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No description available.

To investigate the prevalence and magnitude of hydrophobicity in near-surface peat, a poor fen was characterized into four main post-fire microforms: i) severely burned hollows (SB-H), ii) severely burned Sphagnum fuscum hummocks (SB-Sf), iii) lightly burned S. fuscum hummocks (LB-Sf) and, iv) lightly burned feathermoss lawns (LB-F). The SB-H possessed the most hydrophobicity at the surface (85 ± 20 s) and increased at the 2 cm depth (183 ± 35 s). In comparison, the LB-F experienced an increase in hydrophobicity from the surface (44 ± 10 s) to 5 cm (323 ± 32 s) and remained high to the 10 cm depth (211 ± 31 s). Results on Sphagnum recovery show that only LB-Sf are recovering and the SB-H show marginal recovery of pioneer species such as Ceratodon purpureus and Polytrichum strictum. Moreover, S. fuscum had a mean surface cover of 56 ± 5.9% in the LB-Sf and both pioneer species together possessed a total cover of 15 ± 4.4% in the SB-H. While the vascular cover was correlated with increased transplant productivity which in conjunction with moisture availability (preference for hydrophilic substrate), transplant size (15cm diameter preferred over smaller colonies), and transplant location (SB-H preferred over LB-F) should all lead to decreased mortality in treatments. However, each species possesses slightly different characteristics that may be more desirable under reclamation conditions. Species that typically form hummock microform types like Sphagnum fuscum, Sphagnum magellanicum, and to some extent Sphagnum angustifolium can retain moisture under dry conditions (Clymo and Hayward, 1982; Andrus, 1986) and may be optimal for areas experiencing droughts or water limitations. Areas that are commonly inundated with water may benefit from a species that grows through lateral expansion such as Sphagnum angustifolium, Sphagnum riparium, or Sphagnum squarrosum (Andrus, 1986). With S. angustifolium possibly being the best generalist due to its ability to remain photosynthetically active throughout a large range of moisture contents, tolerate desiccation, and grow rapidly (Silvola and Aaltonen, 1984; Andrus, 1986). / Thesis / Master of Science (MSc)

Vacuum harvested peatlands typically do not spontaneously regenerate peatland species and more importantly the peat-forming Sphagnum mosses. Thus harvested and abandoned peatlands require restoration to return the peat-forming Sphagnum moss to the ecosystem. Restoration can create a hydrological environment that is suitable for peatland species’ regeneration and results in substantial Sphagnum moss growth. Bois-des-Bel was restored in the winter of 1999 and studied in the following three years (2000-2002), then again after 10 years (this study). Immediately following restoration the conditions were deemed favourable for Sphagnum regeneration (i.e. soil water pressures and water tables, > -100 cm and -40 cm respectively) (~ 15-20 cm in 10 years), while evaporation from the surface was reduced due to the straw mulch that was applied as part of the restoration measures. Although the hydrological conditions were suitable for peat revegetation, Bois-des-Bel was still a net exporter of carbon during first three years. The purpose of this thesis is to understand the hydrological evolution of Bois-des-Bel since the initial assessments and document the hydrophysical properties that could limit net carbon sequestration. This is done with a combination of field and laboratory (monolith) experiments through comparison of its hydrology and hydraulic parameters to that of a natural reference site. Since the initial assessment a water table rise of ~ 5-10 cm has occurred at the Restored site with an average water table of -27.3 (± 14.9) with respect to the cutover peat (pre-restoration surface) and ~ -42.3 (± 20.9) cm with respect to the regenerated Sphagnum surface. This water table is still much further from the capitula and more variable than at the Natural site (33.2 ± 9.0 cm). Both evapotranspiration (242 mm) and runoff (7 mm) from the Restored site maintained the same relationships in 2010 as during the initial assessments, compared to the Unrestored site (290mm and 37 mm, respectively). Although lower evapotranspiration equated to less water lost from the system, evapotranspiration at the Restored site was not indicative of the Natural site (329 mm), chiefly due to limited surface Sphagnum moisture at the Restored site. After ten years following restoration, the large scale hydrological processes are still controlled by the cutover peat and not the regenerated Sphagnum moss; thus the Restored site is still divergent from the Natural site. Wells paired with the soil moisture measurements resulted in average water tables of -53.7 ± 17.8 cm at the Restored site and -31.9 ± 8.3 cm at the Natural site. In addition to much lower water tables, the upper layers of regenerated Sphagnum (θ2.5 cm – 0.12 and θ7.5 cm – 0.11) on average were far drier than the