Yield and nitrogen accumulation and partitioning in winter wheat under elevated CO2: A 3-year free-air CO2 enrichment experiment

Fossil fuel combustion and deforestation have resulted in a rapid increase in atmospheric [CO2] since the 1950’s, and it will reach about 550 μmol mol−1 in 2050. Field experiments were conducted at the Free-air CO2 Enrichment facility in Beijing, China. Winter wheat was grown to maturity under elevated [CO2] (550 ± 17 μmol mol−1) and ambient [CO2] (415 ± 16 μmol mol−1), with high nitrogen (N) supply (HN, 170 kg N ha−1) and low nitrogen supply (LN, 100 kg N ha−1) for three growing seasons from 2007 to 2010. Elevated [CO2] increased wheat grain yield by 11.4% across the three years. [CO2]-induced yield enhancements were 10.8% and 11.9% under low N and high N supply, respectively. Nitrogen accumulation under elevated [CO2] was increased by 12.9% and 9.2% at the half-way anthesis and ripening stage across three years, respectively. Winter wheat had higher nitrogen demand under elevated [CO2] than ambient [CO2], and grain yield had a stronger correlation with plant N uptake after anthesis than before anthesis at high [CO2]. Our results suggest that regulating on the N application rate and time, is likely important for sustainable grain production under future CO2 climate.

Interacting controls on innate sources of CO2 efflux from a calcareous arid zone soil under experimental acidification and wetting

More than half of global soil carbon is stored as carbonates, primarily in arid and semi-arid zones. Climate change models predict more frequent and severe rainfall events in some parts of the globe, many of which are dominated by calcareous soils. Such events trigger substantial increases in soil CO2 efflux. We hypothesised that the primary source of CO2 emissions from calcareous, arid zone soil during a single wetting event is abiotic and that soil acidification and wetting have a positive, potentially interacting, effect. We manipulated soil pH, soil moisture, and controlled soil respiration by gamma irradiating half of an 11 day incubation experiment. All manipulated experimental treatments had a rapid and enormous effect on CO2 emission. Respiration contributed ca. 5% of total CO2 efflux; the major source (carbonate buffering) varied depending on the extent of acidification and wetting. Maximum CO2 efflux occurred when pH was lowest and at intermediate matric potential. CO2 efflux was lowest at native pH when soil was air dry. Our data suggest that there may be an underestimate of soil-atmosphere carbon fluxes in arid ecosystems with calcareous soils. There is also a clear potential that these soils may become net carbon sources depending on changes in rainfall patterns, rainfall acidity, and future land management. Our findings have major implications for carbon cycling in arid zone soil and further study of carbon dynamics in these terrestrial systems at a landscape level will be required if we are to improve global climate and carbon cycling models.

OzFACE: the Australian savanna free air CO2 enrichment facility and its relevance to carbon-cycling issues in a tropical savanna

A free air CO2 enrichment (FACE) facility has recently been constructed in a tropical savanna in north-eastern Queensland, Australia. The system has a novel and cost-effective design and uses an industrial source of pure CO2 piped directly to the site. We describe the design details of this facility and assess the likely contribution it will make towards advancing our understanding of the direct impacts of rising atmospheric CO2 on savannas. These include addressing uncertainties about future shifts in the tree–grass balance and associated changes in carbon stocks, responses of C4 grasses in dry tropical environments, potential sequestration of soil carbon, and the modifications of CO2 responses by moisture and nutrient interactions. Tropical regions have been poorly represented in climate change research, and the work at the OzFACE facility will complement existing and ongoing FACE studies at temperate latitudes.

CO2 emission estimation in the urban environment: measurement of the CO2 storage term

Eddy covariance has been used in urban areas to evaluate the net exchange of CO2 between the surface and the atmosphere. Typically, only the vertical flux is measured at a height 2–3 times that of the local roughness elements; however, under conditions of relatively low instability, CO2 may accumulate in the airspace below the measurement height. This can result in inaccurate emissions estimates if the accumulated CO2 drains away or is flushed upwards during thermal expansion of the boundary layer. Some studies apply a single height storage correction; however, this requires the assumption that the response of the CO2 concentration profile to forcing is constant with height. Here a full seasonal cycle (7th June 2012 to 3rd June 2013) of single height CO2 storage data calculated from concentrations measured at 10 Hz by open path gas analyser are compared to a data set calculated from a concurrent switched vertical profile measured (2 Hz, closed path gas analyser) at 10 heights within and above a street canyon in central London. The assumption required for the former storage determination is shown to be invalid. For approximately regular street canyons at least one other measurement is required. Continuous measurements at fewer locations are shown to be preferable to a spatially dense, switched profile, as temporal interpolation is ineffective. The majority of the spectral energy of the CO2 storage time series was found to be between 0.001 and 0.2 Hz (500 and 5 s respectively); however, sampling frequencies of 2 Hz and below still result in significantly lower CO2 storage values. An empirical method of correcting CO2 storage values from under-sampled time series is proposed.

