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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.
21

Colonization of restored peatlands by insects : Diptera assemblages in mined and restored bogs in eastern Canada

Grégoire Taillefer, Amélie. January 2007 (has links)
The impact of peatland restoration on Diptera assemblages was studied across multiple organizational levels (taxon, size class, trophic group) among abandoned-mined, restored and natural sites of three bogs and the environmental variables affecting those assemblages were determined. More than 22,000 individuals representing 716 species were collected using pan traps, sweeping and Malaise traps. Restored and abandoned sites were similar to each other and both distinct from natural sites as shown by small-size class, acalyptrate and trophic assemblages. However, abandoned sites showed much lower evenness and generally supported lower species richness than restored and natural sites, due to the dominance of one or two saprophagous species. The coverage of bare peat, Sphagnum mosses and ericaceous shrubs explained most of the variance in species composition. Those results suggest that restoration enhanced the recovery of high species diversity, although more than seven years are needed to recover a complete trophic structure or to enable species with low dispersal ability to recolonize to pre-disturbance levels.
22

Revitalizace vybrané lokality rašeliniště s ukončenou těžbou / Revitalization of selected sites of excavated peat bogs

JANÁK, Bohumil January 2017 (has links)
Roast moorland one of the unique South Bohemian habitats. Currently, these sites are protected by law and they paid great attention to the media and professional - the general public. Local unique biodiversity is linked to hydrological conditions in the area, they live here rare species of animals and unique diverse plant communities. Despite this fact, a large part of the area previously used for peat extraction. These interventions, however, fundamentally not damage the local area and biological processes. That all changed beginning of the industrial peat extraction, where a large part of the territory forcibly drained, and cut down massively damaged by subsequent mining. Drainage of land degradation brought about significant changes in the local flor, faun and peat. After mining was part of the territory of unprofessional revitalized using improper procedures and are non-native plants such as: Giant cage and others. Since 1998 in this and surrounding areas held a program to rescue these unique habitats revitalization of Šumava wetlands and peatlands. Its main aim is to rescue the damaged wetlands and marshes, groundwater and increase the overall improvement of the water regime in the landscape. This program could involve the general public.
23

Atmospheric mercury deposition and mercury stable isotope compositions in peat bogs. / Les isotopes stables du mercure dans les tourbières comme outil de compréhension des dépôts atmosphériques actuels et passés sur les surfaces continentales

Enrico, Maxime 25 September 2015 (has links)
Les tourbières sont communément utilisées comme archives de dépôts de mercure (Hg). De nombreuses études ces dernières décennies ont montré que les taux d’accumulation de Hg (HgARs) ont augmenté en réponse à l’industrialisation. Les signatures isotopiques en Hg se révèlent très utiles pour mieux caractériser les dépôts de Hg. Elles ont permis de montrer que les dépôts secs de Hg élémentaire gazeux (GEM) dominent les dépôts de Hg sur la tourbière du Pinet. L’analyse d’échantillons de tourbe provenant de plusieurs tourbières en hémisphère nord montre que les dépôts secs de GEM dominent globalement les dépôts de Hg. Les tourbières pourraient donc être utilisées comme archives à la fois des dépôts humides et des concentrations en GEM pendant l’Holocène. On présente la première reconstruction quantitative des concentrations passées en GEM à partir de carottes de tourbe. L’impact de l’Homme sur le cycle du Hg a eu pour conséquence une augmentation graduelle des concentrations en GEM de 0,2 (10 000 – 4000 BP) à 3,5 ng m-3 (20ème siècle), accompagnée par des modifications de signatures isotopiques du Hg atmosphérique. Cette première utilisation de tourbières comme archives de concentration et d’isotopie du GEM est prometteuse, et devrait être étendue à la période pré-anthropique pour étudier les variations naturelles du cycle du Hg pendant l’Holocène. / During the past few decades, peatlands were successfully used to investigate historical mercury (Hg) deposition. The chronology of Hg accumulation rates (HgARs) to peatlands is well constrained, with recent increases in HgAR associated with anthropogenic Hg emissions and deposition. The use of Hg stable isotopes in peatland ecosystems provides new opportunities to better characterize and understand historical Hg deposition. In an extensive study conducted at the Pinet peat bog (French Pyrenees) we identify gaseous elemental Hg (GEM) dry deposition, via foliar uptake, as the dominant Hg transfer pathway from the atmosphere to peat vegetation. Based on the Hg isotope analysis of multiple northern hemispheric peat records, we find that GEM dry deposition dominates Hg deposition globally. We suggest that peatlands can be used as archives of both past Hg wet deposition, Hg dry deposition and GEM concentration. We present the first quantitative reconstruction of historical atmospheric GEM concentrations using peat archives from the Pyrenees. The Human impact on Hg cycling caused a gradual increase in GEM concentrations from 0.2 (10,000 – 4000 BP) to 3.5 ng m-3 (20th Century) and was accompanied by a change in atmospheric Hg isotope signatures. This first comprehensive study on Hg isotope deposition to peatlands is promising and should be extended to pre-anthropogenic times to investigate natural variations in atmospheric Hg dynamics during the Holocene.
24

