| Title Information | |
* Auerswald, Karl, Prof. Dr., Technische Universität München, Lehrstuhl für Grünlandlehre, Freising
Bäumler, Rupert, Prof. Dr., Universität Erlangen, Institut für Geographie, Erlangen
* Flessa, Heiner, apl. Prof. Dr., Universität Göttingen, Institut für Bodenkunde und Waldernährung, Göttingen
Gattinger, Andreas, Dr., GSF-Forschungszentrum für Umwelt und Gesundheit, Institut für Bodenökologie, Oberschleißheim
* Gebauer, Gerhard, Prof. Dr., Universität Bayreuth, Lehrstuhl für Pflanzenökologie, Bayreuth
* Giesemann, Anette, Dr., Bundesforschungsanstalt für Landwirtschaft (FAL), Institut für Agrarökologie, Braunschweig
Gietl, Christine, Priv.-Doz. Dr., Technische Universität München, Lehrstuhl für Botanik, Biologikum, Freising
Haber, Wolfgang, Prof. Dr., Technische Universität München, Lehrstuhl für Landschaftsökologie, Freising
Haider, Konrad, Prof. Dr., Deisenhofen
Hoppe, Brigitte, Prof. Dr., c/o Universität München, Geschichte der Naturwissenschaften, München
Horacek, Micha, Mag., ARCS Research GmbH, Abteilung Umweltforschung, Seibersdorf
* Horn, Peter, Prof. Dr., Bayerische Staatssammlung für Paläontologie und Geologie, München
* Leuenberger, Markus, Priv.-Doz. Dr., Universität Bern, Physikalisches Institut, Bern
* Lüttge, Ulrich, Prof. emer., Technische Universität Darmstadt, Institut für Botanik, Darmstadt
Meckenstock, Rainer, Priv.-Doz. Dr., GSF-Forschungszentrum für Umwelt und Gesundheit, Institut für Grundwasserökologie, Oberschleißheim
Melzer, Arnulf, Prof. Dr., Technische Universität München, Limnologische Station, Iffeldorf
Muhr, Jan, Universität Bayreuth, Lehrstuhl für Pflanzenökologie, Bayreuth
Nöth, Heinrich, Prof. Dr., Präsident der Bayerischen Akademie der Wissenschaften, München
Rehfuess, Karl Eugen, Prof. Dr., Technische Universität München, Dept. für Ökologie, Freising
* Rossmann, Andreas, Priv.-Doz. Dr., isolab GmbH, Laboratorium für Stabile Isotopen, Schweitenkirchen
Schmederer, Josef, ORR Dipl.-Geol., Bayer. Landesamt für Wasserwirtschaft, Referat Hydrogeologie und Grundwasserschutz, München
* Schmidt, Hanns-Ludwig, Prof. emer. für Allgemeine Chemie und Biochemie, Landshut
* Schnyder, Hans, Prof. Dr., Technische Universität München, Lehrstuhl für Grünlandlehre, Freising
Seiler, Klaus-Peter, Prof. Dr., GSF-Forschungszentrum für Umwelt und Gesundheit, Geschäftsführung, Oberschleißheim
* Struck, Ulrich, Priv.-Doz. Dr., Universität München, GeoBio-CenterLMU, München
Ziegler, Hubert, Prof. Dr., Vorsitzender der Kommission für Ökologie, Bayerische Akademie der Wissenschaften, München
Von fast allen chemischen Elementen in der Natur existieren verschiedene, unterschiedlich schwere Formen (Isotope), die sich nur in der Anzahl ihrer Neutronen unterscheiden. Es wird unterschieden zwischen radioaktiven Isotopen, die nach einer charakteristischen Zeit zerfallen, und stabilen Isotopen. Letztere sind Gegenstand dieses Berichtbandes, wobei vor allem die stabilen Isotope des Kohlenstoffs (C), Sauerstoffs (O), Wasserstoffs (H), Stickstoffs (N) und Schwefels (S) sowie der schweren Elemente Neodym (Nd), Strontium (Sr) und Blei (Pb) im Vordergrund der Betrachtungen stehen.
