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The explosive expansion of the population of the Metropolitan Region of Curitiba raised a high increase in the demand for water resources and the uncontrolled settlement poses a large problem for the environment. The greatest menace to the water supply sources of this region is the urban occupation (invasion) into the areas that contain these resources. This occupation continues with its slow, silent, although progressive march, threatening precious and irreplaceable resources. From this background an area in the direct vicinity north-east of Curitiba has been studied. In this area a drinking water reservoir was constructed in the time that the study took place in the Iraí-basin. The Iraí-reservoir even though an area around the lake will be protected may be polluted by two tributaries which flow through more or less densely populated areas. In the study area on the same time wells have been constructed. To estimate what the impact may be from the possibly polluted reservoir on the aquifer a groundwater flow model has been constructed. On the same time to estimate the water balance and the spatial distribution of pollution vulnerability the hydrological model MODBIL has been used. Also other methods have been used to estimate the pollution vulnerability to make a comparison and because none of the methods takes every aspect into account. With the calibrated groundwater flow model for the situation before the construction of the Iraí-reservoir and after its construction, simple particle tracking transport models are constructed as scenarios how the water of the aquifer may be influenced.
Rifting and breakup of Westgondwana in the Late Jurassic/ Early Cretaceous initiated the formation of the South Atlantic and its conjugated pair of passive continental margins. The Walvis Basin offshore NW-Namibia is an Early Cretaceous to recent depositional centre with a typically wedge-shaped postrift sedimentary succession covering an area of 105000km2. A 2D model transect across the central Walvis Basin and adjacent onshore areas is used as a case study to investigate quantitatively the denudational history of the evolving passive margin and the related contemporaneous depositional postrift evolution offshore. The database for both the onshore and offshore part of the model traverse is well constrained by own field work, published data as well as by seismic and well data supported by samples. The ultimate goal of this project is to present an integrated approach towards a quantitative link between surface processes and internal processes in terms of a mass and process balance.
In a three-year study the current aeolian transportation processes were examined in a linear dune area previously used for grazing near Nizzana at the Israeli-Egyptian border. The research area was subject to heavy grazing across the border, which led to the total destruction of the natural vegetation in the period of 1967 to 1982. As a consequence, intensified aeolian activity and significant changes of the morphology of the dunes were observed. After the end of the grazingg on the Israeli side, a rapid return of the vegetation in the interdune corridors and on the footslopes of the dunes took place. In addition also a reduction of obviously active areas on the dune crests was observed. The situation on Egyptian territory west the border remained unchanged until today. This study is aimed at understanding the changed aeolian morphodynamics east the border. The emphasis was placed on the investigation of the spatial and temporal distribution of aeolian sand transport as well as on the influencing factors morphology, surface condition and vegetation.
The Bafoussam area in west Cameroon is located within the Cameroon Neoproterozoic orogenic belt (north of the Congo craton) which is part of the Central African Fold Belt (CAFB).The evolution of the CAFB is related to the collision between the convergent West African craton, the São Francisco – Congo cratons and the Sahara Metacraton. The outcrop area stretches over a surface of ~1000 km2 and dominantly consists of granitoids which intruded wall-rocks of gneiss and migmatite during the Pan-African orogeny. The Bafoussam granitoid emplacement was influenced by the N 30 °E strike-slip shear zone in the prolongation of the Cameroon Volcanic Line, but also by the N 70 °E Central Cameroon Shear Zone. In the field, these two shear directions are expressed in the schistosity and foliation trajectories, fault orientation and the alignment of the volcanic