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The deep geological underground represents an important georesource for the short-
term storage of renewable energy and the long-term reduction of greenhouse gas emissions. To ensure the economic viability and safety of any subsurface storage project, detailed characterisation of the quality and integrity of the reservoir and its cap rock is required. This characterisation includes the accurate determination of the petrophysical properties, such as porosity and permeability, as well as the potential mineral reactions, such as the dissolution of reactive phases, which may occur during the lifespan of such a project. Clay minerals are common components of many reservoir systems and, depending on their type and structure, can have a significant impact on storage and transport properties. These processes are, however, currently not well understood. In order to address these issues, the main focus of this thesis is on mineralogical analyses using X-ray diffraction (XRD) and microstructural studies using focused ion beam scanning electron microscopy (FIB-SEM) together with micro X-ray computed tomography (µXCT) to gain a better understanding of the influence of clay minerals on reservoir and cap rock properties.
A central part of this thesis focuses on the analysis of clay minerals and pore structures of the Bebertal Sandstone of the Parchim Formation (Early Permian, Upper Rotliegend), which is considered a natural analogue for the tight reservoir sandstones of the North German Basin. Two illite polytypes with a variety of characteristic structures have been identified in the Bebertal sandstone. Disordered 1Md illite forms the majority of the observed structures, which include omnipresent grain coatings, altered permeable feldspar grains and pore-filling meshwork structures. Trans-vacant 1M illite represents the second and youngest generation of authigenic illite and occurs as fibrous to lath-shaped particles that grew into open pore spaces and led to a significant reduction in porosity and permeability during late diagenesis. Based on these results, a model for the formation of illite polytypes in the aeolian layers of the Bebertal sandstone was developed that describes the temporal and spatial evolution of porosity and permeability during diagenesis. Information from this model was then used to improve the prediction of permeability of the Bebertal sandstone based on µXCT pore space models and direct numerical simulations. To achieve this, a micro-scale pore space model was created that allowed the simulation of permeability reduction by clay minerals by including nanoporous illite domains based on a novel morphological algorithm. By performing Navier-Stokes-Brinkman simulations, more accurate predictions of permeabilities with respect to experimentally determined values were obtained compared to conventional Navier-Stokes simulations.
The detailed characterisation of the Bebertal sandstone has shown that natural reservoir rocks are usually complex heterogeneous systems with small-scale variations in texture,
composition, porosity and permeability. Flow-through experiments on the Bebertal sandstone revealed that the coupled geochemical and hydrodynamic processes that occur during the dissolution of calcite could not be predicted by reactive transport models. Therefore, as part of this thesis, a novel approach for developing synthetic sandstones at low temperatures based on geopolymer binder was developed. It is shown that simpler and more homogeneous porous materials can be produced with porosity and permeability values in the range of natural sandstones. These can be used to better understand the dynamic and coupled processes relevant to the storage of renewable energy in reservoir rocks through improved experimental constraints.
The final part of this thesis reports on a detailed clay mineral and pore space study of
three shale formations and one mudstone that were identified as potential seals for the Mt. Simon sandstone reservoir in the Illinois Basin. During the Illinois Basin - Decatur Project, this reservoir was used for the sequestration of one megaton of supercritical carbon dioxide. In order to better assess the quality of the sealing units and to better understand the role of the intergranular clay mineral matrix as potential pathway for fluid migration, a multi-scale evaluation was conducted that included thin section analysis, quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN), mercury intrusion capillary pressure (MICP) measurements, quantitative XRD and high-resolution FIB-SEM. The results allow for the classification of the studied formations into primary and secondary seals and emphasise the importance of three-dimensional clay-mineral-related pore structure characterisations in cap rock studies. XRD proved the most reliable method for the identification and quantification of clay minerals in the studied cap rocks and mudstones. In contrast, FIB-SEM and QEMSCAN provided the spacial constraints for reconstructing fluid flow pathways within the clay mineral matrix.
Overall, this thesis highlights the importance of the precise identification of clay minerals in geological reservoirs and their cap rocks. It also illustrates the need for three-dimensional characterisation and modelling of the associated small pore structures for an improved understanding of the rocks diagenetic history as well as the prediction of the transport and storage properties of these crustal reservoir systems.
