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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Evaluating Tire Pressure Control System to Improve Productivity and Mitigate Pavement Damage

Mabood, Fazal 08 September 2008 (has links)
The introduction of the use of Tire Pressure Control Systems (TPCS) to improve the productivity of the Canadian trucking industry is gaining momentum. The imposition of seasonal load restrictions (SLR) on the thaw-weakened secondary roads interrupts the transportation of raw materials to processing facilities For the forestry industry in particular, this has very significant impacts on productivity and costs. FPInnovations-Feric Division (Feric) has investigated the potential for TPCS-equipped trucks to travel with full, legal loading during the SLR period without accelerating road wear and tear. The TPCS monitors and adjusts the inflation pressure of the trucks’ tires while driving and allows the operator to optimize the inflations for changes in loading, travel speed, or road quality encountered in the trip. This thesis describes an investigation to determine whether TPCS can be used to mitigate traffic generated damage to secondary roads and also reduce the need to implement load restrictions. The project involves a partnership with the Ontario Ministry of Transportation Ontario (MTO), Forest Engineering Research Institute of Canada (FERIC), Ontario Ministry of Natural Resources (MNR) and the Centre for Pavement and Transportation Technology (CPATT) located at the University of Waterloo. The thesis will describe the methodology, design, and instrumentation of the two test sites which are located in Dryden, Ontario and Chapleau, Ontario. In addition, repeated Portable Falling Weight Deflectometer (PFWD) testing is being carried out at these sites and the initial results of this examination and associated impacts of the environment and traffic on the road will be presented. This study also involves looking into the reliability of using the portable FWD, offering a lower cost alternative instead of the trailer mounted FWD to monitor pavement strength for the identification the SLR period. The use of innovative sensors and data collection techniques are proving to be very informative and are advancing pavement engineering knowledge. Moreover, the thesis is aimed at exploring the possibilities of achieving the current objectives of the government DOTs such as TPCS potential for addressing the timber industry in crisis, reduced road maintenance budgets, and global warming increasing road damage.
42

Deterioration mechanisms of historic cement renders and concrete

Griffin, Isobel Margaret January 2013 (has links)
Since the introduction of Portland cement in the early nineteenth century the number of buildings constructed from concrete or using cement mortars and renders has grown exponentially, and cement is one of the most common building materials in use today. Consequently a significant proportion of the built heritage contains cementitious materials. The relative youth of these buildings means that less research has been undertaken to understand how and why they deteriorate than for traditional buildings, and that the development of appropriate conservation methods and techniques is less advanced. The primary aim of this research was to understand the causes and mechanisms of some of the types of deterioration commonly found in historic concrete and cement buildings and structures, with reference to the Second World War reinforced concrete and cement-rendered buildings at East Fortune airfield in East Lothian, Scotland. Additional aims were to investigate the efficacy of the building repairs and maintenance regimes undertaken to date, and to make recommendations for the future conservation of the buildings. East Fortune airfield contains a number of cement-rendered brick masonry buildings and a reinforced concrete air raid shelter. The initial visual survey identified several types of deterioration, from which the blistering and flaking of the render; the cracking and delamination of the render; and the spalling of the concrete in the air raid shelter were selected for further research. The research included time lapse photography, non-destructive testing, environmental monitoring and the physical, chemical and petrographic characterisation of the building materials. Hypotheses regarding the causes of deterioration were tested in the laboratory, for example with linear variable displacement transducer measurements, and modelled using crack propagation theories and models for water transport through porous media. It is demonstrated that the blistering and flaking of the render is caused by shale aggregate particles, which undergo sufficient expansion during freeze-thaw cycles to crack the surrounding render. This phenomenon is termed ‘pop-outs’ in the concrete literature. The more catastrophic cracking and delamination of the renders is also due to freeze-thaw cycling, which is shown to cause significant damage provided the moisture content of the render is above a certain threshold level. This type of deterioration has occurred at an accelerated rate for some of the modern render repairs, due to an inadequate understanding of the properties of the original and repair materials. In particular, the properties of the bricks are critical to the performance of the cement renders, and it is found that the sorptivity of historic bricks may vary considerably depending upon the orientation of the brick. Finally, the diagnosis for the air raid shelter is that the corrosion of the steel reinforcements is caused by high levels of chlorides present within the raw materials used to make the pre-cast concrete sections. The results of the investigations are used to suggest building conservation solutions for this particular site. Furthermore, since the deterioration mechanisms investigated are common for historic cement and concrete, the findings are relevant to many other sites. The over-arching methodology used to investigate the deterioration at the site and the methodologies developed to test particular hypotheses are also applicable for other investigations of historic building materials. There is much about this research that is innovative and new. The work on render cracking compares the results of dilation tests on cementitious and ceramic materials, which has not been done previously, and the pop-outs diagnosed in the work on render flaking have rarely, if ever, been reported for cement renders. The modelling work undertaken to quantify the stresses produced by the pop-outs and to explain the inclined crack formation patterns is entirely original. The use of petrography to diagnose causes of render failure is described in the literature, but this is one of very few case studies to be written up, and the work on the air raid shelter constitutes the only formal investigation of this type of Stanton shelter.
43

