Drought evolution and its impact on the crop yield in the North China Plain

The understanding of the impact of drought on the agricultural ecosystem is key to minimize drought-related yield losses. In this study, we analyzed the spatiotemporal characteristics of drought events in the North China Plain (NCP) based on the Standard Precipitation Evapotranspiration Index (SPEI) and investigated the impact of drought on winter wheat and summer maize yields. The results indicate an overall drought and wetting trend during the winter wheat growing season in the Henan and Shandong provinces, respectively. A significant wetting trend was detected in the NCP during the summer maize growing season at the 1-, 3-, 6-, and 12-month scales. Moreover, the drought episodes clearly reveal that the drought pattern has changed from summer and autumn droughts in the 1980s, to autumn and winter droughts in the 1990s, and to winter and spring droughts in the recent decade. Our results also show that the annual variations in the detrended SPEI can explain extensive fluctuations associated with both winter wheat and summer maize yields in the NCP. Furthermore, considerable differences in the relationship between agricultural crop yields and the SPEI time series with different lags were observed; the most correlated time scale increases with the advancement of the winter wheat growth stage. The correlations between the winter wheat standardized yield residuals series (SYRS) and detrended SPEI in three subperiods are consistently high and stable, whereas a substantial decrease of the correlation was observed at all time scales for summer maize, except for the 1-month lag. Our findings can help to better understand the drought evolution in the NCP in recent decades and hence provide stakeholders with references for the design of future drought mitigation plans.