| Vegetation phenology is a natural phenomenon formed by vegetation adapting to the regional climate with an annual cycle,and directly affects the life activities of vegetation,which in turn affects its yield and quality.In the context of climate change and the COVID-19,world food security is facing serious challenges,and the No.1 Document of the Central Government in 2022 pointed out that we should stabilize the basic plate of agriculture,ensure absolute food security,and fill the rice bowl with Chinese food.In this paper,we extracted the date of green-up,heading and maturity of winter wheat in Henan Province from 2000 to 2015 based on dynamic threshold method and derivative method using remote sensing data,actual measurement data of agricultural meteorological stations,statistical data and other geographical data,and explored the spatial and temporal distribution and variation patterns of each phenological period.The response of winter wheat phenology to different time scales of drought index SPEI,temperature and sunshine hours and their effects on yield were analyzed in order to provide reference for winter wheat agricultural production.The following conclusions were obtained.(1)Spatial and temporal variation of winter wheat phenological periodThe average greening period of winter wheat on the metric scale was concentrated between 40 d and 50 d,heading period was concentrated between 90 and 115 d,and maturity period was concentrated between 120 and 145 d.The average greening,heading and maturity periods of winter wheat on the provincial scale were 48.9d,108.7d and 139.7d,respectively.Spatially,there was little difference between north and south in the return period of winter wheat in Henan Province from 2000 to 2015,and the heading and maturity periods showed a clear trend of early south and late north.Except for the relationship between greening stage and longitude,which was not obvious,winter wheat phenological stage showed a strong correlation with latitude and longitude.For each 1° increase in latitude,the greening,heading and maturity periods were delayed by 1.71 d,4.49 d and 5.79 d,respectively,and for each 1°increase in longitude,the heading period was advanced by 4.62 d and the maturity period was delayed by 4.82 d.Temporally,the greening,heading,and maturity dates of winter wheat from 2000 to 2015 all showed different degrees of advancement.At the metric scale,the rate of change of greening date was 0-1d/year,the rate of change of heading date was 0-4d/year,and the rate of change of maturity date was 0-2d/year.at the provincial scale,the average advance of greening date of winter wheat was 0.23days/year,the average advance of heading date was0.21days/10 year,and the average advance of maturity date was 0.26days/10 year.The average advance of maturity date was 0.26days/10 year.(2)Response of winter wheat phenology to climate changeFor the greening stage,the pre-season lengths of drought index SPEI,mean temperature,and sunshine hours were 1 month,1 month,and 2 months,respectively.For the tassel stage,the pre-season lengths of drought index SPEI,mean temperature,and sunshine hours were 1month,3 months,and 4 months,respectively.For the maturity stage,the pre-season lengths of drought index SPEI,mean temperature,and sunshine hours were 2 months,5 months,and 1month,respectively.For the green-up date,SPEI(February)was slightly more positively correlated with the re-greening date,and moderate drought would promote wheat re-greening in northern and southern Henan and inhibit wheat re-greening in central Henan;temperature(February)was mainly negatively correlated with the re-greening date,and warming would inhibit wheat regreening in Zhoukou and promote wheat re-greening in other regions;sunshine hours(January-February)was mainly positively correlated with the re-greening period,and increasing sunshine hours would inhibit wheat re-greening in Zhoukou and promote it in other places.For the heading date,SPEI(April)was mainly negatively correlated with the heading date,and increased drought would promote wheat heading in the central region and inhibit wheat heading in other regions;temperature(February-April)was mainly negatively correlated with the tasseling period,and increased temperature would promote wheat heading;sunshine(January-April)was mainly negatively correlated with the heading period,and increased sunshine hours would promote wheat heading.For maturity date,SPEI(May-June)was mainly negatively correlated with maturity,and moderate drought could promote winter wheat maturity in Shangqiu and Zhoukou and inhibit it in other regions;temperature(February-June)was mainly negatively correlated with maturity,and warming was favorable to wheat maturity;sunshine(June)was mainly positively correlated with maturity,and increased sunshine hours were favorable to wheat maturity in northern Henan and unfavorable to wheat maturity in other regions.(3)Coupling effects of drought,temperature and sunshine hours on wheat phenologyWith the coupling of the three climatic factors,the dominant influence factor of wheat re-greening in northeast Henan was drought index,and in south-central Henan was temperature and sunshine.Winter wheat tassel stage was influenced by mean temperature to the greatest extent,but was significantly influenced by sunshine hours in some areas in central Henan.The maturity of winter wheat was significantly affected by all three factors,with drought having the greatest influence in north and southeast Henan and temperature and sunshine hours in other regions.(4)Impact of winter wheat phenological changes on yieldWheat yield is significantly negatively correlated with wheat green-up date,heading date and maturity date,and the advancement of wheat greening,heading and maturity in most regions will lead to yield increase to some extent,and the advancement of local greening and tassel in Xinxiang City,Anyang City and Zhoukou City will lead to yield reduction. |
