Abstract:

Carbon dioxide (CO2), ethane (CH4) and nitrous oxide (N2O) are generally thought as the main greenhouse gases, playing an important role in climate change. It is considered that the observation of CO2 flux over paddy ecosystem is the main content of the research on agricultural sources of greenhouse gas monitoring and control technology. Based on eddy covariance system, the canopy flux of CO2, latent heat and sensible heat over paddy ecosystem at agrometeorological experimental station of Jingzhou were measured during May 2010 and September 2010 to analyze the variations and its influence factors. The results indicated that diurnal variations of carbon dioxide flux, latent heat and sensible heat showed a unipeak model, and the maximum values appeared around at 14〖DK〗∶00 in general, but the amplitude was different during rice transplanting, tillering, jointingheading, milky stage. This had a significant correlation with the diurnal variation of total solar radiation and the leaf area index (LAI) during each growth stage. The one hand, CO2 emission flux of soil and crop respiration has a correlation with temperature. On the other hand, it is related to irrigation and crop conditions. Plants absorb and assimilate CO2 by photosynthesis during the day, so CO2 absorption flux has a significant correlation with LAI and photosynthetically active radiation (PAR). Correlation coefficients between canopy CO2 flux and meteorological factors (air temperature, soil temperature in 5 cm, PAR exposure per hour, latent heat flux, sensible heat flux) were significant at 0.01 level (P<0.01) during rice stages. The correlation coefficients between canopy CO2 flux and PAR exposure per hour were much bigger during rice tillering, jointingheading, milky stage than other periods, which could be used to estimate canopy CO2 flux by MichaelisMenten model