The hydrology and dissolved organic carbon (DOC) biogeochemistry in a boreal peatland /

Fraser, Colin J. D. January 1999 (has links)
No description available.
25

Colonization of restored peatlands by insects : Diptera assemblages in mined and restored bogs in eastern Canada

Grégoire Taillefer, Amélie. January 2007 (has links)
No description available.
26

Carbon biogeochemistry of open water pools on an ombrotrophic raised bog, James Bay, Québec, Canada

McEnroe, Nicola A., 1973- January 2008 (has links)
Carbon (C) biogeochemical cycling studies in northern peatlands, in particular the production, consumption, storage and emission of C gases (CO2 and CH4) over space and time between different peatland landforms can help in understanding their current and future role in the global C cycle. In some peatlands, a distinct surface patterning of vegetation, interspersed with open water pools, controls the spatial and temporal variability in CO 2 and CH4 exchange to atmosphere. These open water pools initially develop from shallow, flooded hollows to deeper water bodies and at some point reach a limit in their depth. Observations link pool size to age and spatial location on the peatland surface and over time the proportional cover of pools increases, playing an important role in the long-term peatland C balance. / The processes responsible for the production of CO2 and CH 4 in pools remain unexplored. In particular, the contribution of pools to the peatland C balance over the timeframe of the development of a pool complex is not explained and pools are not incorporated into current peatland models. A field study was carried out to examine the exchange of CO2 and CH4 from pools to atmosphere and to explore the spatial and temporal dynamics in CO2, CH4 and DOC storage in pools of different size and spatial location. This was undertaken to improve the understanding of the processes responsible for the generation of CO 2 and CH4 over the timescale of pool development. The empirical study was carried out during spring, summer and fall over two years in an ombrotrophic, raised bog, Quebec, Canada. A modelling component was carried out to examine the contribution of pools to the long-term peatland C balance. / Measurements of dissolved concentrations and emissions of CO2 and CH4 from pool surfaces to atmosphere were different among pools of different sizes and spatial location. Shallow pools had consistently higher emissions of both CO2 and CH4 and higher water column dissolved CO2 and DOC concentrations. Deeper pools had greater concentrations of sediment CH4. Dissolved organic carbon in pools was allochthonous, with a greater concentrations and proportion from higher plant materials in shallow pools, likely contributing to the observed water column CO2 concentrations and greater CO2 emissions. / All pools were supersaturated with dissolved CO2 and CH 4 at the time of sampling, with shallow pools up to eight times atmospheric equilibrium concentrations for CO2 and concentrations were up to one hundred times greater than CH4, comparable to findings in other global freshwater systems. Results suggest that greater decomposition is occurring in shallow pools due to warmer water and basal sediment temperatures and increased light penetration and dissolved oxygen (00) and that greater CH4 production and oxidation accounts for some of the differences reaching a limit at 0.7 m deep. Even though this range of pools are not as deep as pools found on other northern peatlands, the results provide evidence for the potential processes responsible for the generation of CO2 and CH4 emissions to atmosphere and demonstrate that pools have a significant role in the short and long-term peatland C balance. Modelling the hypothesised processes responsible for the generation of CO2 and CH4 shows that if sediment decomposition is the major source of these gases then the dynamical link between pool sediments, C gas production and pool growth has been demonstrated. Ultimately their role as source or sink is largely determined by their size (depth), the proportional cover on the landscape and their rates of C storage in sediments versus rates of C uptake and exchange.
27

