Controls on the Extractability of Soil Organic Matter in Water over the 20 to 80°C Temperature Range
Bibliographic record
Abstract
Cold (room temperature, 20°C) and hot water (70–80°C) methods have been used to extract soil organic matter (SOM), but the controls on organic matter solubility within the 20 to 80°C range are not well understood. We measured dissolved organic matter (DOM) as well as cations (Ca, Mg, K, Na, NH 4 , Mn, Al), inorganic anions (Cl, NO 3 , PO 4 , SO 4 , HCO 3 ) and Si in water extracts of three soils (pasture soil, pasture soil that had been chemically fallowed for 6 yr, and a forest soil) at temperatures ranging from 20 to 80°C (16‐h incubation in temperature‐controlled water baths). Dissolved organic C (DOC) and N increased exponentially in response to temperature increase. Cation solubility increased substantially with temperature (total soluble cations averaged 2.6 mmol c kg −1 of soil at 20°C, increasing to 8.6 mmol c kg −1 at 80°C). Effects of temperature on solubility of inorganic anions were relatively small (total soluble anions averaged 0.7 mmol c kg −1 at 20°C vs. 1.1 mmol c kg −1 at 80°C). The cation surplus (cations minus inorganic anions), which became greater as temperature increased, was balanced by the negative charge carried by the DOM (estimated charge density of DOM was 600–1900 cmol c kg −1 of C). Temperature‐induced increases in DOM and cations were related to NH 4 + and OH – production by N mineralization at low (20–50°C) temperatures. The mineralized NH 4 + displaced indigenous cations (Ca, Mg, K, Na) while the OH – caused desorption of organic matter to balance the cations. At higher temperature (>50°C), increases in soluble cations and organic matter were at least partly attributable to the release of cations and OH – by hydrolysis of silicate minerals.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".