We investigated the influence of elevated CO2 and O3 on soil N cycling within the soybean growing season and across soil environments (i.e., rhizosphere and bulk soil) at the Soybean Free Air Concentration Enrichment (SoyFACE) experiment in Illinois, USA. Elevated O3 decreased soil mineral N likely through a reduction in plant material input and increased denitrification, which was evidenced by the greater abundance of the denitrifier gene nosZ. Elevated CO2 did not alter the parameters evaluated and both elevated CO2 and O3 showed no interactive effects on nitrifier and denitrifier abundance, nor on total and mineral N concentrations. These results indicate that elevated CO2 may have limited effects on N transformations in soybean agroecosystems. However, elevated O3 can lead to a decrease in soil N availability in both bulk and rhizosphere soils, and this likely also affects ecosystem productivity by reducing the mineralization rates of plant-derived residues.
Bibliographical noteFunding Information:
This research was funded by the National Science Foundation (grant # NSF-DEB 0543218 ). Additional support was provided by Award Number P42ES004699 from the National Institute of Environmental Health Sciences. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Environmental Health Sciences or the National Institutes of Health.
- Real-time quantitative PCR
- Soil N cycling