Study on carbon exchange of a maize agroecosystem during growing seasons in northeast China
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Abstract:
Based on the carbon flux data over an agroecosystem in Jinzhou field station of Shenyang Atmospheric Environment Research Institute of China Meteorological Administration, the change of CO2 flux in the growing seasons of the maize farmland ecosystem was analyzed. The average nocturnal respiration rate was 0.17, 0.18, 0.15, 0.19 mgCO2·m2·s-1 and the average daytime net carbon exchange rate was -0.43, -0.43, -0.39, -0.39 mgCO2·m2·s-1 during the growing season in 2008?2011, the interannua variability was not significant. The 8-day accumulation of net carbon exchange was U-shaped and the maximum carbon absorption intensity was -81.6, -75.2, -64.8, -59.7 gC·m-2·8d-1. The CO2 flux changed significantly in different phenological stages, and the change was the largest from jointing stage to milk ripening stage. During the four years, the ecosystem showed carbon sink in the growing season, and the proportion of carbon consumed by respiration to fixed carbon in photosynthesis was not different. The cumulative carbon exchange capacity was -513.37, -489.86, -482.06, -398.67 gC·m-2, respectively. There was a linear correlation between the nocturnal ecosystem respiration and EVIs×Ws (EVIs and Ws are the functions of enhanced vegetation index and land surface water index on photosynthesis, respectively) (R2=0.73), and L-T equation (R2=0.39) was satisfied with land surface temperature. The results showed that the respiration model based on remote sensing data was effective in estimating ecosystem respiration (R2=0.92), which played an important role in carbon budget assessment of Maize Farmland Ecosystem in Northeast China.
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