Research for a dissolved nitrogen budget was conducted at Mer Bleue bog near Ottawa, ON, from May 20, 2003 to May 21, 2004. Mer Bleue is located within an area experiencing the highest levels of atmospheric nitrogen deposition in North America, although these levels are only low to moderate compared to those in Europe. Continuous measurements of precipitation, evapotranspiration, bog water table level and outflow water depth were used in conjunction with discrete measurements of precipitation and outflow to determine the hydrologic budget. Water samples were taken from precipitation collectors, piezometers at various depths and locations throughout the bog, and an outflow point in order to gauge changes and patterns in chemical concentrations at various points throughout the bog. The nature of the bog morphology and landscape allowed for collection of water samples from a single outflow point. / Chemical analysis combined with the water budget revealed that the majority of the dissolved nitrogen is entering the bog as NO3-N and NH 4-N (inorganic nitrogen), and leaving the bog as dissolved organic nitrogen (DON). Export of nitrogen was generally low relative to the input, and was only a very small fraction of the huge amount of nitrogen stored in the bog. Bog porewater concentrations were dominated by DON and did not show spatial patterns in relation to the bog edge. When comparing the annual accretion of nitrogen at the bog to the long-term storage numbers, it was apparent that there is a missing source of nitrogen. From the literature and patterns in the bog, it appears that this missing input at Mer Bleue is likely due to a combination of previously unmeasured nitrogen fixation and more diverse usage of DON by bog vegetation.

To further the understanding of respiration processes of northern peatlands, the relative importance of each type of belowground respiration was determined at Mer Bleue, a northern peatland located near Ottawa, Ontario, from June to November, 2003. Direct measurements of total, soil organic matter (SOM) and root respiration were made, with rhizosphere respiration determined by residual. Although an aboveground source, determination of live Sphagnum respiration was also attempted in the field. To identify changes in CO2 fluxes with environmental conditions, peat temperature and water table levels were monitored throughout the study period. / SOM respiration was higher than hypothesized at 63% while root and rhizosphere respiration were lower than hypothesized at 21% and 16%, respectively, of total belowground respiration. As the field experiment for determining live Sphagnum respiration was unsuccessful, it was determined by calculation to be 18% of total respiration, slightly higher than hypothesized. Opposite of hypothesized, air temperatures, peat temperatures and water table levels generally had weak and insignificant relationships when linearly regressed with total respiration.

Rates of carbon and peat accumulation were studied in a series of peat landforms within discontinuously frozen peatlands near Fort Simpson, Northwest Territories. An extended distribution of the White River volcanic ash layer was used as a chronostratigraphic horizon to ensure a consistent time span of peat deposition among peat cores and to allow a large core sample size without the expense of radiocarbon dating. Apparent recent carbon accumulation rates measured over the past 1200 years were not significantly different among rich fen, peat plateau, and collapse fen (means 13--14 g C M-2 yr-1). Poor fen and bog mean accumulation rates were 20--22 g C M-2 yr -1 and were not significantly different from each other. Microtopography and water table position appear to be important controls on both carbon and vertical peat accumulation rates. A regional survey incorporating measurements from other parts of the southwestern Northwest Territories and the southeastern Yukon shows rates similar to those near Fort Simpson. / The aggradation of permafrost results in 50 and 65% decreases in carbon and vertical peat accumulation rates, respectively. Carbon and peat accumulation continue to decrease significantly with both increasing permafrost maturity and the number of ground fires. The internal degradation of permafrost results in nearly a doubling in carbon accumulation rates, yet permafrost degradation at the margins of a peat plateau results in carbon accumulation rates similar to the peat plateau. / Clymo's (1984) carbon accumulation model was applied to cores from each landform in addition to a core spanning the entire developmental history of the peatland. Results indicate that true carbon accumulation and sequestration efficiency rates in ombrotrophic peatlands are lower in the upper Mackenzie Valley than for other boreal regions, primarily owing to high decomposition rates. The cessation of carbon accumulation is being approached. The model also serves to highlight the dangers of using apparent and true carbon accumulation rates interchangably. / Apparent and true carbon accumulation rates are significantly lower than published rates from other parts of northern Canada, Finland, and the Former Soviet Union. Low and variable summer precipitation in the region may be a significant factor through increased aerobic decomposition and/or decreased plant production caused by moisture stress.

