Impacts Of Climate Change On Spring And Summer Maize Yields Of Main Planting Zone In China In Recent 30 Years

Climate change and extreme climate events have posed a serious threat to agricultural production and food security.Maize is the main food crop in China,and studying the feedback mechanism of maize to climate change and extreme climate events is of great practical significance for maize planting regional planning and increasing and stabilizing yields.At the same time,the light and temperature potential yield is the key index to determine the yield gap of maize and to quantify the impact of climate resources on maize production.Exploring the relationship between climate resources and light and temperature potential yield and yield gap of maize will provide an important reference for formulating regional planning for agricultural development and guiding agricultural production practice.In order to quantitatively study the changes of maize yield and potential yield caused by climate change,and to find an effective way to reduce maize yield gap.In this paper,the first order difference,collinearity detection,Pearson correlation,multiple linear and nonlinear regression methods were used to analyze and construct a statistical regression model for spring-summer maize yield of 121 stations in major maize producing areas in China under the background of climate change from 1988 to 2017.Secondly,the effects of extreme precipitation and temperature events on spring-summer maize were analyzed by using first-order difference,collinearity detection,Pearson correlation and multiple linear regression.Finally,the direct and indirect effects of climate resources on the light and temperature potential yield and yield gap of spring-summer maize under the light and temperature drive were explored based on the step-by-step revised model of light and temperature.The main results of the paper are as follows:(1)The multivariate nonlinear functions performed better than the linear ones in explaining maize yield variation,especially cubic terms and interaction terms of climate variables.According to the Pearson correlation coefficients(r)between the climatic factors and maize yield,spring maize yield was more sensitive to Hum,Sun and Pre and summer maize yield was more sensitive to Pre and temperature.The contribution of climatic factors to account for spring and summer yields change ranked as Pre>Hum>Sun>Tmin>Tmax>Tave.Both the wet-cold and wet-warm climate had positive effects on maize yield,especially the wet-cold climate.However,both the dry-cold and dry-warm climate had negative effects on maize yield,especially the dry-warm climate.Climate change explained 5.8-87.6%of variability in spring maize yields and 6.6-78.5%of variability in summer maize yields,respectively,which were also site-specific.(2)Compared to other extreme climate types,extreme dry heat climate and extreme wet cold climate had the greatest negative impact on spring maize and summer maize,respectively.iID,iHD and CDD had better ability to explain spring maize yield variation and accounted for 6.9%,6.5%and 6.5%of the changes in spring maize yield,respectively.CDD,iHD and R10 had better ability to explain summer maize yield variation and accounted for 13.6%,10.5%and 8.3%of the changes in summer maize yield,respectively.Extreme climate events explained 37.6%of variability in spring maize yields and 43.8%of variability in summer maize yields,respectively,which were also site-specific.The contribution of extreme climate indices type to account for spring or summer maize yields change ranked as threshold>relative>absolute>other(relative>threshold>other>absolute).The yield of spring maize was more correlated with extreme temperature events(negative correlation),especially extreme temperature events.However,summer maize yield was more correlated with extreme precipitation events(negative correlation),especially extreme flooding events.(3)The change trend of climate resources,light and temperature potential yield(Y(T))and yield gap of maize during the growth period from 1988 to 2017 were discrepant.The trend of radiation(Rs)、sunshine percentage(a)、heat degree days(HDD)and diurnal temperature range(Dtr)of spring maize decreased,while growing degree days(GDD)and Photo-degree days(PDD)increased.The trend of Rs、α、PDD and Dtr of summer maize decreased,while GDD and HDD increased.The trend of photo synthetic potential yield(Y(Q))of spring-summer maize decreased,while Y(T)increased.Yield gap(YGQT)between Y(Q)and light and Y(T)of spring maize had increasing trend,while summer maize exhibited decreasing trend.Yield gap(YGTA)between Y(T)and actual yield of spring-summer maize had decreasing trends.The proportion of YGQT to YGTA of spring-summer maize increased,with the fluctuation range of 0.55-0.84 and 0.48-0.96,respectively.The effects of temperature and heat resources on YGQT were 35%and 31%,respectively.Therefore,the effects of temperature and heat resources on YGQT of spring maize were more significant.The effect of light and temperature resources on the YGTA of spring-summer maize is about 61%,so there will is a great yield increasing space of maize.(4)Climate resources directly affect the change of light and temperature potential yield and maize yield gap.According to r values between climatic resources and maize Y(T)(or YGQT and YGTA),spring-summer maize Y(T)(or YGQT and YGTA)was positively correlated with all climatic resources,especially with light resources.The negative effect of heat resources on YGQT of spring-summer maize was greater than that of light resources,and the negative effect of GDD on YGQT of spring-summer maize was the strongest,with r is-0.65 of spring mazie and r is-0.81 of summer maize,respectively.The YGTA of spring-summer maize was positively correlated with all climate resources,and the correlation with light resources was stronger.The slope change trend of climate resource will indirectly affect the changing trend of Y(T)and yield gap.The indirect effects of light resources on spring maize Y(T),YGQT and YGTA were greater,especially Rs and α.This indirect effect is reflected in the consistent growth pace between light resources and spring maize Y(T),or YGQT,or YGTA.When the change trend of light resource increases faster,the change trend of Y(T),YGQT and YGTA of spring maize will also has faster increasement.Similarly,heat resources had a greater influence on Y(T),YGQT and YGTA of summer maize,especially GDD and DTR and the influence reason is the same as above.