Thesis (M.Sc.) - Carleton University, 2008. / Includes bibliographical references (p. 79-84). Also available in electronic format on the Internet.

Boreal peatlands play important roles in global C and nutrient cycling. Oligotrophic bogs are naturally nitrogen (N) limited, receiving nutrients only via atmospheric deposition. Increased nutrient deposition, particularly N will almost certainly change the microbiology, biogeochemistry, and C and nutrient balances in bogs. Both primary production and decomposition can be affected, but the net effects of N fertilization are complex and unclear. A three-year N fertilization experiment with 15N double labeled 15NH415NO3 as a tracer was designed to study the effects of increasing N deposition on various N pools (including microbial communities, moss, roots, litter, and aboveground vascular plants) and how these N pools process and retain applied N in four ombrogenous bogs in northern Alberta, Canada. Linear growth of Sphagnum mosses was highly variable. However, both capitulum and stem weight showed increase in weight with N addition, resulting in significant increase of capitulum and stem bulk density with N deposition. Total annual primary production, with both capitulum and stem growth accounted for, doubled from low N deposition plots to high N deposition plots. Microbial biomass N measured by chloroform fumigation-extraction only showed a decrease with N deposition in the first year of the experiment. Fungal biomass declined with N deposition as nutrients are readily available under high N loads, perhaps eliminating the need for help from symbiotic fungi for nutrient uptake. The growth of Sphagnum mosses and microbial communities may have been influenced by drier and warmer growing period during 2005 to 2007. These abnormal climatic events could have masked the effects of N deposition on surface Sphagnum moss and microbial communities. This 15N tracer experiment revealed high retention rates of 15N by moss layers as expected. However, retention efficiency of moss layers declined over time and with increasing N deposition, indicating a leakier system as N deposition exceeds the critical load of Sphagnum moss. Aboveground vascular plants overall benefited from N deposition, but different species responded differently based on the root morphology, rooting depths, and the mycorrhizae associations.

Palmiet peatlands in the agricultural landscape are viewed by farmers as problematic. They obstruct the effective passage of water along watercourses and therefore promote localized flooding of lands and infrastructure, and they trap sediment delivered along watercourses that drowns fields and infrastructure with sedimentary deposits. These events are problematic for farmers trying to make a living off the land. Wetlands are also often viewed as wastelands that should be put to more productive use. The obvious thing to do is to bring in machinery to drain the wetlands and improve the flow of water and sediment through these wetlands.

Peatlands in Southern South America (SSA), in the path of the Southern Westerly Wind belt (SWW), offer the potential of reliable palaeoclimate archives. This investigation aimed to test the late-Holocene climate signal related to variability of the SWW. Three sites were investigated: San Juan and Karukinka bog, southernmost Chile and San Carlos, a Sphagnum dominated bog, discovered in the Falkland Islands, to form a regional comparison. A multi-proxy approach was used, combining both palaeoecological and stable isotopic methods. At one site, Karukinka, intra-site replicability was tested across three profiles located along a microtopographical gradient. A low number of statistically significant correlations between proxies were evident. KAR-EM-1, the low-hummock profile, displayed the highest number of significant correlations, suggesting an optimal coring location. Chronological uncertainty in the high-hummock profile, KAR-EM-3, was the focus of discussion. Intra-site replicability between the palaeoecological records was improved by plotting the records against a ‘master chronology’, from the mid-hummock profile, KAR-EM-2, assuming a synchronous acrotelm-catotelm boundary across the profiles. The testate amoeba inferred depth to water table (WTD) reconstructions offered the highest intra-site coherence, while the stable isotope records suggested generally poor intra-site replicability. A semi-quantitative method of intra-site comparison was carried out which resulted in a number of climate scenarios. The inter-site comparison assessed correlations between the records from the three sites. A lack of significant correlations between the sites may have been due to regional climate variations and differences in the temporal resolution of the records. Robust climatic inferences were limited to the last 300 years. The WTD reconstructions displayed the highest inter-site coherence and suggested a drying trend after AD 1930 due to a southerly shift of the SWW. Late-Holocene climate variability was inferred from the palaeoecological records from Karukinka. Two periods were identified: a MCA period of generally wetter conditions (AD 750-1100) and a LIA period of overall drier conditions (~AD 1100-1900) during a southerly and northerly shifted SWW respectively, driven by solar variability and polar cell strengthening.

