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Examination of peat samples collected from hummocks and hollows within a confined bog reveals that peat collected from different locations, designated by surface topography, vary in ash content, ash alkalinity, initial Kjeldahl nitrogen content, and fixed and total nitrogen after ammoniation with an ammonia-air mixture. The values of these properties have shown hummocks and hollows to be true entities having characteristic ranges of certain properties. The results have shown that, although peat is heterogenous with respect to certain properties, use can still be made of determined values if ranges of these values are recognized and utilized. Misinterpretations and meaninglessness of results are possible if this is not done. / Thesis / Master of Science (MSc)

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.

Investigating the archaeology of submerged landscapes beneath many metres of sea and buried under modern sands requires an understanding of the terrestrial surface as it may have been prior to the inundation. To do this, environmental evidence is required from contextualised in-situ locations and the best material evidence for preservation of archaeology, organic remains, dating proxies, pollen, diatoms, microfossils, coleoptera etc. is peat. This research supports the search for peat in submarine environments by interpreting seismic surveys of the sub-sea floor and analysing reflective signals for distinctive organic responses. By means of sedimental analysis and ground observation, the research sets out to differentiate between organic signals, to allow for the identification and location of shallow peat beds within features of a palaeolandscape. Using these results should provide an opportunity to target such peat beds in an archaeologically focused coring programme. The research also examines ways in which organic responses may be mapped over larger areas in order to integrate the results into a wider scale landscape model identifying potential peatland, marsh, valley fen and lowland areas. Finally, the research introduces an artificial intelligence neural networking technology for the identification of organic interfaces in seismic surveys, examining three different ways in which this could be accomplished using specialist computer tools and software.

Som en följd av global uppvärmning blir det allt viktigare med resiliens mot klimatkrisens konsekvenser, däribland mer frekventa skogsbränder. Då våtmarker kan behålla vatten och ge resiliens mot torka och bränder är det intressant att undersöka relationen mellan våtmarker och skogsbränder. Syftet med detta arbete är att undersöka våtmarkers påverkan på skogsbränder i boreala skogsmiljöer, där frågeställningarna berör antändningsrisk, intensitet, brandskador, areell spridning och utdikning. Arbetet genomförs som litteraturstudie och GIS-analys med fokus på brandspridning. I GIS genomfördes först en multikriterieanalys och sedan en modellering av brandförlopp, i två områden i Hälsingland. Enligt analys och tolkning av resultat är fuktighet, grundvattennivå, vegetation, ytstruktur och storlek de viktigaste faktorerna i våtmarkers relation till skogsbränder. Sannolikhet för antändning, brandintensitet och brandskador minskar alla med ökad fuktighet, ökad grundvattennivå, gott om vitmossa och mindre av annan vegetation. Dessa faktorer gör även våtmarker till bättre brandbarriärer, speciellt i kombination med ökad storlek och heterogen ytstruktur. I motsats är våtmarker med lägre fuktighet och grundvattennivå, större bränsletillgång och träd sämre som barriärer mot skogsbrand och upplever intensivare bränder. Under extrem torka riskerar dock alla våtmarker, i olika utsträckning, att torka ut till den grad att bränder sprider sig över dem.GIS-analysen visar en koppling mellan sankmarker och områden med långsam brandspridning under normala förhållanden, och en stor lokal variation i förutsättningarna för brandspridning. Utdikning av våtmarker försämrar våtmarkernas resiliens mot skogsbränder, och skapar en risk för torvbränder, med allvarliga konsekvenser. En återvätning av utdikade våtmarker skulle förbättra deras brandresiliens. / As a result of global warming, it is ever more important with resilience towards the consequences of the climate crisis, including more frequent wildfires. Since wetlands can retain water and give resilience towards drought and fires, it is interesting to explore the relation between wetlands and wildfires. This study aims to research the influence of wetlands on wildfires in boreal forest environments, with research questions regarding risk of ignition, fire intensity, fire damage severity, areal spread and wetland drainage. The work consists of a literature review and GIS analysis focusing on fire spread. The GIS analysis is done through a multi-criteria analysis and afterwards a modeling of fire development, in two areas in Hälsingland, Sweden. According to analysis and interpretation of the result, the most important factors in the relation between wetlands and wildfires are moisture, water table level, vegetation, surface structure and wetland size. Probability of ignition, fire intensity and fire damage are all reduced with increased moisture, higher water table, plenty of sphagnum moss and less other vegetation. These factors also improve wetland efficiency as barriers against fire, especially in combination with increased size and a heterogeneous surface structure. On the contrary, wetlands with a lower moisture level and water table, larger fuel availability and trees function less efficiently as fire barriers and experience more intense fires. During extreme drought, however, all wetlands to a different extent risk drying out to the point where fire can spread over them. The GIS analysis displays a connection between fens and areas with slow fire propagation under normal conditions, as well as a large local variation in the factors influencing wildfire propagation. Wetland drainage deteriorates wetland resilience against wildfires, and creates a risk of peat fires, with severe consequences. Rewetting of drained wetlands would improve their fire resilience.

