Characterization of Boreal-Arctic Vegetation Growth Phases and Active Soil Layer Dynamics in the High-Latitudes of North America: A Study Combining Multi-Year In Situ and Satellite-Based Observations
Bibliographic record
Abstract
This dissertation examined the seasonal freeze/thaw activity in boreal-Arctic soils and vegetation physiology in Alaska, USA and Alberta, Canada, using in situ environmental measurements and passive microwave satellite observations. The boreal-Arctic high-latitudes have been experiencing ecosystem changes more rapidly in comparison to the rest of Earth due to the presently warming climatic conditions having a magnified effect over Polar Regions. Currently, the boreal-Arctic is a carbon sink; however, recent studies indicate a shift over the next century to become a carbon source. High-latitude vegetation and cold soil dynamics are influenced by climatic shifts and are largely responsible for the regions atmospheric carbon fluxes. Under a warming climate, soils are thawing for extended periods of time, allowing for heightened aerobic decomposition of organic matter in the soil, increasing soil carbon emissions. Simultaneously, vegetation performs photosynthesis longer, resulting in increased sequestering of atmospheric carbon. Regional and global climate affect one another through land-atmosphere carbon feedbacks. The strength, and contribution, of this study lies in high quality fine-scale in situ datasets day-of-year occurrences for soil state transitions and vegetation growth phenophase activity at site-specific locations. Findings include (1) a more thermally variable active layer in dry tundra compared to wet tundra; (2) active layer isothermal conditions are established rapidly in the fall ( ~ 2 days) but not in the spring (~ 11 days); (3) boreal willow shrubs (Salix Spp.) have the shortest exiting dormancy period (11 days) yet the longest active above ground stem growth (61 days); (4) moist bog type environments were shown to be the optimal spruce (Picea Spp.) growth environments (active trunk growth duration of ~ 55 days); and (5) AMSR satellite data were shown to preemptively estimate land surface condition change compared to in-situ measurements during the spring transition for both tundra types while lagging during the fall transition and freeze-up periods. These results elucidate the need for further field work campaigns collecting active soil layer measurements in order to precisely gauge the seasonally thawed and active windows for soil and vegetation. Outcomes of this research include increased availability of quantified soil and vegetation activity windows. Conclusions include prospects which are valuable for studies attempting to optimize carbon flux estimations using freeze/thaw microwave satellite datasets.
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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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) | 0.000 | 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 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".