cones as well. In the Bafoussam area, four types of granitoids can be distinguished, including: (i) the biotite granitoid, (ii) the deformed biotite granitoid, (iii) the mega feldspar granitoid, and (iv) the two-mica granitoid. These granitoids occur as elongated plutons hosting irregular mafic enclaves (amphibole-bearing, biotite-rich, and metagabbroic types) and are frequently cut by late pegmatites, aplite dykes and quartz veins. Petrographically, they range in composition from syenogranite (major), alkali-feldspar granite, granodiorite, monzogranite, quartz-syenite, quartzmonzonite to quartz-monzodiorite. Potassium feldspar, quartz, plagioclase and biotite are the principal phases, in cases accompanied by amphibole and accessory minerals such as apatite,zircon, monazite, titanite, allanite, ilmenite and magnetite. Sericite, epidote and chlorite are secondary minerals. In addition, the two-mica granitoid contains primary muscovite and sometimes igneous garnet. In the granitoids, potassium feldspar is orthoclase (microcline and orthoclase: Or81–97Ab19–3), and plagioclase is mainly oligoclase with some albite and andesine (An3–35Ab96–64).Biotite is Fe-rich (meroxene and lepidomelane, with some siderophyllite), having high Fe2+/(Fe2+ + Mg) ratios of 0.40–0.80. It is a re-equilibrated primary biotite and suggests calc-alkaline and peraluminous nature of the host granitoids. Amphibole is edenitic and magnesian hastingsitic hornblende, with high Mg/(Mg + Fe2+) ratios of 0.50–0.62. The evolution of the hornblende was dominated by the edenitic, tschermakitic, pargasitic and hastingsitic substitution types. Primary muscovite is iron-rich [Fe2+/(Fe2+ + Mg) = 0.52–0.82] and has experienced celadonite and paragonite substitutions. Igneous garnet is almandine–spessartine (XFe = 0.99 and XMn = 0.46–0.56). The euhedral grain shapes of garnet crystals and the absence of inclusions coupled with the high Mn and Fe2+contents (2.609–3.317 a.p.f.u and 2.646–3.277 a.p.f.u,respectively) and low Mg contents (0.012–0.038 a.p.f.u) clearly point to its plutonic origin. The Mn-depletion crystallization model is suggested for the origin of the analyzed garnet, i.e. initial crystallization of garnet inducing early decrease of Mn in the original melt. Aluminum-in-hornblende and phengite barometric estimates show that the granitoids crystallized at 4.2 ± 1.1 to 6.6 ± 1.0 kbar, corresponding to emplacement depths of 15–24 km.Zircon and apatite saturation temperature calibrations and hornblende–plagioclase thermometry yielded emplacement temperatures between 772 ± 41 and 808 ± 34 °C. Except the two-mica granitoid, the titanite–magnetite–quartz assemblage gives oxygen fugacities ranging from 10–17 to 10–13, suggesting that the granitoids were produced by an oxidized magma. Since the twomica granitoid lacks magnetite, it was originated from a magma under reducing conditions, below the quartz–fayalite–magnetite buffer. Fluid inclusions in quartz from hydrothermal veins are secondary in nature and are found in trails along healed microcracks or in clusters. Two types of fluid inclusion have been recognized, mixed aqueous–non-aqueous volatile fluid inclusions subdivided into aqueous-rich mixed and non-aqueous volatile-rich mixed fluid inclusions, and pure aqueous fluid inclusions.The non-aqueous volatile-rich mixed fluid inclusions are one-, two-, or three-phase inclusions, whereas the aqueous-rich mixed fluid inclusions are exclusively three-phase inclusions. Both have similar low to moderate salinities (1 to 10 equiv. wt. %). The total homogenization temperatures of the aqueous-rich mixed fluid inclusions are slightly lower than those of the nonaqueous volatile-rich mixed fluid inclusions, ranging from 150 to 250 °C and 170 to 300 °C,respectively. They contain nearly pure CO2, or CO2 with addition of 4.1–13.5 mole % CH4 as volatile constituents. Pure aqueous fluid inclusions are two-phase with lower total homogenization temperatures (130–150 °C) and salinities ranging from 3 to 8 equiv. wt. %. They display mixing salt system characteristics, having NaCl as the dominant salt and considerable amounts of other divalent cations. Aqueous-rich mixed fluid inclusions and pure aqueous fluid inclusions exhibit a low geothermal gradient value of 18 °C/km, whereas the non-aqueous volatiles-rich mixed fluid inclusions have a high density which correspond to high geothermal gradient of 68 °C/km. The studied granitoids are intermediate to felsic in compositions (56.9–74.6 wt. % SiO2)and have high contents of alkalis K2O (1.73–7.32 wt. %) and Na2O (1.25–5.13 