New insights into moss nitrogen fixation and associated N2 fixer communities from a 1000 Km latitudinal transect in Eastern Canada. 
Bibliographic record
Abstract
Moss-associated cyanobacteria nitrogen (N2-) fixation can support moss growth and constitutes a major source of new N in boreal forest ecosystems. Moss-colonizing cyanobacterial biomass and their N2-fixation are usually considered linearly correlated. However, recent evidence showed that cyanobacterial biomass and N2-fixation can be disconnected, hinting that they might be affected by the different environmental and ecological drivers. These drivers are often studied using manipulative experiments (e.g. fertilization, incubation) and remain to be validated with complementary work in observational studies. Cyanobacteria are considered the major actors of N fixation. However, the nature and diversity of active microbial communities associated with feather mosses are still unclear and the effects of the environment on these community are vague. Using random forest, spearman correlations and linear mixed-effects models, we studied the main drivers of cyanobacterial biomass and N2-fixation of two dominant feather moss species collected over three years on a 1000-km latitudinal transect in the eastern Canadian boreal forest. Using RNA-based amplicon sequencing of the 16S rRNA and nifH genes we explored the active bacterial communities along this transect and along the moss shoot. We report that temperature, precipitation, and phosphorus were the main drivers of moss cyanobacterial biomass and that temperature, molybdenum and vanadium were the main drivers of N2-fixation. Cyanobacteria accounted for 33% of global bacterial communities and 65% of diazotrophic communities, respectively. Several cyanobacterial and proteobacterial methanotrophic genera, including poorly known taxa found for the first time on boreal feather mosses, were actively contributing to N2-fixation. We showed that bacteria were heterogeneously distributed along the moss shoot, with phototrophs being dominant in the apical part and methanotrophs being dominant in the basal part. Finally data showed that climate (temperature, precipitation), environmental variables (moss species, month, tree density) and nutrients (nitrogen, phosphorus, molybdenum, vanadium, iron) strongly shape the global and diazotrophic bacterial communities and create ecological niches on the moss shoot. This work provides new insights into the feather moss microbiome and its ecological and biogeochemical functions. Our data provides evidence that the feather moss microbiome plays crucial roles in supporting moss growth, health, and decomposition, as well as in the boreal forest carbon and nitrogen cycles. Finally, this study highlights the strong effects of climate and nutrients in shaping feather moss microbiome and its activity (i.e., N2 fixation). This work will help better predict the impacts of global change on this symbiosis and on nitrogen input in boreal forest ecosystems.
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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 | 0.002 | 0.004 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".