Abstract: Global climate change, characterized by elevated atmospheric CO₂ concentration and temperature, is an important issue affecting human sustainable development. In this study, open top chamber (OTC) systems were used to simulate climate change scenarios of rising atmospheric CO₂ concentration (EC, +100 ppm) and increasing temperature (ET, +1.5 ℃). The concentration of dissolved organic carbon (DOC) in surface water and pore water, aromaticity index, biomass, yield and related driving factors of double cropping rice in Jianghan Plain were observed. The results showed that DOC concentration in soil pore water at 20 cm soil layer during the filling stage of early rice was significantly increased by 284.2% under EC treatment, compared with CK (P<0.05), and DOC aromaticity index under EC treatment was significantly decreased by 36.9% and 31.6% at booting stage and heading stage (P<0.05), respectively. DOC aromaticity index at 20 cm soil layer during the jointing stage of early rice reduced by 35.5% under EC treatment (P<0.05). Compared with EC and ET treatments, DOC aromaticity index of soil pore water at 20 cm soil depth under the combined treatment of atmospheric CO₂ concentration increasing and warming (ETEC) was significantly increased, with a range of 23.6%-51.4% during the whole growing period of paddy field (P<0.05). Both EC and ET treatments significantly increased aboveground biomass and grain yield of double cropping rice (P<0.05). This study provided scientific evidence for exploring the responses of double cropping rice to climate change and the key processes of carbon cycling in paddy ecosystems in Jianghan Plain in China.

Key words: CO₂ concentration, temperature increase, DOC concentration, aromaticity index, grain yield.