Teplotní a vlhkostní režim strukturních půd Vysokých Tater / Thermal and moisture regime of patterned ground in the High Tatras

Pechačová, Blanka January 2013 (has links)
6 ABSTRACT Thermal and moisture regime of patterned ground is closely associated with the presence of the regelation phenomenon. Generally, the regelation includes all processes leading to the water freeze-thaw alternations in soil or bedrock. As a result of cyclic freezing and thawing of soil water under specific conditions, processes, such a moisture migration, ice segregation or frost heaving, operate. Termal and moisture regime is the main factor of these processes and consequentely, of the patterned ground formation. The submited diploma thesis is concerned with thermal and moisture regime of patterned ground in the High Tatras. The main aims of the thesis was to characterize thermal and moisture regime of patterned ground, to evaluate and confront the patterned ground regelation activity depending on the diverse soil depths and different types of the patterned ground and to evaluate the soil temperature relationship to the air temperatures, soil moisture content and the water level regime of the nearest lakes. The partial purpose of the thesis was to assess the applicability of different methods of the regelation cycle determination based on the soil temperature measurements. During the study period 2007 - 2012 the regelation activity of sorted paterned ground (Hincove oká, Lúčne sedlo and Skalnaté...
44

Freeze-Thaw Resistance of Concrete : Effect of: Curing Conditions, Moisture Exchange and Materials

Rønning, Terje F. January 2001 (has links)
<p>Research on freeze-thaw resistance of concrete in general and on curing and moisture conditions in particular is motivated from an economic and product sustainability point of view. Specifically, it is argued for the importance of considering the effect of curing and test exposure conditions on the moisture uptake and performance during freeze-thaw. Due to the demonstrated importance of moisture conditions on performance, they should be related to those of field service conditions when choosing a test procedure in a particular case. This is vital for adequate testing of new</p><p>and more sustainable concrete materials.</p>
45

Freeze-Thaw Resistance of Concrete : Effect of: Curing Conditions, Moisture Exchange and Materials

Rønning, Terje F. January 2001 (has links)
Research on freeze-thaw resistance of concrete in general and on curing and moisture conditions in particular is motivated from an economic and product sustainability point of view. Specifically, it is argued for the importance of considering the effect of curing and test exposure conditions on the moisture uptake and performance during freeze-thaw. Due to the demonstrated importance of moisture conditions on performance, they should be related to those of field service conditions when choosing a test procedure in a particular case. This is vital for adequate testing of new and more sustainable concrete materials.
46

Examination of a novel proteinaceous extract from winter rye (<i>Secale cereale</i> L. cv Musketeer)