Underground hard coal mining operations irreversibly disrupt the pre-existing mechanical equilibrium of the geological media. The employment of high-recovery methods modifies the stress field of the sedimentary sequence, generating movement and faulting of the rock layers above and below mined seams. These new fracture zones do affect the original conditions of the hydrogeological system by modifying flow pathways and increasing the permeability of the rock sequence. Moreover, the surface area of rock exposed to air and water is increased, conditioning the water-rock interaction. Despite this rather clear conceptualization, flow and reactive transport processes in fractured overburdens are rarely modeled simultaneously. Discrete setups that consider fractures and porous matrix require extensive characterization of both media, which is impractical for regional case studies. As a result, most post-mining models explicitly ignore fracture structures by employing the equivalent porous approach or even both media with lumped parameter models. However, omitting either medium represents a delicate simplification, considering that mining-related fractures control the rate and direction of water flow within moderately permeable but relatively highly porous rock sequences.
In this dissertation, the specific contribution of fractured and matrix continua to the transient discharge and water quality of a post-mining coal zone is quantified and evaluated. For this purpose, dual and multiple interacting continua models are employed to simulate fluid flow and reactive mass transport in fractured and variable water-saturated rock sequences. The effectiveness of the models is evaluated by simulating the origin, generation and transport of acid mine drainage (i.e., water with elevated concentrations of hydrogen, iron, sulfate and chloride) within the shallow overburden of the Ibbenbüren Westfield. Compared to other coal districts in Germany, this area is strongly delimited by the local geology and topography, resulting in a well-defined hydrogeological system to test the models. Petrographic and chemical analyses performed on core samples from the area show the strong influence of mining-derived fractures on the water-rock interaction within the Carboniferous sequence. The presence of oxidized pyrite along with amorphous iron hydroxide phases in weathering fronts on both sides of the fractures demonstrates the exchange of solutes and gases between the fractured and the porous matrix media.
Based on the previous evidence, the TOUGHREACT software is employed to characterize flow and reactive transport processes in the Westfield. However, each of the two processes is simulated at separate stages to have more control in the adjustment of sensitive parameters for which little information is available. For the flow component, a dual continuum model, with Richard’s equations is used to characterize the unsaturated water flow in both fractured and matrix media. Under this approach, the model adequately reproduces the bimodal flow behavior of the discharges measured in the mine drainage for the years 2008 and 2017. Simulation results show how the fractured continuum generates intense discharge events during the winter months while the rock matrix controls smooth discharge limbs in summer, when water is slowly released back to the fractures. With the flow component calibrated, the second part of the study incorporates the geochemical processes into the model based on actual data from the rock samples. Their simulation requires extending the two-continuum setup to a multiple continua model with five nested block strings: one for the fractures and four for the rock matrix. This further subdivision prevents under-representations of kinetic reactions with short equilibrium length scales and numerical instabilities due to lack of chemical and flow gradients. As a result, the new multiple continua model provides good agreement with respect to long- and short-term concentrations and discharge trends measured in the mine drainage. The flow of oxygen and meteoric water through the fractured continuum leads to a high and steady release of hydrogen, iron and sulfate ions derived from pyrite oxidation in the matrix continua closest to the fractures. Moreover, high chloride concentrations result from the mixing and gradual release of relatively immobile solutes in the matrix as they interact with percolating water in the fracture. Both findings are equally congruent with the reactive pyrite oxidation and iron hydroxide precipitation fronts identified in the fractured core samples.
In the end, the multiple continua models, the simulation procedure and the results of the benchmark and sensitivity analysis scenarios developed for the Westfield pave the way for the application of the approach in other mining zones. The first candidate emerges in the Ibbenbüren Eastfield, where a coupled elemental-isotopic approach included in this thesis has confirmed that water-conducting fracture zones are primary elements for solute generation and transport in the first 300 meters of the overburden. In the latter case, calibration and verification of the models can be complemented with measurements of δ34S in sulfates and δ18O, δ2H, and Tritium in water.
The skull is an extremely informative part of the vertebrate body. Skulls are
involved to hunt, feed and drink, to nurse, fight, dig, and to many other activities.
Also, main sensory organs are situated on the head in order to enable a given
animal to see, smell, taste, feel, listen, equilibrate and think; hence, the head is the
main connection to the external world. It follows that a skull, with and without soft
tissue, can tell a lot about its owner. Each skull consists of many individual bones
constituting regions (e.g., snout and braincase) that represent different aspects of an
anatomical mosaic, which in turn allows deeper (palaeo)biological insights.