No description available.

Forested peatlands of the Great Dismal Swamp (GDS) have been greatly altered since colonial times, motivating recent restoration efforts. Community structure and function were hydrologically altered by 19th and 20th century ditches installed to lower water levels and enable early timber harvesting. Contemporary forest communities are comprised of maturing remnants from selective timber harvesting that ended in the early 1970s. Red maple (Acer rubrum) has become the dominant species across GDS, encroaching on or replacing the historical mosaic of cypress (Taxodium spp.)/tupelo (Nyssa spp.), Atlantic white-cedar (Chamaecyparis thyoides), and pocosin (Pinus spp.). Moreover, peat soil has been exposed to more unsaturated conditions resulting in carbon loss through decomposition and increased peat fire frequency and severity. Installation of ditch control structures aim to control drainage and re-establish historical hydrology, vegetation communities, peat accretion rates, and fire regime. To help inform restoration and management, we conducted two complimentary studies to test hypotheses regarding hydrologic influences on vegetation, peat depths, and peat fire vulnerability. First, we found thicker peat, lower maple importance, and higher species richness at wetter sites (e.g., higher mean water levels). In our second study, we evaluated the integrated effects of peat properties and water level dynamics on peat fire vulnerability. We found decreased burn vulnerability with increased wetness, suggesting that the driest sites were always at risk to burn, whereas the wettest sites never approached fire risk conditions. Together our findings demonstrate strong hydrologic controls on GDS ecosystem structure and function, thereby informing water level management for restoration goals. / Master of Science

The complexity of interactions that inform policy-making poses several challenges to evaluating the impact of policy research. Two key obstacles to policy-oriented research impact assessment (PORIA) are determining the degree of influence that can be claimed by a knowledge-generating entity and quantifying the impact of a policy-oriented research program. This thesis builds upon prior PORIA efforts to develop a framework for the evaluation of the impact of the Sustainable Wetlands Adaptation and Mitigation Program (SWAMP), an environmentally-focused, policy-oriented research project led by the Center for International Forestry Research (CIFOR). We examine a case study of the Indonesian Forest Moratorium policy to determine the policy's impact on emissions from peat deforestation. Results indicate that the policy has been largely ineffective in decreasing deforestation to date and has in fact been associated with increased deforestation above business-as-usual trends. Nevertheless, our analysis shows that if the moratorium were to achieve full protection, Indonesia could avoid the release of 10 - 20 million tons of carbon dioxide over the next 15 years, which corresponds to a mean social value of $402 - 805 million using a $40/ton social cost of carbon. With SWAMP's timely knowledge generation on tropical wetland carbon dynamics we estimate that $4.03 - 40.26 million of these social benefits can be attributed to CIFOR. Furthermore, through its involvement in the IPCC Wetlands Supplement and the Blue Carbon Initiative, SWAMP stands to positively influence outcomes of the 45 billion tons of carbon stored in non-Indonesian tropical peatlands and the global extent of mangroves, further increasing the impact of CIFOR. / Master of Science

