Lichen abundance in the peatlands of northern Alberta: Implications for boreal caribou

Abstract

:In boreal forests, wildfire is a dominant ecological process that, among other things, affects the distribution and abundance of terrestrial lichens. Woodland caribou (Rangifer tarandus caribou) occupying peatland complexes of western Canada rely on terrestrial lichens for winter forage. Understanding the relationship between lichen distribution and fire is therefore important in order to understand caribou ecology. We documented abundance of terrestrial lichens in 73 peatland sites in northern Alberta, all within caribou home ranges. Forty-eight of these had been disturbed by forest fire within the past 70 y, while 25 had not been disturbed for at least 70 y. Peatlands that had not been disturbed for at least 70 y had low lichen cover (average 21.7± 2.1%; range 4.6–54.0%) and lower lichen biomass (660.0± 63.3 kg·ha-1) than other studied boreal areas. However, lichen in sites disturbed by fire appeared to have recovered after only 40 y. This rapid recovery seems to have been mediated by a high growth rate: 4.8± 0.1 mm·y-1. Controlling for the effect of time since fire, lichen cover was inversely related to cover of Sphagnum spp., while growth rates of lichen were positively related to time since fire. Although the re-growth of lichen after fire was rapid in comparison to other systems, we suggest that fire has a strong effect on lichen distribution and hence on the spatial distribution of foraging habitat for Alberta caribou.