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1. Structure of Molecular Nitrogen Nanoclusters Containing Stabilized Nitrogen Atoms

   https://doi.org/10.1007/s10909-024-03225-8  

   Wetzel, C K; Lee, D M; Khmelenko, V V (October 2024, Journal of Low Temperature Physics)

   Impurity-helium condensates (IHCs) formed by injecting the discharge products of gaseous mixtures of helium atoms and nitrogen molecules into bulk superfluid 4He at temperature 1.5 K, were studied by X-band electron spin resonance. IHCs consists of collections of N2 nanoclusters which form aerogel-like structure inside bulk HeII. It was found that N2 nanoclusters have a two shell structure, an outer shell which contains high concentration of stabilized N atoms and an interior shell with lower concentrations of N atoms. In this paper, we have studied the dependence of the shell structure of the N2 nanoclusters which compose the IHCs by varying the ratio of nitrogen to helium in the prepared gas mixture from 0.06 to 1%. The highest local concentration of N atoms in nanoclusters (1.2 ⋅ 1021 cm−3 ) was observed in the sample prepared from the gas mixture containing the lowest nitrogen admixture (0.06%). Additionally, the evolution of nanocluster structure was studied as the samples were drained of liquid helium (T ≤ 3.5 K) and warmed beyond the point of explosive recombination (3.5 K ≤ T ≤ 6.5 K). 

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2. Loss of immiscible nitrogen from metallic melt explains Earth’s missing nitrogen

   https://doi.org/10.7185/geochemlet.1919  

   Liu, J.; Dorfman, S.M.; Lv, M.; Li, J.; Zhu, F.; Kono, Y. (July 2019, Geochemical Perspectives Letters)
3. Long-term nitrogen deposition reduces the diversity of nitrogen-fixing plants

   https://doi.org/10.1126/sciadv.adp7953  

   Moreno-García, Pablo; Montaño-Centellas, Flavia; Liu, Yu; Reyes-Mendez, Evelin Y; Jha, Rohit Raj; Guralnick, Robert P; Folk, Ryan; Waller, Donald M; Verheyen, Kris; Baeten, Lander; et al (October 2024, Science Advances)

   Biological nitrogen fixation is a fundamental part of ecosystem functioning. Anthropogenic nitrogen deposition and climate change may, however, limit the competitive advantage of nitrogen-fixing plants, leading to reduced relative diversity of nitrogen-fixing plants. Yet, assessments of changes of nitrogen-fixing plant long-term community diversity are rare. Here, we examine temporal trends in the diversity of nitrogen-fixing plants and their relationships with anthropogenic nitrogen deposition while accounting for changes in temperature and aridity. We used forest-floor vegetation resurveys of temperate forests in Europe and the United States spanning multiple decades. Nitrogen-fixer richness declined as nitrogen deposition increased over time but did not respond to changes in climate. Phylogenetic diversity also declined, as distinct lineages of N-fixers were lost between surveys, but the “winners” and “losers” among nitrogen-fixing lineages varied among study sites, suggesting that losses are context dependent. Anthropogenic nitrogen deposition reduces nitrogen-fixing plant diversity in ways that may strongly affect natural nitrogen fixation. 

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4. Symbiotic nitrogen fixation reduces belowground biomass carbon costs of nitrogen acquisition under low, but not high, nitrogen availability

   https://doi.org/10.1093/aobpla/plae051  

   Perkowski, Evan A; Terrones, Joseph; German, Hannah L; Smith, Nicholas G (October 2024, AoB PLANTS)

   Kalcsits, Lee (Ed.)

   Abstract Many plant species form symbiotic associations with nitrogen-fixing bacteria. Through this symbiosis, plants allocate photosynthate belowground to the bacteria in exchange for nitrogen fixed from the atmosphere. This symbiosis forms an important link between carbon and nitrogen cycles in many ecosystems. However, the economics of this relationship under soil nitrogen availability gradients is not well understood, as plant investment toward symbiotic nitrogen fixation tends to decrease with increasing soil nitrogen availability. Here, we used a manipulation experiment to examine how costs of nitrogen acquisition vary under a factorial combination of soil nitrogen availability and inoculation with Bradyrhizobium japonicum in Glycine max L. (Merr.). We found that inoculation decreased belowground biomass carbon costs to acquire nitrogen and increased total leaf area and total biomass, but these patterns were only observed under low fertilization and were the result of increased plant nitrogen uptake and no change in belowground carbon allocation. These results suggest that symbioses with nitrogen-fixing bacteria reduce carbon costs of nitrogen acquisition by increasing plant nitrogen uptake, but only when soil nitrogen is low, allowing individuals to increase nitrogen allocation to structures that support aboveground growth. This pattern may help explain the prevalence of plants capable of forming these associations in less fertile soils and provides useful insight into understanding the role of nutrient acquisition strategy on plant nitrogen uptake across nitrogen availability gradients. 

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5. Nitrogen wet deposition stoichiometry: the role of organic nitrogen, seasonality, and snow

   https://doi.org/10.1007/s10533-022-00966-0  

   Murray, Desneiges S.; Shattuck, Michelle D.; McDowell, William H.; Wymore, Adam S. (September 2022, Biogeochemistry)