Nitrogen and carbon cycling in a New Zealand pumice soil under a manuka (Leptospermum scoparium) and kanuka (Kunzea ericoides) shrubland
Bibliographic record
Abstract
Shrubland communities dominated by manuka (Leptospermum scoparium J. Forst. and G. Forst.) and kanuka (Kunzea ericoides var. ericoides ((A. Rich) J. Thompson) are widespread throughout New Zealand. They frequently colonise disturbed land surfaces and are important for erosion mitigation, and also for their capacity to act as a carbon (C) sink. We here investigate C and nitrogen (N) cycling in 3 stands (~26–56 years old) that had established on a repeatedly burned forest site on a Podzolic Orthic Pumice soil in the Turangi area, central North Island. For comparison, limited measurements of N cycling were also made at other manuka–kanuka sites on non-volcanic soils. Leaf N concentrations at the Turangi site were 11.8–13.9 g/kg, and lower than those at many of the other manuka–kanuka stands. Total annual litterfall and N content increased with stand age, as did total N concentrations in FH material and mineral soil (0–100 mm depth). Total C concentrations in mineral soil did not, however, differ significantly in the 3 stands. Levels of soil microbial C and N, rates of carbon dioxide production, and metabolic coefficients (qCO2 values) suggest C cycling could be fairly rapid at this site. In contrast, rates of net mineral-N and nitrate-N production were low to very low compared with those in similar pumice soils under angiosperm–conifer forests, and in the non-volcanic soils under other manuka–kanuka stands. Low N availability and tight N cycling at the Turangi site are thereby strongly suggested. No definitive explanation for the atypically low N availability at this site is apparent, although the possible effects of previous forest burnings may have been a contributing factor. The continued growth of these shrubs, nevertheless, shows they can compete successfully for the N that does become available through gross N mineralisation in the Turangi ecosystem.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| 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".