Studies on lichen-dominated systems. XIX. The postfire recovery sequence of black spruce – lichen woodland in the Abitau Lake Region, N.W.T.

Abstract

The postfire recovery sequence in spruce woodland growing on drumlins in the Abitau-Dunvegan Lakes area of the Northwest Territories [Canada] is described. Four phases are recognized: yr 1-yr 20, the Polytrichum phase dominated by P. piliferum, with Lecidea granulosa and L. uliginosa as associated species; yr 21 to about yr 60, the Cladonia phase dominated by C. stellaris and C. uncialis; yr 61 to about yr 130, the spruce-Stereocaulon phase with S. paschale forming an almost pure lichen ground cover; after yr 130, the canopy closes and the lichen cover disappears and is replaced by a moss cover forming the final phase, spruce-moss woodland. These phases are confirmed by component analysis. The existence of spruce-Stereocaulon woodland in the area is dependent on cyclic burning. In the absence of fire the spruce canopy would close and the lichen cover would largely disappear. This event is rare in the area with a reburn cycle of about 100 yr. Fire is an important vector in the maintenance of this existence barren-ground caribou winter range.