Lim, Ze Long 11 April 2011
A gel is a cross-linked polymer network that spans an entire liquid medium; its properties depend strongly on the interaction of the polymer and the liquid medium. There are various ways to induce gelation in different systems such as altering temperature or pH. In this study, phenol extracted protein fractions from non-acclimated (NA) and cold-acclimated (CA) winter rye (Secale cereale L. cv Musketeer) leaf tissue were subjected to freeze-thaw treatment. Gelation was induced in the NA and CA extracts after repeated freeze-thaw treatments, accompanied by a change in sample rheological properties. Further experimentation revealed that gel formation only occurred at high pH (pH 12.0) and that a minimum of 3 to 4 freeze-thaw cycles were required. The viscosity of the protein gel increased 5.7- to 9.5-fold in the NA and CA extracts respectively upon freeze-thaw. Experiments optimizing the extraction conditions and protein concentration were also performed. The gel was stable and only a specific combination of chaotropic agent, anionic surfactant and reducing agent such as urea, sodium docecyl sulfate (SDS) and â-mercaptoethanol (â-ME) with heating could disrupt the gel network. The gel was composed of several proteins in the extracts as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Based on SDS-PAGE analysis, ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) was identified as the major protein component in the gel. Various experiments were performed to assess the role of Rubisco in gel formation; however, the results were inconclusive. It is suggested that these extracts may contain antifreeze proteins (AFPs) that have been demonstrated to form amyloid gels upon freeze-thaw. Further studies examining the composition and mechanism of gel formation may result in a future role for this material in the food industry.
47

Greenhouse gas emission from a Prairie pothole landscape in Western Canada

Dunmola, Adedeji Samuel 10 April 2007 (has links)
Knowing the control of landscape position in greenhouse gas (GHG) emission from the Prairie pothole region is necessary to provide reliable emission estimates needed to formulate strategies for reducing emission from the region. Presented here are results of a study investigating the control of landscape position on the flux of nitrous oxide (N2O) and methane (CH4) from an agricultural soil. Field flux of N2O and CH4 and associated soil parameters from the Upper, Middle, Lower and Riparian slope positions were monitored from spring to fall of 2005, and spring of 2006, at the Manitoba Zero-Tillage Research Association (MTRZA) farm, 17.6km North of Brandon, MB. The field site consisted of a transect of 128 chambers segmented into the four landscape positions, with either all chambers or a subset of the chambers (32) sampled on select days. Spring thaw is an important period for annual inventory of N2O emission, thus, soil samples were also collected from the four slope positions in fall 2005, and treated in the laboratory to examine how antecedent moisture and landscape position affect the freeze-thaw emission of N2O from soil. Daily emissions of N2O and CH4 for 2005 were generally higher than for 2006, the former being a wetter year. There was high temporal variability in N2O and CH4 emission, with high fluxes associated with events like spring thaw and fertilizer application in the case of N2O, and rapid changes in soil moisture and temperature in the case of CH4. There was a high occurrence of hotspots for N2O emission at the Lower slope, associated with its high soil water-filled porosity (WFP) and carbon (C) availability. The Riparian zone was not a source of N2O emission, despite its soil WFP and organic C being comparable with the Lower slope. The hotspot for CH4 emission was located at the Riparian zone, associated with its high soil WFP and C availability. The Upper and Middle slope positions gave low emission or consumed CH4, associated with having low soil WFP and available C. This pattern in N2O and CH4 emission over the landscape was consistent with examination of entire 128 chambers on the transect or the 32 subset chambers. Significantly lowering the antecedent moisture content of soil by drying eliminated the freeze-thaw emission of N2O, despite the addition of nitrate to the soil. This was linked to drying slightly reducing the denitrifying enzyme activity (DEA) of soil. The highest and earliest freeze-thaw emission of N2O was from the Riparian zone, associated with its high antecedent moisture content, DEA and total organic C content. The addition of nitrate to soil before freezing failed to enhance freeze-thaw emission of N2O from the Upper, Middle and Lower slope positions, but increased emission three-fold for the Riparian zone. Despite the greater potential of the Riparian zone to produce N2O at thaw compared to the Upland slopes, there was no spring-thaw emission of N2O from the zone on the field. This was because this zone did not freeze over the winter, due to insulation by high and persistent snow cover, vegetation and saturated condition. The denitrifying potential and freeze-thaw N2O emission increased in going from the Upper to the Lower slope position, similar to the pattern of N2O emission observed on the field. The localization of hotspots for N2O and CH4 emission within the landscape was therefore found to be driven by soil moisture and C availability. When estimating GHG emission from soil, higher emission index for N2O and CH4 should be given to poorly-drained cropped and vegetated areas of the landscape, respectively. The high potential of the Riparian zone for spring-thaw emission of N2O should not be discountenanced when conducting annual inventory of N2O emission at the landscape scale. When fall soil moisture is high, snow cover is low, and winter temperature is very cold, freeze-thaw emission of N2O at the Riparian zones of the Prairie pothole region may be very high. / May 2007
48

