Thesis (M. Sc.)--Université Laval, 2002. / "Fevrier 2002." Includes bibliographical references. Downloaded and printed from Laval University website.

A peatland near Lake Charlotte, Nova Scotia that had been damaged by all-terrain vehicles (ATVs) was identified as a compensatory mitigation site. Restoration practices commonly used for harvested peatlands were applied to small sections of ATV damaged peatland. In the test plots, treatments of moss and shrub transplantation, fertilizer application, and straw mulch addition were applied in various combinations to determine the optimum restoration approach for specific areas within the Lake Charlotte peatland complex. The overall objective of this research was to recommend a procedure for the complete restoration of the damaged portions of the peatland. A number of different hydrological, physio-chemical and biological parameters were monitored throughout the 2009 growing season to evaluate the effectiveness of the different treatments. In conclusion, this study demonstrated that techniques developed to restore peatlands degraded by peat extraction activities are also effective for restoring peatlands impacted by ATV use.

Pollen assemblages, peat humification and carbon:nitrogen stratigraphy were examined at high resolution in a core from a fen peatland in the Hudson Bay Lowlands, Northern Ontario, to interpret the factors that drive long-term peatland dynamics. Subtle changes in the vegetation community are evident over the record, suggesting both allogenic and autogenic influences, but a fen community appears to have been resilient to external perturbations including isostatic rebound and hydroclimatic changes between 6400 and 100 years BP. Paleoclimatic reconstructions from the fossil pollen assemblages indicate that precipitation increased 3000 years BP at the end of the Holocene Thermal Maximum, and that carbon accumulation in the fen was controlled more by effective surface moisture (precipitation) than by temperature. The pollen record suggests changes over the past century, including increases in shrub Betula, Alnus, Ambrosia, and Cyperaceae and a decrease in Sphagnum spores, consistent with the observed Pan-Arctic shrub increase.

Pollen assemblages, peat humification and carbon:nitrogen stratigraphy were examined at high resolution in a core from a fen peatland in the Hudson Bay Lowlands, Northern Ontario, to interpret the factors that drive long-term peatland dynamics. Subtle changes in the vegetation community are evident over the record, suggesting both allogenic and autogenic influences, but a fen community appears to have been resilient to external perturbations including isostatic rebound and hydroclimatic changes between 6400 and 100 years BP. Paleoclimatic reconstructions from the fossil pollen assemblages indicate that precipitation increased 3000 years BP at the end of the Holocene Thermal Maximum, and that carbon accumulation in the fen was controlled more by effective surface moisture (precipitation) than by temperature. The pollen record suggests changes over the past century, including increases in shrub Betula, Alnus, Ambrosia, and Cyperaceae and a decrease in Sphagnum spores, consistent with the observed Pan-Arctic shrub increase.

No description available.

In this thesis, I establish and explore the role of phenology in understanding the rapidly changing environment of a subarctic peatland. First, I demonstrate how digital repeat photography can be used to characterize and differentiate distinct plant communities using two years of images. Each habitat is composed of different plant functional groups, promoting the individualistic approach to characterization that near-earth remote sensing tools can provide. The camera-product Relative Greenness successfully characterized interannual variability in seasonal growth for each habitat type. Across habitats, there was a direct relationship between advancement of spring onset and active season growth though this overall pattern showed habitat-specific variance. The camera images were also useful in characterizing the flowering phenology of an ​eriophorum​-rich fen habitat, for which a metric named Intensity was created. These results suggest that employment of phenology cameras in highly heterogeneous subarctic environments is a robust method to characterize phenology on a habitat to species scale. Next, I explored the role that this phenology product has in modeling Net Ecosystem Exchange (NEE) also measured at the field site. I hypothesized that the explanatory power of the phenology index, which is conceptually tied to a measure of photosynthetic capacity, would be tightly linked to the timescale it was used for: At sub-daily timescales, environmental forces would dominate, though when averaged over days to weekly scales, the biology represented through the camera index would be more influential. I show that at multiple time scales the environmental factors outperform the camera index when modeling NEE. Together, these studies begin to explore the applicability of phenology camera systems in subarctic environments.

