Methane Fluxes from Living and Dead Trees in a Temperate Forest
Bibliographic record
Abstract
Trees have been identified as an important source of methane in forest ecosystems, but little research exists on fluxes beyond their stems, such as those from foliage, branches, wounds, and coarse woody debris. Recent instrumentation advances allow rapid and accurate measurements of relatively low methane flux rates in-situ; this thesis takes advantage of such technology to explore methane fluxes from these tree components in northern hardwood forests of central Ontario, Canada. Foliage was found to represent a substantial component of forest methane budgets, acting as a sink in upland forests and a source in lowland forests (averages = -0.54, 6.06 nmol m-2 s-1; n = 27, 12, respectively). Uptake is hypothesized to occur through methanotrophs within foliage, and emissions from channelling of methane that originates in soil. In an upland site tree branches, wounds, and stems emitted methane (averages = 0.61, 10.58, 0.59 nmol m-2 s-1; n = 18, 83, 79, respectively), and at the stand scale represented 83%, 8%, and 9% of emissions from trees respectively. Emissions are hypothesized to occur through anoxic decomposition within the tree, which often occurs due to wounding. Coarse woody debris was found to act as a methane source in early decay classes and a sink in later decay classes (average flux rates ranged from 0.78 to -1.58 nmol m-2 s-1; n = 94). Immediately after harvest there was a large pulse of emissions from the cut surfaces of trees (>4000 nmol m-2 s-1 for Acer saccharum boles), but on average coarse woody debris was a methane sink in both managed and unmanaged stands. These results represent some of the first and most comprehensive in-situ methane flux measurements from tree branches, wounds, foliage, and coarse woody debris, and help to improve estimates of forest methane budgets. Inclusion of wounds and branches into calculations of tree methane fluxes will increase net emissions, but inclusion of upland foliage and dead wood as methane sinks can offset them. Strengthening forest methane sinks and reducing sources is an attractive policy option for “climate-smart” forestry, and this research can be built upon to support future efforts in this field.
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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 | 0.001 |
| 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) | 0.001 | 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".