Browsing by Author "Strack, Maria"

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    Biogeochemical Exchange of Carbon After Peatland Restoration: Carbon Dioxide Fluxes and Dissolved Organic Carbon Export and Chemistry
    (2013-01-25) Zuback', Yoseph; Strack, Maria
    This study looks at an abandoned peatland ten years after a restoration which was undertaken to return the peatland to its natural ecological function of carbon storage. This thesis examines the export of organic carbon in water (dissolved organic carbon), its chemical properties, and carbon dioxide (CO2) flux in different vegetation communities and environmental conditions, ultimately seeking to understand how restoration has affected the carbon exchange in the restored peatland, vs. an abandoned peatland, and a nearby natural peatland. DOC export was higher at the abandoned site over the course of the year, DOC chemical properties suggested slowing decomposition at the restored site, and restoration has roughly halved atmospheric carbon export, now ten years after restoration.
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    Carbon Dynamics in Extracted Minerotrophic Peatlands: An Analysis of the Effect of Plant Biodiversity
    (2014-05-20) Hassanpour Fard, Golnoush; Strack, Maria
    Recent experiments have shown that biodiversity loss can impair natural ecosystem functioning. Extraction of horticultural peat is known to alter the diversity of vegetation and convert peatlands from net sinks to persistent sources of carbon to the atmosphere. Peatland restoration has been shown to re‐establish the natural carbon sink function, however, current restoration techniques could be refined with more knowledge of the role of plant biodiversity. In a controlled field study, I tested the effect of plant biodiversity on carbon sequestration in an extracted peatland in Quebec, Canada. Closed‐chamber method was used to measure the flux of carbon between the peatland and the atmosphere in fourteen treatments planted with different numbers of species. Species richness was not found to have a significant impact on carbon sequestration and no overyielding was detected in polycultures. Species identity was important with Carex aquatilis having a significantly positive impact on carbon sequestration.
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    Dissolved Organic Carbon Dynamics in Constructed and Natural Fens in Athabasca Oil Sands Development Region near Fort McMurray, Alberta
    (2014-09-30) Khadka, Bhupesh; Strack, Maria
    Peatlands, mainly fens, are largely disturbed in order to recover bitumen below the surface in the Athabasca oil sands development region, Alberta. Mine closure plans require ecosystem reclamation: hence fen construction method is being investigated. In this study, dissolved organic carbon (DOC) dynamics in a constructed fen were compared with three other diverse natural fens in the region. The constructed fen had lower soil DOC concentration than all natural fens. Based on E2/E3, E4/E6 and SUVA254 of the DOC, the constructed fen had DOC with significantly greater humic content, aromatic nature and larger molecular size than the natural fens. A laboratory DOC production study revealed that these patterns are likely due to the limited DOC contribution from newly planted vegetation at the constructed fen resulting in DOC largely derived from humified peat. These preliminary results suggest that DOC dynamics in the constructed system could be useful for evaluating reclamation success through time.
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    Effect of Drainage on Carbon Biogeochemistry and Microbiological Communities in Western Canadian Boreal Peatlands
    (2013-05-01) Graham, Jaime; Dunfield, Peter; Strack, Maria
    This study compared the bacterial and archaeal communities between a natural peatland and a peatland affected by water table drawdown along a microtopographic position and depth gradient. Peat physicochemical properties, carbon flux and potential CO2 and CH4 production as well as CH4 oxidation were measured to determine which factors affect microbial composition and diversity. Bacterial and archaeal communities were described by targeting the 16S rRNA gene using pyrosequencing. Physicochemical parameters measured included pH, peat temperature, humification, acetate, formate, sulfate, nitrite and nitrate. The most predominant methanotroph genus was Methylocella and the most predominant methanogen group was Methanomicrobiales Rice Cluster II. Diversity indices show humification and position relative to the water table as significant drivers affecting microbial diversity and richness. The control and drained sites differed significantly regarding the physicochemical influences on microbial relative abundance, however, pH affected methanotroph and methanogen relative abundance at both peatland sites.