Intensities and self-broadening coefficients of the strongest water vapour lines in the 2.7 and 6.25μm absorption bands

Intensities and self-broadening coefficients are presented for about 460 of the strongest water vapour lines in the spectral regions 1400–1840 cm−1 and 3440–3970 cm−1 at room temperature, obtained from rather unique measurements using a 5-mm-path-length cell. The retrieved spectral line parameters are compared with those in the HITRAN database ver. 2008 and 2012 and with recent ab-initio calculations. Both the retrieved intensities and half-widths are on average in reasonable agreement with those in HITRAN-2012. Maximum systematic differences do not exceed 4% for intensities (1600 cm−1 band) and 7% for self-broadening coefficients (3600 cm−1 band). For many lines however significant disagreements were detected with the HITRAN-2012 data, exceeding the average uncertainty of the retrieval. In addition, water vapour line parameters for 5300 cm−1 (1.9 μm) band reported by us in 2005 were also compared with HITRAN-2012, and show average differences of 4–5% for both intensities and half-widths.

The role of CO2 and dynamic vegetation on the impact of temperate land use change in the HadCM3 coupled climate model

Human induced land-use change (LUC) alters the biogeophysical characteristics of the land surface influencing the surface energy balance. The level of atmospheric CO2 is expected to increase in the coming century and beyond, modifying temperature and precipitation patterns and altering the distribution and physiology of natural vegetation. It is important to constrain how CO2-induced climate and vegetation change may influence the regional extent to which LUC alters climate. This sensitivity study uses the HadCM3 coupled climate model under a range of equilibrium forcings to show that the impact of LUC declines under increasing atmospheric CO2, specifically in temperate and boreal regions. A surface energy balance analysis is used to diagnose how these changes occur. In Northern Hemisphere winter this pattern is attributed in part to the decline in winter snow cover and in the summer due to a reduction in latent cooling with higher levels of CO2. The CO2-induced change in natural vegetation distribution is also shown to play a significant role. Simulations run at elevated CO2 yet present day vegetation show a significantly increased sensitivity to LUC, driven in part by an increase in latent cooling. This study shows that modelling the impact of LUC needs to accurately simulate CO2 driven changes in precipitation and snowfall, and incorporate accurate, dynamic vegetation distribution.

Fast and slow precipitation responses to individual climate forcers: a PDRMIP multi-model study

Precipitation is expected to respond differently to various drivers of anthropogenic climate change. We present the first results from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), where nine global climate models have perturbed CO2, CH4, black carbon, sulfate, and solar insolation. We divide the resulting changes to global mean and regional precipitation into fast responses that scale with changes in atmospheric absorption and slow responses scaling with surface temperature change. While the overall features are broadly similar between models, we find significant regional intermodel variability, especially over land. Black carbon stands out as a component that may cause significant model diversity in predicted precipitation change. Processes linked to atmospheric absorption are less consistently modeled than those linked to top-of-atmosphere radiative forcing. We identify a number of land regions where the model ensemble consistently predicts that fast precipitation responses to climate perturbations dominate over the slow, temperature-driven responses.

THE COMPTON-THICK SEYFERT 2 NUCLEUS OF NGC 3281: TORUS CONSTRAINTS FROM THE 9.7 mu m SILICATE ABSORPTION

We present mid-infrared (mid-IR) spectra of the Compton-thick Seyfert 2 galaxy NGC 3281, obtained with the Thermal-Region Camera Spectrograph at the Gemini-South telescope. The spectra present a very deep silicate absorption at 9.7 mu m, and [S IV] 10.5 mu m and [Ne II] 12.7 mu m ionic lines, but no evidence of polycyclic aromatic hydrocarbon emission. We find that the nuclear optical extinction is in the range 24 mag <= A(V) <= 83 mag. A temperature T = 300 K was found for the blackbody dust continuum component of the unresolved 65 pc nucleus and the region at 130 pc SE, while the region at 130 pc NW reveals a colder temperature (200 K). We describe the nuclear spectrum of NGC 3281 using a clumpy torus model that suggests that the nucleus of this galaxy hosts a dusty toroidal structure. According to this model, the ratio between the inner and outer radius of the torus in NGC 3281 is R(0)/R(d) = 20, with 14 clouds in the equatorial radius with optical depth of tau(V) = 40 mag. We would be looking in the direction of the torus equatorial radius (i = 60 degrees), which has outer radius of R(0) similar to 11 pc. The column density is N(H) approximate to 1.2 x 10(24) cm(-2) and the iron K alpha equivalent width (approximate to 0.5-1.2 keV) is used to check the torus geometry. Our findings indicate that the X-ray absorbing column density, which classifies NGC 3281 as a Compton-thick source, may also be responsible for the absorption at 9.7 mu m providing strong evidence that the silicate dust responsible for this absorption can be located in the active galactic nucleus torus.

