Global role of vanadium for nitrogen fixation in extratropical forests
Bibliographic record
Abstract
Biological nitrogen fixation by nitrogenase is often assumed to rely exclusively on molybdenum as an enzymatic cofactor, despite molybdenum scarcity in terrestrial ecosystems and recent demonstrations of vanadium nitrogenase (V-Nase) activity in cryptogamic organisms, collectively responsible for over 40% of terrestrial biological nitrogen input. Here we highlight a global role for vanadium in nitrogen biogeochemistry in extratropical forests’ cryptogams. Measurements in bryophytes and cyanolichens from three continents indicate V-Nase activity in each forest surveyed. We use V-Nase regulation by molybdenum content and nitrogen fixation rates to estimate the global contribution of vanadium to nitrogen fixation by extratropical cryptogams as 30%, with human activities likely responsible for a 30% relative decrease since pre-industrial times. This newly discovered global role of vanadium forces a reevaluation of the nitrogen cycle, where including nitrogenase enzymatic heterogeneity will help better predict the response of the terrestrial carbon sink to global change and understand species biogeography.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".