Temperature variations and rice yields in China: historical contributions and future trends

Abstract

Temperature is the principal factor that determines rice growth, development and ultimately grain yield. In this study, normal growing-degree-days (NGDD) and killing growing-degree-days (KGDD) were used to capture the different effects of normal and extreme temperatures on rice yields, respectively. Based on these indexes, we assessed the contributions of temperature variations to county-level rice yields across China during the historical period (1980–2008), and estimated the potential exposure of rice to extreme temperature stress in the near future (2021–2050). The results showed that historical temperature variations had measurable impacts on rice yields with a distinct spatial pattern: for different regions, such variations had contributed much to the increased rice yields in Northeast China (Region I) (0.59 % yield year⁻¹) and some portions of the Yunnan-Guizhou Plateau (Region II) (0.34 % yield year⁻¹), but seriously hindered the improvements of rice yields in the Sichuan Basin (SB) (−0.29 % yield year⁻¹) and the southern cultivation areas (Region IV) (−0.17 % yield year⁻¹); for the entire country, half of the contributions were positive and the other half were negative, resulting in a balance pattern with an average of 0.01 % yield year⁻¹. Under the RCP8.5 scenario, climate warming during 2021–2050 would substantially reduce cold stress but increase heat stress in the rice planting areas across China. For the future period, Region I, II and eastern China would be continually exposed to more severe cold stress than the other regions; Region III (including SB and the mid-lower reaches of Yangtze River (MLRYR)) would be the hot spot of heat stress.