Methyl bromide emissions to the atmosphere from temperate woodland ecosystems
Bibliographic record
Abstract
Abstract The environmental importance of methyl bromide (CH3Br) arises from its contribution to stratospheric ozone loss processes and, as a consequence, its emissions from anthropogenic sources are subject to the Montreal Protocol. A better understanding of the natural budget of CH3Br is required for assessing the benefit of anthropogenic emission reductions and for understanding any potential effects of environmental change on global CH3Br concentrations. Measurements of CH3Br flux in temperate woodland ecosystems, in particular, are very sparse, yet these cover a large fraction of terrestrial land surface. Results presented here from 18 months of field measurements of CH3Br fluxes in four static flux chambers in a woodland in Scotland and from enclosures of rotting wood and deciduous and coniferous leaf litter suggest net emissions from temperate woodlands. Net CH3Br fluxes in the woodland varied between the chambers, fluctuating between net uptake and net emissions (−73 to 279 ng m−2 h−1 across 161 individual measurements), and with no strong seasonality, but with time‐averaged net emission overall [27±57 (1 SD)] ng m−2 h−1]. This work demonstrates that scale‐up needs to be based on sufficient individual measurements to provide a reasonably constrained estimate of the long‐term mean. Mean (±1 SD) net CH3Br emissions from deciduous and coniferous leaf litter were 43 (±33) ng kg−1 (dry weight) h−1 and 80 (±37) ng kg−1 (dry weight) h−1, respectively, and ∼1–2 ng kg−1 (fresh weight) h−1 from rotting woody litter. Despite the intrinsic variability, data obtained here consistently point to the conclusion that the temperate forest soil/litter ecosystem is a net source of CH3Br to the atmosphere.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 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".