|
| ||
|
|
||
Carbon Isotope Composition (carbon + isotope_composition)
Selected AbstractsCarbon isotope composition of fossil leaves , revealing ecophysiological responses to past environmental changeNEW PHYTOLOGIST, Issue 2 2002Wolfram M. Kürschner No abstract is available for this article. [source] Use of decreasing foliar carbon isotope discrimination during water limitation as a carbon tracer to study whole plant carbon allocationPLANT CELL & ENVIRONMENT, Issue 5 2002S. K. Arndt Abstract Foliar carbon isotope discrimination (,) of C3 plants decreases in water-deficit situations as discrimination by the photosynthetic primary carboxylation reaction decreases. This diminished , in leaves under water deficit can be used as a tracer to study whole plant carbon allocation patterns. Carbon isotope composition (,13C value) of leaf hot water extracts or leaf tissue sap represents a short-term integral of leaf carbon isotope discrimination and thus represents the ,13C value of source carbon that may be distributed within a plant in water-deficit situations. By plotting the ,13C values of source carbon against the ,13C values of sink tissues, such as roots or stems, it is possible to assess carbon allocation to and incorporation into sink organs in relation to already present biomass. This natural abundance labelling method has been tested in three independent experiments, a one-year field study with the fruit tree species Ziziphus mauritiana and peach (Prunus persica), a medium-term drought stress experiment with Ziziphus rotundifolia trees in the glasshouse, and a short-term drought stress experiment with soybean (Glycine max). The data show that the natural abundance labelling method can be applied to qualitatively assess carbon allocation in drought-stressed plants. Although it is not possible to estimate exact fluxes of assimilated carbon during water deficit the method represents an easy to use tool to study integrated plant adaptations to drought stress. In addition, it is a less laborious method that can be applied in field studies as well as in controlled experiments, with plants from any developmental stage. [source] Carbon isotope discrimination and wood anatomy variations in mixed stands of Quercus robur and Quercus petraeaPLANT CELL & ENVIRONMENT, Issue 8 2001S. Ponton Abstract The two most common oak species in western Europe, Quercus robur and Quercus petraea, display different ecological behaviours, particularly with respect to their responses to drought. The ecophysiological basis of this niche difference is not understood well. Here we test the hypothesis that these two species present distinct water use efficiencies (WUEs), using the carbon isotope discrimination approach. Leaves and 13 dated ring sequences were sampled in 10 pairs of adult trees growing side by side. Carbon isotope composition was measured on cellulose extracts. In addition, relationships between carbon isotope discrimination and wood anatomy were assessed at the tree level. Quercus robur displayed a 1·0, larger isotopic discrimination than Q. petraea, and therefore a lower intrinsic WUE (,13%). This interspecific difference of isotopic discrimination was quite stable with time and independent of tree radial growth and climate fluctuations. A strong positive correlation was observed between average tree values of earlywood vessel surface area and 13C isotopic discrimination. This correlation was even higher with 13C of the 1976 dry year (r = 0·86). These observations led to the hypothesis that hydraulic properties of xylem could exert a constraint on leaf gas exchange, resulting in a larger WUE for individuals with smaller vessel cross-section area. [source] Winners and losers in herbaceous plant communities: insights from foliar carbon isotope composition in monocultures and mixturesJOURNAL OF ECOLOGY, Issue 6 2005A. JUMPPONEN Summary 1We established monocultures and 16 unique mixed communities of 12 native grasses, legumes and non-N2 -fixing forbs. We identified species having a greater or lesser yield in the mixed communities than expected from monoculture data as winners and losers, respectively. To test our hypothesis that performance of the subordinate species (losers) is mainly controlled by light availability, whereas the dominant species (winners) are sensitive to the availability of below-ground resources, we traced the effects of number of species, light transmission in the community and foliar N concentration on plant photosynthesis through leaf C isotope composition (,13C). 