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 [CO 2 ] (373 and 287 μmol mol −1 , respectively) at three levels of supplemental nitrogen (N) (3, 6 and 14.5 m M ) 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 [CO 2 ] which occurred during the 20th century (i.e. approximately 290 to 370 μmol mol −1 CO 2 ). Leaf photosynthesis increased both as a function of growth [CO 2 ] and N supply during the first 46 DAS. Although by 46 DAS photosynthetic acclimation was observed relative to a common measurement CO 2 concentration, there was no interaction with N supply. Both [CO 2 ] and N increased biomass, relative growth rates and leaf area whereas root : shoot ratio was increased by CO 2 and decreased by increasing N; however, N supply did not effect the relative response to [CO 2 ] for any measured vegetative parameter up to 77 DAS. Due to the relative stimulation of shoot biomass, total above‐ground N increased at elevated [CO 2 ] for all levels of supplemental N, but nitrogen use efficiency (NUE) did not differ as a function of [CO 2 ]. Overall, these data suggest that any potential response to increased atmospheric [CO 2 ] 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 distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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 teacher head, 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".