Major altitudinal shifts in Andean vegetation on the Amazonian flank show temporary loss of biota in the Holocene
Bibliographic record
Abstract
The Lateglacial and Holocene vegetation history from the Amazonian flank of the south Colombian Andes has been studied in a 12 m long sediment core from Lake La Cocha (2780 m altitude). 18 AMS 14 C ages and 550 pollen samples yielded a history of a ~25 yr resolution. Montane forest extended up to 2200 m during the Lateglacial and shifted during a 10,000 yr period with millennial-scale and centennial-scale variability superimposed, to its present-day limit at 3550 m. We hypothesise that Intertropical Convergence Zone (ITCZ)-modulated trans-Amazonian moisture flows are an important driver of forest dynamics but influence of ENSO (El Niño Southern Oscillation) variability after 7000 yr BP may also be reflected in the record. Quasi-forest stability lasted for maximally 200 to 600 years. Upslope forest shifts up to 300 m/100 yr, reflecting a 1.5°C temperature increase were common during the Holocene. During several intervals of fastest forest migration the subpáramo disappeared for short intervals of time, suggesting that upslope forest migration exceeded the migration capacity of the subpáramo biome. From Lateglacial time onwards a suite of arboreal taxa show successive upslope expansion events, suggesting internal forest dynamics during the shift of residence areas from their glacial to Holocene altitudinal intervals. Logging, preferentially Podocarpus, frequent fires, forest disturbance and changes of the diatom flora in the lake suggest strong human impact after 1405 cal. yr BP.
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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 | 0.000 | 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) | 0.002 | 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".