Investigating uptake of N2O in agricultural soils using a high-precision dynamic chamber method

Uptake (or negative flux) of nitrous oxide (N2O)in agricultural soils is a controversial issue which has proved difficult to investigate in the past due to constraints such as instrumental precision and methodological uncertainties. Using a recently developed high-precision quantum cascade laser gas analyser combined with a closed dynamic chamber, a well-defined detection limit of 4 μg N2O-N m could be achieved for individual soil flux measurements. 1220 mea- surements of N2O flux were made from a variety of UK soils using this method, of which 115 indicated uptake by the soil (i.e. a negative flux in the micrometeorological sign convention). Only four of these apparently negative fluxes were greater than the detection limit of the method, which suggests that the vast majority of reported negative fluxes from such measurements are actually due to instrument noise. As such, we suggest that the bulk of negative N2O fluxes reported for agricultural fields are most likely due to limits in detection of a particular flux measurement methodology and not a result of microbiological activity consuming atmospheric N2O

Nitrous oxide emissions from European agriculture - An analysis of variability and drivers of emissions from field experiments

Nitrous oxide emissions from a network of agricultural experiments in Europe were used to explore the relative importance of site and management controls of emissions. At each site, a selection of management interventions were compared within replicated experimental designs in plot-based experiments. Arable experiments were conducted at Beano in Italy, El Encin in Spain, Foulum in Denmark, Logården in Sweden, Maulde in Belgium, Paulinenaue in Germany, and Tulloch in the UK. Grassland experiments were conducted at Crichton, Nafferton and Peaknaze in the UK, Gödöllö in Hungary, Rzecin in Poland, Zarnekow in Germany and Theix in France. Nitrous oxide emissions were measured at each site over a period of at least two years using static chambers. Emissions varied widely between sites and as a result of manipulation treatments. Average site emissions (throughout the study period) varied between 0.04 and 21.21 kg N₂O-N ha⁻¹ yr⁻¹, with the largest fluxes and variability associated with the grassland sites. Total nitrogen addition was found to be the single most important determinant of emissions, accounting for 15% of the variance (using linear regression) in the data from the arable sites (<i>p</i> < 0.0001), and 77% in the grassland sites. The annual emissions from arable sites were significantly greater than those that would be predicted by IPCC default emission factors. Variability of N₂O emissions within sites that occurred as a result of manipulation treatments was greater than that resulting from site-to-site and year-to-year variation, highlighting the importance of management interventions in contributing to greenhouse gas mitigation

The potential for tree planting strategies to reduce local and regional ecosystem impacts of agricultural ammonia emissions

Trees are very effective at capturing both gaseous and particulate pollutants from the atmosphere. But while studies have often focussed on PM and NOx in the urban environment, little research has been carried out on the tree effect of capturing gaseous emissions of ammonia in the rural landscape. To examine the removal or scavenging of ammonia by trees a long-range atmospheric model (FRAME) was used to compare two strategies that could be used in emission reduction policies anywhere in the world where nitrogen pollution from agriculture is a problem. One strategy was to reduce the emission source strength of livestock management systems by implementing two ‘tree-capture’ systems scenarios – tree belts downwind of housing and managing livestock under trees. This emission reduction can be described as an ‘on-farm’ emission reduction policy, as ammonia is ‘stopped’ from dispersion outside the farm boundaries. The second strategy was to apply an afforestation policy targeting areas of high ammonia emission through two planting scenarios of increasing afforestation by 25% and 50%. Both strategies use trees with the aim of intercepting NH3 emissions to protect semi-natural areas. Scenarios for on-farm emission reductions showed national reductions in nitrogen deposition to semi-natural areas of 0.14% (0.2 kt N–NHx) to 2.2% (3.15 kt N–NHx). Scenarios mitigating emissions from cattle and pig housing gave the highest reductions. The afforestation strategy showed national reductions of 6% (8.4 kt N–NHx) to 11% (15.7 kt N–NHx) for 25% and 50% afforestation scenarios respectively. Increased capture by the planted trees also showed an added benefit of reducing long range effects including a decrease in wet deposition up to 3.7 kt N–NHx (4.6%) and a decrease in export from the UK up to 8.3 kt N–NHx (6.8%)

Nitrogen - grasping the challenge. A manifesto for science-in-action through the International Nitrogen Management System. Summary report

Report published by Centre for Ecology & Hydrology, Edinburgh, UK on behalf of the International Nitrogen Management System (INMS). Freely available to download from the Official link

