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Athabasca County No. 12 AB
Canada

Association of postfire peat accumulation and microtopography in boreal bogs


Year: 2005

Abstract:
Peatlands accumulate organic matter as peat because of disproportionate rates of production and decomposition. However, peat accumulation heterogeneity has not been well studied along the microtopographic gradient (hummocks vs. hollows), particularly with respect to fire. Fire affects peatland species composition by differentially removing vegetation and resetting succession, resulting in peat accumulation changes. We examined peat accumulation and microtopography in two historically burned bogs in Alberta, Canada. Measurements of current and historic microtopography were made, and cores were collected along the gradient to identify depth of peat accumulated since fire, as well as to assess properties of the accumulated peat. Current microtopography is significant and correlated with the immediate postfire surface relief. However, differences in the magnitude of variability between sites suggests that differential rates of growth between features are exacerbated between sites and reflected in bog microtopography. Rates of organic matter accumulation, ranging from 156 to 257 g.m^sup -2^.year^sup -1^, were elevated but comparable to published rates of recent accumulation. Organic matter content and accumulation rate were greater for hummocks than hollows at Athabasca bog, but the difference between features diminished at Sinkhole Lake, suggesting that the pattern and properties of peat accumulation and microtopography postfire may be attributable to differences in site conditions.

Oil sands terrestrial habitat and risk modeling for disturbance and reclamation - Phase I report


Author(s): Welham, C.

