Characteristics of laboratory-field measured spectra responding to alkalinized soil and conversion

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.