Abgeschlossene Dissertationen
Microplastics in limnic ecosystems – Identification of sources and sinks in the model catchment of Lake
Tollense, Germany
Tamminga, Matthias
Betreuung durch: Prof. Dr. Jürgen Böhner und Dr. Elke Fischer
Freshwater systems have been underrepresented in microplastic research compared to the marine environment so far. Though, they have to be attributed high relevance due to the function of streams and rivers as important input vectors for terrestrial microplastics and the yet not fully clarified role of lakes as potential sinks on varying time-scales. Moreover, lakes are particularly appropriate as a research subject, as they allow budgeting approaches due to their semi-closed character accompanied by reduced complexity. The
Lake Tollense catchment (Mecklenburg-Western Pomerania) is a model example in this regard. The lakes shape, its exposure within the landscape, strong gradients concerning human activities and the polarized allocation of its tributaries and discharge enable the investigation of sources and driving factors for microplastic pollution in freshwater ecosystems. To achieve this, a second major research need has to be addressed: The harmonization of methodical approaches along the complete process chain beginning with sampling-concepts (specifically for particles smaller manta mesh-size) and ending with the identification respectively characterization of microplastic particles found.
This project aims to contribute to both the aims by (1) developing a sampling-strategy, which closes the knowledge gap for particles below the mesh-size of common trawling approaches, (2) setting up a digestion protocol suitable for the analysis of all ecosystem compartments, (3) using a microplastic identification approach that allows the processing of large sample numbers (e.g. Nile Red staining combined with subsample micro-Raman-spectroscopy) and finally (4) including a set of compartments, namely surface waters, the water column, tributaries and discharges as well as treated and untreated waste waters into the analysis.
Macro- and microplastic pollution in limnic sediments
Hengstmann, Elena
Betreuung durch: Prof. Dr. Jürgen Böhner und Dr. Elke Fischer
Scientific research of recent decades has increasingly focused on the pollution of aquatic ecosystems by plastics. The quantification of macro- and microplastics in limnic ecosystems is at the forefront of this PhD project, which takes the example of Lake Tollensesee in
Mecklenburg-Western Pomerania. Due to its size, sufficient water depth, distribution of use intensities well as morphological aspects and access to bank border sediments, it offers almost ideal conditions for a comprehensive macro- and microplastic study.
By answering the guiding question "What is the abundance of macro- and microplastics in sediments of Lake Tollensee?", the environmental plastic load of the lake ecosystem can be better assessed. The question of the (intermediate) storage of microplastics in limnic basins is another main focus of the work. During the transport of microplastic particles through the
water network, limnic basins could function as, at least, temporary sinks. Broader knowledge on this topic is necessary in order to identify reliable statements about basic mechanisms of microplastic dynamics. Since the weathering of larger plastic parts leads to the formation of (secondary) microplastics, the simultaneous consideration of macroplastic pollution is indispensable.
For the determination of micro- and macroplastics in the bank border zone, one representative beach section per exposition, which is mainly characterized by a sandy substrate, is investigated. Possible differences in the distribution of plastic depending on the
use of these sections can thus be detected. Sediments from the bottom of the lake are also integrated into the analysis. Sampling takes place every six months in order to answer the question of potential seasonal variations in micro- and macroplastic pollution.
Modelling Environmental and Social Impacts of Bioenergy from Oil Palm Cultivation in Nigerian Niger Delta.
Okoro, Stanley
Betreuung durch: Prof. Dr. Udo Schickhoff
Projektbeschreibung:
The increasing demand for bioenergy due to its climate mitigation ability has been promoting the expansion of a number of agricultural commodities; this includes oil palm (Elaeis guineensis).The commercial cultivation of oil palms and other bioenergy crops has been leading to competition with food and environmental degradation, causing one of the major issues confronting many governments around the world. This problem has been acute especially in developing countries where there is often a lack of understanding of environmental and societal interactions with respect to land use issues. My project is aimed to employ the integration of Remote Sensing, GIS and Constraint Optimization Modelling approach with the view to evaluate the environmental and social impacts of bioenergy production from oil palm cultivation on the Nigerian Niger Delta environment.
Pastoral Resources in the Naryn Area, Kyrgyz Republic, under Post-Socialist Transformation - Analysis, Monitoring and Forecasting
Hoppe, Franziska
Betreuung durch: Prof. Dr. Udo Schickhoff
Projektbeschreibung:
Animal husbandry in mountainous regions has always played a major role in the life of Kyrgyz people and the livestock sector has been one of the strongest components of the regional economy during Soviet and post-Soviet times.Montane and alpine rangelands, which occupy 45% of the Kyrgyzstan’s land area, represent the significant basis for this economic sector. During the Soviet regime the livestock industry had been massively expanded. The first years after independence saw, a drastic reduction in livestock numbers, and a temporarily decreasing grazing pressure. However, in the further course of post-Soviet transformation livestock numbers have been considerably increasing again. By current estimates, at least 25-35 % of pasture areas are subject of vegetation and soil degradation. Using an interdisciplinary approach, the project TRANSPAST aims at assessing the capability of rangeland ecosystems to cope with increased grazing pressure, and at predicting the future pastoral resource availability under different land use scenarios. Based on collected data in the field, as well as their evaluation and including socio-economic aspects, a comprehensive understanding of human-environment interactions will be developed. In addition the project intends to predict the future pastoral resource availability under different land use scenarios, and to provide management suggestions.
