Self-limitation of wildfires compensates for the low resilience of young forest stands in the eastern Canadian taiga

Abstract:

To better understand the relationship between wildfire activity and boreal forest resilience and resistance in the context of climate change we need detailed spatiotemporal data on fire history. The importance of bottom-up drivers (i.e. forest age and previous fire) in the resilience and resistance of the boreal forest against high burn rates has been addressed by several studies, but the mechanisms are not yet well understood. In this study, we undertook an exhaustive spatiotemporal reconstruction of fire activity in the fire-prone eastern Canadian taiga to explore 1) if there has been a change in fire activity during the 20^th century, and 2) if there has been a weakening in the self-limiting feedback due to the lower burn rate of younger forest stands. We reconstructed fire activity for the 1840-2018 time period with 1-year temporal and 2-km spatial resolution along 340 and 300 km-length transects in the northern boreal forest of Quebec, Canada. Our results indicate that the current (i.e. last 30 years) level of fire activity (i.e. fire size, fire intervals and burn rate) is within the range of natural variability of the last 160 years and has remained stable at approximately 2% of the landscape area per year. We also show that the age-related negative feedback has remained strong and most likely compensated for the low resilience of young forest stands. This resistance mechanism has been strong enough to protect landscapes against high fire activity, except in some rare cases where particularly severe weather events resulted in short-interval reburns.