Decreasing photosynthesis at different spatial scales during the late growing season on a boreal cutover
Bibliographic record
Abstract
The relationship between photosynthesis and accumulated cold degree days (CDD) over the late growing season was examined at the shoot, ecosystem and landscape scales in a boreal cutover in eastern Canada predominated by black spruce (Picea mariana Mill. BSP), lowbush blueberry (Vaccinium angustifolium Ait.) and sheep laurel (Kalmia angustifolia L.). We calculated CDD as the sum of minimum daily temperatures below a 5 degrees C threshold. Light-saturated photosynthesis at the shoot level (A(max)) of black spruce and V. angustifolium decreased steadily with increasing CDD once temperatures below the CDD threshold value became frequent in mid-September, whereas K. angustifolia showed a more irregular pattern. Tissue acclimation played an important role in the decrease in A(max) as the season progressed, but only V. angustifolium showed decreasing foliar nitrogen concentrations. Based on eddy covariance flux tower data, maximum daily gross primary productivity (GPP(max)-tower) at the ecosystem level was more strongly related to CDD (r(2) = 0.59) than was maximum daily net ecosystem exchange (r(2) = 0.32). The GPP(max) was likely influenced by both tissue acclimation and the direct effects of changing temperatures and irradiances on physiological rates. Mean daily GPP, calculated for consecutive 8-day periods for a 25 km(2) area around the tower by the MODIS MOD17A2 Collection 4 satellite algorithm (GPP- MODIS), decreased more rapidly with increasing CDD than did GPP(max)-tower. Although GPP-MODIS was closely correlated with mean daily GPP from the tower (GPP(daily)-tower, r(2) = 0.95) over the late growing season, the former was about twice as high. Although MODIS estimates of air temperature closely tracked the ground data, the maximum light-use efficiency parameter used by the MODIS algorithm was much higher than that indicated by the tower measurements. There was a 3% decline in GPP(max)-tower with an increase of 10 CDD, corresponding to the percent decline in branch-level A(max) of black spruce and V. angustifolium.
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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 | 0.000 | 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 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".