Effects of defoliation on growth and N fixation in<i>Alnus tenuifolia</i>: Consequences for changing disturbance regimes at high latitudes
Bibliographic record
Abstract
:Alder plays an important role in the nitrogen (N) economy of boreal forests because of its high capacity for atmospheric N fixation. Range expansion and increased insect and/or pathogen attack are two potential consequences of climate change that may result in significant, albeit opposite, effects on these systems through influences on alder-mediated N inputs. This study contrasted the effects of weekly defoliation at different intensities on growth and N fixation in Alnus tenuifolia seedlings with recovery of these traits following a single but intensive defoliation event. Weekly removal of 15, 25, or 40% leaf area for 9 weeks reduced total plant weight by 7, 13, and 29%, respectively, and led to progressive increases in leaf weight ratio at the expense of shoot growth. Although maximum photosynthetic rates (Pmax) were similar among treatments between defoliation events, increasing levels of defoliation led to progressive short-term declines in Pmax immediately following treatments. Plants with 40% leaf removal had N fixation rates (48.3 ± 2.4 μmol N·g-1·h-1) that were 67% less than undefoliated plants (147.6 ± 8.9 μmol N·g-1·h-1), and even the lowest level of leaf removal led to significant reductions in fixation rates relative to controls. In the recovery experiment, N fixation rates in defoliated plants (158.4± 12.1 μmol N·g-1·h-1) were 40% less than control values (264.1± 18.3 μmol N·g-1·h-1) 24 h following defoliation. After 28 d of regrowth, the total biomasses of defoliated and control plants were indistinguishable; however, N fixation rate in defoliated plants (39.2 ± 2.0 μmol N·g-1·h-1) remained 73% less than that of control plants, suggesting a strong competition between symbiont and host sinks for photosynthate.
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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) | 0.000 | 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 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".