Effects Of Meteorological And Agricultural Drought On Winter Wheat Growth And Yield

Drought is one of the main natural disasters affecting crop growth process and yield.In order to deal with drought disaster in crop growth period scientifically and reasonably and reduce the influence of drought on winter wheat growth and yield,it is of great si gnificance to explore the influence of different types of drought on winter wheat growth process and yield.On the basis of collecting meteorology,soil,crop,geography and other data,this study analyzed the temporal and spatial evolution and drought characteristics in different regions of China in 1961-2100 based on 12-month SPEI.Further study about meteorological drought and agricultural drought from 1-to 9-month timescale in winter wheat growth period was did.DSSAT-CERES-Wheat model was used to simulate the winter wheat growth period,biomass in winter wheat maturity,the maximum leaf area index and winter wheat yield of 108 agrometeorological stations in China under SSP1-2.6,SSP2-4.5,SSP3-7.0 and SSP5-8.5 scenarios.At last,the relationships between biomass in winter wheat maturity/the maximum leaf area index/winter wheat yield and SPEI/SMDI at different timescales were analyzed to explore the effects of meteorological drought and agricultural drought on winter growth and yield.The main conclusions are as follows:(1)The spatiotemporal evolution and drought characteristics under different drought levels in different subregions of China in historical and future periods were analyzed comprehensively.Compared with the historical period,the drought tendency in the northwest desert region of China would increase in the 21st century,while wet tendency would occur in the other regions.With the increase of emission scenarios,the humidification trend in the Qinghai-tibet region,the northeast temperature region and the north China warm temperate region would increase gradually.Compared with 1961-2000,the frequency,duration and intensity of extreme drought in the northwest desert region of China and the Qinghai-tibet plateau region would increase over 2021-2060 and 2061-2100,while the mild,moderate and severe drought duration and severity over 2021-2060 and 2061-2100 gradually decreased.The drought frequency in the humid and semi-humid region of north China is lower than that in the other regions.The drought frequency over future under SSP1-2.6scenario is higher than the other three scenarios.The extreme drought duration and intensity under SSP5-8.5 scenario is greater than the other three scenarios.(2)The spatiotemporal evolution characteristics of multi-timescale drought in winter wheat growth period in winter wheat planting area in China were systematically expounded.The meteorological drought of winter wheat growth period in Huang-Huai-Hai Plain over 1981-2015 was more frequency than that in Xinjiang.The agricultural at the 0-10 cm and 10-40 cm depth occurred more frequently in Huang-Huai-Hai Plain than in the other two regions.The agricultural drought at the 10-40 cm depth in Huang-Huai-Hai Plain is more serious than that in the 0-10 cm depth,while the agricultural drought in Xinjiang was just the opposite.In the future period,the short and medium timescale meteorological drought frequency would be higher from winter wheat sowing to greening period.The agricultural drought frequency at 0-10 cm depth would be higher from jointing to maturation period(From March to June).The agricultural drought frequency at 10-40 cm depth would be higher from greening to anthesis period(January to April).There is an increasing trend of agricultural drought in winter wheat growth period from SSP1-2.6 to SSP5-8.5 scenario.The agricultural drought intensity at 0-10 cm depth is larger than that at10-40 cm depth under SSP3-7.0 and SSP5-8.5 scenarios.(3)DSSAT-CERES-Wheat model was used to simulate and analyze the variation of winter wheat growth index and yield comprehensively in historical and future period.DSSAT-CERES-Wheat model generally performed well in simulating winter wheat anthesis date,maturity date and yields(with R~2 larger than 0.64,where R~2 is determination of coefficient).It can be used to simulate the growth process of winter wheat.The biomass in winter wheat maturity,the maximum leaf area index and winter wheat yield in Huang-Huai-Hai Plain and the other region was larger than that in Xinjiang in the historical period.The winter wheat flowering date and maturity date over 2021-2060 and 2061-2100were advanced,and the flowering and maturity date of winter wheat in high emission scenarios are larger.The winter wheat flowering date and maturity date in Huang-Huai-Hai Plain and Xinjiang are delayed compared with the other region.The biomass in winter wheat maturity,the maximum leaf area index and winter wheat yield were not significantly different over 2021-2060 under the four scenarios.Compared with 2021-2060,the biomass in winter wheat maturity,the maximum leaf area index and winter wheat yield were increased in 2061-2100.They increased greatly in Huang-Huai-Hai Plain and Xinjiang under SSP5-8.5 scenario.(4)The effects of multi-timescale meteorological and agricultural drought on winter wheat growth and yield were systematically revealed from multiple aspects.The 4-month SPEI and 1-month SMDI at the 0-10 cm 10-40 cm depth had more effected on the biomass in winter wheat maturity,the maximum leaf area index and winter wheat yield during historical and future period.The correlation coefficient between agricultural drought index(SMDI)and the biomass in winter wheat maturity,the maximum leaf area index and winter wheat yield were larger than that of meteorological drought index(SPEI),which indicates that agricultural drought has great influence on winter wheat growth and yield.The correlation coefficient between SMDI at 0-10 cm depth and the biomass in winter wheat maturity,the maximum leaf area index and winter wheat yield were about 0.3,0.4 and 0.5 respectively.With the increase of emission intensity,the correlation between drought in winter wheat growth period and the biomass in winter wheat maturity,the maximum leaf area index and winter wheat yield were not different over2021-2060,while that gradually decreased over 2061-2100.The correlation coefficient between drought index and the maximum leaf area index and the biomass in winter wheat maturity in each month of winter wheat growth period was not different.The SPEI and SMDI during the jointing and milk period(from March to May)had great influence on winter wheat yield,but less at overwintering period of winter wheat,which indicated that proper“drought exercise”at overwintering period had little effect on winter wheat yield.SMDI and SPEI explained more than 14%and less than 2%of winter wheat yield variability,respectively.The correlations between drought indexes and the maximum leaf area index,the biomass in winter wheat maturity and winter wheat yield were largest in Huang-Huai-Hai Plain,followed by Xinjiang.The yield reduction rates of winter wheat of most sites in Huang-Huai-Hai Plain and the other region were between 5%and 25%in the drought years of historical period.The yield reduction rates of winter wheat of most sites in Huang-Huai-Hai Plain over 2021-2060 and 2061-2100 were between 15%and 30%,and that in most sites in Xinjiang were between 5%and 15%.This study can provide a useful reference for the formulation of drought resistance measures in winter wheat growth period.