Oecologia

, Volume 165, Issue 2, pp 511–520

Facultative nitrogen fixation by canopy legumes in a lowland tropical forest

  • Alexander R. Barron
  • Drew W. Purves
  • Lars O. Hedin
Ecosystem ecology - Original Paper

DOI: 10.1007/s00442-010-1838-3

Cite this article as:
Barron, A.R., Purves, D.W. & Hedin, L.O. Oecologia (2011) 165: 511. doi:10.1007/s00442-010-1838-3

Abstract

Symbiotic dinitrogen (N2) fixation is often invoked to explain the N richness of tropical forests as ostensibly N2-fixing trees can be a major component of the community. Such arguments assume N2 fixers are fixing N when present. However, in laboratory experiments, legumes consistently reduce N2 fixation in response to increased soil N availability. These contrasting views of N2 fixation as either obligate or facultative have drastically different implications for the N cycle of tropical forests. We tested these models by directly measuring N2-fixing root nodules and nitrogenase activity of individual canopy-dominant legume trees (Inga sp.) across several lowland forest types. Fixation was substantial in disturbed forests and some gaps but near zero in the high N soils of mature forest. Our findings suggest that canopy legumes closely regulate N2 fixation, leading to large variations in N inputs across the landscape, and low symbiotic fixation in mature forests despite abundant legumes.

Keywords

EcosystemPlant strategyGapNitrostatNitrogen limitationNitrogenSuccessionIngaNutrient cycling

Supplementary material

442_2010_1838_MOESM1_ESM.pdf (1 mb)
Supplementary material 1 (PDF 1065 kb)
442_2010_1838_MOESM2_ESM.pdf (67 kb)
Supplementary material 2 (PDF 67 kb)
442_2010_1838_MOESM3_ESM.pdf (130 kb)
Supplementary material 3 (PDF 129 kb)
442_2010_1838_MOESM4_ESM.pdf (157 kb)
Supplementary material 4 (PDF 156 kb)

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Alexander R. Barron
    • 1
  • Drew W. Purves
    • 2
  • Lars O. Hedin
    • 1
  1. 1.Department of Ecology and Evolutionary BiologyPrinceton UniversityPrincetonUSA
  2. 2.Computational Ecology and Environmental Science Group, Microsoft ResearchCambridgeUK