A thawing boreal peat landscape along the southern limit of permafrost presently is carbon neutral
Bibliographic record
Abstract
Along the southern limit of permafrost in northwestern Canada rising air temperatures have caused widespread land cover changes at unprecedented rates. A prominent change includes thermokarst wetland expansion at the expense of black spruce-dominated boreal forest stands due to the permafrost thaw-induced collapse of peat plateaus. We present a multi-year (2013 – 2017) net ecosystem carbon (C) balance (NECB, g C m-2year-1) at Scotty Creek near Fort Simpson, NT. The highly fragmented study site is dominated by permafrost-free wetlands and forested permafrost peat plateaus. Eddy covariance measurements of net ecosystem carbon dioxide (CO2) and methane (CH4) exchanges (2013 – 2017) are complemented by discharge (2014 – 2016) and water chemistry monitoring (2015 and 2016) at the outlets of three small headwater catchments (<0.5 km2) draining the eddy covariance footprint area. In addition to net ecosystem CO2and CH4exchanges, the NECB includes the export of dissolved C (DC) as the sum of inorganic and organic C (DIC and DOC), free CO2and CH4through runoff, and the estimated import of DOC through precipitation. We use absorbance spectroscopy for dissolved organic matter (DOM) characterization to distinguish different DOM sources among catchments and characteristic land cover types. Between 2013 and 2017, the NECB varied between a weak net C source (~16 ±5 g C m-2year-1) and sink (~-22 ±5 g C m-2year-1) in 2015 and 2013, respectively, with a mean value of -1 ±7 g C m-2year-1. The net C sink-source strength was largely controlled by variations in net CO2exchange, ranging between a weak net CO2 sink (~-29 ±3 g C m-2year-1) and source (~8 ±4 g C m-2year-1) in 2015 and 2013, respectively. In contrast, our study site was a persistent annual net CH4source (~8 ±1 g C m-2year-1). Compensated by the import of DOC through precipitation, DC exported from the three catchments was a negligible component of the NECB. There were no significant differences in DOC concentrations and absorbance indices among catchments, and thawed and frozen land cover types, overall illustrating high DOM aromaticity (SUVA254= 3.3 ± 0.6 L mg-1m-1) and high molecular weight (a254:a365 = 4.3 ± 0.3) characteristic for peatlands and peat-dominated landscapes outside the circumpolar permafrost region. We conclude that a rapidly thawing boreal peat landscape along the southern limit of permafrost presently appears to be C neutral.
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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) | 0.003 | 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".