## 3 Results
### Post-Blowdown Vegetation Regeneration Process  
From the total of 45 analyzed blowdowns, 10 have recovered to a level within the 95% CI of their pre-disturbance NPV mean within 12 months for both Landsat-8 and PlanetScope NICFI data. Whenever the NPV fractions were detected as recovered in the Landsat-8 time series, they were also detected as recovered in PlanetScope NICFI. The opposite was not always the case; 10 blowdowns were identified as recovered in PlanetScope NICFI but not in Landsat-8, likely due to the lack of image acquisitions from Landsat-8. Furthermore, 25 of the 45 blowdowns did not return to pre-disturbance NPV levels after 20 months of observation. For the 20 blowdowns whose time to recover to pre-disturbance levels was detected in PlanetScope NICFI, the shortest recovery was three months and the longest was 20 months, with a mean of 12.2 \(\pm\) 4.8 months. For the same ten blowdowns in Landsat-8, the average recovery time was similar (14.1 \(\pm\) 3.1 months) to PlanetScope but with a smaller variance, with a minimum of 8 months and a maximum of 15 months. Figure 6 shows the trends in \(\Delta\)NPV for both PlanetScope NICFI and OLI Landsat-8. The start date of each blowdown was determined as the month of the earliest image in which it was detected in either of the two datasets. The trend in NPV fractions in PlanetScope NICFI for all 45 blowdown events is shown in Figure 6A. The trajectory of NPV chronological changes in the PlanetScope NICFI monthly time series was broadly complete and, although fluctuating, showed a generally declining trend. Additionally, many blowdowns did not reach their peak NPV when they were first visible, so NPV did not always fall. This suggests that the extent of damage caused by blowdown events may be underestimated if only the first visible image is used to assess NPV changes. All available Landsat-8 images of blowdowns were included in Figure 6B. Compared to PlanetScope NICFI, the OLI Landsat-8 was not able to provide a consistent \(\Delta\)NPV trajectory with recovery (Figure 6B) due to difficulties in obtaining regular monthly observations. Although a decrease in \(\Delta\)NPV over time can be seen, the details of the chronological change are not clear. In the 15 months analyzed after the blowdown, there was an average of 12.9 available cloud-free PlanetScope NICFI images for all blowdown events, compared to only 5.1 images from Landsat-8. Figure 5: Boxplots of (**A**) \(\Delta\)NPV\({}_{\text{first}}\) (the difference between the average NPV of the first post-blowdown image acquisition and of the pre-blowdown images) and (**B**) max \(\Delta\)NPV (the max \(\Delta\)NPV value among all months post-blowdown). The notch in the boxplots represents the 95% confidence interval around the median. To gain a deeper understanding of the recovery trend of permanent vegetation after blowdown events, we analyzed PlanetScope NICFI images due to limited availability of OLI Landsat-8 images. Upon considering all blowdown events, we observed that the mean \(\Delta\)NPV curve reached around pre-blowdown level at approximately 15 months or more, and about 17 months to fall completely into the 95% CI of the mean pre-blowdown NPV (Figure 7). This recovery time is longer than the average of 12.3 months and 14.1 months required for the NPV to surpass the lower bound of the 95% confidence interval (CI) around the mean of pre-disturbance NPV. Furthermore, the lower limit of the 95% CI of the mean curve decreased to pre-blowdown level at around 6 months, while the upper limit remained above 0 throughout the study period, which is significantly different from the mean curve, indicating substantial differences in the \(\Delta\)NPV curves of individual blowdowns. Figure 6: Changes in \(\Delta\)NPV over time for all 45 blowdowns based on (**A**) PlanetScope NICFI and (**B**) Landsat-8. Figure 7: Changes in \(\Delta\)NPV over time based on PlanetScope NICFI. (Blue line: mean \(\Delta\)NPV values; grey curve: each blowdown event; green shades: 95% CI.)