2Phalaris arundinacea and Phleum pratense, the two tallest grass species, yielded more in mixtures than expected, as, initially, did Dactylis glomerata. Festuca ovina, the smallest grass, and Ranunculus acris, a forb, had smaller yield in mixtures than expected. For most species, observed mixture yields did not deviate significantly from those expected. 3Decreases in transmitted light decreased ,13C in D. glomerata, Lotus corniculatus and Rumex acetosa. The ,13C of Trifolium pratense and L. corniculatus was affected by increasing number of species in the plant community even after accounting for the transmitted light. In P. arundinacea, ,13C increased with increasing foliar %N, as expected for the tallest, dominant species. 4Species showing a positive, significant relationship between ,13C and transmitted light were relatively low growing and unable to establish dominance in multispecies communities due to shading by larger dominants. 5We conclude that above-ground competition is crucial in determining C isotope composition among the subordinate species, whereas the dominant species are more strongly affected by below-ground resources. Different factors thus dictate the physiological performance of species according to the size-distribution hierarchy in the community. [source] Variability in the carbon isotope signature of Prochilodus lineatus (Prochilodontidae, Characiformes) a bottom-feeding fish of the Neotropical regionJOURNAL OF FISH BIOLOGY, Issue 6 2007C. A. Lopes The spatial and seasonal variability of stable carbon isotopes in detritivorous Prochilodus lineatus, primary producers and particulate organic carbon (POC) were examined to promote a better understanding of the trophic dynamics of food webs in Neotropical ecosystems. Spatial variability in carbon isotope composition in the species showed a decreasing gradient in the Upper Paraná River system, from the Paraná River and Itaipu Reservoir subsystems to the Baía and Ivinheima subsystems. Fish ,13C followed the isotopic trend of POC along the Paraná River and Baía subsystem. Seasonal differences were not observed in fish. The analysis of percentile contribution of C3 and C4 sources in the species diet revealed the predominance of C3 plants (phytoplanktonic and periphytic algae and riparian vegetation) in most of the analysed subsystems and seasons. Nevertheless, the considerable participation of riparian vegetation was verified, especially in the Ivinheima subsystem in the dry season. C4 macrophytes presented a maximum contribution along the Upper Paraná River. These results demonstrate the existence of specific variability for the consumer and their food sources in different environments of the same ecosystem. [source] Sex-specific responses of Populus cathayana to drought and elevated temperaturesPLANT CELL & ENVIRONMENT, Issue 6 2008XIAO XU ABSTRACT Dioecious plant species represent an important component of terrestrial ecosystems. Yet, little is known about sex-specific responses to drought and elevated temperatures. Populus cathayana Rehd, which is a dioecious, deciduous tree species, widely distributed in the northern, central and southwestern regions of China, was employed as a model species in our study. In closed-top chamber experiments, sex-specific morphological, physiological and biochemical responses of P. cathayana to drought and different elevated temperatures were investigated. Compared with the controls, drought significantly decreased the growth and the net photosynthesis rate (A), and increased the intrinsic water use efficiency (WUEi), carbon isotope composition (,13C), and the malondialdehyde (MDA) and abscisic acid (ABA) contents in droughted plants. In contrast, elevated temperatures significantly promoted the growth and the A, but decreased the WUEi, ,13C, MDA and ABA contents in well-watered individuals. When compared with males, elevated temperatures induced well-watered females to express a greater increase in the height growth (HG), basal diameter (BD), leaf area (LA), total number of leaves (TNL), dry matter accumulation (DMA) and specific leaf area (SLA), and a lower decrease in the A value, transpiration (E), stomatal conductance (gs), MDA and ABA contents, while elevated temperatures induced drought-stressed females to exhibit lower values of HG, BD, LA, TNL, DMA, A, E, gs and the intercellular CO2 concentration (Ci), and higher levels of SLA, WUEi, ,13C, MDA and ABA contents. Our results indicated that the female individuals of P. cathayana are more responsive and suffer from greater negative effects than do males when grown under