Overstory density, short growing seasons, and moisture limit Engelmann spruce establishment over time in high-elevation managed stands
Bibliographic record
Abstract
For tree species with narrow ranges of climate suitability for regeneration such as Engelmann spruce (Picea engelmannii Parry ex Engelm.), understanding biophysical influences on juvenile establishment over time is crucial for supporting silvicultural practices responsive to climate change. We developed count-based models to identify abiotic and biotic variables explaining annual spruce establishment over 20–30 years following silvicultural regeneration treatments across 24 spruce stands in Colorado. Covariates retained in our final model encompassed information on climate, physiography, stand structure, and time. Establishment was positively related to germination- and second-year frost-free period beginning dates, indicating that moisture limitations at early life stages may be alleviated by longer retention of snowpack. Yet, recruits were positively influenced by both lengthier frost-free periods and lower heat–moisture indices, suggesting a tension between growing-season length and moisture limitations for physiological maturation, lasting 5 years after germination. Establishment was also limited by higher elevations and lower solar radiation, further suggesting cold limitations in these stands. Moreover, overstory basal area negatively influenced recruitment, suggesting an inhibitive effect on light and precipitation availability for seedlings. Our findings extend similar conclusions from harsher treeline environments to high-elevation managed stands but illustrate stronger relative effects of overstory density and cold-related limitations and suggest transitions in climate effects with life stages.
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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 | 0.001 |
| 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 | 0.001 | 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".