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  • 1
    Electronic Resource
    Electronic Resource
    Stable carbon isotopes in tree rings of beech: climatic versus site-related influences (1997)
    Springer
    Trees 11 (1997), S. 291-297 
    Details
    ISSN: 0931-1890
    Keywords: Key words Stable carbon isotopes ; Palaeoclimate ; Fagus sylvatica ; Tree ring ; Precipitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004680050087
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  • 2
    Electronic Resource
    Electronic Resource
    A 13C tracer study to identify the origin of dissolved organic carbon in forested mineral soils (2004)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 55 (2004), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The relative contributions of sources of carbon in soils, such as throughfall, litter, roots, microbial decay products and stable organic fractions, to dissolved organic C are controversial. To identify the origin of dissolved organic C, we made use of a 4-year experiment where spruce and beech, growing on an acidic loam and on a calcareous sand, were exposed to increased CO2 that was depleted in 13C. We traced the new C inputs from trees into dissolved organic C, into water-extractable organic C, and into several particle-size fractions. In addition, we incubated the labelled soils for 1 year and measured the production of dissolved organic C and CO2 from new and old soil C. In the soil solutions of the topsoil, the dissolved organic C contained only 5–10% new C from the trees. The δ13C values of dissolved organic C resembled those of C pools smaller than 50 µm, which strongly suggests that the major source of dissolved organic C was humified old C. Apparently, throughfall, fresh litter and roots made only minor contributions to dissolved organic C. Water-extractable organic C contained significantly larger fractions of new C than did the natural dissolved organic C (25–30%). The δ13C values of the water-extractable organic C were closely correlated with those of sand fractions, which consisted of little decomposed organic carbon. The different origin of dissolved and water-extractable organic C was also reflected in a significantly larger molar UV absorptivity and a smaller natural 13C abundance of dissolved organic C. This implies that the sampling method strongly influences the characteristics and sources of dissolved organic C. Incubation of soils showed that new soil C was preferentially respired as CO2 and only a small fraction of new C was leached as dissolved organic C. Our results suggest that dissolved organic C is produced during incomplete decomposition of recalcitrant native C in the soils, whereas easily degradable new components are rapidly consumed by microbes and thus make only a minor contribution to the dissolved C fraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2003.00578.x
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  • 3
    Electronic Resource
    Electronic Resource
    Correlating δ13C and δ18O in cellulose of trees (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We measured the carbon and oxygen isotopic composition of stem cellulose of Pinus sylvestris, Picea abies, Fagus sylvatica and Fraxinus excelsior. Several sites along a transect of a small valley in Switzerland were selected which differ in soil moisture conditions. At every site, six trees per species were sampled, and a sample representing a mean value for the period from 1940 to 1990 was analysed. For all species, the mean site δ13C and δ18O of stem cellulose are related to the soil moisture availability, whereby higher isotope ratios are found at drier sites. This result is consistent with isotope fractionation models when assuming enhanced stomatal resistance (thus higher δ13C of incorporated carbon) and increased oxygen isotope enrichment in the leaf water (thus higher δ18O) at the dry sites. δ18 O-δ13C plots reveal a linear relationship between the carbon and oxygen isotopes in cellulose. To interpret this relationship we developed an equation which combines the above-mentioned fractionation models. An important new parameter is the degree to which the leaf water enrichment is reflected in the stem cellulose. In the combined model the slope of the δ18O-δ13C plot is related to the sensitivity of the pi/pa of a plant to changing relative humidity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-53.x
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  • 4
    Electronic Resource
    Electronic Resource
    Estimating the uptake of traffic-derived NO2 from 15N abundance in Norway spruce needles (1999)
    Springer
    Oecologia 118 (1999), S. 124-131 
    Details
    ISSN: 1432-1939