Statistical Downscaling of precipitation in Amazonia
Kawohl, Tobias
Betreuung durch: Prof. Dr. Jürgen Böhner
Projektbeschreibung:
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Sensitivity of treeline at Rolwaling Himal to global warming – Analyses of vegetation and regeneration processes
Bürzle, Birgit
Betreuung durch: Prof. Dr. Udo Schickhoff
Projektbeschreibung:
Climate warming is expected to induce treelines to advance to higher elevations since, at a global scale, low-temperature growth limitation determines the position of natural alpine treelines. On a regional and local scale, however, treeline position, form (spatially pattern), and dynamics depend on multiple interactions of influencing factors and mechanisms. Thus empirical studies give evidence of both advancing treelines as well as rather insignificant responses. This inconsistency of findings is not well understood and pointing to considerable research deficits, concerning the effects of global and local factors. Furthermore, past treeline studies mainly focused on the response of mature trees (e.g. growth, growth form) to climate warming. Since treeline advance particularly depends on successful dispersal of seeds and the survival of young seedlings, future assessments have in particular to consider the response of pre-established life stages to climate warming.
Integrating field sampling/mapping and experimental treatments, the PhD project aims at investigating the sensitivity and response of the treeline ecotone in Rolwaling Himal, Nepal, to climate warming. Focusing on tree recruitment and regeneration processes, treeline response will be analysed by correlating patterns of naturally established seedlings with microhabitat conditions and mechanisms (e.g. plant interactions associated with facilitation, competition, feedback systems, shelter elements). In order to explore the future potential for climate change-induced treeline advance, regeneration analyses will be complemented by an experimental approach using open top chambers (OTCs).
Modelling changing distribution ranges of Himalayan plant species under climate change conditions
Bobrowski, Maria
Betreuung durch: Prof. Dr. Udo Schickhoff
Projektbeschreibung:
Global warming and other global environmental changes (e.g. habitat loss and fragmentation, accumulation of nutrients and pollutants, biological invasions) are increasingly threatening biodiversity and ecosystem services. Due to above-average warming rates high latitude and high altitude regions are particularly susceptible to climate warming effects. Recent observational, experimental and modelling work has pointed to major changes in arctic and montane ecosystems as a result of climate change. Significant changes in the distribution of species and ecosystems have to be expected. A number of different modelling approaches has been developed such as Maxent and BIOMOD, forecasting future species distributions under climate change conditions. Hitherto published results of respective modelling studies primarily refer to plant species and communities of the European Alps. For the Himalayan mountain range, species or habitat distribution modelling studies have not been conducted so far. It is therefore the objective of this thesis to investigate how and to what extent Himalayan plant species distribution ranges may change or shift under climate change conditions. In order to predict future distribution ranges, species distribution modelling will be applied based on geocoded information on current species distributions and quantified environmental niches of species.
Treeline dynamics at Rolwaling Himal
Schwab, Niels
Betreuer: Prof. Dr. Udo Schickhoff
Projektbeschreibung:
While at global scale plant growth limitation by low-temperature determines the position of natural alpine treelines, at smaller scales the factors and mechanisms influencing treeline characteristics are not well understood. Main objective of the project TREELINE is to detect the hitherto poorly understood driving forces for spatially differentiated treeline dynamics. As our study area, the secluded Rolwaling valley provides one of the rare near-natural Himalayan treelines with negligible human impact.
Forest ecological and dendroecological data and their analyses’ results will be this work’s contribution to TREELINE’s integrated landscape approach model. Appropriate forest and vegetation sampling methods will be applied at Rolwaling during extensive field campaigns. Open source GIS and statistics software (SAGA-GIS, R) will be used to elaborate and visualize results. Major tasks are to investigate age structure of stands and annual radial increment of trees for changes, with the aim of describing treeline dynamics at different positions of the valley’s slopes. Increments will be tested for correlation with data from high resolution climate modelling (see projects of E. Rauch and L. Gerlitz, both Hamburg). Moreover the spatial effectiveness of other relevant abiotic and biotic site factors, e.g. soil conditions and ground vegetation (see projects of M. Müller, Tübingen and B. Bürzle, Hamburg), will be analysed to explain spatially non-uniform treeline response patterns.
