Basin-wide variations in Amazon forest nitrogen-cycling characteristics as inferred from plant and soil 15N:14N measurements

Autores

Nardoto, G.B., Quesada, C.A., Pati no, S., Saiz, G., Baker, T.R., Schwarz, M., Schrodt, F., Feldpausch, T.R., Domingues, T.F., Marimon, B.S., Marimon Junior, B.H., Vieira, I.C.G., Silveira, M., Bird, M.I., Phillips, O.L., Lloyd, J. and Martinelli, L.A.

Publicado en

Plant Ecology & Diversity, v. 7(1-2)

Año de publicación

2014

Afiliaciones

Faculdade UnB Planaltina, Universidade de Brasília, Brasília, Brasil
School of Geography, University of Leeds, Leeds, UK
Instituto Nacional de Pesquisas da Amazônia, Manaus, Brasil
School of Earth and Environmental Science, James Cook University, Cairns, Australia
Max Planck Institute für Biogeochemie, Jena, Deutschland
Departamento de Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brasil
Departamento de Ciências Biológicas, Universidade do Estado de Mato Grosso, Nova Xavantina, Brasil
Museu Paraense Emilio Goeldi, Belém, Brasil
Centro de Ciências Biológicas e da Natureza, Universidade Federal do Acre, Rio Branco, Brasil
Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, Brasil

Programa

CRN3

Proyecto

CRN3005

Keywords

N natural abundance, Amazon, Fabaceae, Nitrogen, nitrogen fixation, Tropical forest, Phosphorus

DOI

https://doi.org/10.1080/17550874.2013.807524
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Resumen

Background
Patterns in tropical forest nitrogen cycling are poorly understood. In particular, the extent to which leguminous trees in these forests fix nitrogen is unclear.

Aims
We aimed to determine factors that explain variation in foliar &delta15N (&delta15NF) for Amazon forest trees, and to evaluate the extent to which putatively N2-fixing Fabaceae acquire nitrogen from the atmosphere.

Methods
Upper-canopy &delta15NF values were determined for 1255 trees sampled across 65 Amazon forest plots. Along with plot inventory data, differences in &delta15NF between nodule-forming Fabaceae and other trees were used to estimate the extent of N2 fixation.

Results
&delta15NF ranged from &minus12.1&permil to +9.3&permil. Most of this variation was attributable to site-specific conditions, with extractable soil phosphorus and dry-season precipitation having strong influences, suggesting a restricted availability of nitrogen on both young and old soils and/or at low precipitation. Fabaceae constituted fewer than 10% of the sampled trees, and only 36% were expressed fixers. We estimated an average Amazon forest symbiotic fixation rate of 3 kg N ha&minus1 year&minus1.

Conclusion
Plant &delta15N indicate that low levels of nitrogen availability are only likely to influence Amazon forest function on immature or old weathered soils and/or where dry-season precipitation is low. Most Fabaceae species that are capable of nodulating do not fix nitrogen in Amazonia.