    Keywords: Key words15N ; Forests ; Spruce ; Picea abies ; NO2 deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 15N ratio of nitrogen oxides (NOx) emitted from vehicles, measured in the air adjacent to a highway in the Swiss Middle Land, was very high [δ15N(NO2) = +5.7‰]. This high 15N abundance was used to estimate long-term NO2 dry deposition into a forest ecosystem by measuring δ15N in the needles and the soil of potted and autochthonous spruce trees [Picea abies (L.) Karst] exposed to NO2 in a transect orthogonal to the highway. δ15N in the current-year needles of potted trees was 2.0‰ higher than that of the control after 4 months of exposure close to the highway, suggesting a 25% contribution to the N-nutrition of these needles. Needle fall into the pots was prevented by grids placed above the soil, while the continuous decomposition of needle litter below the autochthonous trees over previous years has increased δ15N values in the soil, resulting in parallel gradients of δ15N in soil and needles with distance from the highway. Estimates of NO2 uptake into needles obtained from the δ15N data were significantly correlated with the inputs calculated with a shoot gas exchange model based on a parameterisation widely used in deposition modelling. Therefore, we provide an indication of estimated N inputs to forest ecosystems via dry deposition of NO2 at the receptor level under field conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050710
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  • 5
    Electronic Resource
    Electronic Resource
    Linking stable oxygen and carbon isotopes with stomatal conductance and photosynthetic capacity: a conceptual model (2000)
    Springer
    Oecologia 125 (2000), S. 350-357 
    Details
    ISSN: 1432-1939
    Keywords: δ13C δ18O Grassland Isotope model Land-use change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Based on measurements of δ18O and δ13C in organic matter of C3-plants, we have developed a conceptual model that gives insight into the relationship between stomatal conductance (g l) and photosynthetic capacity (A max) resulting from differing environmental constraints and plant-internal factors. This is a semi-quantitative approach to describing the long-term effects of environmental factors on CO2 and H2O gas exchange, whereby we estimate the intercellular CO2 concentration (c i) from δ13C and the air humidity from δ18O. Assuming that air humidity is an important factor influencing g l, the model allows us to distinguish whether differences in c i are caused by a response of g l or of A max. As an application of the model we evaluated the isotope data from three species in plots differing in intensity of land use (hay meadows and abandoned areas) at three sites along a south north transect in the Eastern Alps. We found three different δ18O–δ13C response patterns in native and planted grassland species (cultivated in the greenhouse). After preliminary confirmation by gas-exchange measurements we conclude that the proposed model is a promising tool for deriving carbon water relations in different functional groups from δ18O and δ13C isotope data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420000466
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  • 6
    Electronic Resource
    Electronic Resource
    Simulation of Increased Nitrogen Deposition to a Montane Forest Ecosystem: Partitioning of the Added 15N (1999)
    Springer
    Water, air & soil pollution 116 (1999), S. 129-134 
    Details
    ISSN: 1573-2932
    Keywords: nitrogen deposition ; montane forest ; Picea abies ; N-15 isotope ; nitrate leaching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Nitrogen (N) was added over two years to a spruce-dominated (Picea abies) montane forest at Alptal, central Switzerland. A solution of ammonium nitrate (NH4NO2) was frequently sprinkled on the forest floor (1500 m2) to simulate an additional input of 30 kg N ha-1 yr-1 over the ambient 12 kg bulk inorganic N deposition. The added nitrogen was labelled with 15NH4 15NO3 during the first year. Results are compared to a control plot. Neither the trees nor the ground vegetation showed any increase in their N content. Only 4.1% of N in the ground vegetation came from the N addition. Current-year needles contained 11 mg N g-1 dry weight, of which only 2% was from labelled N; older needles had approximately half as much 15N. The uptake from the treatment was therefore very small. Redistribution of N also took place in the trunks: 1 to 2-year-old wood contained 0.7% labelled N, tree rings dating back 3 to 14 years contained 0.4%. Altogether, the above-ground vegetation took up 12% of the labelled N. Most 15N was recovered in the soil: 13% in litter and roots, 63% in the sieved soil. Nitrate leaching accounted for 10%. Factors thought to be influencing N uptake are discussed in relation to plant use of N and soil conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005206927764
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  • 7
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    Mitoribosomal small subunit biogenesis in trypanosomes involves an extensive assembly machinery (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2019