Large areas of northern peatlands have been drained and afforested in the second half of the 20th century with significant impacts on important ecosystem services, including loss of biodiversity and potential changes in C storage. A considerable effort is currently invested into restoring original peatland function and ecosystem services, with an increasing area of newly restored peatland areas over recent years. However, the effect of restoration on the greenhouse gas (GHG) budget is unknown. This study is the first quantification of CO2, CH4 and N2O fluxes from forest-to-bog restoration sites spanning 0 to 17 years in age. Further, the impact of afforestation on peat decomposition is measured in situ, and the impact of afforestation on the biochemical composition of the peat in relation to CO2 and CH4 fluxes is investigated. Results show that forest-to-bog restoration is successful from a GHG perspective, since all three major GHG fluxes of the restoration sites are changing along the chronosequence towards the fluxes from near pristine bog sites. The peat decomposition rate under the forest plantations is a big part of the total soil respiration at 126.8 ± 14.7 g C m-2 y-1 (44% of total soil CO2 efflux) and our results indicate a slowing down of peat decomposition towards the near pristine bog. CH4 fluxes increase with restoration age, whilst all sites remain a small sink for N2O. I observed changes in peat quality and nutrient availability in the pore water under forests. Different CO2 fluxes between vegetation-free peat cores from different sites for the same temperature and water level show that these differences in peat quality and nutrient availability shape the biogeochemical processes in the peatlands. However only small differences in CH4 fluxes between sites were evident, suggesting that on its own (and in absence of biotic interactions under field conditions), forestry effects on CH4 flux are limited.

Inland waters including streams, rivers, reservoirs and lakes are regarded as a significant site of Organic Carbon (OC) cycling, and greenhouse gas production. As a result, there has been significant recent interest in the rates and fate of fluvial carbon exported from organic soils, such as peatlands. Additionally, peatlands can be subject to substantial degradation resulting in high rates of fluvial OC export, and this has led to efforts to repair degraded peatlands through restoration programmes. As a consequence, the study of degraded areas is useful to quantify the upper values of carbon release, understand processes of transformation, and evaluate the success of restoration programmes. Importantly peatlands are also collection areas for drinking water, which has implications for treatment, and requires better understanding of carbon cycling upstream of treatment works, in headwater rivers, reservoirs and pipes. UK upland blanket peat catchments are a key location in which to consider global questions surrounding fluvial carbon export and transformations, as they are highly degraded, provide a source of drinking water supply, and are currently undergoing pioneering methods of landscape scale restoration. This thesis considers Kinder Scout, an area of highly degraded and gullied blanket peatland in the South Pennines, UK. Using analysis of water samples collected over several years in the Kinder reservoir catchment and plateau, this thesis presents three novel contributions to global questions concerning OC cycling and peatlands. Firstly it provides (to date), the only carbon budget for a reservoir in a peat dominated catchment with high Particulate Organic Carbon (POC) export, which demonstrates that reservoirs may be net sources of Dissolved Organic Carbon (DOC), with the implication that POC-DOC interactions are important OC transformation mechanism in degraded systems. Secondly through use of a unique integrated combination of methods, it considers changes in carbon flux and composition in both river, lake and pipe locations, providing detailed understanding of the relative roles of river reaches, reservoirs and supply pipes, in controlling fluvial carbon cycling in peatland systems, and upstream of water treatment works. An important implication here, is that rate and direction of change in water treatability varies through a catchment. Finally, it includes results from the first widespread monitoring of the catchment scale effects of a new method of peatland revegetation. This restoration approach is being applied at landscape scale and the findings here, are that despite fears to the contrary, it does not lead to short term increases in fluvial carbon loss, which is an important piece of evidence supporting practical conservation approaches in these systems. To further enhance this research, a combination of field and laboratory investigations into carbon transformation processes, and ongoing restoration mentoring should be undertaken.