Reliable determinations of ecosystem scale fluxes of net carbon (C) and greenhouse gases for northern peatland ecosystems are of great value to determine the impact of soil warming and altered precipitation on emissions. Additionally, few studies have been performed which measure the C fluxes, particularly methane flux (FCH4), during the spring melt and fall freeze up periods, therefore making it difficult to provide adequate annual C estimates from northern peatland ecosystems. This study aimed to determine ecosystem scale FCH4 from a eutrophic Subarctic fen at Churchill, Manitoba (58°45'N 94°4'W), to understand (a) seasonal trends over two consecutive growing seasons,(b) if over-winter stored CH4 was released as a pulse during the spring-melt period, and (c) soil temperature - FCH4 relations for modelling FCH4 over the spring-melt period. An ecosystem scale methane (CH4) and carbon dioxide (CO2) flux measurement system using the eddy covariance (EC) technique was used from late-June to mid-October of 2008 and early-June to late-September of 2009, with focus on the spring-melt period of late-May to mid-July of 2009. The EC flux measurement system consisted of a closed-path RMT-200 Fast Methane Analyzer (Los Gatos Research Inc.) along with a LI-7500 open-path CO2/H2O gas analyzer (LI-COR Biosci.) and a CSAT3 3-dimensional sonic anemometer (Campbell Sci.). The system was powered by a combination of wind, solar, and gas electric generation. The EC flux measurement system provided seasonal FCH4 values of 0 – 90 nmol CH4 m-2 s-1, similar to previous studies in Subarctic and Arctic peatlands which incorporated the EC technique. A melt period CH4 emission burst was not observed, rather a gradual increase in emission over the spring period. Modelled FCH4 using a temperature-response curve relationship with soil temperature at 5 cm depth over the spring-melt period (May 30 – July 19, 2009) showed the fen to be a net source of CH4, of 1.4 mmol m-2 CO2 equivalent.

The term palsa is a Fennoscandian word for a peaty hillock or mound having a permafrost core composed of alternating layers of segregated ice lenses, and organic or mineral soil. This dissertation presents results of a study on the morphology, ecology, cryotic structure, and thermal regime of 6 palsas sites in the Schefferville area and offers a new categorization of these features based on their cryotic structure. Eighteen palsa sites were located within a 35 km radius of Schefferville and six of these sites were investigated in detail. Palsas ranged from 5.6-59.0 m in length and up to 1.1 m in height. Most were located in valleys formed by the strong ridge-valley topography of the Labrador trough. Analysis of plant macrofossils suggests a successional change from hydrophilic species 10-15 cm below the palsa surface to relatively xerophilic species on the palsa surface. The transition zone between these vegetation associations indicates when the peat surface was heaved above the water table and thus, the initiation of the palsa. Surface vegetation on the palsas is used to indicate stage or category of development. Lichens and shrubs combined with small amounts of bare peat suggest a stable palsa. Large areas of bare peat on the surface of palsas resulting from erosion indicates degradation. Healthy sedges on the palsa surface indicate aggrading conditions. Ground ice within palsas ranged from small discontinuous ice lenses within peat to large lenses at the peat mineral soil contact and within the mineral soil. The depth of snow on the palsa surface varied on both a temporal and spatial basis. Active layer depths were not greatly affected by the depth of winter snow. Climatic parameters, such as heating degree days and bright sunshine hours, were found to predict maximum active layer depths more accurately than Stefan's equation. This dissertation shows that palsas with both organic and mineral soil cores are common permafrost features in the Schefferville area

