Post-Clearcutting Chronosequence in the B.C. Coastal Western Hemlock Zone
Bibliographic record
Abstract
We estimated the magnitude of various sinks for forest floor N released by decomposition in a 400-year-old stand and along a 26-year post-clearcutting chronosequence in a Pacific silver fir (Abies amabilis [Dougl.] Forbes) and western hemlock (Tsuga heterophylla [Raf.] Sarg.) ecosystem on Vancouver Island. The total biomass and N-content of various components of the overstory and understory vegetation were measured, as well as the upper mineral-soil N-storage, and the fluxes of dissolved forms of N in forest floor and mineral-soil leachates. The overstory vegetation was not an important sink for N until at least 10 years after clearcutting; uptake by trees was not a significant sink for the post-clearcutting assart flush. In contrast, the early-seral understory vegetation played a small but probably significant role during the assart period. Competition for N between the understory and overstory vegetation during the first 10 years was probably not significant because the amount of N released from the forest floor far exceeded the amount of N taken up by either of these two components. Total leaching losses of dissolved-N between 3 and 12 years after clearcutting did not appear to vary significantly from total leaching losses in the old forest. Based on the lysimeter data, the upper mineral soil appeared to have the biological and/or chemical capacity to prevent most of the N released from the forest floor after clearcutting from moving down to below the rooting zone. However, we do not conclude from this that the majority of the N released is retained within the ecosystem. In a subsequent paper we develop a forest floor N-bud-get model to evaluate whether or not this is the case.
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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 | 0.001 | 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) | 0.001 | 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".