Peat-mineral Mix Research Articles

Trembling aspen root suckering and stump sprouting response to above ground disturbance on a reclaimed boreal oil sands site in Alberta, Canada

Trembling aspen (Populus tremuloides Michx.) is an important early successional species in the boreal region that commonly regenerates via root suckering and, to a lesser extent, stump sprouting after aboveground disturbance such as harvesting or wildfire. However, the response of aspen to disturbance on reclaimed oil sands sites is not known. To determine the suckering and sprouting response of 6-year-old seedling origin aspen growing on a reclamation site, we destructively sampled 87 individual trees in May 2017. Trees were selected across two soil types, forest floor-mineral mix and peat-mineral mix, and three height classes, 100–199 cm, 200–299 cm, and > 300 cm. In August 2017, we returned to each cut tree to assess the type (sucker vs. stump sprout) and abundance of regeneration. Aspen readily responded to disturbance; however, responses were highly variable between trees, ranging from zero to 47 suckers and zero to 42 sprouts. Trees growing on peat-mineral mix were 7.8 times more likely to produce at least one sucker and generally had a higher abundance of suckers. Tree height was also positively correlated with suckering probability and abundance, while competition from surrounding vegetation decreased the probability and abundance of suckering, especially when cover of competing species was greater than 52.5%. The probability of stump sprouting was not affected by soil type or tree size, but did decrease with increases in tree competition. Overall, trembling aspen respond vigorously to disturbances on mine reclamation sites which is a promising sign of resilience for these novel and young ecosystems.

Growth Response of Aspen and Alder to Fresh and Stockpiled Reclamation Soils

Soil stockpiling is a common reclamation practice used in oil sands mining in the boreal forest region of Canada to conserve soil resources; but stockpiling may have detrimental effects on soil quality and plant growth. We examined growth response of trembling aspen (Populus tremuloides Michx.), a fast-growing early successional tree, and green alder (Alnus viridis (Chaix) DC. ssp crispa (Ait.) Turrill), a nitrogen-fixing shrub, to stockpiling and fertilization treatments on two reclamation soils (forest floor mineral mix (FFMM) and peat mineral mix (PMM)). Aspen and alder seeds were planted and their growth monitored for four months in the greenhouse. We found that unfertilized stockpiled FFMM supported significantly higher aspen and alder aboveground biomass than the other fresh and stockpiled soils. Phosphorus and potassium supply rates were highest in stockpiled FFMM and were positively correlated with aboveground plant biomass. There was no significant difference in aspen and alder aboveground biomasses between unfertilized fresh FFMM and PMM soils. Aspen grown in combination with nitrogen-fixing alder did not experience competition or facilitation except on fresh PMM, where aspen height declined. Fertilization increased both aspen and alder growth and eliminated differences in growth between soil types and stockpiling treatments. Our study showed that individual soil properties are more important for revegetation purposes than type of soil or stockpiling treatment.

Comparing Spatial Heterogeneity of Bioavailable Nutrients and Soil Respiration in Boreal Sites Recovering From Natural and Anthropogenic Disturbance

The mining of oil sands in Alberta, Canada is a large-scale disturbance that requires land reclamation to equivalent land capability. Cover soils used for upland forest reclamation are forest floor mineral-mix (FFM) sourced from upland forest ecosystems and peat mineral-mix (PM) sourced from lowland ecosystems. Spatial heterogeneity and quantity of soil resources, especially nutrient bioavailability, is important because it affects the establishment of native vegetation in forest ecosystems and soil respiration is an indicator for overall soil biologic activity. We studied spatial heterogeneity of soil nutrients as well as seasonal and spatial patterns of soil respiration in two sites reclaimed either with FFM or PM and two reference sites recovering either from harvest or fire. Contrary to our initial hypothesis, we identified spatial heterogeneity in some bioavailable nutrients in FFM and PM cover soil, indicating that standard placement processes can recreate spatial heterogeneity. However, some nutrients such as P, K and S showed no heterogeneity in PM at all. P and K availability was significantly lower and S was significantly higher in PM than in FFM and reference sites. Seasonal pattern of respiration showed variability on natural reference sites and on FFM, indicating that disturbance had not removed belowground function completely. PM reclaimed sites showed no strong seasonal respiration patterns indicating homogeneous belowground function. Surprisingly PM treatments were not characterized by highest rates of soil respiration while having highest amounts of total organic carbon. We conclude that FFM reclaimed sites may be more successfully reclaimed than PM sites because they are more similar to reference sites in terms of nutrient status and seasonal respiration patterns.