The genetic architecture of the human cerebral cortex

INTRODUCTION The cerebral cortex underlies our complex cognitive capabilities. Variations in human cortical surface area and thickness are associated with neurological, psychological, and behavioral traits and can be measured in vivo by magnetic resonance imaging (MRI). Studies in model organisms have identified genes that influence cortical structure, but little is known about common genetic variants that affect human cortical structure. RATIONALE To identify genetic variants associated with human cortical structure at both global and regional levels, we conducted a genome-wide association meta-analysis of brain MRI data from 51,665 individuals across 60 cohorts. We analyzed the surface area and average thickness of the whole cortex and 34 cortical regions with known functional specializations. RESULTS We identified 306 nominally genome-wide significant loci (P < 5 × 10−8) associated with cortical structure in a discovery sample of 33,992 participants of European ancestry. Of the 299 loci for which replication data were available, 241 loci influencing surface area and 14 influencing thickness remained significant after replication, with 199 loci passing multiple testing correction (P < 8.3 × 10−10; 187 influencing surface area and 12 influencing thickness). Common genetic variants explained 34% (SE = 3%) of the variation in total surface area and 26% (SE = 2%) in average thickness; surface area and thickness showed a negative genetic correlation (rG = −0.32, SE = 0.05, P = 6.5 × 10−12), which suggests that genetic influences have opposing effects on surface area and thickness. Bioinformatic analyses showed that total surface area is influenced by genetic variants that alter gene regulatory activity in neural progenitor cells during fetal development. By contrast, average thickness is influenced by active regulatory elements in adult brain samples, which may reflect processes that occur after mid-fetal development, such as myelination, branching, or pruning. When considered together, these results support the radial unit hypothesis that different developmental mechanisms promote surface area expansion and increases in thickness. To identify specific genetic influences on individual cortical regions, we controlled for global measures (total surface area or average thickness) in the regional analyses. After multiple testing correction, we identified 175 loci that influence regional surface area and 10 that influence regional thickness. Loci that affect regional surface area cluster near genes involved in the Wnt signaling pathway, which is known to influence areal identity. We observed significant positive genetic correlations and evidence of bidirectional causation of total surface area with both general cognitive functioning and educational attainment. We found additional positive genetic correlations between total surface area and Parkinson’s disease but did not find evidence of causation. Negative genetic correlations were evident between total surface area and insomnia, attention deficit hyperactivity disorder, depressive symptoms, major depressive disorder, and neuroticism. CONCLUSION This large-scale collaborative work enhances our understanding of the genetic architecture of the human cerebral cortex and its regional patterning. The highly polygenic architecture of the cortex suggests that distinct genes are involved in the development of specific cortical areas. Moreover, we find evidence that brain structure is a key phenotype along the causal pathway that leads from genetic variation to differences in general cognitive function

Temperature dependence of inorganic nitrogen utilisation by bacteria and microalgae

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN022745 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Soil properties and soil greenhouse gas emissions in biochar-amended bioenergy soils incubated under controlled laboratory conditions

Data from an investigation of the effects of biochar application to soil on greenhouse gas emissions using soil from a bioenergy crop (Miscanthus X. giganteus). Data include physical (bulk density) and chemical analyses of the soil (total carbon (C) and nitrogen (N), extractable ammonium and nitrate), and greenhouse gas (GHG) emissions (carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)) during incubations. Data were collected during two incubation experiments investigating the effects of temperature, soil moisture and soil aeration on biochar induced suppression of GHG emissions. Biochar is a carbon rich substances which is being advocated as a climate mitigation tool to increase carbon sequestration and reduce nitrous oxide emissions

Global Nitrogen Deposition and Carbon Sinks

Elevated rates of reactive nitrogen deposition have been invoked as an explanation for significant increases in global carbon sinks. Deposition rates to both land and the oceans are projected to alter markedly during the 21st century and so may play a significant role in determining the future growth rate of atmospheric CO2. Here we examine the evidence for reactive nitrogen input as a key determinant of enhanced biospheric carbon storage in the past and in the decades to come.JRC.H.2-Climate chang

Soil properties and soil greenhouse gas emissions in biochar-amended bioenergy soils undergoing long term field incubation.

Data collected during field and laboratory experiments to investigate the long-term effects of biochar application to soil on greenhouse gas emissions in a bioenergy plantation (Miscanthus X. giganteus). Analysis included monitoring of greenhouse gas emissions (carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)), soil physical (bulk density and soil moisture ) and soil chemical analyses (total carbon (C) and nitrogen (N), extractable ammonium and nitrate). Biochar was applied to plots in a bioenergy plantation and emissions of CO2, CH4 and N2O were measured over a 2 year period. In addition a laboratory incubation experiment was conducted on soil taken from the Miscanthus field amended with field-incubated biochar to assess the effect on greenhouse gas emissions. Biochar is a carbon rich substances which is being advocated as a climate mitigation tool to increase carbon sequestration and reduce nitrous oxide emissions

Global agriculture and nitrous oxide emissions

Nitrous oxide (N2O) is an important anthropogenic greenhouse gas and agriculture represents its largest source. It is at the heart of debates over the efficacy of biofuels, the climate-forcing impact of population growth, and the extent to which mitigation of non-CO2 emissions can help avoid dangerous climate change. Here we examine some of the major debates surrounding estimation of agricultural N2O sources, and the challenges of projecting and mitigating emissions in coming decades. We find that current flux estimates - using either top-down or bottom-up methods - are reasonably consistent at the global scale, but that a dearth of direct measurements in some areas makes national and sub-national estimates highly uncertain. We also highlight key uncertainties in projected emissions and demonstrate the potential for dietary choice and supply-chain mitigation.JRC.H.2-Air and Climat