same species at the Natural site (θ2.5 cm – 0.23 and θ7.5 cm – 0.32) under only Sphagnum. Furthermore the Restored site was very dry just above the cutover peat (θ17.5 cm – 0.19), compared to the same probe depth at the Natural site (0.57). At the Natural site under ericaceous and Sphagnum the soil moisture contents were generally double that of the Sphagnum-only site. In addition to poor soil water retention at the Restored site, high specific yield was observed in the Restored site (0.44) monoliths while the water table fluctuated within the Sphagnum compared to both the Natural (0.10) and Unrestored (0.05) monoliths. These retention characteristics at the Restored site are due to far lower fraction of water filled pores for a given pore diameter than the same species (S. rubellum) at the Natural site. The high abundance of large pores do not generate the necessary capillary force to draw water from the relatively wet cutover peat into the Sphagnum moss, resulting in a capillary barrier. Although after ten years the Restored section of Bois-des-Bel had somewhat representative bog peatland ecology, the hydrological conditions needed for net carbon sequestration were not present. The lack of water transmission from the cutover peat to the regenerated Sphagnum moss due to large pores and the inability of the Sphagnum moss to retain water are both retarding the restoration. For Bois-des-Bel to become a net carbon sequestering further lateral infilling of the Sphagnum leaves and branches along with decomposition of the basal layer will be need. In addition to these two processes, planting of ericaceous shrubs could lower the water loss through evaporation, thus increasing the capitula moisture content and creating healthier mosses. If Bois-des-Bel continues on its current ecohydrological trajectory it is likely that it will self-regulate and make the necessary structural changes to become a net carbon sequestering system.

Vacuum harvested peatlands typically do not spontaneously regenerate peatland species and more importantly the peat-forming Sphagnum mosses. Thus harvested and abandoned peatlands require restoration to return the peat-forming Sphagnum moss to the ecosystem. Restoration can create a hydrological environment that is suitable for peatland species’ regeneration and results in substantial Sphagnum moss growth. Bois-des-Bel was restored in the winter of 1999 and studied in the following three years (2000-2002), then again after 10 years (this study). Immediately following restoration the conditions were deemed favourable for Sphagnum regeneration (i.e. soil water pressures and water tables, > -100 cm and -40 cm respectively) (~ 15-20 cm in 10 years), while evaporation from the surface was reduced due to the straw mulch that was applied as part of the restoration measures. Although the hydrological conditions were suitable for peat revegetation, Bois-des-Bel was still a net exporter of carbon during first three years. The purpose of this thesis is to understand the hydrological evolution of Bois-des-Bel since the initial assessments and document the hydrophysical properties that could limit net carbon sequestration. This is done with a combination of field and laboratory (monolith) experiments through comparison of its hydrology and hydraulic parameters to that of a natural reference site. Since the initial assessment a water table rise of ~ 5-10 cm has occurred at the Restored site with an average water table of -27.3 (± 14.9) with respect to the cutover peat (pre-restoration surface) and ~ -42.3 (± 20.9) cm with respect to the regenerated Sphagnum surface. This water table is still much further from the capitula and more variable than at the Natural site (33.2 ± 9.0 cm). Both evapotranspiration (242 mm) and runoff (7 mm) from the Restored site maintained the same relationships in 2010 as during the initial assessments, compared to the Unrestored site (290mm and 37 mm, respectively). Although lower evapotranspiration equated to less water lost from the system, evapotranspiration at the Restored site was not indicative of the Natural site (329 mm), chiefly due to limited surface Sphagnum moisture at the Restored site. After ten years following restoration, the large scale hydrological processes are still controlled by the cutover peat and not the regenerated Sphagnum moss; thus the Restored site is still divergent from the Natural site. Wells paired with the soil moisture measurements resulted in average water tables of -53.7 ± 17.8 cm at the Restored site and -31.9 ± 8.3 cm at the Natural site. In addition to much lower water tables, the upper layers of regenerated Sphagnum (θ2.5 cm – 0.12 and θ7.5 cm – 0.11) on average were far drier than the same species at the Natural site (θ2.5 cm – 0.23 and θ7.5 cm – 0.32) under only Sphagnum. Furthermore the Restored site was very dry just above the cutover peat (θ17.5 cm – 0.19), compared to the same probe depth at the Natural site (0.57). At the Natural site under ericaceous and Sphagnum the soil moisture