Abstract: With closed chamber and GC technique, a comparative study was conducted on the CO₂ fluxes in mire and grassland on Ruoergai plateau during the plant growth period in 2003-2005. The results showed that the mean value of the CO₂ fluxes in the three years was 203.22 mg·m^-2·h^-1 in mire and 323.03 mg·m^-2·h^-1 in grassland, with the former being only about 60% of the latter. The perennially waterlogging of mire limited the decomposition of plant residues, roots and organic substances, resulting in a lower CO₂ flux in mire than in grassland. The seasonal changes of CO₂ fluxes in mire and grassland were positively correlated with air temperature, the peak value being usually appeared in July or August, and the diurnal changes of the CO₂ fluxes were also positively correlated with air temperature, the peak value being usually appeared between 11:00 and 17:00. The CO₂ fluxes had a higher correlation with the soil temperature at the depth of 5 cm than at the depths of 10 cm and 15 cm.

Key words: exogenous 6-BA, yield, shading, rice stubble wheat