wt. %) but low abundances in MnO (0.01–0.20 wt. %), MgO (0.10–3.97 wt. %), CaO (0.37–4.85 wt. %), P2O5(up to 0.90 wt. %). They display variable contents in TiO2 (0.07–0.91 wt. %), Fe2O3* (total Fe = 0.96–7.79 wt. %) and Al2O3 (12.0–17.6 wt. %) contents. The granitoids show a wide range of high-field-strength elements (HFSE) and large ion lithophile elements (LILE) contents, with felsic granitoids being enriched in HFSE and the intermediate granitoids displaying in contrast high LILE concentrations. They exhibit chemical characteristics of non-alkaline to mid-alkaline, alkali-calcic, calc-alkaline, K-rich to shoshonitic, ferriferous affinities. Chondrite-normalized rare earth element (REE) patterns are characterized by a strong enrichment in light compared to heavy REEs [(La/Sm)N = 3.23–9.65 and (Ga/Lu)N = 1.45–5.54, respectively], with small to significant negative Eu anomalies (Eu/Eu* = 0.28–1.08). Ocean ridge granites (ORG)normalized multi-elements spidergrams display typical collision-related granites pattern, with characteristic negative anomalies of Ba, Nb and Y, and positive anomalies in Rb, Th and Sm. The granitoids under study are genetically I-type granitoids (biotite granitoid, deformed biotite granitoid and mega feldspar granitoid) and one S-type granitoid (two-mica granitoid). The I-type granitoids are metaluminous (ASI: 0.70–1.00) or moderately peraluminous if highly fractionated (ASI: 1.01–1.06). The geochemistry and petrological features of these I-type granitoids argue for close genetic relationships and it is suggest that they originated from a single parent magma. The observed variability in mineralogy and major and trace element compositions in these granitoids are then the reflection of the fractional crystallization that evolved separation of plagioclase, biotite, K-feldspar and accessory minerals at the level of emplacement. The two mica S-type granitoid is exclusively peraluminous (ASI: 1.07–1.25) and classified as a peraluminous leucocratic granitoid or leucogranite. It is marked in its CIPW normative composition by the permanent presence of corundum, ranging between 0.12 and 3.03. The Bafoussam granitoids were emplaced in a syn- to post-collisional tectonic environment. The observed deformational features and the concentrations in Y, less than 40 ppm, confirm that they are related to an orogenesis. Whole-rock Rb–Sr isochrons defines an igneous crystallization ages of 540 ± 27 Ma for the biotite granitoid and 587 ± 41 Ma for the mega feldspar granitoid. These ages fit with the range of Pan-African granitoid ages (650–530 Ma) in West Cameroon and correspond to the Pan-African D2 deformation event in the Neoproterozoic Cameroon orogenic belt. The two-mica granitoid yields an older Rb–Sr isochron age of 663 ± 62 Ma which is considered to be probably a mixing age. The Nd–Sr isotopic compositions indicate that the I-type granitoids have been produced by partial melting of a tonalite–granodiorite source in the lower crust. This is supported by their initial 87Sr/86Sr(600 Ma) ratios (0.705–0.709) and by their WNd(600 Ma) values (0.2 to –6.3, mainly < 0). The two-mica granitoid was generated by partial melting of a greywacke-dominated source involving biotite-limited, biotite dehydration melting. Chemical data of the two-mica granitoid that support this hypothesis are low CaO/Na2O (0.11–0.38) and Sr/Ba (0.20–0.30), the high Rb/Sr (2.26–7.00), the high initial 87Sr/86Sr(600 Ma) ratios ranging from 0.708 to 0.720, the large range in Al2O3/TiO2 (47–204) and the negative WNd(600 Ma) values (–9.9 to –14.0). Moreover,the higher initial 87Sr/86Sr(600 Ma) ratios of the two-mica granitoid are consistent with an upper crust origin. The depleted mantle Nd model ages (TDM) of 1.3–2.3 Ga indicate that the studied granitoids originated by partial melting of Paleoproterozoic and Mesoproterozoic crust, with limited mantle-derived magma contribution. The high initial 87Sr/86Sr(600 Ma) ratios of these granitoids coupled with the wide negative WNd(600 Ma) values strongly suggest a very long residence time in the crust of their protoliths before the melting event. The petrologic signatures of the Bafoussam granitoids are similar to those described in other Pan-African belts of western Gondwanaland such as the neighbouring provinces of Nigeria and the Central African Republic, as well as in the Borborema Province of northeastern Brazil. This supports the previous hypothesis that the Central African fold Belt including Cameroon, Nigeria and the Central African Republic provinces has a continuation in Brazil.