Evaluating foliar nutrient concentration as an indicator of soil nutrients in reclaimed and natural forests in Alberta, Canada

ABSTRACT Foliar nutrient concentrations are commonly recommended as indicator for soil nutrient status in managed and wildland ecosystems. Using data from an oil sands mine reclamation site in Alberta, Canada, we evaluated whether trembling aspen (Populus tremuloides Michx.) foliar concentrations of macronutrients accurately represent soil solution and soil nutrient pools in both reclaimed and wildfire-impacted natural reference boreal forest ecosystems. Reclamation soils were upland-based forest soil (forest floor-mineral mix; FFMM) and lowland-based peat soil (peat-mineral mix; PMM) with and without fertilisation. Individual macronutrient concentrations differed among treatments in the soil nutrient pool, but differences decreased in the soil solution pool and disappeared in the foliar pool. Few significant correlations between foliar and belowground pools were observed, but foliar phosphorus was correlated to soil phosphorus in natural reference sites. Multivariate analyses showed reclaimed sites were different from reference sites across all nutrient pools. Again, few significant multivariate correlations between foliar and belowground nutrient pools were observed, except for the unfertilised forest floor-mineral mix site, where foliar nutrients were positively correlated with soil solution. Based on our findings, we suggest that trembling aspen foliar nutrient concentrations are not a consistently reliable indicator of soil and soil solution nutrients in reclaimed or natural ecosystems.

Biochar affects aspen seedling growth and reclaimed soil properties in the Athabasca oil sands region

Restoring ecosystem function after oil sands surface mining involves reestablishing the biotic and abiotic ecosystem components that affect biogeochemical cycles and fluxes. In boreal forest ecosystems, pyrogenic carbon is a native soil component that affects a variety of biogeochemical parameters and biochar is its human-made analog. To evaluate the benefits of biochar amendment to reclamation cover soils, we compared characteristics and function of peat–mineral mix (PM) and forest floor–mineral mix (FFM) with and without biochar in an 18 wk greenhouse study. We assessed nutrient bioavailability (NO3, NH4, P, K, S, Mg, and Ca), foliar nutrient concentrations (N, P, K, S, Mg, Ca, Na, and Mo), soil respiration, rhizosphere polysaccharide concentration, soil organic matter stability, and Populus tremuloides Michx. seedling growth. Seedling growth increased significantly on PM cover soil with biochar. Biochar improved K nutritional status and potentially interacted with Na bioavailability in PM, affecting growth. Soil respiration significantly decreased in PM with biochar and increased in FFM. Soil organic matter stability was positively correlated with seedling growth and increased with biochar. Our findings suggest that biochar may have a significant positive effect on upland forest reclamation in the Athabasca oil sands region, especially on sites that are reclaimed with PM.

