Late-Quaternary Climatic and Vegetational Change in the Lower Mackenzie Basin, Northwest Canada
Bibliographic record
Abstract
A 355—cm sediment sequence from Twin Tamarack Lake near Inuvik, Northwest Territories, Canada, provides a 14 500—yr record of pollen percentages and accumulation rates, interpretable in terms of climatic change and plant community dynamics. Four distinct pollen assemblage zones are recognized: a Gramineae—Artemisia—Cyperaceae—Salix zone from 14 500 to 11 800 BP; a Betula glandulosa zone from 11 800 to 8400 BP, subdivided into four subzones (Gramineae—herb, Populus, Salix, and Juniperus); a Picea—Betula zone, from 8400 to 5900 BP; and a Piceae—Betula—Alnus zone from 5900 to 0 BP. The vegetation during the late—glacial at this site (14 500—11 800 BP) was relatively stable, consisting of sparse herb tundra on uplands in a slowly warming climate. Dwarf birch increased during this phase. The early Holocene period of maximum summer radiation produced thermal conditions °10% warmer than present, initiating a change from tundra to woodland at most sites, effected by the efficiently dispersed Populus (chiefly P. balsamifera). Relatively rapid changes in regional vegetation occurred during this period (11 800 to 6500 BP); Juniperus invaded the poplar woodlands, occupying well—drained, favorable sites, and later the slower—dispersed Picea (chiefly P. glauca) arrived and formed stands on alluvial sites, largely replacing poplar. At °7500 BP, Betula papyrifera spread on to the uplands; the accumulation of fuel, accelerated by the spread of conifer woodlands, likely caused an increase in fire frequency, which in turn maintained arboreal birch in the area. Fire opened up the woodlands locally and promoted the spread of Alnus crispa, expressed in the pollen record as a prominent rise in both percentage and PAR values. Picea mariana and other species adapted to mire habitats spread at this time (°7000 BP) as paludification, peat growth, and permafrost aggradation occurred in the extensive lowlands. The termination of summers warmer than at present (°6000 BP) initiated the development of a relatively stable vegetation that has persisted to the present.
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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) | 0.060 | 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 teacher head, 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".