Responses of a rice-wheat rotation agroecosystem to experimental warming

Climate change is likely to affect agroecosystems in many ways. This study was performed to investigate how a rice-winter wheat rotation agroecosystem in southeast China would respond to global warming. By using an infrared heater system, the soil surface temperature was maintained about 1.5 A degrees C above ambient milieu over 3 years. In the third growing season (2009-2010), the evapotranspiration (ET) rate, crop production, soil respiration, and soil carbon pool were monitored. The ET rate was 23 % higher in the warmed plot as compared to the control plot during the rice paddy growing season, and the rice grain yield was 16.3 % lower, but there was no significant difference in these parameters between the plots during the winter wheat-growing season. The phenology of the winter wheat shifted under experimental warming, and ET may decrease late in the winter wheat-growing season. Experimental warming significantly enhanced soil respiration, with mean annual soil respiration rates of 2.57 +/- A 0.17 and 1.96 +/- A 0.06 mu mol CO2 m(-2) s(-1) observed in the warmed and control plots, respectively. After 3 years of warming, a significant decrease in the total organic carbon was observed, but only in the surface soil (0-5 cm). Warming also stimulated the belowground biomass, which may have compensated for any heat-induced loss of soil organic carbon. Paddy rice seemed to be more vulnerable to warming than winter wheat in terms of water-use efficiency and grain production.