Coarse Woody Debris as a Land Reclamation Amendment at an Oil Sands Mining Operation in Boreal Alberta, Canada

Coarse woody debris (CWD) is an important component of natural forests and is now being used in reclaiming oil sands land to control erosion, enhance diversity, and function as longer term storage of organic matter. However, the impact of woody debris on reclaimed ecosystems may vary depending on the amount applied and the soil it is applied to. We studied the impact on the plant community (including tree regeneration and understory plants) and soil properties of four levels of CWD cover (None, Low, Moderate, High) on two reclamation soils (forest floor-mineral mix and peat-mineral mix) and natural post-fire soils. Significant differences were observed among soil types in terms of the plant community and soil properties but fewer differences were attributable to CWD. However, overall native plant species’ diversity and abundance decreased with High CWD while cover of non-native species on the reclaimed soils greatly decreased with Low CWD. Natural seedling regeneration density of trembling aspen was unaffected by CWD on both reclamation soil types. The soil nutrient supply rates and soil moisture were significantly different among soil types but there were no differences among debris treatments while soil temperature decreased with CWD. Overall, a Low (up to 30% ground cover) woody debris application appears to be optimal for maintaining native plant species diversity and abundance while controlling undesirable plant species.

Ecohydrological functioning of an upland undergoing reclamation on post‐mining landscape of the Athabasca oil sands region, Canada

AbstractEcohydrological functioning of natural Boreal forest in Canada's Boreal Plains is a product of interactions between soil hydrophysical characteristics and hydrogeochemical processes. These interactions create a moisture–nutrient gradient within the surface soils, increasing along low‐relief transitions from upland to riparian zone, and in turn influence the distribution of vegetation communities. It is not yet known if/when analogous ecohydrological functions can be achieved in constructed uplands following industrial disturbance, such as that following oil sands development. Hence, to assess this, we studied interactions between hydrogeochemical processes and vegetation colonization in a constructed upland relative to hydrophysical properties of 2 reclamation cover substrates during a typical continental climate's growing season. Our results indicated that in 3 years of postconstruction, the establishment of a moisture–nutrient gradient that supports vegetation colonization along slope positions was still limited by heterogeneity of cover substrates. Portions of the upland under peat–mineral mix were characterized by lower nutrient availability, high moisture content, and establishment of planted shrubs and trees. In contrast, forest floor materials plots were characterized by poor soil quality, but higher nutrient availability and greater colonization of invasive grasses and native shrubs. We suggest that the colonization of underdeveloped soils by invasive grasses may facilitate pedogenic processes and thus should be accepted by reclamation managers as a successional milestone in the recovery of ecohydrological functioning of constructed uplands. Poor soil structure under forest floor materials could not support edaphic conditions required by plants to efficiently utilize fertilizer, making this practise futile at the early stage of soil development.

The impact of reconstructed soils following oil sands exploitation on aspen and its associated belowground microbiome

The objective of this study was to investigate the impact of different soil covers used to reclaim decommissioned oil sands mining sites on the genetic diversity of aspen and their associated belowground microbiota. Aspen genotyping showed that trees mostly originated from sexual reproduction on sites reclaimed with soil covers made of upland forest floor-mineral mix (FFMM) and lowland peat-mineral mix (PMM). In contrast, most individuals in mature and burned stands sampled as benchmarks for natural disturbances originated from vegetative reproduction. Nonetheless, aspen populations in the FFMM and PMM sites were not genetically different from those in mature and burned stands. DNA metabarcoding of bacteria and fungi in root and soil samples revealed that the diversity of the belowground microbiota associated with aspen and the relative abundance of putative symbiotic taxa in PMM were significantly lower than for FFMM and naturally disturbed sites. Despite similar aspen genetic diversity between FFMM and PMM sites, trees were not associated with the same belowground microbiota. Because the soil microbiome and more specifically the mycorrhizal communities are variable both in space and time, long-term monitoring is particularly important to better understand the ecological trajectory of these novel ecosystems.

