Soil Nitrification and Denitrification Potentials in a Wheat Field Soil as Affected by Elevated Atmospheric CO_2 and Rice Straw Incorporation

摘要

By the end of this century, atmospheric carbon dioxide (CO_2) concentration is predicted to be up to 549-970 umolmol~(-1) (IPCC 2001). Such an increase should have a direct effect on soil microbial processes, though the CO_2 concentration in soil is generally higher than that in atmosphere (Baggs et al. 2003). Soil nitrification and denitrification are the microbial processes of great significance in soil N cycling and N_2O production (Camol et al. 2002), and their rates could be modified by elevatedatmospheric CO2 concentration because of the sensitivity of related soil microbes to the changes of soil environmental factors induced by it (Barnard et al. 2005). Bagges et al. (2003) indicated that the total denitrification in grass swards was increased under elevated atmospheric CO_2, because the increased belowground C allocation provided the energy for denitrification. So far, there is no consistent information about soil microorganisms and their activity involved in nitrification, and little experimental evidence is available on the responses of soil microorganisms involved in denitrification to elevated atmospheric CO_2 (Fromin et al. 2005). In this paper, a Chinese Rice/Wheat FACE (free air carbon dioxide enrichment) system was installed o n a r ice-wheat r otation field o f E astern China t o s tudy t he e ffects o f elevated CO_2 and rice straw incorporation on soil nitrification and denitrification potentials, the numbers of soil nitrifiers and denitrifiers in a wheat field.