Farmland ecosystem is an important part of the terrestrial ecosystem, accounting for 10.5% of the global land area, its carbon dioxide flux accounted for 21% - 25% of the man-made greenhouse gas emissions, and therefore, measuring the soil co₂ efflux is crucial for accurately evaluating the effects of soil management practices on global warming and carbon cycling.

With the supervision of Professor Fang Chen, Dr. Yi Liu of Wuhan Botanical Garden examined the diurnal and seasonal soil carbon dioxide (co₂) fluxes pattern in rice paddy fields in central China and assessed the role of floodwater in controlling the emissions of co₂ from soil and floodwater in intermittently draining rice paddy soil.

Results showed that seasonal variations, diurnal patterns, conversion processes of draining and flooding cycles, and temperature influenced soil co₂ fluxes from paddy fields mutually. From the comparison of soil co₂ fluxes under draining and flooding conditions we conclude that: the net effluxes of co₂ from the paddy soil were lower when the paddy was flooding than when it was draining. Under draining conditions, co₂ flux was positive and settled around 2-4 µmol.m-2.s-1throughout the night, despite falling temperatures. After sunrise, co₂ fluxes remained positive and increased with temperature, reaching a peak at 2 pm (14 : 00 h) before falling again as temperatures declined. Under flooding conditions, fluxes of co₂ were lower because the diffusivity and biological activity of the topsoil was substantially reduced by floodwater. The results provide the basis of scientific data for the global carbon balance budget and global co₂ potential effect evaluation.

The study was supported by the National Natural Science Foundation of China (31100386), and the Cooperated Program with International Plant Nutrition Institute (IPNI- HB-33). Relevant results were published in PLoS One entitled “Carbon dioxide flux from rice paddy soils in central China: Effects of intermittent flooding and draining cycles”.