In the boreal forest of Alberta, oil exploration has brought roads into previously undisturbed areas. Peatlands cover vast areas of the boreal forest, transmit water across the landscape, provide habitat for wildlife, and store carbon sequestered from the atmosphere. Roads crossing peatlands is inevitable, and little is known about how roads impact plant communities, water chemistry, and water tables. Few studies of large fen complexes have been conducted in the continental boreal forest, nor have many investigated the impact of roads. Understanding the relationships between species, water chemistry, and microtopography provides insight into the nature of continental fens and how they respond to disturbance. I examined plant communities and water chemistry characteristics of an undisturbed fen and compared the data to nearby peatlands that were disturbed by mineral haul roads. This study determined the control study site was an acidic fen with a pH generally less than 4.0 and four community types were recognized. Most of the complex was very wet, open, oligotrophic poor fen, with a treed, oligotrophic, species poor area extending between two water tracks. As the fen narrowed following its drainage, site type changed to mesotrophic poor fen, with mesotrophic rich fen communities in some marginal areas. The water table was very stable. The road sites showed signs of enriched water chemistry and changed plant communities within 50 meters of the road upstream. Downstream plant communities were less effected. Water tables appear to be influenced both upstream and downstream differently.

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No description available.

Peatland ecosystems only cover 2-3 % of the Earth‟s surface but they represent significant carbon stores, holding approximately one third of the global soil carbon (C). The major peat forming genera Sphagnum appears to be highly sensitive to increased N availability. Many studies have shown decreased productivity of Sphagnum which could lead to a decrease in the amount of C stored, especially as many studies also show an increase in the decomposition rate with higher N deposition. However, the overall effects of N on CO2 fluxes of Sphagnum remain unclear. The present study aimed to look at the effects of increased N on Sphagnum productivity, decomposition and CO2 fluxes after long-term N additions (> 5 years) using a field experiment at Whim Moss in southern Scotland where N deposition has been manipulated employing a very realistic application coupled to rainfall since 2002. The experiment also has treatments with PK addition to test the effects of removing P and/or K-limitation. Measurements of plant tissue nutrient concentrations, visual assessments of Sphagnum viability, and pore water analysis were also carried out. Nitrogen additions increased tissue N, and decreased Sphagnum shoot extension and productivity. Simultaneous P and K additions alleviated the effects of N on tissue N concentrations and growth, although this was only significant for shoot extension. Visual assessments correlated well with tissue chemistry and productivity; the decline in health was associated with high %N and reduced productivity. Interestingly, in the present study increased N decreased the mass loss and again when PK was added with N decomposition rates were more similar to the control. With respect to the carbon balance of the site and the sustainability of peatlands the results suggest that the negative effect of N on C assimilation may be partially offset by the reduced decomposition rates. The CO2 measurements showed a large loss of C as CO2 from all the Sphagnum plots which was exacerbated by adding N especially when the air temperature increased. The positive temperature response of ecosystem respiration with N additions suggests that in high N deposition areas climate change and subsequent temperature rises will increase C losses from bogs.

The relationship between vegetation change and rehabilitation management is investigated at a severely degraded cut-over lowland raised mire on the Wales/England border, managed by Natural England and The Countryside Council for Wales. Positive responses are confirmed 11 years after rehabilitation commenced, identifying trends towards raised mire as well as bog pool vegetation and water table thresholds associated with these trends have been established. A landscape-scale vegetation survey was carried out three times over 9 years. Species abundance was correlated with average seasonal water table height, time since rehabilitation, cutting type and survey year. Key species maps for the time series confirmed positive vegetation response, but slower than stipulated in the site management plan. There was a clear increase in the target peat-forming species (Sphagnum cuspidatum, Eriophorum angustifolium and E. vaginatum) as a direct response to rehabilitation and correlating positively with a high water table. Permanent quadrat vegetation monitoring was carried out three times at five-year intervals. Uncut areas and areas of recent commercial cuttings were rehabilitated earliest having significant increases in target mire species without the loss of other mire species from excess inundation. In the recent commercial cutting areas, a successional trend was identified, from a low water table to a fluctuating water table characterised by Molinia caerulea-rich vegetation, followed by a transition to stable, inundated conditions supporting Sphagnum cuspidatum/Eriophorum spp pool vegetation. A second successional trend, associated with the achievement of a near-surface, stable water table, saw the development of raised mire vegetation including Sphagna other than S. cuspidatum. This latter trend was primarily found in the uncut areas of the site but was also found to a lesser extent in recently cut-over areas where it was preceded by a fluctuating water table with a Calluna vulgaris- Molinia caerulea vegetation. A new survey related water table residence time calculated from hydrology data with vegetation for each quadrat. Analysis identified a mire pool vegetation type correlated with shallow, above surface flooding. A diverse mire vegetation type was also found which correlated with the water table staying within the upper 10cm of peat. The minimum threshold for establishment of Sphagnum species was found to be an average water table level within the range of 5.1 to 10cm below the peat surface. Higher cover of Sphagnum species was related to shallow flooding – suggesting that these conditions would be most efficient in re-establishing mire vegetation. 3 A base-line vegetation monitoring survey on an area immediately following deforestation and damming identified a subtle but positive response of the mire vegetation to management within one year.

