seismic line sampling - sdw.enr.gov.nt.ca
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SEISMIC LINE SAMPLING NWT SEISMIC STUDY
PREPARED FOR:
Environment and Natural Resources Box 7, 149 McDougal Road
Fort Smith, NT X0E 0P0
SEISMIC LINE JUNCTION IN THE DAHCHO AREA AT 10 V 565564 6760606
PREPARED BY:
DAVID POLSTER, M.SC., R.P. BIO. POLSTER ENVIRONMENTAL SERVICES LTD.
6015 MARY STREET DUNCAN, BC, V9L 2G5
MAY, 2013
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1.0 INTRODUCTION
Seismic lines create a disturbance over broad areas of the landscape. As they recover the ecological
consequences of that disturbance may diminish, but this may take many decades. Understanding the
ecology of recovery processes, including the factors that may enhance or retard recovery rates as well as
the effects of seismic lines at various stages of recovery on the biota (plants and animals) of the area, is
essential for the understanding of the cumulative effects of seismic activity. This brief report presents a
summary of work that was undertaken during a field inspection of Sahtu and Dahcho sites conducted
March 24th
to 30th, 2013. In addition a synopsis of the sampling implications of meetings that were held
in Calgary on April 8th to 11
th, 2013 is provided. This report builds on a report prepared by Polster
Environmental Services Ltd. (PES 2013) that presents the proposed sampling design and data analysis
for the seismic recovery study.
2.0 STUDY METHODS
The seismic recovery study design was developed to provide a scientific basis for the determination of
recovery processes leading to establishment of a foundation for the assessment of cumulative impacts of
seismic lines. As such, study methods that have been widely used in British Columbia to describe
ecosystems were adopted (Luttmerding et al. 1990). Sampling design will provide paired plots with one
plot on the seismic line and one plot in the surrounding undisturbed vegetation. This allows an
assessment of the level of floristic recovery that has occurred on the lines. In addition, sampling a
diversity of stand types provides a foundation for the development of a variety of recovery trajectory
theories. For instance, sampling a line that passes through a Black Spruce – Labrador-tea – Sphagnum
forest where the line has cut through the insulating layer and exposed the permafrost to melting shows
how a retrogressive succession occurs (going from a closed forest to open water). Similarly, sampling
this same forest where the insulating layer has not been removed and only the trees have been removed
shows how a line that is clearly visible from the air may be floristically similar to the surrounding area
with only a structural difference (tree size). The sampling methods have been selected to allow these
various patterns to be teased from the data.
Selection of sampling sites can be restricted due to the inability to land a helicopter. A study to find
suitable landing sites was undertaken in late March, 2013. This study was based on the use of geo-
located pdf images of Landsat images that could be shown on an iPad® with a GPS tracking system in
real time so that potential landing sites could be marked. Photograph 1 shows an image of the data that
was collected in the Dahcho area. Sampling sites (238 sites) were identified for the Dahcho area
(Photograph 1) as well as 3 sub-areas within the Sahtu area (177 sites; 132 sites and 66 sites). For each
point, the UTM coordinates of the helicopter at the time of point placement were recorded. In addition,
notes on the specific site conditions were recorded with the point. For instance, notes for the site shown
in the photograph on the cover of this report might record that there is a junction where a helicopter
could land as well as several different vegetation types that could be sampled. Data files (.gpx files) for
the different areas sampled are provided with this report. These can be queried to determine the UTM
coordinates and the notes specific to that site.
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Sampling designs were discussed and decided at a meeting of technical experts held in Calgary, Alberta
from April 8th
to 11th, 2013. The meeting was conducted with the intention of providing a platform
where technical information could be exchanged and where the direction of future studies could be
determined. A number of important sampling considerations were discussed at this meeting. The
results of these discussions have been incorporated into the design of the current study and are presented
below.
Photograph 1. Potential landing sites within the Dahcho area. The UTM Coordinates of each point as well as
pertinent notes about the site have been recorded.
3.0 RESULTS AND DISCUSSIONS
The Describing Ecosystems in the Field (Luttmerding et al. 1990) sampling and data analysis
methodology has been used for decades in British Columbia. In addition, these methods were used in
the three Yukon seismic studies described in Polster (2010). These methods have allowed large areas to
be efficiently sampled and the data analysed to provide some interesting insights into recovery
processes. These methods should be used for future studies in the NWT to allow data to be compared
and combined if appropriate.
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In addition to the vegetation data collection, information on the wildlife, forests and soils should be
collected. Depth to permafrost (where applicable) appears to be an important criteria for determination
of recovery trajectories. Similarly, the general conditions of the soils (organic or mineral) should be
collected at the time of sampling. Forestry data as per the NWT forms should also be collected. These
are similar to the methods used in the Yukon.
Information on wildlife use of the site being sampled will help to determine the role of seismic lines at
various stages of recovery. A simple measure of browse use has been developed by the BC Ministry of
Forests (Forest Practices Branch) and is shown in Figure 1. This simple assessment can be used to
document the wildlife use of sample sites where browsing is present. Since the species will be
documented as part of the vegetation study, adding in a browse component will be relatively simple and
will provide a level of data that can be incorporated with the vegetation data analysis (much like the
permafrost depth).
Figure 1. Browse use classes from BC Ministry of Forests and Range, 2005
4.0 CONCLUSIONS
The development of sampling procedures as well as the locations of potential sample sites has been
prepared. These procedures are in common use elsewhere, although combining them in a single study is
not widely conducted. However, by combining the sampling to cover vegetation, wildlife, forestry and
soils, the data that is generated can used to create a model of seismic recovery that will be relatively
resilient. Understanding how these attributes of seismic line recovery interact (e.g. vegetation/forests
and soils vs. wildlife use) will allow projections of cumulative impacts to be based on sound science. It
is clear that seismic lines can remain on the landscape for decades. However, the relative ecological
impacts of the lines are less clear. The methodology described in this report will provide information
that can help to elucidate this complex interaction of biophysical conditions and to provide a context
onto which the social aspects of seismic recovery can be overlain.
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REFERENCES CITED
BC Ministry of Forests and Range. 2005. Range Effectiveness Evaluations 2004. Part 2. An Evaluation
of Rangeland Health and Effectiveness of Plant Residues in Protecting Resource Values. Doug
Fraser. Range Practices Specialist. Forest Practices Branch. Ministry of Forests.
Luttmerding, H.A., D.A. Demarchi, E.C. Lea, D.V. Meidinger and T. Vold. 1990. Describing
Ecosystems in the Field 2nd
Ed. MOE Manual 11. Ministry of Environment. Victoria, B.C. 213
pp.
Polster, D.F. 2010. Ecology of Yukon Seismic Lines: Vegetation recovery processes. Unpublished
report prepared for Yukon Energy, Mines and Resources by Polster Environmental Services.
November 2010.
PES. 2013. Sampling Design: NWT Seismic Line Recovery Study. Unpublished report prepared for
Environment and Natural Resources, NT Government by Polster Environmental Services Ltd.
January, 2013.
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