environments with increased drought stress and elevated temperature. [source] Genetic parameters and QTL analysis of ,13C and ring width in maritime pinePLANT CELL & ENVIRONMENT, Issue 8 2002O. Brendel Abstract Classical quantitative genetics and quantitative trait dissection analysis (QTL) approaches were used in order to investigate the genetic determinism of wood cellulose carbon isotope composition (,13C, a time integrated estimate of water use efficiency) and of diameter growth and their relationship on adult trees (15 years) of a forest tree species (maritime pine). A half diallel experimental set-up was used to (1) estimate heritabilities for ,13C and ring width and (2) to decompose the phenotypic ,13C/growth correlation into its genetic and environmental components. Considerable variation was found for ,13C (range of over 3,) and for ring width (range of over 5 mm) and significant heritabilities (narrow sense 0·17/0·19 for ,13C and ring width, respectively, 100% additivity). The significant phenotypic correlation between ,13C and ring width was not determined by the genetic component, but was attributable to environmental components. Using a genetic linkage map of a full-sib family, four significant and four suggestive QTLs were detected for ,13C, the first for ,13C in a forest tree species, as far as known to the authors. Two significant and four suggestive QTLs were found for ring width. No co-location of QTLs was found between ,13C and growth. [source] Spatial distribution of leaf water-use efficiency and carbon isotope discrimination within an isolated tree crownPLANT CELL & ENVIRONMENT, Issue 10 2001X. Le Roux Abstract The spatial variations in the stable carbon isotope composition (,13C) of air and leaves (total matter and soluble sugars) were quantified within the crown of a well-watered, 20-year-old walnut tree growing in a low-density orchard. The observed leaf carbon isotope discrimination (,) was compared with that computed by a three-dimensional model simulating the intracanopy distribution of irradiance, transpiration and photosynthesis (previously parameterized and tested for the same tree canopy) coupled to a biophysically based model of carbon isotope discrimination. The importance of discrimination associated with CO2 gradients encountered from the substomatal sites to the carboxylation sites was evaluated. We also assessed by simulation the effect of current irradiance on leaf gas exchange and the effect of long-term acclimation of photosynthetic capacity and stomatal and internal conductances to light regime on intracanopy gradients in ,. The main conclusions of this study are: (i) leaf , can exhibit important variations (5 and 8, in total leaf material and soluble sugars, respectively) along light gradients within the foliage of an isolated tree; (ii) internal conductance must be taken into account to adequately predict leaf ,, and (iii) the spatial variations in , and water-use efficiency resulted from the short-term response of leaf gas exchange to variations in local irradiance and, to a much lesser extent, from the long-term acclimation of leaf characteristics to the local light regime. [source] Preparation of starch and soluble sugars of plant material for the analysis of carbon isotope composition: a comparison of methods,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2009Andreas Richter Starch and soluble sugars are the major photosynthetic products, and their carbon isotope signatures reflect external versus internal limitations of CO2 fixation. There has been recent renewed interest in the isotope composition of carbohydrates, mainly for use in CO2 flux partitioning studies at the ecosystem level. The major obstacle to the use of carbohydrates in such studies has been the lack of an acknowledged method to isolate starch and soluble sugars for isotopic measurements. We here report on the comparison and evaluation of existing methods (acid and enzymatic hydrolysis for starch; ion-exchange purification and compound-specific analysis for sugars). The selectivity and reproducibility of the methods were tested using three approaches: (i) an artificial leaf composed of a mixture of isotopically defined compounds, (ii) a C4 leaf spiked with C3 starch, and (iii) two natural plant samples (root, leaf). Starch preparation methods based on enzymatic or acid hydrolysis did not yield similar results and exhibited contaminations by non-starch compounds. The specificity of the acidic hydrolysis method was especially low, and we therefore suggest terming these preparations as