Characteristics of laboratory-field measured spectra responding to alkalinized soil and conversion
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Graphical Abstract
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Abstract
To explore the conditions and rules of conversions between spectra of alkalinized soil under different measure environments, the paper investigated the laboratory-measured and field-measured spectra of alkalinized soil within the Qitai oasis at the northern slope area of Tianshan Mountain in Xinjiang. Based on the analysis of the characteristics of the laboratory-measured and field-measured spectra and physicochemical properties of alkalinized soil at the study spots, the spectral transformation between the laboratory-measured and field-measured spectra were built by multiple linear regression method. The results showed that there was a significant positive correlation between the field-measured spectra and the soil pH value, therefore soil alkalinization could be effectively monitored by using the field-measured spectra. Although the correlation between the laboratory-measured spectra and the soil pH value was insignificant, pH value has the greatest impact on the conversion from the laboratory-measured spectra to the field-measured spectra, followed by the band3 (630-690 nm) and the band2 (520-600 nm) of the laboratory-measured spectra. The laboratory-measured spectra of band1 (450-520 nm) and band4 (760-900 nm) had no significant correlations with the field-measured spectra of the band1 (450-520 nm), band2 (520-600 nm), band3 (630-690 nm) and band4 (760-900 nm). The laboratory-measured spectra were significantly negatively correlated to the soil OM(organic matter), therefore the laboratory-measured spectra had the potential for estimating the quantitative retrieval of the soil OM. The model for laboratory-to-field spectral measurement transformation was less complex with fewer variables, more stability and higher verified accuracy, so it was better than the model for filed-to-laboratory spectral transformation.
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