Characterization of soil P in coastal forest chronosequences of southern Vancouver Island: effects of climate and harvesting disturbance
Bibliographic record
Abstract
Limitation of tree growth due to inadequate P supply has been found for young plantations following harvesting of old-growth in high rainfall areas of coastal British Columbia. To understand the reasons for P limitation, we investigated P chemistry in mineral soil to 50 cm depth in sites from the Coastal Forest Chronosequence project on Vancouver Island. This allowed comparison of biogeoclimatic subzone (higher rainfall on west than east coast sites) and of time from harvesting disturbance (seral stage). Available (Bray 1) P was significantly higher (P < 0.001) on the drier east side (up to 50 mg kg−1), than on the west side (<5 mg kg−1), although total P values were less divergent (694 mg kg−1, east and 534 mg kg−1, west). There were no significant seral stage effects on total and available P. Extraction with 0.5 M NaOH recovered 50–60% of total P, except for samples from 10–30 cm depth on the west side, for which only 20% was recovered, an effect not found for C. Analysis of the NaOH extracts by 31P nuclear magnetic resonance (NMR) spectroscopy showed much higher proportions of orthophosphate P on the east side. West side extracts were higher in organic P forms, especially diesters, typical of forest ecosystems with restricted nutrient cycling and high precipitation. On the west side, low concentrations of available P, higher proportions of organic P in NaOH extracts, and depression of NaOH extractability at 10–30 cm are consistent with P being a limiting nutrient for tree growth, a problem that may be exacerbated by harvesting disturbance. Key words: Forest chronosequences, harvesting disturbance, 31P NMR, P cycling, organic P
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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 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| 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".