Size and variability of crop productivity both impacted by CO2 enrichment and warming-A case study of 4 year field experiment in a Chinese paddy

China is a key global region vulnerable to climate change; however, limited studies have focused on the combined impacts of atmospheric CO2 enrichment and warming on crop production in arable land, especially in rice paddies in China. To address this issue, a 4 year open-air field experiment during 2010-2014 was conducted to simulate the impact of climate change on crop production in a rice paddy in southeast of China. Four treatments including the ambient condition (CK), CO2 enrichment (500 ppmv, CE), warming of canopy air (2 °C above the ambient, WA), and the combined CO2 enrichment and warming (CW) were used to investigate the responses of total biomass, crop yield and harvest index. In general, different treatments significantly affected wheat and rice production. Compared to CK, CE significantly increased grain yield of rice by 8%. In contrast, the decreases of 26.2% and 10% in wheat and rice yield were observed under WA. However, there was no significant difference of wheat production between CW and CK, while rice yield and biomass were slightly decreased by a mean of 4.8% and 5.3% over 4 years, indicating the positive effect of CO2 enrichment was unable to compensate for the negative impact of warming. The interannual variations of the responses were also observed in this study. The variation of wheat yields during 4 years was much higher than that of rice yields; however, significant changes in the stability of rice biomass and harvest index were observed under CE and WA. The results indicated both stabilizing and increasing grain yield under climate change are major challenges for agriculture in developing countries.