Download NWT Seismic Line Recovery Study

SAMPLING DESIGN
NWT SEISMIC LINE RECOVERY STUDY
PREPARED FOR:
Environment Natural Resources
Box 7, 149 McDougal Road
Fort Smith, NT
X0E 0P0
PLOT 4A (LEFT) AT 10 V 471784 6672901 AND PLOT 4 (RIGHT) AT 10 V 471791 6672843.
PREPARED BY:
DAVID POLSTER, M.SC., R.P. BIO.
POLSTER ENVIRONMENTAL SERVICES LTD.
6015 MARY STREET
DUNCAN, BC, V9L 2G5
JANUARY, 2013
1.0
INTRODUCTION
Seismic lines constitute one of the largest cumulative impacts of oil and gas exploration. The recovery
patterns and processes of seismic line disturbances dictate how long these impacts will reside on the
landscape. Understanding how these patterns and processes assort themselves on the landscape and
along lines of different ages allows predictions to be made about recovery rates. In addition,
understanding how the recovery processes operate allows future lines to be established in a manner that
will maximize recovery.
This brief report provides a description of the sampling design and data analysis methods as part of a
larger study of seismic line recovery that was initiated in the fall of 2012. Field work for this larger
study is planned for the summer of 2013; probably late July or early August to achieve the greatest
advantage in terms of weather and plant development (phenology). This report describes the methods
for the field portion and the data analysis portion of this study.
2.0
SAMPLING DESIGN
Sampling will be conducted on a ‘paired plots’ basis. The photographs on the cover of this report show
a pair of plots established just south of the confluence of the Peace River and Liard River in 2008. This
entails establishing one plot on the disturbed area (e.g. seismic line) and one plot in the adjacent
undisturbed vegetation placed far enough from the disturbed area so that there is no influence of the
disturbance on the vegetation of the plot. This allows for relative control of edaphic factors so slope,
aspect, elevation and soil conditions. Edaphic factors will be recorded for each plot. Paired sampling
therefore allows the disturbance to be the major difference between two plots. However it does not
control for permafrost depth as disturbance is often associated with a melting of permafrost while an
undisturbed vegetation cover tends to insulate permafrost. In addition, as vegetation re-grows on the
disturbance, the species composition on and off the disturbance can be compared.
Paired plots will be established in a variety of different locations so that a variety of ecosystems are
sampled. The stands are only sampled once. For instance, landing on a seismic line at the edge of a
wetland adjacent to an upland area allows the wetland to be sampled both on and off the line and the
upland to be sampled on and off the line (see Photograph 1). Going to a second wetland and repeating
this process allows data from the first and second wetlands to be compared floristically as well as the
responses of the wetlands to the disturbances. The upland areas can be compared in a similar manner.
Sampling at each plot will consist of vegetation sampling and forestry sampling and some simple soil
sampling (e.g. depth to permafrost and general soil classification). GPS locations of each plot will be
taken. Forestry sampling will make use of the Government of the NWT tally sheets. Fifty square meter
plots will be used on the disturbed areas and in areas where trees are smaller than 7 cm dbh. In forested
areas detailed tree heights will be measured for three representative trees while the remainder will be
estimated. Diameter tapes will be used to measure tree diameters while appropriately sized prisms will
be used to determine basal area where the use of prisms is suitable. Tree cores of dominant trees will be
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taken to determine stand age. On the disturbed areas where trees are small, a stem “cookie” will be
collected to determine age and growth patterns.
Vegetation sampling will follow the relevé method described by Mueller-Dombois and Ellenberg
(1974). At each relevé (plot) location a full list of species will be compiled. Species will be assigned to
one of four strata, moss, herb, shrub and tree. The tree layer can be split into dominant trees, main tree
canopy and understory trees while the shrub layer can be split into tall shrubs (< 2 m) and low shrubs
(Luttmerding et al. 1990) as appropriate to the stand being sampled. The cover / abundance of each
species will be visually estimated following a modified Braun-Blanquet scale. Species that occur only
once or twice and cover less than 1 percent of the plot area or may occur more times as for seedlings but
still cover less than 1 percent of the plot area will be given an “R” if only once or twice and a “+” if they
are more numerous but still less than 1 percent.
Cody (2000) and Hulten (1968) and the on-line version of the Flora of North America will be used as
the taxonomic standards for vascular plants. Bryophyte taxonomy will follow Vitt et al. (1988).
Voucher specimens will be collected of species whose identity is in question and at least one example of
each species listed. Botanical specimens will be treated following the mythology outlined in Brayshaw
(1973). These will be made available to the GNT upon request.