Die Isotope eines Elements verhalten sich chemisch gleich, reagieren aber physikalisch etwas unterschiedlich. Durch die Anreicherung bzw. Abreicherung eines Isotops entstehen bei vielen biologischen oder chemischen Prozessen in der Natur charakteristische, quantitativ erfassbare und gut interpretierbare Muster, so genannte »isotopische Fingerabdrücke«. Die Analyse stabiler Isotope ist daher zu einem bedeutenden Werkzeug in allen Bereichen ökologischer Forschung geworden. Mit Hilfe der Verhältnisse 18O/16O und 15N/14N in Eisbohrkernen kann beispielsweise auf Klimaänderungen in der Vergangenheit geschlossen werden und das Verhältnis der Kohlenstoffisotope 13C/12C in Pflanzenproben erlaubt Rückschlüsse auf deren Photosynthesemechanismen und Wachstumsbedingungen. Auch viele sonst untrennbar ineinander verwobene Prozesse können mit Hilfe der Analyse stabiler Isotope identifiziert und quantifiziert werden. Dies trägt wesentlich zum Verständnis der Prozesse und Wechselwirkungen innerhalb komplexer biologischer und ökologischer Systeme bei.
Der vorliegende Berichtband zu der gleichnamigen Tagung »Auf Spurensuche in der Natur: Stabile Isotope in der ökologischer Forschung« (veranstaltet von der Kommission für Ökologie der Bayerischen Akademie der Wissenschaften) zeigt anhand einiger ausgewählter Beispiele die große Bedeutung und einige der vielfältigen Anwendungsmöglichkeiten dieser Analysenmethode auf.
Karl Auerswald, Wolfgang Haber, Hubert Ziegler
Hanns-Ludwig SCHMIDT: Fundamentals, systematics, and importance of isotope discriminations in biological systems
[11 pp., 6 black-and-white figures]
Non-statistical isotope distributions of the bioelements in the living Nature are primarily basing on isotope discriminations by thermodynamic isotope effects on primary compounds in their natural cycles; this is exemplarily demonstrated for the natural water cycle. Within biological systems preferably isotope effects on enzyme catalysed reactions are the main cause for the formation of intermolecular and intramolecular non-statistical isotope distributions.
In vivo, thermodynamic isotope effects can only become efficient, when a stationary state of the metabolism is at least transiently attained, kinetic isotope effects are only realized in context with branching events of the metabolism. This is outlined for the C-isotope distribution between and within individual natural plant compounds. The systematics of the O- and H-isotope distributions in natural compounds are derived, and their importance for the elucidation of biosyntheses of natural compounds and their discriminations from synthetic analogues is demonstrated. Correlations between synthesis and isotopic patterns of nitrate and nitrous oxide and ecological questions are outlined.
The examples shall demonstrate that the systematics of isotope separations on the molecular level will permit to better understand, interpret and use global isotope discriminations in living systems.
Markus LEUENBERGER: Stable isotopes of polar ice cores give climatic information
[16 pp., 11 coloured and 4 black-and-white figures, 1 table]
Ice cores carry a wealth of climatic information, that are temporally well constraint and generally accessible with high precision. Water isotope ratio can be measured relatively easy with high precision and yield a first impression about former variations of the local temperature. However, attention must be paid to transfer water isotope ratio variations into a temperature evolution, because there are additional parameters that influence the isotopic composition such as the source temperature and the seasonal distribution of precipitation. Here a new temperature proxy can be very helpful, nitrogen isotope ratios that are driven by gravitation enrichment and thermal diffusion. This new proxy is in particular useful to explore large and rapid temperature jumps as present as the so-called Dansgaard-Oeschger events. Measurements performed on NorthGRIP ice revealed temperature jumps in the range of 8-15 degree Celsius for Dansgaard-Oeschger events 8-17. The associated precision is about 3 degrees. Deviations from the relationship between water isotope ratios and local temperature found by Dansgaard can principally be explained in two ways. (1) Through an additional source temperature change on top of the change due to the change between glacial and Holocene climate regimes, and (2) through a change in the seasonal distribution of precipitation. Besides the parallel behavior of water isotopes and temperature, we found a good agreement between methane concentrations and temperature. However, different temperature sensitivities have been found here as well. This could point to different sources or to temporally varying strengths of certain sources.
