Effects of Narrow Linear Disturbances on Light and Wind Patterns in Fragmented Boreal Forests in Northeastern Alberta

Abstract

Forest fragmentation threatens forest biodiversity and ecosystem function. One of the concerns relates to increases in edge effects, which among other things affects the forest microclimate that influences the distribution and behavior of species. In Alberta, Canada, boreal anthropogenic disturbances from in situ oil exploration are increasing forest fragmentation, especially in the form of exploratory well pads and seismic lines (i.e., linear forest clearings created during the exploration phase of oil extraction). Dissection of these forests by seismic lines has the potential to change local patterns in wind and light, and thus may alter forest communities. Although alterations of these abiotic conditions are likely, the magnitude of these changes is unknown, particularly the effects of changes in the width and orientation of linear disturbances. Here we investigated changes in light and wind on seismic lines compared to that of adjacent undisturbed forests and nearby cleared openings. Specifically, we examined how seismic line characteristics (i.e., line direction, line width, and adjacent canopy height) altered local responses in these abiotic conditions. Generalized Linear Mixed Effect models predicted a 2-fold increase in average light intensity and maximum wind speeds, and a 4-fold increase in average wind speeds on seismic lines compared to adjacent forests. These changes did not approach the conditions in large openings, which compared to forests had a 3-fold increase in average light intensity, a 16-fold increase in average wind speeds, and a 4-fold increase in maximum wind speeds. Line width and orientation interacted with adjacent forest height altering the abiotic environment with wider lines having a 3-fold increase on maximum wind speed. We conclude that even localized, narrow (<10-m wide) forest disturbances associated with oil sands exploration alter forest microclimatic conditions. Recent changes in practices that reduce line width as well as promoting tree regeneration, will minimize the environmental effects of these anthropogenic disturbances.

Distribution of Cranberry Blue Butterflies (Agriades optilete) and Their Responses to Forest Disturbance from In Situ Oil Sands and Wildfires

“…Openings in the forest canopy, such as seismic lines, allow early seral plant species, on which butterflies rely for nectar sources and larval host plants, to increase in abundance and diversity [53], and thus seem to benefit the whole butterfly community [16]. On the other hand, both seismic lines and well pads affect abiotic conditions by increasing illuminance and wind speeds [54]. While abiotic conditions in seismic lines are more similar to those of undisturbed forests, the effects of well pads are more substantial, with 16-times higher average wind speed, 4-times higher maximum wind speed, and 3-times higher illuminance [54].…”

“…On the other hand, both seismic lines and well pads affect abiotic conditions by increasing illuminance and wind speeds [54]. While abiotic conditions in seismic lines are more similar to those of undisturbed forests, the effects of well pads are more substantial, with 16-times higher average wind speed, 4-times higher maximum wind speed, and 3-times higher illuminance [54]. These conditions may negatively affect cranberry blues, particularly due to wind speed that may limit the movement of these small (~25 mm wingspan) butterflies.…”

Short‐term effects of wildfire in boreal peatlands: Does fire mitigate the linear footprint of oil and gas exploration?

“…Given the very nature of OG exploration and extraction practices, in‐situ landscapes have become heavily dissected (as defined by Jaeger [2000]) by a network of thousands of kilometers of linear features (seismic lines, pipelines, access roads, etc. ), and other local disturbances (exploration pads, well‐sites, and other industrial infrastructure; Timoney and Lee 2001, Pasher et al 2013, Pattison et al 2016, Stern et al 2018). In many cases, this extensive footprint has shown little natural recovery (Revel et al 1984, Lee and Boutin 2006, Jorgenson et al 2010, Finnegan et al 2018b), becoming a prevalent and persistent landscape feature, with important implications on various ecological properties (e.g., carbon dynamics, permafrost, and hydrology; Strack et al 2019, Williams et al 2013), and the abundance, composition and distribution of many taxa (Hebblewhite 2017, Finnegan et al 2018a, Fisher and Burton 2018).…”

Effects of Fire Severity and Woody Debris on Tree Regeneration for Exploratory Well Pads in Jack Pine (Pinus banksiana) Forests

“…Others have estimated the dispersal distance for jack pine seed is roughly 2-3-times the parent tree height [10] with jack pine starting to develop seeds as early as five-years of age when in good conditions [45,46]. Seed dispersal distance may be larger on exploratory well pads as some exploratory footprints, such as the connecting seismic lines, are known to increase wind speeds and dispersal in other plants [47,48]. Other potential seed sources on exploratory well pads include the cones within the residual woody debris left post-construction, five years prefire, although viability of these seeds may be low.…”