Nitrogen enrichment and the emission of nitrous oxide from streams
Bibliographic record
Abstract
[1] Nitrous oxide (N2O) is a potent greenhouse gas produced during nitrogen cycling. Global nitrogen enrichment has resulted in increased atmospheric N2O concentrations due in large part to increased soil emissions. There is also a potentially important flux from streams, rivers and estuaries; although measurements of these emissions are sparse, and role of aquatic ecosystems in global N2O budgets remains highly uncertain. Using the longest-term measurements of N2O fluxes from streams to date, we found annual fluxes from 14 sites in five streams of south-central Ontario, Canada varied widely–from net uptake of 3.2 ± 0.2 (standard deviation)μmol N2O m−2 d−1 to net release of 776 ± 61 μmol N2O m−2 d−1. N2O consumption was associated with very low nitrate concentrations (<2.7 μM). Mean annual (log-transformed) N2O emissions from our study streams (across sites and years) were positively related to nitrate concentrations (r2= 0.59).This nitrate-N2O relationship can be generalized across all 20 streams (in Canada, Japan, Mexico, and the midwestern United States) for which published data now exist and could provide a new basis for the IPCC to calculate agricultural emissions from streams. In addition to predicting annual emissions, we present the first measurements of N2O concentrations under ice in streams. Nitrate was a strong predictor of N2O % saturation during periods of ice cover (r2 = 0.89), when gas exchange is negligible. Given the small surface area of streams within a catchment and the fact our measured areal fluxes are comparable to reported fluxes from agricultural soils, this suggests streams are a small regional N2O source.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".