Influence of rising atmospheric CO <i>2</i> since 1900 on early growth and photosynthetic response of a noxious invasive weed, Canada thistle ( <i>Cirsium</i> <i>arvense</i> )
Bibliographic record
Abstract
Using climate-controlled growth chambers, the growth, morphology and photosynthetic response of Canada thistle ( Cirsium arvense L. Scop.), a recognized invasive weed, was determined at CO2 concentrations ([CO2]) of 285, 382 and 721 µmol mol–1 during the vegetative state. These concentrations correspond roughly to ambient [CO2] from 1900, 2001 and those projected for 2100, respectively. At the end of the vegetative stage, leaves grown at 721 µmol mol–1 still had significantly higher photosynthetic rates under the growth conditions, relative to the 285 or 382 µmol mol–1 CO2 treatment. Significant differences in leaf morphology, particularly the number and length of leaf spines, were also observed, with spine number and length increasing as a function of [CO2]. At the end of the vegetative stage, at 54 d after sowing (DAS), whole plant biomass had increased by 69% for the elevated (720 µmol mol–1) CO2 treatment relative to current ambient CO2. However, biomass had increased by 126% for current ambient (380 µmol mol–1) relative to the concentration that existed in 1900 (285 µmol mol–1). Data from this study indicate that rising [CO2] may have already had a substantial influence on the vegetative development of Canada thistle, by significantly stimulating growth and photosynthesis, as well as altering leaf defenses to potential herbivory. Overall, these changes could have important implications for growth and control of this noxious weed as atmospheric CO2 continues to increase.
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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) | 0.000 | 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".