The eminent importance of snow cover for climatic, hydrologic, anthropogenic, and economic reasons has been widely discussed in scientific literature. Up to 50% of the Northern Hemisphere is covered by snow at least temporarily, turning snow to the most prevalent land cover types at all. Depending on regular precipitation and temperatures below freezing point it is obvious that a changing climate effects snow cover characteristics fundamentally. Such changes can have severe impacts on local, national, and even global scale. The region of Central Asia is not an exception from this general rule, but are the consequences accompanying past, present, and possible future changes in snow cover parameters of particular importance. Being characterized by continental climate with hot and dry summers most precipitation accumulates during winter and spring months in the form of snow. The population in this 4,000,000 km² vast area is strongly depending on irrigation to facilitate agriculture. Additionally, electricity is often generated by hydroelectric power stations. A large proportion of the employed water originates from snow melt during spring months, implying that changes in snow cover characteristics will automatically affect both the total amount of obtainable water and the time when this water becomes available. The presented thesis explores the question how the spatial extent of snow covered surface has evolved since the year 1986. This investigation is based on the processing of medium resolution remote sensing data originating from daily MODIS and AVHRR sensors, thus forming a unique approach of snow cover analysis in terms of temporal and spatial resolution. Not only duration but also onset and melt of snow coverage are tracked over time, analyzing for systematic changes within this 26 years lasting time span. AVHRR data are processed from raw Level 1B orbit data to Level 3 thematic snow cover products. Both, AVHRR and MODIS snow maps undergo a further post-processing, producing daily full-area mosaics while completely eliminating inherent cloud cover. Snow cover parameters are derived based on these daily and cloud-free time series, allowing for a detailed analysis of current status and changes. The results confirm the predictions made by coarse resolution predictions from climate models: Central Asian snow cover is changing, posing new challenges for the ecosystem and future water supply. The changes, however, are not aimed at only one direction. Regions with decreasing snow cover exist as well as those where the duration of snow cover increases. A shift towards earlier snow cover start and melt can be observed, posing a serious challenge to water management authorities due to a changed runoff regime.
The ecosystem of the high northern latitudes is affected by the recently changing environmental conditions. The Arctic has undergone a significant climatic change over the last decades. The land coverage is changing and a phenological response to the warming is apparent. Remotely sensed data can assist the monitoring and quantification of these changes. The remote sensing of the Arctic was predominantly carried out by the usage of optical sensors but these encounter problems in the Arctic environment, e.g. the frequent cloud cover or the solar geometry. In contrast, the imaging of Synthetic Aperture Radar is not affected by the cloud cover and the acquisition of radar imagery is independent of the solar illumination. The objective of this work was to explore how polarimetric Synthetic Aperture Radar (PolSAR) data of TerraSAR-X, TanDEM-X, Radarsat-2 and ALOS PALSAR and interferometric-derived digital elevation model data of the TanDEM-X Mission can contribute to collect meaningful information on the actual state of the Arctic Environment. The study was conducted for Canadian sites of the Mackenzie Delta Region and Banks Island and in situ reference data were available for the assessment. The up-to-date analysis of the PolSAR data made the application of the Non-Local Means filtering and of the decomposition of co-polarized data necessary.
The Non-Local Means filter showed a high capability to preserve the image values, to keep the edges and to reduce the speckle. This supported not only the suitability for the interpretation but also for the classification. The classification accuracies of Non-Local Means filtered data were in average +10% higher compared to unfiltered images. The correlation of the co- and quad-polarized decomposition features was high for classes with distinct surface or double bounce scattering and a usage of the co-polarized data is beneficial for regions of natural land coverage and for low vegetation formations with little volume scattering. The evaluation further revealed that the X- and C-Band were most sensitive to the generalized land cover classes. It was found that the X-Band data were sensitive to low vegetation formations with low shrub density, the C-Band data were sensitive to the shrub density and the shrub dominated tundra. In contrast, the L-Band data were less sensitive to the land cover. Among the different dual-polarized data the HH/VV-polarized data were identified to be most meaningful for the characterization and classification, followed by the HH/HV-polarized and the VV/VH-polarized data. The quad-polarized data showed highest sensitivity to the land cover but differences to the co-polarized data were small. The accuracy assessment showed that spectral information was required for accurate land cover classification. The best results were obtained when spectral and radar information was combined. The benefit of including radar data in the classification was up to +15% accuracy and most significant for the classes wetland and sparse vegetated tundra. The best classifications were realized with quad-polarized C-Band and multispectral data and with co-polarized X-Band and multispectral data. The overall accuracy was up to 80% for unsupervised and up to 90% for supervised classifications. The results indicated that the shortwave co-polarized data show promise for the classification of tundra land cover since the polarimetric information is sensitive to low vegetation and the wetlands. Furthermore, co-polarized data provide a higher spatial resolution than the quad-polarized data.
