Reindeer lichens, therefore, can colonize and become a dominant floral element on soils too shallow or sterile to support higher plants, provided that humidity is sufficently high for lichen growth and temperature is sufficently low to inhibit competitors. C. mitis generally the first reindeer lichen to become established in postfire white spruce and black spruce stands. It dominates for 30 to 40 years and is then replaced by others such as C. alpestris and C. rangiferia . Can survive cool fires but are almost always killed by severe fire. In the black spruce zone, lichens generally burn poorly in early morning or near sunset, even on hot days, whereas at mid-day they flare up with almost incredible heat and flame.
Humidity changes at ground level and dehydration appear to be the most likely factors involved.
Fifty percent or more may survive if there is not much organic litter to retain the fire. Recover very slowly after fire. Length of recovery time required varies with species, the extent and intensity of the fires, and site and microclimatic condition, but an average of 40-50 years appears to be a conservative estimate. After fire the first reindeer lichen to become established is Cladonia mitis . The second reindeer lichen phase is generally dominated by C. alpestris , C. rangiferina , or C. arbuscula.