Spectral Response Of The Changes Of Agronomic Characters In Frosted Winter Wheat Under The Different Topsoil Moistures

Recently,with the frequent appearance of extreme global climate,winter wheat freeze injury monitoring is becoming more difficult,unpredictable and complex.The winter wheat freeze injury consisted of wintering stage freeze injury,regreening stage freeze injury and late frost injury.For the winter wheat in Huang-Huai-Hai Region,late frost injury occcurred frequently and effected on winter wheat yield greatly.The occurrence of a disaster is often affected by many factors.The occurrence of late frost injury is closely related to the weather condition,soil condition,management method and so on.With the development of hyperspectral technology,it is convenient to monitor the winter wheat late frost injury.The hyperspectral monitoring of winter wheat late frost njury under different soil moistuer is a problem worthy of discussion.In this paper,To explore characteristics of hyperspectral reflectance responding to late frost damage in winter wheat canopy under different topsoil moisture levels and test abilities of sensitive wavelengths to predict extents of yield change,respectively,pot experiments with three levels of topsoil moisture of Dry?<10%?,Moderate?10-20%?and Wet?>20%?were conducted at the jointing stage of winter wheat in 2013 and 2016.Acquisiting canopy spectra of frosted and unfrosted winter wheat,plant height,yield componentss?ear number per plant,kernel number per ear,1000-kenel weight,yield per plant?and dry matter weight.Extracting sensitive spectral indices,then building predicting model based on sensitive spectral indices.The best fitting model and the prediction accuracy are determined by using the decision coefficient?R²?,the relative root mean square error?RRMSE?and the ratio of prediction deviation?RPD?.The major contents and results in this research are as follows:?1?Based on the ANOVA analysis of yield componentss under different topsoil moisture,the results indicate that:kernel number per ear and yield per plant generally have a reducing trend with the decrease of topsoil moistures.Late frost injuries showed the most significant?P<0.05?influences on winter wheat yield under conditions of the treatment Dry.Analyzing the canopy reflectance of winter wheat under different topsoil moisture,the results indicate that:In green peak region?near 523 nm?,yellow edge region?near 571 nm?,red edge region?near 732 nm?and two water absorption bands?around 952 nm and 1 145 nm?of the near-infrared region,the first derivative reflectance of winter wheat canopy was more different under conditions of the treatment Dry+Frost than the treatment Moderate+Frost and Wet+Frost.After removing the influences of different topsoil moistures on spectrum reflectance,difference curves of the first derivative reflectance responding to late frost damages under the treatments Dry,Moderate and Wet were quite different mainly in the yellow edge region?centered at 570 nm?and the red edge region?centered at 710 nm?.?2?Correlation analysis was made between CRPH,the changes of yield components and CDMW and the original spectral value,the first derivate value,the difference of first derivate value and the spectral index.The results are as follows:400⁵20nm and 571⁶99nm in normalized spectral reflectance,685⁷21nm in the difference of the first derivate reflectance,are sensitive to CDMW.574⁷01nm in normalized spectral reflectance,706⁷25nm in first derivative reflectance,693⁷28nm in the difference of the first derivate reflectance,are sensitive to CRPH.The CRPH and CDMW have more sensitive spectral indices,which were 23 and 16,respectively.There were only 7 sensitive spectral indices of CYPP.The formula of the sensitive spectral indices contains the reflection information of the band in red edge.?3?ND₇₀₅,CI_{red edge},SR₇₀₅,RMCARI/ROSAVI,SR₅₅₅ and LHI-3,6 indexes can be used for predicting the CRPH of frosted wheat under different surface soil moisture,prediction accuracy reached a significant level of 0.001.CIred edge,OSAVI,LHI-1 and HI 4 indexes can be used for the predicting the CYPP of frosted wheat under different surface soil moisture,prediction accuracy reached a significant level of 0.05.SR₅₅₅?SR₇₀₅?ND₇₀₅?PSSRa?PSSRb?CI_{red edge}?OSAVI?RTCARI/ROSAVI?LHI-1,9 indexes can be used for the predicting the CDMW of frosted wheat under different surface soil moisture,prediction accuracy reached a significant level of 0.001.