Abiotic Stresses to Vegetation Re-establishment in a Cutover Bog Contaminated with Seawater

Montemayor, Marilou B. January 2006 (has links)
Part of a cutover bog in Pokesudie Island, New Brunswick, Canada was contaminated with seawater and was still largely devoid of vegetation 5 years after the event and was consequently chosen for study. The study area consisted of rectangular fields with cambered surface that sloped down (2%) to the drainage ditches on both sides. Across this slope zones were created: Up-, Mid- and Low- areas on either side of the centerline of fields. Two field experiments were conducted to determine abiotic stresses to plant re-establishment in terms of hydrology and peat characteristics along this cambered surface. The general objective was to identify microsites or zones that could be suitable to the introduction of wetland halophytes <em>Juncus balticus</em> Willd. and <em>Spartina pectinata</em> Link obtained from nearby salt marshes. <br /><br /> In the first experiment, cylindrical <em>J. balticus</em> sods were transplanted into the Up- and Low- areas, at 1, 3, 5, 10 and 20 d of incubation (in May 2005) with measurements made on the Outer and Inner annular sod sections, replicated over 4 blocks. Moisture (% dry weight basis (dwb)) reached maximum values 1 day after transplantation, 84±0. 05 for Outer and 103±0. 07 for Inner sod section. Salinity (dS m<sup>-1</sup>) in sods due to ingress of sodium (Na<sup>+</sup> ) and chloride (Cl<sup>-</sup>) reached values of the surrounding peat 3 days after transplantation, 3. 52±1. 06 for Inner sod section and 4. 11±0. 99 for Outer sod section in Up-areas, and 1. 76±0. 24 for Inner sod section and 2. 57±0. 28 for Outer sod section in Low-areas. Maximum decrease in pH was at 5 days after transplantation, in Outer sod section in the Up-areas (from 5. 89 to 4. 88±0. 14) which was much higher than the pH range of 3-4 of the surrounding peat. This was due to the buffering capacity of calcium (Ca<sup>2+</sup>) and magnesium (Mg<sup>2+</sup>) in sods which did not change in concentration after 20 days of incubation. Therefore, Inner sod sections were less affected by the surrounding peat compared to the Outer sod sections, suggesting that a larger sod volume may alleviate stressful conditions for a longer time at transplantation and consequently allow greater time for adaptation. <br /><br /> In the second experiment, <em>J. balticus</em> and <em>S. pectinata</em> were transplanted on the 3 Locations Up-, Mid- and Low- areas, replicated over 10 blocks; and peat characteristics were measured at Depths 0-5, 5-10, 10-15 and 15-20 cm 5 times during the study period May-August 2005. Survival of <em>J. balticus</em> was poorest (27. 5±8. 3 %) in the Low-areas compared to 68. 5±8. 9 % in the Up- and 58. 5±8. 7% in the Mid- areas. <em>S. pectinata</em> survival was very good at all Locations (89±5. 3, 91. 6±3. 1 and 84. 2±4. 4 for Up-, Mid- and Low- areas, respectively) having better adaptation to early season waterlogged conditions. Waterlogged conditions resulted from a perched water table during the early part of the growing season (May-June) and were alleviated only upon the complete thaw of the frozen peat layer on 8 July. Thereafter, important changes in hydrology and peat characteristics occurred: water table depths decreased from -8. 5±1. 7 and -1. 6±1. 2 cm on 26 May, to -51. 5±2. 5 and -40. 7±2. 4 cm by 9 August in Up- and Low-areas, respectively; redox potentials at 12 cm depth increased from 26 June (190. 9±8, 175±10. 8 and 109. 2±29. 4 mV) to 9 August (282. 8±8, 302. 8±14. 