Plant Functional Trait Approach to Assess the Persistence of Seismic Line Footprint in Boreal Peatlands of Alberta, Canada

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Anna Dabros
Kellina Higgins
Kierann Santala
Isabelle Aubin
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The Canadian province of Alberta is densely dissected by seismic lines - linear disturbances used for oil and gas exploration. Natural recovery of seismic lines to pre-disturbance treed conditions in boreal ecosystems is generally slow, and persistence of seismic lines is particularly notable in peatlands, including treed bogs. A functional trait approach can help understand the mechanisms that drive community composition and structure following a disturbance. We explored the role of environmental filters (soil moisture, soil temperature, light, and growing substrate) on vascular species composition and functional community structure on seismic lines in a treed bog near Peace River, NW Alberta. We investigated successional trajectories on seismic lines constructed between 1951 and 1986, and the impact of seismic line orientation (N-S and E-W). We also compared taxonomic and functional trait composition of plots on seismic lines, at the line edges, and in the adjacent treed bog, 75 m away from the edge. We found no differences in plant species and functional trait composition based on the seismic line age and line orientation, confirming that seismic lines are not following the expected successional trajectories frequently observed in boreal ecosystems after other disturbances such as logging or fire. Taxonomic and functional composition were different on seismic lines compared to the line edges and interior treed bog, further supporting that the lines are different from the pre-disturbance conditions. Seismic lines had a few trees, received more light, and were wetter, with an abundant deep layer of waterlogged Sphagnum, whereas the adjacent treed bog had a dense mature overstory and was drier with a higher cover of feathermoss. Seismic lines included primarily shorter species with extensive lateral expansion, which is consistent with a high abundance of low ericaceous shrubs on the lines. Dominance of ericaceous shrubs likely also played a role in low presence of herbaceous species on the lines, which is related to the low presence of hemicryptophytes, compared to the adjacent treed bog. It is unlikely that the historic seismic lines in treed bogs of Alberta will follow expected successional trajectories over the next decades without outside intervention. However, better understanding of the mechanisms that control ecosystem functioning based on taxonomic and functional community composition observed on seismic lines can inform restoration and mitigation measures needed for seismic line recovery.