High rates of nitrogen fixation of <i>Ulex</i> species in the understory of maritime pine stands and the potential effect of phosphorus fertilization
Bibliographic record
Abstract
Nitrogen (N2) fixation by Ulex species was studied in a range of mature maritime pine (Pinus pinaster Ait.) stands as well as in a phosphorus (P) fertilization trial in a young (6-year-old) open pine stand. The biomass was estimated by allometric relationships, and the percentage of N derived from atmosphere was calculated according to the natural 15N abundance method. Ulex stand biomass was lower in the mature pine stand than in the young open pine stand. In the latter pine stand, Ulex mean annual biomass increment ranged from 1 to 5 Mg·ha1·year1, increasing with P fertilization dose, as did the Ulex stand biomass, ranging from 5.4 to 31.1 Mg·ha1 after six growing seasons in the most highly fertilized treatment. For the sites where the natural 15N abundance method was applicable, the calculated percentage of N in the Ulex europaeus L. tissues derived from atmosphere was very high (mean = 82%; range = 59%100%). At the other sites, the N2 fixation was probably also very important but could not be calculated with confidence. Here, the mean fixation rate of the former sites was used to calculate the N2 fixation flux. The estimated annual N2 fixation flux ranged from 0.5 to 5.1 kg N·ha1·year1 in the mature pine stands. In the young open pine stand, the Ulex understory fixation ranged from 8.1 to 57.4 kg N·ha1·year1, increasing with P fertilization dose. Considering the low levels of N fluxes in theses ecosystems, these figures are very high.
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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 | 0.001 | 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 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".