Nitrogen limitation in a sweetgum plantation: implications for carbon allocation and storage
Bibliographic record
Abstract
The N status of temperate forests is closely linked to their C fluxes, and altered C or N availability may affect ecosystem C storage through changes in forest production and C allocation. We proposed that increased fine-root production previously observed in a sweetgum ( Liquidambar styraciflua L.) forest in response to elevated [CO2] was a physiological response to N limitation. To examine this premise, we fertilized plots in the sweetgum plantation adjacent to the Oak Ridge National Laboratory free-air CO2-enrichment (FACE) experiment. We hypothesized that N fertilization would increase sweetgum net primary production, leaf [N], and the relative flux of C to wood production. Annual additions of 200 kg·ha–1 of N as urea increased soil N availability, which increased stand net primary production, stand N uptake, and N requirement by about one-third. Increased leaf [N] and leaf area production in the fertilized plots increased stem production and shifted relative flux of C to wood production. We conclude that sweetgum production on this site is limited by soil N availability and a decreased fraction of net primary production in fine-root production with N addition is consistent with the premise that increased fine-root production in the adjacent FACE experiment is in response to N limitation.
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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".