Soil mounding as a restoration approach of seismic lines in boreal peatlands: implications on microtopography

Abstract

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.

Silviculture treatments hasten seedling growth on seismic disturbances in boreal treed fens

“…Longer‐term tests would increase our understanding of forest recovery on seismic lines in response to silviculture treatments and guide effective implementation for success. As Pinzon et al (2022) noted, such comparative assessments would also allow us to better understand the treatment response of other ecosystem properties that complement tree regeneration and therefore to improve restoration tools as a whole.…”

“…In 2021, the year we started sampling, the mounds had remained intact (Fig. S1), though some settling had occurred (Sutton 1993; Pinzon et al 2022) with average mound heights around 40 cm in both project areas (Echiverri et al 2020; S. Hillson unpublished data). For additional details on mounding specifications in both project areas, see Filicetti et al (2019).…”

“…These artificial hummocks (i.e. mounds) are elevated above the water table, creating a raised planting site designed to increase nutrient availability, drainage, and soil temperature at the rooting zone (Sutton 1993;Londo 2001;Pinzon et al 2022). Enhanced tree recruitment and growth on seismic lines is beneficial to caribou since trees and taller woody vegetation reduce wolf (Canis lupus) movement which may subsequently reduce hunting efficiency and caribou predation (Dickie et al 2017(Dickie et al , 2023.…”

“…In both scenarios, there is limited conifer tree regeneration (Mallik 2003; Finnegan et al 2018; Dabros et al 2022). These conditions are caused by the heavy machinery used to construct seismic lines, which compacts soils and simplifies the natural distribution of hummocks and hollows (Stevenson et al 2019; Davidson et al 2020; Pinzon et al 2022). This simplification or flattening reduces the availability of suitable microsites for tree establishment (Lieffers et al 2017).…”

Inverted Soil Mounding as a Restoration Approach of Seismic Lines in Boreal Peatlands: Implications on Plant and Arthropod Abundance and Diversity

“…It is a silvicultural technique used by the forest industry to establish suitable conditions for tree growth by creating a drier elevated microhabitat and reducing competing vegetation [11,14]. While studies have found that mounded seismic lines have higher tree regeneration [12], other studies have also shown inverted mounding alters peat properties [15], reduces understory cover [16,17], and significantly increases heterogeneity in microtopography compared to adjacent reference fens [18]. However, additional research is needed to further explore the impact of mounding treatments on overall ecosystem properties and biodiversity, especially as the loss in vegetative cover can affect habitat quality (i.e., biophysical conditions) for peatland fauna.…”