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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
Baker, Timothy R.
Feldpausch, Ted R.
Marimon, Beatriz Schwantes
Marimon Júnior, Ben Hur
Guimarães Vieira, Ima Cèlia
Bird, Michael I.
Phillips, Oliver L.
Martinelli, Luiz Antônio
|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.|
|Appears in Collections:||Artigos|
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