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Fig. 4.12.3.
Denitrification activity in the rhizosphere soil after harvesting.
to the rhizosphere. All that could have retarded the synthesis of denitrifiers
compared with other microbial populations.
The result of our experiment did not indicate a direct plant-mediated
effect of elevated CO
2
on N
2
O fluxes or denitrification activity. However,
the positive effect on plant growth and microbial biomass has important
implications for potential feedback effects between soils and the
atmosphere. The turnover of the enlarged microbial biomass, and other
processes such as nitrification and nitrate reduction deserve further studies.
Acknowledgements
We are grateful to Lesley Swan and Olive Pauline for technical support.
We thank the Commission of the European Communities (Grant of the
Marie Curie Training Programme), and SOAEFD for financial support.
References
Canadell, J.G., Pitelka, L.F. and Ingram, J.S.I. (1996) The effects of elevated [CO
2
]
on plant-soil carbon below-ground: a summary and synthesis.
Plant and Soil
187, 391-400.
Clayton, H., McTaggart, I.P., Parker, J., Swan, L. and Smith, K.A. (1997) Nitrous
oxide emissions from fertilized grassland: a 2-year study of the effects of N
fertilizer form and environmental conditions.
Biology and Fertility of Soils
25,
252-260.
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