Neighbourhood species richness and drought-tolerance traits modulate tree growth and δ C responses to drought.

Mixed-species forests are promoted as a forest management strategy for climate change adaptation, but whether they are more resistant to drought than monospecific forests remains contested. In particular, the trait-based mechanisms driving the role of tree diversity under drought remain elusive. Using tree cores from a large-scale biodiversity experiment, we investigated tree growth and physiological stress responses (i.

Combined -omics framework reveals how ant symbionts benefit the Neotropical ant-plant at different levels.

Ant-plant defensive mutualism is a widely studied phenomenon, where ants protect their host plants (myrmecophytes) against herbivores in return for the provision of nesting sites and food. However, few studies addressed the influence of ant colonization and herbivory on the plant's metabolism. We chose the Amazonian plant , living in association with cf.

Isotopically characterised N O reference materials for use as community standards.

Rationale: Information on the isotopic composition of nitrous oxide (N O) at natural abundance supports the identification of its source and sink processes. In recent years, a number of mass spectrometric and laser spectroscopic techniques have been developed and are increasingly used by the research community. Advances in this active research area, however, critically depend on the availability of suitable N O isotope Reference Materials (RMs).

USGS44, a new high-purity calcium carbonate reference material for δ C measurements.

Rationale: The stable carbon isotopic (δ C) reference material (RM) LSVEC Li CO has been found to be unsuitable for δ C standardization work because its δ C value increases with exposure to atmospheric CO . A new CaCO RM, USGS44, has been prepared to alleviate this situation.

Methods: USGS44 was prepared from 8 kg of Merck high-purity CaCO .

Methyl sulfates as methoxy isotopic reference materials for δ C and δ H measurements.

Rationale: Stable hydrogen and carbon isotope ratios of methoxy groups (OCH ) of plant organic matter have many potential applications in biogeochemical, atmospheric and food research. So far, most of the analyses of plant methoxy groups by isotope ratio mass spectrometry have employed liquid iodomethane (CH I) as the reference material to normalise stable isotope measurements of these moieties to isotope-δ scales. However, comparisons of measurements of stable hydrogen and carbon isotopes of plant methoxy groups are still hindered by the lack of suitable reference materials.

Optimization of on-line hydrogen stable isotope ratio measurements of halogen- and sulfur-bearing organic compounds using elemental analyzer-chromium/high-temperature conversion isotope ratio mass spectrometry (EA-Cr/HTC-IRMS).

Rationale: Accurate hydrogen isotopic analysis of halogen- and sulfur-bearing organics has not been possible with traditional high-temperature conversion (HTC) because the formation of hydrogen-bearing reaction products other than molecular hydrogen (H ) is responsible for non-quantitative H yields and possible hydrogen isotopic fractionation. Our previously introduced, new chromium-based EA-Cr/HTC-IRMS (Elemental Analyzer-Chromium/High-Temperature Conversion Isotope Ratio Mass Spectrometry) technique focused primarily on nitrogen-bearing compounds. Several technical and analytical issues concerning halogen- and sulfur-bearing samples, however, remained unresolved and required further refinement of the reactor systems.

Reassessment of the NH NO thermal decomposition technique for calibration of the N O isotopic composition.

Rationale: In the last few years, the study of N O site-specific nitrogen isotope composition has been established as a powerful technique to disentangle N O emission pathways. This trend has been accelerated by significant analytical progress in the field of isotope ratio mass spectrometry (IRMS) and more recently quantum cascade laser absorption spectroscopy (QCLAS).

Methods: The ammonium nitrate (NH NO ) decomposition technique provides a strategy to scale the N site-specific (SP ≡ δ N - δ N ) and bulk (δ N  = (δ N  + δ N )/2) isotopic composition of N O against the international standard for the N/ N isotope ratio (AIR-N ).

Organic Reference Materials for Hydrogen, Carbon, and Nitrogen Stable Isotope-Ratio Measurements: Caffeines, n-Alkanes, Fatty Acid Methyl Esters, Glycines, L-Valines, Polyethylenes, and Oils.

An international project developed, quality-tested, and determined isotope-δ values of 19 new organic reference materials (RMs) for hydrogen, carbon, and nitrogen stable isotope-ratio measurements, in addition to analyzing pre-existing RMs NBS 22 (oil), IAEA-CH-7 (polyethylene foil), and IAEA-600 (caffeine). These new RMs enable users to normalize measurements of samples to isotope-δ scales. The RMs span a range of δ(2)H(VSMOW-SLAP) values from -210.

A new organic reference material, l-glutamic acid, USGS41a, for δ(13) C and δ(15) N measurements - a replacement for USGS41.

Rationale: The widely used l-glutamic acid isotopic reference material USGS41, enriched in both (13) C and (15) N, is nearly exhausted. A new material, USGS41a, has been prepared as a replacement for USGS41.

Methods: USGS41a was prepared by dissolving analytical grade l-glutamic acid enriched in (13) C and (15) N together with l-glutamic acid of normal isotopic composition.

Isotopic disproportionation during hydrogen isotopic analysis of nitrogen-bearing organic compounds.

Rationale: High-precision hydrogen isotope ratio analysis of nitrogen-bearing organic materials using high-temperature conversion (HTC) techniques has proven troublesome in the past. Formation of reaction products other than molecular hydrogen (H(2)) has been suspected as a possible cause of incomplete H(2) yield and hydrogen isotopic fractionation.

Methods: The classical HTC reactor setup and a modified version including elemental chromium, both operated at temperatures in excess of 1400 °C, have been compared using a selection of nitrogen-bearing organic compounds, including caffeine.

Novel silver-tubing method for quantitative introduction of water into high-temperature conversion systems for stable hydrogen and oxygen isotopic measurements.

A new method to seal water in silver tubes for use in a TC/EA (thermal conversion/elemental analyzer) reduction unit using a semi-automated sealing apparatus can yield reproducibilities (1 standard deviation) of delta(2)H and delta(18)O measurements of 1.0 per thousand and 0.06 per thousand, respectively.

Comprehensive inter-laboratory calibration of reference materials for delta18O versus VSMOW using various on-line high-temperature conversion techniques.

Internationally distributed organic and inorganic oxygen isotopic reference materials have been calibrated by six laboratories carrying out more than 5300 measurements using a variety of high-temperature conversion techniques (HTC)a in an evaluation sponsored by the International Union of Pure and Applied Chemistry (IUPAC). To aid in the calibration of these reference materials, which span more than 125 per thousand, an artificially enriched reference water (delta(18)O of +78.91 per thousand) and two barium sulfates (one depleted and one enriched in (18)O) were prepared and calibrated relative to VSMOW2b and SLAP reference waters.

Continuous flow 2H/1H and 18O/16O analysis of water samples with dual inlet precision.

A method for isotope ratio analysis of water samples is described comprising an on-line high-temperature reduction technique in a helium carrier gas. Using a gas-tight syringe, injection of 0.5 to 1 microL sample is made through a heated septum into a glassy carbon reactor at temperatures in excess of 1300 degrees C.

Two new organic reference materials for delta13C and delta15N measurements and a new value for the delta13C of NBS 22 oil.

Analytical grade L-glutamic acid is chemically stable and has a C/N mole ratio of 5, which is close to that of many of natural biological materials, such as blood and animal tissue. Two L-glutamic acid reference materials with substantially different 13C and 15N abundances have been prepared for use as organic reference materials for C and N isotopic measurements. USGS40 is analytical grade L-glutamic acid and has a delta13C value of -26.