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A completely revised and enhanced version of the water balance model MODBIL of the regional water balance dynamics of Cyprus was developed for this study. The model is based on a physical, process-oriented, spatially distributed concept and is applied for the calculation of all important water balance components of the island for the time period of 1961-2004. The calibrated results are statistically analysed and visualised for the whole island area, and evaluated with respect to the renewability of natural water resources. Climate variability and changes of the past decades are analysed with regard to their influence on water balances. A further part of the study focusses on the simulation of impacts of potential climate change. The water balances are simulated under changing climatic conditions on the base of theoretical precipitation, temperature and relative humidity changes and the revealed impacts on the water balances and renewable resources are discussed. Furthermore, a first principal water balance scenario is developed for the assessment of the regional hydrological changes expected for Cyprus by the end of the 21st century. The scenarios are based on recently calculated climate change assessments for this part of the Mediterranean, under an assumed further increase of greenhouse gasses in the atmosphere.
Mit der vorliegenden Arbeit werden konventionelle thermische Kraftwerke an deutschen Flüssen identifiziert, bei denen aufgrund hoher Flusswassertemperaturen im Zusammenhang mit wasserrechtlichen Grenzwerten Leistungseinschränkungen auftraten. Weiterhin wird aufgezeigt, wie sich die Wassertemperaturen der Flüsse in der Vergangenheit (rezent) entwickelt haben und wie sie sich zukünftig im Kontext des Klimawandels entwickeln könnten.
Mittels Literaturrecherche, Medienanalyse und schriftlicher Befragung wurden konventionelle thermische Kraftwerke identifiziert, welche wassertemperaturbedingte Leistungseinschränkungen verzeichneten. Die meisten dieser Leistungseinschränkungen zwischen 1976 und 2007 zeigen sich bei großen Kraftwerken mit einer elektrischen Bruttoleistung über 300 Megawatt, bei Steinkohle- und Kernkraftwerken, bei Kraftwerken mit Durchlaufkühlung und bei solchen, die zwischen 1960 und 1990 in Betrieb gingen.
Trendanalysen interpolierter und homogenisierter, rezenter Wassertemperaturzeitreihen deutscher Flüsse ergeben positive Trends v. a. im Frühjahr und Sommer. Die Zählstatistik zeigt in den Jahren 1994, 2003 und 2006 die meisten Tage mit sehr hohen und extrem hohen Wassertemperaturen in den Sommermonaten. In diesen Jahren traten gleichzeitig 63 % aller identifizierter wassertemperaturbedingter Leistungseinschränkungen bei Kraftwerken, meist zwischen Juni und August, auf.
Für die Trendanalysen und den Mittelwertvergleich simulierter zukünftiger Wassertemperaturzeitreihen wurden drei Szenarien – B1, A1B und A2 sowie drei Zukunftsperioden 2011-2040, 2011/2041-2070, 2011/2071-2100 betrachtet. Es ergeben sich für die Zukunftsperiode 2011-2040 des A1B- oder A2-Szenarios in mindestens einem der Sommermonate eine Erwärmung und für das B1-Szenario negative oder keine Trends. Die mittleren Wassertemperaturen der Zukunftsperiode 2011-2040 zeigen in allen drei Szenarien gegenüber denen der Klimanormalperiode 1961-1990 positive Unterschiede in mindestens einem der Sommermonate. Für die beiden späteren Zukunftsperioden bis 2070 bzw. bis 2100 liegen in allen Wassertemperaturzeitreihen der drei Szenarien im Sommer positive Trends bzw. Differenzen gegenüber den mittleren Wassertemperaturen der Klimanormalperiode vor.
Durch die Synthese der drei Analysen ist erkennbar, dass Isar, Rhein, Neckar, Saar, Elbe und Weser die meisten Kraftwerksstandorte mit wassertemperaturbedingten Leistungseinschränkungen verzeichnen. Es zeigen sich hier positive Trends sowohl in den rezenten als auch zukünftigen Wassertemperaturen für die Zukunftsperiode 2011-2040 des A1B- und A2-Szenarios in jeweils mindestens einem der Sommermonate. Gegenüber den mittleren Wassertemperaturen der Klimanormalperiode liegen für alle drei Szenarien positive Unterschiede der Wassertemperaturen vor.
Bei einer Kraftwerkslaufzeit von 40-50 Jahren und einem Kernenergieausstieg 2022 bzw. 2034, werden 48-64 % bzw. 67-91 % der Kraftwerke mit wassertemperaturbedingten Leistungseinschränkungen bis 2022 bzw. 2034 außer Betrieb gehen. Bei einer Laufzeitverlängerung würden nach 2022 fünf der elf betroffenen Kernkraftwerke weiter am Netz bleiben. Somit kann es wieder zu wassertemperaturbedingten Leistungseinschränkungen kommen. In Deutschland sind nach wie vor große Kraftwerke an Flüssen geplant. Deren Kühlsysteme müssen entsprechend ausgewählt und konstruiert werden, um der zu erwartenden Erhöhung der Flusstemperaturen Rechnung zu tragen.
The global-local sustainable development and climate change adaptation policy, and the emerging political discourse on the value of local Adaptation, have positioned the local institutions and their governance space within the strategic enclaves of multilevel governance system. Such shifts have transformed the context for sustainable Nature Based Tourism (NBT) development and adaptation in Nepal in general, and its protected areas, in particular. The emerging institutional adaptation discourse suggests on the need to link tourism development, adaptation and governance within the sustainability concept, and also to recognize the justice and inclusive dimensions of local adaptation. However, sociological investigation of institutional adaptation, particularly at the interface between sustainability, justice and inclusive local adaptation is an undertheorized research topic.
This exploratory study examined the sociological process of the institutional adaptation, especially the social resilience and adaptive governance capacities of the NBT institutions, in 7 Village Development Committees of the Mustang district, a popular destination in the Annapurna Conservation Area, Nepal. Using the sphere (a dynamic social space concept) and quality of governance as the analytical framework, the integrative adaptation as the methodological approach and the case study action research method, the study investigated and generated a holistic picture on the state of the social resilience and adaptive governance capacities of the NBT institutions.
The findings show institutional social resilience capacities to be contingent on socio-political construction of adaptation knowledge and power. Factors influencing such constructions among NBT institutions include: the site and institutions specific political, economic and environmental dispositions; the associated socio-political processes of knowledge constructions and volition action; and the social relationships and interaction, operating within the spheres and at multiple governance levels. The adaptive governance capacities hinge on the institutional arrangements, the procedural aspects of adaptation governance and the governmentality. These are reflective of the diverse legal frameworks, the interiority perspective of the decision making and governance practices of the NBT institutions.
