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  • N-mineralization  (2)
  • Chemistry  (1)
  • N mineralizaton  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The relative importance of autotrophic and heterotrophic nitrification in a conifer forest soil as measured by 15N tracer and pool dilution techniques (1999)
    Springer
    Biogeochemistry 44 (1999), S. 135-150 
    Details
    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
    URL: http://dx.doi.org/10.1023/A:1006059930960
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  • 2
    Electronic Resource
    Electronic Resource
    The relative importance of autotrophic and heterotrophic nitrification in a conifer forest soil as measured by15N tracer and pool dilution techniques (1999)
    Springer
    Biogeochemistry 44 (1999), S. 135-150 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00992975
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  • 3
    Electronic Resource
    Electronic Resource
    Forest floor-mineral soil interactions in the internal nitrogen cycle of an old-growth forest (1991)
    Springer
    Biogeochemistry 12 (1991), S. 103-127 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00001809
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  • 4
    Electronic Resource
    Electronic Resource
    Toluene diffusion and reaction in unsaturated Pseudomonas putida biofilms (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 656-670 
    Details
    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.
    Type of Medium: Electronic Resource
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