Role of permafrost thaw transitions in biogeochemical nitrogen cycling
Bibliographic record
Abstract
Significant organic nitrogen (ON) stocks have accumulated in permafrost peatlands over millennia. Climate change is expected to increase peatland thaw, making this ON more susceptible to biogeochemical degradation. However, the interplay between thaw-released N and N cycling remains poorly understood. To elucidate ON composition across a thaw transition (palsa to thaw front to bog), we employed 21 T electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and nuclear magnetic resonance (NMR) spectroscopy. In addition, we performed metatranscriptomic sequencing to evaluate microbial activity changes in N cycling pathways between the palsa and bog. We observed an approximate 10-fold increase in dissolved ON and a significant rise in ammonium concentration between the palsa and thaw front. Additionally, there was a reduction in the peptide-like fraction and an increase in the aromatic fraction of dissolved ON molecules. Dissolved ON concentrations decreased by 73 % between the thaw front and bog, while expression of ammonium-producing genes was significantly higher in the bog compared to the palsa. Our findings highlight the release and rapid compositional shift of ON during thaw transitions. This underscores the need for further studies on thaw-released N to enhance models predicting N cycling and Arctic greenhouse gas emissions. • Permafrost thaw corresponds with a spike in dissolved organic N. • Permafrost thaw fronts serve as transition zones with distinct dissolved organic N. • Peptide-like organic N is limited at the point of permafrost collapse. • Upregulated N-utilizing metabolomic pathways correlated to limited organic N in bog.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.002 | 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 teacher head, 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".