In conclusion, it is argued that effective local adaptation in the Mustang district is contingent on the adaptation and institutional dynamics of the NBT institutions, consisting of the cognitive, subjective, process and procedural aspects of the adaptation knowledge production and its use.
Spatiotemporal dynamics of freshwater macrophytes in Bavarian lakes under environmental change
(2022)
Macrophytes are key components of freshwater ecosystems because they provide habitat, food, and improve the water quality. Macrophyte are vulnerable to environmental change as their physiological processes depend on changing environmental factors, which themselves vary within a geographical region and along lake depth. Their spatial distribution is not well understood and their importance is publicly little-known. In this thesis, I have investigated the spatiotemporal dynamics of freshwater macrophytes in Bavarian lakes to understand their diversity pattern along different scales and to predict and communicate potential consequences of global change on their richness.
In the introduction (Chapter 1), I provide an overview of the current scientific knowledge of the species richness patterns of macrophytes in freshwater lakes, the influences of climate and land-use change on macrophyte growth, and different modelling approaches of macrophytes.
The main part of the thesis starts with a study about submerged and emergent macrophyte species richness in natural and artificial lakes of Bavaria (Chapter 2). By analysing publicly available monitoring data, I have found a higher species richness of submerged macrophytes in natural lakes than in artificial lakes. Furthermore, I showed that the richness of submerged species is better explained by physio-chemical lake parameters than the richness of emergent species. In Chapter 3, I considered that submerged macrophytes grow along a depth gradient that provides a sharp environmental gradient on a short spatial scale. This study is the first comparative assessment of the depth diversity gradient (DDG) of macrophytes. I have found a hump-shaped pattern of different diversity components. Generalised additive mixed-effect models indicate that the shape of the DDG is influenced mainly by light quality, light quantity, layering depth, and lake area. I could not identify a general trend of the DDG within recent years, but single lakes show trends leading into different directions. In Chapter 4, I used a mechanistic eco-physiological model to explore changes in the distribution of macrophyte species richness under different scenarios of environmental conditions across lakes and with depths. I could replicate the hump-shaped pattern of potential species richness along depth. Rising temperature leads to increased species richness in all lake types, and depths. The effect of turbidity and nutrient change depends on depth and lake type. Traits that characterise “loser species” under increased turbidity and nutrients are a high light consumption and a high sensibility to disturbances. “Winner species” can be identified by a high biomass production. In Chapter 5, I discuss the image problem of macrophytes. Unawareness, ignorance, and the poor accessibility of macrophytes can lead to conflicts of use. I assumed that an increased engagement and education could counteract this. Because computer games can transfer knowledge interactively while creating an immersive experience, I present in the chapter an interactive single-player game for children.
Finally, I discuss the findings of this thesis in the light of their implications for ecological theory, their implications for conservation, and future research ideas (Chapter 6). The findings help to understand the regional distribution and the drivers of macrophyte species richness. By applying eco-physiological models, multiple environmental shaping factors for species richness were tested and scenarios of climate and land-use change were explored.
The discontinuous mountain permafrost zone is characterized by its heterogeneous distribution of frozen ground and a small-scale variability of the ground thermal regime. Large parts of these areas are covered by glacial till and sediments that were exposed after the recession of the glaciers since the 19th century. As response to changed climatic conditions permafrost-affected areas will lose their ability as sediment storage and on the contrary, they will act as source areas for unconsolidated debris. Along with modified precipitation patterns the degradation of the discontinuous mountain permafrost zone will (temporarily)
increase its predisposition for mass movement processes and thus has to be monitored in a differentiated way.
Therefore, the spatio-temporal dynamics of frozen ground are assessed in this study based on results obtained in three glacier forefields in the Engadin (Swiss Alps) and at the Zugspitze (German Alps). Sophisticated techniques are required to uncover structural differences in the subsurface. Thus, the applicability of advanced geophysical methods is tested for alpine environments and proved by the good 3D-delineation of a permafrost body and by the detection of detailed processes in the active layer during snow melt. Electrical resistivity tomography (ERT) approaches (quasi-3D, daily monitoring) reveal
their capabilities to detect subsurface resistivity changes both, in space and time. Processes and changes in regard to liquid water content and ice content are observed to exist at short distances even though the active layer is not subject to a considerable thickening
over the past 7 years. The stability of the active layer is verified by borehole temperature data. No synchronous
trend is recognized in permafrost temperatures and together with multi-annual electrical resistivity data they indicate degradation and aggradation processes to occur at the same time. Different heat transfer mechanisms, especially during winter, are recognized by means of temperature sensors above, at, and beneath the surface. Based on surface and borehole temperature data the snow cover is assessed as the major controlling factor for the thermal regime on a local scale. Beyond that, the debris size of the substrate, which modifies the snow cover and regulates air exchange processes above the ground, plays a crucial role as an additional buffer layer. A fundamental control over the stability of local permafrost patches is attributed to the ice-rich transient layer at the base of the active layer. The refreezing of melt water in spring is illustrated with diurnal ERT monitoring data from glacier forefield Murtèl.
Based on these ERT and borehole temperature data a conceptual model of active layer processes between autumn and spring is developed. The latent heat that is inherent in the transient layer protects the permafrost beneath from additional energy input from the surface as long as the refreezing of melt water in spring prevails and sufficient ice is build up each spring. Permafrost sites without a transient layer show considerably higher
temperatures at their table and are more prone to degradation in the years and decades ahead. As main investigation area a glacier forefield beneath the summits of Piz Murtèl and Piz Corvatsch in the Swiss Engadin was chosen. It is located west of the well-known
rock glacier Murtèl. Here, a permafrost body inside and adjacent to the lateral moraine was investigated and could be delineated very well. In the surrounding glacier forefield no further indications of permafrost occurrence could be made. Geophysical data and temperature values from the surface and from a permafrost borehole were compared with long-term data from proximate glacier forefield Muragl (Engadin). Results from both
sites show a considerable stability of the active layer depth in summer while at the same time geophysical data demonstrate annual changes in the amount of liquid water content and ice content in the course of years.
