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<p>Northern peatlands (>45°N) mostly initiated during the Holocene and have been a large C sink to the atmosphere. Northern peatland formation prefers wet and cold condition where the productivity persistently exceeds decomposition and thereby C accumulates. As the northern high latitude region is likely to be warmer in the future, whether northern peatlands will continue being C sinks or switch to C sources is uncertain. To address this issue, I revise and apply a process-based model designed for describing peatland biogeochemical processes, Peatland Terrestrial Ecosystem Model (PTEM), to simulate the C dynamics at both site and regional level, from 15 ka BP-2300. For the site-level simulation, PTEM 1.0 is substantially revised into PTEM 2.0 in terms of peat accumulation process, plant functional types, productivity and decomposition, and soil thermal properties. A simulation from peat initiation to 2300 is conducted for three northern peatland sites. I found PTEM 2.0 can effectively capture the historical C accumulation progress, when compared with the observation. The future simulation indicates northern peatlands have reduced C sink capacity or switch to a C source under N insufficiency and water table deepening. </p> <p>Afterwards, a historical pan-Arctic simulation during 15ka BP-1990 is conducted. PTEM 2.0 is revised into PTEM 2.1 by adding spatially-explicit run-on and run off processes. The spatially-explicit peat initiation dataset is derived from neural network approach and a spatially-explicit peat expansion trend is established on top of it. My estimated pan-Arctic peatland C storage is 396-421 Pg C with the long-term C accumulation rate (CAR) of 22.9 g C∙m-2 yr-1. The simulated spatial distribution of peat C and the temporal pattern of CAR both agree with literature values. I analyzed northern peatlands’ response to historical climate change since 0.5 ka BP and found decreased CAR in the warmer non-permafrost and permafrost-thaw region, while the opposite was found in the colder permafrost region. The results indicate warmer southern peatlands will first switch to a C source under warming while more northern peatlands will become larger sinks. </p> <p>Based on the result of historical simulation, a future simulation is conducted for 1990-2300 with peatland expansion/shrinkage considered. PTEM 2.1 is revised into PTEM 2.2 such that the water table depth, run-on and run-off are estimated from a TOPMODEL approach. In the 21st century, northern peatlands are projected to be a C source of 1.2-13.3 Pg C under five out of six climate scenarios. During 2100-2300, northern peatlands under all scenarios are a C source under all climate scenarios. Northern peatlands switch to C sources due to deepening water table depth, insufficient N availability, and plant functional type shift. I found that northern peatlands remain as a C sink until a mean pan-Arctic peatlands annual temperature reaches -2.09 - -2.89°C. This study predicts a northern peatland sink to a source shift around 2050, earlier than previous estimates of after 2100, and emphasizes the vulnerability of northern peatlands to climate change. </p>

Northern peatlands have acted as persistent sinks of CO2 throughout the Holocene largely owing to their ability to maintain shallow water table depths that limit decomposition rates and supports the growth of keystone vegetation including Sphagnum mosses. There is concern, however, that the future success and ecosystem function of these northern peat deposits may be at risk to climate change, where temperatures and evaporation rates are predicted to increase substantially in the next century. While numerous studies have examined the hydrology and carbon dynamics in large expansive peatland systems where a water table (WT) is ever-present, relatively little research has been done on small scale peat-accumulating systems where their vulnerability remains unknown. One region where a broad spectrum in the scale of peat accumulation is present is in the bedrock depressions of Canadian Shield rock barrens, which are of special importance as many peat deposits here provide habitat to species at risk including the Blanding’s Turtle and the Massassauga Rattlesnake. This study examines the controls that govern water storage dynamics and moss water availability in 18 different peat-accumulating depressions that vary in size, catchment area, and sediment composition. The magnitude of WT variability was often several times greater in shallower bedrock depressions (<50 cm deep) as compared to deeper ‘bogs’ (>60 cm deep). The magnitude of depression WT variability appeared to be closely linked to the WT depth (WTD), the relative proportions of different sediment types within the depression, and the depth dependant specific yield (Sy) of each sediment type. Sites which contained large fractions of Polytrichum moss or mineral soil – which were more common in shallow depressions ¬¬– had the greatest WT variability due to the lower porosity and Sy of this sediment as compared to Sphagnum peat. Sphagnum dominated ‘vernal pools’ (30-50 