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      基于连续小波特征的植烟土壤有机碳含量反演研究

      Inversion of Soil Organic Carbon Content in Tobacco Planting Soil Based on Continuous Wavelet Analysis

      • 摘要: 为实现少量敏感波段下植烟土壤有机碳(soil organic carbon,SOC)含量的准确反演,以曲靖市3个县区的106份植烟土壤样品为研究对象,建立基于小波变换的敏感波段的植烟SOC含量反演模型。结果表明,经过Savitzky-Golay平衡滤波优化后的高光谱数据与SOC含量建立的统计回归模型,其决定系数与优化前相比平均提高了44%;733 nm是对植烟SOC最优的敏感光谱波段,决定系数(R2)值为0.75。对优化后的高光谱反射率数据进行连续小波变换,发现733 nm在1~6尺度下的小波特征反演精度不断增加,到6尺度后趋于稳定,R2值均高于0.80。将优化后的733 nm光谱数据及其在6~10尺度下提取的小波特征作为输入变量,分别构建4种机器学习模型,以随机森林的表现最优,预测模型R2为0.88,均方根误差为1.65 g/kg,相对分析误差为3,运行时间为0.21 s。敏感波段与其高尺度小波特征结合能够实现植烟SOC含量的快速、无损和精确的反演,为SOC含量测定的传感器算法研制提供了参考。

         

        Abstract: To achieve accurate inversion of soil organic carbon (SOC) content in tobacco-growing soil under limited sensitive bands, this study utilized 106 soil samples from three counties in Qujing City as research subjects. An inversion model was used to predict SOC content in tobacco-growing soil based on the combination of sensitive bands and their wavelet features. A model for inverting SOC content based on continuous wavelet analysis was established using a hyperspectral imaging device. Results indicated that the regression model established with the hyperspectral data optimized by Savitzky-Golay filtering showed an average increase of 44% in the coefficient of determination compared to that before the optimization. Using the correlation coefficient method, it was found that 733 nm was the optimal spectral band for SOC in tobacco planting, with a coefficient of determination (R2) value of 0.75. By applying continuous wavelet transform to the optimized hyperspectral reflectance data, it was observed that the inversion accuracy increased with wavelet features at scales from 1 to 10 under the 733 nm band, stabilizing after scale 6, where the R2 value exceeded 0.8. Four machine learning models were developed using the optimized 733 nm spectral data combined with its wavelet features extracted at scales 6 to 10 as input variables. Among these, the Random Forest model produced the best prediction results, with R2 values of 0.88, root mean square errors of 1.65 g/kg, relative prediction deviations of 3, and running time of 0.21 s, respectively. Combining sensitive bands with their own high-scale wavelet features enables rapid, non-destructive, and accurate inversion of SOC content in tobacco-growing soil. These results provide a reference for the development of algorithms for SOC sensors.

         

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