A third investigation area is located in the German Alps. The Zugspitzplatt is a high mountain valley with considerably more precipitation and thicker snow cover compared to both Swiss sites. In close proximity to the present glacier and at a large talus slope beneath the summit crest ground ice could be observed. The high subsurface resistivity values and comparable data from existing studies at the Zugspitze may indicate the presence of sedimentary ice in the subsurface of the karstified Zugspitzplatt. Based on these complementary data from geophysical and temperature measurements as
well as geomorphological field mapping the development of permafrost in glacier forefields under climate change conditions is analyzed with cooperation partners from the SPCC project. Ground temperature simulations forced with long-term climatological data are modeled to assess future permafrost development in glacier forefield Murtèl. Results suggest that permafrost is stable as long as the ice-rich layer between the active layer and
the permafrost table exists. After a tipping point is reached, the disintegration of frozen ground starts to proceed rapidly from the top.
Das Tibetplateau (TP) ist das höchste Gebirgsplateau der Erde und bildete sich im Verlauf der letzten 50 Millionen Jahre. Durch seine Ausmaße veränderte das TP nicht nur das Klima im heutigen Asien, sondern bewirkte Veränderungen weltweit. Heute stellt das TP einen Hotspot des Klimawandels dar und ist als Quellgebiet vieler großer Flüsse in Asien für die Wasserversorgung von Milliarden von Menschen von zentraler Bedeutung. Vor diesem Hintergrund ist es wichtig, die Prozesse, die das Klima in der Region steuern, besser zu verstehen und die Variabilität des Klimas auf unterschiedlichen Zeitskalen abschätzen zu können.
Grundlegendes Ziel der vorliegenden Arbeit ist es, räumlich hochaufgelöste quantitative Informationen über die Veränderung der klimatischen Verhältnisse in Asien während der Bildungsphase des TP und unter warm- und kaltzeitlichen Randbedingungen zur Verfügung zu stellen und dadurch eine Verbindung zwischen den verschiedenen Zeitskalen herzustellen. Hierfür werden das heutige Klima und das Paläoklima der Region mit Hilfe von Klimamodellen simuliert. Da frühere Studien zeigen konnten, dass die Ergebnisse von hochaufgelösten Modellen besser mit Paläoklimarekonstruktionen übereinstimmen, als die von vergleichsweise niedrig aufgelösten Globalmodellen, erfolgt ein dynamisches Downscaling des globalen Klimamodells ECHAM5 mit dem regionalen Klimamodell REMO.
Die Heraushebung des TP wird durch eine Serie von fünf Simulationen (Topogra- phieexperimente) approximiert, in denen die Höhe des TP in 25%-Schritten von 0% bis 100% der heutigen Höhe verändert wird. Die Schwankungen des Klimas im spä- ten Quartär sind durch Simulationen für das mittlere Holozän und den Hochstand der letzten Vereisung, das Last-Glacial-Maximum, repräsentiert (Quartärexperi- mente). In den Quartärexperimenten wurden die Treibhausgaskonzentrationen, Orbitalparameter, Landbedeckung und verschiedene Vegetationsparameter an die Bedingungen der jeweiligen Zeitscheibe angepasst. Die Auswertung der Simulati- onsergebnisse konzentriert sich auf jährliche und jahreszeitliche Veränderungen der bodennahen Temperatur und des Niederschlags. Außerdem werden die sich erge- benden Änderungen in der Intensität des indischen Monsuns anhand verschiedener Monsunindizes analysiert. Für das TP und die sich unmittelbar anschließenden Ge- biete wird zusätzlich eine Clusteranalyse durchgeführt, um die dort vorkommenden regionalen Klimatypen identifizieren und charakterisieren zu können.
In den Topographieexperimenten zeigt sich, dass die 2m-Temperatur im Bereich des TP im Jahresmittel mit abnehmender Höhe des Plateaus um bis zu 30◦C zunimmt, während es in den übrigen Teilen des Modellgebiets nahezu überall kälter wird. Die Jahressumme des Niederschlags nimmt mit abnehmender Höhe des TP westlich und nördlich davon zu. Im Bereich des TP sowie südlich und östlich davon gehen die Niederschläge zurück. Die starke Niederschlagszunahme nördlich des TP kann durch die Ausbildung eines Höhentrogs statt eines Höhenrückens in diesem Bereich erklärt werden. Das grundsätzliche räumliche Muster der Veränderungen besteht dabei bereits bei einer Plateauhöhe von 75% des Ausgangswertes und ändert sich bei weiterer Verringerung der Höhe nicht wesentlich. Lediglich der Betrag der Veränderungen nimmt zu. Dies gilt für die 2m-Temperatur und den Niederschlag und sowohl im Jahresmittel als auch für die einzelnen Jahreszeiten. Bezüglich der Intensität des indischen Sommermonsuns zeigt sich, dass zwischen 25% und 75% der heutigen Höhe des TP die stärkste Intensivierung stattfindet. Eine mit heute vergleichbare Monsunintensität tritt erst auf, wenn das TP die Hälfte seiner jetzigen Höhe erreicht hat.
Im mittleren Holozän ist es im Jahresmittel in den meisten Teilen des Modellge- biets kälter und feuchter als heute. Die Unterschiede sind jedoch größtenteils gering und nicht signifikant. Hinsichtlich der Temperatur zeigen die Modelldaten nur vereinzelt eine gute Übereinstimmung mit den rekonstruierten Werten. Allerdings weisen die Rekonstruktionen eine hohe räumliche Variabilität auf, wodurch die in diesem Datensatz vorhandenen Unsicherheiten widergespiegelt werden. Hinsicht- lich des Niederschlags ist die Übereinstimmung besser. Hier deuten sowohl die simulierten als auch die rekonstruierten Daten auf feuchtere Bedingungen hin.
In der Simulation für das Last-Glacial-Maximum liegen die Temperaturen überall im Modellgebiet im Jahresmittel und in allen Jahreszeiten um bis zu 8◦C unter den heutigen Werten. Es besteht eine gute Übereinstimmung mit den rekonstruierten Temperaturwerten für diese Zeitscheibe. Zu einer signifikanten Abnahme der jährlichen Niederschlagsmenge kommt es westlich und nordwestlich des TP, in Indien, Südostasien und entlang der Ostküste Chinas. Für die Bereiche, für die Niederschlagsrekonstruktionen verfügbar sind, stimmen die Modellergebnisse gut mit diesen überein. Zu einer signifikanten Niederschlagszunahme kommt es nur zwischen der Nordküste des Golfs von Bengalen und dem Himalaya, wobei dies möglicherweise ein Modellartefakt darstellt.