The analysis of the intermediate digital elevation model data of the TanDEM-X showed a high potential for the characterization of the surface morphology. The basic and relative topographic features were shown to be of high relevance for the quantification of the surface morphology and an area-wide application is feasible. In addition, these data were of value for the classification and delineation of landforms. Such classifications will assist the delineation of geomorphological units and have potential to identify locations of actual and future morphologic activity.
Climate change assessment in Southeast Asia and implications for agricultural production in Vietnam
(2011)
For many years, the study of climatic changes and variations has become the main objective of climatic research, as has been appreciated in the IPCC's reports and several publications regarding climatic evolution on different space-time scales. Since the 80's, many research groups have generated the extensive database from which the analysis of temperature, precipitation and other climatic parameters has been performed on a global scale (Jones et al., 1986; Hansen and Lebedeff, 1987, 1988; Vinnikov et al., 1987, 1990). The most important result of these research projects is the evidence of global warming during the 20th century, especially in the last two decades. However, numerous challenges still exist about the structure and dimension of the climatic change on a considerable scale. Therefore, it is necessary to carry out studies on a local and regional scale that allow for a more precise evaluation of the global warming phenomenon. A statistical analysis approach was developed to identify systematic differences between large-scale climatic variable from the General Circulation Models (GCM), NCEP, CRU re-analysis data set and climatic parameters (temperature and precipitation data). Models are able to satisfactorily reproduce the spatial patterns of the regional temperature and precipitation field. The response of the climate system to various emission scenario simulated by the GCM was used to analyze and predict the local climate change. The main objective of this study is to analysis the time evolution of the annual and seasonal temperature and precipitation during the 21st century and in order to contribute to our knowledge of temperature and precipitation trends over the century on a regional scale, not only in Southeast Asia but also in Vietnam; the study focuses to develop a dynamical – statistical model describing the relationship between the major climate variation and agricultural production in Vietnam. This study will be an important contribution to the present-day assessment of climate change impacts in the low latitudes. Regional scenarios of climate change, including both rainfall and mean temperature were then used to assess the impact of climate change on crop production in the region in order to evaluate the vulnerability of the system to global warming. Climate change has adverse impacts on the socio - economic development of all nations. But the degree of the impact will vary across nations. It is expected that changes in the earth's climate will impact on developing countries like Vietnam, in particular, hardest because their economies are strongly dependent on crude forms of natural resources and their economic structure is less flexible to adjust to such drastic changes. In Chapter 1: Introduction and background I describe in general terms climate, climate change, climate change model with benefits and problems. Chapter 2: methodology discusses the methods including interpolation, validation, clustering, correlation and regression which were applied in the study. Chapter 3 and chapter 4 describe the database and study area. The most important is chapter 5 Results. The last is chapter 6 Conclusion and outlook followed by the reference list and an appendix.