Micronutrient concentrations vary between peat–mineral mix and substrates in revegetated sites in the Alberta oil sands

Adequate supply of micronutrients is essential for plant growth in reclaimed sites in the Athabasca oil sands region. The objectives of this study were to determine boron, iron, manganese, copper, and zinc concentrations in peat–mineral mix (PMM), tailings sand (TS), and overburden (OB) materials and to assess whether lodgepole pine (Pinus contorta) planted on PMM over TS and white spruce (Picea glauca) planted on PMM over OB had low foliar micronutrient concentrations. Micronutrient concentrations determined using LiNO3 and Mehlich-3 extractions were different between PMM and TS in the pine sites while only LiNO3 extractable boron was different between PMM and OB in the spruce sites (p iron > manganese > zinc > copper in all soil layers with concentrations ranging from 0.04 to 39.56 μg g−1. The low foliar concentration of copper in pine and spruce was consistent with low LiNO3 extractable copper in the soil in both the pine and spruce s...

Carbon, nitrogen and phosphorus release from peat and forest floor-based cover soils used during oil sands reclamation

Reclamation practices in the oil sands region of Alberta involve the reconstruction of soil profiles using a combination of salvaged mineral substrates and organic-matter-rich surface materials, including peat–mineral mix (PM) and forest floor – mineral mix (FFM). The successful re-establishment of vegetation on reclaimed sites is for a large part dependent on the nutrients these materials can provide. Hence, the overall objective of this study was to compare carbon (C), nitrogen (N), and phosphorus (P) release rates from PM and FFM materials used to cap reconstructed sandy soils. A 325 d laboratory incubation was conducted to measure these rates. The two materials released comparable amounts of N on a per kilogram of soil basis (111–118 mg N kg−1). However, when results were normalized based on each material’s organic C content, N release was six times greater for FFM than for PM, in accordance with results of previous studies. In addition, overall C mineralization and P release rates were over one order...

Forest water use in the initial stages of reclamation in the Athabasca Oil Sands Region

AbstractFollowing large‐scale surface oil sands mining, large tracts of the boreal forest in the Athabasca Oil Sands Region of Western Canada are legally required to be reclaimed. A greater understanding of how these novel ecosystems function and develop with regard to water use is crucial to aid in the development of regulatory practices and protocols based on information from ecosystem recovery. In this paper, a 12‐year (2003–2014) eddy covariance measurement record of latent and sensible heat fluxes and gross ecosystem productivity of carbon dioxide is analysed to evaluate how a reclaimed boreal forest has developed during its initial growth period. The study site is a reclaimed oil sands saline‐sodic clay shale overburden deposit that was topped with 100 cm of glacial till and 20 cm of peat mineral mix. The site was seeded with barley (Hordeum spp.) in 2001 to reduce erosion of the soil cover whereas aspen (Populus tremuloides Michx.) and spruce (Picea glauca [Moench] Voss) boreal tree species were planted in 2004. Changes in structure and function corresponded to the transition of dominant vegetation cover from early successional species to forest. Leaf area index increased from a growing season peak of 0.9 in 2003 to 4.0 in 2014 and was associated with an increased growing season gross ecosystem productivity (4.9 to 8.9 g C m−2 day−1), an increased evapotranspiration (1.6 to 3.4 mm day−1), and a decreased partitioning of energy to sensible heat (Bowen's ratio decreased from 1.1 to 0.4). Although canopy conductance increased throughout the 12 years, the shift from early successional species to trees with more conservative water use resulted in a decrease in conductance normalized by leaf area. Water use efficiency has increased slightly since 2008 with an average of 10.0 g CO2 kg−1 H2O for the last 6 years. No prolonged dry periods were observed during the study period. The functioning of this novel ecosystem is evolving as expected on the basis of the trends observed for other natural and disturbed boreal forests.

