SEISMIC LINE SAMPLING

Transcription

1 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 PREPARED BY: DAVID POLSTER, M.SC., R.P. BIO. POLSTER ENVIRONMENTAL SERVICES LTD MARY STREET DUNCAN, BC, V9L 2G5 MAY, 2013

2 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 24 th to 30 th, In addition a synopsis of the sampling implications of meetings that were held in Calgary on April 8 th 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, This study was based on the use of geolocated 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. -2 -

3 Sampling designs were discussed and decided at a meeting of technical experts held in Calgary, Alberta from April 8 th to 11 th, 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. -3 -

4 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, 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. -4 -

5 REFERENCES CITED BC Ministry of Forests and Range Range Effectiveness Evaluations 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 Describing Ecosystems in the Field 2 nd Ed. MOE Manual 11. Ministry of Environment. Victoria, B.C. 213 pp. Polster, D.F Ecology of Yukon Seismic Lines: Vegetation recovery processes. Unpublished report prepared for Yukon Energy, Mines and Resources by Polster Environmental Services. November PES Sampling Design: NWT Seismic Line Recovery Study. Unpublished report prepared for Environment and Natural Resources, NT Government by Polster Environmental Services Ltd. January,