The geologic barrier represents the final contact between a landfill and the environment. Ideally suited are clays and mudstones because of sufficient vertical and lateral extent, low hydraulic conductivities and high sorptive characteristics. Since hydraulic conductivity is no longer the single criteria to determine transport and retardation of contaminants in geologic landfill barrier materials, diffusive and sorptive characteristics of 4 different clay and mudstone lithologies in Northern Bavaria, were investigated. Cored samples from various depths were included in this study and subjected to evaluations of geochemistry, mineralogy, physical parameters, sorption and diffusion. A transient double reservoir with decreasing source concentration was designed and constructed using clear polycarbonate cylinders for undisturbed clay plugs of 2 to 4cm thickness. Samples were also fitted with internal electrical conductivity probes to determine the migration of the diffusive front. A multi chemical species synthetic landfill leachate was contrived to simulate and evaluate natural pollutant conditions. A computational method for determining mineralogy from geochemical data was also developed. It was found that sorptive processes are mostly controlled by the quality and type of fine grained phyllosilicates and the individual chemical species involved exhibited linear, Freundlich, as well as Langmuir sorption properties. Effective diffusion and sorption coefficients were also determined using POLLUTEv6 (GAEA, 1997) software and receptor reservoir concentrations for K, Na, Ca, Cu, NH4, Cl, NO3, SO4, and concentration totals at predetermined time intervals. Anion exclusion proved to be a major factor in the diffusion process and was used to explain many observed anomalies. Furthermore, diffusion coefficients were found not to be static with a multi chemical species leachate, but actually varied during the course of the experiment. Strong indications point toward the major role of pore space quality, shape, and form as control of diffusive properties of a geologic barrier. A correlation of CECNa of the samples with De may point to a possible deduction of diffusive properties for multi species leachates without extensive and time consuming laboratory tests
The glaciers in Norway exert a strong influence on Norwegian economy and society. Unlike many glaciers elsewhere and despite ongoing climate change and warming, many of them showed renewed advances and positive net mass changes in the 1980's and 1990's, followed by rapid retreats and mass losses since 2000. This difference in behaviour may be attributed to differences and shifts in the glaciological regime - the differences in the magnitude of impacts of climatic and non-climatic geographical factors on the glacier mass.
This study investigates the influence of various atmospheric variables on mass balance changes of a selection of glaciers in Norway by means of Pearson correlation analyses and cross-validated stepwise multiple regression analyses. The analyses are carried out for three time periods (1949-2008, 1949-1988, 1989-2008) separately in order to take into consideration the possible shift in the glaciological regime in the 1980's. The atmospheric variables are constructed from ERA40 and NCEP/NCAR re-analysis datasets and include regional means of seasonal air temperature and precipitation rates and atmospheric circulation indices. The multiple regression models trained in these time periods are then applied to predictors reconstructed from the CMIP3 climate model dataset to generate an estimate for mass changes from the year 1950 to 2100. The temporal overlap of estimates and observations is used for calibration. Finally, observed atmospheric states in seasons that are characterised by a particularly positive or negative mass balance are categorised into time periods of modelled climate by the application of a Bayesian classification procedure.
The strongest influence on winter mass balance is exerted by different indices of the North Atlantic Oscillation (NAO), Northern Annular Mode (NAM) and precipitation. The correlation coefficients and explained variances determined from the multiple regression analyses reveal an East-West gradient, suggesting a weaker influence of the NAO and NAM on glaciers underlying a more continental regime. The highest correlation coefficients and explained variances were obtained for the 1989-2008 time period, which might be due to a strong and predominantly positive phase of the NAO. Multi-model ensemble means of the estimates show a mass loss for all three eastern glaciers, while the estimates for the more maritime glaciers are ambivalent. In general, the estimates show a greater sensitivity to the training time period than to the greenhouse gas emission scenarios according to which the climates were simulated. The average net mass change by the end of 2100 is negative for all glaciers except for the northern Engabreen. For many glaciers, the Bayesian classification of observed atmospheric states into time periods of modelled climate reveals a decrease in probability of atmospheric states favouring extremes in winter, and an increase in probability of atmospheric states favouring extreme mass loss in summer for the distant future (2071-2100). This pattern of probabilities for the ablation season is most pronounced for glaciers underlying a continental and intermediate regime.
Grasslands shape many landscapes of the earth as they cover about one-third of its surface. They are home and provide livelihood for billions of people and are mainly used as source of forage for animals. However, grasslands fulfill many additional ecosystem functions next to fodder production, such as storage of carbon, water filtration, provision of habitats and cultural values. They play a role in climate change (mitigation) and in preserving biodiversity and ecosystem functions on a global scale. The degree to what these ecosystem functions are present within grassland ecosystems is largely determined by the management. Individual management practices and the use intensity influence the species composition as well as functions, like carbon storage, while higher use intensities (e.g. high mowing frequencies) usually show a negative impact. Especially in Central European countries, like in Germany, the determining influence of grassland management on its physiognomy and ecosystem functions leads to a large variability and small-scale alternations of grassland parcels. Large-scale information on the management and use intensity of grasslands is not available. Consequently, estimations of grassland ecosystem functions are challenging which, however, would be required for large-scale assessments of the status of grassland ecosystems and optimized management plans for the future. The topic of this thesis tackles this gap by investigating the major grassland management practice in Germany, which is mowing, for multiple years, in high spatial resolution
and on a national scale.
