases like NH₃ and NO_x is considered as a main factor for nitrogen (N) loading of Picea abies ecosystems. In order to quantify NH₃ deposition, tracer experiments with ¹⁵N labelled NH₃ were carried out in fumigation chambers (GSF München).

NH₃ uptake is linearly related to the gas concentration in the air, but the relation differs between organs and depends on N-nutrition of the organs. Plants well supplied with N have a lower NH₃ uptake per g dry weight then plants deprived of N. Only a small amount of the offered gas deposits to the external plant surfaces. The NH₃ uptake rates of spruce indicate that NH₃ may be regarded as being just as or even more important as environmental pollutant than NO_x with respect to N loading of spruce ecosystems.     

The Influence of Ammonium on Nitrate Uptake and Assimilation in 2-Year-Old Ash and Oak Trees - A Tracer-Study with 15N

Abstract

Interactions between ammonium and nitrate as competitive N sources depend on various biotic and abiotic factors. The preference for one of these N sources and the influence of ammonium on nitrate uptake and nitrate reductase activity was investigated in a ¹⁵N labelling experiment using 2-year-old potted plants of ash (Fraxinus excelsior L.) and oak (Quercus robur L.) under greenhouse conditions.

Seedlings of both tree species use ammonium and nitrate in equal amounts when both N forms are supplied in a 1:1 ratio (1.5 mM NH₄ ⁺ + 1.5 mM NO₃ ^?), although there is a slight tendency that ammonium is preferred. In both species total N uptake is higher if ammonium and nitrate are supplied simultaneously when compared with uptake of nitrate alone (3 mM nitrate). If nitrate is the sole N source N uptake is only half as high as if ammonium and nitrate are supplied in a ratio of 1:1.

The distribution of nitrate reductase between shoot and roots is not influenced by the N-form: nitrate reductase activity is always highest in the roots of both species under the conditions of this experiment.

Xylem sap analyses showed that both species transport higher concentrations of amino acids than of nitrate from the roots to the shoot. The amino acid composition is independent of the type of N source. Furthermore, ash trees contain more nitrate in the xylem sap than oak trees, reflecting the higher N uptake and the higher nitrate reductase activity in the leaves of this species.     

Short-term carbon dynamics in a temperate grassland and heathland ecosystem exposed to 104 days of drought followed by irrigation

Temperate ecosystems are susceptible to drought events. The effect of a severe drought (104 days) followed by irrigation on the plant C uptake, its assimilation and input of C in soil were examined using a triple ¹³CO₂ pulse-chase labelling experiment in model grassland and heathland ecosystems. First ¹³CO₂ pulse at day 0 of the experiment revealed much higher ¹³C tracer uptake for shoots, roots and soil compared to the second pulse (day 44), where all plants showed significantly lower ¹³C tracer uptake. After the third ¹³CO₂ pulse (day 70), very low ¹³C uptake in shoots led to a negligible allocation of ¹³C into roots and soil. During irrigation after the severe drought, the ¹³C tracer that was allocated in plant tissues during the second and third pulse labelling was re-allocated in roots and soil, as soon as the irrigation started. This re-allocation was higher and longer lasting in heathland compared to grassland ecosystems.     

Distribution and Utilization of 15N in Cowpeas Injected into the Stem Under Influence of Water Deficit

Abstract

Investigations were carried out on Vigna unguiculata L. Walp. to estimate the distribution and utilization of ¹⁵N in different organs after stem injection during vegetative, flowering and pod filling stage. During flowering effects of water deficit were also examined. In well watered plants, within 4 days after injection, 65% of ¹⁵N accumulated in leaves. This was drastically reduced to 42% by water deficit. ¹⁵N accumulation in stems increased under water deficit. The translocation of ¹⁵N from the stem base to roots were not altered by water deficit. During pod filling 62% of recovered ¹⁵N in the plants had accumulated in seeds, 24% in leaves and 11% in stems within 4 days, whereas the uptake of nitrogen in pod walls and roots remained low (2%). These results demonstrate that the method of injecting very small quantities (1 mg/plant) of ¹⁵N into the stem base allows an exact and detailed quantitative assessment of N translocation/distribution with regard to different organs, different growth stages and different treatments.     