3 and 312. 3±29. 6 mV) in the Up-, Mid- and Low-areas, respectively which showed that anaerobic conditions were maintained throughout the study period; decreased moisture content from 1256. 8±61. 9, 1667. 4±126. 3 and 1728. 6±153 on 30 May, to 851. 7±21. 2, 874. 6±47 and 1008. 2±57. 5 % dwb on 25 July) which caused increased dry bulk density (from 0. 07±0. 002, 0. 06±0. 003 and 0. 07±0. 01 to 0. 09±0. 003, 0. 09±0. 005 and 0. 08±0. 004) in the Up-, Mid- and Low-areas, respectively; and increased electrical conductivity (salinity) especially on the 0-5cm surface (from 1. 9±0. 13, 1. 8±0. 31 and 1. 5±0. 29 to 18±1. 9, 17. 5±1. 1 and 12. 2±1 dS m<sup>-1</sup>) which also caused decreased pH (from 3. 5±0. 04, 3. 5±0. 08 and 3. 6±0. 01 to 2. 85±0. 04, 2. 85±0. 01 and 2. 9±0. 03) in the Up-, Mid- and Low-areas, respectively. Therefore, spring flooding followed by high surface salinity in summer precludes plant establishment by seeding and explains the current lack of spontaneous revegetation. Waterlogged conditions were of greater magnitude and duration at lower elevation areas unfavourable to <em>J. balticus</em> survival but salinity levels were high in the Up- and Mid-areas. <br /><br /> In the subsequent part of the second experiment, plants of <em>J. balticus</em> and <em>S. pectinata</em> grown in the study area and those collected from marshes were divided into above- and below- ground parts and accumulation of salt ions in plant tissues were determined to understand the species' salt-tolerance mechanism, as well as the accumulation of potentially toxic levels of iron (Fe) and manganese (Mn). Both plant species had similar accumulations (mmol kg<sup>-1</sup> dry wt,) of Na<sup>+</sup> (474. 3±41 and 468. 3±31. 7, respectively) and Cl<sup>-</sup> (314. 9±21. 9 and 310. 5±27. 5, respectively) in the above-ground parts but differed in how they managed Na<sup>+</sup>. <em>J. balticus</em> accumulated more Na<sup>+</sup> in below-ground parts (659. 3±88. 7) and had limited transport to the above-ground parts, while <em>S. pectinata</em> accumulated and excreted Na<sup>+</sup> in the above-ground parts and had less accumulation in the below-ground parts (397. 4±25. 1). <em>S. pectinata</em> maintained (313. 1±23. 8 in marsh <em>vs. </em> 292. 4±26. 2 in bog) and <em>J. balticus</em> increased (84. 2±1. 2 in marsh <em>vs. </em> 531. 2±38. 6 in bog) K<sup>+</sup>-selectivity in the shoots, a key requirement for survival in saline conditions. Compared with their respective marsh plants, <em>S. pectinata</em> had more salinity-tolerance than <em>J. balticus</em> primarily through its maintenance of Ca<sup>2+</sup> (21. 5±1. 7 in marsh <em>vs. </em> 35. 6±3. 8 in bog) compared to a decrease in <em>J. balticus</em> (144. 7±12. 5 in marsh <em>vs. </em> 41±3. 7 in bog). Furthermore, Fe and Mn uptake in both species decreased but reached critical Fe-deficiency levels (1. 1±0. 1 mmol kg<sup>-1</sup> dry wt,) only in <em>S. pectinata</em> grown in drier areas. <br /><br /> It is concluded that local conditions of waterlogging (especially in lower elevation areas) and high salinity and low pH (notably in the upper elevation areas) were favourable to the survival of <em>S. pectinata</em> in all areas and <em>J. balticus</em> only in upper elevation areas. Sod transplanting may alleviate the acidity problem and depending on sod volume may delay the effects of harsh conditions of the cutover bog. However, long-term survival and growth of both species in drier areas may be constrained by deficiency in calcium in <em>J. balticus</em> and iron in <em>S. pectinata</em>.
49