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    Local Hydrologic Conditions Associated with Seismic Line Disturbance in the Boreal Forest of Northern Alberta
    (2024-04-24) Weiland, Lelia Mae; Ketcheson, Scott; McDermid, Greg; Strack, Maria; Ryan, Cathy
    Seismic lines are a prominent disturbance in the boreal forest, characterized by clearcut lines between 1.5-10 meters wide, fragmenting the landscape. After clearing, these seismic lines frequently exhibit low seedling recruitment and growth rates, due in part to the altered hydrological conditions on the line, resulting in a persistent disturbance that requires further understanding to facilitate recovery. As such, this research quantified soil and hydrologic properties on seismic lines at two sites south of Fort McMurray Alberta during 2021 and 2022. Water table levels were measured weekly, and were paired with measurements of bulk density, saturated hydraulic conductivity, porosity and specific yield. A snow study, completed in March of 2022, analyzed snow depth, density and snow water equivalent across seismic lines. Bulk density increased on seismic lines by 16% and 124% in lowland and upland ecosites respectively, due to compression in lowlands, and moss removal in uplands. Saturated hydraulic conductivity decreased on seismic lines by one order of magnitude for upland and lowland ecosites. Porosity decreased significantly at the rooting zone in upland ecosites. Specific yield decreased significantly at the surface of upland and lowland ecosites. Water table variability was increased on seismic lines, however depth to water table was more related to topographic position. Snow water equivalent was up to 90 mm higher than the natural area on wide East-West oriented lines. The results may provide information to researchers and industry partners on the alteration of important ecosite factors on seismic lines that may limit line recovery trajectories.
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    Mapping shrub biomass in a boreal continental fen
    (2019-01-24) He, Annie; McDermid, Gregory J.; Post, John R.; Strack, Maria
    Biomass estimation is a heavily explored topic in the literature, as biomass information can provide valuable insight into understanding an ecosystem’s health. However, few studies exist on quantifying aboveground biomass (AGB) in peatlands. This thesis summarizes how allometric equations and unmanned aerial vehicles (UAV) can be used to map AGB across a 2-hectare peatland site. Prior to using UAVs to measure AGB, accurate field measurements are required to calibrate and validate the UAV-AGB model. We developed allometric equations for three dominant shrub genera found in boreal peatlands and found that equations based on shrub genus were not significantly different from a pooled equation of all shrub genera. The UAV study revealed that UAV-derived volume was the best predictor of AGB (R2=0.885) and was subsequently used as the dependent variable for our AGB model. This thesis reports the findings revealed through the process of estimating AGB using allometric equations and UAVs.
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    Methanotrophic Bacteria and Biogeochemical Cycling in an Oil Sands End Pit Lake
    (2016) Haupt, Evan; Dunfield, Peter; Voordouw, Gerrit; Gieg, Lisa; Strack, Maria; Else, Brent
    This study examined for the first time the microbial community and biogeochemical cycling of methane and oxygen in Base Mine Lake, the reclamation site of a former tailings pond in the Athabasca oil sands region of Northern Alberta. Base Mine Lake represents the first large-scale demonstration of the “water-capped end pit lake” approach to tailings pond reclamation, with the ultimate goal of transitioning the lake into a natural, self-sustaining ecosystem. The oxygenated upper portion of the lake is home to aerobic hydrocarbon degrading bacteria, including a diverse population of methane oxidizing bacteria, whose activity, dispersion, and community composition is greatly influenced by seasonal variation. The majority of methanotrophs in the lake belong to the class Gammaproteobacteria, although Alphaproteobacteria methanotrophs make up a relatively large percentage of methanotrophs during summer stratification. Methanotroph abundance and potential for methane oxidation are relatively high during periods of turnover or partial mixing in the lake, and decrease during stratification.