Ulrich STRUCK und Falk POLLEHNE: Nitrogen isotopes in sediments of lakes and coastel zones as an indicator for the influence of eutrophication
[19 pp., 5 black-and-white figures]
As a consequence of enhanced use of fertilizers in agriculture many coastal and lake ecosystems changed their trophic state. Until recently the legislative response to these problems focused mainly on the reduction of fertilizers in industrial and human waste waters. A major source of limnic and coastal eutrophication, the excessive use of fertilizers in agriculture, has just been started to be regulated in the last decade.
In unaffected terrestrial ecosystems inorganic nutrients such as nitrogen are often a limiting factor for plant growth. The main source of nitrogen for those ecosystems is the huge N pool in the atmosphere. The nitrogen isotope signature (δ15N) of atmospheric N has a value of 0 ‰. Fertilizer nitrogen has the same N source and shows roughly the same δ15N signature as air nitrogen. As fertilisation of agricultural land exceeds the nitrogen demand of the crop, these plants discriminate the nitrogen pool by taking up the lighter isotope (14N) and leaving the heavier (δ15N, values up to 10-80 ‰) to accumulate in the soil. The evaporation of ammonium from manure, used as fertilizer, is a discriminating step as well, that stripes lighter isotopes and leaves an isotopically higher N residue. This enriched pool will eventually be transported via surface runoff and groundwater to the river systems and will be further transported to lakes and the coastal zone. In consequence plants and other organisms in eutrophied ecosystems display enriched δ15N values, which are also preserved in organic sediments of these areas. Sedimentary nitrogen isotope records in dated cores from the Baltic Sea show increasing δ15N values after the 1920s (from 2 ‰ to more than 12 ‰ today). This pattern becomes less pronounced with increasing distance to the coast. A similar pattern was found in a sediment core from the Bavarian lake Chiemsee investigated recently. Here the sediments are enriched in 15N after about 1930 with a maximum of 7 ‰ during the late 1960s. A sediment core from the unaffected lake Alat near Füssen in Bavaria shows no increased values throughout. This could be expected, as the lake receives no water from areas under agricultural use and thus shows no impact of eutrophication. The process is reversible as the example of Chiemsee shows. The successful reduction of nutrient loads in the lake Chiemsee due to a ring tiling around the lake is already visible in the δ15N signature in lake surface sediments.
Gerhard GEBAUER: Changing Partners in the dark forest – stable isotopes provide a new insight into the nutrition of orchids
[13 pp., 6 coloured- and 2 black-and-white figures, 3 tables]
Most plants are forming a close partnership with fungi in their rhizosphere. In this mycorrhizal symbiosis, plants usually provide their fungal partners with carbohydrates from the photosynthesis and receive mineral nutrients, which are more efficiently being taken up from the soil through the fungal mycelium. This mutualistic arrangement has been subverted worldwide by a few hundreds of plant species that are free from chlorophyll and thus lack the ability to photosynthesize. This nutrition at the cost of the fungal partner is called mycoheterotrophy. The most numerous examples of this behaviour are found among the orchid family. Although chlorophyll free orchid species are known to be mycoheterotrophic, adult green orchids are still thought to be fully autotrophic. Recent data from stable carbon and nitrogen isotope abundance analyses, however, provide evidence that some of the putatively autotrophic orchids live partially at the cost of the fungal partners. This partial mycoheterotrophy is associated with a change of the fungal partner and explains how orchids can thrive into the deepest shade of our forests.
