Concept · environmental-science
Nitrogen cycle
6 studies
The nitrogen cycle is how N is deposited, taken up, transformed or lost — including wastewater anammox, deposition and biological fixation.
Nitrogen is both a pollutant and a nutrient; undergraduates need both faces.
Studies
6
Findings
5
7 supporting · 0 challenging · 0 qualifying citations
Open tensions
1
Currently
What we know
- This library holds 6 empirical papers on nitrogen cycle with measured outcomes rather than reviews.
- Twelve-year outdoor oxidation of pine around iron nails produced condensed aromatic nitrogen like ‘black N’, implying non-fire ConAN fluxes (≈3–63 Tg yr−1) comparable to pyrogenic estimates.
- Vanadium nitrogenase was active in most valid moss and lichen samples across three continents, averaging about 40% of moss N2 fixation.
- Soil–air nitrous acid exchange is set by an equilibrium gas-phase concentration over soil ([HONO]*) versus ambient HONO, so soils can emit or take up HONO as they dry.
- At Loobos, TER fell while GPP rose over 26 years; acid soils (pH 2.9) and N deposition appear to throttle decomposition.
Largest unresolved question
A reactor microbiome or a canopy 15N tracer is not catchment-scale load.
Common misconceptions
Intermittent aeration always kills every unwanted microbe.
NOB suppression and TN removal trade off with switching frequency and scale.
Related
Claim ledger
What the evidence shows
Drawn from 6 studies in this library. Mix labels say which citation roles are present; they are not a strength score. Supports means evidence for a finding; Challenges means evidence against a stated position; Qualifies marks scope.
This library holds 6 empirical papers on nitrogen cycle with measured outcomes rather than reviews.
- ‘Black’ nitrogen can form without fire
- Vanadium nitrogenase fuels forest moss N fixation
- Soil HONO flux depends on an equilibrium concentration
Study Role Design N Population Outcome ‘Black’ nitrogen can form without fire Supports OtherSpectroscopic characterization of 12-year outdoor iron-nail pine oxidation plus global ConAN budget Case study of pine deck oxidation; flux estimates are back-of-envelope budgets, not a sample N Condensed aromatic nitrogen formed in outdoor-oxidized pine (Norfolk, VA) and global litter fluxes Nonpyrogenic vs pyrogenic ConAN flux estimates to soils Vanadium nitrogenase fuels forest moss N fixation Supports Cross-sectionalLISARA assays of moss and lichen V-nitrogenase across three continents N=109 · 109 sampling plots (>40 sites, 9 locations); multiple cryptogam samples per plot Mosses and lichens in extratropical forests of North America, South America, and East Asia Share of biological N2 fixation attributable to vanadium nitrogenase Soil HONO flux depends on an equilibrium concentration Supports Animal / in-vitroDynamic-chamber experiments on drying soil with switched inlet HONO concentrations Inlet HONO switched among 0, 5, and 15 ppb across soil water contents Laboratory soil–atmosphere HONO exchange chambers Soil–air HONO flux is set by equilibrium [HONO]* versus ambient HONO, so soils can emit or take up HONO as they dry Twelve-year outdoor oxidation of pine around iron nails produced condensed aromatic nitrogen like ‘black N’, implying non-fire ConAN fluxes (≈3–63 Tg yr−1) comparable to pyrogenic estimates.
Vanadium nitrogenase was active in most valid moss and lichen samples across three continents, averaging about 40% of moss N2 fixation.
Soil–air nitrous acid exchange is set by an equilibrium gas-phase concentration over soil ([HONO]*) versus ambient HONO, so soils can emit or take up HONO as they dry.
At Loobos, TER fell while GPP rose over 26 years; acid soils (pH 2.9) and N deposition appear to throttle decomposition.
Debates
Tensions and limits
Some items are genuine disagreements on the same question. Others mark different assays, populations, or outcomes.
A reactor microbiome or a canopy 15N tracer is not catchment-scale load.
