2.3 Field warming treatment
In order to realistically simulate the global warming scene, we have conducted elevated temperature experiment since 2009 through the FATE (free-air temperature enhancement) system in the rice field (Rehmani et al., 2011&2014; Dou et al., 2018; Tang et al., 2019). Warming treatment was performed by FATE with 12 ceramic infrared radiator heaters (FTE-1000-240-0-L10-Y; 1000W, 240V; 245 mm long × 60 mm wide) 1.2m above the rice canopy in each experimental plot. Angles of the heater in the horizontal and vertical directions are 45° and 30° to ensure the consistent and stable heating of the canopy and the effective area of infrared radiation is 1.5 × 1.5 × 3.1416 = 7.1m2, respectively (Figure 1). Two sensors (Model HOBO U23-001) were installed and located at the canopy height in each plot to record the temperature and humidity changes of rice canopy. The HOBO was set to record the data every 30 minutes, and HOBO Pro software was used for data processing. Field meteorological data during the test period were collected from the meteorological station (WatchDog 550) installed ~100 m away from the experimental field (Tang et al., 2019). Daytime and nighttime of rice canopy temperature were increased by 1.568 ℃ and 3.089 ℃, respectively (Supplemental figure 1). Temperature increase range and trend were in accordance with the temperature range of global warming and the rule of asymmetric warming characteristics.