Age and growth reductions increase the proportion of dark heartwood in sugar maple at the northern limit of its range
Bibliographic record
Abstract
Abstract The wood of sugar maple (Acer saccharum Marsh.) in the northernmost part of the species range often exhibits high proportions of discoloured wood at the centre of the stems, which is referred to as dark heartwood. This defect significantly decreases the wood market value of the species, which, in turn, challenges the implementation of state-of-the art silvicultural treatments. The causes of dark heartwood are associated with trauma and the colder climate of the northern regions. In this study, we investigate factors influencing the occurrence of dark heartwood in sugar maple’s northern populations, considering tree age, vigour, stem growth, and local climate. We also aimed to determine whether the proportion of dark heartwood is higher in northern stands compared to more southern ones. We collected samples from 302 sugar maple stems at 16 sites within two bioclimatic domains of Quebec, Canada, i.e. the balsam fir–yellow birch domain (representing the northern limit of the sugar maple range) and the sugar maple–yellow birch domain (representing a more southern location within the range). Our results indicate a positive relationship between dark heartwood proportions and stem age, as well as with the amplitude of the maximum growth reduction throughout the tree’s lifespan and the length of the longest suppression period. We also observed significantly higher dark heartwood proportion for a given tree age in northern stands. The results suggest that silvicultural systems aiming to release suppressed crop trees through group selection using a cut-to-length system could favour the development of high quality timber.
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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 | 0.001 | 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".