Negative effects of nitrogen override positive effects of phosphorus on grassland legumes worldwide

Pedro M. Tognetti, Suzanne M. Prober, Selene Báez, Enrique J. Chaneton, Jennifer Firn, Anita C. Risch, Martin Schuetz, Anna K. Simonsen, Laura Yahdjian, Elizabeth T. Borer, Eric W. Seabloom, Carlos Alberto Arnillas, Jonathan D. Bakker, Cynthia S. Brown, Marc W. Cadotte, Maria C. Caldeira, Pedro Daleo, John M. Dwyer, Philip A. Fay, Laureano A. GherardiNicole Hagenah, Yann Hautier, Kimberly J. Komatsu, Rebecca L. McCulley, Jodi N. Price, Rachel J. Standish, Carly J. Stevens, Peter D Wragg, Mahesh Sankaran

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


Anthropogenic nutrient enrichment is driving global biodiversity decline and modifying ecosystem functions. Theory suggests that plant functional types that fix atmospheric nitrogen have a competitive advantage in nitrogen-poor soils, but lose this advantage with increasing nitrogen supply. By contrast, the addition of phosphorus, potassium, and other nutrients may benefit such species in lownutrient environments by enhancing their nitrogen-fixing capacity. We present a global-scale experiment confirming these predictions for nitrogen-fixing legumes (Fabaceae) across 45 grasslands on six continents. Nitrogen addition reduced legume cover, richness, and biomass, particularly in nitrogen-poor soils, while cover of non-nitrogenfixing plants increased. The addition of phosphorous, potassium, and other nutrients enhanced legume abundance, but did not mitigate the negative effects of nitrogen addition. Increasing nitrogen supply thus has the potential to decrease the diversity and abundance of grassland legumes worldwide regardless of the availability of other nutrients, with consequences for biodiversity, food webs, ecosystem resilience, and genetic improvement of protein-rich agricultural plant species.

Original languageEnglish (US)
Article numbere2023718118
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number28
StatePublished - Jul 13 2021

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. This work was generated using data from the Nutrient Network ( experiment, funded at the site scale by individual researchers. Coordination and data management were supported by funding to E.T.B. and E.W.S. from the NSF Research Coordination Network (NSF-DEB-1042132) and Long-Term Ecological Research (NSF-DEB-1234162 to Cedar Creek Long-Term Ecological Research) programs, and the Institute on the Environment (DG-0001-13). We also thank the Minnesota Supercomputer Institute for hosting project data and the Institute of the Environment for hosting Network meetings. P.M.T. was supported by an Argentine Research Council fellowship (Consejo Nacional de Investigaciones Científicas y Técnicas) and the Australian Endeavour Programme.

Publisher Copyright:
© 2021 National Academy of Sciences. All rights reserved.


  • Eutrophication
  • Fabaceae
  • Legumes
  • N deposition
  • Nutrient Network


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