The Role of Lichens in Boreal Tundra Transition Areas

Abstract

The importance and distribution of spruce-lichen in northern Canada is described and fire is documented as being centrally im- portant to the ecology of these woodlands. Thus the cladonia (C. stellaris (Opiz) Pouz. & Vezda) woodland simply represents a long-term phase during the recovery sequence following fire, leading ultimately, although rarely, to a closed canopy spruce woodland. The existence of a second lichen type in Canada is described and the possible widespread occurrence of this stereocaulon (S. paschale (L.) Hoffm.) woodland north of latitude 600N in the Northwest Territories is discussed. Excessive grazing by caribou is thought not to be an important factor in the ecology of this type. The slow development of the Stereocaulon paschale surface is correlated with the very extreme surface microclimate of burned at this latitude. Although the pattern of net photosynthesis activity in Stereocaulon is closely adapted to the less stressful microclimate of the developing woodland, soil nutrients, pH and snow depth interactions are probably also involved in the ecology of this species.