HCl-hydrolysable carbon, rather than starch. Despite being more specific, enzyme-based methods to isolate starch also need to be further optimized to increase specificity. The analysis of sugars by ion-exchange methods (bulk preparations) was fast but produced more variable isotope compositions than compound-specific methods. Compound-specific approaches did not in all cases correctly reproduce the target values, mainly due to unsatisfactory separation of sugars and background contamination. Our study demonstrates that, despite their wide application, methods for the preparation of starch and soluble sugars for the analysis of carbon isotope composition are not (yet) reliable enough to be routinely applied and further research is urgently needed to resolve the identified problems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Sulfur Isotope Geochemistry of the Supergiant Xikuangshan Sb Deposit, Central Hunan, China: Constraints on Sources of Ore ConstituentsRESOURCE GEOLOGY, Issue 4 2006Dong-sheng Yang Abstract. The supergiant Xikuangshan Sb deposit is located in the Middle to Upper Devonian limestone of central Hunan, China. Primary ores are composed of early-stage stibnite and calcite with rare pyrite, early main-stage stibnite and quartz, and late main-stage stibnite and calcite. New sulfur isotope data reveal the clustering of ,34S values (+5 , +8 %) for both early and late main-stage stibnite; a single early-stage stibnite exhibits ,34S value (+7.5 %) identical to its main ore-stage counterparts and the coexisting calcite has almost unmodified carbon isotope composition (-4.4 %). The data suggest a probable common source of sulfur for stibnite that was deposited at different paragenetic stages. A much wider variation in ,34S values for early main-stage stibnite (+3.5 to +16.3 %, av. +7.5 %) compared to that for late main-stage stibnite (+5.3 to +8.1 %, av. +6.2 %) can be interpreted to be due to local interaction of earlier ore fluid with Devonian host rocks. The previous studies show that the Precambrian basement contains elevated Sb concentrations, and two distinctive sulfur reservoirs with ,34Spyrite values at ca. +11 , +24 % and -7.0 ,-11 %. The homogenizing effect for sulfur hydrothermally leached from the two reservoirs might have provided ore constituents for the Xikuangshan fluids. [source] Relationships of grain ,13C and ,18O with wheat phenology and yield under water-limited conditionsANNALS OF APPLIED BIOLOGY, Issue 2 2007J.P. Ferrio Abstract Stable carbon isotope composition (,13C) of dry matter has been widely investigated as a selection tool in cereal breeding programmes. However, reports on the possibilities of using stable oxygen isotope composition (,18O) as a yield predictor are very scarce and only in the absence of water stress. Indeed, it remains to be tested whether changes in phenology and stomatal conductance in response to water stress overrule the use of either ,13C or ,18O when water is limited. To answer this question, a set of 24 genotypes of bread wheat (Triticum aestivum) were assayed in two trials with different levels of deficit irrigation and a third trial under rainfed conditions in a Mediterranean climate (northwest Syria). Grain yield (GY) and phenology (duration from planting to anthesis and from anthesis to maturity) were recorded, and the ,13C and ,18O of grains were analysed to assess their suitability as GY predictors. Both ,13C and ,18O showed higher broad-sense heritabilities (H2) than GY. Genotype means of GY across trials were negatively correlated with ,13C, as previously reported, but not with ,18O. Both isotopes were correlated with grain filling duration, whereas ,18O was also strongly affected by crop duration from planting to anthesis. We concluded that ,18O of grains is not a proper physiological trait to breed for suboptimal water conditions, as its variability is almost entirely determined by crop phenology. In contrast, ,13C of grains, despite being also affected by phenology, still provides complementary information associated with GY. [source] The role of inter-specific, micro-habitat and climatic factors on the carbon isotope (,13C) variability of a modern leaf assemblage from northern Scandinavia: implications for climate reconstructionBOREAS, Issue 2 2006NEIL J. LOADER To provide a basis for the interpretation of past climatic conditions from Quaternary leaf records, leaf carbon isotope (,13C) results are presented for 12 northern European dwarf-shrub, shrub and tree species growing across a network of 18 sites in northern