Symbiotic dinitrogen fixation is seasonal and strongly regulated in water-limited environments

Guy Dovrat*, Efrat Sheffer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Plants, especially perennials, growing in drylands and seasonally dry ecosystems are uniquely adapted to dry conditions. Legume shrubs and trees, capable of symbiotic dinitrogen (N 2 ) fixation, often dominate in drylands. However, the strategies that allow symbiotic fixation in these ecosystems, and their influence on the nitrogen cycle, are largely unresolved. We evaluated the climatic, biogeochemical and ontogenetic factors influencing nitrogen fixation in an abundant Mediterranean legume shrub, Calicotome villosa. We measured nodulation, fixation rate, nitrogen allocation and soil biogeochemistry in three field sites over a full year. A controlled experiment evaluated differences in plant regulation of fixation as a function of soil nutrient availability and seedling and adult developmental stages. We found a strong seasonal pattern, shifting between high fixation rates during the rainy season at flowering and seed-set times to almost none in the rainless season. Under controlled conditions, plants downregulated fixation in response to soil nitrogen availability, but this response was stronger in seedlings than in adult shrubs. Finally, we did not find elevated soil nitrogen under N 2 -fixing shrubs. We conclude that seasonal nitrogen fixation, regulation of fixation, and nitrogen conservation are key adaptations influencing the dominance of dryland legumes in the community, with broader consequences on the ecosystem nitrogen cycle.

Original languageAmerican English
Pages (from-to)1866-1877
Number of pages12
JournalNew Phytologist
Volume221
Issue number4
DOIs
StatePublished - Mar 2019

Bibliographical note

Publisher Copyright:
© 2018 The Authors. New Phytologist © 2018 New Phytologist Trust

Keywords

  • Calicotome villosa
  • Mediterranean ecosystems
  • biological nitrogen fixation
  • drylands
  • leaf nitrogen content
  • leguminosae
  • symbiosis
  • water limitation

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