Stimulation of ammonia oxidizer and denitrifier abundances by nitrogen loading: Poor predictability for increased soil N 2 O emission

Abstract. Nitrogen (N) deposition is generally considered to increase soil nitrous oxide (N2O) emission in N-rich forests. In many tropical forests, however, elevated N deposition has caused soil N enrichment and further phosphorus (P) deficiency, and the interaction of N and P to control soil N2O emission remains poorly understood, particularly in forests with different soil N status. In this study, we examined the effects of N and P additions on soil N2O emission in an N-rich old-growth forest and two N-limited younger forests (a mixed and a pine forest) in southern China to test the following hypotheses: (1) soil N2O emission is the highest in old-growth forest due to the N-rich soil; (2) N addition increases N2O emission more in the old-growth forest than in the two younger forests; (3) P addition decreases N2O emission more in the old-growth forest than in the two younger forests; and (4) P addition alleviates the stimulation of N2O emission by N addition. The following four treatments were established in each forest: Control, N addition (150 kg N ha−1 yr−1), P addition (150 kg P ha−1 yr−1), and NP addition (150 kg N ha−1 yr−1 plus 150 kg P ha−1 yr−1). From February 2007 to October 2009, monthly quantification of soil N2O emission was performed using static chamber and gas chromatography techniques. Mean N2O emission was shown to be significantly higher in the old-growth forest (13.9 ± 0.7 µg N2O-N m−2 h−1) than in the mixed (9.9 ± 0.4 µg N2O-N m−2 h−1) or pine (10.8 ± 0.5 µg N2O-N m−2 h−1) forests, with no significant difference between the latter two. N addition significantly increased N2O emission in the old-growth forest but not in the two younger forests. However, both P and NP addition had no significant effect on N2O emission in all three forests, suggesting that P addition alleviated the stimulation of N2O emission by N addition in the old-growth forest. Although P fertilization may alleviate the stimulated effects of atmospheric N deposition on N2O emission in N-rich forests, this effect may only occur under high N deposition and/or long-term P addition, and we suggest future investigations to definitively assess this management strategy and the importance of P in regulating N cycles from regional to global scales.

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Do warming-induced changes in quantity and stoichiometry of root exudation promote soil N transformations via stimulation of soil nitrifiers, denitrifiers and ammonifiers?

European Journal of Soil Biology ◽

10.1016/j.ejsobi.2016.03.007 ◽

2016 ◽

Vol 74 ◽

pp. 60-68 ◽

Cited By ~ 17

Author(s):

Ziliang Zhang ◽

Mingfeng Qiao ◽

Dandan Li ◽

Huajun Yin ◽

Qing Liu

Keyword(s):

Root Exudation ◽

Soil N ◽

N Transformations ◽

Induced Changes ◽

Stimulation Of

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Strategies to Overcome Intermediate Accumulation During in situ Nitrate Remediation in Groundwater by Hydrogenotrophic Denitrification

Frontiers in Microbiology ◽

10.3389/fmicb.2021.610437 ◽

2021 ◽

Vol 12 ◽

Author(s):

Clara Duffner ◽

Anja Wunderlich ◽

Michael Schloter ◽

Stefanie Schulz ◽

Florian Einsiedl

Keyword(s):

Aquatic Ecosystems ◽

Food Production ◽

Environmental Science ◽

Nitrogen Loading ◽

Groundwater Systems ◽

Lag Times ◽

Agriculture And Food ◽

The Eu ◽

Stimulation Of

Bioremediation of polluted groundwater is one of the most difficult actions in environmental science. Nonetheless, the clean-up of nitrate polluted groundwater may become increasingly important as nitrate concentrations frequently exceed the EU drinking water limit of 50 mg L–1, largely due to intensification of agriculture and food production. Denitrifiers are natural catalysts that can reduce increasing nitrogen loading of aquatic ecosystems. Porous aquifers with high nitrate loading are largely electron donor limited and additionally, high dissolved oxygen concentrations are known to reduce the efficiency of denitrification. Therefore, denitrification lag times (time prior to commencement of microbial nitrate reduction) up to decades were determined for such groundwater systems. The stimulation of autotrophic denitrifiers by the injection of hydrogen into nitrate polluted regional groundwater systems may represent a promising remediation strategy for such environments. However, besides high costs other drawbacks, such as the transient or lasting accumulation of the cytotoxic intermediate nitrite or the formation of the potent greenhouse gas nitrous oxide, have been described. In this article, we detect causes of incomplete denitrification, which include environmental factors and physiological characteristics of the underlying bacteria and provide possible mitigation approaches.

