Evolution Of Climate Resources And Drought Risk Analysis During Growing Periods Of Winter Wheat Under Climate Scenario In Northern Winter Wheat Belt

Daily meteorological station data and the future scenario data of RCP4.5 scenario simulated by PRECIS was selected to compare the simulation accuracy of the active accumulated temperature,accumulated thermal development unit and the development rate model?Wang&Engel model?were used for simulating the jointing,heading,milk-ripe and maturity date of winter wheat in northern winter wheat belt.In this study,model with high simulation accuracy was selected to simulate winter wheat growth stages in the future,analyzing the variations of agricultural climatic resources and the evolution characteristics of drought during each growth stage and growing period of winter wheat in the northern winter wheat belt.The results were as follows:?1?Wang&Engel model could most satisfactorily simulate days during sowing-jointing and sowing-heading,root-mean-square error?RMSE?were 3.0³.7 days,index of agreement were above 0.9.Active accumulated temperature method could most accurately simulated days during heading-milk-ripe and heading-maturity,RMSE were 2.6³.1 days,index of agreement were above 0.8.?2?In 2031-2090,the growth stage of winter wheat postponed before winter,and advanced after winter in the study area.The variation trend of each winter wheat growth period was significant?P<0.01?,with the change value of 1.8,1.7,-1.3,-1.1,-1.1,-1.3,-1.4 d·?10a?^-1 for date of sowing,the start of wintering,regreening,jointing,heading,milk-ripe and maturity,respectively.Compared to baseline period?1976-2005?,space difference of regreening period was the largest in 2040s?2031-2060?,while the more spatial variation of regreening and maturity stage and minimum spatial variation of sowing date were achieved in 2070s.The regreening date would more advanced in the northwest area in 2040s,which was opposite to that in 2070s.The maturity date would more advanced in the northwest area in 2070s.The duration of over-wintering period,heading-milk ripe,milk ripe-maturity and the whole growth period were significantly reduced in 2031-2090?P<0.05?.Compared to the baseline period,the duration of over-wintering period and the whole growth period shortened by 18.3³1.6 and 22.5³7.5 days respectively in 2070s,and contribution rates of over-wintering period to the changes of the whole growth period were above 70%.?3?In future,the thermal resources of winter wheat increased,while the precipitation,light resources and climate production potential decreased in the study area.Thermal resource during over-wintering period increased greatly in 2031-2090,with the change of negative accumulated temperature during over-wintering period being 37.8?·d·?10a?^-1.The precipitation during sowing-wintering and the whole growth period reduced significantly?P<0.05?,with the variation value of-7.1 and-11.8mm·?10a?^-1respectively.The solar radiation during over-wintering period,jointing-heading,heading-milk ripe and the whole growth period reduced highly significantly?P<0.01?,reducing by 62.4MJ·m^-2·?10a?^-1 during the whole growth period.?4?Future climate production potential of winter wheat sharp declined in northeastern border of study area,but the space distribution features of light,temperature and water resources changed inconsistently.Compared to the baseline period,the spatial variation of thermal resources was greater during over-wintering and regreening-jointing period.The thermal resources sharp increased in the northwest part of the study area in 2040s and 2070s.The changes of thermal resources during regreening-jointing were different between the east and west part of the study area in 2040s,while the change was greater between the southeast and northwest part of the study area in 2070s.The precipitation during sowing-wintering,heading-milk ripe and the whole growth period decreased in the northwest and increased in the southeast in 2040s.However,the precipitation during over-wintering and jointing-heading increased in most part of study area,which was decreased during regreening-jointing and milk ripe-maturity period.The precipitation during jointing-heading increased in most part of study area in2070s,which was decreased during other growth period.The spatial variability of radiation would greater during sowing-wintering in 2040s and reduced rapidly in areas as southeast of Hebei,Tianjin.The spatial variability of radiation was greater during regreening-jointing in 2070s and its decrease range increased gradually from southeast to northwest.?5?In the future,the water demand and precipitation of winter wheat both reduced in the northern winter wheat belt,and the drought conditions were still severe.There were spatial differences between drought frequency and drought risks from east to west part of study area.The frequency of middle drought and severe drought was higher during sowing-wintering in the eastern study area,while the frequency of severe drought and extreme drought was higher in other growth periods.In west of study area,the frequency of middle drought was higher,the frequency of severe drought and extreme drought increased with growth stages changing.In the future,the drought risk during multiple growing periods increased gradually from west to east.