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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.
31

Hochmoore im Erzgebirge - Untersuchungen zum Zustand und Stoffaustragsverhalten unterschiedlich degradierter Flächen

Böhm, Anna Katharina 24 February 2006 (has links)
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”.
32

Optimization of Physical Properties for Ditches–Case Study: Kankberg, Maurliden and Renström-Petiknäs.

Ketema, Ghebriel Kidane January 2014 (has links)
It is important for practical and legal reasons that water and sediments in disturbed areas around the mining operation should be controlled. The construction of a well-designed drainage system that controls erosion and thus restores the proper hydraulic function of the surface is one of the most important post-disturbance features which should be done as part of the mining activities. However, even with the best planning and design, unless proper construction practices are adapted; both the disturbed and reclaimed areas are very much likely to be susceptible to erosion, sedimentation and stability problems. In order to tackle the problem, guidelines on how to design and construct the drainage system should be well prepared. The main objective of this study was to prepare guidelines for the proper design, construction and monitoring of the water drainage management system in the study areas (Kankberg, Maurliden and Renström-Petiknäs). This report has analysed the results from the outcome of HEC-RAS software for the case study of the new ditch around the Maurliden mine site and integrated with different guidelines. Based on the results of the HEC-RAS, the most common problems in the drainage system have been identified. Moreover the thesis project identified important physical parameters such as cross-sections and slopes of the representative ditch which affect the function of the ditch in the study areas. Hydraulic parameters such as velocity which is very important for designing the type of lining and also Froude number which is very important in identifying the type of flow whether it is super-critical, critical or sub-critical were identified. The latter helps to select the type of guideline to be used between steep slope and mild slope.
33

Wetland Habitat Use by Semiaquatic Fauna in a Hydromodified and Fragmented Landscape

Britton, Sean Michael 19 December 2022 (has links)
No description available.
34

Subsidence Damage in Southern Arizona

McCauley, Charles A., Gum, Russell L. 06 May 1972 (has links)
From the Proceedings of the 1972 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 5-6, 1972, Prescott, Arizona / Land is subsiding over a heavily mined aquifer in south central Arizona. Subsidence damages are inventoried to help provide a basis upon which cost studies can be performed to determine actions to lessen the economic impact of these damages. Water table drawdown produces increasing loading stress by three ways: changes in bouyant support of aquifer grains, changes in water table, or both. Two types of subsidence are recognized--one-directional compression, and near surface phenomenon. Damages due to natural structures, and to man-made structures are reviewed. Agricultural damages include field releveling, ditch repair and well damage. Damages to transportational facilities include highways, bridges, pipelines, and railroads. Damages to domestic and urban structures are suggested. Questionnaires, interviews and on-site inspections were used to collect information on land subsidence damages in the study area.
35

Perspectives on the Geomorphic Evolution and Ecology of Modified Channels and Two-Stage Ditches in the Agriculturally-Dominated Midwestern United States

D'Ambrosio, Jessica Leigh 20 May 2013 (has links)
No description available.
36

Population dynamics of hybrid ecosystems: Implications for marginal ecosystem conservation and management

Nichter, Ashlee N. 29 November 2017 (has links)
No description available.
37

Mécanismes de propagation du roseau commun envahisseur au Québec

Albert, Arnaud 01 1900 (has links)
No description available.
38

Drobní zemní savci podél přirozených a antropogenních krajinných bariér / Small terrestrial mammals along natural and anthropogenic landscape barriers

BOHDAL, Tomáš January 2011 (has links)
The dissertation summarises the result of the study of small terrestrial mammals (Eulipotyphla, Rodentia) along natural (watercourses) and anthropogenic (road, highway) landscape barriers. It points to an interesting phenomenon of road drainage ditches as a transitional migration environment, further it assesses the level of locomotion activity, the rate of structure of subpopulations and the frequency of crossing watercourses in the case of selected rodent species. It contributes with its results to solving problems concerning the effect of these landscape structures on the species diversity, ground mobility or genetic structure of small terrestrial mammals. ˙˙˙˙

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