Enhanced vulnerability to fire by Pinus densiflora forests due to tree morphology and stand structure in Korea

Why do fires occur more frequently in Pinus densiflora forests in Korea, and why is the related damage more severe on such sites? We assumed that the reasons stem from characteristics of the tree species, including their combustibility, morphology and stand structure. Investigating both P. densiflora forests and the less vulnerable Quercus variabilis forests along the Korean eastern coast, we determined that, in spring, when fires are most frequent, the extremely flammable moisture content of fine fuels (6%) is not significantly different between the two types and the fine fuel load is much greater in the Q. variabilis forests. The P. densiflora forests retain more ladder fuel due to the greater coverage and density of their shrub layers in addition to their dead branches from lower on their boles and thinner barks, which enable fires to spread vertically with greater tree withering. Thus, when one considers all of these factors in combination, the following conclusions become apparent. First, in the initial ignition phase of fire, P. densiflora forests are more vulnerable due to their combustion characteristics. Second, those forests might allow flames to move vertically because of tree morphology and a stand structure that retains abundant ladder fuel. Finally, P. densiflora forests might be vulnerable to massive blazes because of their vast contiguous nature, especially in that region of Korea.