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    Mineral nitrogen and phosphorus pools affected by water table lowering and warming in a boreal forested peatland
    (2017-09-14) Munir, Tariq; Khadka, Bhupesh; Xu, Bin; Strack, Maria; Munir, Tariq
    Changes in atmospheric temperature and lowering in water-table (WT) are expected to affect peatland nutrient dynamics. To understand the response of peatland nitrogen (N) and phosphorus (P) dynamics to warming and drainage in a continental wooded-bog of hummock – hollow microtopography, we compared three sites: 1) control, 2) recently drained (2-3 years; experimental), and 3) older drained (12-13 years; drained), during 2013. The WT was lowered at experimental and drained sites to 74 cm and 120 cm, respectively, while a warming of ~1 °C was created at one-half of the microforms using open-top chambers. Responses of peat total-inorganic- nitrogen [TIN = nitrate nitrogen (NO3--N) + ammonium nitrogen (NH4+-N)] and phosphate-P [PO43--P] pools and, vegetation C:N ratio, δ13C, and δ15N to the experimental treatments were investigated across sites/microforms and over time. Peat TIN available and extractable pools increased with deepening of WT and over time, and were greater at hummocks relative to hollows. In contrast, the PO4 pools increased with short-term drainage but reverted to very close to their original (control) nutrient values in the longer-term. The WT and warming driven change in the peat TIN pool was strongly reflected in the vascular vegetation C:N ratio and, shrub δ13C and δ15N, while moss nutrient dynamics did not vary between sites. Therefore, we suggest that atmospheric warming combined with WT deepening can increase the availability of mineral N and P, which then can be reflected in vascular vegetation and hence modify the productivity and ecosystem functioning of the northern mid-latitude continental forested bogs in the long-term.
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    Partitioning Forest-Floor Respiration into Source Based Emissions in a Boreal Forested Bog: Responses to Experimental Drought
    (MDPI, 2017-03-10) Munir, Tariq; Khadka, Bhupesh; Xu, Bin; Strack, Maria
    Northern peatlands store globally significant amounts of soil carbon that could be released to the atmosphere under drier conditions induced by climate change. We measured forest floor respiration (RFF) at hummocks and hollows in a treed boreal bog in Alberta, Canada and partitioned the flux into aboveground forest floor autotrophic, belowground forest floor autotrophic, belowground tree respiration, and heterotrophic respiration using a series of clipping and trenching experiments. These fluxes were compared to those measured at sites within the same bog where water‐table (WT) was drawn down for 2 and 12 years. Experimental WT drawdown significantly increased RFF with greater increases at hummocks than hollows. Greater RFF was largely driven by increased autotrophic respiration driven by increased growth of trees and shrubs in response to drier conditions; heterotrophic respiration accounted for a declining proportion of RFF with time since drainage. Heterotrophic respiration was increased at hollows, suggesting that soil carbon may be lost from these sites in response to climate change induced drying. Overall, although WT drawdown increased RFF, the substantial contribution of autotrophic respiration to RFF suggests that peat carbon stocks are unlikely to be rapidly destabilized by drying conditions
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    Peatland Biogeochemistry and Plant Productivity Responses to Field-based Hydrological and Temperature Simulations of Climate Change
    (2015-01-09) Munir, Tariq; Strack, Maria
    Northern peatlands have accumulated approximately one third of all soil carbon (C) and therefore play an important role in the global C cycle. Besides the C sink function, peatlands are one of the largest biological sources of atmospheric methane (CH4) and represent approximately 10% of global soil nitrogen (N) stocks. These ecosystems are present at latitudes that are predicted to be highly sensitive to climate change that will likely result in deeper water table positions. The reduction in soil moisture may increase peat decomposition rates and consequently affect nutrient dynamics. While attempts have been made to assess the impact of climate change on peatland C gas exchange and nutrient dynamics, controlled field experimentation remains limited. Therefore, the objectives of this thesis were to estimate the responses of peatland carbon dioxide (CO2) and CH4 flux, nutrient dynamics, and plant productivity to a recent- and a ten-year old drainage, and a warming treatment induced by open-top chambers, across the peatland’s hummock-hollow microtopography. The study was carried out at a dry continental treed bog in boreal Alberta during 2011-2013. Water level drawdown in the longer-term resulted in shifts in biomass coverage and plant community composition between the microforms. The moss biomass was replaced by vascular plant biomass (mostly woody shrubs) at hummocks, and by lichen biomass at hollows. The shift in dominant vegetation was reflected in CO2 fluxes; the longer-term drained hummocks were the largest sink of CO2 while hollows at the same site were the largest sources. While the short- and longer-term drained sites were net sources of CO2, the warming treatment converted the longer-term drained site to a sink of CO2-C. Water table drawdown greatly reduced CH4 flux at both hummocks and hollows, and the reduction increased with time. The warming treatment increased emissions of CH4 at hollows and increased consumption of CH4 at hummocks. The extractable and available nutrient pools in the peat soil increased with deepening of water level, and over time. The water level driven dynamics of peat nutrient pools were reflected in the vegetation C:N ratio. The warming treatment increased nutrient pools more at hummocks than at hollows and the impact increased with time. Based on these results, I suggest that, models of peatland development need to include C and nutrient cycling links to moisture and temperature parameters to better predict plant productivity and C exchange under changing climatic conditions.
