Canadian Forest Service Publications
Edge influence of low-impact seismic lines for oil exploration on upland forest vegetation in northern Alberta (Canada). 2017. Dabros, A.; Hammond, H.E.J.; Pinzon, J.; Pinno, B.; Langor, D. Forest Ecology and Management 400(2017):278-288.
Issued by: Northern Forestry Centre
Catalog ID: 38722
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Low-impact seismic (LIS) techniques were developed to reduce the environmental footprint of oil exploration. Though relatively narrow (~2–3 m) and constructed with light-weight equipment, these lines cause forest fragmentation, and with their high density and potential edge influence extending into adjacent forest, their impact may be considerably underestimated. We assessed the effects of 3- to 4-year-old LIS lines in upland coniferous sub-boreal forests in northwestern Alberta (Canada) by investigating the distance of influence from the LIS line centre, through the edge and into the adjacent forest on vascular and non-vascular plant species diversity and cover and on several environmental factors. We also assessed whether cardinal orientation of the edge affects influence on plants and environmental factors. Edge orientation had no effect on extent of edge influence on plants or environmental variables, but distance from seismic line edge did. Species diversity of herbaceous plants was lowest from the seismic line edge up to 15 m into the adjacent forest, when compared to mid- (25 m) and far-interior (75 m) forest. In contrast, cover was lower 5 m from the seismic line edge in comparison to far-interior forest, but conditions on the seismic lines did not differ from the seismic line edge or any sampled distance up to 75 m from the edge. Non-vascular species had lower diversity and cover on the seismic lines and along the edges in comparison to any distance away from the edge. There was no effect of distance from the seismic line edge on live woody plants, but deadwood was more frequently encountered near the seismic line edges in comparison to interior forest. Soil temperature was higher on the seismic lines and along the line edges whereas soil moisture on the seismic lines was about twice as high as at the edges and adjacent forest. Seismic lines and edges also received more light than the forest near the edge, but not more than the far-interior forest. With edge influence detectable up to 15 m from edge 3 to 4 years postconstruction, long-term and regular monitoring of LIS lines is recommended, as active management and remedial reclamation actions might be required to bring the recovery of these disturbances on the right trajectory.
Plain Language Summary
Seismic explorations are used to locate and determine the depth of oil deposits before their extraction. Seismic lines created during seismic explorations are among the most common linear disturbances found in Alberta and thus one of the main causes of forest fragmentation, which poses a serious threat to diversity in the landscape. Historically, seismic line construction involved wood clearing of 5- to 10-m-wide strips (often many kilometers in length) using heavy machinery. Recently, low impact seismic (LIS) techniques have been developed and implemented to reduce the environmental footprint of oil industry explorations. The extent of ecological effects of these linear disturbances, however, is little known. We looked at how far into the forest the effect of these lines (the edge effect) reached and how it affected the diversity and abundance of plants. We also assessed whether the orientation of these lines influenced plants and environmental factors. Edge orientation had no effect on extent of edge effects on plants or environmental variables, but distance from line centre and line edge did. Diversity and abundance of herbs were reduced on the lines and near the edges and was detectable as far as 75 m away from the line and into the adjacent forest. Reduced light reaching the ground near the line edges, caused likely by denser tree canopies near the edges, probably contributed to reduced presence of low-to-the-ground herbs. Diversity and abundance of mosses and lichens was also reduced, but only on the lines and at the edges. Natural regeneration of the lines is less likely to occur if the main sources for that regeneration (seeds, means for vegetative reproduction) were reduced in the areas near line edges and disturbances. We recommend long-term and regular monitoring of LIS lines, as active management and remedial reclamation actions may be required to promote the recovery of these disturbances.