Impact of temperature changes on early-rice productivity in a subtropical environment of China

The impact of climate warming on rice production has attracted considerable attention. In this study, we (1) analyzed trends in maximum and minimum temperatures and low temperature events from 1980 to 2010 for early season, (2) evaluated relationships between rice-yield attributes and maximum or minimum temperature by using data from field experiments conducted in early seasons of 1991-2004, and (3) compared grain yield among different rice establishment methods by using data from field experiments done in early seasons of two contrasting years (2009 and 2010) with respect to low temperature events in Changde, Hunan Province, China. The results showed that maximum and minimum temperatures in early season increased by 2.2 °C and 2.1 °C, respectively, during the period 1980-2010 and there was a significant relationship between early-rice grain yield and maximum temperature. Grain yield increased by 7% for each 1 °C increase in growing-season maximum temperature. The increase in grain yield with maximum temperature was driven from the increased daily yield rather than growth duration. However, stabilizing growth duration was critical to overcome the potential negative impact of future climate warming on early-rice production. On the other hand, the climate warming did not lead to significant decreases in low temperature events. In the year with low temperature events, direct seeding produced less grain yield than transplanting and seedling throwing by 32% and 23%, respectively. Our study suggests that direct seeding is a high risk establishment method for early-rice production and seedling throwing may be a more satisfactory method of establishing early-rice under current climate change scenarios.