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Ambio. 2002 Mar;31(2):97-101.

Nitrogen and nature.

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1
Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA. vitousek@stanford.edu

Abstract

Anthropogenic changes to the global N cycle are important in part because added N alters the composition, productivity, and other properties of many natural ecosystems substantially. Why does added N have such a large impact? Why is N in short supply in so many natural ecosystems? Processes that slow the cycling of N relative to other elements and processes that control ecosystem-level inputs and outputs of N could cause N supply to limit the dynamics of ecosystems. We discuss stoichiometric differences between terrestrial plants and other organisms, the abundance of protein-precipitating plant defenses, and the nature of the C-N bond in soil organic matter as factors that can slow N cycling. For inputs, the energetic costs of N fixation and their consequences, the supply of nutrients other than N, and preferential grazing on N-fixers all could constrain the abundance and/or activity of biological N-fixers. Together these processes drive and sustain N limitation in many natural terrestrial ecosystems.

PMID:
12078015
[Indexed for MEDLINE]
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