Year: 2010

Abstract:
The overall objective of this project is to develop a framework that integrates risk management and strategic decision-making to evaluate the impact of disturbance (natural and industrial) on ecosystem products and services, and on habitat availability for terrestrial species in Alberta’s Lower Athabasca planning region. This will include an evaluation of the impact of disturbance (natural disturbance due to insect outbreaks, fire and wind, as well as other industrial and agricultural disturbances), conservation, and reclamation activities associated with oil sands development both at the lease and regional levels. The project will be conducted in three phases. Each phase is sequential such that its results and conclusions represent the foundation for the subsequent work. In this way, project investment and outcomes can be realized incrementally. Four scenarios will be incorporated into the overall project. These include scenarios constituting a basecase analysis, climate change, mine development plans, and regional development plans. The basecase scenario is a series of outcomes derived with no consideration for future climate change. The importance of the basecase is that it represents the null condition and thus provides a context for comparing the relative impact of different climate change scenarios (the focus of subsequent project activities). The basecase scenario was the main focus of the work conducted in Phase I, and is comprised of a dendrochronology study of the relationship between climate and tree growth in the sub-boreal region that encompasses oil sands mining, an aspatial analysis of habitat suitability for 10 wildlife species in relation to reclamation activities on the Kearl Lake mine, and a risk analysis of the potential for development of water stress in young reclamation plantations at the Kearl Lake mine. The report begins with an introductory chapter that defines core concepts and project objectives. Dendrochronology The dendrochronology work examined the relationship between climate and tree growth (specifically ring width) for four species (white spruce – Picea glauca, black spruce – Picea mariana, jack pine – Pinus banksiana, and trembling aspen – Populus tremuloides) in the sub-boreal forests of western Canada (Alberta and Saskatchewan). A review of on-line and literature sources was used to identify tree core collections from the region. A total of 29 chronologies were identified that matched a set of suitability criteria: 18 chronologies for white spruce, 8 for jack pine, 2 for black spruce and 1 for trembling aspen. In addition, 9 aspen chronologies were analyzed from cores collected within the region. Each core series was used to date tree rings by year of growth and to create master chronologies of ring width over the previous 75 years (1935 to 2009). Residual chronologies were generated by standardizing and detrending master chronologies to remove non-climate-related influences on growth. These residual chronologies were then correlated to one or more of 25 climate-related variables derived from climate records obtained from nearby weather stations. Results indicate that radial growth of white spruce was limited by current year water stress; significant relationships were found between radial growth and growing season precipitation and summer temperatures. Similar results were found for jack pine, but no conclusive results were found for trembling aspen or black spruce. Subsequent work will be required to (a) add additional data sources, particularly for aspen, and (b) to determine whether additional climate relationships may better explain ring chronologies. The full report is provided in Section 2. Habitat suitability analysis Habitat suitability indices (HSIs) were calculated from equations for 10 boreal forest wildlife species (moose, black bear, snowshoe hare, lynx, red-backed vole, fisher, Cape May warbler, ruffed grouse, pileated woodpecker, and northern goshawk) in natural forests and within reclamation plans developed as part of the Kearl Lake mine. Input values for each index were derived from output generated from the ecosystem simulation model, FORECAST. The development of each index was calculated from the initiation of reclamation through to mine closure as per practices described in the Kearl Lake Environmental Impact Assessment (EIA). It should be noted that for some species, the HSI includes parameters with a spatial component, the latter of which requires calculation of one or more landscape metrics. For present purposes, HSIs were calculated for the 10 species without including spatial metrics. In practical terms, these HSIs then represent the most optimistic scenarios for habitat development since the inclusions of spatial metrics only serves to reduce habitat suitability (though in some cases, the HSI may remain unchanged). Specific objectives were as follows: • Review of habitat suitability models that may be applicable to Alberta boreal forests. • Identify variables used in the habitat suitability models that can be simulated with the FORECAST model. • Simulate the reclamation prescriptions described in the Kearl Lake EIA documents with FORECAST and generate output suitable for populating each habitat suitability model. • Generate habitat suitability indices (HSIs) for 10 wildlife species (identified from the review) on the Kearl lake mine site and compare and contrast the temporal development of habitat from reclamation initiation to mine closure. Conclusions were: 1. There is a 37-year window following mine operation when upland habitat suitability is very poor on the mine footprint (an area that encompasses almost 30,000 ha). 2. Habitat suitability recovers relatively quickly thereafter; 50 years after mine operation, 4 out of 10 species have a 100 % suitability index, and this increases to 9 out of 10 species 55 years after mine operation. 3. The overall quality and pattern of recovery in habitat suitability depends on how much upland is reclaimed relative to the original (pre-mining) landscape. 4. Deviations in the post-mining distribution of ecosite phases relative to the pre-mining landscape could have significant implications for the habitat suitability of particular species, either positively (more habitat is created) or negatively. 5. The broad variation among species in their HSI values suggests that reclamation practices could be targeted towards the habitat requirements of one particular wildlife species by preferentially reclaiming more favourable ecosite phases. Conversely, a broad range of ecosite phases is necessary to promote a higher degree of biodiversity on the reclaimed landscape. 6. When habitat recovery rates on reclaimed sites are considered in conjunction with the overall mine footprint, it suggests that the negative impact of the operation is not trivial with respect to habitat loss. The full report is contained in Section 3. A risk analysis of the potential development of water stress in young reclamation plantations The development of ecologically viable reclamation strategies and methodologies in the oil sands region can be a difficult undertaking considering the logistical challenges of constructing soil covers capable of providing both the hydrological and nutritional characteristics required for the establishment of self-sustaining, productive forest ecosystems. To examine the potential for the development of water stress in proposed reclamation plantations within the Kearl Lake mining area, a risk analysis was conducted for different species and ecosite combinations using the stand-level forest hydrology model ForWaDy. The risk analysis was designed to evaluate the probability of high levels of water stress developing in young plantations of white spruce, trembling aspen, and jack pine established on different ecosites as a function of soil texture and slope position. Each species and soil type combination was simulated for a 25-year period using historical climate data from the Fort McMurray weather station. Annual summaries of simulated water stress (expressed as a Transpiration Deficit Index; TDI) during the growing season were used to derive probabilities of exceeding a range of water stress thresholds. Spruce was the species most likely to experience high TDI levels (greater than 0.3). In addition, it was the only species to reach TDI levels greater than 0.6 during the 25-year simulation period. Jack pine, in contrast, was the least likely to experience high TDI levels and did not exceed levels of 0.5 during any year; the remaining species were intermediate between the spruce and pine. The probability of exceeding TDI thresholds was consistently greater in an a-b ecosite grouping (representing dry, nutrient poor sites) relative to a d-e grouping (moist, nutrient-rich sites). Differences between the two ecosite groupings were relatively small, however. The difference would have been greater if not for the 50 cm peat layer that is applied to each site as a rooting substrate, and which alone constitutes 70% to 80% of the water holding capacity of the total soil profile. The probabilities reported here are based on the simulated response of the tree–soil combinations to the past 25 years of climate data (1982 - 2006). These years reflect the current climate but are not likely to be representative of future climate conditions predicted for the region from Global Circulation Models. An exploration of the impact of climate change on water stress and its implications for overall growth and the associated development of structural habitat elements will be conducted in Phase II of the project. The full report is contained in Section 4. The report concludes with a brief description of the next steps in the project.

Profiling stable isotopes of water signatures to define mass transport mechanisms from water capped fluid fine tailings in the oil sands industry


Author(s): Dompierre, K., & Barbour L.

