Origins of hard carbonate nodules in arable Chernozems in the Central Russian Upland
Bibliographic record
Abstract
Abstract The genesis of hard carbonate nodules in the lowermost horizons (180–200 cm) of arable soils in the southern part of the forest‐steppe region of the Central Russian Upland was associated with a change in soil water regime. The conversion of forest to arable lands was studied in three agro‐chronosequences located on flat interfluves and consisted of undisturbed soils under deciduous forests and arable soils with different durations of agricultural use. Due to arable agricultural activity, the upper soil horizons become drier in the summer during the growing season, whereas the lowermost parts get wetter in the spring and autumn after harvests. As a result, two types of hard carbonate nodules, which differed in morphology, origin and age, formed in the arable soils. The first type of hard nodules had a dense cryptocrystalline fabric in thin sections and colloform morphology viewed under an electron microscope, consisting of calcite with Si, Al and Fe peaks in EDS spectra, and had a 14 C‐age from 16,410 ± 200 to 13,570 ± 150 years BP. Their formation occurred due to an ascending of “old” carbonate matter in colloidal suspensions through capillary pores from parent rocks in the periods of strong heating of the soil surface; these nodules had an evaporative origin. The second type of hard nodules consisted of crystalline pure calcite and had a 14 C‐age of < 4,500 years BP. They had a hydromorphic genesis and developed in periods of water stagnation in the deep horizons and can be considered to be markers of a seasonal hydromorphism of arable soils in the studied area. Highlights The conversion of forest to arable lands resulted in a change of soil water regime followed by the formation of two types of hard nodules The uplifting of calcite colloidal solutions/suspensions from parent material enriched newly formed hard nodules with “old” 14 C The seasonal stagnant water in the lowermost soil horizons caused hard nodule recrystallization and rejuvenation by “young” 14 C from organic acids and atmospheric CO 2 .
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 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 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".