Ulrich LÜTTGE: Physiological ecology of photosynthesis: aut-ecological and syn-ecological aspects on the basis of δ13C and δ18O data
[14 pp., 3 black-and-white figures, 2 tables]
Photosynthesis is the basis of the primary production of biomass in all ecosystems. Changes in the signature of stable isotopes in the biomass as compared to the inorganic substrates of the non living environment – especially the carbon dioxide in the atmosphere – which are relevant to photosynthesis occur at different levels, such as diffusion, enzyme reactions of metabolism, and in relation to genetically anchored photosynthetic physiotypes of plants. All of this is under the influence of external ecological conditions. Thus, isotope signatures provide traces of how plants react to external conditions in habitats and ecosystems. Physiological aut-ecology of individual organisms and species documents their reactions. Conversely, the different plants also determine their habitats and ecosystems. Besides a diversity of life forms and species of plants we also observe an ecophysiological diversity which is mirrored in stable isotope signatures. Physiological syn-ecology provides overviews. Thus, isotope signatures support the evaluation of natural and man made ecosystems for conservation and management in agriculture and forestry.
Hans SCHNYDER und Rudi SCHÄUFELE: 13C and 18O signatures of CO2 – markers for CO2 fluxes in ecosystems?
[9 pp., 7 black-and-white figures]
Terrestrial ecosystems play a critical role in the global C budget. Photosynthesis and respiration are the largest components of the C budget, but they can not be separated and quantified using conventional techniques – hampering progress in the understanding of the C economy of ecosystems. However, the photosynthetic and respiratory CO2 fluxes may be partitioned on the basis of different stable isotope signatures of the CO2 (13C and 18O). But, the stable isotope signatures of the net CO2 flux and flux components may vary significantly over time. At present the mechanisms underlying these fluctuations are not understood properly. Also field measurements are constrained by large logistic demands.
We have developed a mobile on-line isotope-ratio mass spectrometer system which allows near-continuous measurements of 13C and 18O in CO2. The paper presents data demonstrating the dynamics of 13C and 18O in CO2 above grassland during a diurnal cycle, and discusses the potential of these data.
Karl AUERSWALD, Michael SCHWERTL, Rudi SCHÄUFELE und Hans SCHNYDER: Let the sheep do the sampling – animal hairs as a tool for ecosystem analysis
[12 pp., 7 black-and-white figures, 1 table]
Ecosystems are characterized by their size, heterogeneity and continuous change. These properties cause difficulties with most conventional measuring methods. Stable isotopes of bio-elements may serve as an elegant alternative, because their fractionation directly indicates underlying processes and can be interpreted quantitatively. In grassland ecosystems the analysis of hairs from grazing animals offers the additional advantage that the grazing animal integrates over the grazed area and thus dampens small-scale heterogeneity. This allows the detection of even weak ecosystem signals, which otherwise would disappear in the noise of heterogeneity. Furthermore, hair provides an archive, which can be read retrospectively and chronologically. This allows analyzing pronounced seasonal fluctuations even with only few sampling dates. As an example, this is demonstrated by quantifying the effect of water deficiency on photosynthesis, where water deficiency varied in space due to soil heterogeneities and in time due to weather. This effect became clearly visible (r2 = 0.91) although it only caused a change of 1.5 ‰ in biomass 13C signature. In addition, the effect of peat degradation and subsequent CO2 release could also be detected although this effect caused a shift of only 0.4 ‰. The analysis of hairs from grazing animals thus can serve as a valuable tool in ecosystem analysis.
Heiner FLESSA: Storage of carbon in soils – analysis on the basis of stable carbon isotopes
[13 pp., 8 black-and-white figures, 1 table]
Soil organic matter is a central element in the global carbon (C) cycle and it influences nearly all soil properties and functions. In soils where a change from C3 to C4 plants or vice versa has occurred, the natural abundance of 13C and 12C in soil organic matter, in dissolved and gaseous decay products of soil organic matter, and in different soil organic matter fractions provides detailed information on the processes of C stabilization and C transformation in soils. We present two studies which were conducted on fields with long-term maize cropping. The δ13C(PDB) values of the soil organic matter and its decay products were used to quantify stabilization of maize carbon in different soil organic matter fractions and to determine the function of these fractions as a source of CO2 and dissolved organic carbon (DOC).
