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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 16 (2006): 2091–2122, doi:10.1890/1051-0761(2006)016[2091:MFMDDA]2.0.CO;2.
    Description: Denitrification, the reduction of the nitrogen (N) oxides, nitrate (NO3-) and nitrite (NO2-), to the gases nitric oxide (NO), nitrous oxide (N2O) and dinitrogen (N2), is important to primary production, water quality and the chemistry and physics of the atmosphere at ecosystem, landscape, regional and global scales. Unfortunately, this process is very difficult to measure, and existing methods are problematic for different reasons in different places at different times. In this paper, we review the major approaches that have been taken to measure denitrification in terrestrial and aquatic environments and discuss the strengths, weaknesses and future prospects for the different methods. Methodological approaches covered include; 1) acetylene-based methods, 2) 15N tracers, 3) direct N2 quantification, 4) N2/Ar ratio quantification, 5) mass balance approaches, 6) stoichiometric approaches, 7) methods based on stable isotopes, 8) in situ gradients with atmospheric environmental tracers and 9) molecular approaches. Our review makes it clear that the prospects for improved quantification of denitrification vary greatly in different environments and at different scales. While current methodology allows for the production of accurate estimates of denitrification at scales relevant to water and air quality and ecosystem fertility questions in some systems (e.g., aquatic sediments, well defined aquifers), methodology for other systems, especially upland terrestrial areas, still needs development. Comparison of mass balance and stoichiometric approaches that constrain estimates of denitrification at large scales with point measurements (made using multiple methods), in multiple systems, is likely to propel more improvement in denitrification methods over the next few years.
    Keywords: Denitrification ; Greenhouse effect ; Nitrate ; Nitric oxide nitrogen ; Nitrous oxide ; Stable isotopes ; Water quality
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: 822728 bytes
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 85 (1991), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Production of N2O was detected within 30 min of adding water to very dry soil (matric water potential 〈 −9 MPa) sampled at the end of the dry season from an annual grassland of California, U.S.A. Using C2H2 to inhibit nitrification, we demonstrate that nitrification was a modest source of N2O in sieved soil wetted to a water content below field capacity, but that denitrification was the major source of N2O in sieved soils wetted to a water content above field capacity and in intact cores wetted either below or above field capacity. Significant abiological sources of N2O were not detected. De novo enzyme synthesis began within 4–8 h of wetting, and denitrifying enzyme activity doubled within 26 h, indicating that denitrifying bacteria can quickly transform their metabolic state from adaptation to severe drought stress to rapid exploitation of changing resources.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Global change biology 11 (2005), S. 0 
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The impact of elevated CO2 on terrestrial ecosystem C balance, both in sign or magnitude, is not clear because the resulting alterations in C input, plant nutrient demand and water use efficiency often have contrasting impacts on microbial decomposition processes. One major source of uncertainty stems from the impact of elevated CO2 on N availability to plants and microbes. We examined the effects of atmospheric CO2 enrichment (ambient+370 μmol mol−1) on plant and microbial N acquisition in two different mesocosm experiments, using model plant species of annual grasses of Avena barbata and A. fatua, respectively. The A. barbata experiment was conducted in a N-poor sandy loam and the A. fatua experiment was on a N-rich clayey loam. Plant–microbial N partitioning was examined through determining the distribution of a 15N tracer. In the A. barbata experiment, 15N tracer was introduced to a field labeling experiment in the previous year so that 15N predominantly existed in nonextractable soil pools. In the A. fatua experiment, 15N was introduced in a mineral solution [(15NH4)2SO4 solution] during the growing season of A. fatua. Results of both N budget and 15N tracer analyses indicated that elevated CO2 increased plant N acquisition from the soil. In the A. barbata experiment, elevated CO2 increased plant biomass N by ca. 10% but there was no corresponding decrease in soil extractable N, suggesting that plants might have obtained N from the nonextractable organic N pool because of enhanced microbial activity. In the A. fatua experiment, however, the CO2-led increase in plant biomass N was statistically equal to the reduction in soil extractable N. Although atmospheric CO2 enrichment enhanced microbial biomass C under A. barbata or microbial activity (respiration) under A. fatua, it had no significant effect on microbial biomass N in either experiment. Elevated CO2 increased the colonization of A. fatua roots by arbuscular mycorrhizal fungi, which coincided with the enhancement of plant competitiveness for soluble soil N. Together, these results suggest that elevated CO2 may tighten N cycling through facilitating plant N acquisition. However, it is unknown to what degree results from these short-term microcosm experiments can be extrapolated to field conditions. Long-term studies in less-disturbed soils are needed to determine whether CO2-enhancement of plant N acquisition can significantly relieve N limitation over plant growth in an elevated CO2 environment.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 8 (1991), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-515X