Hinsichtlich der Monsunintensität bestehen große Unterschiede zwischen den Indizes. Während der Extended Indian Monsoon Rainfall Index eine starke Ab- schwächung des indischen Sommermonsuns anzeigt, ist der Wert des Webster and Yang Monsoon Index verglichen mit heute nahezu unverändert. Ein Vergleich der Monsunintensität in den Topographie- und den Quartärexperimenten macht deut- lich, dass der indische Monsun durch den Wechsel von warm- und kaltzeitlichen Randbedingungen mindestens so stark beeinflusst wird wie durch die Hebung des TP.
In the scope of climate warming and the increase in frequency and intensity of severe heat waves in Central Europe, identification of temperate tree species that are suited to cope with these environmental changes is gaining increasing importance. A number of tree physiological characteristics are associated with drought-stress resistance and survival following severe heat, but recent studies have shown the importance of plant hydraulic and anatomical traits for predicting drought-induced tree mortality, such as vessel diameter, and their potential to predict species distribution in a changing climate.
A compilation of large global datasets is required to determine traits related to drought-induced embolism and test whether embolism resistance can be determined solely by anatomical traits. However, most measurements of plant hydraulic traits are labour-intense and prone to measurement artefacts. A fast, accurate and widely applicable technique is necessary for estimating xylem embolism resistance (e.g., water potential at 50% loss of conductivity, P50), in order to improve forecasts of future forest changes. These traits and their combination must have evolved following the selective pressure of the environmental conditions in which each species occurs. Describing these environmental-trait relationships can be useful to assess potential responses to environmental change and mitigation strategies for tree species, as future warmer temperatures may be compounded by drier conditions.
Glacier outlines during the ‘Little Ice Age’ maximum in Jotunheimen were mapped by using remote sensing techniques (vertical aerial photos and satellite imagery), glacier outlines from the 1980s and 2003, a digital terrain model (DTM), geomorphological maps of individual glaciers, and field-GPS measurements. The related inventory data (surface area, minimum and maximum altitude) and several other variables (e.g. slope, range) were calculated automatically by using a geographical information system. The length of the glacier flowline was mapped manually based on the glacier outlines at the maximum of the ‘Little Ice Age’ and the DTM. The glacier data during the maximum of the ‘Little Ice Age’ were compared with the Norwegian glacier inventory of 2003. Based on the glacier inventories during the maximum of the ‘Little Ice Age’, the 1980s and 2003, a simple parameterization after HAEBERLI & HOELZLE (1995) was performed to estimate unmeasured glacier variables, as e.g. surface velocity or mean net mass balance. Input data were composed of surface glacier area, minimum and maximum elevation, and glacier length. The results of the parameterization were compared with the results of previous parameterizations in the European Alps and the Southern Alps of New Zealand (HAEBERLI & HOELZLE 1995; HOELZLE et al. 2007). A relationship between these results of the inventories and of the parameterization and climate and climate changes was made.
The topic of the present study focuses on landslide susceptibility assessment in the Northern Vienna Forest by GIS-based, statistic-probabilistic and deterministic modelling. The study is based on two complementary approaches for integrated landslide susceptibility assessment, which is not limited to one single methodology and its inherent assumptions.
A statistic-probabilistic method is applied to the whole region of the Northern Vienna Forest. This regional model investigates the basic disposition for landslides under consideration of controlling factors, which are persistent and more or less constant over time. A deterministic method is applied on a larger scale in a sub-study site of the Hagenbach Valley. These detailed models aim to investigate the variable disposition as a function of substrate wetness, which is in turn dependent on meteorological conditions. A main aspect of the work is the development of various wetness scenarios, which consider short-term weather phenomena, like heavy or long-lasting rainfall, but which also investigate the influence of meteorological and climate conditions on slope stability, which may vary in mid-term and long-term.
Furthermore, the assessment of the effects of climate change on the disposition for landslides is a major aspect of the study. Hence, average changes in air temperature and precipitation as predicted by Regional Climate Models are incorporated into modelling. In this context, it is tested whether changes in substrate wetness and thus in slope stability can be identified and quantified as a consequence of changed climate conditions.
As further objective shallow slope movements are incorporated into disposition modelling. According to geomorphological and sedimentological studies, these quaternary sediments are essential for slope formation in the Vienna Forest. In general, it is assumed that landslides primarily occur in weathered flysch sandstones rich in marl. Field-based surveys, however, identified shallow landslide activity in the quaternary sediments covering the flysch bedrock in wide areas. Therefore, the influence of these sediments on slope dynamics is studied in the present work within GIS-based slope stability models.
The results of the statistic-probabilistic landslide susceptibility assessment provide information on the basic disposition of the Northern Vienna Forest for landslides. The resulting regional susceptibility map reveals that the Northern Zone, a tectonic unit in the north of the study area, has extensive areas with the highest degree of landslide susceptibility. In this overthrust area in transition to the Molasse Zone there are geological units which are highly susceptible to landslides. The “Wolfpassing Formation” and the “Calcareous Klippen” of the Northern Zone show significant landslide densities. These geological zones start in the north near St. Andrä-Wördern and continue in south-western direction along the ridges of Tulbinger Kogel, Klosterberg, Frauenberg, and Eichberg.
Statistical weighting carried out in the course of regional landslide susceptibility assessment provides information on the spatial relation between landslide processes and specific controlling factors. The modelling highlights the relevance of zones rich in clay within the flysch formations as controlling geofactor. The highest landslide susceptibility is calculated for the geological units, which contain layers of Gaultflysch rich in clay and shale. Furthermore, a close correlation between the distribution of landslides on the one hand and the spatial distribution of the fault system and nappe boundaries on the other hand is ascertained. Hence, the tectonic conditions can be seen as crucial controlling geofactor for landslide activity in the study area. In the proximity of drainage lines an increased landslide frequency is revealed. In combination with heavy rainfall, torrential discharge can occur in creeks and may cause instabilities in adjacent hillslopes. In addition, the model documents an enhancement of landslide susceptibility on north-west facing slopes. In comparison to meteorological data it is obvious that the north-west exposition corresponds to the prevailing wind direction of the study area. Therefore, north-west facing slopes might be exposed to enhanced advective rainfall amounts, which can increase substrate wetness and thus landslide susceptibility. The latter geofactors indicate the significance of meteorological and hydrological conditions for the occurrence of landslides in the study area.