Porous Asphalt Pavement Designs: Proactive Design for Cold Climate Use

Schaus, Lori Kathryn January 2007 (has links)
Porous asphalt pavements offer an alternative technology for stormwater management. A porous asphalt pavement differs from traditional asphalt pavement designs in that the structure permits fluids to pass freely through it, reducing or controlling the amount of run-off from the surrounding area. By allowing precipitation and run-off to flow through the structure, this pavement type functions as an additional stormwater management technique. The overall benefits of porous asphalt pavements may include both environmental and safety benefits including improved stormwater management, improved skid resistance, reduction of spray to drivers and pedestrians, as well as a potential for noise reduction. With increasing environmental awareness and an evolving paradigm shift in stormwater management techniques, this research aims to provide guidance for Canadian engineers, contractors, and government agencies on the design of porous asphalt pavement structures. One of the keys to the success of this pavement type is in the design of the asphalt mix. The air void percentage, which is ultimately related to the effectiveness of the pavement to adequately control the runoff, is a critical component of the mix. However, special consideration is required in order to obtain higher air void percentages while maintaining strength and durability within a cold climate. The objectives of this study were to evaluate several laboratory porous asphalt mix designs for durability and strength in cold climate conditions. The porous asphalt mixes consisted of a porous asphalt Superpave mix design method whereby the asphalt binder type was varied. Performance testing of the porous asphalt including draindown susceptibility, moisture-induced damage susceptibility, dynamic modulus, and permeability testing were completed. Based on the preliminary laboratory results, an optimal porous asphalt mix was recommended for use in a Canadian climate. Initial design guidelines for porous asphalt were provided based on preliminary findings and hydrological analysis.
50

Abiotic Stresses to Vegetation Re-establishment in a Cutover Bog Contaminated with Seawater