    Keywords: autotrophic nitrification ; heterotrophic nitrification ; conifer forest ; N-mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The importance of heterotrophic nitrification was studied in soil from a mixed-conifer forest. Three sites in the forest were sampled: a clear cut area, a young stand and a mature stand. In the mature stand, the mineral soil (0–10 cm) and the organic layer were sampled separately. Gross rates of N mineralization and nitrification were measured by15NH 4 + and15NO 3 − isotopic pool dilution, respectively. The rates of autotrophic and heterotrophic nitrification were distinguished by use of acetylene as a specific inhibitor of autotrophic nitrification. In samples supplemented with15NH 4 + and treated with acetylene, no15NO 3 − was detectable showing that the acetylene treatment effectively blocked the autotrophic nitrification, and that NH 4 + was not a substrate for heterotrophic nitrification. In the clear cut area, autotrophic nitrification was the most important NO 3 − generating process with total nitrification (45 ug N kg−1h−1) accounting for about one-third of gross N mineralization (140 ug N kg−1 h−1). In the young and mature forested sites, gross nitrification rates were largely unaffected by acetylene treatment indicating that heterotrophic nitrification dominated the NO 3 − generating process in these areas. In the mature forest mineral and organic soil, nitrification (heterotrophic) was equal to only about 5% of gross mineralization (gross mineralization rates of 90 ug N kg−1 h−1 mineral; 550 ug N kg−1 h−1 organic). The gross nitrification rate decreased from the clear cut area to the young forest area to the mineral soil of the mature forest (45; 17; 4.5 ug kg−1 h−1 respectively). The15N isotope pool dilution method, combined with acetylene as an inhibitor of autotrophic nitrification provided an effective technique for assessing the importance of heterotrophic nitrification in the N-cycle of this mixed-conifer ecosystem.
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  • 6
    ISSN: 1573-515X
    Keywords: autotrophic nitrification ; heterotrophic nitrification ; conifer forest ; N-mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The importance of heterotrophic nitrification was studied in soil from a mixed-conifer forest. Three sites in the forest were sampled: a clear cut area, a young stand and a mature stand. In the mature stand, the mineral soil (0–10 cm) and the organic layer were sampled separately. Gross rates of N mineralization and nitrification were measured by 15NH4+ and 15NO3- isotopic pool dilution, respectively. The rates of autotrophic and heterotrophic nitrification were distinguished by use of acetylene as a specific inhibitor of autotrophic nitrification. In samples supplemented with 15NH4+ and treated with acetylene, no 15NO3- was detectable showing that the acetylene treatment effectively blocked the autotrophic nitrification, and that NH4+ was not a substrate for heterotrophic nitrification. In the clear cut area, autotrophic nitrification was the most important NO3- generating process with total nitrification (45 ug N kg- 1 h-1) accounting for about one-third of gross N mineralization (140 ug N kg-1 h-1). In the young and mature forested sites, gross nitrification rates were largely unaffected by acetylene treatment indicating that heterotrophic nitrification dominated the NO3- generating process in these areas. In the mature forest mineral and organic soil, nitrification (heterotrophic) was equal to only about 5% of gross mineralization (gross mineralization rates of 90 ug N kg-1 h-1 mineral; 550 ug N kg-1 h-1 organic). The gross nitrification rate decreased from the clear cut area to the young forest area to the mineral soil of the mature forest (45; 17; 4.5 ug kg-1 h-1 respectively). The 15N isotope pool dilution method, combined with acetylene as an inhibitor of autotrophic nitrification provided an effective technique for assessing the importance of heterotrophic nitrification in the N-cycle of this mixed-conifer ecosystem.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biogeochemistry 12 (1991), S. 103-127 
    ISSN: 1573-515X
    Keywords: fungal translocation ; microbial biomass ; 15N ; N leaching ; N mineralizaton ; nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Seasonal patterns and annual rates of N inputs, outputs, and internal cycling were determined for an old-growth mixed-conifer forest floor in the Sierra Nevada Mountains of California. Rates of net N mineralization within the forest floor, and plant N-uptake and leaching of inorganic N from the forest floor were 13, 10, and 9 kg-N ha-1 yr-1, respectively. The Mediterranean-type climate appeared to have a significant effect on N cycling within this forest, such that all N-process and flow rates showed distrinct seasonal patterns. We estimated the forest floor supplies less than one-third of the total aboveground plant N-uptake in this forest. The rate of net nitrification within the forest floor was always low (1 kg-NO3 --N ha-1 30d-1). Mean residence times for organic matter and N in the forest floor were 13 and 34 years, respectively, suggesting that this forest floor layer is a site of net N immobilization within this ecosystem. We examined the influence of the forest floor on mineral soil N dynamics by injecting small amounts of15N-enriched (NH4)2SO4 solutions into the surface mineral soil with the forest floor present (+FF) or removed (-FF). K2SO4-extractable NO3 --N, total inorganic-N, and total-N pool sizes in the mineral soil were initially increased after forest floor removal (after 4 months), but NO3 --N and total inorganic-N were not significantly different thereafter. Microbial biomass-N and K2SO4-extractable total-N pool sizes were also found to be larger in mineral soils without a forest floor after 1 and 1.3 years, respectively. Total15N-recovery was greater in the +FF treatment compared to the -FF treatment after 1-year (about 50% and 35%, respectively) but did not differ after 1.3 years (both about 35%), suggesting that the forest floor delays but does not prevent the N-loss from the surface mineral soil of this forest. We estimated using our15N data that fungal translocation from the mineral soil to the forest floor may be as large as 9 kg-N ha-1 yr-1 (similar in magnitude to other N flows in this forest), and may account for all of the observed absolute increase of N in litter during the early stages of decomposition at this site. Our results suggest that the forest floor acts both as a source and sink for N in the mineral soil.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Biodegradation 8 (1997), S. 143-151 
