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1. Temporal variability of nitrogen fixation and particulate nitrogen export at Station ALOHA: Temporal variability of nitrogen fixation and particulate nitrogen

   https://doi.org/10.1002/lno.10386  

   Böttjer, Daniela ; Dore, John E. ; Karl, David M. ; Letelier, Ricardo M. ; Mahaffey, Claire ; Wilson, Samuel T. ; Zehr, Jonathan ; Church, Matthew J. ( January 2017 , Limnology and Oceanography)
2. Tree symbioses sustain nitrogen fixation despite excess nitrogen supply

   https://doi.org/10.1002/ecm.1562  

   Menge, Duncan N. L. ; Wolf, Amelia A. ; Funk, Jennifer L. ; Perakis, Steven S. ; Akana, Palani R. ; Arkebauer, Rachel ; Bytnerowicz, Thomas A. ; Carreras Pereira, K. A. ; Huddell, Alexandra M. ; Kou‐Giesbrecht, Sian ; et al ( January 2023 , Ecological Monographs)

   Symbiotic nitrogen fixation (SNF) is a key ecological process whose impact depends on the strategy of SNF regulation—the degree to which rates of SNF change in response to limitation by N versus other resources. SNF that is obligate or exhibits incomplete downregulation can result in excess N fixation, whereas a facultative SNF strategy does not. We hypothesized that tree‐based SNF strategies differed by latitude (tropical vs. temperate) and symbiotic type (actinorhizal vs. rhizobial). Specifically, we expected tropical rhizobial symbioses to display strongly facultative SNF as an explanation of their success in low‐latitude forests. In this study we used¹⁵N isotope dilution field experiments in New York, Oregon, and Hawaii to determine SNF strategies in six N‐fixing tree symbioses. Nitrogen fertilization with +10 and +15 g N m⁻² year⁻¹for 4–5 years alleviated N limitation in all taxa, paving the way to determine SNF strategies. Contrary to our hypothesis, all six of the symbioses we studied sustained SNF even at high N.Robinia pseudoacacia(temperate rhizobial) fixed 91% of its N (%N_dfa) in controls, compared to 64% and 59% in the +10 and +15 g N m⁻² year⁻¹treatments. ForAlnus rubra(temperate actinorhizal), %N_dfawas 95%, 70%, and 60%. For the tropical species, %N_dfawas 86%, 80%, and 82% forGliricidia sepium(rhizobial); 79%, 69%, and 67% forCasuarina equisetifolia(actinorhizal); 91%, 42%, and 67% forAcacia koa(rhizobial); and 60%, 51%, and 19% forMorella faya(actinorhizal). Fertilization with phosphorus did not stimulate tree growth or SNF. These results suggest that the latitudinal abundance distribution of N‐fixing trees is not caused by a shift in SNF strategy. They also help explain the excess N in many forests where N fixers are common.

    

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3. Preliminary estimates of the contribution of Arctic nitrogen fixation to the global nitrogen budget: Arctic nitrogen fixation

   https://doi.org/10.1002/lol2.10046  

   Sipler, Rachel E. ; Gong, Donglai ; Baer, Steven E. ; Sanderson, Marta P. ; Roberts, Quinn N. ; Mulholland, Margaret R. ; Bronk, Deborah A. ( October 2017 , Limnology and Oceanography Letters)
4. Soil Nitrogen Supply Exerts Largest Influence on Leaf Nitrogen in Environments with the Greatest Leaf Nitrogen Demand

   https://doi.org/10.1111/ele.70015  

   Cheaib, Alissar ; Waring, Elizabeth_F ; McNellis, Risa ; Perkowski, Evan_A ; Martina, Jason_P ; Seabloom, Eric_W ; Borer, Elizabeth_T ; Wilfahrt, Peter_A ; Dong, Ning ; Prentice, Iain_Colin ; et al ( January 2025 , Ecology Letters)

   Accurately representing the relationships between nitrogen supply and photosynthesis is crucial for reliably predicting carbon–nitrogen cycle coupling in Earth System Models (ESMs). Most ESMs assume positive correlations amongst soil nitrogen supply, leaf nitrogen content, and photosynthetic capacity. However, leaf photosynthetic nitrogen demand may influence the leaf nitrogen response to soil nitrogen supply; thus, responses to nitrogen supply are expected to be the largest in environments where demand is the greatest. Using a nutrient addition experiment replicated across 26 sites spanning four continents, we demonstrated that climate variables were stronger predictors of leaf nitrogen content than soil nutrient supply. Leaf nitrogen increased more strongly with soil nitrogen supply in regions with the highest theoretical leaf nitrogen demand, increasing more in colder and drier environments than warmer and wetter environments. Thus, leaf nitrogen responses to nitrogen supply are primarily influenced by climatic gradients in photosynthetic nitrogen demand, an insight that could improve ESM predictions.

    

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5. Nitrogen-doped CVD diamond: Nitrogen concentration, color and internal stress

   https://doi.org/10.1016/j.diamond.2020.107794  

   Zaitsev, A.M. ; Kazuchits, N.M. ; Kazuchits, V.N. ; Moe, K.S. ; Rusetsky, M.S. ; Korolik, O.V. ; Kitajima, Kouki ; Butler, J.E. ; Wang, W. ( May 2020 , Diamond and Related Materials)

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