Repeated fires in forested peatlands in sporadic permafrost zone in Western Canada

Abstract

Wildfires have a crucial role in northern boreal peatland ecosystems as drivers of ecosystem functioning affecting vegetation composition and biomass, peat accumulation patterns and soil carbon (C) stocks. Northern peatland ecosystems are under pressure due to the climate warming and increasing anthropogenic stress. The frequency and severity of wildfires is predicted to increase in the future, and therefore knowledge on long-term natural fire dynamics and their effect on peatland functioning provide crucial information for peatland management and preservation policies. 
 
To investigate long-term fire history and its effect on peat accumulation and vegetation succession we analyzed macroscopic plant remains and charcoal from peat cores from five peatlands in western Canada. Records of the most recent fire events were derived from fire scars and documented fires in the study area. The regional long-term peatland fire patterns were examined by pooling together macroscopic charcoal records and calculating 100-year moving averages.

All studied sites, except the northernmost one, demonstrated repeated fires throughout the past 1500 years suggesting that fires have been integral part of the peatland ecosystems in Western Canada. Compiled charcoal records indicate a peak in fire activity with highest abundance of charcoal for the period from 1300s to 1550s and decreasing fire activity during the recent centuries. The clear and consistent post-fire increase in the abundance of Sphagnum mosses suggests relatively rapid recovery of peatland ecosystems after burning. The regeneration pattern, where pre-fire vegetation repeatedly re-establishes, suggests that in a long-term perspective fires do not necessarily have negative effect on peatland functioning and peat accumulation. In conclusion, peatlands could remain as effective carbon sinks if their natural state is secured.