Assessing the cumulative impact of wildland fires and seismic lines disturbance on peatlands in Northern Alberta.

Abstract:

Many peatlands in Alberta exist within a sub-humid climate where evapotranspiration often exceeds precipitation during most years. With increasing atmospheric warming and drying, these ecosystems are close to reaching their hydroclimatic limit and are becoming more susceptible to wildland fires exacerbated by carbon stored in soils. The region is also fragmented by seismic lines used for oil and gas exploration since the 1960s, causing soil compaction which makes it difficult for water to penetrate into peatland soils, thereby changing both the soil moisture and thermal regime. Since seismic line disturbance is relatively recent, the long-term impacts of seismic lines on ecosystem vegetation succession within peatlands is not well known. Thus, the combined effects of fire, climate change, and anthropogenic disturbances may support fewer boreal peatlands in Alberta with a decreased carbon sequestration potential and have implications on northern communities. The objectives of this research is to determine the impact of (i) wildland fire, (ii) seismic line age and width, and (iii) combined effects of these disturbances on shrub and conifer regeneration trajectories in a boreal peatland/ upland forest chronosequence of 8 years, 18 years, 30 years and 38 years since fire. To answer these objectives, we use field measurements to evaluate the utility of multi-spectral airborne lidar data collected in August 2020 to identify deciduous shrubs and conifer trees found along seismic lines and peatlands in the chronosequence. The study area includes burned and unburned sites near Fort McMurray that were burned in 1982, 1990, 2002, and 2011. For validation purposes, vegetation height and genus were measured coincident with the lidar survey along burned and unburned seismic lines. We hypothesize an increase in deciduous species along seismic line edges compared to conifers within peatlands, due rapid recovery after wildland fire, especially on unmolded lines. Conifers such as black spruce have a slower growth rate which is further impacted by flattening of the peatland microtopography and loss of suitable microsites. Hence, this study is significant in understanding which ecosystems are more and less resilient to seismic line disturbances and have an improved understanding of post-fire succession trajectories.