使用高光谱仪ASD Field Spec在波长范围400～1 000 nm内, 采集有机质含量水平不同的土壤反射光谱数据, 之后求取一阶导数(一阶导数光谱）并进行小波去噪; 通过数值积分计算、 相关分析, 从去噪后的一阶导数光谱中提取吸收面积表征有机质含量变化。 结果显示: (1)土壤一阶导数光谱中含有大量噪声, 致使光谱曲线轮廓和有机质的吸收特征难以识别。 (2)当小波分解层数J=3时, 小波去噪在平滑土壤一阶导数光谱曲线的同时, 较好的保持了曲线上多个敏感波段的光谱响应特征。 (3)从去噪后的一阶导数光谱中提取的吸收面积S(538, 586)与有机质含量的相关系数为－0.876 3, 较好的反映了土壤有机质含量的变化情况, 可以用于土壤有机质含量测算。

The hyperspectral reflectance of soil was measured by a ASD FieldSpec within 400~1 000 nm.Next, its first derivative of spectra were acquired and de-noised by the threshold de-noising method based on wavelet transform. From the de-noised derivative spectra, absorption areas used as indicatoresas for soil organic matter content were acquired by numerical integration. Results show that: (1) Because of much noise, it is difficult to identify spectra contour and features in the first derivative of soil spectra resulting from different organic content levels. (2) When the scale of wavelet decomposition was 3, the threshold de-noising method based on wavelet transform can keep the balance between smoothing curve and holding spectra features. (3) Absorption area S(538, 586) is extracted from de-noised first derivative of soil spectra, and the coefficient of correlation between it and organic matter content is 0.896 3.