Anette GIESEMANN: Tracing sulphur: stable sulphur isotopes in ecological research
[11 pp., 5 black-and-white figures, 2 tables]
Sulphur (S), a major plant nutrient to all organisms, is turned over on a global scale. To analyse exchange processes between compartments of an ecosystem, stable sulphur isotope analysis is used. Depending on their origin, samples differ in their isotopic composition and hence pools characterised by their sulphur isotopic composition occur in ecosystems. During industrial processes, sulphur in form of SO2 is often delivered to the atmosphere and deposited in ecosystems in very high amounts, which causes damage on e.g. plants. Stable S isotope analysis allowed to trace sulphur of atmospheric origin in an ecosystem even when it is deposited at subnecrotic levels. Furthermore, sulphur containing fertilizers were under evaluation, and translocation as well as use of fertilizer derived sulphur could be evaluated successfully using stable isotope analysis.
Peter HORN: Isotope signatures of heavy elements in ecological research and practice
[22 pp., 6 black-and-white figures, 1 table]
Chemical elements in rocks and soils, such as strontium and lead, may show natural spatial variations in their isotope abundance ratios 87Sr/86Sr, and 206,207,208Pb/204Pb, which reflect the local geological and lithological settings. Carried by water they can be taken up by plants and animals, and thereby enter the food chains. As they are persistent and conservative they can be used to determine the provenance of food stuffs and to trace and reconstruct pathways of the elements and their compounds in human environments.
Possible natural and anthropogenic influences on the specific isotope ratios of heavy elements will be discussed. Examples in applying 87Sr/86Sr, and 206Pb/207Pb – 208Pb/207Pb will be presented to demonstrate the potential of the method. Further isotope pairs, namely 143Nd/144Nd and 234U/238U, which may find applications in ecological research, will also be described.
Andreas ROSSMANN: Mislabelling? Stable isotope analyses of food products with protected geographical origin
[12 pp., 8 black-and-white figures, 2 tables]
Food products with labelled geographical origin or geographical indication are preferred by consumers and are therefore sold at higher prices as compared to products without such indications. This is especially true for products which have obtained the label "protected denomination of origin" (PDO) by the EU. It is important for those products that they are made in strictly defined regions only from raw materials originating from that region using traditional production methods. The higher price which can be obtained for them make dishonest producers trying to sell such valuable products originating not from expensive raw material of the provenance region, but from cheaper raw materials coming from other regions. This cannot be easily detected by conventional physical-chemical methods of analysis, as the composition of the true and of the imitated product are often the same within the natural variability of the parameters applied. Stable isotope analyses have proved as being able to detect such manipulations, especially if they are applied as multielement stable isotope analyses combining results for the isotopic ratios of light "bio" (H, C, N, O, S) and heavy "geo" (Sr, Pb, Nd) elements.
The proof of the authenticity and the detection of adulteration, respectively, apply the fact that the climatic, geographical and geological conditions of the provenance region, that is the environment, give a unique combination of the multielement isotopic ratios, that is a multielement isotopic fingerprint, to a product, which enables a clear differentiation from products of another region. A prerequisite for the application of the method is a reliable database of authentic samples from the source region, and the knowledge about climate, production methods, and geology, which allows understanding and explaining the isotopic data as measured. The methods of multielement stable isotope analyses of light elements and their progress during the last years play an important role for the practical application of the procedures described. Due to the amount of single data, an evaluation by discriminant analysis has often to be applied, even if in some cases the determination of one or two elements' isotopic ratios can be sufficient to answer the question of origin.
| Copyright © 2012 Verlag Dr. Friedrich Pfeil |
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