Fuel Loads and Peat Smoldering Carbon Loss Increase Following Drainage in a Forested Boreal Peatland

We aimed to assess how peatland drainage altered the spatiotemporal variability in forest cover, aboveground biomass, and tree productivity and how these changes related to the spatial variability in peat burn severity. We studied a black spruce and birch dominated boreal peatland in Parkland County, Alberta, Canada, which was drained in 1987 and burned in 2021. Using remote sensing techniques (historical imagery and LiDAR), we determined that forest cover increased by 180% following drainage and aboveground tree biomass decreased from 26.1 kg m⁻² adjacent to the nearest drainage ditch to 2.8 kg m⁻² 95 m away from the nearest ditch. Field surveys and a LiDAR-based analysis were conducted to measure the spatial variability in peat burn severity. Drained peatland margins experienced the greatest peat burn severity with a mean depth of burn of 26.9 ± 12.6 cm (18.2 ± 10.1 kg C m⁻²) compared to natural middles at 15.3 ± 6.2 cm (3.9 ± 2.1 kg C m⁻²), where peat burn severity increased with proximity to ditches and greater aboveground biomass. We present a conceptual model outlining the increases in aboveground and peat fuel loads following drainage and suggest that the area around a ditch that is impacted by drainage, which is commonly assumed to be 30 m, likely increases through time in forested peatlands due to the afforestation feedback. Drained peatlands represent a severe fire risk for communities and fire management agencies. Peatland restoration should be integrated into fuel management strategies to reduce the risk that drained peatlands pose.