As described above, the regional assessment is based on controlling factors that are persistent over a long period of time and can therefore be considered as constant. On the contrary, the large-scale, physically based deterministic modelling investigates the disposition for landslides under variable humidity conditions in the substrate. In conclusion it can be stated that the disposition for slope instability is strongly varying in dependence of the humidity conditions in the substrate. A heavy rainfall event causes a drastic reduction of stable areas by 23% compared to monthly average wetness conditions in summer (July). In summary the wetness scenarios demonstrate, that apart from short-term weather conditions, like long-lasting or heavy rainfall, the long-term-development of substrate moisture has impact on slope stability. The more persistent, seasonally fluctuating wetness conditions show measureable influence on slope stability: As a consequence of increased topographic wetness in the winter month February there is an increase of instable areas by 5% in comparison with the summer month July. The modelling further revealed that quaternary sediments are more moisture sensitive and the influence of changing wetness conditions is stronger in these layers than in the bedrock.
The results of modelling, which are based on climate change, indicate that a moderate change of slope stability on a monthly average is possible in comparison to the conditions of the climate normal period. An assumed average monthly temperature increase of 2°C in combination with a precipitation increase of 30% in the winter months lead to an augmentation of recharge of 7% in the model in comparison with the long-term average conditions. Due to this increased recharge, there is a slight increase of topographic wetness in the model. This wetness augmentation results in an extension of instable slope areas by 3% and a reduction of the stable slope areas proportional to this extension. This slightly increased instability reduces critical triggering thresholds for single rainfall events meaning that even lower precipitation amounts or intensities can cause instabilities.
In contrast to the winter months, the incorporation of forecasted climate change into the modelling reveals a reduction of instable slope areas in favour of stable areas in the summer scenario. The forecasted average air temperature increase of 2.5°C in combination with a reduction of the average monthly precipitation amount of 15% drastically decreases substrate moisture. Consequently, instable slope areas are reduced by 11% of the study area. This effect on slope stability in the model mainly results from the reduced monthly rainfall amounts, but also from increased evapotranspiration as a consequence of the increased air temperature causing reduced recharge amounts. However, in spite of the monthly decrease of precipitation amounts, precipitation intensities are probable to rise according to climate studies. In this context the results of the modelling indicate, that a drastic, short-term increase of landslide disposition due to heavy rainfall events has to be expected more frequently in summer.
The results of the complementary methods are then assembled. Based on this synthesis the following conclusion can be drawn: The regional landslide susceptibility assessment yields that hillslopes with an inclination of 26° to 31° are highly landslide prone. The physically based models indicate that in this slope gradient range the presence of quaternary sediments is of major importance for landslides. Therefore, it can be concluded that a considerable portion of known landslides mapped in flysch actually occurred in quaternary sediments.
Environmental interlinked problems such as human-induced land cover change, water scarcity, loss in soil fertility, and anthropogenic climate change are expected to affect the viability of agriculture and increase food insecurity in many developing countries. Climate change is certainly the most serious of these challenges for the twenty-first century. The poorest regions of the world – tropical West Africa included – are the most vulnerable due to their high dependence on climate and weather sensitive activities such as agriculture, and the widespread poverty that limits the institutional and economic capacities to adapt to the new stresses brought about by climate change. Climate change is already acting negatively on the poor smallholders of tropical West Africa whose livelihoods dependent mainly on rain-fed agriculture that remains the cornerstone of the economy in the region. Adaptation of the agricultural systems to climate change effects is, therefore, crucial to secure the livelihoods of these rural communities. Since information is a key for decision-making, it is important to provide well-founded information on the magnitude of the impacts in order to design appropriate and sustainable adaptation strategies.
Considering the case of agricultural production in the Republic of Benin, this study aims at using large-scale climatic predictors to assess the potential impacts of past and future climate change on agricultural productivity at a country scale in West Africa. Climate signals from large-scale circulation were used because state-of-the art regional climate models (RCM) still do not perfectly resolve synoptic and mesoscale convective processes. It was hypothesised that in rain-fed systems with low investments in agricultural inputs, yield variations are widely governed by climatic factors. Starting with pineapple, a perennial fruit crops, the study further considered some annual crops such as cotton in the group of fibre crops, maize, sorghum and rice in the group of cereals, cowpeas and groundnuts belonging to the legume crops, and cassava and yams which are root and tuber crops. Thus the selected crops represented the three known groups of photosynthetic pathways (i.e. CAM, C3, and C4 plants).
In the study, use was made of the historical agricultural yield statistics for the Republic of Benin, observed precipitation and mean near-surface air temperature data from the Climatic Research Unit (CRU TS 3.1) and the corresponding variables simulated by the regional climate model (RCM) REMO. REMO RCM was driven at its boundaries by the global climate model ECHAM 5. Simulations with different greenhouse gas concentrations (SRES-A1B and B1 emission scenarios) and transient land cover change scenarios for present-day and future conditions were considered. The CRU data were submitted to empirical orthogonal functions analysis over the north hemispheric part of Africa to obtain large-scale observed climate predictors and associated consistent variability modes. REMO RCM data for the same region were projected on the derived climate patterns to get simulated climate predictors. By means of cross-validated Model Output Statistics (MOS) approach combined with Bayesian model averaging (BMA) techniques, the observed climate predictors and the crop predictand were further on used to derive robust statistical relationships. The robust statistical crop models perform well with high goodness-of-fit coefficients (e.g. for all combined crop models: 0.49 ≤ R2 ≤ 0.99; 0.28 ≤ Brier-Skill-Score ≤ 0.90).
Provided that REMO RCM captures the main features of the real African climate system and thus is able to reproduce its inter-annual variability, the time-independent statistical transfer functions were then used to translate future climate change signal from the simulated climate predictors into attainable crop yields/crop yield changes. The results confirm that precipitation and air temperature governed agricultural production in Benin in general, and particularly, pineapple yield variations are mainly influenced by temperature. Furthermore, the projected yield changes under future anthropogenic climate change during the first-half of the 21st century amount up to -12.5% for both maize and groundnuts, and -11%, -29%, -33% for pineapple, cassava, and cowpeas respectively. Meanwhile yield gain of up to +10% for sorghum and yams, +24% for cotton, and +39% for rice are expected. Over the time period 2001 – 2050, on average the future yield changes range between -3% and -13% under REMO SRES–B1 (GHG)+LCC, -2% and -11% under REMO SRES–A1B (GHG only),and -3% and -14% under REMO SRES–A1B (GHG)+LCC for pineapple, maize, sorghum, groundnuts, cowpeas and cassava. In the meantime for yams, cotton and rice, the average yield gains lie in interval of about +2% to +7% under REMO SRES–B1 (GHG)+LCC, +0.1% and +12% under REMO SRES–A1B (GHG only), and +3% and +10% under REMO SRES–A1B (GHG)+LCC. For sorghum, although the long-term average future yield depicts a reduction there are tendencies towards increasing yields in the future. The results also reveal that the increases in mean air temperature more than the changes in precipitation patterns are responsible for the projected yield changes. As well the results suggest that the reductions in pineapple yields cannot be attributed to the land cover/land use changes across sub-Saharan Africa. The production of groundnuts and in particular yams and cotton will profit from the on-going land use/land cover changes while the other crops will face detrimental effects.