Carbon biogeochemistry of open water pools on an ombrotrophic raised bog, James Bay, Québec, Canada

McEnroe, Nicola A., 1973- January 2008 (has links)
No description available.
28

Hochmoore im Erzgebirge - Untersuchungen zum Zustand und Stoffaustragsverhalten unterschiedlich degradierter Flächen / Peat bogs in the mountains "Erzgebirge" - investigations of state and output of dissolved substances from differently degraded areas

Böhm, Anna Katharina 14 December 2006 (has links) (PDF)
Die Hochmoore des Erzgebirges sind auf Grund ihrer jahrhunderte langen Nutzung und der ökosystemaren Wandelprozesse der vergangenen 10 - 15 Jahre unterschiedlich stark degradiert. Gleichzeitig sind sie durch den Austrag vergleichsweise hoher Austräge von DOC (Dissoloved Organic Carbon) gekennzeichnet. Um den Zusammenhang zwischen dem Zustand der Hochmoore, als Ergebnis in erster Linie der unterschiedlich nutzungsbedingten Degradation und den Stoffausträgen speziell den DOC-Austrägen zu erfassen, wurden mittels landschaftsökologischer Methoden Hochmoortestflächen verschiedener Zustände vergleichend untersucht. Die Ergebnisse lieferten erste Hinweise, dass in Flächen mit natürlicher Regeneration oder anthropogener Wiedervernässung vergleichsweise hohe DOC-Konzentrationen und – Austräge zu beobachten waren. Demgegenüber standen stärker degradierte Flächen mit zum Teil aktueller forstlicher Nutzung (geräumte Entwässerungsgräben), die durch geringere DOC-Konzentrationen und – Austräge charakterisiert waren. Da die gefundenen Zusammenhänge nicht endgültig belegt werden konnten, besteht insbesondere Forschungsbedarf hinsichtlich landschaftshaushaltlicher Untersuchungen unterschiedlich degradierter Hochmoore im Erzgebirge. / Natural peat bogs are known as a sinks especially for carbon because of theire special matter and water balance. The use of peat bogs requiers their drainage, but consequently the peat will decompose unreversible and peatlands turn to a source esspecially for carbon. The peat bogs in the “Erzgebirge Mountains” were used over several centuries. Thats why the peatlands existing nowadays have different states dependent on the duratian of their use. Beside the use peatlands were mostly negativly effected by processes of ecological change in the “Erzgebirge Maountains” in the last 10 to 15 years. As one result of ecological change the increased output of DOC (Dissolved Organic Carbon) into surface waters can be seen. The main source for DOC are peatlands. By the way it seems to exist a connection between the output of DOC and other dissolved substances and the state of the peatlands especially of their ditches. To research this hypothesis four test areas of different state were chosen. Their state and the output of DOC and other dissolved substances were investigated with methods from landscape ecology from 2001-2003. It was the first time, that peatlands in the “Erzgebirge Mountains” were investigated in such a way. The badest state had the test area where the ditches were cleaned in 2000/ 2001 (“Weiße Mulde”, Western “Erzgebirge Mountains”). This test area showed the lowest but constant DOC-concentrations and DOC-output during the investigation period. The test areas “Carlsfeld” and “Löffelsbach” (Western “Erzgebirge Mountains”) had the best state. The state of “Carlsfeld” is related to the narueal closed ditches, which cause the processes of self regeneration. Due to such processes the DOCconcentrations were distinctly higher but very variable in dependence on weather and runoff. The same was supposed to DOC-output. The same valuation got the test area “Löffelsbach”, because of rewetting by technical closed ditches in 2001. During the investigation period the highest DOC-concentrations of all test areas were measured there. Similar to “Carlsfeld” DOC-concentrations and –output were highly variable in dependence on weather and runoff. The state of the test area “Salzflüßchen” (Eastern “Erzgebirge Mountains”) is also related to processes of self regeneration but was valuated bader than “Carlsfeld”, because the effect of former drainage was stronger in this area. In 2005 the rewetting of the test area is planed by “Naturpark Erzgebirge/ Vogtland”. In the consequence the DOC-concentrations and –output will increase similar to “Löffelsbach”. The results of the investigations indicate that a connection exists between state of peatlands and output of dissolved substances esspecially DOC. The results are supported by national and international literature. It will be clear, that more research is necessary especially on the field of comparative investigations of peatlands with different states in the “Erzgebirge Mountains”.
29