In the past three centuries, palaeontologists dug out countless fossils from all
over the world and from many preserved periods and groups, including dinosaurs.
Hence, public and private collections house numerous fossil skull specimens. To
further enlighten our understanding of palaeoecological, physiological and
phylogenetic affinities of dinosaurian representatives belonging to different groups,
and in order to reveal new aspects on their (neuro)anatomy, behaviour, ontogeny
and evolution, a thoroughly examination with modern techniques is the aim of this
thesis.
In order to get a phylogenetically broad understanding, fossil remains from at
least four extinct species, including Irritator challengeri (a theropod: mostly bipedal
carnivores) from the Early Cretaceous of northeastern Brazil, Europasaurus holgeri
(a sauropod: long-necked, quadrupedal herbivores) from the Late Jurassic of Lower
Saxony, Emausaurus ernsti together with an unnamed taxon from the Early Jurassic
of Mecklenburg-Western Pomerania, and Struthiosaurus austriacus, Late
Cretaceous of eastern Austria (the latter three are thyreophorans: armoured, mostly
quadrupedal herbivores), were in closer focus. To document and digitally reconstruct
cranial bones and cavities therein, the material was examined with micro computed
tomography (microCT). On this basis, the full morphology of the preserved anatomy
was revealed, described and contextualized, for example, in conjunction with
comparative anatomy and biomechanical considerations. During this process, further
methods were used to investigate and depict individual fossils: macro- and microphotography,
photogrammetry and phylogenetic analyses, each encompassing
multiple sub-tasks and being supported by 3D prints.
As part of the result, it was possible to formulate reasoned assumptions about
the lifestyle of the taxa in focus. For instance, the neuroanatomy and the osteological
characteristics of the spinosaurid Irritator challengeri implicate that this taxon was an
agile hunter with a habitually inclined snout that was specialized in catching relatively
small prey with a robust dentition and a comparably weak - but fast - bite, with a
remarkable jaw mechanism which enabled the animal to kinetically widen the
pharynx during lower jaw depression. The (neuro)anatomy of I. challengeri, S.
austriacus, E. ernsti and E. holgeri presented here, enrich our knowledge about a
plethora of (lifestyle-related) aspects of these animals, their closer relatives and the
prehistoric world they lived in.
Seas and oceans are essential for the global ecosystem. Entire societies, economies and countless livelihoods rely on their good environmental status. Yet, pressures on marine environments are increasing. An extensive assessment and monitoring of marine habitats is a vital precondition for understanding these systems and their sustainable conservation. Remote sensing methods can temporally accelerate the mapping, improve the spatial resolution and support the interpretation of large areas. Hydroacoustic becomes the method of choice for areas deeper than the coastal zone as optical signals are limited by strong attenuation in the water column. Apart from depth measurements for the creation of bathymetric charts, the recording of backscatter strength is useful for the characterization of the seafloor surface. The direct influence of the inhabiting benthic community on the backscattered signal is rarely considered, although it can be utilized for the detection of benthic life. Information about habitat-specific backscatter responses or a hydroacoustic remote sensing catalog for benthic habitats is missing so far.
The multibeam echosounder (MBES) has the advantage of recording both, bathymetry and backscatter strength simultaneously with related incidence angle. Further, recent technological developments allow to change between frequencies. Angular range curves supported the quantification of backscatter strength of different frequencies. Acoustic data sets were complemented by ground truthing in form of sedimentological and biological samples as well as video profiles. Study areas were located offshore the island of Sylt in the North Sea as well as in vicinity to Oder Bank and close to the coast offshore Hohe Düne/Rostock, both in the Baltic Sea. Investigated habitats included sand areas inhabited by tubeworms, loose mussel clusters on top of sand areas, seagrass meadows, coarse sand and gravel areas, and a reef covered by mussels.
Multifrequency backscatter maps, combining frequencies between 200 kHz and 700 kHz, illustrate small-scale features at the seafloor not visible in monofrequent maps. Key habitats showed a specific backscatter response, which can partly be related to macrobenthic flora and fauna. Data sets recorded with a (partly calibrated) MBES in three different month (May, August, October) revealed that backscatter strength can further detect spatial as well as temporal habitat dynamics. Alterations in the sediment composition at the seafloor surface of the ecologically valuable coarse sand and gravel areas were caused by seasonal changes in local hydrodynamics.
