Comment on egusphere-2025-3849
Bibliographic record
Abstract
Abstract. Terrestrially-derived plant waxes and their compound-specific stable carbon (δ13C) and hydrogen (δ2H) isotope ratios are valuable tools for inferring past changes in vegetation and hydrology in sedimentary archives. Such inferences require knowing the ecological (i.e. plant growth form) and environmental (i.e. temperature, precipitation, relative humidity, elevation) mechanisms that govern the production of different plant wax carbon chain-lengths and the fractionation of stable isotopes. These mechanisms, however, are uncertain in the Arctic, limiting our ability to infer past vegetation and hydrology changes. To address this, we produced terrestrial plant n-alkanoic acid and n-alkane abundance and δ13C and δ2H data from a latitudinal environmental gradient along the Eastern Canadian Arctic (105 individuals), which we compiled with published data across the Arctic (additional 281 individuals). We compared this dataset with environmental parameters to assess the mechanisms that govern plant-wax production and isotope fractionation. We found that total plant wax concentrations and Average ChainLength (ACL) were statistically different between vascular (trees, shrubs, forbs, ferns, graminoids) and non-vascular plants (mosses, liverworts) and lichens, whereas δ13C values and δ2H apparent fractionation relative to growing season precipitation δ2H often did not differ significantly between plant growth forms. Correlations between plant wax indices and mean of the months above freezing (MAF) environmental parameters were generally weak (r ≤ 0.4), and/or not significant (p > 0.05). These results suggest that a fundamental assumption to paleoclimate research holds in the Arctic: for individual plant taxa and plant communities, the abundance, ACL, and δ13C/δ2H isotopic fractionation of both n-alkanoic acids and n-alkanes is independent of temperature, precipitation, humidity, and elevation. Instead, changes in sedimentary plant wax distributions reflect changes in plant taxa present through time, and changes in plant wax δ2H reflect changes in source water δ2H. Therefore, plant waxes can be used to infer past changes in climate and ecology.
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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 | 0.010 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.004 | 0.003 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.012 | 0.006 |
| Insufficient payload (model declined to judge) | 0.609 | 0.454 |
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".