The Effects Of Climate Change And Human Activities On Maize Yield In Heilongjiang Province

Under the changing environment,that is,under the dual effects of climate change and human activities,agricultural development and food security and other aspects of Heilongjiang province are seriously threatened.Especially,maize is the most important crop in Heilongjiang province.Therefore it is of great significance and application value to study the effect of changing environment on maize yield in Heilongjiang province.Collected to 23 meteorological sites in Heilongjiang province,the meteorological data such as precipitation,temperature,sunshine time and maize yield data,as well as the national climatic data center website related sunspot data,directly from two direction of qualitative and quantitative analysis of the meteorological elements(precipitation,temperature and sunshine hours.),the remote correlation factor,sunspots and find its influence on maize yield in Heilongjiang province.The main research results are as follows:(1)Continuous wavelet method was used to obtain the cycle change of maize yield before and after detrending in Heilongjiang province.After detrending,the main period ol maize yield sequence was about 13a,and the subperiod was about 3a.(2)Based on empirical mode decomposition(EMD)method for corn production decomposition,reveals the periodic characteristics of the component:maize yield sequence was broken down into two IMF components and a residue,which the IMF reflect was a fluctuation of the scale of the about 3-6 a,in the whole cycle of oscillation was relatively uniform,year of adj acent peaks and troughs appeared;IMF2 was characterized by 14a-scale fluctuation with slow oscillation frequency,relatively stable and small amplitude and gentle fluctuation.For the residual term(R),the overall maize yield during the study period showed an upward trend.(3)The qualitative analysis method of cross wavelet transform and wavelet coacervate spectrum was adopted to elucidate the influence of climate change and human activities on maize yield.On the micro level,PDO,temperature,ENSO and precipitation mainly affected the high-frequency fluctuation(short-cycle fluctuation,IMF1 component)of maize yield,and AO,sunshine duration and sunspots mainly affected the medium-frequency fluctuation(medium-cycle fluctuation,IMF2 component)of maize yield.Human activities mainly affected the trend part of corn yield(residual term,R),among which the amount of fertilizer application was the main influencing factor.On the whole,the micro study was more detailed than the macro study,which was more helpful to reveal the mechanism(4)Based on EMD decomposition of maize yield and multiple linear regression,macro and micro maize yield prediction model was built,the results showed that the microscopic forecast maize yield component and the synthetic prediction accuracy was superior to maize yield prediction results directly on macro,respectively,the forecast of each component to synthesis method can effectively improve the prediction accuracy of maize yield(5)Residual analysis method and random forest algorithm were used to quantitatively analyze the impact of climate change and human activity related factors on maize yield.The contribution rate of climate change factor to the maize yield sequence of Heilongjiang province was 31.1%,and the contribution rate of human activity factor(fertilizer application amount)to the maize yield sequence of Heilongjiang province was 68.9%.The important degree of the five main factors influencing maize yield was:fertilizer application amount>PDO>temperature>precipitation>sunshine hours.