干旱强度及发生时间对华北平原五省冬小麦产量影响

本文利用2001-2016年时间分辨率为8 d的MOD09A1和MOD16A2的数据集,构建了基于NDVI和ET/PET的干旱指数(DSI),分析华北平原五省不同程度的干旱在时间和空间上的分布情况,探究不同程度的干旱作用于冬小麦不同生长阶段对农作物产量产生的影响。研究表明:①年际分布上,2001-2002年干旱最为严重,其余年份干旱显著减缓,年内分布上,干旱主要集中发生在春季和秋季,夏季次之,冬季最少;②空间分布上,河北北部、河南南部、安徽及江苏的中部和北部、山东东部是干旱多发区;③干旱对冬小麦产量的影响研究表明,越冬期发生初旱对产量起促进作用,而在乳熟成熟阶段发生初旱则会导致农作物减产;轻旱发生在乳熟期会对冬小麦产量产生显著影响,而中旱发生在开花、乳熟成熟期都会对产量产生显著影响,随干旱程度加重,干旱对作物产量产生显著负作用的生长期越长;此外,在播种时若出现水分短缺也会对冬小麦的产量产生影响,尤其是发生重旱和特旱。研究不同强度干旱发生在不同生长阶段对冬小麦产量的影响,对研究区的灌溉时间规划以及保墒增产具有重要理论与现实意义。

Impacts of drought intensity and drought duration on winter wheat yield in five provinces of North China plain

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.