Reliable determinations of ecosystem scale fluxes of net carbon (C) and greenhouse gases for northern peatland ecosystems are of great value to determine the impact of soil warming and altered precipitation on emissions. Additionally, few studies have been performed which measure the C fluxes, particularly methane flux (FCH4), during the spring melt and fall freeze up periods, therefore making it difficult to provide adequate annual C estimates from northern peatland ecosystems. This study aimed to determine ecosystem scale FCH4 from a eutrophic Subarctic fen at Churchill, Manitoba (58°45'N 94°4'W), to understand (a) seasonal trends over two consecutive growing seasons,(b) if over-winter stored CH4 was released as a pulse during the spring-melt period, and (c) soil temperature - FCH4 relations for modelling FCH4 over the spring-melt period. An ecosystem scale methane (CH4) and carbon dioxide (CO2) flux measurement system using the eddy covariance (EC) technique was used from late-June to mid-October of 2008 and early-June to late-September of 2009, with focus on the spring-melt period of late-May to mid-July of 2009. The EC flux measurement system consisted of a closed-path RMT-200 Fast Methane Analyzer (Los Gatos Research Inc.) along with a LI-7500 open-path CO2/H2O gas analyzer (LI-COR Biosci.) and a CSAT3 3-dimensional sonic anemometer (Campbell Sci.). The system was powered by a combination of wind, solar, and gas electric generation. The EC flux measurement system provided seasonal FCH4 values of 0 – 90 nmol CH4 m-2 s-1, similar to previous studies in Subarctic and Arctic peatlands which incorporated the EC technique. A melt period CH4 emission burst was not observed, rather a gradual increase in emission over the spring period. Modelled FCH4 using a temperature-response curve relationship with soil temperature at 5 cm depth over the spring-melt period (May 30 – July 19, 2009) showed the fen to be a net source of CH4, of 1.4 mmol m-2 CO2 equivalent.

Boreal peatlands are important ecosystems to the global carbon cycle. Although they cover only 3% of the earth's land surface area, boreal peatlands store roughly one third of the world's soil carbon. Peatlands also comprise a large natural source of methane emitted to the atmosphere. Some methane in peatlands is oxidized before escaping to the atmosphere by aerobic methane oxidizing bacteria. With changing climate conditions, the fate of the stored carbon and emitted methane from these systems is uncertain. One important step toward better understanding the effects of climate change on carbon cycling in peatlands is to ascertain the microorganisms actively involved in carbon cycling. To investigate the active aerobic methane oxidizing bacteria in a boreal peat bog, a combination of microcosm experiments, DNA-stable isotope probing, and next generation sequencing technologies were employed. Studies were conducted on samples from the S1 peat bog in the Marcell Experimental Forest (MEF). Potential rates of methane oxidation were determined to be in the range of 13.85 to 17.26 μmol CH₄ g dwt⁻¹ d⁻¹. After incubating with ¹³C-CH₄, DNA was extracted from these samples, separated into heavy and light fractions with cesium chloride gradient formation by ultracentrifugation and needle fractionation, and fractions were fingerprinted with automated ribosomal intergenic spacer analysis (ARISA) and further interrogated with qPCR. Based on ARISA, distinct banding patterns were observed in heavy fractions in comparison to the light fractions indicating an incorporation of ¹³C into the DNA of active methane oxidizers. This was further supported by a relative enrichment in the functional gene pmoA, which encodes a subunit of the particulate methane monooxygenase, in heavy fractions from samples incubated for fourteen days. Within heavy fractions for samples incubated for 8 and 14 days, the relative abundance of methanotrophs increased to 37% and 25%, respectively, from an in situ abundance of approximately 4%. Phylogenetic analysis revealed that the methanotrophic community was composed of both Alpha and Gammaproteobacterial methanotrophs of the genera Methylocystis, Methylomonas, and Methylovulum. Both Methylocystis and Methylomonas have been detected in peatlands before, however, none of the phylotypes in this study were closely related to any known cultivated members of these groups. These data are the first to implicate Methylovulum as an active methane oxidizer in peatlands, though this organism has been detected in another cold aquatic ecosystem with consistent methane emissions. The Methylovulum sequences from this study, like Methylocystis and Methylomonas, were not closely related to the only cultivated member of this genus. While Methylocystis was dominant in ¹³C-enriched fractions with a relative abundance of 30% of the microbial community after an eight-day incubation, Methylomonas became dominant with a relative abundance of approximately 16% after fourteen days of incubation. The relative abundance of Methylovulum was maintained at 2% in ¹³C- enriched fractions after eight and fourteen days.