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    Picea mariana (Mill.) B.S.P Plantation on Cutover Peatland in Alberta (Canada): Evaluating the Effect of Fertilization and Resulting Carbon Stocks.
    (2015-04-29) Garcia Bravo, Tania; Strack, Maria; McDermid, Greg
    Horticultural peat extraction in Canada is mainly performed by vacuum-harvesting, leading to a residual peat soil limited in nutrients and seed bank, which does not allow adequate plant recovery once extraction ceases. Restoration techniques have been designed for the rehabilitation of open bog areas in eastern Canada, but in western Canada many undisturbed peatlands have high cover of forest and the reintroduction of trees should be part of restoration goals. This study is focused on Picea mariana (Mill.) B.S.P (black spruce) plantation. Previous studies have shown that fertilization is needed, but the adequate dose of fertilizer to create the preferred habitat structures remains unclear. Fertilizer dose could also affect the colonization of non-target species such as Betula papyrifera (March.) and consequently microclimate conditions and competition could affect the growth of P. mariana. Results showed that a low dose of fertilizer (8.9 g/ bag) allowed P. mariana to establish while controlling the B. papyrifera colonization. Higher rates of fertilization resulted in dense B. papyrifera communities having a direct effect on photosynthetically active radiation and relative humidity at ground level. Black spruce plantation on cutover peat will also affect the site’s carbon (C) balance. The C balance was estimated using the C stock in biomass of the forest plantation and soil respiration measurement (CO2 and CH4). Although B. papyrifera fixed C though biomass, they also may influence the site hydrology by higher evapotranspiration. After seven years post-restoration, the study site was a source of C due to dry conditions and lack of understory, resulting in peat oxidation. These results can be used to assist in the choice of suitable treatments when the restoration goal is the recovery of ecological functions in cutover peatlands.
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    Quantifying the Impact of Seismic Lines on Methane Release in a Treed Bog Ecosystem using Unmanned Aerial Vehicles (UAVs)
    (2017-12-22) Lovitt, Julie; McDermid, Gregory; Strack, Maria; Bergerson, Joule
    Peatlands are extremely complex and sensitive ecosystems, capable of releasing vast amounts of methane in response to disturbance events. To date, little advancement has been made by researchers to quantify the impact of small-scale anthropogenic disturbances on these ecosystems, specifically seismic lines. These “low-impact” linear features present a challenge to researchers as they exist at dimensions too small for the majority of remote-sensing platforms to successfully identify and measure, even though they account for a considerable portion of land disturbance in Canada’s western Boreal, and are anticipated to have extensive, compounding environmental effects. This thesis summarizes how unmanned aerial vehicle photogrammetry can be used to address this knowledge gap by showcasing the ability to generate accurate peatland terrain models, and subsequently estimate seismic-line impacts on both physical parameters (microtopography and depth-to-water) and peatland methane emission, ultimately revealing one of the hidden impacts of seismic lines on Canada’s Boreal peatlands.
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    Spatial variability of soil hydrophysical properties in Canadian Sphagnum dominated peatlands
    (2013-01-18) Branham, Jordanna; Strack, Maria
    Patterned peatlands develop through eco-hydrological feedback loops, resulting in a microtopography of hummocks and hollows. Physical and hydrologic properties were compared between climate zones, peatland types, microform types and depth in relation to elevation and the water table, to determine if the ecologic definition of microforms holds true for their hydrologic properties. Study sites were located near St. Charles-de-Bellechasse, Quebec, and Wandering River, Alberta, and consisted of a bog and fen in each location. Cores were extracted from the field and soil physical properties (bulk density, decomposition, and porosity) and hydrologic properties (saturated and unsaturated hydraulic conductivity, water retention and anisotropy), were measured. Climate may play a potential role in the anisotropy of saturated hydraulic conductivity, while peatland type influences the degree of difference between hummocks and hollows. Saturated hydraulic conductivity is dependent on depth, and supports current model assumptions of higher flow in hollows than in hummocks. Finally, unsaturated hydraulic conductivity is dependent on the physical properties of pore size distribution, inactive to active pore ratio and decomposition status. Implications of the results suggest that model assumptions for saturated K should be based on the presence of macropores or mesopores within the peat matrix, and not bulk density alone. Models that currently use only one hydraulic conductivity value for a peatland apply to only the saturated zone, as microforms significantly impact the unsaturated conditions.