    Description: 〈p〉Mitochondrial ribosomes (mitoribosomes) are large ribonucleoprotein complexes that synthesize proteins encoded by the mitochondrial genome. An extensive cellular machinery responsible for ribosome assembly has been described only for eukaryotic cytosolic ribosomes. Here we report that the assembly of the small mitoribosomal subunit in 〈i〉Trypanosoma brucei〈/i〉 involves a large number of factors and proceeds through the formation of assembly intermediates, which we analyzed by using cryo–electron microscopy. One of them is a 4-megadalton complex, referred to as the small subunit assemblosome, in which we identified 34 factors that interact with immature ribosomal RNA (rRNA) and recognize its functionally important regions. The assembly proceeds through large-scale conformational changes in rRNA coupled with successive incorporation of mitoribosomal proteins, providing an example for the complexity of the ribosomal assembly process in mitochondria.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Site-specific water-use strategies of mountain pine and larch to cope with recent climate change (2016)
    Oxford University Press
    Details
    Publication Date: 2016-09-01
    Description: We aim to achieve a mechanistic understanding of the eco-physiological processes in Larix decidua and Pinus mugo var. uncinata growing on north- and south-facing aspects in the Swiss National Park in order to distinguish the short- and long-term effects of a changing climate. To strengthen the interpretation of the 18 O signal in tree rings and its coherence with the main factors and processes driving evaporative 18 O needle water enrichment, we analyzed the 18 O in needle, xylem and soil water over the growing season in 2013 and applied the mechanistic Craig–Gordon model (1965) for the short-term responses. We found that 18 O needle water strongly reflected the variability of relative humidity mainly for larch, while only 18 O in pine xylem water showed a strong link to 18 O in precipitation. Larger differences in offsets between modeled and measured 18 O needle water for both species from the south-facing aspects were detected, which could be explained by the high transpiration rates. Different soil water and needle water responses for the two species indicate different water-use strategies, further modulated by the site conditions. To reveal the long-term physiological response of the studied trees to recent and past climate changes, we analyzed 13 C and 18 O in wood chronologies from 1900 to 2013. Summer temperatures as well as summer and annual amount of precipitations are important factors for growth of both studied species from both aspects. However, mountain pine trees reduced sensitivity to temperature changes, while precipitation changes come to play an important role for the period from 1980 to 2013. Intrinsic water-use efficiency (WUEi) calculated for larch trees since the 1990s reached a saturation point at elevated CO 2 . Divergent trends between pine WUEi and 18 O are most likely indicative of a decline of mountain pine trees and are also reflected in decoupling mechanisms in the isotope signals between needles and tree-rings.
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 9
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    The relationship between needle sugar carbon isotope ratios and tree rings of larch in Siberia (2015)
    Oxford University Press
    Details
    Publication Date: 2015-11-21
    Description: Significant gaps still exist in our knowledge about post-photosynthetic leaf level and downstream metabolic processes and isotopic fractionations. This includes their impact on the isotopic climate signal stored in the carbon isotope composition ( 13 C) of leaf assimilates and tree rings. For the first time, we compared the seasonal 13 C variability of leaf sucrose with intra-annual, high-resolution 13 C signature of tree rings from larch ( Larix gmelinii Rupr.). The trees were growing at two sites in the continuous permafrost zone of Siberia with different growth conditions. Our results indicate very similar low-frequency intra-seasonal trends of the sucrose and tree ring 13 C records with little or no indication for the use of ‘old’ photosynthates formed during the previous year(s). The comparison of leaf sucrose 13 C values with that in other leaf sugars and in tree rings elucidates the cause for the reported 13 C-enrichment of sink organs compared with leaves. We observed that while the average 13 C of all needle sugars was 1.2 more negative than 13 C value of wood, the 13 C value of the transport sugar sucrose was on an average 1.0 more positive than that of wood. Our study shows a high potential of the combined use of compound-specific isotope analysis of sugars (leaf and phloem) with intra-annual tree ring 13 C measurements for deepening our understanding about the mechanisms controlling the isotope variability in tree rings under different environmental conditions.
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 10
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    THEODORE, a two-step heating system for the EC/OC determination of radiocarbon (14C) in the environment (2004)
    Elsevier
    Details
    Publication Date: 2004-08-01
    Print ISSN: 0168-583X
    Electronic ISSN: 1872-9584
    Topics: Physics
    Published by Elsevier
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