A newly developed 3D seismic lander has the ability to support hydroacoustic remote sensing as an additional, non-destructive ground truthing method utilizing a high frequency of 130 kHz to image the shallow subsurface. Buried objects, e.g., stones, shells, fruit gummy worms, as well as sediment disturbances could be detected and visualized in a laboratory experiment. The 3D seismic lander is likely to improve the investigation of volume scatter contribution to backscatter strength and is potentially applicable for the imaging of bioturbation.
Anthropogenic greenhouse gases such as carbon dioxide (C02) must be mitigated and reduced to preserve
a stable climate for future generations. One promising technology is carbon capture and storage (CCS) in
geologic formations, which is currently being deployed in numerous pilot projects across the United
States. One of these is the Illinois Basin–Decatur Project that has successfully stored 1 million metric tons
of C02 in the Mt. Simon storage complex. The Mt. Simon Sandstone reservoir has been largely unexplored
due to a previous lack of economic interest. Oil-bearing formations in the Illinois Basin are in younger
successions and formation waters in the Mt. Simon are highly saline but with low levels of critical elements
(i.e. lithium, magnesium). In the Illinois Basin, a limited number of drill holes penetrate the Mt. Simon
formation with an even smaller number of core samples in these deep strata. This has left the earliest
Paleozoic rocks in the Illinois Basin poorly understood. The stratigraphic test well at the IBDP revealed
the lowest most section of the Mt. Simon to be a thick highly porous and permeable sandstone. With a
near to complete lack of other wells penetrating this lower Mt. Simon unit, major questions arose such as
1) what is the origin of this deep porous sandstone; 2) what controls the distribution of this sandstone
and where can more of it be found; 3) what controls porosity at this depth when overlying sandstones
have largely poor reservoir properties; and 4) is it suitable for geologic carbon storage (i.e. are there high
quality seals that provide secure storage and prevent vertical migration)?
This research examines the origin and diagenesis of the Mt. Simon storage complex by first resolving the
age of the underlying Precambrian basement and investigating basement structures associated with
sediment accommodation (chapter ii). Basement geochronology and a comprehensive investigation of
the Mt. Simon provenance (chapter iii) suggests a largely local sediment supply depositing into a rift basin.
Detrital zircon geochronology of the lower Mt. Simon yields a dominant Mesoproterozoic proximal source
as confirmed in regional basement samples yielding Eastern Granite-Rhyolite, Southern Granite-Rhyolite,
and Mazatzal Province rocks. A small peak of Early Cambrian zircons (527 to 541 Ma) in the lower Mt.
Simon is indicative of rift volcanics as confirmed by the geochronology of a basalt sample recovered in a
deep stratigraphic test hole along the rift axis in west-central Indiana. Failed rifting pre-dated the
formation of the Illinois Basin with the earliest Paleozoic sediments deposited in a northward trending
Cambrian aulacogen. Locally sourced arkose in the lower Mt. Simon is considered to present an
anomalously high porosity that was preserved throughout its diagenetic history. Petrographic
characterization shows the lower Mt. Simon contains abundant diagenetic grain coatings of illite that
prevented pervasive nucleation of authigenic quartz found in the other overlying Mt. Simon units (chapter
iv). These clay coating are considered the most significant feature that controlled porosity preservation
in the Mt. Simon storage complex. Geochronology of these illite coatings reveals two major events of
illitization both of which correspond with structural deformation and igneous activity in and around the
basin in response to regional orogenic events (chapter v). The early illitization event (mostly
Carboniferous) was associated with smectite illitization and potassium feldspar dissolution, which caused
significant secondary porosity. The later illitization event (Triassic) is identified in non-reservoir units of
the Mt. Simon where pore occluding kaolinite was partially illitized. Lastly, high-resolution pore space
characterization of thick pervasive shale formations overlying the Mt. Simon indicates the Eau Claire shale, directly overlying the Mt. Simon, provides the best seal to the Mt. Simon reservoir completing the Mt. Simon storage complex (chapter vi).