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    Towards the early detection of CO2 leaks from carbon storage sites: modelling and measurement of reaction, diffusion and mass flow of CO2 and O2 in near-surface soils
    (2018-01-18) Alam, Md Monzurul; Norman, Ann-Lise; Layzell, David; Strack, Maria; Yau, Andrew
    Carbon capture and storage (CCS) of CO2 in geological reservoirs is being used to mitigate climate change and so a method and technology is needed for early leak detection. This thesis focuses on understanding the reaction, diffusion, and mass flows of O2 and CO2 in near surface soils with or without a CO2 leak. Two numerical models were developed to describe O2 and CO2 reactions, diffusion, mass flow and concentration gradients in the top 1 m of Alberta soils. The first model showed that under typical soil pH values, virtually all CO2 and O2 diffusion would occur in the gaseous phase, with less than 0.10% occurring in the aqueous phase, even for high soil water content. The second model calculated the contribution of diffusion and mass flow for CO2 and O2 in the gas phase of soils having a range of respiratory quotient (RQ=CO2 flux/O2 flux) values, with or without a CO2 leak. With RQ values ranging from 0.7 to 1.2, mass flow was predicted to account for -0.19% to 1.09% of CO2 flux to the soil surface, respectively. When simulated rates of CO2 leakage were set at 1 and 5 times the net biological flux from soils, the contribution of mass flow to total CO2 flux increased to about 3% and 13%, respectively. The model was also used to identify the Gas Concentration Ratio (GCR = [CO2] differential between bulk air and soil surface / [O2] differential between bulk air and soil surface) as a metric that could be used to identify soils impacted by a CO2 leak. Three gas analysis systems were built for use with a soil column to test the accuracy of the models and the potential value of a GCR measurement. The observed concentration gradients were found to be a good fit to the model predictions and the observed GCR measurements were able to differentiate between soils impacted by CO2 leaks as low as 2 to 3 times the normal biological flux rate of soils (ca. 2 μmolCO2/m2/s). This work supports the further development and use of a portable instrument to carry out GCR measurements at CCS sites.
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    UAV Remote Sensing Can Reveal the Effects of Low-Impact Seismic Lines on Surface Morphology, Hydrology, and Methane (CH4) Release in a Boreal Treed Bog
    (Journal of Geophysical Research: Biogeosciences, 2018-02-23) Lovitt, Julie; Rahman, Mustafizur M.; Saraswati, Saraswati; McDermid, Gregory J.; Strack, Maria; Xu, Bin
    Peatlands are globally significant stores of soil carbon, where local methane (CH4) emissions are strongly linked to water table position and microtopography. Historically, these factors have been difficult to measure in the field, constraining our capacity to observe local patterns of variability. In this paper, we show how remote sensing surveys conducted from unmanned aerial vehicle (UAV) platforms can be used to map microtopography and depth to water over large areas with good accuracy, paving the way for spatially explicit estimates of CH4 emissions. This approach enabled us to observe—for the first time—the effects of low-impact seismic lines (LIS; petroleum exploration corridors) on surface morphology and CH4 emissions in a treed-bog ecosystem in northern Alberta, Canada. Through compaction, LIS lines were found to flatten the observed range in microtopographic elevation by 46 cm and decrease mean depth to water by 15.4 cm, compared to surrounding undisturbed conditions. These alterations are projected to increase CH4 emissions by 20–120% relative to undisturbed areas in our study area, which translates to a total rise of 0.011–0.027 kg CH4 day 1 per linear kilometer of LIS (~2 m wide). The ~16 km of LIS present at our 61 ha study site were predicted to boost CH4 emissions by 20–70 kg between May and September 2016.