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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]

• • Bryophytes regenerated well on low impact seismic (LIS) lines in boreal uplands. • • Feathermoss increased on LIS lines over 5 years from 25 % to 90 % • • Vascular plants did not show strong signs of regeneration over 5 years. • • Edge effects into the forest similar for herbaceous plants over 5 years. • • Succession on LIS lines follows unique pattern compared other boreal disturbances. As of the mid-1990 s, low impact seismic (LIS) line construction (<3 m wide) became common practice in western Canada and replaced construction of wider (5–10 m) conventional seismic lines, with the intention of mitigating the known negative environmental impacts (e.g., severe soil damage and minimal vegetation recovery) of these long, narrow corridors used by the Oil and Gas (O&G) industry for exploration. Though the apparent disturbance severity on LIS lines is lower compared to conventional lines and it is expected that succession would proceed more readily towards the conditions resembling pre-disturbance forested state in the upland boreal, there is little scientific evidence that supports this. Here, we assess environmental conditions, successional trajectories and potential edge effects extending into the adjacent forest from the LIS line edges three (2014) and eight (2019) years after their construction in 2011, in the southern upland boreal forest of Swan Hills region in northwestern Alberta, to determine if active restoration measures should be recommended. Soil moisture and light were higher on the lines compared to the adjacent forest. Bryophytes (particularly feathermosses associated with late-succession forests) recovered well within eight years of disturbance (attaining nearly 90 % cover in 2019, from a relatively low cover (∼25 %) on the lines in 2014, compared to ∼ 80–90 % in the adjacent forest in both years), while the shrub and herbaceous layers recovered minimally, and tree species were still mostly absent on these lines. Herbaceous species also had a lower cover in the ∼ 2 m zone away from the line edges compared to the interior 75 m away, indicating edge effects in both years. Our results indicate that LIS lines appear to possess a unique combination of similarities and differences to other common boreal disturbances (fire, harvest), resulting in the equally unique successional trajectories that do not generally follow patterns known to occur in upland boreal forests. Long-term monitoring is imperative to determine whether LIS lines will eventually return to the pre-disturbance conditions or whether human intervention will be required to promote the growth of the canopy cover, especially as they constitute part of the habitat for Woodland caribou, an important threatened wildlife species. [ABSTRACT FROM AUTHOR]