Western boreal peatlands have diverse ground covers of Sphagnum and brown mosses that have important hydrological controls on peatland-atmosphere interactions. Since peatland mosses are non-vascular, their shoot structural morphologies and community growth forms affect the storage and fluxes of water that are critical for maintaining productivity and evaporative functions. While many of the mechanisms of capillary rise are fairly well understood for Sphagnum mosses, there is less information on the water dynamics in communities of Tomenthypnum nitens, a dominant brown moss species in northern rich fens. This study investigated how the different hydrophysical characteristics of moss and peat profiles of T. nitens from a rich fen and intermixed Sphagnum angustifolium and Sphagnum magellanicum, from a poor fen affect capillary flow and water retention to support evaporation and productivity; and how different groundwater and atmospheric sources of water affected these processes. Laboratory investigations indicated volumetric water content and gross ecosystem productivity decrease with water table depth for both mosses without the advent of precipitation, with Sphagnum capitula retaining 10-20% more water than T. nitens due to its moss structure and pore connectivity with the water table. Consequently, Sphagnum capillary rise was sufficient to sustain both high pore-water pressures for evaporation and high water content for productivity at all water table depths due to a gradual shift in average water-retaining pore sizes with depth. The structure of T. nitens moss turfs, consisting of live shoots and a basal layer of old, partially decomposed shoots sometimes overlying well-decomposed peat makes capillary rise more difficult, requiring extremely low matric pressures at the surface, sometimes causing desiccation of the uppermost portions of moss shoots, and hence reduced productivity. Additional nocturnal sources of atmospheric water from dew, distillation, and vapour fluxes provide small, but potentially critical sources of water to rewet desiccated moss shoots for early morning productivity for both T. nitens and Sphagnum mosses. Investigations in the field, however, indicated that with frequent precipitation to rewet the moss and the turf base to refill large pores, evaporative demands at the T. nitens moss canopy could drive capillary flow from the water table to maintain adequate θ for productivity. T. nitens mosses also can grow in turfs disconnected from the underlying iii peat, so that the basal layer temporarily retains water from precipitation for capillary rise. Thus, while capillary connection of the T. nitens moss turf with the underlying peat and water table is not critical to maintain productivity, it grows in a relatively large range of elevations from the water table, compared to Sphagnum and feather mosses. Rewetting of the capitula and the raising of the water table by precipitation provided higher water matric pressures within the moss matrix, and along with high evaporative demands, provided the mechanisms for sufficient capillary flow for productivity. Thus, Sphagnum could grow in habitats far from the water table like feather mosses, although the latter did not require capillary rise for productivity. Furthermore, disequilibrium between water vapour and liquid in the pores of T. nitens in the near-surface suggested pressures calculated with the Kelvin equation may not provide an accurate characterization of actual matric pressures in the moss. However, as the disequilibrium is caused by vapour pressure gradients between the moss and the atmosphere, it is likely a driving factor that helps maintain vapour and capillary water fluxes to provide moisture for T. nitens and other mosses. These results illustrate hydrological mechanisms that explain how moss growth form and habitat are linked. As such, the Sphagnum and T. nitens mosses are well adapted to maintain capillary in their poorly drained habitats in western boreal peatlands.