Germination and early growth of boreal understory plants on 3 reclamation soil types under simulated drought conditions

Forest land reclamation after industrial activity requires the re-establishment of self-sustaining ecosystems consisting of native plant species. This greenhouse study determined the germination and early growth of the understory species Leymus innovatus (Beal) Pilg. (Poaceae; hairy wild rye), Chamerion angustifolium (L.) Holub (Onagraceae; fireweed), and Solidago canadensis L. (Asteraceae; goldenrod) in 3 operational reclamation soil types (forest floor-mineral mix, peat-mineral mix, and clay topsoil) under various water stress conditions. Germination of the 3 species occurred only when a standard, high moisture level was maintained; there was essentially no germination when watering was restricted. Furthermore, C. angustifolium germination was greatest in the forest floor-mineral mix. Seedling biomass production in all species and in all soil types increased with higher watering rates; however, the growth increase with watering was lessened on the peat-mineral mix and clay soils, likely because of limited nutrient supplies. Among the species studied, C. angustifolium had the greatest bio-mass growth potential in higher watering treatments but it was more sensitive to drought with higher mortality in the lower watering treatments. By contrast, L. innovatus and S. canadensis had greater relative biomass production in drier conditions and had greater root:shoot ratios than did C. angustifolium . These results can be used operationally by reclamation practitioners to aid in the development and deployment of appropriate native plant seed mixes to the correct reclamation site and soil types. Pinno BD, Li EHY, Khadka B, Schoonmaker A. 2017. Germination and early growth of boreal understory plants on 3 reclamation soil types under simulated drought conditions. Native Plants Journal 18(2):92–104.

Reclaimed soils, fertilizer, and bioavailable nutrients: Determining similarity with natural benchmarks over time

Comparing functional similarity in reconstructed ecosystems with natural benchmarks can provide ecologically meaningful information to measure reclamation success. We examined nutrient supply rate using ion-exchange resins as a measure of ecosystem function in two oil sands reclaimed soils, viz. peat mineral mix (PMM) and forest floor mineral mix (FFMM), and measured fertilization effect on nutrient supply rates in these soils for three consecutive years contrasted with young-fire-disturbed and mature forest stands. Results indicated that nutrient profiles of reclaimed soils were significantly different than natural benchmarks. Phosphorus and potassium supply rates in reclaimed soils were up to 91% lower, whereas S, Ca, and Mg were, respectively, up to 95%, 62%, and 74% higher than in benchmark soils. The expected nutrient flush postfertilization was only apparent in N and P, but the transient effect levelled off the year after fertilization in most cases. Fertilization aligned the temporal trajectory of ...

English

The goal of land reclamation after oil sands mining in the boreal forest of northern Alberta, Canada is to re-establish functioning forest ecosystems, including the development of a natural plant community. Reclamation practices include the use of operational reclamation soils derived from upland forest soils (referred to as forest floor-mineral mix (FFMM)), which has higher plant diversity, and lowland based peat-mineral mix (PMM), which has greater tree regeneration. Building from experience in forest harvesting practices and natural landscape patterns, the reclamation concept was put into practice in a new reclamation area established in 2015 with patches or islands of differing sizes and shapes of FFMM placed within a matrix of the more abundant PMM. These islands of FFMM are intended to serve as lifeboats and colonization centres for native biota. Initial studies are focusing on determining the optimal size and spacing of the FFMM patches. Plant species area curves were developed and show that patch sizes of at least 671 - 960 m 2 are recommended to allow initial establishment of native plant species, and in particular woody species, with smaller patch sizes favouring non-native weedy species. Initial spatial patterns indicate no relationship between plant species richness and distance to FFMM - PMM soil boundary with the rate and distance of spread of native plants from the FFMM patches being an important monitoring consideration in future years. This work on the Islands approach will help in the development of more efficient and effective reclamation practices which take advantage of the ecological differences in available reclamation soils.

