Using indirect methods to constrain symbiotic nitrogen fixation rates : a case study from an Amazonian rain forest
Cleveland, Cory C.
Houlton, Benjamin Z.
Reed, Sasha C.
Townsend, Alan R.
MetadataShow full item record
KeywordAmazon Basin; Ecosystem modeling; Mass balance; Nitrogen fixation; Nutrient cycling; Rondonia; Tropical forest
Human activities have profoundly altered the global nitrogen (N) cycle. Increases in anthropogenic N have had multiple effects on the atmosphere, on terrestrial, freshwater and marine ecosystems, and even on human health. Unfortunately, methodological limitations challenge our ability to directly measure natural N inputs via biological N fixation (BNF)—the largest natural source of new N to ecosystems. This confounds efforts to quantify the extent of anthropogenic perturbation to the N cycle. To address this gap, we used a pair of indirect methods—analytical modeling and N balance—to generate independent estimates of BNF in a presumed hotspot of N fixation, a tropical rain forest site in central Rondônia in the Brazilian Amazon Basin. Our objectives were to attempt to constrain symbiotic N fixation rates in this site using indirect methods, and to assess strengths and weaknesses of this approach by looking for areas of convergence and disagreement between the estimates. This approach yielded two remarkably similar estimates of N fixation. However, when compared to a previously published bottom-up estimate, our analysis indicated much lower N inputs via symbiotic BNF in the Rondônia site than has been suggested for the tropics as a whole. This discrepancy may reflect errors associated with extrapolating bottom-up fluxes from plot-scale measures, those resulting from the indirect analyses, and/or the relatively low abundance of legumes at the Rondônia site. While indirect methods have some limitations, we suggest that until the technological challenges of directly measuring N fixation are overcome, integrated approaches that employ a combination of model-generated and empirically-derived data offer a promising way of constraining N inputs via BNF in natural ecosystems.
© The Authors 2009. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License. The definitive version was published in Biogeochemistry 99 (2010): 1-13, doi:10.1007/s10533-009-9392-y.
The following license files are associated with this item:
Except where otherwise noted, this item's license is described as Attribution-NonCommercial 3.0 Unported
Showing items related by title, author, creator and subject.
Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean Moutin, T.; Karl, David M.; Duhamel, Solange; Rimmelin, P.; Raimbault, P.; Van Mooy, Benjamin A. S.; Claustre, H. (Copernicus Publications on behalf of the European Geosciences Union, 2008-01-29)Due to the low atmospheric input of phosphate into the open ocean, it is one of the key nutrients that could ultimately control primary production and carbon export into the deep ocean. The observed trend over the last 20 ...
Iron availability limits the ocean nitrogen inventory stabilizing feedbacks between marine denitrification and nitrogen fixation Moore, J. Keith; Doney, Scott C. (American Geophysical Union, 2007-04-04)Recent upward revisions in key sink/source terms for fixed nitrogen (N) in the oceans imply a short residence time and strong negative feedbacks involving denitrification and N fixation to prevent large swings in the ocean ...
Sohm, Jill A.; Hilton, Jason A.; Noble, Abigail E.; Zehr, Jonathan P.; Saito, Mak A.; Webb, Eric A. (American Geophysical Union, 2011-08-27)Dinitrogen (N2) fixation is recognized as an important input of new nitrogen (N) to the open ocean gyres, contributing to the export of organic matter from surface waters. However, very little N2-fixation research has ...