Abstract:

Based on the MOD09A1 and MOD16A2 datasets with a temporal resolution of 8 days during a period from 2001 to 2016, Drought Severity Index (DSI) was quantified to characterize spatiotemporal distribution of droughts of different drought intensities. The correlation coefficients were quantified between drought-affected cropland area and the climatic winter wheat yield. In addition, relevant impacts of droughts with different drought intensities were investigated on the winter wheat yield during different growing periods. The results show that: (1) drought regimes during 2001-2016 showed a declining trend in terms of drought intensity at annual and inter-annual scales. The most severe drought occurred during 2001-2002 while regional and intermittent droughts could be observed during 2003-2010, and were alleviated during 2011-2016 with persistent wetting tendency thereafter. In terms of annual drought distribution, droughts occurred mainly in spring and autumn, some occurred in summer and few droughts in winter; (2) Generally, in terms of the spatial distribution of droughts, central and northern Hebei, southern Henan, Anhui and Jiangsu, and eastern Shandong provinces were dominated by frequent droughts though droughts were in decreasing trends; (3) analysis results concerning effects of droughts on winter wheat yield show that the incipient drought during the winter period can promote the winter wheat yield, while in the milking stage of the winter wheat, occurrence of droughts may decrease crop yield. The mild drought potential has significant effects on winter wheat yield during the ripening interval, while the moderate drought occurs during flowering, milking and ripening periods can have a significant impact on the winter wheat yield. Meanwhile, droughts with higher degree of intensity will have more significant impacts on winter wheat at its earlier growing season. In addition, water shortage due to drought effects during planting periods will reduce the yield of winter wheat, and severe and extreme droughts in particular. Therefore, it is of great merits in quantification of impacts of droughts with different intensities on winter wheat yield in different growing seasons, and it has important theoretical and practical significance for the planning of irrigation and the increase of soil moisture in the study region.

Key words: five provinces of the North China plain, drought intensity, crop yield, food security