contents were generally double that of the Sphagnum-only site. In addition to poor soil water retention at the Restored site, high specific yield was observed in the Restored site (0.44) monoliths while the water table fluctuated within the Sphagnum compared to both the Natural (0.10) and Unrestored (0.05) monoliths. These retention characteristics at the Restored site are due to far lower fraction of water filled pores for a given pore diameter than the same species (S. rubellum) at the Natural site. The high abundance of large pores do not generate the necessary capillary force to draw water from the relatively wet cutover peat into the Sphagnum moss, resulting in a capillary barrier. Although after ten years the Restored section of Bois-des-Bel had somewhat representative bog peatland ecology, the hydrological conditions needed for net carbon sequestration were not present. The lack of water transmission from the cutover peat to the regenerated Sphagnum moss due to large pores and the inability of the Sphagnum moss to retain water are both retarding the restoration. For Bois-des-Bel to become a net carbon sequestering further lateral infilling of the Sphagnum leaves and branches along with decomposition of the basal layer will be need. In addition to these two processes, planting of ericaceous shrubs could lower the water loss through evaporation, thus increasing the capitula moisture content and creating healthier mosses. If Bois-des-Bel continues on its current ecohydrological trajectory it is likely that it will self-regulate and make the necessary structural changes to become a net carbon sequestering system.

Peatlands are multiservice ecosystems: they are the largest terrestrial store of carbon in the UK, unique habitats which provide a home for internationally important species and managed for forestry, farming and game management and shooting. This makes understanding the impact of management practices on their ecology important if they are to be sustainably managed for multi-benefits. Fire has long been used to manage peatlands in the UK to improve grazing and habitat provision for livestock and game. The effect of fire on carbon cycling in blanket bogs is of increasing concern as greenhouse gas emissions from land use is now an important management as well as political issue. Gaps however, still exist in our understanding of the controls on greenhouse emissions from blanket bogs and the impact fire may have on them both directly and indirectly by modifying vegetation composition and environmental conditions. The main objective of this research was to assess the effect of fire on greenhouse gas emissions by measuring methane and ecosystem respiration after burning at blanket bog sites across Scotland for a period of up to 3 years and relating changes in fluxes with changes in vegetation composition and abiotic conditions. In addition, the response of the Sphagnum layer to burning was assessed by looking at the recovery of Sphagnum capillifolium in the field and in a novel laboratory experiment. The indirect effects of fire on methane emissions were further investigated by a laboratory experiment devised to test if high temperatures would be fatal to methanotrophic bacteria in the Sphagnum layer, reducing methanotrophy, and thus a mechanism for fire to increase methane emissions in the short term. The results showed that methane emissions and ecosystem respiration were not significantly different in burnt plots when compared to adjacent unburnt plots at each of the three sites studies. Methane emissions were only weakly correlated to the position of the water table and neither methane fluxes or ecosystem respiration correlated with measures of vegetation composition and above ground biomass. Methanotrophy in Sphagnum was found to be difficult to detect, with a high temperature treatment having no significant effect on rates of methane oxidation. S. capillifolium was found to respond to fire by growing new auxiliary stems if the capitulum was consumed or irreversible damaged physiologically by temperatures experienced at the moss surface, with surface temperatures around 400oC with a temperature residency time of 30 seconds on artificially dried samples the most damaging, but not lethal, treatment. These results suggest that low severity fires which only consume the canopy vegetation, not penetrating the peat and leaving the moss layer mostly intact, do not have significant effects on methane emissions and ecosystem respiration in the short and medium term. In addition, it suggests that S.capillifolium can, under certain circumstances, survive a fire with the characteristics of those studied here. These findings reiterate that best practice burning guidelines must continue to ensure that burning is only carried out on blanket bog when conditions are conducive to fires with the characteristics studied here, which had little effect on important components of the carbon cycle and are survivable by at least one of the most common species of Sphagnum.