Future Climate Change and Urbanization Impact on Coastal Strom Surge Risk in the Pearl River Delta Region, China
Li, Li (2016)
Betreuer: Prof. Dr. Jürgen Böhner, Prof. Dr. Gabriele Gönnert (LSBG Hamburg)
Laufzeit: 2011-2016
Development and implementation of GIS-based methods for the assessment of meso-scale climate change impacts in sub-Saharan Africa, with special reference to the Okavango catchment
Weinzierl, Thomas (2015)
Betreuer: Prof. Dr. Jürgen Böhner, Prof. Dr. Udo Schickhoff
Laufzeit: 2011-2015
Assessment of High Resolution Climate Data for the Tibetan Plateau and the Himalayan Arc - New Approaches in Statistical Downscaling
Gerlitz, Lars (2014)
Projektwebsite: TREELINE, CLASH
Betreuer: PD. Dr. Axel Thomas (Universität Mainz), Prof. Dr. Jürgen Böhner
Laufzeit: 2011-2014
Climate impact studies often require precise and spatially high resolution climate data. However the spatial heterogeneity in high-mountain regions is not sufficiently captured by state-of-the-art climate reanalysis products due to their limited spatial resolution. With the aim of assessing near surface climate parameters for the Tibetan Plateau and the adjacent mountain ranges with high spatial and temporal resolution, the PhD-thesis presents a statistically modeling framework, basically integrating statistical downscaling and GIS based climate spatialization routines. Digital elevation models and their derivates were integrated into statistical downscaling models in order to represent specific topoclimatic processes. Different machine learning and data mining approaches were applied to develop robust transfer fuctions. The final statistical model allows the analysis of topoclimatic processes under varying synoptic conditions and facilitates the generation of high resolution climate estimates as required by climate impact studies.
Rangeland Degradation and Rehabilitation in the Succulent Karoo, South Africa
Dipl. Ing. (FH) Wiebke Hanke (2013)
Landschaftsnutzung/Naturschutz
Betreuer: Prof. Dr. Jürgen Böhner und Prof. Dr. Norbert Jürgens
Laufzeit: 2010-2012
Rangeland degradation within arid environments due to unsustainable livestock production threatens livelihoods of people and biodiversity worldwide. The global biodiversity hot spot of the Succulent Karoo biome in South Africa has been no exception. In the framework of BIOTA Southern Africa, therefore, a restoration experiment was established in the Richtersveld region. The aim of this project is to understand degradation processes and to identify effective rehabilitation techniques for this area.
Remote sensing of urban canopy parameters for enhanced modeling and climate related classification of urban structures
Bechtel, Benjamin (2013)
Projektwebsite: Urban Climate: Work Package I
Betreuer: Prof. Dr. Jürgen Böhner und Prof. Dr. Jürgen Oßenbrügge
Laufzeit: 2008-2011
The first work package aims to contribute to an improved understanding of microclimatic influences of the heterogeneous urban land-use and morphology. We intend to develop and implement state of the art methods to analyse the local energy balance by specific spectral response pattern of the modelling domain on different synoptic conditions. Secondly a set of extensive climate relevant urban surface parameters will be developed which includes spectral features, land cover, geometric/morphologic features and advanced anisotropic parameterisations of the urban canopy energy balance as well as urban roughness. Those parameters shall give a better representation of micro climate relevant city morphology and thus allows to a certain extent explanation of the spatial variation within urban climate.
The Impact of the Transformation Process on Humanenvironmental Interactions in Souther Kyrgyzstan
Dipl.-Biol. Peter Borchardt (2013)
Projektwebsite: kirgistan.uni-hamburg.de
Betreuer: Prof. Dr. Udo Schickhoff
Laufzeit: 2007-2010
Die alpinen Weidegebiete, oberhalb der süd-kirgisischen Walnuss-Wildobst-Wälder, sind aufgrund der gegenwärtigen Überweidung in einem kritischen Zustand. Auswirkungen veränderter Lebensunterhaltsstrategien auf die Umwelt kommen in der zweiten Dekade des Transformationsprozesses zunehmend in einem Wandel von Struktur und Funktion beweideter alpiner Ökosysteme zum Ausdruck. Die gegenwärtig nicht nachhaltige Nutzung der Weideressourcen sowie der äußerst defizitäre Forschungsstand zu den sozioökonomischen Ursachen und ökologischen Folgewirkungen sind Gegenstand der Untersuchungen dieses von der Volkswagenstiftung finanzierten Projektes.
Spatial high resolution regionalization of urban climates, integrating statistical and dynamical downscaling and remote sensing techniques, Projekt am KlimaCampus (CLISAP D4)
Dipl. Geogr. Thomas Langkamp
Projektwebseite: Urban Systems and Urban Climate (Workpackage II)
und KlimaCampus.de
Betreuer: Prof. Dr. Jürgen Böhner und Prof. Dr. Jürgen Oßenbrügge
Laufzeit: 2009-2012
The so called work pckage II of the CLISAP D4 subproject 'Urban Systems and Urban Climate' focuses on the modelling and downscaling of recent urban climates. The project aims to develop a comprehensive modelling approach for the city of Hamburg. It will allow spatio-temporal high resolution regionalisation of urban climate change effects like rainfall extremes (flooding) or heat waves (associated with high ozone concentration). In order to enable a physically consistent simulation we propose a hierarchical modelling scheme of statistical and dynamical downscaling steps in which advanced surface parametrisation methods will take into account the topographic heterogeneity.