Henceforth, policymakers should take effective measures to limit the on-going land degradation processes and all other anthropogenic actions responsible for temperature increase. Biotechnological improvement of the cultivated crop varieties towards development of set of seed varieties adapted to hotter and dry conditions should be included in the breeding pipeline programs. Amongst other solutions, application of appropriate climate-smart agricultural practices and conservation agriculture are also required to offset the negative impacts of climate change in agriculture.
This thesis on the “Impacts of extreme hydro-meteorological events on electricity generation and possible adaptation measures – a GIS-based approach for corporate risk management and enhanced climate mitigation concepts in Germany” presents an identification of hydro-meteorological extreme events in Germany and their effects on electricity generating units, i.e. on conventional thermal and nuclear power plants as well as on installations of the renewable energies of hydropower, wind energy and photovoltaic installations. In addition, adaptation measures and strategies are named that help power plant operators to prepare for a changing climate. Due to the different requirements of large facility operators and local planners and owners of renewable energies, the work contains the two approaches of corporate risk management and climate mitigation concepts. A changing climate not only consists of a shift in mean values of weather parameters such as global and regional air temperature and precipitation, but may also result in more frequent and more severe single events such as extreme precipitation, tornadoes and thunderstorms. In two case studies, these findings are implemented into an adjusted general risk management structure. This is enhanced by the use of Geographical Information Systems (GIS) to accomplish a localisation of events and infrastructure. The first example gives insight into the consequences of ice throw from wind turbines and how climate mitigation concepts can act as a framework for an adapted, sustainable energy planning. The second example on the other hand highlights a GIS-based flood risk management for thermal power plants and the benefits of an adjusted corporate risk management cycle. The described approach leads to an integrated management of extreme hydro-meteorological events at power plant site respectively district level by combining two cycles of site-related and local planning in addition to GIS-based analyses. This is demonstrated as an example by the comparison of two districts in Germany. The practical outcome is a comprehensive support for decision-making processes.
Chapter 1 – General introduction
Anthropogenic land-use and climate change are the major drivers of the global biodiversity loss. Yet, biodiversity is essential for human well-being, as we depend on the availability of potable water, sufficient food and further benefits obtained from nature. Each species makes a somewhat unique contribution to these ecosystem services. Furthermore, species tolerate environmental stressors, such as climate change, differently. Thus, biodiversity is both the "engine" and the "insurance" for human well-being in a changing climate. Here, I investigate the effects of temperature and land use on herbivory (Chapter 2), predation (Chapter 3) and pest control (Chapter 4), and at the same time identify features of habitats (e.g. plant richness, proximity to different habitat types) and landscapes (e.g. landscape diversity, proportion of oilseed rape area) as potential management targets in an adaptation strategy to climate change. Finally, I discuss the similarities and differences between factors influencing herbivory, predation and pest control, while placing the observations in the context of climate change as a multifaceted phenomenon, and highlighting starting points for sustainable insect pest management (Chapter 5).
Chapter 2 – Plant richness, land use and temperature differently shape invertebrate leaf-chewing herbivory on major plant functional groups
Invertebrate herbivores are temperature-sensitive. Rising temperatures increase their metabolic rates and thus their demand for carbon-rich relative to protein-rich resources, which can lead to changes in the diets of generalist herbivores. Here, we quantified leaf-area loss to chewing invertebrates among three plant functional groups (legumes, non-leguminous forbs and grasses), which largely differ in C:N (carbon:nitrogen) ratio. This reseach was conducted along spatial temperature and land-use gradients in open herbaceous vegetation adjacent to different habitat types (forest, grassland, arable field, settlement). Herbivory largely differed among plant functional groups and was higher on legumes than forbs and grasses, except in open areas in forests. There, herbivory was similar among plant functional groups and on legumes lower than in grasslands. Also the presence of many plant families lowered herbivory on legumes. This suggests that open areas in forests and diverse vegetation provide certain protection against leaf damage to some plant families (e.g. legumes). This could be used as part of a conservation strategy for protected species. Overall, the effects of the dominant habitat type in the vicinity and diverse vegetation outweighed those of temperature and large-scale land use (e.g. grassland proportion, landscape diversity) on herbivory of legumes, forbs and grasses at the present time.
Chapter 3 – Landscape diversity and local temperature, but not climate, affect arthropod predation among habitat types
Herbivorous insects underlie top-down regulation by arthropod predators. Thereby, predation rates depend on predator community composition and behaviour, which is shaped by temperature, plant richness and land use. How the interaction of these factors affects the regulatory performance of predators was unknown. Therefore, we assessed arthropod predation rates on artificial caterpillars along temperature, and land-use gradients. On plots with low local mean temperature (≤ 7°C) often not a single caterpillar was attacked, which may be due to the temperature-dependent inactivity of arthropods. However, multi-annual mean temperature, plant richness and the dominant habitat type in the vicinity did not substantially affect arthropod predation rates. Highest arthropod predation rates were observed in diverse landscapes (2-km scale) independently of the locally dominanting habitat type. As landscape diversity, but not multi-annual mean temperature, affected arthropod predation rates, the diversification of landscapes may also support top-down regulation of herbivores independent of moderate increases of multi-annual mean temperature in the near future.