A variety of approaches, spanning a range of spatial and temporal scales, were applied to the investigation of the effects of low dose SO₄^2- deposition, at rates comparable to those experienced in acid rain impacted areas, on methane (CH₄) emissions from natural wetlands. Over two years of experimental manipulation of SO₄^2- deposition to a peatland in northeast Scotland, CH₄ emissions were suppressed by around 40%. There was no significant difference in suppression of CH₄ flux within the sol- deposition range of 25-100 kg-S ha^-1yr^-1. In a similar short-term controlled environment SO₄^2- manipulation experiment, the suppressive effect of SO₄^2- was found to be independent of the simulated SO₄^2- deposition rate within a range of 15-100 kg-S ha^-1yr^-1. The possibility that suppression of CH₄ fluxes may have been the result of a 'salt effect' was ruled out. Both temperature and water table controlled the extent of CH₄ flux suppression in acid rain impacted wetlands. Sulfate reduction potential in SO₄^2- treatments were found to be 10 times larger than in control plots, suggesting that long-term suppression of CH₄ fluxes is the result of the formation of an enlarged population of competitively superior sulfate reducing bacteria. SO₄^2- concentrations were smaller in peat pore water from SO₄^2- treatments than from controls. This is possibly the result of a stimulated SO₄^2- reducing community scavenging available SO₄^2-, thereby decreasing concentrations to below ambient levels. In northern peatlands (>50°) the effect of SO₄^2- deposition at 1990 rates may have been sufficient to reduce emissions from these systems by around 15% annually. Globally, the effect of acid rain SO₄^2- deposition may be sufficient to reduce CH₄ emissions by as much as 22-28 Tg by 2030, which places this interaction within the same size category as many other components of the global CH₄ budget that have received far greater attention.

Hydrology, particularly the water table position below the surface, is an mportant control on biogeochemical and ecological processes in peatlands. The position of the water table is a function of total storage changes, drainable porosity and peatland surface oscillation (PSO). Because the absolute level of the peat surface (ASL) oscillates in a peatland, we can assign two different water table positions: the water table depth below the surface (relative water level, RWL) and the water table position above an absolute elevation datum eg. sea level (absolute water level, AWL). A review of 37 studies that report peatland surface oscillation indicate awide range (0.4-55 cm), which is to the same order as (or one order smaller than) water storage changes and RWL fluctuations. PSO can vary substantially across a single peatland and through time. A set of mechanisms (flotation, compression/shrinkage, gas volume changes and freezing) is hypothesised to cause ASL changes. The potential of PSO to reduce RWL fluctuations trended (mean in %) floating peatlands (63) greater than bogs (21), fens (18) greater than disturbed peatlands (10) with respect to peatland types. To investigate the spatiotemporal variability of peatland surface oscillation, AWL and ASL were monitored continuously over a one-year period (one site) and monthly (23 sites) in a warm-temperate peatland that is dominated by Empodisma minus (Restionaceae). A new measurement method was developed by pairing two water level transducers, one attached to a stable benchmark (AWL) and one attached to the peat surface (RWL). From August 2005 until August 2006 the ASL oscillated at one site through a range of 22 cm following AWL fluctuations (in total 47 cm). Consequently, RWL fluctuations were reduced on average to 53% of AWL fluctuations. The strong AWL-ASL relationship was linear for 15 sites with manual measurements. However, eight sites showed significantly higher rates of peatland surface oscillation during the wet season (ie. high AWLs) and thus a non-linear behaviour. Temporary flotation of upper peat layers during the wet season may have caused this non-linear behaviour. On the peatland scale AWL fluctuations (mean 40 cm among sites) were reduced by 30-50% by PSO except for three sites with shallow and dense peat at the peatland margin (7-11%). The reduction of RWL fluctuation was high compared to literature values. The spatial variability of PSO seemed to match well with vegetation patterns rather than peat thickness or bulk density. Sites with large PSO showed high cover of Empodisma minus. Surface level changes exhibited surprisingly hysteretic behaviour subsequent to raised AWLs, when the rise of ASL was delayed. This delay reversed the positive ASL-AWL relationship because the surface slowly rose even though AWL started receding. Hysteresis was more pronounced during the dry season than during the wet season. The observed hysteresis can be sufficiently simulated by a simplistic model incorporating delayed ASL fluctuations. PSO has wide implications for peatland hydrology by reducing RWL fluctuations, which feed back to peat decomposition and plant cover and potentially to (drainable) porosity. Stable RWL also reduce the probability of surface run-off. It is further argued that the gas content of the roots of plants, particularly Empodisma minus, added enough buoyancy to detach the uppermost peat layers resulting in flotation.