cm deep) had a WT variability two to three times greater than Sphagnum dominated bogs at WTDs > 20-25 cm, which may be related to exceptionally high ash concentrations near the base of vernal pools which reduced peat porosity and Sy as compared to more organic-rich peat. As compared to bogs, pits (<15 cm deep) and vernal pools had greater rates of WT decline during drying intervals, deeper average WTDs when a WT was present, and extended periods of WT absence during the summer months. As such, moss growing in pits and vernal pools generally had lower near-surface water availability as compared to bogs, though the importance of depression depth in determining the timing of moss stress is also dependant on the hydrophysical properties (Kunsat and moisture retention) of the moss species in question. WT dynamics and moss water availability were generally weakly correlated to depression catchment size, although during wetter periods of the year the rate of WT recession was moderated in pits and vernal pools which had an upslope depression that could provide sustained water inputs for multiple days after rainfall. The results of this study suggest that depression depth may be a first order control in determining peatland vulnerability to future regime shifts induced by external forcings or disturbances. Furthermore, this study suggests that systematic differences may exist between the hydrophysical properties of peat in shallow vs. large bedrock depressions, potentially resulting from contrasts in fire frequency/severity, and/or the degree of humification/compression among geological settings. / Thesis / Master of Science (MSc) / Canada is home to one of the largest reservoirs of organic carbon stored on land in the world, in unique ecosystems called peatlands. Peatlands are formed in wetland environments where a thick layer of organic matter has accumulated over time due to the average rate of vegetation growth on the surface of peatlands exceeding the rate of decomposition of the underlying organic matter. This net accumulation of organic matter over time has caused peatlands to act as a long term sink of carbon dioxide, which is a greenhouse gas that is a primary driver of global warming. The ability of peatlands to have slow decomposition rates and support the growth of key peatland vegetation, most notably various species of ‘peat moss’, is highly dependent upon their ability to keep their water table (i.e. the surface below which pore spaces in the organic matter are saturated with water) close to their growing surface. There is concern, however, that a warmer and dryer climate in the future could cause deeper water table positions in peatlands, thereby increasing decomposition rates, decreasing the growth rate of peat moss, and potentially turning peatlands into a net source of carbon dioxide. Most peatland studies to date, however, have focused on water storage/movement and carbon exchange in large, deep peatland systems, whereas relatively little research has been conducted on smaller peatlands. As such, the vulnerability of these smaller peatlands to future climate change remains uncertain. One region where peatlands exist over a wide range of different sizes and landscape positions is in bedrock depressions of the Canadian Shield, which are of special interest as they also provide habitat for species at risk including the Blanding’s Turtle and the Massassauga Rattlesnake. This study looked at how the water table positions and water availability to different species of peat moss compared over the growing season between 18 peatlands of different sizes and landscape position (i.e. peatlands with a relatively ‘small’ and ‘large’ area upslope of them). This study finds that deeper peatlands (with organic matter layers > 60 cm deep) usually had a shallower water table over the summer months than shallower peatlands (< 50 cm deep), primarily due to differences in the properties of the organic matter underlying their growing surfaces. Furthermore, each of the 12 studied peatlands < 50 cm deep lost their water table for a considerable amount of time during the summer (when their water table position dropped below the underlying bedrock of the depression), whereas each of the six peatlands > 60 cm deep had a water table present for the entire growing season. Surprisingly, a peatland’s position on the landscape seemed to have a relatively minor effect on determining the depth/presence of its water table. As deeper peatlands usually had a water table that was closer to the growing surface and was always present, more moisture was available to the peat moss growing at their surface than for peat moss in shallower depressions, though this moisture availability also depended upon the growth form of the different species of peat moss (some species of peat moss were better at accessing subsurface water than others). Through its impact on water table positions and moisture availability for peat moss, peatland depth is likely a primary control governing peatland vulnerability climate change, with shallower peatlands being more vulnerable to warmer and dryer conditions in the future.

