## 3 Results and Discussion
### Comparison of Spectral Curves for Different Fire Severities  
As shown in Figure 6, the comparison of spectral curves for different fire severities in the post-fire image reveals that, in terms of mean values, a clear separation exists between different fire severities in the near-infrared range (740 nm-1341 nm). However, spectral overlap was observed in the visible-near-infrared range (396 nm-714 nm), the shortwave infrared range (1442 nm-1779 nm), and the range (1947 nm-2468 nm), with the reflectance peaks of the unburned areas in the first two spectral ranges extending into the burned areas, leading to smaller differences. In terms of spectral trends, the spectral curve of unburned areas closely followed the typical vegetation spectral variation pattern. In the visible range, a reflectance peak was observed in the green band (560 nm) due to chlorophyll pigments, and absorption valleys were present in the blue band (480 nm) and red band (660 nm). In the near-infrared range, a reflectance peak was observed between 740 nm and 1341 nm due to internal cellular structures of the leaves. In the shortwave infrared range, reflectance peaks occurred at 1644 nm and 2199 nm due to the leaf moisture content. In contrast, the spectral patterns of burned vegetation were disrupted by fire disturbance, with varying degrees of damage to the typical vegetation spectral variation. No distinct peaks or valleys were observed in the visible range for the burned areas. The reflectance peak in the near-infrared range was reduced, the slope between the red and near-infrared bands was flattened, and there was some increase in the shortwave infrared range. In summary, the greatest difference in mean spectral values for different fire severities was observed in the near-infrared to shortwave infrared range (740 nm-1341 nm). The most noticeable spectral variation trend occurred in the red to near-infrared range (679 nm-757 nm). As shown in Figure 7, the spectral curve comparison of different fire severities in the pre and post-fire images reveals that the mean spectral values and variation trends for different fire severity areas before the fire are similar, generally following the typical vegetation spectral change pattern. Except for the unburned areas, where the mean spectral values increase in the green to shortwave infrared range (516 nm-2417 nm, excluding the removed bands), the spectral mean values in the burned areas decreased across different fire severity levels. Specifically, the spectral mean values in the visible to near-infrared range (396 nm-714 nm) were higher after the fire, while those in the near-infrared to shortwave infrared range (722 nm-2468 nm) were higher before the fire. The greater the fire severity, the more pronounced the decrease in spectral mean values. The most significant differences  
Figure 6: Comparison results of spectral curves for different fire severities using the post-fire ZY1 AHSI image. Note: The ’pre-fire or post-fire’ and ’severity levels’ are connected by an underscore (\(\_\)) to represent the spectra or spectral differences in the respective severity levels in the period, similarly for subsequent cases. in both spectral mean values and trends between the pre- and post-fire images occurred in the near-infrared range (757 nm-1341 nm). Moreover, the spectral mean values of unburned areas were relatively higher after the fire, likely due to the increased chlorophyll content in vegetation during the growing season, which enhances reflectance in the green to near-infrared range (516 nm-740 nm). In the near-infrared to shortwave infrared range (740 nm-1341 nm), the difference was caused by variations in the internal cell structure of newly grown leaves compared to older leaves, leading to multiple reflection differences.