Der [15N]Methacetin-Leberfunktionstest zum Nachweis von Arzneimittelnebenwirkungen. Antibiotika-Therapie mit Amplicillin und mit Gefotaxime bei Neugeborenen

Abstract

The effect of soil temperature and moisture on plant growth and mineralisation of organic residues was investigated using ¹⁵N-labelled soybean residues and temperature-controlled tanks in the glasshouse. Treatments were arranged in a factorial design with: three soil temperatures (20, 26 and 30°C), two soil moisture regimes (8% (–800 Kpa) or 12% (–100 Kpa)), soybean residues added (enriched at 1.82 atom % ¹⁵N excess) or no residues; and either sown with ryegrass or not sown. Pots were sampled six weeks after planting and ¹⁵N-enrichment and δ¹³C of the plant and soil fractions were determined. Soil inorganic N was also periodically measured.

Available inorganic N increased significantly with addition of residues and generally decreased with increasing temperature. Plant dry matter decreased significantly with increase in soil temperature and increased with increasing moisture. Root-to-shoot ratio declined with increased temperature and moisture. Percentage nitrogen derived from residues (%Ndfr) increased linearly with increased temperature and moisture. Δ¹³C decreased linearly with increasing temperature and decreasing moisture status. There was a significant correlation between transpiration and dry matter production, but there was no correlation between water use efficiency and Δ¹³C.

The results suggest that C: N ratio of the root material effects the root turnover and in turn the water supply capacity of the root system.     

Using the natural 15N abundance to assess the main nitrogen inputs into the sand dune area of the North-Western Negev desert (ISRAEL)

The variation of the natural ¹⁵N abundance is often used to evaluate the origin of nitrogen or the pathways of N input into ecosystems. We tried to use this approach to assess the main input pathways of nitrogen into the sand dune area of the north-western Negev Desert (Israel). The following two pathways are the main sources for nitrogen input into the system:

1. Biological fixation of atmospheric nitrogen by cyanobacteria present in biological crusts and by N₂-fixing vascular plants (e.g. the shrub Retama raetam);

2. Atmospheric input of nitrogen by wet deposition with rainfall, dry deposition of dust containing N compounds, and gaseous deposition.

Samples were taken from selected environmental compartments such as biological crusts, sand underneath these crusts (down to a depth of 90?cm), N₂-fixing and non-N₂-fixing plants, atmospheric bulk deposition as well as soil from arable land north of the sandy area in three field campaigns in March 1998, 1999 and 2000. The δ¹⁵N values measured were in the following ranges: grass ?2.5‰ to +1.5‰; R. reatam: +0.5‰ to +4.5‰; non-N₂-fixing shrubs +1‰ to +7‰; sand beneath the biological crusts +4‰ to +20‰ (soil depth 2–90?cm); and arable land to the north up to 10‰. Thus, the natural ¹⁵N abundance of the different N pools varies significantly. Accordingly, it should be feasible to assess different input pathways from the various ¹⁵N abundances of nitrogen. For example, the biological N fixation rates of the Fabaceae shrub R. reatam from the ¹⁵N abundances measured were calculated to be 46–86% of biomass N derived from the atmosphere. The biological crusts themselves generally show slight negative ¹⁵N values (?3‰ to ?0.5‰), which can be explained by biological N fixation. However, areas with a high share of lichens, which are unable to fix atmospheric nitrogen, show very negative values down to ?10‰. The atmospheric N bulk deposition, which amounts to 1.9–3.8?kg?N/ha?yr, has a ¹⁵N abundance between 4.4‰ and 11.6‰ and is likely to be caused by dust from the arable land to the north. Thus, it cannot be responsible for the very negative values of lichens measured either. There must be an additional N input from the atmosphere with negative δ¹⁵N values, e.g. gaseous N forms (NO _x , NH₃). To explain these conflicting findings, detailed information is still needed on the wet, particulate and gaseous atmospheric deposition of nitrogen.     

