Postfire regeneration of plant and soil organic pools in a Piceamariana–Cladoniastellaris ecosystem

Abstract

Postfire recovery of biomass and soil organic pools was measured in a sequence of 10 subarctic lichen woodlands aged from 0 to 140 years. Less than one-tenth of total live biomass combusted at the time of burning. Aboveground biomass combustion of species ranged from nil to over 90% depending on plant stature. Although no trees or lichen survived, shrub mortality (6%) was minor. Developmental phases similar to those in northern hardwood forest were apparent. Reorganization was dominated by shrubs over the first three decades. Aggradation resulted in a fourfold increase in total biomass; it was then followed by a 14% decrease occurring at transition (110–140 years postfire). Breakdown of the burnt lichen mat was rapid (1500 kg•ha−1•year−1) compared with the disintegration of dead wood. Of an initial 40 000 kg•ha−1 in dead boles and branches, 15 000 kg•ha−1 remained 110 years later. Little change in soil humus mass occurred during fire and postfire. Total live and dead organic mass remained relatively constant over the 140 years of recovery. However, the live/dead ratio of organic mass showed a gradual but consistent increase.