Phenology of vegetation light-use efficiency and reflectance: experiment over two boreal ecosystems
Bibliographic record
Abstract
Understanding phenological changes in vegetation through spectral data needs further exploration in order to maximize the contribution that remote sensing technologies make to environmental studies. Analyzing temporal trends in reflectance and associated eddy-covariance estimations would allow not only for understanding the seasonality of their relationship, but also for the determination of optimal time frames for airborne / satellite image collection. This research investigates the temporal trends of several vegetation indices and computed vegetation light-use efficiency (LUE) for two major boreal ecosystems (a black spruce forest, and a peatland), in the vicinity of the Eastmain-1 reservoir, James Bay, Northern Quebec. Ground data were collected hourly from August 3rd, 2012 through to September 22nd, 2012 with three representative time classes (9AM, 1PM, 5PM) analyzed in this thesis. The research further investigates the applicability of ground based models of land cover using previously collected Compact Airborne Spectrographic Imager (CASI) data. No statistically significant relationships were found at the black spruce forest site between reflectance and vegetation LUE. However, significant relationships occurred in the mid-morning between the vegetation reflectance indices PRI (photochemical reflectance index), PSRI (plant senescence reflectance index), RVSI (red-edge vegetation stress index) and LUE at the peatland site allowing for vegetation LUE estimations at the landscape level using previously acquired CASI hyperspectral imagery. For both sites, vegetation LUE increases over the data collection period, which is attributed to species' efficiency in more diffuse sunlight from changing sun angle geometry. At both sites, statistically significant seasonal trends in reflectance for the most part, occurred in the morning time class (9AM). Similar results were found with vegetation LUE. This highlights the importance of determining optimal time frames for imagery collection (with the goal of landscape estimations in environmental studies), which in the case of this study, points to the mid-morning.
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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 | 0.001 | 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 | 0.001 | 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 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".