The impact of nitrogen supply on the potential response of a noxious, invasive weed, Canada thistle (<i>Cirsium arvense</i>) to recent increases in atmospheric carbon dioxide
Bibliographic record
Abstract
A recognized invasive weed, Canada thistle (Cirsium arvense L. Scop.) was grown at ambient and pre‐ambient concentrations of atmospheric carbon dioxide [CO2] (373 and 287 μmol mol−1, respectively) at three levels of supplemental nitrogen (N) (3, 6 and 14.5 mM) from seeding until flowering [77 days after sowing (DAS)]. The primary objective of the study was to determine if N supply limited the potential photosynthetic and growth response of this species to the increase in atmospheric [CO2] which occurred during the 20th century (i.e. approximately 290 to 370 μmol mol−1 CO2). Leaf photosynthesis increased both as a function of growth [CO2] and N supply during the first 46 DAS. Although by 46 DAS photosynthetic acclimation was observed relative to a common measurement CO2 concentration, there was no interaction with N supply. Both [CO2] and N increased biomass, relative growth rates and leaf area whereas root : shoot ratio was increased by CO2 and decreased by increasing N; however, N supply did not effect the relative response to [CO2] for any measured vegetative parameter up to 77 DAS. Due to the relative stimulation of shoot biomass, total above‐ground N increased at elevated [CO2] for all levels of supplemental N, but nitrogen use efficiency (NUE) did not differ as a function of [CO2]. Overall, these data suggest that any potential response to increased atmospheric [CO2] in recent decades for this noxious weedy species was probably not limited by nitrogen supply.
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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 | 0.000 |
| 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".