Northwest Territories Geological Survey

In northern boreal ecosystems, wildfire is the most important natural disturbance in controlling ecosystem structure and function. With recent increases in both the extent and severity of wildfires in some regions of boreal North America, the regional response of carbon pools to increased wildfire disturbance remains poorly understood. Here, we quantify the initial response and long-term recovery of aboveground and belowground carbon pools to wildfire in three distinct regions of the Northwest Territories, Canada, including the taiga plains (n=356), taiga shield (n=190), and Sahtu (n= 10) regions. We measured and analyzed carbon pools using a space-for-time substitution approach across approximately 1,270 km2. Stand age ranged from 1 – 275 years since last fire, and stands were dominated either by black spruce (Picea mariana) or jack pine (Pinus banksiana). Our results show that mature stands in the shield on average have shallower organic soil depths (13.7±2.3cm) compared to the plains (26.0±1.9cm). In the plains ecoregion, fire reduced soil organic layer depths by 84% in dry stands, 44% in intermediate stands, and 9% in wet stands. While wet stands lose less soil organic matter during combustion, they also recovered more quickly. By working across large environmental gradients of fire history, forest hydrology, and vegetation dominance, our field measurements will be helpful in validating remote sensing products related to wildfire as well as process-based modelling of both the short- and long-term consequences of wildfire for ecosystem carbon behaviour.