Long-term response of soil and stem wood properties to repeated nitrogen fertilization in a N-limited Scots pine stand
Bibliographic record
Abstract
Abstract Nitrogen is the nutrient mainly limiting forest growth on mineral soil sites in the boreal regions. The objective of this study was to find out the response of stem wood N to repeated fertilizations and to find out their long-lasting effects on soil organic matter composition, focusing on C and N cycling processes and concentrations of condensed tannins. The site was located in a relatively unfertile Scots pine (Pinus sylvestris L.) stand in eastern Finland. The treatments were three levels of N fertilization (0, 150, 300 kg/ha) applied four times at 5-year intervals with the last addition 29 years ago. The N additions had not changed the pH of the humus layer but resulted in higher availability of N. The C-to-N ratio of organic matter decreased with increasing N addition. The treatment of 300 kg/ha increased the net N mineralization rate and the ratio of net N mineralization/microbial biomass N and decreased the amount of C in the microbial biomass and its C-to-N ratio and the concentration of condensed tannins. Net nitrification and extractable nitrate were negligible in all soils. In soil diffusive fluxes, NH4-, NO3- and amino acid-N were all detected by in situ microdialysis sampling; the results showed large variation but supported higher N availability in N fertilized soil. The N fertilization increased tree-ring widths and the effect lasted for about 10 years after the last fertilization event. Nitrogen content and the N isotopic ratio 15N/14N (δ15N) in tree-rings increased both after the first N addition in the treatment of 300 kg/ha. In conclusion, soil properties still indicated higher N availability in the N fertilized soil after three decades since the latest fertilization, but the response of tree diameter growth had faded out after a much shorter period.
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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) | 0.000 | 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".