Dietary copper absorption and excretion in three semi-terrestrial grapsoid crabs with different levels of terrestrial adaptation

Three species of phylogenetically related semi-terrestrial crabs (Superfamily Grapsoidea - Sesarma rectum, Goniopsis cruentata and Neohelice granulata (formerly: Chasmagnathus granulatus) with different degrees of terrestriality were studied to quantify the accumulation of copper (Cu) in hemolymph, gills, hepatopancreas and antennal gland, and its excretion through the faeces. These crabs were fed for 15 days practical diets containing 0 (A), 0.5 (B), 1.0 (C), and 1.5% (D) of added CuCl2 (corresponding to 0, 0.2, 0.5 and 0.7% of Cu2+, respectively). The amount of food ingested was directly proportional to the degree of terrestriality: S. rectum, the most terrestrial species, ate around 2-3 times more than the other crabs, whereas G. cruentata ate 1.5-2 times more than N. granulata, the least terrestrial. The amount of Cu excreted in the feces was proportional to Cu ingestion, and was 76.8% and 64.2% higher for Sesarma fed diet D compared to G. cruentata and N. granulata, respectively. Sesarma also displayed higher Cu concentration in the haemolymph, gills and antennal glands, but not in the hepatopancreas. A detoxifying mechanism followed by elimination was probably present at this last organ, preventing Cu accumulation. More terrestrial crabs, such as Sesarma, may accumulate more Cu in hemolymph and tissues, showing a correlation between metal accumulation and increased terrestriality. In this aspect, contaminated feed sources with Cu may have more impact in conservation of terrestrial crabs. (C) 2008 Elsevier Inc. All rights reserved.

Transporters involved in glucose and water absorption in the Dysdercus peruvianus (Hemiptera: Pyrrhocoridae) anterior midgut

Little is known about insect intestinal sugar absorption, in spite of the recent findings, and even less has been published regarding water absorption. The aim of this study was to shed light on putative transporters of water and glucose in the insect midgut Glucose and water absorptions by the anterior ventriculus of Dysdercus peruvianus midgut were determined by feeding the insects with a glucose and a non-absorbable dye solution, followed by periodical dissection of insects and analysis of ventricular contents. Glucose absorption decreases glucose/dye ratios and water absorption increases dye concentrations. Water and glucose transports are activated (water 50%, glucose 33%) by 50 mM K(2)SO(4) and are inhibited (water 46%, glucose 82%) by 0.2 mM phloretin, the inhibitor of the facilitative hexose transporter (GLUT) or are inhibited (water 45%, glucose 35%) by 0.1 mM phlorizin, the inhibitor of the Na(+)-glucose cotransporter (SGLT). The results also showed that the putative SGLT transports about two times more water relative to glucose than the putative GLUT. These results mean that D. peruvianus uses a GLUT-like transporter and an SGLT-like transporter (with K(+) instead of Na(+)) to absorb dietary glucose and water. A cDNA library from D. peruvianus midgut was screened and we found one sequence homologous to GLUT1, named DpGLUT, and another to a sodium/solute symporter, named DpSGLT. Semi-quantitative RT-PCR studies revealed that DpGLUT and DpSGLTs mRNA were expressed in the anterior midgut, where glucose and water are absorbed, but not in fat body, salivary gland and Malpighian tubules. This is the first report showing the involvement of putative GLUT and SGLT in both water and glucose midgut absorption in insects. (C) 2010 Elsevier Inc. All rights reserved.

