# Remote Sensing of Forest Burnt Area, Burn Severity, and Post-Fire Recovery: A Review
## 4 Results and Discussions
### Monitoring of Post-Fire Forest Recovery  
Quantifying post-fire effects become increasingly significant for understanding how forest ecosystems respond, including vegetation recovery, patterns of succession, ecosystem resilience, ecological impact, and planning forest management [235; 40; 236]. In this respect, RS has been recognized as an indispensable tool for monitoring referestation patterns after wildfire [237; 238; 239; 240; 241]. Among different quantitative techniques, Tasseled Cap [242] and Multitemporal Kauth Thomas transformations [243] are of particular interest to the researchers as they are based on assessing satellite imagery of three key indicators of post-fire vegetation conditions--brightness, greenness, and wetness. Numerous studies have used a comprehensive analysis related to both transformations for mapping changes and disturbances in forests after wildfires [244; 245; 246; 247; 248; 249; 250]. Several studies on post-fire dynamics have been carried out in boreal forest ecosystems using optical sensors. [PERSON] et al. [251] estimated a mean NPP post-fire recovery for North American boreal forests of about 9 years using a 17-year time series of AVHRR NDVI observations. Another study used two NDVI AVHRR 17-year time series datasets to investigate vegetation recovery after wildfire in the boreal forest of Canada [252]. The results indicated that the rate of forest recovery varied in three episodic wildfire years (1981, 1989, and 1995), and that recovery times to preborn levels (5 years or more) were shorter than in previous studies. [PERSON] et al. [253] observed spatio-temporal patterns of the fraction of absorbed photosynthetically active radiation (fAPAR) with the use of the MODIS time series to estimate post-fire dynamics during and two years after a fire event in Siberian boreal forests. Their results indicated that the differences in the fAPAR trajectories are correlated with the forest type, and fAPAR changes are not significantly different among the boreal latitudinal regions. The post-fire regeneration of Siberian boreal forests was studied using a 16-year time series of NDVI and NDSWIR (normalized difference shortwave infrared index) derived from MODIS [35]. The results have proved that more than 13 years are needed for the temporal NDVI and NDSWIR signals to recover fully after wildfire. [PERSON] and [PERSON] [254] used Landsat TM/ETM+ images to estimate forest succession over a 16-year post-fire period in interior Alaska. The study results indicated that patterns of post-fire Alaskan boreal forests are strongly linked to both the types of pre-fire vegetation and BS. In sixteen years after the fire, most of the high BS areas with closed needle-leaf, open needle-leaf, and mixed forest classes shifted to woodland or shrubland [254]. [PERSON] et al. [255] used three spectral recovery metrics derived from an annual Landsat based per-pixel NBR time series to estimate the recovery cycles of Canadian boreal forests. They found that post-fire spectral forest recovery rates have increased during 1986-2011 by 18% in the Taiga Shield East and 9% in the Taiga Shield West of Canada. Many studies of post-fire vegetation responses are based on the discrimination of spectral bands and vegetation indices (mostly NDVI, dNBR, and EVI) by MODIS, Landsat, SPOT, and Sentinel multitemporal imagery in different regions and forest ecosystems of the world [256; 257; 258; 259; 260; 261; 262; 263; 264; 265; 266; 267]. Numerous studies have observed that NDVI has a higher correlation with post-fire vegetation regrowth, leaf area, and biomass than other VI [36; 135; 268]. Severe changes in the ecosystem growth conditions caused by forest fire often result in rapid reforestation processes that can be observed at the regional level with MODIS 250-m NDVI time series data [35; 36; 269; 270; 271; 272]. [PERSON] et al. [273] used MODIS and Landsat TM/OLI data to evaluate forest recovery processes and physiological activity after the April 2000 forest fire on the eastern coast of South Korea.