Soilless substrates, such as peat, pine bark, and coir, are widely used as growing media in containerized crops for their favorable characteristics, including low bulk density, balanced air exchange and water retention, disease resistance, and low pH and salinity. However, improper irrigation of these media can have negative outcomes such as root asphyxia, pathogen development, and reduced plant growth. Understanding pore size distributions, water dynamics, and gas diffusivity of these substrates is essential to promote plant growth. The effects of different particle sizes of soilless media on processes such as infiltration, hydraulic conductivity, and gas diffusivity are also not well understood. The characterization of these effects is important for the overall improvement of container crop production. This thesis presents three studies that aimed to characterize the physical and hydraulic properties of pine bark substrates, both unamended and amended with peat or coir. The first study looked at three substrate types: unamended, unscreened pine bark, peat-amended pine bark, and coir amended pine bark. Three methods were employed to quantify pore distributions: non-equilibrium infiltration measurements, equilibrium water retention characterization, and scanning electron microscopy. We characterized pore distributions during wetting and drainage for the three substrates. Coir-amended bark had the largest water-conducting porosity, highest hydraulic conductivity, and most water retention. Unamended pine bark had the highest microporosity, and the addition of peat and coir lowered macroporosity, with peat having the greater effect. The total porosity inferred from the infiltration method was significantly smaller than that inferred from drainage experiments due to assumptions related to pore shape. The second study focused on defining hydraulic conductivity and water retention for pine bark substrates of five different particle sizes, <1 mm, 1-2 mm, 2-4 mm, 4-6 mm, and an unscreened fraction. We utilized the same methods from the first study. The resulting data showed that the smallest particle sizes (i.e., <1 mm and 1-2 mm) had the highest hydraulic conductivity and greatest water retention. The three larger sizes had lower hydraulic conductivity and poor water retention, including the unscreened fraction, which more closely followed the results of the 2-4 mm size. The final study examined gas diffusivity of the five pine bark particle sizes at different moisture levels: 60% moisture content (initial conditions), saturated at the bottom of the sample, near-saturated at the sample bottom, and drained from saturation to container capacity. We used a one-chamber gas diffusion setup to find gas diffusion coefficients (Ds). The results displayed an inverse relationship between Ds values and substrate water content. In addition, the larger particle sizes were less sensitive to changes in water content due to their well-draining large pores. Proper balance of aeration and water retention is necessary for the success of soilless growing media. Overall, the smaller particle size fractions had the best water retention and hydraulic conductivity rates while the larger fractions had the largest Ds coefficients. This work contributes valuable knowledge on the physical and hydraulic properties of different size fractions of pine bark substrates, which can assist nursery growers in optimizing water usage for sustainable container crop production. / Master of Science / Since the 1950's soilless substrates have been an important resource for growing a variety of fruits, vegetables, flowers, and ornamental plants. Soilless growing media have become more popular choices for containerized plant production compared to natural soils due to improved air exchange, increased disease resistance, and more plants per acre. They are also favored because they help conserve resources, reduce agricultural waste, and minimize transportation requirements as compared to traditional cropping methods. The most popular types of soilless media include peat, coir, compost, and pine bark. In the U.S., pine bark is the main substrate used, as it is renewable and widely available. Growers still face many issues when using containerized crop production. For example, pine bark is susceptible to water runoff which can cause environmental problems and increase costs from this loss of water and fertilizer. Further characterizing of water and gas dynamics in of pine bark growing media is important for conserving water and fertilizer resources while optimizing plant growth in this container cropping industry. Pore characteristics, aeration, and water movement are key factors of substrates to be described to solve these challenges. This project aimed to apply soil physics strategies to soilless media, focusing on describing pore sizes, water movement, water holding capacity, and air movement in pine bark substrates. We utilized three methods throughout this study. For the first method, we took infiltration measurements to examine how water moved into the media, while the second utilized controlled drainage experiments to observe how water moved out of the media. The final method was characterizing gas movement through the substrates at different water contents and particle sizes. The results found showed that the smaller particle sizes and pine bark mixed with peat and coir had increased ability to retain water and allow water movement as compared to the larger particle sizes and unamended pine bark. In contrast, the larger particles had less water retention but improved gas movement. These results could be applied by stacking different particle sizes or mixes over one another could optimize water retention in the top of the container and drainage and gas movement in the bottom of the container. Overall, the application of this work is to create best management practices for growers to be able to balance water retention and gas movement in order to optimize plant growth.

Peatlands are a diverse type of wetland ecosystem, characterized by high levels of soil organic matter, that provide a wide array of ecosystem services including water storage and filtration, carbon sequestration, and unique habitats. Draining peatlands degrades their resilience to future disturbances, notably including high intensity, soil-consuming fires. Peat soil fires are unique in that they can smolder vertically through the soil column, with consequences ranging from large carbon emissions to altered hydrology and dramatic shifts in vegetation communities. In this work we had two complementary objectives to understand both the drivers and impacts of smoldering fires at the Great Dismal Swamp (VA and NC, USA). First, we developed and verified a new method to model peat burn depths with readily available water level and peat hydraulic property data. Our findings suggest that drainage weakens both short- and long-term controls on peat burn depths by reducing soil moisture and by decreasing peat water holding capacity. To address the impacts of smoldering fires, we quantified the abundance of the noxious Phragmites australis in a large fire scar and the extent to which altered hydrology influenced its occurrence. We did so by leveraging satellite imagery, random forest models, LiDAR data, and water table observations. Our results suggest that P. australis is aided by a hydrologic regime generated, in part, from the combined effects of drainage and deep smoldering fires. Our conclusions from these two studies contribute to the scientific understanding of smoldering peat fires and can inform management efforts. / Master of Science / Peatlands are a diverse type of wetland ecosystem that have characteristically thick levels of organic-rich soil, known as peat. Peatlands are home to a variety of unique plants and animals, store large amounts of carbon, and provide water storage functions. Peatlands were historically drained to enable development and conversion to other land usages, which had many unintended consequences like increasing their risk to wildfires that consume soil organic matter. An intense peat fire can smolder down through the peat, with impacts ranging from large releases of carbon to changes in water levels and vegetation communities. In this work we had two objectives aimed at understanding the drivers and impacts of smoldering peat fires in the Great Dismal Swamp (GDS) (VA and NC, USA). First, we developed and verified a new method of modeling how deep peat fires burn by using readily available water level and soil property data. Our findings suggest that drainage weakens both the short- and long-term controls on peat fire burn depths by reducing soil moisture and by limiting the ability of peats to hold water. We also studied how water levels in a post-peat consuming fire environment influence the amount of the weedy Phragmites australis. We did so by using satellite imagery, elevation data, and water table observations. Results from this investigation suggest that the combined effects of drainage and deep smoldering fires help to create ideal conditions for P. australis invasion and establishment. Our findings from these two studies add to the scientific understanding of smoldering peat fires and may inform land management decisions.