Light-use efficiency of native and hybrid poplar genotypes at high levels of intracanopy competition
Bibliographic record
Abstract
In southern Wisconsin, U.S.A., tree growth and associated canopy traits were compared among five native and hybrid genotypes of poplar (Populus spp.) in replicated, monoclonal stands planted at a 1 × 1 m spacing. The overall objective of this study was to assess clonal suitability to cultural conditions entailing high levels of intracanopy competition (such as high-density plantations or long rotations) and to identify selection criteria suitable to such conditions. Two of the clones were Populus deltoides Bartr., two were P. deltoides × Populus nigra L. (DN) crosses, and the fifth was a P. nigra × Populus maximowiczii A. Henry (NM) cross. In the third year after establishment, variation in aboveground biomass gain (ANBG) was analyzed in relation to canopy light interception (IPAR) and canopy light-use efficiency (LUE) during a 31-day period when growing conditions were most favorable (late June through late July). ANBG in this interval varied by twofold among genotypes (2.765.78 Mg·ha 1 ), and it was highest in the two P. deltoides clones, followed by the NM and DN hybrids, respectively. Across genotypes, ANBG was unrelated to IPAR, which varied by only 5%. Instead, it was strongly and positively related (r 2 = 0.99) to the twofold variation in LUE (1.062.22 g·MJ 1 ). Among measured canopy traits, the best predictor of LUE (r 2 = 0.88) was an additive combination of factors associated to the optimization of canopy photosynthesis: LUE was negatively related to both the canopy light-extinction coefficient and compensation irradiance at the canopy base. We infer from these findings that poplar genotypes can vary considerably in LUE and, correspondingly, in the extent to which photosynthesis is optimized in dense canopies. Furthermore, the low LUE among hybrid genotypes at this level of intracanopy competition may reflect a bias in "tree improvement" efforts towards maximizing biomass production under conditions of relatively low competition.
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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 | 0.000 |
| 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".