Subarctic and alpine tree line dynamics during the last 400 years in north‐western and central Canada
Why this work is in the frame
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Bibliographic record
Abstract
Abstract Aim The objectives of this study were to: (1) identify episodes of establishment and mortality of young and mature trees at several sites at the alpine tree line in the western Northwest Territories and the latitudinal tree line in northern Manitoba; (2) infer changes in the structure and location of the tree line from patterns of establishment; (3) evaluate any relationship between these changes and climate; and (4) investigate sources of variability between sampling sites and study areas. Location Taiga Cordillera of the western Mackenzie Mountains in the Northwest Territories, and the western Hudson Bay Lowlands in northern Manitoba, Canada. Methods Recent tree line dynamics were examined at six climatically similar sites: three in the western Mackenzie Mountains and three around Churchill, Manitoba. Dendroecological techniques were employed to construct static age distributions of species present at each site. Static age structures, residuals from modelled age distributions, and reconstructions of dynamic stand density were used to identify patterns of establishment and mortality and to compare these to changes in climate. Results Tree line locations advanced and stand density increased during the early‐to‐mid‐20th century around Churchill, although responses were not uniform across sites or species. Results were less conclusive in the Mackenzie Mountains, although the tree line probably advanced during the late 18th century, and stand infilling occurred during the mid‐20th century. Correlation analyses with temperature suggest that conditions during establishment and particularly during recruitment are crucial for controlling tree line dynamics. Main conclusions Tree line advance and stand infilling have continued to the present at Churchill, while the tree line has stagnated in the western Mackenzie Mountains. The results of this study indicate that site‐ and species‐specific responses play a large role in determining the tree line response at multiple scales, illustrating the complexity of tree line dynamics in the context of a changing climate.
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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 it