The interaction between nitrogen source, soil pH, and drought in the growth and physiology of three poplar clonesThis article is one of a selection of papers published in the Special Issue on Poplar Research in Canada.
Bibliographic record
Abstract
The objective of this study was to understand how nitrogen (N) source, soil pH, and drought interact in the growth and water-use efficiency of poplars. Rooted cuttings from two hybrid poplar clones, 24 (Walker) ( Populus deltoides × Populus ×petrowskyana ), and 794 (Brooks 6) (Populus deltoides × Populus ×petrowskyana), and one native balsam poplar clone 1004 ( Populus balsamifera L.), were grown in a greenhouse for a period of 8 weeks. Trees received a combination of two N sources (ammonium sulphate [(NH4)2SO4] and calcium nitrate [Ca(NO3)2]), two soil pHs (5 and 7), and two drought levels (85% and 40% field capacity, as determined by mass). Trees had reduced growth, net photosynthesis, and stomatal conductance with NO3– fertilization, and these effects were accentuated at soil pH 7. The drought treatment only slightly reduced growth and rarely interacted with N source or soil pH. Drought also did not affect instantaneous measurements of water-use efficiency, but it increased δ13C by an average of 0.55‰. The poplar clones used in this study appear to be better adapted to take up N from NH4+ than from NO3–-N sources.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".