Dinitrogen Fixation of Microbe-Plant Associations as Affected by Nitrate and Ammonium Supply

Abstract

The dinitrogen fixation activity of Azospirillum sp., and Pantoea agglomerans strains was determined by ¹⁵N₂ incorporation after incubation with ¹⁵N₂ labeled air or/and by acetylene reduction. These bacterial strains were able to fix N₂ both in pure culture and in association with wheat plants in hydroponics. Nitrogenase activity of Azospirillum sp., in pure culture was more rapidly inhibited by the addition of NH₄ ⁺ than NO₃ ^?. The N₂ fixation of P. agglomerans decreased only by NH₄ ⁺ -addition, but was stimulated by NO₃ ^?. Nitrogen fixation in association with wheat plants remained unaffected by both N compounds. However, nitrogen derived from the atmosphere (N_dfa) contributed only very little to the overall nitrogen nutrition of the plants.     

The Impact of Ozone on the 15N Incorporation and Nitrogen Assimilation of Wheat and Maize

Abstract

Young wheat (C3) and maize (C4) plants were exposed to near-ambient concentrations of ozone in open-top chambers in order to investigate the possible effects of ozone on nitrogen metabolism. Nitrogen was supplied to the plants by adding ¹⁵N-labelled tracer substances via the soil substrate. Enzyme activities (NADH nitrate reductase, nitrite reductase, glutamine synthetase and NADH glutamate dehydrogenase) and the incorporation of ¹⁵N were determined.

The findings show that nitrogen metabolism was affected by O₃, however, there were distinct differences between the two species. In plants treated with O₃, NADH nitrate reductase activity in maize leaves was reduced, while NR activity in wheat leaves only slightly declined. Only minor changes were observed with respect to the activities of nitrite reductase, glutamine synthetase and NADH glutamate dehydrogenase.

Feeding experiments using ¹⁵NO₃ ^? showed that the incorporation of nitrate nitrogen in wheat plants exposed to ozone remains virtually unchanged, whereas in maize plants reduced incorporation rates were observed for nitrate nitrogen. The incorporation of ammonium nitrogen was distinctly increased in wheat and maize by the impact of ozone.

When investigating pigment contents, reduced levels of chlorophyll a and b and carotenoids were observed, whereas the pigment content of wheat leaves remained unchanged. These results indicate that young maize plants are more susceptible than wheat plants to short-term ozone exposure.     

The MICE facility – a new tool to study plant–soil C cycling with a holistic approach

Plant–soil interactions are recognized to play a crucial role in the ecosystem response to climate change. We developed a facility to disentangle the complex interactions behind the plant–soil C feedback mechanisms. The MICE (‘Multi-Isotope labelling in a Controlled Environment’) facility consists of two climate chambers with independent control of the atmospheric conditions (light, CO₂, temperature, humidity) and the soil environment (temperature, moisture). Each chamber holds 15 plant–soil systems with hermetical separation of the shared above ground (shoots) from the individual belowground compartments (roots, rhizosphere, soil). Stable isotopes (e.g. ¹³C, ¹⁵N, ²H, ¹⁸O) can be added to either compartment and traced within the whole system. The soil CO₂ efflux rate is monitored, and plant material, leached soil water and gas samples are taken frequently. The facility is a powerful tool to improve our mechanistic understanding of plant–soil interactions that drive the C cycle feedback to climate change.     

Nitrogen Isotope Ratios in Different Compartments of a Mixed Stand of Spruce,Larch and Beech Trees and of Understorey Vegetation Including Fungi

Abstract

Natural nitrogen isotope ratios were measured in different compartments (needles or leaves and twigs of different age classes and crown positions, roots and soil of different horizons) of spruce (Picea abies), larch (Larix decidua) and beech (Fagus sylvatica) trees in an 11-year-old mixed stand in the Fichtelgebirge, NE Bavaria, Germany. In addition, samples of understorey vegetation (mainly ericaceous shrubs and grass) and of ectomycorrhizal and saprophytic fungi were analyzed. The δ¹⁵N values found for all samples ranged between ?7.5 and + 4.5‰. No significant differences were found for the nitrogen isotope ratios of the three tree species despite of their evergreen versus deciduous foliage and despite of their different rooting depth. Ericaceous shrubs had the most negative and fungi and soil from the mineral horizon the most positive δ¹⁵N values. Positive δ¹⁵N values of the fungi indicate their ability to utilize organic soil nitrogen, but the data do not unequivocally show that plants forming mycorrhizas profit from this organic nitrogen source.     