    ISSN: 1572-9729
    Keywords: matric potential ; Pseudomonas putida ; toluene ; water potential ; water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We quantified the effects of matric and solute waterpotential on toluene biodegradation by Pseudomonasputida mt-2, a bacterial strain originally isolated fromsoil. Across the matric potential range of 0 to – 1.5 MPa,growth rates were maximal for P. putida at – 0.25MPa and further reductions in the matric potentialresulted in concomitant reductions in growth rates.Growth rates were constant over the solute potential range0 to – 1.0 MPa and lower at – 1.5 MPa. First ordertoluene depletion rate coefficients were highest at0.0 MPa as compared to other matric water potentialsdown to – 1.5 MPa. Solute potentials down to – 1.5 MPadid not affect first order toluene depletion ratecoefficients. Total yield (protein) and carbon utilizationefficiency were not affected by water potential, indicatingthat water potentials common to temperate soils were notsufficiently stressful to change cellular energyrequirements. We conclude that for P. putida: (1)slightly negative matric potentials facilitate faster growthrates on toluene but more negative water potentials resultin slower growth, (2) toluene utilization rate per cell massis highest without matric water stress and is unaffected bysolute potential, (3) growth efficiency did not differ acrossthe range of matric water potentials 0.0 to – 1.5 MPa.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 60 (1991), S. 301-313 
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Effects of simulated acid rain, comprised of HNO3 and H2SO4 in the mole ratio of 3:1, at pH 5.6, 4.5, 4.0 and 3.0, were tested on the grass, soft chess (Bromus mollis L.) and on clover (Trifolium subterraneum L. var. Woogenellup) in a sandy soil of granodiorite parent material. Soft chess was grown in unfertilized soil, whereas clover was grown in both unfertilized soil and soil fertilized with NH4NO3 and CaSO4·2H2O at the rates of 224 kg ha−1 N and 78 kg ha−1 S. Two acid-spray irrigation periods of 31 and 26 weeks duration, each delivering 400 mm and separated by a dry period of 23 weeks, simulated typical rainfall of northern California rangeland. Plants were harvested after each of the two spray periods. There were very few deleterious effects of acid rain on plant growth or soil and microbial processes. No significant (p〈0.05) effects were shown by soil microbial biomass, CO2 production, nodules per unit weight of clover root, acetylene reduction, denitrification and nitrification potentials, or for soft chess plant weights, and N and P uptake. Mineralizable-N was unaffected also, except in one case. However, pH of soil to 10 mm depths was significantly lower in the pH 3.0 treatment after the first spray period, with a corresponding decrease in exchangeable soil Ca; these effects became significant at greater soil depth only after the second spray period. There were significant effects of acid treatments shown by clover, some of which may be advantageous. Treatments of intermediate acidity generally provided added N and S, which acted as fertilizers, and compensated for possible decreases in plant productivity attributable to acidity per se. There was also evidence of decreased P uptake in unfertilized soil at pH 3. In conclusion, effects of simulated acid rain were minimal, and in some cases were advantageous because of the added N and S having a fertilizer effect on plant nutrition and growth.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 656-670 
    ISSN: 0006-3592
    Keywords: unsaturated biofilm ; diffusion ; substrate utilization kinetics ; matric water potential ; toluene ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biofilms are frequently studied in the context of submerged or aquatic systems. However, much less is known about biofilms in unsaturated systems, despite their importance to such processes as food spoilage, terrestrial nutrient cycling, and biodegradation of environmental pollutants in soils. Using modeling and experimentation, we have described the biodegradation of toluene in unsaturated media by bacterial biofilms as a function of matric water potential, a dominant variable in unsaturated systems. We experimentally determined diffusion and kinetic parameters for Pseudomonas putida biofilms, then predicted biodegradation rates over a range of matric water potentials. For validation, we measured the rate of toluene depletion by intact biofilms and found the results to reasonably follow the model predictions. The diffusion coefficient for toluene through unsaturated P. putida biofilm averaged 1.3 × 107 cm2/s, which is approximately two orders of magnitude lower than toluene diffusivity in water. Our studies show that, at the scale of the microbial biofilm, the diffusion of toluene to biodegrading bacteria can limit the overall rate of biological toluene depletion in unsaturated systems. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 656-670, 1997.
    Additional Material: 8 Ill.
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