Montemayor, Marilou B. January 2006 (has links)
Part of a cutover bog in Pokesudie Island, New Brunswick, Canada was contaminated with seawater and was still largely devoid of vegetation 5 years after the event and was consequently chosen for study. The study area consisted of rectangular fields with cambered surface that sloped down (2%) to the drainage ditches on both sides. Across this slope zones were created: Up-, Mid- and Low- areas on either side of the centerline of fields. Two field experiments were conducted to determine abiotic stresses to plant re-establishment in terms of hydrology and peat characteristics along this cambered surface. The general objective was to identify microsites or zones that could be suitable to the introduction of wetland halophytes <em>Juncus balticus</em> Willd. and <em>Spartina pectinata</em> Link obtained from nearby salt marshes. <br /><br /> In the first experiment, cylindrical <em>J. balticus</em> sods were transplanted into the Up- and Low- areas, at 1, 3, 5, 10 and 20 d of incubation (in May 2005) with measurements made on the Outer and Inner annular sod sections, replicated over 4 blocks. Moisture (% dry weight basis (dwb)) reached maximum values 1 day after transplantation, 84±0. 05 for Outer and 103±0. 07 for Inner sod section. Salinity (dS m<sup>-1</sup>) in sods due to ingress of sodium (Na<sup>+</sup> ) and chloride (Cl<sup>-</sup>) reached values of the surrounding peat 3 days after transplantation, 3. 52±1. 06 for Inner sod section and 4. 11±0. 99 for Outer sod section in Up-areas, and 1. 76±0. 24 for Inner sod section and 2. 57±0. 28 for Outer sod section in Low-areas. Maximum decrease in pH was at 5 days after transplantation, in Outer sod section in the Up-areas (from 5. 89 to 4. 88±0. 14) which was much higher than the pH range of 3-4 of the surrounding peat. This was due to the buffering capacity of calcium (Ca<sup>2+</sup>) and magnesium (Mg<sup>2+</sup>) in sods which did not change in concentration after 20 days of incubation. Therefore, Inner sod sections were less affected by the surrounding peat compared to the Outer sod sections, suggesting that a larger sod volume may alleviate stressful conditions for a longer time at transplantation and consequently allow greater time for adaptation. <br /><br /> In the second experiment, <em>J. balticus</em> and <em>S. pectinata</em> were transplanted on the 3 Locations Up-, Mid- and Low- areas, replicated over 10 blocks; and peat characteristics were measured at Depths 0-5, 5-10, 10-15 and 15-20 cm 5 times during the study period May-August 2005. Survival of <em>J. balticus</em> was poorest (27. 5±8. 3 %) in the Low-areas compared to 68. 5±8. 9 % in the Up- and 58. 5±8. 7% in the Mid- areas. <em>S. pectinata</em> survival was very good at all Locations (89±5. 3, 91. 6±3. 1 and 84. 2±4. 4 for Up-, Mid- and Low- areas, respectively) having better adaptation to early season waterlogged conditions. Waterlogged conditions resulted from a perched water table during the early part of the growing season (May-June) and were alleviated only upon the complete thaw of the frozen peat layer on 8 July. Thereafter, important changes in hydrology and peat characteristics occurred: water table depths decreased from -8. 5±1. 7 and -1. 6±1. 2 cm on 26 May, to -51. 5±2. 5 and -40. 7±2. 4 cm by 9 August in Up- and Low-areas, respectively; redox potentials at 12 cm depth increased from 26 June (190. 9±8, 175±10. 8 and 109. 2±29. 4 mV) to 9 August (282. 8±8, 302. 8±14. 3 and 312. 3±29. 6 mV) in the Up-, Mid- and Low-areas, respectively which showed that anaerobic conditions were maintained throughout the study period; decreased moisture content from 1256. 8±61. 9, 1667. 4±126. 3 and 1728. 6±153 on 30 May, to 851. 7±21. 2, 874. 6±47 and 1008. 2±57. 5 % dwb on 25 July) which caused increased dry bulk density (from 0. 07±0. 002, 0. 06±0. 003 and 0. 07±0. 01 to 0. 09±0. 003, 0. 09±0. 005 and 0. 08±0. 004) in the Up-, Mid- and Low-areas, respectively; and increased electrical conductivity (salinity) especially on the 0-5cm surface (from 1. 9±0. 13, 1. 8±0. 31 and 1. 5±0. 29 to 18±1. 9, 17. 5±1. 1 and 12. 2±1 dS m<sup>-1</sup>) which also caused decreased pH (from 3. 5±0. 04, 3. 5±0. 08 and 3. 6±0. 01 to 2. 85±0. 04, 2. 85±0. 01 and 2. 9±0. 03) in the Up-, Mid- and Low-areas, respectively. Therefore, spring flooding followed by high surface salinity in summer precludes plant establishment by seeding and explains the current lack of spontaneous revegetation. Waterlogged conditions were of greater magnitude and duration at lower elevation areas unfavourable to <em>J. balticus</em> survival but salinity levels were high in the Up- and Mid-areas. <br /><br /> In the subsequent part of the second experiment, plants of <em>J. balticus</em> and <em>S. pectinata</em> grown in the study area and those collected from marshes were divided into above- and below- ground parts and accumulation of salt ions in plant tissues were determined to understand the species' salt-tolerance mechanism, as well as the accumulation of potentially toxic levels of iron (Fe) and manganese (Mn). Both plant species had similar accumulations (mmol kg<sup>-1</sup> dry wt,) of Na<sup>+</sup> (474. 3±41 and 468. 3±31. 7, respectively) and Cl<sup>-</sup> (314. 9±21. 9 and 310. 5±27. 5, respectively) in the above-ground parts but differed in how they managed Na<sup>+</sup>. <em>J. balticus</em> accumulated more Na<sup>+</sup> in below-ground parts (659. 3±88. 7) and had limited transport to the above-ground parts, while <em>S. pectinata</em> accumulated and excreted Na<sup>+</sup> in the above-ground parts and had less accumulation in the below-ground parts (397. 4±25. 1). <em>S. pectinata</em> maintained (313. 1±23. 8 in marsh <em>vs. </em> 292. 4±26. 2 in bog) and <em>J. balticus</em> increased (84. 2±1. 2 in marsh <em>vs. </em> 531. 2±38. 6 in bog) K<sup>+</sup>-selectivity in the shoots, a key requirement for survival in saline conditions. Compared with their respective marsh plants, <em>S. pectinata</em> had more salinity-tolerance than <em>J. balticus</em> primarily through its maintenance of Ca<sup>2+</sup> (21. 5±1. 7 in marsh <em>vs. </em> 35. 6±3. 8 in bog) compared to a decrease in <em>J. balticus</em> (144. 7±12. 5 in marsh <em>vs. </em> 41±3. 7 in bog). Furthermore, Fe and Mn uptake in both species decreased but reached critical Fe-deficiency levels (1. 1±0. 1 mmol kg<sup>-1</sup> dry wt,) only in <em>S. pectinata</em> grown in drier areas. <br /><br /> It is concluded that local conditions of waterlogging (especially in lower elevation areas) and high salinity and low pH (notably in the upper elevation areas) were favourable to the survival of <em>S. pectinata</em> in all areas and <em>J. balticus</em> only in upper elevation areas. Sod transplanting may alleviate the acidity problem and depending on sod volume may delay the effects of harsh conditions of the cutover bog. However, long-term survival and growth of both species in drier areas may be constrained by deficiency in calcium in <em>J. balticus</em> and iron in <em>S. pectinata</em>.

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