Inkorporation von 15N-markiertem Harnstoff in Organogene Dünge- und Abfallstoffe während der Rotte

Abstract

Eight organic fertilizers and wastes enriched with ¹⁵N labelled urea were stored at 25°C for one year. At the end of the experiment the ¹⁵N recovery rate ranged between 24 and 100%. The distributions of inorganic nitrogen (NH₄- and NO₃-N) and organic nitrogen (fulvic acids, humic acids and non extractable substances) are ascertained. Between the test materials, there are great differences in incorporation parameters.     

In vivo NMR spectroscopy: in situ 15N pulse labelling NMR spectroscopy with photoautotrophic microorganisms

For studying the nitrogen metabolism in plants ¹⁵N NMR spectroscopy can be used. For in vivo ¹⁵N NMR (natural abundance of ¹⁵N: 0.37%) enrichment of the sample with the isotope ¹⁵N is compulsory. The detection of time courses of ¹⁵N assimilation from cells, which are enriched in culture is restricted in scope. Here, a method, the ¹⁵N pulse labelling NMR spectroscopy, is demonstrated, which permits labelling of different nitrogen compounds in photoautotrophic microorganisms during the NMR spectroscopic measurement. Using an effective illumination system it is possible to maintain photosynthesis in plant samples of high biomass densities in the magnet necessary for ammonia assimilation. The technique thus enables to directly observe ammonia assimilation pathways by application of a ¹⁵NO₃ ^? or ¹⁵NH₄ ^? pulses.

Für das Studium des Stickstoffstoffwechsels der Pflanzen kann die ¹⁵N-NMR-Spektroskopie herangezogen werden. Hierzu ist bei der in-vivo-¹⁵N-NMR (natürliche Häufigkeit von ¹⁵N: 0.37%) eine Anreicherung der Probe mit dem Isotop ¹⁵N unerläßlich. Eine Verfolgung der ¹⁵N-Assimilationskinetik mit Zellen, die in der Kultur angereichert wurden, ist jedoch nur bedingt möglich. In dieser Arbeit wird die ¹⁵N-Pulsmarkierungs-NMR-Spektroskopie als eine Methode vorgestellt, die es erlaubt, eine Markierung von Stickstoffverbindungen in photoautotrophen einzelligen Mikroorganismen während der NMR-Messung im Magneten vorzunehmen. Es wird ein spezielles Beleuchtungssystem verwendet, das eine für die Stickstoffassimilation ausreichende Photosyntheseleistung der Zellen unter NMR-Bedingungen bei hoher Biomassedichte ermöglicht. Diese Technik erlaubt durch die Applikation eines ¹⁵NO₃ ^?-oder ¹⁵NH₄ ⁺-Pulses eine direkte Verfolgung von Ammonium-Assimilationswegen.     

A Dual 13C and 15N Long Term Labelling Technique to Investigate Uptake and Translocation of C and N in Beech (Fagus sylvatica L.)

Abstract

A continuous dual ¹³CO₂ and ¹⁵NH₄ ¹⁵NO₃ labelling experimental set-up is presented that was used to investigate the C and N uptake and allocation within 3-year old beech (Fagus sylvatica L.) during one growing season. The C and N allocation pattern was determined after six, twelve and eighteen weeks of growth. The carbon uptake was distinctly different in the three phases examined: The first six weeks after budbreak were dedicated to leaf growth with a R/S (root to shoot) ratio of 0.14 for the new carbon. The second growth phase showed a balanced R/S ratio of C allocation and after week 13, the root compartment was the main carbon sink (R/S = 6.97).

Nitrogen allocation was more basipetal as compared to carbon. In the second growth phase, R/S of N_new was 5.57 but fell to 3.54 for the third growth phase probably due to formation of reserves in buds and stem.