Earth Observation (EO) has the advantage of providing information of the earth’s surface on multi-temporal time steps. An extensive literature review on the use of EO for grassland management and production analyses, which was part of this thesis, showed that in particular research on grasslands consisting of small parcels with a large variety of management and use intensity, like common in Central Europe, is underrepresented. Especially
the launch of the Sentinel satellites in the recent past now enables the analyses of such grasslands due to their high spatial and temporal resolution. The literature review specifically on the investigation of grassland mowing events revealed that most previous studies focused on small study areas, were exploratory, only used one sensor type and/or lacked a reference data set with a complete range of management options.
Within this thesis a novel framework to detect grassland mowing events over large areas is presented which was applied and validated for the entire area of Germany for multiple years (2018–2021). The potential of both sensor types, optical (Sentinel-2) and Synthetic Aperture Radar (SAR) (Sentinel-1) was investigated regarding grassland mowing event detection. Eight EO parameters were investigated, namely the Enhanced Vegetation Index (EVI), the backscatter intensity and the interferometric (InSAR) temporal coherence for both available polarization modes (VV and VH), and the polarimetric (PolSAR) decomposition parameters Entropy, K0 and K1. An extensive reference data set was generated based on daily images of webcams distributed in Germany which resulted in mowing information
for grasslands with the entire possible range of mowing frequencies – from one to six in Germany – and in 1475 reference mowing events for the four years of interest.
For the first time a observation-driven mowing detection approach including data from Sentinel-2 and Sentinel-1 and combining the two was developed, applied and validated on large scale. Based on a subset of the reference data (13 grassland parcels with 44 mowing events) from 2019 the EO parameters were investigated and the detection algorithm
developed and parameterized. This analysis showed that a threshold-based change detection approach based on EVI captured grassland mowing events best, which only failed during periods of clouds. All SAR-based parameters showed a less consistent behavior to mowing events, with PolSAR Entropy and InSAR Coherence VH, however, revealing the
highest potential among them. A second, combined approach based on EVI and a SARbased parameter was developed and tested for PolSAR Entropy and InSAR VH. To avoid additional false positive detections during periods in which mowing events are anyhow reliably detected using optical data, the SAR-based mowing detection was only initiated
during long gaps within the optical time series (< 25 days). Application and validation of
these approaches in a focus region revealed that only using EVI leads to the highest accuracies (F1-Score = 0.65) as combining this approach with SAR-based detection led to a strong increase in falsely detected mowing events resulting in a decrease of accuracies (EVI + PolSAR ENT F1-Score = 0.61; EVI + InSAR COH F1-Score = 0.61).
The mowing detection algorithm based on EVI was applied for the entire area of Germany for the years 2018-2021. It was revealed that the largest share of grasslands with high mowing frequencies (at least four mowing events) can be found in southern/south-eastern Germany. Extensively used grassland (mown up to two times) is distributed within the entire country with larger shares in the center and north-eastern parts of Germany. These patterns stay constant in general, but small fluctuations between the years are visible. Early mown grasslands can be found in southern/south-eastern Germany – in line with high mowing frequency areas – but also in central-western parts. The years 2019 and 2020 revealed higher accuracies based on the 1475 mowing events of the multi-annual validation data set
(F1-Scores of 0.64 and 0.63), 2018 and 2021 lower ones (F1-Score of 0.52 and 0.50).
Based on this new, unprecedented data set, potential influencing factors on the mowing dynamics were investigated. Therefore, climate, topography, soil data and information on conservation schemes were related to mowing dynamics for the year 2020, which showed a high number of valid observations and detection accuracy. It was revealed that there are no strong linear relationships between the mowing frequency or the timing of the first mowing event and the investigated variables. However, it was found that for intensive grassland usage certain climatic and topographic conditions have to be fulfilled, while extensive grasslands appear on the entire spectrum of these variables. Further, higher mowing frequencies occur on soils with influence of ground water and lower mowing frequencies in protected areas. These results show the complex interplay between grassland mowing dynamics and external influences and highlight the challenges of policies aiming to protect grassland ecosystem functions and their need to be adapted to regional circumstances.