Analysis of Chlorophyll Concentration in Potato Crop by Coupling Continuous Wavelet Transform and Spectral Variable Optimization
Analysis of Chlorophyll Concentration in Potato Crop by Coupling Continuous Wavelet Transform and Spectral Variable Optimization
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DOI：
10.3390/rs12172826
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发表时间：
2020-09-01
期刊：
影响因子：
5
通讯作者：
Sun, Hong
中科院分区：
文献类型：
--
作者：
Liu, Ning;Xing, Zizheng;Sun, Hong
基于光谱技术的叶绿素含量分析对于监测马铃薯作物的生长状况和指导田间精准施氮具有重要意义。合适的数据处理和建模方法可以提高叶绿素分析的稳定性和准确性。为了开发这种方法，我们在2018年通过在分蘖、块茎形成、块茎膨胀和块茎成熟阶段进行田间试验收集了建模数据。基于不同分解尺度（2（1）~ 2（10），Scales 1-10）下的原始反射率、标准正态变量反射率和小波特征，采用偏最小二乘（PLS）算法建立叶绿素分析模型，并采用竞争自适应重加权采样（汽车）算法对模型进行优化。比较了各种模型的性能。尺度3下的WFs与叶绿素浓度的相关性最强，相关系数为-0.82。在模型校正过程中，最优模型为Scale 3-CARS-PLS，该模型是基于汽车选择的Scale 3下的敏感WFs建立的，校正集的最大决定系数（Rc 2）为0.93，最小Rc 2-Rcv 2值为0.14。在模型验证过程中，Scale 3-CARS-PLS模型的验证集决定系数（Rv 2）最大，为0.85，交叉验证均方根误差（RMSEV）最小，为2.77 mg/L，表现出较好的叶绿素浓度预测能力。最后，利用2020年采集的测试数据对Scale 3-CARS-PLS模型的分析性能进行了测量，R-2和RMSE值分别为0. 69和3. 36 mg/L，显示出良好的适用性。因此，Scale 3-CARS-PLS模型可用于叶绿素浓度的分析。该研究为马铃薯叶绿素含量分析提供了重要的支持手段。
The analysis of chlorophyll concentration based on spectroscopy has great importance for monitoring the growth state and guiding the precision nitrogen management of potato crops in the field. A suitable data processing and modeling method could improve the stability and accuracy of chlorophyll analysis. To develop such a method, we collected the modelling data by conducting field experiments at the tillering, tuber-formation, tuber-bulking, and tuber-maturity stages in 2018. A chlorophyll analysis model was established using the partial least-square (PLS) algorithm based on original reflectance, standard normal variate reflectance, and wavelet features (WFs) under different decomposition scales (2(1)-2(10), Scales 1-10), which were optimized by the competitive adaptive reweighted sampling (CARS) algorithm. The performances of various models were compared. The WFs under Scale 3 had the strongest correlation with chlorophyll concentration with a correlation coefficient of -0.82. In the model calibration process, the optimal model was the Scale3-CARS-PLS, which was established based on the sensitive WFs under Scale 3 selected by CARS, with the largest coefficient of determination of calibration set (Rc2) of 0.93 and the smallestRc2-Rcv2value of 0.14. In the model validation process, the Scale3-CARS-PLS model had the largest coefficient of determination of validation set (Rv2) of 0.85 and the smallest root-mean-square error of cross-validation (RMSEV) value of 2.77 mg/L, demonstrating good prediction capability of chlorophyll concentration. Finally, the analysis performance of the Scale3-CARS-PLS model was measured using the testing data collected in 2020; the R-2 and RMSE values were 0.69 and 3.36 mg/L, showing excellent applicability. Therefore, the Scale3-CARS-PLS model could be used to analyze chlorophyll concentration. This study indicated the best decomposition scale of continuous wavelet transform and provided an important support method for chlorophyll analysis in the potato crops.