Oecologia

, Volume 174, Issue 4, pp 1107–1116

Overlap in nitrogen sources and redistribution of nitrogen between trees and grasses in a semi-arid savanna

  • K. V. R. Priyadarshini
  • Herbert H. T. Prins
  • Steven de Bie
  • Ignas M. A. Heitkönig
  • Stephan Woodborne
  • Gerrit Gort
  • Kevin Kirkman
  • Brian Fry
  • Hans de Kroon
Physiological ecology - Original research

DOI: 10.1007/s00442-013-2848-8

Cite this article as:
Priyadarshini, K.V.R., Prins, H.H.T., de Bie, S. et al. Oecologia (2014) 174: 1107. doi:10.1007/s00442-013-2848-8

Abstract

A key question in savanna ecology is how trees and grasses coexist under N limitation. We used N stable isotopes and N content to study N source partitioning across seasons from trees and associated grasses in a semi-arid savanna. We also used 15N tracer additions to investigate possible redistribution of N by trees to grasses. Foliar stable N isotope ratio (δ15N) values were consistent with trees and grasses using mycorrhiza-supplied N in all seasons except in the wet season when they switched to microbially fixed N. The dependence of trees and grasses on mineralized soil N seemed highly unlikely based on seasonal variation in mineralization rates in the Kruger Park region. Remarkably, foliar δ15N values were similar for all three tree species differing in the potential for N fixation through nodulation. The tracer experiment showed that N was redistributed by trees to understory grasses in all seasons. Our results suggest that the redistribution of N from trees to grasses and uptake of N was independent of water redistribution. Although there is overlap of N sources between trees and grasses, dependence on biological sources of N coupled with redistribution of subsoil N by trees may contribute to the coexistence of trees and grasses in semi-arid savannas.

Keywords

Tree–grass interactions Nitrogen source Nitrogen-15 stable isotope Nitrogen-15 labelling Andover Game Reserve Nitrogen redistribution 

Supplementary material

442_2013_2848_MOESM1_ESM.docx (31 kb)
Supplementary material 1 (DOCX 30 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • K. V. R. Priyadarshini
    • 1
  • Herbert H. T. Prins
    • 1
  • Steven de Bie
    • 1
  • Ignas M. A. Heitkönig
    • 1
  • Stephan Woodborne
    • 2
  • Gerrit Gort
    • 3
  • Kevin Kirkman
    • 4
  • Brian Fry
    • 5
  • Hans de Kroon
    • 6
  1. 1.Resource Ecology GroupWageningen UniversityWageningenThe Netherlands
  2. 2.iThemba LaboratoriesWITSJohannesburgSouth Africa
  3. 3.BiometrisWageningen UniversityWageningenThe Netherlands
  4. 4.University of KwaZulu-NatalPietermaritzburgSouth Africa
  5. 5.Australian Rivers InstituteGriffith UniversityBrisbaneAustralia
  6. 6.Department of Experimental Plant Ecology, Institute for Water and Wetland ResearchRadboud UniversityNijmegenThe Netherlands

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