Changes in CH 4 and CO 2 emissions from soils under flooded conditions after being exposed to FACE (free-air CO 2 enrichment) for three years

Abstract

To evaluate the variations of CO 2 and CH 4 emissions from FACE (free-air CO 2 enrichment, F) soils three years after rice-wheat rotation FACE treatment, incubation experiments in the laboratory with laboratory and elevated CO 2 concentration (1000 μl L −1) were carried out under flooded conditions at 25°C. Results show that soil organic carbon is increased by 11% after exposure to FACE treatment for three years. The results indicate that at laboratory and elevated CO 2, the cumulative CO 2 emissions from FACE soils are 35% and 22% higher than those from the ambient soils, whereas the cumulative CH 4 emissions from FACE soils are 2.6 and 2.3 times that of ambient soils. Thus, there is a larger ratio of cumulative emissions of CH 4 to CO 2 in the soil F. The elevated CO 2 concentration during the incubation stimulates the cumulative CO 2 emission significantly, but its stimulation on CH 4 emission is not statistically significant. The results indicate that the elevated atmospheric CO 2 concentration stimulates the turnover rates of soil organic matter, with a net increase in soil organic matter content, and alters the CH 4/CO 2 ratio.