Estimation of maize canopy chlorophyll density under drought stress based on continuous wavelet transform
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DOI:10.7606/j.issn.1000-7601.2021.04.20
Key Words: drought stress  chlorophyll density  continuous wavelet transform  vegetation index  canopy  maize
Author NameAffiliation
TAN Xianming College of Agronomy, Sichuan Agricultural University/Key Laboratory of Southwest Crop Ecophysiology and Farming System in Southwest, Ministry of Agriculture/Sichuan Engineering Research Center for Crop Strip Intercropping System, Chengdu, Sichuan 611130, China 
WANG Zhonglin College of Agronomy, Sichuan Agricultural University/Key Laboratory of Southwest Crop Ecophysiology and Farming System in Southwest, Ministry of Agriculture/Sichuan Engineering Research Center for Crop Strip Intercropping System, Chengdu, Sichuan 611130, China 
ZHANG Jiawei College of Agronomy, Sichuan Agricultural University/Key Laboratory of Southwest Crop Ecophysiology and Farming System in Southwest, Ministry of Agriculture/Sichuan Engineering Research Center for Crop Strip Intercropping System, Chengdu, Sichuan 611130, China 
WANG Beibei College of Agronomy, Sichuan Agricultural University/Key Laboratory of Southwest Crop Ecophysiology and Farming System in Southwest, Ministry of Agriculture/Sichuan Engineering Research Center for Crop Strip Intercropping System, Chengdu, Sichuan 611130, China 
YANG Feng College of Agronomy, Sichuan Agricultural University/Key Laboratory of Southwest Crop Ecophysiology and Farming System in Southwest, Ministry of Agriculture/Sichuan Engineering Research Center for Crop Strip Intercropping System, Chengdu, Sichuan 611130, China 
YANG Wenyu College of Agronomy, Sichuan Agricultural University/Key Laboratory of Southwest Crop Ecophysiology and Farming System in Southwest, Ministry of Agriculture/Sichuan Engineering Research Center for Crop Strip Intercropping System, Chengdu, Sichuan 611130, China 
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Abstract:
      This study measured maize canopy chlorophyll density and canopy spectrum data under drought stress in each growth period.The original spectral reflectance and canopy chlorophyll density were used for correlation analysis.Using common vegetation index, free combination of bands, continuous wavelet transform to build maize canopy chlorophyll density estimation model, and the coefficient of determination (R2) and root mean square error (RMSE) were used to test its accuracy. The results showed that: compared with the normal control the canopy chlorophyll density during the tasseling stage decreased by 7.8%, 29.5%, and 44.2% under mild, moderate, and severe drought stress, respectively; RVI(555,538), NDVI(555,538) and sensitive wavelet coefficients bior 5.5 (26,792), rbio 2.6 (22,790) and gaus 6 (21,791) had higher correlation with chlorophyll density, and the absolute correlation coefficients were all above 0.900; The validation set R2 of the canopy chlorophyll density estimation models based on sensitive wavelet coefficients were all above 0.850, comparing with other vegetation index models, the average increase was 20.6%, and the average RMSE decreased by 32.6%; The optimal model was a univariate linear regression model with gaus 6 (21,791) as the independent variable R2=0.864, RMSE=1.532. Using continuous wavelet transform to preprocess the spectral data effectively improve the accuracy of the maize canopy chlorophyll density estimation model.