A comparative biogeochemical study of extant, and fossil gymnosperm wood from Axel Heiberg Island, Canada
Bibliographic record
Abstract
An analysis of the main lignin, polysaccharide and hemicellulose components of modern and fossil Metasequoia and Larix woods was conducted through the application of Py-GC/MS, tetramethylammonium .hydroxide (TMAH) thermochemolysis, 13C NMR, Py-MS and TG-DSC in order to discern the main similarities and differences between modern and fossil woods, an~ to discover the main reasons for their preservation, the main processes involved in the initial stages of fossilisation, and the palaeoenvironment associated with their depositional sites in Axel Heiberg Island, Canada. Four modern Larix species woods were compared to each other, and then to the only extant Metasequoia species wood to discover the exact similarities and .any differences between them. This was done because the exact species of fossil Larix and Metasequoia are unknown. No differences were found and it is assumed that as no differences exist between modern species, no differences exist between fossil species. The Py-GC/MS total ion chromatogram of the modern woods showed carbohydrate and guaiacyl lignin-derived compounds indicative of gymnosperm wood. A decrease in carbohydrates relative to the modern woods was discovered in the fossil woods and a relative increase in methoxyphenols and tannins. Similarities to the effects of degradation through fungal invasion were noted in the analysis of the fossil woods with a relatively decreased polysaccharide compared to their modern counterpart, with the possibility of fungal degradation during early diagenesis. The TMAH thermochemolysis total ion chromatograms showed an increase of threo/erythro 1-(3,4-dimethoxyphenyl)-1,2,3-trimethoxypropane (G14/G15 - long chain) over 3,4-dimethoxybenzaldehyde/3,4-dimethoxybenzoic acid methyl ester (G4/G6 - short chain) guaiacyl structures from modern to fossil. Similarities to the effects of degradation through fungal invasion were again noted in the analysis of the fossil woods where long chain guaiacyl structures dominate over the short chain guaiacyl structures, reinforcing the possibility of fungal input during early diagenesis. 13C NMR analysis highlighted an increase in side chain degradation from the guaiacyl units thus forming condensed guaiacyl structures, and a decrease in carbohydrate content from the fossil woods relative to the modern woods. Possible tannin input was detected contributing to wood preservation. TG-DSC and Py-MS analysis showed carbohydrate content decreased from modern relative to fossil sample and condensed lignin structures increased. Polysaccharides were shown to be more in abundance within the Metasequoia than Larix sample indicating less degradation had occurred. The fossil woods although degraded, had maintained their basic carbohydrate/lignin structure and were comparable to modern woods degraded through fungal invasion. In addition the nature of the degradation was found to resemble that caused by white rot fungi. The general state of degradation was less severe in the Metasequoia than the Larix. The Metasequoia wood had probably been deposited after that of the Larix and in different environmental conditions, being slightly anoxic, with less fungal input. The presence of tannins together with the subsequent extreme cold of Axel Heiberg Island probably contributed to the woods preservation over time.
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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 | 0.003 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".