Spatial distribution characteristics and impact on spring maize yield of drought in Northeast China

Global warming has caused strong increase in temperature in China and this especially evident in Northeast China. As a consequence, drought stress has been more frequent, severe and over larger areas in this region. The severe drought stress has increased the risk of spring maize production in this major maize cultivation area of China. Thus understanding the spatial distribution of drought in relation to spring maize growth and yield formation was critical for in depth understanding of policy and decision making to deter yield reduction in Northeast China. Daily meteorological data for the period 19612012 were collected at 69 meteorological stations to analyze the effects of global warming on drought stress and yield of maize in Northeast China. Also spring maize growth and yield data were collected for the same period in the study area. The Penman-Monteit method was used to calculate potential evapotranspiration (PET). Based on the PET, the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated (SPEI_PM), which was used to classify drought grade of the study area. The drought hazard index in each meteorological station was calculated then with weight and occurrence rating score of every drought grade. The trend in SPEI was calculated for five growth stages using the Mann-Kendall test and the relationship between SPEI_PM and climate-driven maize yield determined using regression analysis. The results showed West Jilin Province and West Liaoning Province were high drought risk areas during maize growing season, while East Jilin Province and East Liaoning Province were low drought risk areas. Drought risk also increased with maize growth in East Heilongjiang Province. Moreover, drought intensity and drought-affected area decreased at maize seedling stage but increased at later growth stages of maize for the 52-year study period. High correlations were observed between SPEI_PM3-7 (SPEI_PM from May to July) and climate-driven maize yield in West Liaoning Province for 1991–2012 and also between SPEI_PM3-8 (SPEI_PM from June to August) for West Jilin Province, East Jilin Province as well as Songnen Plain (P < 0.01). In addition, climate-driven yield in Central Jilin Province and SPEIPM3-8 were significantly correlated (P < 0.05). Generally, drought intensity and drought- affected area in spring drought areas such as Songnen Plain, West Jilin Province, West Liaoning Province and South Liaoning Province decreased gradually. However, drought intensity in study area increased in frequency and severity at late growth stages in Northeast China, especially in the east. In areas with abundant rainfall (e.g., East Jilin Province), the axis of symmetry of the regression equation between climate-driven yield and drought index was closed to 0, suggesting that normal rainfall was sufficient to ensure high yield in the area. In areas with scarce rainfall (e.g., West Liaoning Province and West Jilin Province), the axis of symmetry of the regression equation between climate-driven yield and drought index was closed to 1, suggesting that irrigation was necessary to improve both yield and water use efficiency.