Effects of soil warming and increased precipitation on greenhouse gas fluxes in spring maize seasons in the North China Plain.

Climatic changes, such as global warming and altered precipitation are of major environmental concern. Given that ecosystem processes are strongly regulated by temperature and water content, climate changes are expected to affect the carbon (C) and nitrogen (N) cycles, especially in agricultural systems. However, the interactive effects of soil warming and increased precipitation on greenhouse gas emissions are poorly understood, particularly in the North China Plain (NCP). Therefore, a field experiment was conducted over two spring maize seasons (May-Sept.) in 2018 and 2019. Two levels of temperature (T0: ambient temperature; T1: increase on average of 4.0 °C) combined with two levels of precipitation (W0: no artificial precipitation; W1: +30% above ambient precipitation) were carried out in the NCP. Our results showed that soil warming significantly promoted cumulative NO and CO emissions by 49% and 39%, respectively. Additionally, increased precipitation further enhanced the NO and CO emissions by 54% and 14%, respectively. This suggests that high soil temperature and water content have the capacity to stimulate microbial activities, and thus accelerate the soil C and N cycles. Soil warming increased CH uptake by 293%, but increased precipitation had no effect on CH fluxes. Overall, soil warming and increased precipitation significantly enhanced the GHG budget by 39% and 16%, respectively. This study suggests that climate warming will lead to enhanced GHG emissions in the spring maize season in the NCP, while increased precipitation in the future may further stimulate GHG emissions in a warming world.