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1

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Water stress effects on toluene biodegradation by Pseudomonas putida (1997)

Holden, Patricia A. ; Halverson, Larry J. ; Firestone, Mary K.

Springer

Biodegradation 8 (1997), S. 143-151

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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

URL: http://dx.doi.org/10.1023/A:1008237819089

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The relative importance of autotrophic and heterotrophic nitrification in a conifer forest soil as measured by 15N tracer and pool dilution techniques (1999)

Pedersen, Henning ; Dunkin, Kristie A. ; Firestone, Mary K.

Springer

Biogeochemistry 44 (1999), S. 135-150

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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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3

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The relative importance of autotrophic and heterotrophic nitrification in a conifer forest soil as measured by15N tracer and pool dilution techniques (1999)

Pedersen, Henning ; Dunkin, Kristie A. ; Firestone, Mary K.

Springer

Biogeochemistry 44 (1999), S. 135-150

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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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4

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Forest floor-mineral soil interactions in the internal nitrogen cycle of an old-growth forest (1991)

Hart, Stephen C. ; Firestone, Mary K.

Springer

Biogeochemistry 12 (1991), S. 103-127

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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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5

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Soil chemical and microbial effects of simulated acid rain on clover and soft chess (1991)

McColl, John G. ; Firestone, Mary K.

Springer

Water, air & soil pollution 60 (1991), S. 301-313

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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.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00282629

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