Global Carbon Investment in Terrestrial Biological Nitrogen Fixation

Abstract Biological nitrogen (N) fixation (BNF) provides the N needed to produce proteins and other biological building blocks, helping feed humanity and mitigate climate change. Due to its high energetic cost compared to other forms of N acquisition, biotic investment in BNF indicates N limitation. Globally gridded BNF flux data provide an opportunity to determine the energetic investment in BNF across ecosystems, which would help reconcile conflicting indicators of N limitation. Here, we use a new BNF synthesis to quantify the relative importance of BNF in different N‐fixing niches, in different biomes, and across the globe by calculating the fraction of net primary productivity (NPP) invested in BNF and the fraction of plant N acquisition provided by BNF. Larger fractions of non‐agricultural NPP were invested in BNF in less‐productive, higher‐latitude biomes. This pattern was driven by biocrusts and mosses. Similarly, non‐agricultural symbiotic N‐fixing plants invested relatively more of their own NPP in BNF in less‐productive, higher‐latitude biomes. This symbiotic plant pattern was driven by shrubs and herbs, overriding the opposite pattern in trees. Symbiotic plants also acquired a higher fraction of their N from BNF at higher latitudes and in less productive biomes. Investments in symbiotic BNF were 10× higher in agricultural (2.9% of NPP) versus natural (0.29%) biomes, providing 26% versus 3.1% of ecosystem‐scale plant N acquisition. These results support the paradigm of strong N limitation at higher latitudes, help understand the rarity of N‐fixing trees at higher latitudes, underscore the dominance of human activity, and inform terrestrial biosphere models.

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Publication Details

Journal
Global Biogeochemical Cycles
Published
2026-07-30
DOI
https://doi.org/10.1029/2026gb009098
Primary Topic
Photosynthetic Processes and Mechanisms
Type
article
Field-Weighted Citation Impact
0.00

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article

Global Carbon Investment in Terrestrial Biological Nitrogen Fixation

Johannes Piipponen, Jennifer L. Funk, Duncan N. L. Menge, Cory C. Cleveland et al.
Global Biogeochemical Cycles
Photosynthetic Processes and Mechanisms
article

Global Carbon Investment in Terrestrial Biological Nitrogen Fixation

Johannes Piipponen, Jennifer L. Funk, Duncan N. L. Menge, Cory C. Cleveland, Verity Salmon, Steven S. Perakis, Maga Gei, Michael J. Gundale, Mark B. Peoples, Bettina Weber, Sasha C. Reed, Sarah Jovan, Katherine A. Dynarski, Amelia A. Wolf, Nina Wurzburger, Sarah A. Batterman, Kevin L. Griffin, Sian Kou‐Giesbrecht, Fiona M. Soper, Emilio Rodríguez‐Caballero, Timothy E. Crews, D. F. Herridge, Anika P. Staccone, Benton N. Taylor, Carla R. Reis Ely
article en

Abstract

Abstract Biological nitrogen (N) fixation (BNF) provides the N needed to produce proteins and other biological building blocks, helping feed humanity and mitigate climate change. Due to its high energetic cost compared to other forms of N acquisition, biotic investment in BNF indicates N limitation. Globally gridded BNF flux data provide an opportunity to determine the energetic investment in BNF across ecosystems, which would help reconcile conflicting indicators of N limitation. Here, we use a new BNF synthesis to quantify the relative importance of BNF in different N‐fixing niches, in different biomes, and across the globe by calculating the fraction of net primary productivity (NPP) invested in BNF and the fraction of plant N acquisition provided by BNF. Larger fractions of non‐agricultural NPP were invested in BNF in less‐productive, higher‐latitude biomes. This pattern was driven by biocrusts and mosses. Similarly, non‐agricultural symbiotic N‐fixing plants invested relatively more of their own NPP in BNF in less‐productive, higher‐latitude biomes. This symbiotic plant pattern was driven by shrubs and herbs, overriding the opposite pattern in trees. Symbiotic plants also acquired a higher fraction of their N from BNF at higher latitudes and in less productive biomes. Investments in symbiotic BNF were 10× higher in agricultural (2.9% of NPP) versus natural (0.29%) biomes, providing 26% versus 3.1% of ecosystem‐scale plant N acquisition. These results support the paradigm of strong N limitation at higher latitudes, help understand the rarity of N‐fixing trees at higher latitudes, underscore the dominance of human activity, and inform terrestrial biosphere models.

Global Biogeochemical CyclesVol. 40(8)
Oak Ridge Associated Universities (US), Smithsonian Tropical Research Institute (PA), United States Geological Survey (US), Oak Ridge National Laboratory (US), Commonwealth Scientific and Industrial Research Organisation (AU), University of Leeds (GB), Oregon State University (US), US Forest Service (US), Lamont-Doherty Earth Observatory (US), University of Georgia (US), Simon Fraser University (CA), Minnesota Medical Association (US), Earth Island Institute (US), Swedish University of Agricultural Sciences (SE), Cary Institute of Ecosystem Studies (US), Graz University of Technology (AT), The Land Institute (US), Evolutionary Genomics (United States) (US), Max Planck Institute for Chemistry (DE), Mill Valley Public Library (US), Agriculture and Food (AU), Oak Ridge Institute for Science and Education, Forest and Rangeland Ecosystem Science Center, Southwest Biological Science Center, McGill University (CA), University of Almería (ES), University of Montana (US), Columbia University (US), University of California, Davis (US), The University of Texas at Austin (US), University of New England (AU), Aalto University (FI)
National Science Foundation, U.S. Geological Survey, Natural Environment Research Council, European Research Council
Openalex Percentile: Top 15%
Photosynthetic Processes and Mechanisms
DOIOpen Access PDFOpenAlex
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