Artificial drainage networks established throughout peatlands during the peat extraction process often remain active following abandonment, maintaining a water table relatively far from the surface of the peat and hindering the survival and reestablishment of Sphagnum mosses. Since cutover peatlands are characterized by low (negative) soil water pressures, sufficient internal water storage and balanced water fluxes are critical for the physiological function of spontaneously regenerated Sphagnum mosses. The relative importance of water exchanges between spontaneously regenerated Sphagnum moss cushions and their surroundings are addressed through investigation of the sensitivity of moss moisture dynamics to a range of environmental variables. Precipitation waters are poorly retained within the cushions, which indicated that rain event water can only be relied upon by the mosses for a short period of time. An imbalance between water inputs and losses from moss cushions identified that additional (small) sources of water, such as dewfall and distillation, are potentially important for physiological processes under dry conditions, common in disturbed peatland ecosystems. As an initial restoration effort, rewetting of the peatland by blocking drainage ditches consequently reduced the runoff efficiency and caused the site-average water table to rise by 32 cm. Higher water tables and a blocked drainage network created conditions more favourable for Sphagnum survival through increasing the moisture content and soil-water pressures within the remnant peat deposit. The hydrologic connectivity between moss cushions and the remnant peat was strong when conditions were wet and the water table was within 30 cm of the surface of the cutover peat but weakened as conditions became drier, as reflected by weakened upward hydraulic gradients in the unsaturated zone below the moss cushions. Runoff variability increased following rewetting, and displayed a greater dependence upon antecedent conditions (capacity to retain additional water on-site) and event-based precipitation dynamics. Evapotranspiration rates were 25% higher following rewetting (3.6 mm day-1) compared to pre-restoration ET rates of 2.7 mm day-1. Total storage changes were restricted following rewetting, as a factor of the reduced runoff losses limiting water table drawdown, thereby constraining peat compression and preventing undue drying of the unsaturated zone. Changes to the system hydrology following rewetting of the peatland by blocking drainage ditches created conditions more favourable for Sphagnum survival through increasing the moisture content and soil-water pressures within the remnant peat deposit; although restoration efforts should aim to constrain water table fluctuations to within the upper 30 cm.

Artificial drainage networks established throughout peatlands during the peat extraction process often remain active following abandonment, maintaining a water table relatively far from the surface of the peat and hindering the survival and reestablishment of Sphagnum mosses. Since cutover peatlands are characterized by low (negative) soil water pressures, sufficient internal water storage and balanced water fluxes are critical for the physiological function of spontaneously regenerated Sphagnum mosses. The relative importance of water exchanges between spontaneously regenerated Sphagnum moss cushions and their surroundings are addressed through investigation of the sensitivity of moss moisture dynamics to a range of environmental variables. Precipitation waters are poorly retained within the cushions, which indicated that rain event water can only be relied upon by the mosses for a short period of time. An imbalance between water inputs and losses from moss cushions identified that additional (small) sources of water, such as dewfall and distillation, are potentially important for physiological processes under dry conditions, common in disturbed peatland ecosystems. As an initial restoration effort, rewetting of the peatland by blocking drainage ditches consequently reduced the runoff efficiency and caused the site-average water table to rise by 32 cm. Higher water tables and a blocked drainage network created conditions more favourable for Sphagnum survival through increasing the moisture content and soil-water pressures within the remnant peat deposit. The hydrologic connectivity between moss cushions and the remnant peat was strong when conditions were wet and the water table was within 30 cm of the surface of the cutover peat but weakened as conditions became drier, as reflected by weakened upward hydraulic gradients in the unsaturated zone below the moss cushions. Runoff variability increased following rewetting, and displayed a greater dependence upon antecedent conditions (capacity to retain additional water on-site) and event-based precipitation dynamics. Evapotranspiration rates were 25% higher following rewetting (3.6 mm day-1) compared to pre-restoration ET rates of 2.7 mm day-1. Total storage changes were restricted following rewetting, as a factor of the reduced runoff losses limiting water table drawdown, thereby constraining peat compression and preventing undue drying of the unsaturated zone. Changes to the system hydrology following rewetting of the peatland by blocking drainage ditches created conditions more favourable for Sphagnum survival through increasing the moisture content and soil-water pressures within the remnant peat deposit; although restoration efforts should aim to constrain water table fluctuations to within the upper 30 cm.

