Impact of tree species composition on fire resistance in temperate forest stands

Numerous factors influence the frequency and intensity of forest fires. Forest fire damage and recovery are influenced by the species composition of the forests. This study assessed forest fire damage vulnerability and forest fire resistance according to the species composition of the forest stand (i.e., the proportion of needle leaf trees (NTs) versus broadleaved trees (BTs) within the forest stand). Following a forest fire event in South Korea, fire damage severity was determined by comparing the pre- and post-event normalized burn ratio obtained from Sentinel-2 imagery. In addition, using 3 m PlanetScope images, we were able to quantify (1) the species composition between NTs and BTs within 30 m of Sentinel-2 pixels and (2) the extent of fire damage and recovery based on changes in phenological timing events and the vegetation index. The results showed that the NT-dominated forest stands underwent more fire damage than the BT-dominated stands, and the differences increased with increasing fire severity. In NT-dominated forest stands, an increase in BT proportion led to a decrease in fire damage, whereas in BT-dominated forest stands, no such correlations were observed. Furthermore, the NT-dominated stands showed more delayed phenological events at the beginning and end of the growing season than the BT-dominated stands, implying slow post-fire recovery in the NT-dominated stands. Our results showed differences in fire damage vulnerability and recovery depending on species composition and demonstrated that the increased fire resistance of BT could improve the fire resistance of a forest stand. These results suggest that considering tree species biodiversity is critical for restoring fire-damaged areas, particularly in the context of climate change, where wildfire frequency is expected to increase.