Fig. 1. Spatial distribution of winter wheat planting area and the distribution of random sampling points

Fig. 2. Reflectance curves of winter wheat canopy during the dimple occurrence (a) and the stigma elongation (b) under low-temperature treatments
Note: CK is the control, without low-temperature treatment, normal growth; Wavebands of 1 340~1 450 and 1 800~2 050 nm are removed due to strong absorption of water vapor

Fig. 3. Scatter plots showing the measured and predicted yield reduction rates of winter wheat based on the constructed spectral indices B8a-B12 (a), B8-B12 (b) in this study and the published spectral index EVI (c)

Fig. 4. Spatial distribution of the winter wheat predicted yield reduction rates by the constructed spectral index B8a-B12 in this study

Table 1. Published spectral indices and corresponding expressions selected in this study

Table 2. Essential parameters of the selected Sentinel-2 wavebands in this study

Table 3. Correlation analysis between published spectral indices and yield reduction rates of winter wheat

Table 4. Accuracy of linear regression equations of published and constructed spectral indices in this study on predicting the yield reduction rates of winter wheat

Table 5. Accuracy of the linear regression based on the Sentinel-2 broad-waveband spectral indices in predicting the yield reduction rates of winter wheat