Northern peatlands are an important long-term sink for atmospheric carbon dioxide (CO2) and a contemporary source of methane (CH4). Under contemporary climate and environmental change, including enhanced nutrient deposition through industrialization and commercial peat harvesting, the microbial environment in peat is altered. Microorganisms are responsible for the net production of greenhouse gases in these sites, although controls on microbial activity and microbial communities are poorly understood, limiting our ability to predict greenhouse gas emissions. The objective of this thesis was to determine the microbial role in peat decomposition and greenhouse gas fluxes in northern peatlands. Nutrient, carbon (C) substrate, and microbial-ecological controls on microbial activity under natural climate variability, increased nutrient deposition, and commercial harvesting and restoration were explored in detail. Environmental change effects were evaluated in relation to processes and temporal variability in pristine sites. / The natural temporal variability of decomposition, microbial biomass, and nitrogen (N) was characterized in the Mer Bleue bog near Ottawa, ON over two years. In a warmer, drier year, lower water table position corresponded to increased N availability, which was in turn linked to enhanced microbial CO2 production, consistent with patterns in ecosystem respiration measured at the site level. It was shown that microbial activity can play an important role in inter-annual climate driven ecosystem respiration and net ecosystem CO2 exchange. / Through field and laboratory nutrient fertilization experiments, it was shown that increased nitrogen (N) deposition altered the heterotrophic microbial community at Met Bleue and led to decreased decomposition rates after one year, despite increased total microbial biomass. After the second year of fertilization, however, decomposition rates were elevated, presumably a result of a concomitant shift in moss species and supply of more bioavailable plant material. Comparison of fertilizations in the presence and absence of vegetation indicated that in oligotrophic sites, vegetation mediated elevated nutrient effects on decomposition and that N cycling occurred largely in the organic forms. / Aerobic and anaerobic microbial activity, peat organic and nutrient chemistry, microbial biomass, and methanogen, CH4-oxidizing bacteria, bacteria, and archaea were characterized in two sets of pristine, actively harvested, harvested and abandoned, and harvested and restored peatlands in Quebec and New Brunswick.

Net ecosystem exchange of CO$ sb2$ (NEE) and CH$ sb4$ flux were measured at five sites within a boreal peatland near Thompson, Manitoba, from June through September, 1994. Sites were chosen to represent the different plant communities present along a productivity gradient where the water table was at or near the peat surface. Methane emissions, water table depth, and peat temperature were measured on weekly basis, while the relationship between photosynthetically active radiation (PAR) and net ecosystem exchange of CO$ sb2$ was determined three times during the field season, and then used to develop net ecosystem production (NEP) models at each site. Porewater methane was sampled for $ rm delta sp{13}C/ sp{12}C$ isotopic analysis once a month. / Among the sites, after PAR, light CO$ sb2$ flux was primarily controlled by sedge biomass and water table position, while dark CO$ sb2$ flux was controlled by peat temperature. From early June to late August, the five sites consumed approximately 1 to 2 g $ rm CO sb2$-C m$ rm sp{-2}d sp{-1}$. Seasonal CH$ sb4$ fluxes ranged between 16 and 456 mg $ rm CH sb4 m sp{-2}d sp{-1}$, and were higher than fluxes measured at other boreal sites in the same latitude. Seasonal average NEP was a good predictor of seasonal CH$ sb4$ fluxes from the sites (r$ sp2$ = 0.50), providing a model which estimates CH$ sb4$ flux based on site productivity alone. Stable carbon isotope analysis indicates root exudates that stimulate methanogenesis are an important control on this relationship, as is a high water table, particularly in its influence on the depth of the CH$ sb4$ oxidizing layer in the peat. These results suggest NEP measurements have the potential to be used in remote sensing applications to estimate CH$ sb4$ flux from wetlands, but that their use may be restricted to inundated sites.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.