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Stimulation of root growth and soil nitrogen uptake by foliar application of urea to wheat and sunflower

The Journal of Agricultural Science ◽

10.1017/s0021859600073056 ◽

1996 ◽

Vol 126 (2) ◽

pp. 127-135 ◽

Cited By ~ 4

Author(s):

S. Sen ◽

P. M. Chalk

Keyword(s):

Soil Nitrogen ◽

Root Biomass ◽

Dry Matter ◽

Foliar Application ◽

Urea Solution ◽

Soil N ◽

Clay Loam ◽

Limited Effectiveness ◽

N Status ◽

Stimulation Of

SUMMARYWheat and sunflower plants were grown in a temperature-controlled glasshouse in Melbourne, Australia (37° 50′ S, 145° 00′ E), from 9 August to 2 October 1991, in cylinders containing two soils (Walpeup loamy sand (LS) and Gombalin clay loam (CL)) of low and moderate N status, respectively. Nitrogen fertilizer was applied by immersion of leaves in 0·18 M urea solution (10·5 atom% 15N).Plants were N-deficient in the Walpeup LS but not in the Gombalin CL soils. Both species had higher root: shoot ratios, and higher proportions of foliar-absorbed N were transferred to the roots, in the Walpeup LS plants. Plant N derived from the fertilizer and root or shoot dry matter were significantly correlated only when plants were N-deficient.In the Walpeup LS soil, N-fertilized wheat harvested 33 days after sowing (DAS) took up significantly less soil N compared with unfertilized plants, whereas significantly more soil N was taken up by N-fertilized sunflower compared with unfertilized plants harvested at 54 DAS. The fertilizerinduced response in uptake of soil N was directly related to the observed response in production of root biomass for both species. The different responses were related to the severity of the N deficiency and the limited effectiveness of foliar applications of urea in ameliorating the deficiency.

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Effects of nitrogen and phosphorus additions on nitrous oxide emission in a nitrogen-rich and two nitrogen-limited tropical forests

10.5194/bg-2015-552 ◽

2016 ◽

Author(s):

M. H. Zheng ◽

T. Zhang ◽

L. Liu ◽

W. X. Zhu ◽

W. Zhang ◽

...

Keyword(s):

Nitrous Oxide ◽

Tropical Forests ◽

N2o Emission ◽

N Deposition ◽

Soil N ◽

N Addition ◽

Old Growth ◽

Old Growth Forest ◽

P Addition ◽

Stimulation Of

Abstract. Nitrogen (N) deposition is generally considered to increase soil nitrous oxide (N2O) emission in N-rich forests. In many tropical forests, however, elevated N deposition has caused soil N enrichment and further phosphorus (P) deficiency, and the interaction of N and P to control soil N2O emission remains poorly understood, particularly in forests with different soil N status. In this study, we examined the effects of N and P additions on soil N2O emission in an N-rich old-growth forest and two N-limited younger forests (a mixed and a pine forest) in southern China, to test the following hypotheses: (1) soil N2O emission is the highest in old-growth forest due to the N-rich soil; (2) N addition increases N2O emission more in the old-growth forest than in the two younger forests; (3) P addition decreases N O emission more in the old-growth forest than in the two younger forests; and (4) P addition alleviates the stimulation of N2O emission by N addition. The following four treatments were established in each forest: Control, N addition (150 kg N ha–1 yr–1), P addition (150 kg P ha–1 yr–1), and NP addition (150 kg N ha–1 yr–1 plus 150 kg P ha–1 yr–1). From February 2007 to October 2009, monthly quantification of soil N2O emission was performed using static chamber and gas chromatography techniques. Mean N2O emission was shown to be significantly higher in the old-growth forest (13.86 ± 0.71 μg N2O-N m–2 h–1) than in the mixed (9.86 ± 0.38 μg N2O-N m–2 h–1) or pine (10.83 ± 0.52 μg N) forests, with no significant difference between the latter two. N addition significantly increased N2O emission in the old-growth forest but not in the two younger forests. However, both P- and NP-addition had no significant effect on N2O emission in all three forests, suggesting that P addition alleviated the stimulation of N2O emission by N addition in the old-growth forest. Although P fertilization may alleviate the stimulated effects of atmospheric N deposition on N O emission in N-rich forests, we suggest future investigations to definitively assess this management strategy and the importance of P in regulating N cycles from regional to global scales.

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Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066917 ◽

1971 ◽

Vol 29 ◽

pp. 570-571

Author(s):

E. A. Elfont ◽

R. B. Tobin ◽

D. G. Colton ◽

M. A. Mehlman

Keyword(s):

Chemical Composition ◽

Rat Liver ◽

Future Study ◽

Mode Of Action ◽

Liver Mitochondria ◽

Rat Liver Mitochondria ◽

Effective Inhibitor ◽

Biochemical Effects ◽

Glycerophosphate Dehydrogenase ◽

Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

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Gap junctions in the prothoracic glands of the tobacco hornworm, Manduca sexta

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100123933 ◽

1992 ◽

Vol 50 (1) ◽

pp. 706-707

Author(s):

Ji-da Dai ◽

M. Joseph Costello ◽

Lawrence I. Gilbert

Keyword(s):

Gap Junctions ◽

Small Molecules ◽

Manduca Sexta ◽

Freeze Fracture ◽

Cell Communication ◽

Cellular Level ◽

Thin Sections ◽

Prothoracic Glands ◽

Polyhydroxylated Steroids ◽

Stimulation Of

Insect molting and metamorphosis are elicited by a class of polyhydroxylated steroids, ecdysteroids, that originate in the prothoracic glands (PGs). Prothoracicotropic hormone stimulation of steroidogenesis by the PGs at the cellular level involves both calcium and cAMP. Cell-to-cell communication mediated by gap junctions may play a key role in regulating signal transduction by controlling the transmission of small molecules and ions between adjacent cells. This is the first report of gap junctions in the PGs, the evidence obtained by means of SEM, thin sections and freeze-fracture replicas.

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