Year: 2014

Abstract:
Thirty End Pit Lakes (EPLs) are planned for remediation of open pit oil sands mines in the Athabasca Oil Sands region, however their feasibility as a reclamation feature has yet to be fully evaluated. End Pit Lakes are constructed within mined-out pits and many will contain fluid fine tailings (FFT). The main objectives of these lakes are to: (1) provide an effective means of isolating these soft, consolidating tailings within the closure landscape; (2) passively treat mine site water, including expressed FFT pore water; and (3) support the development of a sustainable biological system. Mass transport processes from the FFT to the overlying lake will have considerable influence on EPL performance. Physical mass transport from the FFT to the lake will occur due to diffusion, but will also be affected by advective transport due to tailings self-weight consolidation. Defining physical mass transport mechanisms and rates through the FFT provides insight on geochemical conditions at the FFT – lake water interface, and offers a better understanding of mass balance in the EPL. Syncrude Canada Ltd. has initiated the first full-scale EPL (Base Mine Lake), and established a monitoring program to characterize the physical, geochemical, and biological processes occurring in this new system. The stable isotopes of water (δ2H and δ18O) signature of oil sands process affected water has been shown to be highly distinct from that of freshwater associated with snow melt or rainfall (Baer, 2014). As a result, the isotope composition of the lake water and FFT pore-water can potentially be used as a conservative tracer for mass transport. Samples were collected every 0.1 m across the FFT – lake water interface (2 m above, to 2 m below), at three locations in Base Mine Lake. Water from each sample was analyzed with a Picarro L-2120-i Cavity Ring Down Spectrometer based on the vapour equilibration technique used by Wassenaar et al. (2008) to determine δ2H and δ18O concentrations. These results were compared to δ2H and δ18O concentrations of the lake at multiple locations, as well as inflow and outflow water. Numerical modelling was used to interpret the measured isotope profiles across the FFT – lake water interface and elucidate mass transport mechanisms from the FFT to the lake water.

Spatial and temporal variations in fire frequency in the boreal forest of northern Alberta


Author(s): Larsen, C. P. S.

Year: 1995

Abstract:
Forest fires occur frequently in the boreal forest of North America and greatly affect vegetation dynamics, biogeochemical cycles and resident human populations. Estimates of the frequency of boreal forest fires would be useful for understanding boreal ecosystems and managing that affects of fires on human populations. The objectives of this work were to investigate relations between fire frequency and climate change, vegtitation type and waterbreaks in Wood Buffalo National Park (WBNP), located in northern Alberta. To address these objectives, four hypotheses were tested: (1) tree ring-width records from the boreal forest can provide a proxy climate record: (2) annual area burned in the boreal forest varies in response to climate changes: (3) boreal forest fire frequency varies with differences in forest type and the proximity to waterbreaks; and (4) fossil pollen and macroscopic charcoal records from massive lake sediments can provide meaningful estimates of local fire frequency. The first hypothesis was tested by constructing tree ring chronologies from 3 white spruce and two jack pine sites in WBNP. All five chronologies were significantly positively correlated with June precipitation in the growth year or the previous year, and were significantly negatively correlated with historical records of fire weather and annual area burned. The second hypothesis was tested by analyzing historical records of annual area burned and climate, and tree ring records of fire history and climate. Annual area burned was significantly negatively correlated with seasonal means of fire weather indices. The time since last fire was estimated using tree ring records from 166 sites located throughout WBNP. These records exhibited decadal and centennial scale variations in fire frequency. Comparisons with tree ring other proxy climate records suggest that these variations are related to climatic changes. The third hypothesis was tested using survival analysis of the time since last fire records, disagregated by dominant vegetation and the mean distance to waterbreaks. Sites dominated by jack pine (Pinus banksiana) and aspen (Populus tremuloides) exhibited significantly higher fire frequencies than did sites dominated by black spruce (Picea mariana) or white spruce (Picea glauca). Fire frequency increased with increased mean distance to waterbreaks. The fourth hypothesis was tested by analyzing fossil pollen and charcoal records from two lakes at $\sim$5 year resolution for 600 years. I compared their fire history records with local tree ring records of fire, and their mean fire intervals with regional fire frequency estimates for sites with similar vegetation and mean distances to waterbreaks. One lake exhibited a meaningful fire frequency estimate and the other lake did not. The poor fire frequency estimate was related to high sediment mixing and the lack of homogenous vegetation around the lake. The results indicate that: (1) area burned and fire frequency in the boreal forest of northern Alberta varies temporally at the annual, decadal and centennial scales; (2) fire frequency varies spatially in relation to vegetation type and mean waterbreak distance; and (3) lakes with massive sediments can provide meaningful estimates of local fire frequency.