Abstract:

The apple planting area and output of Hebei Province are the top in the country, and the temporal and spatial variation trends and characteristics of extreme drought in Hebei Province are analyzed, in order to provide a theoretical basis for scientific irrigation in apple producing areas, and promote the development of local characteristic agriculture and the effective utilization of water resources. Based on the data of 142 ground weather stations in Hebei Province, this paper used surface wetness index and wavelet analysis to study the temporal and spatial characteristics of extreme drought in the apple growing season in Hebei Province in the past 40 years (1981-2020), including the frequency, total number of occurrences and cyclical changes of extreme drought. The results showed that: (1) in terms of time changes, the frequency of extreme drought in the apple growing season in Hebei Province had averaged 0.7-3.5 times per year in the past 40 years. The occurrence of extreme drought in each growing period of apple growing season in descending order was as follows: initial growth period (germination-flowering stage), late growth stage, fruit coloration stage, young fruit stage, and fruit expansion period. Between the decades, the 1980s were the highest, the 2000s were the lowest, and the 2010s showed a recovery trend. (2) In terms of spatial distribution, the total number of droughts in the apple growing season showed the characteristics of less in the northeast and more in the northwest and central and southern regions, and the number of extreme droughts in the southern region was higher than that in the northern region during each phenological period during the year, but the high-value areas of extreme drought occurrence in the fruit expansion period and the late growth period were concentrated in the northwest Hebei region. The variation period of extreme drought in the province was 4-8 a, 7-11 a, 16-20 a. The frequency of extreme drought showed a recovery trend in the young fruit stage and late growth stage of apples in the 2010s, which should attract attention in the production practice.

Key words: Hebei Province, apple, extreme drought, humidity index, spatiotemporal distribution