Boreal conifer seedling responses to experimental competition removal during summer drought
Bibliographic record
Abstract
Abstract The southern range limit of white spruce ( Picea glauca ) in western Canada is believed to arise from effects of moisture limitation on seedling recruitment. Within stands near white spruce’s range limit, the adverse effects of water limitation on seedling growth and survival may be compounded by competition from neighboring understory plants and trees. To test this hypothesis, we conducted a competition removal experiment on white spruce seedlings in the Cypress Hills, an isolated forest landscape within the Canadian Prairies. We measured the height and diameter at root collar of 371 natural seedlings, and then we manually cleared all vegetation within a 75‐cm radius of 83 seedlings to remove local competition from neighboring plants. In addition to removal of neighboring plants, we excavated a 75‐cm radius trench around another 46 of these seedlings to remove competition for belowground resources. We took hemispherical photographs above each seedling to calculate canopy openness (a proxy for light availability) and re‐measured height and diameter over two years to calculate pre‐ and post‐treatment growth. There was a pronounced difference in precipitation between the two years of our experiment, with spring–summer precipitation 58% higher than average in the pre‐treatment year and 62% lower than average in the post‐treatment year. The diameter growth and survival of seedlings growing without competition showed smaller decreases in the dry post‐treatment year than control seedlings. Removing competition by trenching increased the height growth of seedlings located under an open canopy, but not of those growing under heavy shade. These interactions suggest that white spruce regeneration in water‐limited areas is sensitive to both light availability and local competition. Competition exacerbated drought effects on seedlings, which suggests that frequent droughts could have greater negative impacts on boreal tree seedlings that are growing under a closed canopy.
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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) | 0.005 | 0.001 |
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; both teacher heads agree on what is shown here.
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".