Spectral absorption properties of aerosol particles from 350-2500nm

The aerosol spectral absorption efficiency (alpha(a) in m(2)/g) is measured over an extended wavelength range (350-2500 nm) using an improved calibrated and validated reflectance technique and applied to urban aerosol samples from Sao Paulo, Brazil and from a site in Virginia, Eastern US, that experiences transported urban/industrial aerosol. The average alpha(a) values (similar to 3m(2)/g at 550 nm) for Sao Paulo samples are 10 times larger than a a values obtained for aerosols in Virginia. Sao Paulo aerosols also show evidence of enhanced UV absorption in selected samples, probably associated with organic aerosol components. This extra UV absorption can double the absorption efficiency observed from black carbon alone, therefore reducing by up to 50% the surface UV fluxes, with important implications for climate, UV photolysis rates, and remote sensing from space. Citation: Martins, J.V., P. Artaxo, Y.J. Kaufman, A.D. Castanho, and L.A. Remer (2009), Spectral absorption properties of aerosol particles from 350-2500nm, Geophys. Res. Lett., 36, L13810, doi: 10.1029/2009GL037435.

Continuum, Discrete, and Explicit Solvation Models for Describing the Low-Lying Absorption Spectrum of the Pterin Acid in Aqueous Environment

The absorption spectrum of the acid form of pterin in water was investigated theoretically. Different procedures using continuum, discrete, and explicit models were used to include the solvation effect on the absorption spectrum, characterized by two bands. The discrete and explicit models used Monte Carlo simulation to generate the liquid structure and time-dependent density functional theory (B3LYP/6-31G+(d)) to obtain the excitation energies. The discrete model failed to give the correct qualitative effect on the second absorption band. The continuum model, in turn, has given a correct qualitative picture and a semiquantitative description. The explicit use of 29 solvent molecules, forming a hydration shell of 6 angstrom, embedded in the electrostatic field of the remaining solvent molecules, gives absorption transitions at 3.67 and 4.59 eV in excellent agreement with the S(0)-S(1) and S(0)-S(2) absorption bands at of 3.66 and 4.59 eV, respectively, that characterize the experimental spectrum of pterin in water environment. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110: 2371-2377, 2010

Solvent effects on the electronic absorption spectrum of camphor using continuum, discrete or explicit approaches

We address the effect of solvation on the lowest electronic excitation energy of camphor. The solvents considered represent a large variation in-solvent polarity. We consider three conceptually different ways of accounting for the solvent using either an implicit, a discrete or an explicit solvation model. The solvatochromic shifts in polar solvents are found to be in good agreement with the experimental data for all three solvent models. However, both the implicit and discrete solvation models are less successful in predicting solvatochromic shifts for solvents of low polarity. The results presented suggest the importance of using explicit solvent molecules in the case of nonpolar solvents. (C) 2009 Elsevier B.V. All rights reserved.

MAGNETO-OPTICAL ABSORPTION AND PHOTOMAGNETISM IN EUROPIUM CHALCOGENIDES

The absorption threshold in EuTe and EuSe was investigated as a function of applied magnetic field in the Faraday geometry. A well-resolved doublet of sharp dichroic lines was observed when the magnetic field induced ferromagnetic alignment of the spins in the crystal lattice. In contrast, at zero magnetic field only a broad and featureless absorption onset is seen. These results are fully explained in terms of a model of electronic transitions between localized states at the Eu lattice site and a tight-binding conduction band, which incorporates the formation of spin domains. Based on this model, predictions are made concerning the possibility of inducing magnetization of the spin lattices by illuminating the material with circularly polarized light.

UV optical absorption spectra analysis of beryl crystals from Brazil

The spectral decomposition analysis was applied to the optical absorption spectra of green and colorless beryl crystals from the Brazilian Eastern Pegmatitic province in the natural state, Submitted to heat treatment and irradiated with UV light The attributions of the lines were made taking into account highly accurate quantum mechanical calculations The deconvolution of the green beryl spectra revealed four lines, two of them around 12,000 cm(-1) (1 5eV) and two of them around 34,000 cm(-1) (4.2 eV) attributed to Fe(2+) and Fe(3+), respectively The deconvolution of the colorless beryl spectra without any treatment, after heating and for the same heat treatment followed by UV light irradiation revealed five lines The analysis of ratio relations showed that the lines at 36,400 cm(-1) (4.5 eV) and 41,400 cm(-1) (5 1 eV) belongs to a single defect attributed to a silicon dangling bond defect (=Si). Discussions and comparison with reported defects in quartz have supported the allocation of the lines at 61,000 cm(-1) (7.6 eV) and 43,800 cm(-1) (5 4 eV) to diamagnetic oxygen vacancy defect ( Si-Si ) and unrelaxed ( Si Si ) defect, respectively Finally, the line at 39.100 cm(-1) (4.8 eV), quite polarized along the c-axis, was attributed to a (Fe(2+) OH(-)) defect in the structural channels (C) 2009 Elsevier B V All rights reserved