Temporal-Spatial Characteristics And Risk Assessment Of Maize Drought In Northeast China

Agriculture is one of the areas most sensitive to climate change.In recent years,global temperatures have risen,meteorological disasters have occurred frequently,and crop growth has been seriously affected.Drought is one of the most common natural disasters in the world.As a traditional agricultural country,China's losses due to drought are becoming increasingly serious.As one of the main maize producing areas in China,the research on the drought risk of maize in the Northeast region is conducive to agricultural production practices and the formulation of drought resistance measures,and has very important practical significance.Based on daily weather data from 1981 to 2015 in Northeast China,we analyzed the spatial and temporal distribution characteristics of water supply and demand and drought in maize growth period.According to the theory of natural disaster risk,we construct a maize drought risk index in Northeast China from four aspects: hazard factor,vulnerability,exposure,and drought resistance capacity.The main conclusions are as follows:1.Crop water deficit index CWDI can effectively represent the drought situation of maize in Northeast China.2.Before the mid-1990 s,the water supply of Maize in Northeast China was mostly in sufficient state,and after the mid-1990 s,the water supply of maize was mostly in deficit state.During the growth period of maize,the distribution of precipitation gradually increased from west to east,and the change rule of water demand was opposite.The greater the precipitation,the smaller the coefficient of variation,the greater the water demand,the larger the coefficient of variation.And the variation coefficient of precipitation is between 0.2-0.38,indicating that the interannual volatility is strong;the variation coefficient of water demand is less than 0.1,indicating that the interannual volatility is weak.3.The distribution of maize drought frequency in different drought grades in Northeast China is very significant,and light drought frequency > medium drought frequency > heavy drought frequency > special drought frequency.And the frequency of light drought was significantly higher than that of other drought,above 0.2.In all growth stages,the highest frequency of light drought is jointing heading stage,above 0.25.The frequency of moderate and severe drought is close to each other in each growth period,both of them are about 0.13.The highest frequency of special drought occurred in the sowing seedling stage,and nearly 1/3 of the area was above 0.35.The variation coefficient of different levels of drought frequency is different in different growth periods.The maximum of variation coefficient of light,medium and heavy drought is in heading milk stage,which is 2.4,3.9 and 6.1 respectively;the maximum of variation coefficient of spec ial drought is in jointing heading stage,which is 3.2.4.The drought risk of maize in Northeast China gradually decreases from west to east,and the coefficient of variation is smaller in areas with higher risk.Vulnerability gradually decreases from the northwest to the southeast,and the coefficient of variation is greater in areas with greater vulnerability.Exposure is stronger in areas south of central China,and its corresponding coefficient of variation is smaller.Disaster prevention and mitigation capacity is stronger in the south of the study area,and its coefficient of variation gradually decreases from northwest to southeast.The drought risk of maize gradually decreased from southwest to northeast,and its coefficient of variation gradually increased.