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

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

doi:10.1007/bf00992975

Cited by 108 publications

(69 citation statements)

References 25 publications

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“…These data indicate that the nitrifying community produced nitrate at the expense of organic rather than inorganic sources of ammonia. We are confident that we accurately determined PNA rates in the present study because of the following: (i) the average rates of PNA were similar to those observed by Fenn and colleagues for the same soils sampled in 1994 (17), (ii) the rates of PNA were mostly higher than those measured in other acidic forest soils (33,37,40), and (iii) acetylene completely inhibited a very high rate of PNA in a fertilized sandy soil control (Fig. 3).…”

Section: Discussionsupporting

confidence: 53%

“…Together, our observations indicate that other microbial populations or other processes besides those involving autotrophic AOB were likely responsible for relatively high PNA rates in CP and SP soils, whereas low PNA rates in the less N-impacted DW soil were predominantly catalyzed by autotrophic AOB. Low autotrophic AOB activities were also observed in mixed-conifer forest soils in the Sierra Nevada Mountains in California, where nitrification activity was only partially inhibited by acetylene (40). This study used 15 N pool dilution techniques to demonstrate that inorganic ammonia was not the substrate for nitrate accumulation in mature forest soils.…”

Section: Discussionmentioning

confidence: 99%

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Autotrophic Ammonia-Oxidizing Bacteria Contribute Minimally to Nitrification in a Nitrogen-Impacted Forested Ecosystem

Jordan

Cantera

Fenn

et al. 2005

Appl Environ Microbiol

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Deposition rates of atmospheric nitrogenous pollutants to forests in the San Bernardino Mountains range east of Los Angeles, California, are the highest reported in North America. Acidic soils from the west end of the range are N-saturated and have elevated rates of N-mineralization, nitrification, and nitrate leaching. We assessed the impact of this heavy nitrogen load on autotrophic ammonia-oxidizing communities by investigating their composition, abundance, and activity. Analysis of 177 cloned ␤-Proteobacteria ammonia oxidizer 16S rRNA genes from highly to moderately N-impacted soils revealed similar levels of species composition; all of the soils supported the previously characterized Nitrosospira clusters 2, 3, and 4. Ammonia oxidizer abundance measured by quantitative PCR was also similar among the soils. However, rates of potential nitrification activity were greater for N-saturated soils than for soils collected from a less impacted site, but autotrophic (i.e., acetylene-sensitive) activity was low in all soils examined. N-saturated soils incubated for 30 days with ammonium accumulated additional soluble ammonium, whereas less-N-impacted soils had a net loss of ammonium. Lastly, nitrite production by cultivated Nitrosospira multiformis, an autotrophic ammonia-oxidizing bacterium adapted to relatively high ammonium concentrations, was significantly inhibited in pH-controlled slurries of sterilized soils amended with ammonium despite the maintenance of optimal ammonia-oxidizing conditions. Together, these results showed that factors other than autotrophic ammonia oxidizers contributed to high nitrification rates in these N-impacted forest soils and, unlike many other environments, differences in nitrogen content and soil pH did not favor particular autotrophic ammonia oxidizer groups.

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Section: Discussionsupporting

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Autotrophic Ammonia-Oxidizing Bacteria Contribute Minimally to Nitrification in a Nitrogen-Impacted Forested Ecosystem

Jordan

Cantera

Fenn

et al. 2005

Appl Environ Microbiol

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“…Heterotrophic nitrification is likely to be performed by fungi characterized by higher microbial C:N ratios than bacteria (Landi et al 1993, Paul andClark 1996), which coincides with our finding of high microbial C:N ratios during key periods of gross nitrification (Table 2). Heterotrophic nitrification has been reported to dominate over autotrophic nitrification in several soils ranging from various forest ecosystems (Burton et al 2007, Grenon et al 2004, Pedersen et al 1999, Koyama et al 2010) to grassland (Cookson et al 2006, Mü ller et al 2002, 2009, Rü tting et al 2008. Nonetheless, the actual contribution of heterotrophic nitrification to total gross nitrification remains unclear in our as well as in most other studies, unless 15 NO 3 À pool dilution studies combined with selective inhibitors of autotrophic or heterotrophic nitrification (Barraclough and Puri 1995) are performed.…”

Section: Environmental Controls Of Gross N Turnovercontrasting

confidence: 41%

Seasonality of soil microbial nitrogen turnover in continental steppe soils of Inner Mongolia

