The relative contribution of climate and cultivar renewal to shaping rice yields in China since 1981

Abstract

Rice is one of China’s most important staple food crops, where the yields are strongly influenced by climate and rice variety renewal. Using high-quality weather data, rice growth, and agricultural practice data, the contribution of climatic variation on rice yield increases was analyzed from 1981 to 2009 in Wuchang, Northeast China. In this region, the annual mean surface air temperature increased by 0.6 °C/decade, and the accumulated temperature (>10 °C) increased by 120.1 °C/decade from 1981 to 2009, mainly related to global warming. During the same period, rice yields increased by 2,095 kg/ha*decade. To quantify the contribution of climate change to rice yield increases, a “climate similarity index” was devised, where the most important climate parameters for rice growth were compared among years. If the rice variety was changed between 2 years, while the climate conditions were similar, any yield change would be attributed to a rice variety renewal effect. Conversely, changes in rice yields that were not associated with variety changes were attributed to climate change. Our results showed that over the analyzed period, the influence of climate on yields was estimated to 805 kg/ha per decade, while the increasing trend due to rice variety renewal was estimated to 1,290 kg/ha per decade. Thus, 38 % of the yield increases can be related to climatic variation and the remaining 62 % to changes in rice varieties. Furthermore, the effect of variety renewal on the rice yield increases was more pronounced before the 1990s, while afterward, the yield increases were mainly influenced by climatic variations in Northeast China.