Isotopic composition of tropospheric and soil N<sub>2</sub>O from successive depths of agricultural plots with contrasting crops and nitrogen amendments
Bibliographic record
Abstract
Agricultural soils are the dominant contributor to increases in atmospheric nitrous oxide (N 2 O). Few studies have investigated the natural N and O isotopic composition of soil N 2 O. We collected soil gas samples using horizontal sampling tubes installed at successive depths under five contrasting agricultural crops (e.g., unamended alfalfa, fertilized cereal), and tropospheric air samples. Mean δ 15 N and δ 18 O values of soil N 2 O ranged from −28.0 to +8.9‰, and from +29.0 to +53.6‰. The mean δ 15 N and δ 18 O values of tropospheric N 2 O were +4.6 ± 0.7‰ and +48.3 ± 0.2‰, respectively. In general, δ values were lowest at depth, they were negatively correlated to soil [N 2 O], and δ 15 N was positively correlated to δ 18 O for every treatment on all sampling dates. N 2 O from the different agricultural treatments had distinct δ 15 N and δ 18 O values that varied among sampling dates. Fertilized treatments had soil N 2 O with low δ values, but the unamended alfalfa yielded N 2 O with the lowest δ values. Diffusion was not the predominant process controlling N 2 O concentration profiles. Based on isotopic and concentration data, it appears that soil N 2 O was consumed, as it moved from deeper to shallower soil layers. To better assess the main process(es) controlling N 2 O within a soil profile, we propose a conceptual model that integrates data on net N 2 O production or consumption and isotopic data. The direct local impact of agricultural N 2 O on the isotopic composition of tropospheric N 2 O was recorded by a shift toward lower δ values of locally measured tropospheric N 2 O on a day with very high soil N 2 O emissions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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 teacher head, 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".