The placenta of two Sphagnum species was examined by electron microscopy. In contrast to all mosses so far investigated, neither sporophyte nor gametophyte placental cells of Sphagnum develop wall ingrowths. The sporophyte cells are highly vacuolate and the gametophyte cells close to them degenerate to produce a system of spaces filled with mucilage. Whether this type of placenta represents a primitive or derived condition in mosses is discussed.

This study examined the usefulness of remote sensing to monitor peatlands, and more specifically Sphagnum moss ‘health’. Results from this study show that thermal imaging can be used to monitor Sphagnum productivity, as when the surface temperature of Sphagnum exceeds a threshold value (30.8 °C in the field and 18.2 °C in the laboratory), Sphagnum quickly changes from being productive to being unproductive. The Enhanced Normalized Difference Vegetation Index (ENDVI) can also be used in a similar manner, where if the ENDVI value is high (above 0.11 in the field and -0.12 in the laboratory), Sphagnum will be productive, and otherwise, it will be stressed. A classification scheme was developed to monitor peatland recovery to fire disturbance. By utilizing the ENDVI, leaf area index and aboveground biomass within a recovering peatland can be mapped, as well as the recovery trajectory of the groundcover. The findings of this study highlight the potential use of remote sensing to assess the driving factors of Sphagnum moss stress, as well as quickly and expansively aid in peatland recovery trajectory. / Thesis / Master of Science (MSc)

<p>Disturbed peatlands may undergo a dramatic alteration in ecohydrological conditions, potentially limiting the recolonisation of peat-forming species like <em>Sphagnum</em>. A poor fen was experimentally drained in 1984, both the drained and undrained portion of the peatland burned in 2001, providing an unique opportunity to examine the ecohydrological response to ‘double disturbance’.</p> <p>The undrained site<em> </em>was characterized by a healthy recovery of<em> </em>peatland microform <em>Sphagnum</em> species, low soil water pressure (Ψ), high volumetric soil moisture (θ) content and high and stable water table position. However, the drained site showed no recolonization of <em>Sphagnum</em> with <em>Brome</em> grasses representing the dominant surface cover nine years post-wildfire.</p> <p>While the study period was generally wet and as such Ψ did not exceed thresholds limiting <em>Sphagnum</em> growth (≥ -100 mb) during the study period, a series of ecohydrological influences were found to be operating, limiting <em>Sphagnum</em> recolonisation at the drained site. The physical peat structure following drainage and wildfire has been considerably altered, changing the moisture retention and water storage properties of the peat, largely through substantive increases in bulk density (ρ_b). Moreover, specific yield (<em>Sy</em>) has also decreased the drained peat having become more humified, increasing unstable water table fluctuations. As such, this has lowered the resilience to drought. Only smaller decreases in θ are required to reach Ψ ≥ -100 mb at the drained and impose ecophysiological stress on <em>Sphagnum</em> growth. Dense canopy cover (<em>Betula</em> and <em>Sali</em>x) has limited available radiation at the surface to recolonisation, shading out the surface, further limiting <em>Sphagnum</em> recolonisation.</p> / Master of Science (MSc)

<p>The objective of this thesis is to examine the changes to peatland ecohydrological processes as a result of wildfire disturbance in forested ombrotrophic peatlands of the Boreal Plains. The hydrology and atmospheric exchanges of energy and water were examined at two peatlands in northern Alberta: one recently burned and the other approximately 75 years since fire.</p> <p>Wildfire resulted in little change in net radiation flux to the peatland during the snow-free period. A decrease in the net radiation flux during the late winter was caused by the loss of the tree canopy and the increase in albedo during winter. While summer albedo largely returned to pre-fire values within two years after fire, the amount of solar radiation reaching the burned peat surface increased by nearly 50%. As a result, surface evaporation increased by an amount only marginally greater than the loss of transpiration. The net result on the water balance was a modest increase in water losses during the course of the summer, resulting in a lower water table. Water table decline per unit of evaporation was higher due to a decrease in specific yield, likely from a combination of post-fire peat compression and the combustion of high specific yield surface peat during wildfire. The combination of lower water table and enhanced evaporation cause greater pore-water pressures after fire, particularly in hummocks. The hydrological regime of hollows was not significantly altered by wildfire, despite the larger depth of burn in the hollows.</p> / Doctor of Philosophy (PhD)