Abstract: Stationary observation of CO₂ emission and fixation in paddy ecosystem was carried out during the late rice growing season,using the closed static chamber technique in a red soil hilly region.It was found that CO₂ flux varied with the weather condition（sunny,rainny,cloudy） from day to day.The daily net CO₂ fixation fluctuated sharply during the season,peaking up to 10.35 g·m^-2·d^-1,and dropping down below zero,-0.92 g·m^-2·d^-1,at the maturing stage of the crop.The CO₂ accumulative emission from the paddy ecosystem reached 20.4 t·hm^-2 and from the soil through respiration 6.3 t·hm^-2.The former was in an extreme power function relationship with the crop biomass.During the entire growing season of late rice,the paddy ecosystem fixed 3.85 to 4.00 t·hm^-2 C from the atmosphere.

Key words: paddy ecosystem of late rice, red earth hilly region, CO₂ flux, CO₂ fixation