Intraseasonal Soil Macroaggregate Dynamics in Two Contrasting Field Soils Using Labeled Tracer Spheres
Bibliographic record
Abstract
Several studies have hypothesized that increased turnover of soil aggregates promotes soil organic matter losses under cultivation; while others suggest that organic matter protection requires occlusion into aggregates. However, few direct observations of aggregate dynamics are reported in the literature. A 2‐yr field study was performed to observe active organic C dynamics and soil macroaggregate dynamics in two contrasting soils. Dysprosium‐labelled tracer spheres were applied to field plots to observe soil macroaggregate dynamics, while CO 2 ‐evolution during 10‐d laboratory incubations was used to measure active C dynamics. Results of biochemical analyses showed higher active C turnover in the low C soil, suggesting a lower proportion of incoming organic matter was protected when compared with the high C soil. No net aggregation or degradation was determined over the long‐term, suggesting the soil was at steady‐state. However, aggregation followed a cyclical pattern reset by the over‐winter period and tillage. Tracer incorporation into large macroaggregates was observed within 9 d after tillage, reaching a maximum of 40 to 60% tracer incorporation into >1‐mm aggregates after 72 d. A rapid approach to equilibrium within the study period reflected rapid dynamics of macroaggregates in both soils studied. Slower macroaggregate dynamics in the high C soil were attributed to sustained aggregate stability and resiliency at the end of the growing season. Based on observations of macroaggregate dynamics in soils with contrasting active organic C dynamics, we suggest that rapid macroaggregate turnover not only results in the exposure of labile organic matter but also provides a mechanism for the occlusion and physical protection of particulate organic matter.
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How this classification was reachedexpand
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 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 teacher head, 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".