The question of peatlands management in Ireland is characterised by tensions between environmental, social and economic concerns, making it of central relevance to the field of sustainable development. This thesis examines the complexities associated with the current peatlands landscape in Ireland through the analytical framework of social-ecological systems including the concepts of environmentalism, heritage and future agency. The landscape and its complexities are demonstrated through an analytical description, the analysis of interviews with Irish people involved in peatlands, and the development of future scenarios. The results show that the Irish peatlands landscape is a highly complex topic displaying clashes between rural communities, government and environmental authorities in numerous ways. They also indicate that the heritage associated with Irish peatlands is diverse and multi-dimensional. Within this context, there is a need for balance between environmental and social concerns. However, the question of sustainability might never be settled in the future and instead will likely require constant evaluation and re-evaluation by the various actors involved in carrying it out.

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Reptiles are the vertebrate taxon with the highest percentage of at-risk species in Canada, many of which exist at the northern limit of their species’ home range in Ontario. Numerous reptiles are found in the Georgian Bay area; however, factors limiting their distribution in Ontario are poorly understood. It is likely that the thermal and hydrological conditions of a reptile’s critical habitat are contributing factors. Specifically, peatlands serve as ideal hibernacula for the threatened Eastern Massasauga Rattlesnake (Sistrurus catenatus) while moss cushions may provide freshwater turtles, including the threatened Blanding’s Turtle (Emydoidea blandingii) and endangered Spotted Turtle (Clemmys guttata), with nesting opportunities on open rock barrens. Although different in their functional purpose at opposite life stages for two separate orders of reptiles, these ecosystems provide suitable conditions to meet the physiological needs of the reptiles utilizing them. This analysis characterizes the thermal and hydrological conditions of moss-dominated ecosystems from a reptile species-at-risk perspective. The interaction between the water table and the frost line is important when assessing the winter survival of Eastern Massasauga Rattlesnakes hibernating in peatland hummocks. Larger hummocks are more ideal as they have a lower chance of becoming flooded in the winter while still providing protection from the advancing frost line. Ideally, hummocks that are 30-35 cm tall provide the greatest chance of survival when snakes hibernate 20-25 cm below the surface. Subsurface temperatures in relation to snow depth, as it is influenced by tree stand characteristics, was also assessed. This resulted in the conclusion that the presence, absence, timing, and frequency of freeze and thaw events is likely more important than snow depth when it comes to winter survival. Similar to rattlesnake hibernacula, turtle nests can be inundated for extended periods of time or exposed to extreme temperatures which reduces their chance of survival. The water storage dynamics of 22 hillslope and 12 hilltop moss cushions along with the temperature dynamics at nine locations were characterized. Although it was determined hilltop locations had greater water storage capabilities, continuously monitored moss cushions responded very quickly to rainfall events whereby sites were inundated for less than 12 hours. Average subsurface temperatures decreased with depth as did temperature fluctuations, both of which were positively correlated but not significantly affected by canopy openness. However, due to their tendency to grow on flat surfaces, not all moss cushions are suitable nesting sites. Moreover, temperatures that ensure proper development and equal ratios of male-to-female turtles were not achieved suggesting that this is a potential factor limiting the northern distribution of turtles in Ontario. In order to properly asses the vulnerability of these populations to threats including habitat loss and climate change, the habitat requirements of different species at critical life stages needs to be understood. Therefore, conservationists can use this study to implement mitigation strategies that consider impacts on the thermal and hydrological dynamics within reptile habitat. / Thesis / Master of Science (MSc)

Yes / User-generated reviews of visitor attractions, on publicly available websites, such as Tripadvisor, are frequently used in tourism research but feature less often in published cultural heritage research. In this paper, we describe a qualitative analysis of the text from user-generated reviews of three peatland heritage landscapes in the United Kingdom – Ilkley Moor, Thorne and Hatfield Moors, and Shapwick Heath – to better understand the role tangible and intangible cultural heritage play in visitor perceptions and narratives of these sites. Our analysis indicates that visitors tend to emphasise natural over cultural heritage of peatland landscapes and hold plural, highly contextual and sometimes dissonant perceptions; there is no single story of peatlands. This presents both challenges and opportunities for building public appreciation of peatland cultural heritage. User-generated reviews offer, as-yet under-explored, potential data for use by heritage researchers and managers who seek to explore how visitors understand and use sites, and may also contribute to the emerging intangible heritage of heritage landscapes. / Research Development Fund Publication Prize Award winner, June 2021.