Biogeochemistry

, Volume 119, Issue 1–3, pp 293–306

Stable nitrogen isotope patterns of trees and soils altered by long-term nitrogen and phosphorus addition to a lowland tropical rainforest

  • Jordan R. Mayor
  • S. Joseph Wright
  • Edward A. G. Schuur
  • Mollie E. Brooks
  • Benjamin L. Turner
Article

DOI: 10.1007/s10533-014-9966-1

Cite this article as:
Mayor, J.R., Wright, S.J., Schuur, E.A.G. et al. Biogeochemistry (2014) 119: 293. doi:10.1007/s10533-014-9966-1

Abstract

Foliar nitrogen (N) isotope ratios (δ15N) are used as a proxy for N-cycling processes, including the “openness” of the N cycle and the use of distinct N sources, but there is little experimental support for such proxies in lowland tropical forest. To address this, we examined the δ15N values of soluble soil N and canopy foliage of four tree species after 13 years of factorial N and P addition to a mature lowland rainforest. We hypothesized that N addition would lead to 15N-enriched soil N forms due to fractionating losses, whereas P addition would reduce N losses as the plants and microbes adjusted their stoichiometric demands. Chronic N addition increased the concentration and δ15N value of soil nitrate and δ15N in live and senesced leaves in two of four tree species, but did not affect ammonium or dissolved organic N. Phosphorus addition significantly increased foliar δ15N in one tree species and elicited significant N × P interactions in two others due to a reduction in foliar δ15N enrichment under N and P co-addition. Isotope mixing models indicated that three of four tree species increased their use of nitrate relative to ammonium following N addition, supporting the expectation that tropical trees use the most available form of mineral N. Previous observations that anthropogenic N deposition in this tropical region have led to increasing foliar δ15N values over decadal time-scales is now mechanistically linked to greater usage of 15N-enriched nitrate.

Keywords

Ecosystem ecology Gigante Fertilization Experiment Mass balance mixing models Panama Stoichiometry 

Supplementary material

10533_2014_9966_MOESM1_ESM.pdf (491 kb)
Supplementary material 1 (PDF 491 kb)
10533_2014_9966_MOESM2_ESM.csv (4 kb)
Supplementary material 2 (CSV 4 kb)

Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Jordan R. Mayor
    • 1
    • 2
  • S. Joseph Wright
    • 1
  • Edward A. G. Schuur
    • 3
  • Mollie E. Brooks
    • 3
    • 4
  • Benjamin L. Turner
    • 1
  1. 1.Smithsonian Tropical Research InstituteBalboa, AnconRepublic of Panama
  2. 2.Department of Forest Ecology & ManagementSwedish University of Agricultural SciencesUmeåSweden
  3. 3.Department of BiologyUniversity of FloridaGainesvilleUSA
  4. 4.Institute of Evolutionary Biology and Environmental StudiesUniversity of ZurichZurichSwitzerland

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