This thesis aims to investigate effects of anthropogenic environmental impact on the Richards Bay area. Located on the east coast of South Africa, Richards Bay Harbour evolved into the country’s premier bulk cargo port. The Associated change in land-use and industrial as well as agricultural pollution pose environmental, ecological and human health risks. Here, sedimentological and geochemical investigations focus on the port as final sink for environmental and industrial pollutants, such as metal concentrations, organochlorine pesticides and microplastics.
The study is based on investigations of surface sediment samples from the water-sediment interface to identify spatial distribution patterns, as well as sediment cores to follow temporal changes. Endmember modelling of grainsize distributions, proved to be a viable parameter to distinguish different accumulation spaces and enabled the classification into six harbour sub-basins. Subsequent investigations on the content of microplastics, Polyethylene terephthalate (PET) and Low-density polyethylene (LDPE), showed that these different types of microplastics predominate in two different areas: PET appears to be directly tied to higher populated (tourism) beaches, while LDPE is deposited in low-current sub-basins. Increased metal concentrations link to activities at the bulk cargo berths, where especially Cr and Cu concentrations exceeded the local sediment guideline thresholds. In the areas of high metal concentrations, bioindicators (ostracods, foraminiferas, diatoms) also indicate increased shares of malformed specimens. Multiple recovered sediment cores recorded changes in recent export practices, indicating ceased Cu handling and increased Cr handling over the past decade. Noticing multiple possible influencing factors on elemental distributions, created by the surrounding geological and industrial impact, the usefulness of different normalisers (Al, Fe, Rb, Ti and silt fraction) for Cr, Cu, Co and Pb concentrations was compared and site specific baseline metal concentrations were defined. This identified Al and Rb to be effective normalisers in Richards Bay and Fe or Ti to be affected by local conditions. Data of organochlorine pesticide pollution was gathered in the area of Richards Bay, Goedertrouw Dam and Umlalazi River. The two dominant groups of contaminants detected are dichlorodiphenyltrichloroethanes (ΣDDT, 12 – 350 ng g-1), linked to the use of malaria vector control, and hexachlorocyclohexanes (ΣHCH 35 – 230 ng g-1), an agricultural insecticide. Both indicate recent entry and exceed sediment quality guideline limits, raising concern for local communities and estuarine environments. Seismic data was used to investigate the preindustrial evolution of the incised valley system and bayhead delta at Richards Bay Harbour. A stratigraphically supported development model was created. The thesis shows that harbour sediment is an important sink for inorganic and organic contaminants. Each investigation on environmental pollutants, such as metals, pesticides, microplastics or bioindicator analyses, indicates their deposition in distinct harbour sub-basins. Therefore, their effect can be spatially differentiated and related to plausible sources of pollution. Richards Bay thus represents a variously affected system along the South African coast, in which it is necessary to take environmental protection measures in terms of sustainable and environmentally friendly management.
Die Dissertation beschäftigt sich mit der für die Humangeographie aktuellen Assemblage-Theorie. Thematisch fokussiert sich die Arbeit auf die Nutzung der Fischbestände und die Zusammenkunft dieser Nutzung mit Politik. Dadurch weist das bearbeitete Thema einen klaren Bezug zu aktuellen gesellschaftlichen Entwicklungen und zur derzeitigen wissenschaftlichen Diskussion auf. Die Stärke der Arbeit liegt in den Überlegungen zur Assemblage-Theorie und deren Operationalisierung für die geographische Forschung. Ausgangspunkt dieser Überlegungen bildet das Buch ‚Tausend Plateaus Kapitalismus und Schizophrenie, Band 2‘ von DELEUZE, G. und GUATTARI, F. in der deutschen Übersetzung von 1992. Darauf aufbauend wird näher auf die Denk- und Herangehensweise eingegangen und der thematische Fokus (Fischereipolitik) mit dem theoretischen Ansatz (Assemblage) verkettet.
Over thousands of years, peatlands around the world have accumulated carbon (C) stocks of global importance. Drainage for agriculture, forestry and peat extraction has transformed many peatlands from long-term sinks into strong sources of carbon dioxide (CO2). Peat extraction is worldwide responsible for about ten percent of drained peatlands and is mainly carried out in northern countries and Eastern Europe. In Belarus, 0.3 Mha of peatlands are drained for peat extraction, which is twelve percent of the country's peatland area. From 2006 to 2013, 21,333 ha of this area have been rewetted to protect these peatlands from fire and further degradation, reduce their greenhouse gas (GHG) emissions, turn them back into C sinks and promote biodiversity. A further 260,000 ha are no longer used for peat extraction and their rewetting would be a great benefit for nature conservation and climate protection.
