Bark insulation: Ten Central Alpine tree species compared

Climate-driven increases in frequencies and intensities of wildfires will affect even relatively humid regions such as the Central Alps. During low- to moderate-intensity fires, the resistance of trees to fire is mainly determined by the insulation capability of their bark, which protects underlying tissues from lethal temperatures. However, the knowledge of fire resistance and bark heat insulation of Central Alpine species is scarce. In this study, the bark insulation capability of ten tree species was analyzed by bark surface heating experiments. Heat insulation was assessed by the time required to reach a lethal cambium temperature, linked to bark traits and analyzed with multivariate statistics. Our results revealed a strong overall relationship between bark thickness and cambial temperature responses, but also highlighted the role of bark density in insulating internal tissues. On a species level, additional bark traits, like moisture content, bark surface structure or bark thermal conductivity, contributed to the bark insulation capability. The bark insulation capability thus varied considerably between species. Identifying fire resistant species and knowledge of the traits determining species-specific bark insulation will help to better estimate impacts of fire disturbances and to face the challenge of an increased forest fire risk within the Alpine region.