Habitat preference, growth form, vegetative dispersal and population size of lichens along a wildfire severity gradient

Species' responses to disturbance depend in part on their life histories. In this study we examined the association between post-fire distribution and a few life history characteristics (growth form, presence of soredia, habitat preference and population size) for lichens in the Boundary Waters Canoe Area Wilderness in northern Minnesota, U.S.A. We used sample plots set up two months after a wildfire in 1995, and defined fire-vulnerable and fire-favored species as those over- or under-represented in unburned versus burned plots eight years after the fire. Fire-vulnerable species (30% of species) were characterized by shade preference and crustose growth form. Fire-favored species (7% of species) were characterized by preference for dead wood. Rare species were over- represented in unburned plots. Species observed on charcoal, indicating post-fire colonization, were associated with high regional population size, estimated by sample plot frequency. These results suggest that habitat association and its mechanisms, along with population size, are presumably important predictors of species-specific response to disturbance, such as fire, for lichens in the boreal forest.