Longer photoperiods negate the CO<sub>2</sub> stimulation of photosynthesis in <i>Betula papyrifera</i> Marsh: Implications to climate change‐induced migration
Bibliographic record
Abstract
Abstract In response to global warming, trees are expected to shift their distribution ranges to higher latitudes. The range shift will expose them to novel environmental conditions, such as new photoperiod regimes. These factors can interact with rising atmospheric CO2 ([CO2]) to affect trees' physiology and growth. This study simulated future environmental conditions to investigate photosynthetic responses to changes in photoperiod regimes (seed origin [48°N], 52, 55, and 58°N) and [CO2] (ambient 400 vs. elevated 1000 μmol mol−1) in white birch (Betula papyrifera Marsh.) seedlings. Our results show that elevated [CO2] stimulated leaf photosynthesis (Pn) at the two lower latitudes (48 and 52°N). However, this stimulation by elevated [CO2] was lost in the two higher latitudes (55 and 58°N). Elevated [CO2] led to the downregulation of maximum Rubisco activity (Vcmax) for the two higher latitudes, and maximum electron transport rate (Jmax) and triose phosphate utilization (TPU) at 58°N, while it enhanced Jmax and TPU for the two lower latitudes. Increased instantaneous water‐use efficiency (IWUE) for the two lower latitudes was primarily attributed to the CO2 stimulation of Pn while the higher IWUE under the photoperiod regimes of 55 and 58°N latitudes was explained by reduced water loss. Photoperiod effects varied with [CO2]: Pn increased at the photoperiod regimes of 55 and 58°N in ambient [CO2] while it tended to decline under these photoperiods in elevated [CO2]. Our study suggests that the photosynthesis of white birch will likely respond negatively to northward migration or seed transfer in response to climate change.
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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".