Scandinavia. The role of micro-habitat (hummock/hollow) on carbon isotope trends is explored in addition to a comparison of the carbon isotope composition of both cellulose and wholeleaf material. The data are also examined against local meteorological variables (temperature, precipitation and vapour pressure deficit) at both species and genus levels. Results exhibit only modest coherence between selected plant species and low-order correlations with external climate forcings consistent with accepted models for carbon isotope fractionation. Potential for the analysis and interpretation of stable isotopic time series may still be identified; however, factors such as inter-plant variability, senescence, diagenesis and homogeneity need to be thoroughly addressed before such an approach may be used for palaeoenvironmental reconstructions. These findings highlight the complexities and limitations of spatial calibration methods. [source] Carbon and Oxygen Isotopic Composition of Surface-Sediment Carbonate in Bosten Lake (Xinjiang, China) and its Controlling FactorsACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2009Chengjun ZHANG Abstract: Bosten Lake is a mid-latitude lake with water mainly supplied by melting ice and snow in the Tianshan Mountains. The depositional environment of the lake is spatially not uniform due to the proximity of the major inlet and the single outlet in the western part of the lake. The analytical results show that the carbon and oxygen isotopic composition of recent lake sediments is related to this specific lacustrine depositional environment and to the resulting carbonate mineralogy. In the southwestern lake region between the Kaidu River inlet and the Kongqi River outlet, carbon isotope composition (,13C) values of the carbonate sediment (,1, to ,2,) have no relation to the oxygen isotope composition of the carbonate (,18O) values (,7, to ,8,), with both isotopes showing a low variability. The carbonate content is low (<20%). Carbonate minerals analyzed by X-ray diffraction are mainly composed of calcite, while aragonite was not recorded. The salinity of the lake water is low in the estuary region as a result of the Kaidu River inflow. In comparison, the carbon and oxygen isotope values are higher in the middle and eastern parts of the lake, with ,13C values between approximately +0.5, and +3,, and ,18O values between ,1, and ,5,. There is a moderate correlation between the stable oxygen and carbon isotopes, with a coefficient of correlation r of approximately 0.63. This implies that the lake water has a relatively short residence time. Carbonate minerals constitute calcite and aragonite in the middle and eastern region of the lake. Aragonite and Mg,calcite are formed at higher lake water salinity and temperatures, and larger evaporation effects. More saline lake water in the middle and eastern region of the lake and the enhanced isotopic equilibrium between water and atmospheric CO2 cause the correlating carbon and oxygen isotope values determined for aragonite and Mg,calcite. Evaporation and biological processes are the main reasons for the salinity and carbonate mineralogy influence of the surface-sediment carbonate in Bosten Lake. The lake water residence time and the CO2 exchange between the atmosphere and the water body control the carbon and oxygen isotope composition of the carbonate sediment. In addition, organic matter pollution and decomposition result in the abnormally low carbon isotope values of the lake surface-sediment carbonate. [source] Pretreatment technique for siderite removal for organic carbon isotope and C:N ratio analysis in geological samplesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2008Toti E. Larson A method for the removal of siderite from geological samples to determine organic carbon isotope compositions using elemental analysis isotope ratio mass spectrometry is presented which includes calculations for % organic carbon in samples that contain diagenetic carbonate. The proposed method employs in situ acidification of geological samples with 6,N HCl and silver capsule sample holders and was tested on modern peach leaf samples (NIST 1547) and ancient lacustrine samples from Valles Caldera, New Mexico. The in situ acidification technique eliminates potential errors associated with the removal of soluble organic material using standard acid decanting techniques and allows for removal of the less soluble siderite, which is not efficiently removed using vapor acidification techniques. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||