Spatio-temporal Characteristics Of Phenology Of Winter Wheat In Shandong Province And Its Responses To Climate Change

Vegetation phenology is a natural phenomenon with annual cycle due to the influence of environmental factors including climate change,hydrological status,soil physicochemical properties.Vegetation phenology is the growth and development rhythnm formed by the long-term adaptation to seasonal changing environment.The crop phenological changes will directly influence a variety of biophysical and physiological processes of the crops and thus influence the quality and yield of the crops.Shandong Province is a major province of grain production in China,and its grain yield and quality are directly influence the national food security.Winter wheat is the main crop in Shandong Province.Analysis of the temporal and spatial characteristics of winter wheat phenology in Shandong Province and its responses to climate factors can not only comprehensively and deeply explore the characteristics of the growth processes of winter wheat,but also provide reference for the monitoring and management of agricultural fields in Shandong Province.In this study,based on the MODIS EVI multi-temporal remote sensing data,the field samples as well as the phenological data measured by agricultural meteorological station,the winter wheat four phenological stages(green-up date,jointing date,heading date and maturity date)in Shandong Province from 2003 to2019 were extracted and analyzed.Combined with daily meteorogical data,this study discussed the responses characteristics of winter wheat phenological changes to various climatic factors.It is expected that the results will provide data support and scientific reference for farmland and winter wheat management,as well as agricultural ecological protection in Shandong Province.(1)Extracting and analyzing planting area and four phenological stages of winter wheat based on remote sensing dataPlanting area and four phenological stages(green-up date,jointing date,heading date and maturity date)of winter wheat in Shandong Province extracted from MODIS EVI remote sensing data have high accuracy,and have better correlation with the measured data.The results showed that the green-up date,jointing date,heading date and maturity date of winter wheat in Shandong Province from 2003 to 2019 were concentrated in the45th—70th day of year,75th—100th day of year,103th—125th day of year and 135th—155th day of year,respectively,and showed a spatial pattern of the south earlier than the north,as well as inland earlier than the coastal regions.The difference of phenological pattern between latitudinal zonation is more significant than that between the location of the sea and land.For every 1° increase in latitude,four phenological stages delayed by3.93 d,2.31 d,2.80 d and 2.12 d respectively.At the whole regional scale,the decade trend rates of green-up date,jointing date,heading date and maturity date were 1.56 d/10 a,0.65 d/10 a,-0.54 d/10 a and 2.51 d/10 a,respectively,and the change trend of phenological stages all presented an insignificant feature.At the pixel scale,the green-up date and jointing date were mainly delayed,and the areas with the significant delay tendency accounted for 1.65% and 3.05% of the total area,which were mainly distributed in the eastern coastal regions and the southern areas of Shandong Province.Nearly 6.56% of the total area showed a significant advance trend of the heading date,which was mainly located in the northeast of Heze.What's more,the area with a significant delay trend of maturity date was accounted for 10.23% of the total area,which was generally found in Binzhou,Dezhou and Jining.(2)Phenology of winter wheat responses to climate changeThe average temperature in the past two months and three months had a significant effect on the green-up date of winter wheat in Shandong Province.The high energy of average temperature rise promoted green-up date to advance,which was more obvious in the northwest and east coastal areas of Shandong Province.There was no significant correlation between green-up date and the maximum temperature in recent three months,two months and the same month,but a significant negative correlation between green-up date and the minimum temperature in recent three months and two months.The regions with strong significance were mainly concentrated in the northwest regions and the southern areas of Shandong Province.There was no significant negative correlation between green-up date and the changes of precipitation and sunshine hours in recent three months,two months and the current month.The average temperature in the past three months had a significant effect on the jointing date,and the increase of average temperature was conducive to the advance of the jointing date of winter wheat in the most areas outside southern of Shandong Province.There was no significant positive correlation between jointing date and maximum temperature.The response of jointing date to the minimum temperature in the past two months and three months is more sensitive: in the western coastal areas and the eastern regions of Shandong Province,the rising of the minimum temperature promotes the advance of jointing date.The effect of precipitation and sunshine hours in recent three months,two months and the same month on jointing date was not significant.The average temperature in the past three months had a significant effect on the heading date of winter wheat.The increase of average temperature could advance the heading date of winter wheat in the most areas of Shandong Province.There were significant spatial differences in heading date affected by the highest temperature in recent three months,two months and the same month: Jining,Linyi and other places in the southern of Shandong Province mainly delayed,while in the northern of Shandong Province mainly advanced.There was a significant negative correlation between heading date and minimum temperature in recent three months.There was no significant positive correlation between precipitation and heading date in recent three months,two months and the same month.There are obvious spatial differences in the effect of increasing sunshine hours on heading date: the early effect is dominant in the southern of Shandong Province,while the delayed effect is dominant in the peninsula and the northwest of Shandong Province.The average temperature of the month has a significant effect on the maturity date,and the increase of the average temperature leads to the delay of the maturity date,which is more obvious in the northwest of Shandong Province such as Tai'an,Jining.In the northern central of Shandong Province,the highest temperature promoted the maturity date to advance,while in the southern central of Shandong Province,it mainly delayed.The increase of minimum temperature in the same month delayed the maturity date of most areas in the northwest of Shandong Province.The increase of precipitation in recent three months,two months and the same month is conducive to the advance of maturity date,and the effect is obvious in the northwest and the central of Shandong Province.The increase of sunshine hours had no significant effect on the maturity date.