Nutrient loaded seedlings reduce the need for field fertilization and vegetation management on boreal forest reclamation sites

Tree seedlings loaded with nutrients during nursery production have shown increased growth and survival relative to standard seedlings upon outplanting. We examined outplanting performance of nutrient loaded and standard trembling aspen (Populus tremuloides) seedlings, along with composition and cover of competing vegetation, on a boreal oil sands reclamation site with two different soil types (forest floor mineral mix and peat mineral mix) and four different broadcast fertilizer applications [250 kg/ha immediately available fertilizer (IAF), 500 kg/ha IAF, 670 kg/ha controlled release fertilizer, and an unfertilized control]. Average height growth across all treatments was 19 % greater for nutrient loaded aspen seedlings than standard seedlings after two growing seasons. With respect to soil types, aspen growth was greater on peat mineral mix and seedlings growing in this soil type showed a greater response to both nutrient loading and fertilization; however, this could partially be attributed to greater cover by competing vegetation on the forest floor mineral mix. In the first growing season, trees treated with immediately available fertilizer showed the greatest growth response but in the second growing season only the controlled release fertilizer application resulted in growth rates greater than the controls. Fertilizer regime had similar effects on total cover of competing vegetation, although fertilization additionally promoted increased cover of grasses in the forest floor mineral mix. Overall, we clearly show that nutrient loaded trembling aspen seedlings can be used to offset early field fertilization needs at forest reclamation sites.

Early successional plant community dynamics on a reclaimed oil sands mine in comparison with natural boreal forest communities

ABSTRACTForming the majority of plant diversity in boreal forests, understory communities are important drivers of nutrient cycling and overstory succession. In western Canadian boreal forests, fire is the primary mechanism of natural disturbance, with oil sands mining a substantial anthropogenic disturbance in north-eastern Alberta. An operational reclamation trial, at an oil sands mine, was established the same year as a nearby forest fire, allowing for direct comparison of plant community development between reclaimed and naturally regenerated fire-origin and mature stands. This work reflects a case study with large, but unreplicated, areas of both fertilized and unfertilized reclamation treatments on forest floor-mineral mix (FFMM) and peat-mineral mix (PMM) capping materials. After three years, reclamation sites are compositionally distinct from post-fire and mature natural stands, with more non-native species in reclamation treatments than in natural stands. Communities developing on FFMM are more similar to post-fire successional communities than those on PMM, with high species richness and diversity on FFMM comparable with post-fire stands. Cover soil had a stronger impact on plant community development than fertilization, with fertilization effects dependent on cover soil. A standard dose of fertilizer lowered richness and diversity on FFMM and is not recommended for use with that soil.

Maximizing Natural Trembling Aspen Seedling Establishment on a Reclaimed Boreal Oil Sands Site

Actively facilitating the natural establishment of trees on reclamation sites is seen as an important step in ecosystem recovery after oil sands mining. We examined the effect of different reclamation prescriptions, including two soil types (peat-mineral mix and forest floor-mineral mix) and two fertilizer levels (200 kg N ha–1 and no fertilizer), on naturally established trembling aspen ( Populus tremuloides ) seedlings and other deciduous trees. Aspen has a tiny, windblown seed which is very sensitive to moisture stress during establishment. Seedling establishment was greatest on peat-mineral mix soil with no fertilizer application and was related to the increased surface roughness and soil moisture and lack of vegetation competition with this soil prescription. Surprisingly, seedling establishment was not related to microsite characteristics such as concavity. Once established, average seedling height was not significantly different among soil types or fertilization treatments. Overall, using peat-mineral mix soil and increasing surface roughness offer a starting point for developing best management practices for facilitating natural deciduous tree seedling establishment in this region.

Tracing biogeochemical and microbial variability over a complete oil sand mining and recultivation process

