A laboratory study of soil conditions affecting emissions of nitrous oxide from packed cores subjected to freezing and thawing
Bibliographic record
Abstract
Tenuta, M. and Sparling, B. 2011. A laboratory study of soil conditions affecting emissions of nitrous oxide from packed cores subjected to freezing and thawing. Can. J. Soil Sci. 91: 223-233. A series of laboratory experiments using a packed core soil assay was carried out to test several soil conditions affecting the emission of N2O (nitrous oxide) during thawing of soil. The assay consisted of a sandy loam soil packed to 1.1 Mg m-3, moistened to 80% water-filled pore space, and temperature treated to 4 or -20°C for 2.5 d; the emissions from thawing soil were then determined as the differences in N2O release rates of the temperature-treated soils when placed at 15°C. Nitrate addition to surface soil (0-10 cm) enhanced thaw emission. Thaw emissions, averaged for deeper collected soil (10-30 and 30-60 cm), was 0.3% with NO3- treatment and 1.2% without NO3- treatment of that for surface soil treated similarly. Higher thaw emission for surface soil was related to greater organic matter and microbial biomass C contents and denitrifying enzyme activity than deeper collections of soil. Increasing the bulk density of soil from 1.1, 1.2, and 1.25 Mg m-3 decreased thaw emission. A second freeze-thaw cycle of the highest compaction treatment resulted in an emission of 2.3% of the first freeze-thaw cycle. Acetylene increased thaw emission of N2O and more so for NO3- untreated than treated soil. Using the acetylene inhibition method, the N2O:N2 ratio of gas produced was higher for frozen (0.17) than cold (0.07) treated soil, respectively, without the addition of NO3-. The addition of NO3- increased the N2O:N2 ratio of gas produced with the ratio being 2.45 and 0.53 for frozen and cold-treated soil. The results are consistent with biological denitrification being a source of N2O with conditions promoting N2O production rather than consumption enhancing thaw emissions.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".