Rewetting of abandoned peat extraction areas usually leads to inundation of large areas where not adapted plants die and new species establish, depending on water level and nutrient conditions. Beavers, of which there are many in Belarus, also play an important role in the rewetting of peatlands. They dam up ditches in drained and rewetted peatlands, thus contributing to water level increases and vegetation changes. The aim of this PhD thesis was to investigate the impact of inundation on vegetation and GHG emissions in formerly extracted fens in Belarus, to determine the role of water level in this process, and to study whether such fens develop back into C sinks with an almost neutral GHG balance within one or two decades after rewetting (Papers II and III). Also the potential of beaver activities for peatland restoration was assessed (Paper III).
Two very different fens, rewetted after peat extraction, were chosen as study areas. The first one, Giel'cykaŭ Kašyl, is a former flood mire and was rewetted with water from the Jasiel'da River in 1985. During the study period 2010–2012 this site was a shallow lake (~ 1 m deep) dominated by very productive, tall reed. Shallower areas along the edges had a partly floating vegetation cover of cattail (Typha latifolia, T. angustifolia) and sedges (Carex elata, C. vesicaria). The second fen, Barcianicha, is fed by groundwater. Rewetting from 1995 onwards resulted in water levels at or slightly above surface and a lower nutrient availability compared to Giel'cykaŭ Kašyl'. This was reflected in the establishment of mesotrophic communities of Eriophorum angustifolium and Carex rostrata. Phragmites australis stands, which were also dominant here, were shorter and less productive than in Giel'cykaŭ Kašyl'. The southern area of Barcianicha was not used for peat extraction and has not been rewetted. Until 2009 vegetation of this part was characterized by forbs (Urtica dioica) and wet meadows (Agrostis stolonifera). From autumn 2009, a beaver dam in the main drainage ditch caused flooding of these areas and led to diverging vegetation development depending on water levels.
Within the framework of this doctoral thesis annual fluxes of CO2, methane (CH4) and nitrous oxide (N2O) and the development of water levels and vegetation were monitored for two years at nine sites and evaluated (Papers II and III). Three of the sites, respectively, were located (a) in Giel’cykaŭ Kašyl’, flooded in 1985, (b) in the central area of Barcianicha, which was rewetted in 1995, and (c) in the southern part of Barcianicha, which was flooded by beavers end of 2009. GHG measurements were carried out with manual chambers from August 2010 to September 2012. Annual net CO2 exchange rates (NEE) were modeled based on light response curves of gross primary production (GPP) and on temperature response curves of ecosystem respiration (Reco), which were determined every third to fourth week by alternating measurements with transparent (cooled) and opaque chambers (both with fan) along the daily amplitude of photosynthetically active radiation (PAR) and temperature. Annual CH4 emissions were calculated mainly based on the temperature response of CH4 fluxes over the course of the year, based on biweekly (in summer) to monthly (in winter) repeated single measurements with opaque chambers (without fan). This was done, although all longer rewetted sites were dominated by aerenchymatic plants whose gas transport during the vegetation period may change over the course of the day and can be influenced by shading. This might apply to the six longer rewetted sites, two of which were dominated by Phragmites australis, and the others by Typha latifolia, Carex elata, Carex rostrata or Eriophorum angustifolium. For these six sites therefore studies on the daily course of CH4 release and the influence of chamber shade were conducted, covering 8–24 hours and lasting at least from sunrise to afternoon. Also the extent to which flux rates were affected by a lack of chamber headspace mixing by fans was investigated in the mentioned studies (Papers I and II).
