<i>Robinia pseudoacacia,</i> a nitrogen-fixing tree, facilitates the future growth of neighboring trees in Black Rock Forest
Bibliographic record
Abstract
Trees that form symbioses with nitrogen (N)-fixing bacteria (N fixers) have long been thought to facilitate neighbors’ growth by providing new N, but some data do not show facilitation. Two hypotheses to explain the lack of facilitation are that (1) N fixers may decrease the amount of N they fix over time, reducing the N supply to their neighbors and (2) the effect of facilitation might take longer than the 1–5-year interval of most studies. In this study, we tested these hypotheses with the N-fixing tree Robinia pseudoacacia L. and its nonfixing neighbors, using tree ring N isotopes to estimate past N fixation and tree ring width to estimate past size and growth. Where the isotopes allowed a constrained estimate of N fixation, we did not find support for the first hypothesis: 51% of Robinia’s N came from fixation throughout its 60-year lifespan, with little variation across age. In support of the second hypothesis, we found that Robinia enhanced growth of neighboring trees in the future (up to 14 years) more than in the present. This delayed effect matches the expected timing of facilitation by N fixers and indicates that single-census studies might underestimate the degree to which N fixers facilitate forest growth.
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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 | 0.000 | 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) | 0.001 | 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".