Winter and spring thaw nitrous oxide emissions linked to nitrous oxide production in the soil profile
Bibliographic record
Abstract
The soil processes leading to N2O emissions during winter freezing and spring thawing are not well understood. The principal objectives of this thesis were (i) to determine the crucial factor in triggering a burst in N2O emissions from soils under conventional and best management practices; (ii) to investigate the processes of N2O production in the frozen soil profile; (iii) to elucidate the mechanism of N2O production in the frozen soil profile. The increase of soil water content in the frozen soil layer was the main characteristic of the frozen soils during winter. The crucial factor in triggering N2O fluxes was found to be the high water content in the thawed layer originated from the frozen layer when two agricultural practices were compared in eastern Canada. Total annual and spring thaw N2O emissions measured by a micrometeorological technique from conventional practice soil were higher than that from best management practice soil. Snow depth influenced by agricultural management practices, which affected the depth of soil freezing, was a key factor in influencing N2O fluxes. N2O concentrations at different soil depths were associated with two wet soil layers, i.e., analogous capillary fringes, at the top and bottom of frozen layer. The high water content in the analogous capillary fringes triggered a burst in N2O and CO2 production by enhancing microorganism activity. The correlation between N2O and CO2 concentrations confirmed that biological processes were responsible for N2O production. The occurrence of N2O fluxes measured by chamber method was similar to that by a micrometeorological technique during the periods of soil thawing. 15N2O measurements confirmed the source of N2O fluxes was the 'new' N2O produced in thawed layers. The high 15N enrichment of fluxed N2O confirmed that denitrification was the mechanism responsible for the burst N2O fluxes. A new method for simulating soil freezing and thawing cycles was developed to study nitrous oxide fluxes in the laboratory. The N2O fluxes during these cycles were affected by the degree of soil freezing and water content in soil columns.
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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 | 0.000 |
| 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 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".