Response of the natural abundance of<sup>15</sup>N in forest soils and foliage to high nitrate loss following clear-cutting
Bibliographic record
Abstract
Export of microbially produced nitrate from an ecosystem is expected to increase δ 15 N in the remaining soil organic matter and NH 4 + . To test the hypothesis that nitrification and nitrate loss induced by clear-cutting cause an increase in soil and foliar δ 15 N, we measured δ 15 N in a clear-cut watershed at the Hubbard Brook Experimental Forest, New Hampshire. δ 15 N ranged from 0.02 in the Oie horizon to 7.7 in the Bs2 horizon prior to clear-cutting and increased significantly by 1.3 in the Oie horizon and 0.9 in the Oa horizon 3 years after clear-cutting. Fifteen years after clear-cutting, δ 15 N in both O horizons decreased to near-initial values. No significant temporal changes in the Bs2 and C horizons δ 15 N were observed. Foliar δ 15 N was highest (1.7) the first 2 years after clear-cutting and was significantly higher than in the reference watershed (mean δ 15 N = 1.2), decreasing to 0.0 35 years after clear-cutting and to 1.3 911 years after clear-cutting. Increased foliar δ 15 N coincided with increased stream-water nitrate concentration, suggesting that the increased nitrification responsible for elevated stream-water nitrate may also have caused an enrichment of the plant-available ammonium pool. The response observed in this catchment also suggests that sampling of soil or foliar δ 15 N may provide a practical alternative to long time series of stream chemistry for evaluating nitrogen saturation of forested ecosystems.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".