[1] Isotopomer ratios of N 2 O (bulk nitrogen and oxygen isotope ratios, d 15 N bulk and d 18 O, and intramolecular 15 N site preference, SP) are useful parameters that characterize sources of this greenhouse gas and also provide insight into production and consumption mechanisms. We measured isotopomer ratios of N 2 O emitted from typical Japanese agricultural soils (Fluvisols and Andisols) planted with rice, wheat, soybean, and vegetables, and treated with synthetic (urea or ammonium) and organic (poultry manure) fertilizers. The results were analyzed using a previously reported isotopomeric N 2 O signature produced by nitrifying/denitrifying bacteria and a characteristic relationship between d 15 N bulk and SP during N 2 O reduction by denitrifying bacteria. Relative contributions from nitrification (hydroxylamine oxidation) and denitrification (nitrite reduction) to gross N 2 O production deduced from the analysis depended on soil type and fertilizer. The contribution from nitrification was relatively high (40%-70%) in Andisols amended with synthetic ammonium fertilizer, while denitrification was dominant (50%-90%) in the same soils amended with poultry manure during the period when N 2 O production occurred in the surface layer. This information on production processes is in accordance with that obtained from flux/concentration analysis of N 2 O and soil inorganic nitrogen. However, isotopomer analysis further revealed that partial reduction of N 2 O was pronounced in high-bulk density, alluvial soil (Fluvisol) compared to low-bulk density, volcanic ash soil (Andisol), and that the observed difference in N 2 O flux between normal and pelleted manure could have resulted from a similar mechanism with different rates of gross production and gross consumption. The isotopomeric analysis is based on data from pure culture bacteria and would be improved by further studies on in situ biological processes in soils including those by fungi. When flux/concentration-weighted average isotopomer ratios of N 2 O from various fertilized soils were examined, linear correlations were found between d 15 N bulk and d 18 O, and between SP and d 15 N bulk . These relationships would be useful to parameterize isotopomer ratios of soil-emitted N 2 O for the modeling of the global N 2 O isotopomer budget. The results obtained in this study and those from previous firn/ice core studies confirm that the principal source of anthropogenic N 2 O is fertilized soils.Citation: Toyoda, S., et al. (2011), Characterization and production and consumption processes of N 2 O emitted from temperate agricultural soils determined via isotopomer ratio analysis, Global Biogeochem. Cycles, 25, GB2008,
In this paper we give local normal forms of generic implicit first order ordinary differential equations with independent first integrals. The classification problem in this case is reduced to classifying a certain class of divergent diagrams of map-germs; integral diagrams. The main tools are Legendre singularity theory and differential analysis. We also discuss the relation between previous works and the results obtained in this paper.
We evaluated the impacts of natural wetlands and various land uses on stream nitrogen concentration in two grassland-dominated catchments in eastern Hokkaido, Japan. Analyzing land use types in drainage basins, measuring denitrification potential of its soil, and water sampling in all seasons of 2003 were performed. Results showed a highly significant positive correlation between the concentration of stream NO3-N and the proportion of upland area in drainage basins in both catchments. The regression slope, which we assumed to reflect the impact on water quality, was 24% lower for the Akkeshi catchment (0.012 +/- 0.001) than for the Shibetsu catchment (0.016 +/- 0.001). In the Akkeshi catchment, there was a significant negative correlation between the proportion of wetlands in the drainage basins and stream NO3-N concentration. Stream dissolved organic nitrogen (DON) and carbon (DOC) concentrations were significantly higher in the Akkeshi catchment. Upland and urban land uses were strongly linked to increases in in-stream N concentrations in both catchments, whereas wetlands and forests tended to mitigate water quality degradation. The denitrification potential of the soils was highest in wetlands, medium in riparian forests, and lowest in grasslands; and was significant in wetlands and riparian forests in the Akkeshi catchment. The solubility of soil organic carbon (SOC) and soil moisture tended to determine the denitrification potential. These results indicate that the water environment within the catchments, which influences denitrification potential and soil organic matter content, could have caused the difference in stream water quality between the two catchments.
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