Changes in wheat potential productivity and drought severity in Southwest China

Wheat production in Southwest China (SWC) plays a vital role in guaranteeing local grain security, but it is threatened by increasingly frequent seasonal drought in recent years. In spite of the importance, the impact of past climate change on wheat potential productivity and drought severity has not been properly addressed. In this study, we employed a relatively simple resource use efficiency model to analyze the spatiotemporal changes of the potential productivity (PP) and rainfed productivity (RP) of wheat (Triticum aestivum L.) in Southwest China (SWC) from 1962 to 2010. A wheat drought severity index was defined as the relative difference between PP and RP, i.e., (PP-RP)/PP, to evaluate the changing frequency and severity of drought under warming SWC. Across the entire region from 1962 to 2010, the negative impact of decreasing sunshine hours (0.06 h day(-1) per decade, p < 0.05) on PP was offset by the increase in average temperature of wheat growing season (0.22 A degrees C per decade, p < 0.01). PP increased by 283 kg ha(-1) per decade (p < 0.01), while RP did not show significant trend due to increased water stress. The gap between PP and RP has increased by 26 kg ha(-1) per decade (p < 0.01). Moderate and severe drought mostly occurred in central and southern SWC. The percentage of stations experienced moderate or severe drought increased by 2.0 % (p < 0.05) per decade, and reached 52 % in recent decade. Our results, together with the uneven distribution of rainfall, indicate great potential for irrigation development to harvest water and increase wheat yield under the warming climate in SWC.