Pollen evidence of Late Holocene treeline fluctuation from the southern Coast Mountains, British Columbia
Bibliographic record
Abstract
Palynological records of Holocene climate change in the southern Coast Mountains identify the Neoglacial period, subsequent to 6 600 BP, as cooler and wetter than the preceding Hypsithermal. However, geomorphic evidence of alpine glacier advance suggests that there were three distinct cooler/wetter periods during the Neoglacial. By careful selection of a sensitive alpine site this study has enabled the recognition of two of these stages in a palynological record of Neoglacial climate. Pollen spectra, conifer needle macrofossils, organic matter content, and magnetic susceptibility were assessed for a continuous sequence of sediment from Blowdown Lake, which has a basal date older than 4 000 BP. Comparison of the Picea/Pinus pollen ratios from the core with modern surface samples suggests that treeline was at least 100 m above its present elevation until 3 400 BP, indicating that summer temperatures were at least 0.7 ° C above the present. Treeline declined to near present levels by around 2 400 BP. Two subsequent periods of lower treeline were identified which appear to correlate approximately with the Tiedemann and Late Neoglacial periods of glacier advance in southwestern British Columbia. Differences between Picea/Pinus and Abies/Pinus ratios from the core are consistent with the autecology of the species. This suggests that the sensitivity of the pollen ratio approach to reconstructing treeline is dependent on the ratios selected.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 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) | 0.002 | 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".