Carbon and nitrogen molecular composition of soil organic matter fractions resistant to oxidation
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
The methods used to isolate and characterise pyrogenic organic carbon (PyC) from soils vary widely, and there is little agreement in the literature as to which method truly isolates the most chemically recalcitrant (inferred from oxidative resistance) and persistent (inferred from radiocarbon abundance) fraction of soil organic matter. In addition, the roles of fire, fuel type and soil morphology in the preservation of PyC are not yet defined. In an attempt to elucidate the importance of oxidative recalcitrance, fuel type and soil morphology to the persistence of soil organic matter, we examined two strongly contrasting soils using a variety of PyC isolation techniques coupled with quantifications of the molecular structure and mean residence time of the isolated organic materials. Surface and subsurface soil samples were examined from a Red Chromosol soil and a Black Vertosol soil. The d13C values suggest that PyC in the Red Chromosol was sourced from eucalyptus, whereas PyC in the Black Vertosol was formed from grass. Soils were sieved at 53 µm, treated with hydrofluoric acid to remove organics associated with mineral surfaces, then subjected to three common ‘PyC isolation’ treatments: chromic acid, photo-oxidation and chromic acid followed by photo-oxidation. Molecular structure of the organic residues remaining after each treatment was quantified by solid-state 13C cross polarisation magic angle spinning nuclear magnetic resonance and near edge X-ray absorption fine structure spectroscopy, and the mean residence time of the organic residues was estimated based on radiocarbon abundance. In all cases, treatment with chromic acid followed by photo-oxidation isolated the smallest proportion of organic matter (5–10% of <53 µm C) which also had the longest mean residence time (estimated 600–3460 years). Additionally, molecular structure measurements indicated that this fraction was not composed solely of aromatic compounds, suggesting a non-homogenous source for the most oxidative-resistant fraction of soil organic matter.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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 it