Dannenmann

Wolf

et al. 2012

Ecosphere

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). Four different seasons with characteristic functional patterns of N turnover were identified: (1) Growing season dynamics as characterized by drying/rewetting cycles and negatively correlated temporal courses of net microbial growth and periods with intensive gross ammonification, contributing 40-52% and 29-32% to cumulative annual gross ammonification and nitrification, respectively. Net N mineralization was almost exclusively observed during the growing season. (2) Microbial N dynamics during the autumn freeze-thaw period was characterized by a sharp decline in microbial biomass in conjunction with a peak of gross nitrification contributing 19-36% to cumulative annual fluxes. (3) During winter at constantly frozen soil, a net build-up of microbial biomass was observed, whereas gross N turnover rates were low, contributing 7-10% and 6-11% to cumulative annual gross ammonification or gross nitrification, respectively. (4) The spring freeze-thaw period showed extremely dynamic changes in gross N turnover and soil nitrate concentrations. This period contributed 34-44% and 21-46% to cumulative annual gross ammonification and nitrification, respectively. This study highlights that freeze-thaw cycles are key periods for understanding patterns and magnitudes of gross N turnover in semi-arid continental steppe ecosystems. The results further imply that the observed patterns of microbial biomass and gross N turnover dynamics are likely the consequence of a seasonal succession of microbial communities and turnover of microbial biomass. Our findings emphasize the necessity for high resolution studies on gross N turnover as a prerequisite to infer functioning and annual budgets of ecosystem N cycling.

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“…This population density is 40-to 150-fold greater than the average MPN values obtained from the forest soil samples at Carpenter (ϳ1,000 g of soil Ϫ1 ) and far greater than the estimates made at Lookout. Although such discrepancies indicate that heterotrophic nitrification might be a source of oxidized nitrogen in these coniferous forest soil environments (35), our finding that acetylene completely inhibited NPRs across all transect positions suggests this was likely to be autotrophic nitrification. In this context, others have shown that the size of populations of AOB determined by quantitative PCR can be 10 to 500 times greater than values determined by traditional MPN methods (28,36).…”

Section: Discussionmentioning

confidence: 47%

Ammonia-Oxidizing Bacteria along Meadow-to-Forest Transects in the Oregon Cascade Mountains

Mintie¹,

Heichen²,

Cromack³

et al. 2003

Appl Environ Microbiol

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and CfoI135) were found more frequently in meadow and transition zone soil samples than in forest samples at both sites. At the Lookout site the combination AluI491-CfoI135 was found primarily in meadow samples expressing the highest N mineralization rates. Four unique amoA sequences were identified among 15 isolates recovered into pure culture from various transect locations. Six isolates possessed the most common T-RFLP amoA fingerprint of the soil samples (TaqI283-AluI392-CfoI66), and their amoA sequences shared 99.8% similarity with a cultured species, Nitrosospira sp. strain Ka4 (cluster 4). The other three amoA sequences were most similar to sequences of Nitrosospira sp. strain Nsp1 and Nitrosospira briensis (cluster 3). 16S ribosomal DNA sequence analysis confirmed the affiliation of these isolates with Nitrosospira clusters 3 and 4. Two amoA clone sequences matched T-RFLP fingerprints found in soil, but they were not found among the isolates.For many years the process of nitrification was thought to play a minimal role in N cycling in coniferous forest ecosystems. Based on the physiological properties of a limited number of NH 3 -oxidizing bacteria (AOB) in pure culture, several soil factors were considered detrimental to them, including soil acidity, high C/N ratios, low N availability, and the presence of allelochemical compounds (12,13,22,38,39,49,54). With the advent of improved 15 N tracer methods and mass spectrometric technology, N cycling processes were shown to be tightly coupled in forest soils and that both nitrification and NO 3 Ϫ assimilation can occur simultaneously with mineralization and ammonification (11,15,45,53). These observations stimulated interest in learning more about the nature and physiological ecology of AOB in forest ecosystems (12,14,30,44,51).In recent years, considerable progress has been made in elucidating the composition of AOB communities in soil by taking advantage of variation in gene sequences of either 16S ribosomal DNA (rDNA) or the catalytic subunit of NH 3 monooxygenase, amoA (2,19,37,40). Most research has focused on grasslands and agroecosystems where, in general, soil populations are dominated by the genus Nitrosospira rather than by the widely studied genus Nitrosomonas (4, 8, 24-28, 36, 47, 48). Nitrosospira can be grouped into several phylogenetically distinct clusters (3, 25), with cluster 3 being widely distributed in agricultural soils with high N availability (8,18,27,28,55). Clusters 1, 2, and 4 are more prevalent in soils that are either acidic (47, 48), retired from agricultural use (27, 28), or that were never exposed to tillage and/or applications of N fertilizer (8, 55).The objective of the present study was to examine the nature of the AOB communities associated with soil along high-elevation (ϳ1,500 m) meadow-to-forest transects at two sites in the H. J. Andrews Experimental Forest of Oregon. We hypothesized that these transects would provide a gradient along which differences in vegetation composition and plant N inputs interacting with chang...

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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

Cited by 108 publications

References 25 publications

Autotrophic Ammonia-Oxidizing Bacteria Contribute Minimally to Nitrification in a Nitrogen-Impacted Forested Ecosystem

Autotrophic Ammonia-Oxidizing Bacteria Contribute Minimally to Nitrification in a Nitrogen-Impacted Forested Ecosystem

Seasonality of soil microbial nitrogen turnover in continental steppe soils of Inner Mongolia

Ammonia-Oxidizing Bacteria along Meadow-to-Forest Transects in the Oregon Cascade Mountains

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