Spatial-temporal Distribution of Apples with Different Drought Levels in Northern China

Taking the major apple producing provinces in northern China as the research area, spatial-temporal distribution characteristics of different levels of apple drought during different growing periods are quantitatively evaluated. The drought index is graded, and historical disaster data collected are used to count disaster samples of different drought levels during different growth stages of apple, which verifies the rationality of the drought index level. Then the spatial-temporal distribution of different levels of drought, drought occurrence frequency, and occurrence range of apples during different eras in northern China are analyzed based on the validated drought grade index. Results show that among 46 total samples, the fully matched and basically matched samples account for 85%. Therefore, the drought grade index constructed can reflect the actual drought conditions reasonably for apples in northern China. Spatial distribution characteristics of drought levels decrease sequentially from north to south. The severe drought during different growing periods for apples is mainly distributed in northern and central of Gansu and northern Ningxia. The degree of drought changes greatly with the change of years in north central Shanxi from fruit tree sprouts to flower buds sprout, in Shanxi, Shandong, north Shaanxi from flower buds sprout to flower full bloom, and in Henan from mature to fallen leaves. The area of severe drought gradually increases with changes of the years from 1981 to 2010 in fruit tree sprouts to flower buds sprout and mature to fallen leaves. The frequency of no drought increases from north to south and the high frequency areas occur one time or above in two years. The frequency of severe drought decreases from north to south and the high frequency areas occur one time or above in two years. The light drought has dominated during the past 36 years in the study area, and the range of severe drought during the period from flower to maturity is larger than the other period. The ratio of drought occurring stations show a significant increasing trend for severe drought in the period from fruit tree sprouts to flower buds sprout and the moderate drought in the period from flower to maturity. The drought is severe and the frequency is high in the northwest. In the production of apples, a drought prevention plan should be prepared on the basis of drought warning, and attention should be paid to the timely response to drought at different growth stages.