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Ecosystems

, Volume 9, Issue 8, pp 1257–1265 | Cite as

Inhibition of Nitrification Alters Carbon Turnover in the Patagonian Steppe

  • Amy T. Austin
  • Osvaldo E. Sala
  • Robert B. Jackson
Article

Abstract

Human activities are altering biodiversity and the nitrogen (N) cycle, affecting terrestrial carbon (C) cycling globally. Only a few specialized bacteria carry out nitrification—the transformation of ammonium (NH 4 + ) to nitrate (NO 3 ), in terrestrial ecosystems, which determines the form and mobility of inorganic N in soils. However, the control of nitrification on C cycling in natural ecosystems is poorly understood. In an ecosystem experiment in the Patagonian steppe, we inhibited autotrophic nitrification and measured its effects on C and N cycling. Decreased net nitrification increased total mineral N and NH 4 + and reduced NO 3 in the soil. Plant cover (P < 0.05) and decomposition (P < 0.0001) decreased with inhibition of nitrification, in spite of increases in NH 4 + availability. There were significant changes in the natural abundance of δ15N in the dominant vegetation when nitrification was inhibited suggesting that a switch occurred in the form of N (from NO 3 to NH 4 + ) taken up by plants. Results from a controlled-condition experiment supported the field results by showing that the dominant plant species of the Patagonian steppe have a marked preference for nitrate. Our results indicate that nitrifying bacteria exert a major control on ecosystem functioning, and that the inhibition of nitrification results in significant alteration of the C cycle. The interactions between the C and N cycles suggest that rates of C cycling are affected not just by the amount of available N, but also by the relative availability for plant uptake of NH 4 + and NO 3 .

Keywords

carbon cycling nitrification inhibition nitrogen mineralization semi-arid ecosystem ammonium nitrate 15N stable isotope Patagonian steppe Argentina nitrapyrin 

Notes

Acknowledgements

The research was supported by a grant from the Inter-American Institute for Global Change Research (CRN-012), the Fondo para la Investigación Científica y Tecnológica (FONCyT), and the University of Buenos Aires; additional institutional support was provided by IFEVA. A.T.A. was supported by a National Science Foundation International Research Fellowship and a grant from Fundación Antorchas of Argentina. We thank Jerry Huffman of DowElanco for his expertise and the donation of N-serve 24E for use in our experiment. J. Vrsalovic, L. Vivanco, P. Flombaum, N. Sala, J. Rotundo, R. Pera, P. Roset, and S. Veron provided field assistance, and M. Tagliazucchi, A. Sala, I. Montoya, and W. Cook provided laboratory assistance. L. Gherardi assisted with the greenhouse experiment. T. Loynachan, D. Mengel, G. Malzer, A. Mosier and P. Vitousek supplied us with information about nitrification inhibitors. We are especially grateful to R. Sanchez, J. Stark, and W. Schlesinger for their comments on the experiment.

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Copyright information

© Springer Science+Business Media, Inc. 2007

Authors and Affiliations

  • Amy T. Austin
    • 1
  • Osvaldo E. Sala
    • 1
  • Robert B. Jackson
    • 2
  1. 1.Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA)Facultad de Agronomía, CONICET and Universidad de Buenos AiresBuenos AiresArgentina
  2. 2.Department of Biology and Nicholas School of the EnvironmentDuke UniversityDurhamUSA

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