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Abstract AimNitrogen (N)‐fixing plants are an important component of global plant communities, but the drivers of N‐fixing plant diversity, especially in temperate regions, remain underexplored. Here, we examined broad‐scale patterns of N‐fixing and non‐fixing plant phylogenetic diversity (PD) and species richness (SR) across a wide portion of temperate North America, focusing on relationships with soil N and aridity. We also tested whether exotic species, with and without N‐fixing symbiosis, have fewer abiotic limitations compared with native species. LocationUSA and Puerto Rico. Time periodCurrent. Major taxa studiedVascular plants, focusing on N‐fixing groups (orders Fabales, Fagales, Rosales and Cucurbitales). MethodsWe subset National Ecological Observatory Network (NEON) plant plot data from all sites along two axes (N fixing–non‐N fixing and native–exotic), calculating plot‐level SR, PD and mean pairwise phylogenetic distance (MPD). We then used linear mixed models to investigate relationships between diversity values and key soil measurements, along with aridity, temperature and fire frequency. ResultsAridity was the sole predictor of proportional phylogenetic diversity of N fixers. The SR of N fixers still decreased marginally in arid regions, whereas native N‐fixer MPD increased with aridity, indicative of unique lineages of N fixers in the driest conditions, in contrast to native non‐N fixers. The SR of both native N fixers and non‐N fixers increased in low‐N soils. Aridity did not affect SR of exotic non‐N fixers, unlike other groups, whereas exotic N fixers showed lower MPD in increasingly high‐N soils, suggesting filtering, contrary what was found for native N fixers. Main conclusionsOur results suggest that it is not nitrogen, or any soil nutrient, that has the strongest effect on the relative success of N fixers in plant communities. Rather, aridity is the key driver, at least for native species, in line with empirical results from other biomes and increased understanding of N fixation as a key mechanism to avoid water loss.
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This content will become publicly available on October 22, 2026
Metabolic biochemical models of N 2 fixation for sulfide oxidizers, methanogens, and methanotrophs
ABSTRACT Dinitrogen (N2) fixation provides bioavailable nitrogen to the biosphere. However, in some habitats (e.g., sediments), the metabolic pathways of organisms carrying out N2fixation are unclear. We present metabolic models representing various chemotrophic N2fixers, which simulate potential pathways of electron transport and energy flow, resulting in predictions of whole-cell stoichiometries. By balancing mass, electrons, and energy for metabolic half-reactions, we quantify the electron usage for nine N2fixers. Our results demonstrate that all modeled organisms fix sufficient N2for growth. Aerobic organisms allocate more electrons to N2fixation and growth, yielding more biomass and fixing more N2, while methanogens using acetate and organisms using sulfate allocate fewer electrons. This work can be applied to investigate the depth distribution of N2fixers based on nutrient availability, complementing field measurements of biogeochemical processes and microbial communities.IMPORTANCEN2fixation is an important process in the global N cycle. Researchers have developed models for heterotrophic and photoautotrophic N2fixers, but there is a lack of modeling studies on chemoautotrophic N2fixers. Here, we built nine biochemical models for different chemoautotrophic N2fixers by combining different types of half-chemical reactions. We include three sulfide oxidizers using different electron acceptors (O2, NO3−, and Fe3+), contributing to the sulfur, nitrogen, and iron cycles in the sediment. We have two methanogens using different substrates (H2and acetate) and four methanotrophs using different electron acceptors (O2, NO3−, Fe3+, and SO42−). By modeling these methane producers and users in the sediment and their N2-fixing metabolic pathways, our work can provide insight for future carbon cycle studies. This study outlines various metabolic pathways that can facilitate N2fixation, with implications for where in the environment they might occur.
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- Award ID(s):
- 2015825
- PAR ID:
- 10647072
- Editor(s):
- Fahimipour, Ashkaan K
- Publisher / Repository:
- ASM
- Date Published:
- Journal Name:
- mSystems
- Volume:
- 10
- Issue:
- 10
- ISSN:
- 2379-5077
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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