Bogs and fens, which comprise > 90% of the landscape near the De Beers Victor diamond mine, 90 km west of Attawapiskat, ON, provide different hydrological functions in connecting water flow pathways to the regional drainage network. It is essential to define their distribution, area and arrangement to understand the impact of mine dewatering, which is expected to increase groundwater recharge. Classification was achieved by developing a technique that uses IKONOS satellite imagery coupled with LiDAR-derived DEM derivatives to identify peatland classes. A supervised maximum likelihood classification was performed on the 1 m resolution IKONOS Red/Green/Blue without the infrared (RGB) and with the infrared (IR_RGB) band to determine the overall accuracy prior to inclusion of the DEM derivatives. Confusion matrices indicated 62.9% and 65.8% overall accuracy for the RGB and IR_RGB, respectively. Terrain derivatives were computed from the DEM including slope, vertical distance to channel network (VDCN), deviation from mean elevation (DME), percentile (PER) and difference from mean elevation (DiME). These derivatives were computed at a local (15-cell grid size) and meso (250-cell grid size) scale to capture terrain morphology. The mesoscale 250-cell grid analysis produced the most accurate classifications for all derivatives. However, spectral confusion still occurred (regardless of scale) most frequently in the Fen Dense Conifer vs. Bog Dense Conifer classes and also in the Bog Lichen vs. Bog Lichen Conifer. Despite this confusion, by combining the larger scale LiDAR DEM derivatives and the IKONOS imagery it was found that the overall classification accuracy could be improved by 13%. Specifically, the DiME derivative combined with the multispectral IKONOS (IR_RGB) produced an overall accuracy of 76.5%, and increased to 83.7% when Bog Lichen and Bog Lichen Conifer were combined during a post hoc analysis. This classification revealed the landscape composition of the North Granny Creek subwatershed, which is divided into north and south. The north portion comprises 67.4% bog, 13.6% fen and 18.9% water class, while the south is 63.7% bog, 15.2% fen and 21.1% water class. These proportions provide insight into the hydrology of the landscape and are indicative of the storage and conveyance properties of the subwatershed based on the percentage of bog, fen, or open water.

Peatlands are one of the largest global terrestrial carbon (C) pools, and play a vital role in provision of key ecosystem functions and as refugia for biodiversity. Many peatlands continue to be exploited with lowland raised bogs among the most affected by human modification. It is also now recognised that global climate change has potential to cause further impacts to peatlands, and it is thought that northern peatlands are particularly vulnerable to changes in temperature and precipitation. In this thesis, I report from a series of experiments to test; 1) the effect drought on soil CO2 efflux and photosynthate allocation, and production and chemical composition of dissolved organic carbon in leachate, 2) the effects of ericoid mycorrhizal (ERM) fungal necromass on soil CO2 efflux, 3) whether nitrogen (N) from ERM fungal necromass is important for plant nutrition, and 4) how different species of ERM fungi affect C and N turnover. These experiments were undertaken using a combination of field manipulations and measurements, and establishment of simplified mesocosms and microcosm systems. My results show that soil CO2 efflux in lowland degraded peatland is driven by the depth of water table, and that management of these systems from a C cycling perspective should consider ways to stabilise water table depth. Interpretation of data from field-girdling of C. vulgaris plants and 13CO2 pulse labelling strongly suggested that recent plant photosynthate has little apparent effect on this flux in contrast to many other ecosystems. Although the biomass of ERM fungi is often assumed to have a minor role in C cycling, my data show that the necromass of these fungi is highly labile and turnover rapidly, with potential to make important contributions to CO2 efflux and other microbially-driven processes.