Relationships between carbon age and CO <sub>2</sub> efflux in agricultural and drainage ditch soils using the thermonuclear bomb pulse
Bibliographic record
Abstract
Abstract Agricultural soils contribute significantly to global CO 2 emissions. Soils can be both a CO 2 sink and source depending on vegetation cover and the physical‐chemical characteristics of the soil environment. This study uses a new 14 C dating approach to elucidate soil physical and geochemical properties that drive the production and transport of CO 2 in cultivated and noncultivated drainage ditch soil environments. As expected, CO 2 production and fluxes decrease with soil depth. Relating depth‐specific subsurface radiocarbon of CO 2 ( 14 CO 2 ) to the atmospheric scenario generated from the testing of thermonuclear bombs in the 1950s and 1960s provides a means to date the labile organic C pools responsible for soil respiration that are otherwise generalized as having a modern age (≤1950 AD). Depth‐specific 14 CO 2 measurements showed that CO 2 in shallow soils (≤22.5‐cm depth) have a younger age than CO 2 in deeper soils (>22.5‐cm depth). The 14 CO 2 of surface emissions were comparable to those of shallow soils (≤22.5‐cm depth), showing that respiration in the deeper soils (>22.5‐cm depth) do not contribute significantly to surface emissions, and the higher CO 2 concentrations at depth in soil result from processes limiting CO 2 transport to surface. Coupling the 14 C data with CO 2 flux profiles confirms that CO 2 effluxes are derived from modern soil organic C (<10 yr since sequestered) from the shallowest soil depths in all soil environments studied, but changes in physical soil processes governing gas transport at depth could release these deeper CO 2 stores.
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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 | 0.002 | 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 | 0.002 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| 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 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".