Objective Using Landsat images to study the identification and vegetation restoration of burned areas based on dNBR (difference Normalized Burned Ratio) and EVI (Enhanced Vegetation Index).

Method Taking the 1987 forest fire happened in the northern region of Daxing’an Mountain as the research background, based on land classification and dNBR values, the burned areas were identified and extracted by K-means method, and were classified into light, moderate and severe fire intensity area; and then, based on the EVI values of the burned areas, the vegetation restoration characteristics in the burned area from 1987 to 2019 were analyzed by using the methods of one-way linear regression, Mann-Kendall and Theil-Sen median, so as to explore the vegetation restoration process of burned areas in Daxing'an Mountains.

Result Based on dNBR, the total burned area was 1291.68 hm², and the proportions of light, moderate and severe burned area were 45.70%, 32.16% and 22.14%, respectively. The severe burned area was distributed in the center of the burned area, and the fire intensity gradually decreased from the center to the outside. The impact of forest fire on EVI was obvious, the EVI values of light, moderate and severe burned area decreased by 30.0%, 48.3% and 68.8%, respectively. After the forest fire, the EVI values of burned areas gradually increased with the vegetation recovery, and their differences with the controlled area were gradually reduced. The recovery rates of EVI on different burned forest lands were severe > moderate > light, and the EVI value of shrub grassland was the same as that of the controlled area 2 years after the forest fire. During the process of vegetation restoration in the burned area, the EVI mutation points of forest land were less than that of shrub grassland, EVI mutation points of light burned area were less than those of severe and moderate burned area, and the mutation time of controlled area were all lagged behind that of burned area.

Conclusion dNBR can be used to extract the burned area and fire intensity. The EVI values of burned area decreased obviously because of the fire, and the decreasing degree increased with the increase of fire intensity. In the process of vegetation restoration, the EVI values of the burned are increased gradually; the light and moderate burned forest land recovered to normal vegetation state 6−8 years after the fire, and the severe burned area returned to normal vegetation state about 14 years after the fire, while the burned shrub grassland recovered to normal 2 years after the fire. The ecosystem in the burned area is fragile and vulnerable to environmental conditions. Therefore, the fire intensity and natural environment are the main factors affecting the vegetation restoration of the burned area in Daxing'an Mountains. The results can provide some data support for vegetation restoration and management in Daxing'an Mountains.