Variations in drainage density have been observed in a range of environments as the perennial stream network expands into headwater reaches. This network expansion and contraction results in large changes in drainage density and as such, has implications for the connectivity of the catchment and the associated flux of water, sediments and solutes. One environment where these changes have been observed is peatlands. The accurate characterisation of catchment connectivity in peatlands is desirable for a number of reasons, not least to understand the controls on carbon flux. In addition, the accurate characterisation of these systems will help us to predict the impacts of a changing climate. It is hitherto been difficult to quantify changes in connectivity due to the logistical difficulties of monitoring this phenomenon. The use of Electrical Resistance (ER) technology has shown potential to detect the presence and absence of water. This method is built on here and a range of sensors are developed to monitor connectivity at high temporal and spatial resolutions, specifically flow in ephemeral portions of the channel network, pipeflow and overland flow. The study takes places in the Upper North Grain research catchment, a small peatland headwater catchment in the south Pennines, UK. The data collected on ephemeral streamflows highlight the importance of water table as a control on changes in network extent in the study catchment, as the presence or absence of flow at each site is strongly controlled by local water table. This allows the minimum and maximum drainage density within the catchment to be determined, as well how frequently these states occur. Pipe stormflow generation appears to be strongly linked to the production of saturation excess overland flow. The pipe network is very sensitive to small inputs of rainfall. In contrast, pipe baseflows seem to be controlled by water table level as pipes are fed by seepage from the peat mass. Pipe behaviour could not be related to any of the morphological characteristics presented here and is though to be dependent on the subsurface morphology of the pipe network. Overland flow production was monitored at a gully head and gully side location. At the gully head the incidence of overland flow increased with distance from the gully edge due to higher local water tables encouraging the production of saturation excess overland flow. At the gully side, extreme water table drawdown has caused the peat to become hydrophobic and the incidence of overland flow is high here, due to infiltration excess. This signifies a major advancement in our knowledge of runoff pathways in peatlands as the importance of infiltration excess overland flow has not been acknowledged until now. In general, ephemeral streamflows occur before the production of either overland flow or pipeflow as incident rainfall causes saturation of the gully floors. The temporal pattern of overland flow and pipeflow is similar, although pipeflow continues after overland flow ceases and is thought to be fed by shallow subsurface flow on the recession limb. Both overland flow and pipeflow precede discharge at the catchment outlet by several minutes. The interaction of these processes is examined under both ‘wet’ and ‘dry’ antecedent conditions. The data collected here provide an accurate characterisation of the dynamics of, and controls on, peatland connectivity under current climatic conditions, providing a reference point to which future observations can be compared.