The daytime course of CH4 emissions showed a pronounced dynamic for Phragmites australis in both fens, with minimum release during the night and maximum during the day (Paper I). The other sites in contrast did not show a significant diurnal CH4 flux dynamic (Paper II). Lack of headspace mixing by fans as compared to chambers with fan resulted in a slight underestimation of CH4 emissions at very high chambers (220 and 250 cm), as used for Phragmites australis in Giel'cykaŭ Kašyl', while there was no difference at lower chambers (≤185 cm), as used for the other sites. Opaque chambers resulted for sites dominated by Typha latifolia and Carex elata in significantly (1.2 times and 1.1 times, respectively) lower CH4 fluxes compared to transparent chambers. For the other sites, opaque chambers did not significantly reduce CH4 emissions. This result was unexpected, especially for Phragmites australis, as PAR out of all parameters tested had the strongest influence on CH4 emissions from both reed sites, and clouds directly led to reduction of their emissions. Presumably the gas flow in the reed shoots located within opaque chambers was maintained by shoots outside the chamber that were connected to the enclosed shoots by rhizomes (Paper I). The investigations showed that single measurements between 9 a.m. and 6 p.m. with opaque chambers without fan, as performed for the determination of annual CH4 fluxes, resulted for Carex rostrata and Eriophorum angustifolium in estimates similar to the daily mean, but for Phragmites australis in estimates that were rather above the daily mean. Annual CH4 fluxes from Phragmites australis could therefore be slightly overestimated. CH4 fluxes from Typha latifolia and Carex elata during the vegetation period were corrected by a factor of 1.2, although darkness inside of opaque chambers matters only at day, not at night. Daily and annual CH4 fluxes from these sites have been therefore most likely slightly overestimated, too.
Water saturation and the establishment of adapted vegetation were the most important conditions for the restoration of C sinks (gaseous CO2 and CH4 fluxes) in the investigated peatlands. The only site with falling water levels in summer and thus temporarily aerated peat was the beaver flooded forbs (Urtica dioica) site at Barcianicha. This site was a very strong CO2 emitter and the only significant N2O source of the entire study (Paper III). All other sites were permanently wet, had much lower CO2 emissions or were even net C sinks (Papers II and III). Establishment of adapted vegetation depended on inundation depth and time since rewetting. For example, within one year the meadow site in Barcianicha shallowly flooded by beaver was colonized by Carex rostrata and other adapted helophytes and developed into a CO2 sink, while the deeper flooded site at the same meadow initially attracted only Chara and some individuals of Alisma plantago aquatica and remained a moderate CO2 source. However, the results of the longer rewetted sites show, that also deeply (~ 1 m) flooded fen areas can become densely populated with mire plants in the course of 25 years and develop into net C sinks. Highest annual C uptake in both fens was achieved by the reed sites. Eriophorum angustifolium and Carex rostrata in mesotrophic Barcianicha were smaller C sinks. Typha latifolia and Carex elata in the eutrophic Giel'cykaŭ Kašyl', on the other hand, released CO2, presumably because the high and fluctuating water levels imposed stress to the plants, and because the large supply of nutrients and dead plant material allowed for strong heterotrophic respiration (Paper II). The simultaneously high CH4 emissions made Typha latifolia and Carex elata major sources of GHG. CH4 emissions from Phragmites australis in Giel'cykaŭ Kašyl' were even higher, but due to extremely high CO2 uptake the site was only a small net GHG source. CH4 emissions in Barcianicha were much lower and comparable to undisturbed sedge fens. The difference between Giel'cykaŭ Kašyl' and Barcianicha was mainly due to the different nutrient supply and the related productivity of the plants. Important conclusions are that stable inundation is an appropriate measure for restoration of the C sink of formerly extracted fens, but nutrient input with water needs to be stopped or reduced in order to decrease CH4 production. If this is not possible, establishment of Phragmites australis and other strong C sinks could help to compensate for the climate impact of high CH4 emissions from eutrophic sites.
The effect of the beaver dam on the development of the southern part of Barcianicha depended not only on the initial situation but mainly on the water level. Under optimal conditions, it led to the rapid establishment of adapted mire plants, the restoration of a C sink and a significant reduction of GHG emissions. However, this situation in the shallowly flooded meadow was achieved by chance. In comparison to planned rewetting measures, which aim to raise the water level evenly over the entire peatland, beavers dam ditches in order to improve their immediate habitat, thus influencing water levels only up to a certain distance, but rarely over the entire peatland. Nevertheless, beaver activity is of high value both for mire conservation projects, where existing dams are supplemented by beaver dams, and for abandoned, drained peatlands, like former peat extraction areas in Belarus, many of which at least partially have been rewetted by beavers.
