Investigating the mechanisms of soil organic matter stabilization in a clayey soil of the St-Lawrence lowlands, Québec, Canada
Bibliographic record
Abstract
Soil organic matter (SOM) is a key element in soil quality and productivity, and represents the biggest C pool of the terrestrial biosphere. Understanding soil organic carbon (SOC) retention mechanisms is necessary to address their role as potential C sink, and ensure their quality and productivity for future generations. The objective of this research was to examine, under controlled conditions, the stabilization of newly added C and N coming from crop residues in topsoil and subsoil horizons of a heavy clay soil from the St-Lawrence Lowlands. Topsoil (0-20 cm depth, 31.3 g SOC kg-1 soil) and subsoil (30-70 cm depth, 4.5 g SOC kg-1 soil) were incubated (25ºC, -38 kPa, C/N = 10) for 51 d with increasing amounts (from 0 to 40 g C kg-1 soil) of 13C-15N-labelled corn residues. Carbon mineralization was greater in topsoil than subsoil, but comparable amounts of residue-C were retained in both soils, on a whole soil basis. This suggests that the extra C lost from the topsoil came from the mineralization of autochthonous SOC. Preferential retention of residue-derived C and N occurred in large macroaggregates (>1000 µm) in the subsoil, and in small macroaggregates (250-1000 µm) in the topsoil. Macroaggregate enrichment in residue-derived C and N occurred simultaneously through small-scale adsorption (< 50 µm) and large-scale occlusion (>250 µm). Sequential density fractionation of soil coupled with X-ray diffraction mineralogical analysis revealed a greater proportion of autochthonous and residue-derived C and N associated with soil minerals in subsoil than topsoil. Subsoil organo-mineral complexes were enriched in residue-derived N, indicating preferential adsorption of nitrogenous compounds onto unsaturated mineral surfaces in the early stages of organo-mineral complexes formation. In conclusion, topsoil and subsoil horizons of a heavy clay soil from Eastern Canada can accumulate substantial amounts of residue-derived C and N, with greater potential for C and N sequestration in stable organo-mineral complexes in subsoil than topsoil.
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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 | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".