abstract: Nitrous oxide (N2O) is an important greenhouse gas and an oxidant respired by a diverse range of anaerobic microbes, but its sources and sinks are poorly understood. The overarching goal of my dissertation is to explore abiotic N2O formation and microbial N2O consumption across reducing environments of the early and modern Earth. By combining experiments as well as diffusion and atmospheric modeling, I present evidence that N2O production can be catalyzed on iron mineral surfaces that may have been present in shallow waters of the Archean ocean. Using photochemical models, I showed that tropospheric N2O concentrations close to modern ones (ppb range) were possible before O2 accumulated. In peatlands of the Amazon basin (modern Earth), unexpected abiotic activity became apparent under anoxic conditions. However, care has to be taken to adequately disentangle abiotic from biotic reactions. I identified significant sterilant-induced changes in Fe2+ and dissolved organic matter pools (determined by fluorescence spectroscopy). Among all chemical and physical sterilants tested, γ - irradiation showed the least effect on reactant pools. Targeting geochemically diverse peatlands across Central and South America, I present evidence that coupled abiotic and biotic cycling of N2O could be a widespread phenomenon. Using isotopic tracers in the field, I showed that abiotic N2O fluxes rival biotic ones under in-situ conditions. Moreover, once N2O is produced, it is rapidly consumed by N2O-reducing microbes. Using amplicon sequencing and metagenomics, I demonstrated that this surprising N2O sink potential is associated with diverse bacteria, including the recently discovered clade II that is present in high proportions at Amazonian sites based on nosZ quantities. Finally, to evaluate the impact of nitrogen oxides on methane production in peatlands, I characterized soil nitrite (NO2–) and N2O abundances along soil profiles. I complemented field analyses with molecular work by deploying amplicon-based 16S rRNA and mcrA sequencing. The diversity and activity of soil methanogens was affected by the presence of NO2– and N2O, suggesting that methane emissions could be influenced by N2O cycling dynamics. Overall, my work proposes a key role for N2O in Earth systems across time and a central position in tropical microbial ecosystems. / Dissertation/Thesis / Doctoral Dissertation Microbiology 2020

Groundwater seepage to surface water is an important process to peatland ecosystems; however, the processes controlling seepage zone distribution and magnitude are not well understood. This lack of process-based understanding makes degraded peatland ecosystems difficult to restore and problematic for resource managers developing a sustainable design. Degraded peatlands, particularly abandoned cranberry farms, often have drainage ditches, applied surface sand, and decreased stream sinuosity to artificially lower the water table and support agriculture. These modifications disconnect the surface and groundwater continuum, which decreases thermal buffering of surface water significantly. The combination of a decreased influx of thermally buffered groundwater, a naturally low surface gradient, minimal canopy, and strong solar input causes surface water temperature extremes that degrade ecosystem health. Through strategically incorporating the natural processes to restore groundwater discharge to restored surface streams, surface water temperature extremes will be buffered promoting a healthy, resilient wetland ecosystem. Therefore, it is critical to understand the spatial hydrogeologic constraints that induce groundwater seepage. Here we examine the spatial relationship between surficial groundwater seepage and the subsurface hydrogeologic structure within a mineraltrophic peatland environment. We use multiple field methods to develop a process-based conceptual model of the ground water seepage development at the site; these methods include geophysical, thermal, and isotopic techniques. The results indicate that there are two distinct forms of groundwater discharge to the peatland platform: diffuse lower-flux marginal seepage and discrete higher-flux interior seepage. Both types of groundwater discharge develop through interactions with subsurface peatland basin structure, specifically when the basin slope is perpendicular to the regional groundwater gradient. These observations also allow insight into the formation of the groundwater discharge through time. The strong correlation between the subsurface basin structure and surficial groundwater expression will allow resource managers to more efficiently locate groundwater seepage on large, complex sites, and develop comprehensive management and restoration strategies for these critical ecosystems.

There is an extended concern for how to quantify the fluxes of greenhouse gasses (GHG) and how they are related to climate change and land use. Efforts have already been done, mostly regarding carbon (C) compounds, but there is still much to be done especially to understand regulating factors and interactions with the Nitrogen cycle. NitroEurope is a large project for the integrated European research into the N cycle. This study shares its aim, to improve the understanding the physics involved in the fluxes of the reactive N (Nr). More specifically, the patterns of some physical and biological processes related to Nr have been studied for two wetlands, one in the proximity of Edinburgh and the other in the North of Finland.   A common model setup has been used for both of them, since they are both peat soils. The differences applied to achieve appropriate performances give insights of their nature. The presence of snow is a major factor that governs the behavior of the site in Finland. The scaling of existing models for the estimation of heat transfer in the soil of the Scottish site is also critical, such as its groundwater level. The sites represent different climatic conditions, but for CO2 fluxes they showed similar behavior and response to governing meteorological conditions. Using the GLUE method in combination with a process oriented ecosystem model, some further insights have been gained for the regulation and control of greenhouse gas emissions from the two sites.