Recultivation of disturbed oil sand mining areas is an issue of increasing importance. Nevertheless only little is known about the fate of organic matter, cell abundances and microbial community structures during oil sand processing, tailings management and initial soil development on reclamation sites. Thus the focus of this work is on biogeochemical changes of mined oil sands through the entire process chain until its use as substratum for newly developing soils on reclamation sites. Therefore, oil sand, mature fine tailings (MFTs) from tailings ponds and drying cells and tailings sand covered with peat–mineral mix (PMM) as part of land reclamation were analyzed. The sample set was selected to address the question whether changes in the above-mentioned biogeochemical parameters can be related to oil sand processing or biological processes and how these changes influence microbial activities and soil development.GC–MS analyses of oil-derived biomarkers reveal that these compounds remain unaffected by oil sand processing and biological activity. In contrast, changes in polycyclic aromatic hydrocarbon (PAH) abundance and pattern can be observed along the process chain. Especially naphthalenes, phenanthrenes and chrysenes are altered or absent on reclamation sites. Furthermore, root-bearing horizons on reclamation sites exhibit cell abundances at least ten times higher (108 to 109cellsg−1) than in oil sand and MFT samples (107cellsg−1) and show a higher diversity in their microbial community structure. Nitrate in the pore water and roots derived from the PMM seem to be the most important stimulants for microbial growth. The combined data show that the observed compositional changes are mostly related to biological activity and the addition of exogenous organic components (PMM), whereas oil extraction, tailings dewatering and compaction do not have significant influences on the evaluated compounds. Microbial community composition remains relatively stable through the entire process chain.

Soil quality assessment for peat-mineral mix cover soil used in oil sands reclamation.

A soil quality (SQ) assessment and rating framework that is quantitative, iterative, and adaptable, with justifiable weighting for quality scores, is required for evaluating site-specific SQ at land reclamation sites. Such a framework needs to identify the minimum dataset that reflects the current knowledge regarding relationships between SQ indicators and relevant measures of ecosystem performance. Our objective was to develop nonlinear scoring functions for assessing the impact on SQ of peat-mineral mix (PMM) used as a cover soil at land reclamation sites. Soil functional indicators affected by PMM were extracted from existing databases and correlated with soil organic carbon (SOC). Based on defined objectives for SQ assessment, indicators with significant correlation ( < 0.05) to SOC were selected, normalized, and fitted to sigmoid functions using nonlinear regression procedure to establish SQ functions (SQFs) that can analyze changes in field capacity, permanent wilting point, soil nitrogen, and cation exchange capacity of PMM using SOC as input parameter. Application of the SQFs to an independent dataset produced ratings with mean differences similar to the treatment effects of mixing three levels of peat and mineral soil. These results show that derived ratings and weighing factors using SOC reflect the relationship between PMM treatment and other SQ indicators. Applying the developed SQFs to a long-term soil monitoring dataset shows that an increase or decrease in SOC from 10 to 20 g kg causes a significant change in SQ. This identifies the need for further nutrient and moisture management of PMM to support long-term SQ development in land reclamation.

Do peat amendments to oil sands wet sediments affect Carex aquatilis biomass for reclamation success?

The oil sands industries of Alberta (Canada) have reclamation objectives to return the mined landscape to equivalent pre-disturbance land capability. Industrial operators are charged with reclaiming a vast landscape of newly exposed sediments on saline-sodic marine-shales sediments. Incorporated in these sediments are by-products resulting from bitumen extraction (consolidated tailings (CT), tailings-sand (TS), and oil sands processed water (OSPW)). A sedge community dominated by Carex aquatilis was identified as a desirable and representative late-succession community for wet-meadow zones of oil sands-created marshes. However, the physical and chemical conditions, including high salinity and low nutrient content of CT and TS sediments suppress plant growth and performance. We experimentally tested the response of C. aquatilis to amendments with peat-mineral-mix (PM) on oil sand sediments (CT and TS). In a two factorial design experiment, we also tested the effects of OSPW on C. aquatilis. We assessed survival, below- and aboveground biomass, and physiology (chlorophyll a fluorescence). We demonstrated that PM amendments to oil sands sediments significantly increased C. aquatilis survival as well as below and aboveground biomass. The use of OSPW significantly reduced C. aquatilis belowground biomass and affected its physiological performance. Due to its tolerance and performance, we verified that C. aquatilis was a good candidate for use in reclaiming the wet-meadow zones of oil sands-created marshes. Ultimately, amending CT and TS with PM expedited the reclamation of the wetland to a C. aquatilis-community which was similar in gross structure to undisturbed wetlands of the region.