Chapter 4 – Pest control and yield of winter oilseed rape depend on spatiotemporal crop-cover dynamics and flowering onset: implications for global warming
Winter oilseed rape is an important oilseed crop in Europe, yet its seed yield is diminished through pests such as the pollen beetle and stem weevils. Damage from pollen beetles depends on pest abundances, but also on the timing of infestation relative to crop development as the bud stage is particularly vulnerable. The development of both oilseed rape and pollen beetles is temperature-dependent, while temperature effects on pest abundances are yet unknown, which brings opportunities and dangers to oilseed rape cropping under increased temperatures. We obtained measures of winter oilseed rape (flowering time, seed yield) and two of its major pests (pollen beetle, stem weevils) for the first time along both land-use and temperature gradients. Infestation with stem weevils was not influenced by any temperature or land-use aspect considered, and natural pest regulation of pollen beetles in terms of parasitism rates of pollen beetle larvae was low (< 30%), except on three out of 29 plots. Nonetheless, we could identify conditions favouring low pollen beetle abundances per plant and high seed yields. Low pollen beetle densities were favoured by a constant oilseed rape area relative to the preceding year (5-km scale), whereas a strong reduction in area (> 40%) caused high pest densities (concentration effect). This occurred more frequently in warmer regions, due to drought around sowing, which contributed to increased pollen beetle numbers in those regions. Yet, in warmer regions, oilseed rape flowered early, which possibly led to partial escape from pollen beetle infestation in the most vulnerable bud stage. This is also suggested by higher seed yields of early flowering oilseed rape fields, but not per se at higher temperatures. Thus, early flowering (e.g. cultivar selection) and the interannual coordination of oilseed rape area offer opportunities for environmental-friendly pollen beetle management.
Chapter 5 – General discussion
Anthropogenic land-use and climate change are major threats to biodiversity, and consequently to ecosystem functions, although I could show that ecosystem functions such as herbivory and predation barely responded to temperature along a spatial gradient at present time. Yet, it is important to keep several points in mind: (i) The high rate of climate warming likely reduces the time that species will have to adapt to temperature in the future; (ii) Beyond mean temperatures, many aspects of climate will change; (iii) The compensation of biodiversity loss through functional redundancy in arthropod communities may be depleted at some point; (iv) Measures of ecosystem functions are limited by methodological filters, so that changes may be captured incompletely. Although much uncertainty of the effects of climate and land-use change on ecosystem functions remains, actions to halt biodiversity loss and to interfere with natural processes in an environmentally friendly way, e.g. reduction of herbivory on crops, are urgently needed. With this thesis, I contribute options to the environment-friendly regulation of herbivory, which are at least to some extent climate resilient, and at the same time make a contribution to halt biodiversity loss. Yet, more research and a transformation process is needed to make human action more sustainable. In terms of crop protection, this means that the most common method of treating pests with fast-acting pesticides is not necessarily the most sustainable. To realize sustainable strategies, collective efforts will be needed targeted at crop damage prevention through reducing pest populations and densities in the medium to long term. The sooner we transform human action from environmentally damaging to biodiversity promoting, the higher is our insurance asset that secures human well-being under a changing climate.
The Mediterranean area reveals a strong vulnerability to future climate change due to a high exposure to projected impacts and a low capacity for adaptation highlighting the need for robust regional or local climate change projections, especially for extreme events strongly affecting the Mediterranean environment. The prevailing study investigates two major topics of the Mediterranean climate variability: the analysis of dynamical downscaling of present-day and future temperature and precipitation means and extremes from global to regional scale and the comprehensive investigation of temperature and rainfall extremes including the estimation of uncertainties and the comparison of different statistical methods for precipitation extremes. For these investigations, several observational datasets of CRU, E-OBS and original stations are used as well as ensemble simulations of the regional climate model REMO driven by the coupled global general circulation model ECHAM5/MPI-OM and applying future greenhouse gas (GHG) emission and land degradation scenarios.
Considering its social, economic and natural conditions the Mediterranean Area is a highly vulnerable region by designated affections of climate change. Furthermore, its climatic characteristics are subordinated to high natural variability and are steered by various elements, leading to strong seasonal alterations. Additionally, General Circulation Models project compelling trends in specific climate variables within this region. These circumstances recommend this region for the scientific analyses conducted within this study. Based on the data of the CMIP3 database, the fundamental aim of this study is a detailed investigation of the total variability and the accompanied uncertainty, which superpose these trends, in the projections of temperature, precipitation and sea-level pressure by GCMs and their specific realizations. Special focus in the whole study is dedicated to the German model ECHAM5/MPI-OM. Following this ambition detailed trends and mean values are calculated and displayed for meaningful time periods and compared to reanalysis data of ERA40 and NCEP. To provide quantitative comparison the mentioned data are interpolated to a common 3x3° grid.
The total amount of variability is separated in its contributors by the application of an Analysis of Variance (ANOVA). For individual GCMs and their ensemble-members this is done with the application of a 1-way ANOVA, separating a treatment common to all ensemble-members and variability perturbating the signal given by different initial conditions. With the 2-way ANOVA the projections of numerous models and their realizations are analysed and the total amount of variability is separated into a common treatment effect, a linear bias between the models, an interaction coefficient and the residuals.
By doing this, the study is fulfilled in a very detailed approach, by considering yearly and seasonal variations in various reasonable time periods of 1961-2000 to match up with the reanalysis data, from 1961-2050 to provide a transient time period, 2001-2098 with exclusive regard on future simulations and 1901-2098 to comprise a time period of maximum length. The statistical analyses are conducted for regional-averages on the one hand and with respect to individual grid-cells on the other hand. For each of these applications the SRES scenarios of A1B, A2 and B1 are utilized. Furthermore, the spatial approach of the ANOVA is substituted by a temporal approach detecting the temporal development of individual variables. Additionally, an attempt is made to enlarge the signal by applying selected statistical methods.
In the detailed investigation it becomes evident, that the different parameters (i.e. length of temporal period, geographic location, climate variable, season, scenarios, models, etc…) have compelling impact on the results, either in enforcing or weakening them by different combinations. This holds on the one hand for the means and trends but also on the other hand for the contributions of the variabilities affecting the uncertainty and the signal. While temperature is a climate variable showing strong signals across these parameters, for precipitation mainly the noise comes to the fore, while for sea-level pressure a more differentiated result manifests. In turn, this recommends the distinguished consideration of the individual parameters in climate impact studies and processes in model generation, as the affecting parameters also provide information about the linkage within the system.
Finally, an investigation of extreme precipitation is conducted, implementing the variables of the total amount of heavy precipitation, the frequency of heavy-precipitation events, the percentage of this heavy precipitation to overall precipitation and the mean daily intensity from events of heavy precipitation. Each time heavy precipitation is defined to exceed the 95th percentile of overall precipitation. Consecutively mean values of these variables are displayed for ECHAM5/MPI-OM and the multi-model mean and climate sensitivities, by means of their difference between their average of the past period of 1981-2000 and the average of one of the future periods of 2046-2065 or 2081-2100. Following this investigation again an ANOVA is conducted providing a quantitative measurement of the severity of change of trends in heavy precipitation across several GCMs.