Vývoj a perspektivy návštěvnosti Chalupské a Jezerní slatě (NP Šumava) / Development end perspectives of attendance of two peat bogs (Chalupská a Jezerní slať) in Šumava National Park

DUTKA, Ladislav January 2013 (has links)
Peat bogs of the Šumava National Park are very valuable biotopes with an occurrence of the specific flora and fauna, including glacial relicts. These localities are also very attractive for tourists, so it is important to find the reasonable compromise between an attendance and a nature protection. The study is dealing with the development of touristic attendance of two peat bogs from 2010 to 2012 and enlarges my bachelor?s work (Comparison of attendance of two peat bogs (Chalupská a Jezerní slať) in Šumava National Park). The work is divided into two parts. The first, theoretical part, includes a literary review about the character of the Šumava?s peat bogs and the tourism in those localities. A practical part monitors the attendance of the peat bogs and analyses the research via questionnaire, focused on the specifics of the tourists, their priorities during visit of the peat bogs and transport to those localities. The research was connected to bachelor?s work ? there were also 5 terms of field monitoring, the dates in 2012 were close to the dates in 2010 and the number of the panelled questionnaires was the same, 200. So the results of both years could be easily compared. It was found that the number of peat bogs? visitors increases. There were 1438 visitors on Jezerní slať and 1106 on Chalupská slat peat bog. Jezerní slať was more visited than Chalupská slať in both 2010 and 2012. Most of the visitors came by bicycle, but the number of visitors who came by bus was increased. Huge increase was found in number of dogs, which was really surprising. The visitors of Jezerní slať more often stayed in camping sites than in 2010. The problem of possible development and perspectives of investigated peat bogs is also outlined in the end of the work.
30

Rozšíření, diverzita a ekologie bentických krásivek na lokálním prostorovém měřítku / Distribution, diversity and ecology of benthic desmids along local spatial scale

Svoboda, Pavel January 2012 (has links)
Besides spatial heterogeneity, an important component of diversity of the protist communities is also the variation in species assemblages through time (temporal turnover). Spatial and temporal variation in patterns of distribution and abundance of lentic microphytobenthos assemblages is often large and occurs at relatively small spatial scale. Desmids (Zygnematophyceae) often constitute a characteristic part of the microphytobenthos of peat bogs. Despite their important role in primary production and fact that they are useful indicators of ecosystem uniqueness, investigations of their seasonality and spatial distribution are scarce. In my thesis I have investigated if desmid epipelic communities are driven rather by neutral or niche-based processes, and I also focused on the factors affecting their diversity, seasonal dynamics and spatial patterns at the local spatial scale. The study was conducted at the two different types of biotopes - minerotrophic lowland peat bogs (Doksy region) and ombrotrophic raised bogs (Jizera Mountains region). Seasonal changes in species composition and diversity of assemblages were not evident. This may be affected by a monopolization effect and also that local abundance of species was positively correlated with population persistence, which suggests that high local...

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