Der globale Rückgang der Artenvielfalt, verursacht durch das intensive Eingreifen des Menschen in die Ökosysteme, zählt zu den großen Herausforderungen der kommenden Jahrzehnte, nicht zuletzt im Interesse des Menschen, dessen Existenz dadurch zunehmend bedroht wird. Auch Wälder sind von dieser Entwicklung betroffen. In Deutschland über Jahrhunderte zu Forsten umgebildet, die vorwiegend der Holzproduktion dienten, führte dies zu monotonen Strukturen, in denen natürliche Elemente wie Totholz nicht den notwendigen Platz haben, um die zahlreichen davon abhängigen Arten zu versorgen. Derzeit findet jedoch – ausgelöst durch wissenschaftliche Befunde – ein gesellschaftliches Umdenken statt, das natürliche Waldelemente vermehrt in Wirtschaftswälder integrieren möchte.
Vor dem Hintergrund der sich durch diese Entwicklungen abzeichnenden Veränderung der Wälder wurde nun erstmals für das deutsche Bundesland Bayern flächenrepräsentativ untersucht, wie die Bevölkerung dieser Veränderung gegenübersteht, und wie die kulturellen Ökosystemleistungen von Wäldern, also die Beiträge des Ökosytems Wald für das menschliche Wohlergehen, wahrgenommen und beurteilt werden. Im Vordergrund standen dabei das natürliche Erbe und die Erholung. Dazu wurde eine repräsentative Online-Befragung mit 2473 Probanden durchgeführt, in die zwei leicht modifizierte Choice Experimente eingebunden wurden. Mit ihrer Hilfe sollten nicht nur die Präferenzen für bestimmte Waldzustände und Maßnahmen zur Sicherung der Artenvielfalt aufgedeckt, sondern auch festgestellt werden, welche Trade-offs zwischen ihren gesellschaftlichen, ökologischen und ökonomischen Folgen bestehen. Auch die Einstellung der Befragten gegenüber der Natur allgemein, und Totholz speziell, war Gegenstand der Studie. Zudem wurde über Reisekostenmodelle versucht, die Erholungsleistung der bayerischen Wälder zu bemessen, um sie in Relation zu den anderen Leistungen zu setzen.
Es zeigte sich, dass die Einstellung der bayerischen Bevölkerung gegenüber der Natur und vor allem gegenüber Totholz überwiegend positiv ist, auch wenn unterschiedliche Formen der Umwelteinstellung identifiziert werden konnten. In den Präferenzanalysen ergaben sich positive Zahlungsbereitschaften für solche Waldnaturschutzprogramme, die zu einer Verbesserung der Habitatverfügbarkeit für gefährdete Arten in allen Wäldern, nicht nur in einzelnen Schutzgebieten führen würden. Dabei sind ebenfalls Unterschiede zwischen verschiedenen Waldmanagementstrategien, sowie zwischen bestimmten sozio-demographischen Subgruppen festzustellen. Darüber hinaus konnte ein hoher Wert der Erholungsleistung der bayerischen Wälder ermittelt werden, der sich nicht wesentlich verändern würde, wenn mehr natürliche Strukturen zugelassen werden. Somit wäre diese kulturelle Ökosystemleistung auch weiterhin gewährleistet, vorausgesetzt, dass keine Extremzustände angestrebt werden. Aus Sicht der Forstpraxis und des Naturschutzes ist von besonderem Interesse, dass die Trade-offs, welche zwischen der Gesellschaft und diesen beiden Akteursgruppen bestehen, allen drei Seiten zugute kommen können.
The achievement and monitoring of a good environmental status on continental shelf seas requires
the use of acoustic remote sensing techniques due to their range. The interpretation of acoustic signals
for the identification of benthic communities, however, is still in its infancy. In this thesis, the results
of two field campaigns conducted in a sandy environment off the shore of Sylt Island (North Sea)
utilizing ship- and lander-based acoustic and optical remote sensing techniques are discussed. The
objective of the thesis is a better knowledge of the impact of the polychaete Lanice conchilega on
physical seafloor properties, especially roughness at a cm to mm scale, which is relevant for
understanding acoustic scatter. The results show a clear impact of L. conchilega on roughness even in
sparse populations of less than 2% coverage. However, these sparsely populated areas could not be
reliably identified with acoustic data; a denser population of L. conchilega provided a clearer signal for
the acoustic remote sensing methods. The results are promising regarding the broader use of acoustic
remote sensing techniques for environmental monitoring in selected habitats, although the
determination of minimum population thresholds that can be identified will require further studies.