A reactor microbiome or a canopy 15N tracer is not catchment-scale load.
Study Role Design N Population Outcome ‘Black’ nitrogen can form without fire Supports OtherSpectroscopic characterization of 12-year outdoor iron-nail pine oxidation plus global ConAN budget Case study of pine deck oxidation; flux estimates are back-of-envelope budgets, not a sample N Condensed aromatic nitrogen formed in outdoor-oxidized pine (Norfolk, VA) and global litter fluxes Nonpyrogenic vs pyrogenic ConAN flux estimates to soils Vanadium nitrogenase fuels forest moss N fixation Supports Cross-sectionalLISARA assays of moss and lichen V-nitrogenase across three continents N=109 · 109 sampling plots (>40 sites, 9 locations); multiple cryptogam samples per plot Mosses and lichens in extratropical forests of North America, South America, and East Asia Share of biological N2 fixation attributable to vanadium nitrogenase
PaperFren reads this as a limit on how far one study travels — different assays, populations, or outcomes — not a forced fight between papers.
Timeline
How understanding moved
Study years are when the paper was published. Evidence edits are dated changes to this page's claims. Explanations are when PaperFren added a Discovery — not a claim that the science happened that day.
2026
- ‘Black’ nitrogen can form without fire
- Nitrogen deposition is slowing forest respiration
- Vanadium nitrogenase fuels forest moss N fixation
Concept page published
Nitrogen cycle
Change log
What changed
Dated edits to this page's evidence: studies added or removed from a claim, claims added or withdrawn, and new explanations tagged here. Coverage edits are distinct from reviewed research changes and corrections. Dates record PaperFren updates; study publication dates appear in the timeline.
- Coverage updated · Concept page published
Papers
6 studies in this library bear on Nitrogen cycle, ordered by citations.
- Soil HONO flux depends on an equilibrium concentration
Soil–air nitrous acid exchange is set by an equilibrium gas-phase concentration over soil ([HONO]*) versus ambient HONO, so soils can emit or take up HONO as they dry.
- Intermittent aeration and anammox nitrogen
Switching oxygen on and off kept anammox working while wiping out nitrite-oxidizing bacteria.
- Vanadium nitrogenase fuels forest moss N fixation
Vanadium nitrogenase was active in most valid moss and lichen samples across three continents, averaging about 40% of moss N2 fixation.
- NH4NO3 N-addition overstates steppe microbe effects
In Inner Mongolian steppe, acidic NH4NO3 and (NH4)2SO4 shifted soil bacteria and carbon-gene profiles more than urea or NH4HCO3, so NH4NO3-only experiments can overestimate real N-deposition effects.
- ‘Black’ nitrogen can form without fire
Twelve-year outdoor oxidation of pine around iron nails produced condensed aromatic nitrogen like ‘black N’, implying non-fire ConAN fluxes (≈3–63 Tg yr−1) comparable to pyrogenic estimates.
- Nitrogen deposition is slowing forest respiration
At Loobos, TER fell while GPP rose over 26 years; acid soils (pH 2.9) and N deposition appear to throttle decomposition.
Compare studies
Select 2–10 studies. Design and N are labels, not a ranking.
Nothing selected yet.
Questions
What is still open
A reactor microbiome or a canopy 15N tracer is not catchment-scale load.
Ask PaperFren about Nitrogen cycle
Study this conceptflashcards and short-answer questions
What does nitrogen cycle mean in this library?
The nitrogen cycle is how N is deposited, taken up, transformed or lost — including wastewater anammox, deposition and biological fixation.
Name one empirical finding from the nitrogen cycle papers.
Twelve-year outdoor oxidation of pine around iron nails produced condensed aromatic nitrogen like ‘black N’, implying non-fire ConAN fluxes (≈3–63 Tg yr−1) comparable to pyrogenic estimates.
What is a limit of nitrogen cycle evidence here?
A reactor microbiome or a canopy 15N tracer is not catchment-scale load.