Fig 1.
Study area with soil sample locations.
Fig 2.
Average reflectance spectra curves and their corresponding standard deviation values (shaded regions).
Table 1.
Statistical characteristics of various soil attributes of soil samples.
Fig 3.
Spectral reflectance of soils with different clay contents from the Ebinur Lake basin, China.
Note: spectral curve (a) denotes the soil sample with 4.543% clay content, 24.172 g kg-1 SOM, 68.547 g kg-1 Na+, and 6.044 g kg-1 Ca2+; spectral curve (c) denotes the soil sample with 0.000% clay content, 25.340 g kg-1 SOM, 3.088 g kg-1 Na+, and 2.808 g kg-1 Ca2+.
Table 2.
Statistics of validation results of the calibration set and the corresponding performance on the validation set of raw reflectance.
Table 3.
Statistics of validation results of the calibration set and the corresponding performance on the validation set of absorbance.
Fig 4.
Clay content models using calibration data set based on raw spectral reflectance data treated by fractional derivatives.
Fig 5.
Clay content models using validation data set based on raw spectral reflectance data treated by fractional derivatives.
Fig 6.
Clay content models using calibration data set based on absorbance treated by the fractional derivatives.
Fig 7.
Clay content models using validation data set based on absorbance treated by the fractional derivatives.
Fig 8.
Coefficients of all bands and the constant term of the spectral reflectance model (a) and the absorbance model (b). Note: VIS denotes visible spectroscopy (400–780 nm), SWNIR and LWNIR denote shortwave and longwave near infrared spectroscopy (780–1100 nm and 1100–2526 nm, respectively). Red line denotes the borderline of range of VIS, SWNIR and LWNIR.