CO2 flux and impact factors in winter wheat field ecosystem Impact of climate change on winter wheat production in the Hebei Plain Comprehensive analysis of emissions and global warming effects of greenhouse gases in winter-wheat fields in the high-yield agro-region of North China Plain Ozone stress on light response capacity and on the utilization of PSⅡ absorbed light energy of winter-wheat Effects of long-term ozone exposure on the photosynthesis capacity of grain pericarp and grain-filling of winter-wheat