Isolation and identification of endophytic diazotrophs from lodgepole pine trees growing at unreclaimed gravel mining pits in central interior British Columbia, Canada
Bibliographic record
Abstract
Unreclaimed gravel mining pits located in the central interior of British Columbia have very limited soil nitrogen (N) levels due to gravelly textured soils with weak profile development, no organic forest floor, and low atmospheric N inputs through precipitation. However, lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) trees can be found growing well at these pits with tissue N content and growth rate unaffected by extremely low soil N levels, indicating that pine trees are able to meet their N requirements from an unknown source. We hypothesized that biological N fixation by bacteria living in the tree tissues (known as endophytic diazotrophs) could be a potential N source for these trees. To test this hypothesis, we isolated 77 potential endophytic diazotrophs from needle, stem, and root tissues of pine trees on N-free culture medium. Of these, 32 bacteria showed positive N-fixing ability when tested for nitrogenase enzyme activity using the acetylene reduction assay. These endophytic N-fixing bacteria were identified as mainly belonging to the genera Pseudomonas, Bacillus, Paenibacillus, and Rhizobium, which are well known for their plant-beneficial traits including N fixation. Therefore, it can be concluded that pine trees growing at these severely N-limited gravel pits naturally harbour endophytic diazotrophs, which could be involved in sustaining their vigorous growth, possibly through biological N fixation.
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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 | 0.002 | 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) | 0.000 | 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 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".