Besides it is a difficult task to account for extreme precipitation by GCMs, it is noteworthy that the investigated models differ highly in their projections, resulting partially in a more smoothed and meaningful multi-model mean. Seasonal alterations of the strength of this behaviour are quantitatively supported by the ANOVA.
Der Klimawandel und insbesondere die globale Erwärmung gehören aktuell zu den größten Herausforderungen an Politik und Wissenschaft. Steigende CO2-Emissionen sind hierbei maßgeblich für die Klimaerwärmung verantwortlich. Ein regulierender Faktor beim CO2-Austausch mit der Atmosphäre ist die Vegetation, welche als CO2-Senke aber auch als CO2-Quelle fungieren kann. Diese Funktionen können durch Analysen der Landbedeckungsänderung in Kombination mit Modellierungen der Kohlenstoffbilanz quantifiziert werden, was insbesondere von aktuellen und zukünftigen politischen Instrumenten wie CDM (Clean Development Mechanism) oder REDD (Reducing Emissions from Deforestation and Degradation) gefordert wird. Vor allem in Regionen mit starker Landbedeckungsänderung und hoher Bevölkerungsdichte sowie bei geringem Wissen über die Produktivität und CO2-Speicherpotentiale der Vegetation, bedarf es einer Erforschung und Quantifizierung der terrestrischen Kohlenstoffspeicher. Eine Region, für die dies in besonderem Maße zutrifft, ist Westafrika. Jüngste Studien haben gezeigt, dass sich einerseits die Folgen des Klimawandels und Umweltveränderungen sehr stark in Westafrika auswirken werden und andererseits Bevölkerungswachstum eine starke Änderung der Landbedeckung für die Nutzung als agrarische Fläche bewirkt hat. Folglich sind in dieser Region die terrestrischen Kohlenstoffspeicher durch Ausdehnung der Landwirtschaft und Waldrodung besonders gefährdet. Große Flächen agieren anstelle ihrer ursprünglichen Funktion als CO2-Senke bereits als CO2-Quelle. [...]
The right timing of phenological events is crucial for species fitness. Species should be highly synchronized with mutualists, but desynchronized with antagonists. With climate warming phenological events advance in many species. However, often species do not respond uniformly to warming temperatures. Species-specific responses to climate warming can lead to asynchrony or even temporal mismatch of interacting species. A temporal mismatch between mutualists, which benefit from each other, can have negative consequences for both interaction partners. For host-parasitoid interactions temporal asynchrony can benefit the host species, if it can temporally escape its parasitoid, with negative consequences for the parasitoid species, but benefit the parasitoid species if it increases synchrony with its host, which can negatively affect the host species. Knowledge about the drivers of phenology and the species-specific responses to these drivers are important to predict future effects of climate change on trophic interactions. In this dissertation I investigated how different drivers act on early flowering phenology and how climate warming affects the tritrophic relationship of two spring bees (Osmia cornuta & Osmia bicornis), an early spring plant (Pulsatilla vulgaris), which is one of the major food plants of the spring bees, and three main parasitoids of the spring bees (Cacoxenus indagator, Anthrax anthrax, Monodontomerus).
In Chapter II I present a study in which I investigated how different drivers and their change over the season affect the reproductive success of an early spring plant. For that I recorded on eight calcareous grasslands around Würzburg, Germany the intra-seasonal changes in pollinator availability, number of co-flowering plants and weather conditions and studied how they affect flower visitation rates, floral longevity and seed set of the early spring plant P. vulgaris. I show that bee abundances and the number of hours, which allowed pollinator foraging, were low at the beginning of the season, but increased over time. However, flower visitation rates and estimated total number of bee visits were higher on early flowers of P. vulgaris than later flowers. Flower visitation rates were also positively related to seed set. Over time and with increasing competition for pollinators by increasing numbers of co-flowering plants flower visitation rates decreased. My data shows that a major driver for early flowering dates seems to be low interspecific competition for pollinators, but not low pollinator abundances and unfavourable weather conditions.
Chapter III presents a study in which I investigated the effects of temperature on solitary bee emergence and on the flowering of their food plant and of co-flowering plants in the field. Therefore I placed bee cocoons of two spring bees (O. cornuta & O. bicornis) on eleven calcareous grasslands which differed in mean site temperature. On seven of these grasslands the early spring plant P. vulgaris occurred. I show that warmer temperatures advanced mean emergence in O. cornuta males. However, O. bicornis males and females of both species did not shift their emergence. Compared to the bees P. vulgaris advanced its flowering phenology more strongly with warmer temperatures. Co-flowering plants did not shift flowering onset. I suggest that with climate warming the first flowers of P. vulgaris face an increased risk of pollinator limitation whereas for bees a shift in floral resources may occur.
In Chapter IV I present a study in which I investigated the effects of climate warming on host-parasitoid relationships. I studied how temperature and photoperiod affect emergence phenology in two spring bees (O. cornuta & O. bicornis) and three of their main parasitoids (C. indagator, A. anthrax, Monodontomerus). In a climate chamber experiment with a crossed design I exposed cocoons within nest cavities and cocoons outside of nest cavities to two different temperature regimes (long-term mean of Würzburg, Germany and long-term mean of Würzburg + 4 °C) and three photoperiods (Würzburg vs. Snåsa, Norway vs. constant darkness) and recorded the time of bee and parasitoid emergence. I show that warmer temperatures advanced emergence in all studied species, but bees advanced less strongly than parasitoids. Consequently, the time period between female bee emergence and parasitoid emergence decreased in the warm temperature treatment compared to the cold one. Photoperiod influenced the time of emergence only in cocoons outside of nest cavities (except O. bicornis male emergence). The data also shows that the effect of photoperiod compared to the effect of temperature on emergence phenology was much weaker. I suggest that with climate warming the synchrony of emergence phenologies of bees and their parasitoids will amplify. Therefore, parasitism rates in solitary bees might increase which can negatively affect reproductive success and population size.
In this dissertation I show that for early flowering spring plants low interspecific competition for pollinators with co-flowering plants is a major driver of flowering phenology, whereas other drivers, like low pollinator abundances and unfavourable weather conditions are only of minor importance. With climate warming the strength of different drivers, which act on the timing of phenological events, can change, like temperature. I show that warmer temperatures advance early spring plant flowering more strongly than bee emergence and flowering phenology of later co-flowering plants. Furthermore, I show that warmer temperatures advance parasitoid emergence more strongly than bee emergence. