Phosphorus forms and response to changes in pH in acid-sensitive soils on the Precambrian Shield
Bibliographic record
Abstract
Baker, S. R., Watmough, S. A. and Eimers, M. C. 2015. Phosphorus forms and response to changes in pH in acid-sensitive soils on the Precambrian Shield. Can. J. Soil Sci. 95: 95-108. Soil acidification may explain declines in total phosphorus (TP) levels that have been observed in surface waters in central Ontario, Canada, but much of the research on phosphorus (P) mobility in pH manipulated soils has been performed at high P concentrations (i.e., >500 µM). This study investigated P fractionation in acidic (pH≤4.6) soils in south-central Ontario and relationships between soil pH and P sorption at relatively low P concentrations to test whether long-term declines in soil pH could have increased soil P sorption. Soils from three forested catchments that vary naturally in soil pH and outlet stream [TP] (0.1-0.4 µM in 2008) had very similar soil P concentrations and distributions (Hedley fractionation). Only hydrochloric-acid extractable P (i.e., apatite) differed amongst catchments and was greatest at the catchment with the highest stream [TP]. The fraction of P present as labile/soluble P did not decline with pH as expected and experiments indicated that P sorption at P concentrations between 4.52 and 452.1 µM was insensitive to manipulated solution pH. Soils were, however, able to sorb >90% of P added in sorption experiments at [P]≤452.1 µM. These results suggest that acidification-induced P sorption in upland soils has not contributed to observed decreases in surface water TP concentrations.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".