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Title: Basin-wide variations in Amazon forest nitrogen-cycling characteristics as inferred from plant and soil 15N:14N measurements
Authors: Nardoto, G. B.
Quesada, Carlos Alberto
Patiño, Sandra
Saiz, Gustavo
Baker, Timothy R.
Schwarz, Michael
Schrodt, Franziska
Feldpausch, Ted R.
null, Tomas
Marimon, Beatriz Schwantes
Marimon Júnior, Ben Hur
Guimarães Vieira, Ima Cèlia
Silveira, Marcos
Bird, Michael I.
Phillips, Oliver L.
Lloyd, Jon
Martinelli, Luiz Antônio
Issue Date: 2014
metadata.dc.publisher.journal: Plant Ecology and Diversity
metadata.dc.relation.ispartof: Volume 7, Número 1-2, Pags. 173-187
Abstract: 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 δ15N (δ15NF) for Amazon forest trees, and to evaluate the extent to which putatively N2-fixing Fabaceae acquire nitrogen from the atmosphere. Methods: Upper-canopy δ15NF values were determined for 1255 trees sampled across 65 Amazon forest plots. Along with plot inventory data, differences in δ15NF between nodule-forming Fabaceae and other trees were used to estimate the extent of N2 fixation. Results: δ15NF ranged from -12.1‰ to +9.3‰. 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-1 year-1. Conclusion: Plant δ15N 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. © 2014 Copyright 2013 Botanical Society of Scotland and Taylor & Francis.
metadata.dc.identifier.doi: 10.1080/17550874.2013.807524
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