Optimized rice adaptations in response to heat and cold stress under climate change in southern China

Climate change has drastically affected rice production and imperiled food security. Adaptations are imperative in response to future climate change. Joint adaptations in cultivation and stress resistance were optimized under representative concentration pathways 4.5 (RCP4.5) and 8.5 (RCP8.5) scenarios, in a new perspective of minimizing heat stress and cold stress for double-season rice in southern China. In general, earlier sowing date and shorter duration were projected for early rice, while later sowing date and longer duration were expected for late rice in near term and long term of twenty-first century. Regional demonstrations signaled that south of the Yangtze River and South China would be exposed to a respective advancement of 16.6 and 8.9 days in sowing date, a decrement of 193.6 and 477.3 °C·day in duration for early rice in 2071–2100 under RCP8.5 relative to 2021–2050 under RCP4.5. Regarding late rice, a postponement of 4.7 and 12.7 days in sowing date, and an increment of 896.9 and 237.0 °C·day in duration were likely to be exhibited in south of the Yangtze River and South China, respectively. Cold stress could be reduced to a small intensity but heat stress for early rice would be getting severer, given optimal cultivations were considered. To maintain the intensity of heat stress in 1991–2020, the threshold for heat stress would be boosted to 37.3 °C and 36.6 °C in south of the Yangtze River and South China in 2071–2100 under RCP8.5, respectively. The results highlighted that south of the Yangtze River should adapt to much earlier planting, less shorter duration, and higher heat resistance for early rice, as well as less later planting and much longer duration for late rice, in contrast with South China.