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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Le Polytrichum strictum comme stabilisateur de substrat et plante compagne pour les sphaignes dans la restauration des tourbières exploitées par aspirateur /

Groeneveld, Elisabeth. January 2002 (has links) (PDF)
Thesis (M. Sc.)--Université Laval, 2002. / "Fevrier 2002." Includes bibliographical references. Downloaded and printed from Laval University website.
2

Paleoecological and Carbon Accumulation Dynamics of a Fen Peatland in the Hudson Bay Lowlands, Northern Ontario, from the Mid-Holocene to Present

O'Reilly, Benjamin Cody 15 December 2011 (has links)
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.
3

Paleoecological and Carbon Accumulation Dynamics of a Fen Peatland in the Hudson Bay Lowlands, Northern Ontario, from the Mid-Holocene to Present

O'Reilly, Benjamin Cody 15 December 2011 (has links)
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.
4

An Evaluation of Restoration Techniques for a Small Scale All-Terrain-Vehicle Disturbance in the Lake Charlotte Peatland

Mason, Rebecca 29 July 2010 (has links)
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.
5

On developing an unambiguous peatland classification using fusion of IKONOS and LiDAR DEM terrain derivatives – Victor Project, James Bay Lowlands

DiFebo, Antonio January 2011 (has links)
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.
6

Calibration of phenol oxidase measurement in acidic wetland environments

Chanton, Patrick 27 August 2014 (has links)
Phenol oxidases mediate the degradation of recalcitrant compounds, polyphenolics, in wetland soils and are considered to play a key role in the microbial carbon cycle of peatlands which predominate in boreal biomes. In order to validate a method for quantification of oxidative enzyme activity in acidic wetland environments, the relationship between pH and substrate oxidation was studied using the standard enzyme tyrosinase and in soils collected from six freshwater wetlands including three marshes in north Florida and peatlands of northern Minnesota. Phenol oxidase (PO) activity was quantified with two commonly used assay substrates, ABTS (2,2'-azino-bis(3-ethylobenzthiazoline-6-sulfonic acid) and L-DOPA (L-3,4-dihydroxyphenylalanine), across a pH range of 4 to 7 which matched the in situ pH range of the studied wetlands. The PO assay is sensitive and activity could be detected with either substrate across a pH range of 4 to 7. However, with the standard enzyme tyrosinase, it was shown that a large change or threshold in oxidation rates occurred at pH 5. At pH < 5, L-DOPA oxidation rates were greatly diminished and ABTS oxidation was at a maximum. Above pH 5, ABTS oxidation occurred at much slower rates and L-DOPA oxidation was at a maximum. The pH response of PO activity in wetland soils corroborated observations made with tyrosinase. Thus, ABTS is recommended to be an effective substrate for the quantification of PO activity at an in situ pH of < 5, while L-DOPA is recommended at an in situ pH of > 5. In soils collected from a northern Minnesota peatland, assays conducted at an in situ pH of 4 showed one to two orders of magnitude higher rates of PO activity in solid phase peat in comparison to porewater, indicating that the majority of PO activity is associated with the peat. At three Minnesota peatland sites, PO activity was shown to attenuate with depth in agreement with the activities of other enzymes and with rates of peat decomposition.
7

Surface oscillation in peatlands: How variable and important is it?

Fritz, Christian January 2006 (has links)
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.
8

Vegetation regeneration in the cut-over lowland raised mires of Northern Ireland

Smith, David M. January 1998 (has links)
No description available.
9

On developing an unambiguous peatland classification using fusion of IKONOS and LiDAR DEM terrain derivatives – Victor Project, James Bay Lowlands

DiFebo, Antonio January 2011 (has links)
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.
10

Habitat relationships of bird communities in Wisconsin peatlands /

Zolkowski, Stephanie B. January 2008 (has links) (PDF)
Thesis (M.S.)--University of Wisconsin--Stevens Point, 2008. / Includes bibliographical references.

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