Recovery and dynamics of decomposing plant residue in soil: an evaluation of three fractionation methods
Bibliographic record
Abstract
Summary Our goals in this study were to track the incorporation of plant residue into soil organic matter ( SOM ) and test the effectiveness of different fractionation methods to evaluate this transformation. We incubated soil amended with 13 C ‐labelled barley ( H ordeum vulgare L. ) residue and used three fractionation methods based on size (> 250, 53–250, 5–53 and < 5 µm) and density (< 1.7 g cm −3 , i.e. light fraction (LF) ) and determined its quantity and the rate of C loss or gain or both in these fractions as decomposition progressed. One method was based on size only, another involved density separation followed by size fractionation and a third separated organic matter fractions by size first and then by density. There were significant quantitative differences between the methods for the amount of residue in the fractions, but there was no effect of fractionation method on the rate of change in the residue that comprised the fractions. The density method did not appear to identify all of the most recently added (i.e. least decomposed) residue in the LF or that there was a redistribution of SOM among the fractions. The amount of residue C and the C : N ratio of the residue in the two smallest fractions increased early during the incubation (0–2 months), but subsequently decreased towards the end. The initially small C:N ratio in the clay fraction probably reflects the accumulation of microbial by‐products from the rapid decomposition of water‐soluble compounds. The subsequent increase and decrease in both residue C and C:N ratio reflects the balance of the accumulation of sorbed water‐soluble compounds and dense plant residue fragments and their mineralization over time. We conclude that clay is a sink for residue C (i.e. microbial metabolites) early during decomposition, and that there is a transfer among fractions and mineralization of residue C as decomposition proceeds. These findings indicate that the clay fraction contains a dynamic pool of C that can cycle within short time‐scales.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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".