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 - .
Original language | English (US) |
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Pages (from-to) | 1257-1265 |
Number of pages | 9 |
Journal | Ecosystems |
Volume | 9 |
Issue number | 8 |
DOIs | |
State | Published - Dec 2006 |
Externally published | Yes |
Keywords
- Ammonium
- Argentina
- Carbon cycling
- N stable isotope
- Nitrapyrin
- Nitrate
- Nitrification inhibition
- Nitrogen mineralization
- Patagonian steppe
- Semi-arid ecosystem
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Environmental Chemistry
- Ecology