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Seismic lines—narrow and straight corridors from which overstory has been removed to allow access for oil and gas exploration—are a major human footprint in the boreal forest of western Canada. With slow to minimal recovery of tree cover along these corridors, seismic lines have become a persistent landscape feature affecting connectivity and habitat quality in forested ecosystems, particularly in wetland areas. Soil mounding is a common ground preparation treatment widely applied along seismic lines, with the expectation that it will enhance tree seedling establishment and improve the return of tree cover to disturbed areas. However, much is still unknown about environmental responses following treatment application. In this study, we compared the ground microtopography in treated and untreated seismic lines, as well as the relative elevation between treated and untreated seismic lines with their adjacent treed peatland. The ground elevation in both treated and untreated sites was significantly lower on seismic lines relative to their adjacent treed peatland, with a greater elevation difference in treated areas. Likewise, ground microtopography was orders of magnitude higher along treated areas compared to the natural variation in the adjacent treed peatland. Given the important changes in relative elevation and topography following treatment application, our results suggest the potential for eventual treatment success may be more unpredictable than expected; this may have critical consequences for other ecological properties beyond the restoration goal of tree establishment and return of tree cover. [ABSTRACT FROM AUTHOR]

Boreal peatlands of Alberta (Canada) are heavily dissected by a large network of linear disturbances, including seismic lines used for Oil and Gas exploration. Edge effects resulting from these linear disturbances can increase their footprint and affect wildlife habitat, including the quality and quantity of plant and lichen forage. In 2012, seismic line restoration became a priority in Alberta, under the realm of restoration of habitat of threatened boreal woodland caribou. More accurate understanding of biotic and abiotic interactions leading to edge effects can be important in choosing appropriate restoration practices and prompting natural regeneration. We assessed the extent of edge effects of seismic lines on the adjacent boreal peatland near Peace River, northwestern Alberta. We compared plant and lichen community composition and environmental conditions on seismic lines and along 22 transects, which extended perpendicularly 75 m into the peatland from both lines edges. Soil moisture and light were higher on the lines, but frozen ground was less frequent than in the adjacent peatland. Seismic lines were also subsided by approximately 1.2 cm. Lichens were less abundant in the 2–25 m zone from the edge—indicating edge effects. On the lines, Sphagnum constituted a nearly 100% cover while lichens, trees, herbs, and other bryophytes were less abundant than in the peatland. We demonstrate how knowledge of edge effects on plants and lichens could be applied in assessing caribou habitat quality based on forage availability and predation risk, and how such knowledge could inform restoration practices of seismic lines in peatlands. [ABSTRACT FROM AUTHOR]

Exploration practices for oil sands developments in the boreal forest of western Canada create a network of thousands of kilometers of linear features, particularly seismic lines that dissect these forests posing significant environmental challenges. As wildfire is one of the prevalent stand‐replacing natural disturbances in the Canadian boreal forest, it is an important driver of environmental change and stand development that may contribute to the mitigation of such linear industrial footprint. Here, we evaluate the short‐term cumulative (also known as combined) effects of seismic lines and wildfire on biodiversity and site conditions. One year after the Horse River (Fort McMurray, Alberta, Canada) fire event in the spring of 2016, we compared dissected and undisturbed forests in burned and unburned boreal peatlands, assessing changes in overall stand structure and the responses of a variety of organisms. Soil moisture was significantly higher on seismic lines than in the adjacent forest, suggesting why most of the study sites within the fire perimeter showed little evidence of burning at the line in relation to the adjacent forest. Low fire severity on seismic lines seemed an important driver of local species diversity for ants, beetles, spiders, and plants in disturbed peatlands, resulting in similar species composition on seismic lines both within and outside the burned area, but different assemblages in burned and unburned adjacent forests. Our results suggest that fire did not erase seismic lines; rather, wildfire might increase the influence of this footprint on the recovering adjacent forest. Longer‐term monitoring will be necessary to understand how boreal treed peatlands respond to the cumulative effect of wildfire and linear disturbances. [ABSTRACT FROM AUTHOR]

• Seismic lines in treed bogs are in arrested or alternative state of succession. • Intervention needed for lines to recover along desired successional trajectories. • Tree removal on seismic lines resulted in paludification process. • Dominance of ericaceous species and waterlogged Sphagnum preventes tree recovery. • Functional traits reveal environmental and biological factors limiting succession. 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. [ABSTRACT FROM AUTHOR]