3.0
DATA ANALYSIS
Vegetation data analysis will follow the Braun-Blanquet method (Mueller-Dombois and Ellenberg
1974). This will consist of a simultaneous sorting of the columns (species) and rows (relevés) in a table
composed of all of the plants found and the relevés (plots) in which they were found. This simultaneous
Q & R sorting creates groupings of the species that occur together and groupings of the relevés with
similar species occurrences. Species-relevé groups are formed. Traditionally species-relevé groups are
named by the dominant species in the group and or the edaphic features that the group defines. For
instance, a group might be called the Carex aquatilis wetland group. Vegetation types are defined by
the presence or absence of the species-relevé groups. Community types tend to be indicative of the
underlying processes that caused the vegetation to establish in the manner it has. In addition, the
relative strength of the species-relevé group within the community type can provide indications of the
trends that are occurring in the vegetation. The accompanying species also show patterns that can be
indicative of the direction the community type is going in. These aspects of the floristics of recovering
seismic lines are important in teasing out the details of recovering seismic lines.
Forestry data will be collected at the same plot locations as the vegetation data. The forestry data will be
analysed to provide stand volumes (where appropriate). Computed volumes will be tallied for all
species combined rather than for individual species. These volumes coupled with stand age will be used
to provide an indication of site productivity (site index) or other pertinent features of the site.
The forestry and vegetation data will be assessed in light of the soils information that is collected to
create a model of natural successional processes that are operating in the region to restore the
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anthropogenic disturbances. It is clear that the human caused disturbances are over-lain on natural
disturbance patterns that significantly influence the vegetation and vegetation dynamics (Photograph 1).
Natural successional processes are also influenced by seed availability, micro-site suitability and a
variety of other factors (Walker et al. 2007). Careful analysis of data that is collected in conjunction
with this study and other similar studies can contribute to an understanding of these processes and hence
the development of strategies to minimize the cumulative effects of oil and gas exploration.
Photograph 1. Fire is an important determinant in the expression of vegetation and vegetation
dynamics. The influence of fire, edaphic conditions (e.g. wetlands, permafrost, bedrock type,
etc.) and human disturbances (seismic lines) creates a complicated mosaic of patterns and
processes.
4.0
RESULTS AND DISCUSSION
Understanding the ecology of seismic line recovery is the first step in defining strategies for minimizing
cumulative impacts of industrial developments. This study will provide valuable data and analysis that
can be linked to similar studies to provide insights into minimizing the impacts of industrial
developments. By applying methods that are the same as those used in adjoining jurisdictions the results
of this study can be extended to other areas and the data from other areas can be applied to this study to
increase the robustness of this study.
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The methods that will be used for this study will allow subsequent sampling to be conducted in the
future either at the same locations as the current study to determine the progress of the recovery or in
new locations to ascertain the recovery conditions in the new locations. Ecosystem recovery processes
are dynamic and the ability to follow recovery patterns over decades will allow insights to be gained that
would not be available in a single sampling session. By using standard sampling methods, the data that
is generated will be available for future studies.
5.0
CONCLUSIONS
The study of seismic line (and associated disturbances) recovery provides a foundation upon which
scientifically based recommendations for the minimization of cumulative impacts can be based. In
addition, an understanding of the ecology of recovery allows treatments to be implemented that can be
used to “move” the vegetation along a desired trajectory. In some cases recovering ecosystems become
“stuck” (Photograph 2) and must be treated in some manner to overcome the successional stagnation
that occurs. In other cases, stands of pioneering species stand in stark contrast to the undisturbed areas.
Pioneering species can be attractive to ungulates such as moose which then encourage predators to use
the lines as hunting areas. This can result in an un-natural pressure on some species such as caribou that
do not benefit from the seismic line, but suffer the detriment of increased predation associated with the
line. Treatments that can successionally advance these sites can be appropriate in these cases.
Understanding the ecology of recovery processes can allow interventions in these situations that address
issues that have arisen since the seismic lines were constructed.
The use of standard vegetation and forestry sampling methods in this study will allow subsequent
studies to access the data. Direct comparisons of the recovery of specific sites can provide insights into
how recovery of new disturbances will occur.
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Photograph 2. This winter road was stripped to the mineral soil. Bluejoint Reedgrass has established
a dense sward that is preventing natural successional processes from operating. Some
significant intervention will be needed to move this area along successionally.
LITERATURE CITED
Brayshaw, T.C. 1973. Plant Collecting for the Amateur. Museum Methods Manual 1. British Columbia
Provincial Museum. Queen’s Printer for British Columbia. Victoria, B.C. 16 pp.
Cody, W.J. 2000. Flora of the Yukon Territory. Second Edition. NRC Research Press. Ottawa, Ont. 669
pp.
Hulten, E. 1968. Flora of Alaska and Neighbouring Territories A Manual of the Vascular Plants.
Stanford University Press. Stanford, California. 1008 pp.
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.
Mueller-Dombois, D. and H. Ellenberg. 1974. Aims and Methods of Vegetation Ecology. John Wiley &
Sons. Toronto. 547 pp.
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Walker, L.W., J. Walker and R.J. Hobbs. 2007. Linking Restoration and Ecological Succession.
Springer. New York, N.Y. 190 pp.
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