The boreal peatlands that cover much of western Canada are immense reservoirs of organic carbon and nitrogen, serving as sinks for atmospheric carbon, as well as providing habitat for flora and fauna, and nutrient cycling. These ecosystems are generally believed to be nitrogen limited. Due to regional increases in industrial activities associated in the Athabasca Oil Sands Region (AOSR), atmospheric deposition of nitrogen is projected to increase, with unknown effects on peatland functioning. The results of this study provide baseline data for a nitrogen fertilization experiment with an accurate site description of the entire peatland complex to provide reference for the experiment. This study also examines patterns in production and nitrogen usage along a wet to dry gradient. My main question was if species assemblages could be sorted into communities and how these were related to environmental gradients. In chapters three and four I asked how production and nitrogen usage and storage varied along a moisture gradient. In chapter two, four communities were identified as being independent with clear indicator species. These communities had differences in abiotic factors formed clear gradients across the peatland, influencing the distribution of species arrangements in the peatland complex. Sphagnum angustifolium thrived in all four communities and across the entire range of gradients. This species is a foundation of species of bogs and poor fens and was studied in more detail in chapters 3 and 4. In chapter three, I found that primary production of S. angustifolium increased from dry to wet along the moisture gradient. Cranked wires used to measure linear growth became less reliable in wetter habitats, missing over 50 % of growth measure by innate time markers. Capitula increased in biomass throughout the course of the growing season, suggesting that after vertical elongation, S. angustifolium begins to accumulate branches and leaves in the capitula to close the growing season. Chapter four, evaluating nitrogen requirements found that while primary production of S. angustifolium increased from dry to wet, tissue quality of the growth decreased along this gradient. Despite the lower tissue quality, wet habitats had higher nitrogen requirements to support growth rates. Inputs of atmospheric deposition fulfilled <5% of annual N requirements and nitrogen saturated capitula in the beginning of the season was found to be an important source of nitrogen for growth, as capitula nitrogen storage declined over the season. Of the total nitrogen assimilated into annual growth, the percent lost a year later was similar across the moisture gradient; more nitrogen is stored in the wet habitats, strictly due to higher amounts initially assimilated. The results of this study suggest that in drier peatland habitats, there is an insufficient supply of water to deliver nitrogen and to support continuous growth during the growing season. Consequently, in wetter habitats, production is limited by nitrogen while in drier habitats it is limited by climate.

Increased nitrogen (N) deposition onto boreal peatlands and forests is anticipated with further expansion of Alberta's oil sands industry and consequently, an increase in sources of nitrogen oxide emissions. Increased N deposition has the potential to affect peatland flora and alter N cycling patterns in peatlands, therefore it is imperative to investigate at what level of excess N deposition these effects take place. This thesis discusses results from the first two years of a five year N fertilization study being conducted at a peatland complex near the hamlet of Mariana Lake in northeastern Alberta, Canada aimed at quantifying the N "critical load" for these peatland ecosystems. At the study site there are forty-two experimental plots - half in an ombrotrophic bog, the other half in the poor fen - with varying N fertilization treatments ranging from 0 kg/ha/year to 25 kg/ha/year. To investigate nitrogen uptake by plants at the Mariana Lake study site, I measured nitrogen (N) and carbon (C) concentrations of Sphagnum capitulum tissue and vascular plant foliar tissue. For Sphagnum species, I also analyzed C:N ratios and capitulum N storage. To investigate potential growth response of the target Sphagnum species, measurements were taken for linear growth (the vertical elongation of the Sphagnum shoots), stem mass density (the weight of Sphagnum stems occupying a volume after capitula were removed), and ultimately, net primary production (the product of the prior two measurements). Capitulum mass density (biomass) was measured as well to investigate possible changes in Sphagnum capitulum growth. Also, during the height of the growing season (mid-July, 2011 and 2012), the plant communities in each treatment plot were sampled to provide "baseline" data necessary for documenting any shifts in plant distribution or community composition that may occur after N additions.