Effects of pre-commercial thinning on the dynamics of uneven-aged interior Douglas-fir (Pseudotsuga menziesii var. glauca) stands in British Columbia, Canada
Bibliographic record
Abstract
This dissertation sought to gain insight into the impacts of pre-commercial thinning (PCT) treatments on the development of uneven-aged interior Douglas-fir (IDF) stands in central British Columbia, Canada. Data were available from 24 plots in 3 blocks of a long-term study on the response to PCT, comprised of 5 measurements over 21 years. Growth responses at the stand level and for trees of 3 conifer species (interior Douglas-fir - FD; interior spruce - SX; and lodgepole pine - PL) were assessed. The PCT enhanced the growth rate of the residual trees at the stand and individual tree levels. I compared the performance of 13 competition indices (5 non-spatial and 8 spatially-explicit) to predict individual tree periodic annual basal area increment (PABAI) of the three species and investigated whether neighbouring trees competed with subject trees independently of species identity. Also, I examined the differences in individual tree basal area growth among the three species over time under different levels of competition. The spatially-explicit competition indices were more effective in predicting PABAI than their non-spatial counterparts for all species. Asymmetrical relationships between these species and their neighbours were observed, indicating that aboveground competition for light was the main factor limiting growth. FD had higher PABAI than SX and PL, irrespective of the competition intensity. The Gini coefficient (GC) and the growth dominance coefficient (GDc) were applied to the thinned and unthinned plots to determine how size inequality and growth dominance changed over time. Size inequality was reduced following thinning. GDc decreased with increasing thinning intensity, suggesting that smaller trees were proportionately more vigorous as the thinning intensity increased. Temporal changes in tree spatial patterns were assessed using spatial point pattern analysis. The thinning treatments influenced the spatial pattern of trees with a trend away from clumpy distributions and towards random or regular spatial patterns, while the unthinned plots remained clustered through time. This study provides new insights into the stand dynamics of the uneven-aged IDF stands as observed over a 23-year period, particularly as it relates to different applications of PCT.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".