Asymbiotic nitrogen fixation on woody roots of Norway spruce and silver birch
Bibliographic record
Abstract
High rates of asymbiotic nitrogen (N) fixation have been measured in woody roots in temperate forests, but this rate has not been quantified in boreal forests. We studied the asymbiotic N2 fixation associated with living and decomposing woody roots of Norway spruce (Picea abies (L.) H. Karst.) in three sites in Finland. In addition, tree species effect was studied in one site that included Norway spruce and silver birch (Betula pendula Roth.) monocultures and mixed stands. The rate of N2 fixation measured as nitrogenase activity was affected by host tree species; spruce roots were the most active (0.67 C2H4·day–1·(g dry mass)–1 in spruce monocultures). The activity was not statistically different in decayed and living root samples, and moisture content did not explain the observed high variability in nitrogenase activity. In a birch–spruce mixed stand, the average N2 fixation in woody roots was 0.17 kg N·ha−1·year−1, whereas in Norway spruce dominated sites, the activity ranged from 0.06 to 0.15 kg N·ha−1·year−1. The N2 fixation in decaying and living woody roots is an important contributor to the long-term total N balance of the forest. However, the estimated rate of N2 fixation is low compared with atmospheric N deposition.
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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 | 0.000 |
| 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 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".