Changes in biomass and root:shoot ratio of field-grown Canada thistle (<i>Cirsium arvense</i>), a noxious, invasive weed, with elevated CO<sub>2</sub>: implications for control with glyphosate
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Bibliographic record
Abstract
Canada thistle was grown under field conditions in 2000 and 2003 at ambient and elevated (∼ 350 μmol mol −1 above ambient) carbon dioxide [CO 2 ] to assess how rising [CO 2 ] alters growth, biomass allocation, and efficacy of the postemergent herbicide glyphosate. By the time of glyphosate application, approximately 2 mo after emergence, elevated CO 2 had resulted in significant increases in both root and shoot biomass. However, the relative positive effect of [CO 2 ] was much larger for root, relative to shoot growth, during this period (2.5- to 3.3-fold vs. 1.2- to 1.4-fold, respectively) with a subsequent increase in root to shoot ratio. Glyphosate was applied at 2.24 kg ae ha −1 in 2000 and 2003. Subjective classification of leaf damage in shoots after spraying indicated no significant difference in the extent of necrosis in aboveground tissue as a function of CO 2 concentration. After a 6-wk regrowth period, significant reductions in shoot and root biomass relative to unsprayed plots were observed under ambient [CO 2 ]. However, the decrease in the ratio of sprayed to unsprayed biomass was significantly less at elevated relative to ambient [CO 2 ] conditions for roots in both years, and no difference in shoot biomass was observed between sprayed and unsprayed plots for Canada thistle grown at elevated [CO 2 ] in either year. The observed reduction in glyphosate efficacy at the enriched [CO 2 ] treatment did not appear to be associated with differential herbicide uptake, suggesting that tolerance was simply a dilution effect, related to the large stimulation of root relative to shoot biomass at elevated [CO 2 ]. Overall, the study indicates that carbon dioxide–induced increases in root biomass could make Canada thistle and other perennial weeds that reproduce asexually from belowground organs harder to control in a higher [CO 2 ] world.
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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 | 0.000 | 0.000 |
| 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 | 0.000 | 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 it