On the fate of anthropogenic nitrogen

Schlesinger, William H.

doi:10.1073/pnas.0810193105

Cited by 826 publications

(609 citation statements)

References 95 publications

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“…For instance, given modern rates of terrestrial C accumulation (Ϸ2 Pg C/yr) (27), a C/N ratio that partitions this C into soil (15/1) and plant materials (200/1) equally (28), and assuming that all of the additional C results from new N inputs, we estimate that Ϸ18 Tg N/yr is accumulating on land. This value drops to Ϸ10 Tg N/yr if all of the C is assumed to be stored in plant biomass, consistent with other estimates (e.g., 9 Tg N/yr) (29). Even integrated over 100 years, however, such rates of N accumulation would only have altered total terrestrial N by Ͻ0.1% (9).…”

supporting

confidence: 76%

Imprint of denitrifying bacteria on the global terrestrial biosphere

Houlton

Bai

2009

Proc. Natl. Acad. Sci. U.S.A.

188

234

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Loss of nitrogen (N) from land limits the uptake and storage of atmospheric CO2 by the biosphere, influencing Earth's climate system and myriads of the global ecological functions and services on which humans rely. Nitrogen can be lost in both dissolved and gaseous phases; however, the partitioning of these vectors remains controversial. Particularly uncertain is whether the bacterial conversion of plant available N to gaseous forms (denitrification) plays a major role in structuring global N supplies in the nonagrarian centers of Earth. Here, we use the isotope composition of N ( 15 N/ 14 N) to constrain the transfer of this nutrient from the land to the water and atmosphere. We report that the integrated 15 N/ 14 N of the natural terrestrial biosphere is elevated with respect to that of atmospheric N inputs. This cannot be explained by preferential loss of 14 N to waterways; rather, it reflects a history of low 15 N/ 14 N gaseous N emissions to the atmosphere owing to denitrifying bacteria in the soil. Parameterizing a simple model with global N isotope data, we estimate that soil denitrification (including N2) accounts for Ϸ1/3 of the total N lost from the unmanaged terrestrial biosphere. Applying this fraction to estimates of N inputs, N2O and NOx fluxes, we calculate that Ϸ28 Tg of N are lost annually via N2 efflux from the natural soil. These results place isotopic constraints on the widely held belief that denitrifying bacteria account for a significant fraction of the missing N in the global N cycle.denitrification ͉ isotope ͉ nitrogen ͉ ecosystem ͉ microbe

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supporting

confidence: 76%

Imprint of denitrifying bacteria on the global terrestrial biosphere

Houlton

Bai

2009

Proc. Natl. Acad. Sci. U.S.A.

188

234

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“…These high denitrification fractions are much greater than implied by traditional soil-based approaches (Table 1). At both local and global scales, denitrification losses are often estimated by nitrous oxide (N 2 O)/(N 2 + N 2 O) ratios and the N 2 O emission rates, with an average N 2 O fraction of ∼0.5 observed for soils under natural vegetation (24). Applying this fraction to data collected across our study sites yields denitrification fluxes that are substantially lower than our isotope-based approach (i.e., 0.2-9.4 kg of N ha −1 ·y −1 ; Table 1).…”

Section: Resultsmentioning

confidence: 99%

Microbial denitrification dominates nitrate losses from forest ecosystems

Fang

Koba

Makabe

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

192

125

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Denitrification removes fixed nitrogen (N) from the biosphere, thereby restricting the availability of this key limiting nutrient for terrestrial plant productivity. This microbially driven process has been exceedingly difficult to measure, however, given the large background of nitrogen gas (N 2 ) in the atmosphere and vexing scaling issues associated with heterogeneous soil systems. Here, we use natural abundance of N and oxygen isotopes in nitrate (NO 3 − ) to examine dentrification rates across six forest sites in southern China and central Japan, which span temperate to tropical climates, as well as various stand ages and N deposition regimes. Our multiple stable isotope approach across soil to watershed scales shows that traditional techniques underestimate terrestrial denitrification fluxes by up to 98%, with annual losses of 5.6-30.1 kg of N per hectare via this gaseous pathway. These N export fluxes are up to sixfold higher than NO 3 − leaching, pointing to widespread dominance of denitrification in removing NO 3 − from forest ecosystems across a range of conditions. Further, we report that the loss of NO 3 − to denitrification decreased in comparison to leaching pathways in sites with the highest rates of anthropogenic N deposition.denitrification | nitrate isotopes | nitrogen cycling | forested watersheds

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“…The intermediate N 2 O is a powerful greenhouse gas that contributes to global warming (Schlesinger 2009) and causes stratospheric ozone destruction (Ravishankara et al 2009). Soil is a predominant contributor to the atmospheric N 2 O, mostly released by the microbial processes of nitrification and denitrification (Thomson et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Compaction stimulates denitrification in an urban park soil using 15N tracing technique

Deng

Rensing

et al. 2013

Environ Sci Pollut Res

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Soils in urban areas are subjected to compaction with accelerating urbanization. The effects of anthropogenic compaction on urban soil denitrification are largely unknown. We conducted a study on an urban park soil to investigate how compaction impacts denitrification. By using 15 N labeling method and acetylene inhibition technique, we performed three coherent incubation experiments to quantify denitrification in compacted soil under both aerobic and anaerobic conditions. Uncompacted soil was set as the control treatment. When monitoring soil incubation without extra substrate, higher nitrous oxide (N 2 O) flux and denitrification enzyme activity were observed in the compacted soil than in the uncompacted soil. In aerobic incubation with the addition of K 15 NO 3 , N 2 O production in the compacted soil reached 10.11 ng N h −1 g −1 as compared to 0.02 ng N h −1 g −1 in the uncompacted soil. Denitrification contributed 96 % of the emitted N 2 O in the compacted soil and 36 % of the emitted N 2 O in the uncompacted soil; total denitrification rate was higher in the compacted soil (up to 79.35 ng N h −1 g −1 ) than in the uncompacted soil (0.11 ng N h −1 g −1 ). Under anaerobic incubation with the addition of K 15 NO 3 , no statistical difference in total N losses and 15 N-(N 2 O+N 2 ) flux between the uncompacted soil and the compacted soil was detected. Compaction promoted soil denitrification and may impact urban N biogeochemical cycling.

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On the fate of anthropogenic nitrogen

Cited by 826 publications

References 95 publications

Imprint of denitrifying bacteria on the global terrestrial biosphere

Imprint of denitrifying bacteria on the global terrestrial biosphere

Microbial denitrification dominates nitrate losses from forest ecosystems

Compaction stimulates denitrification in an urban park soil using 15N tracing technique

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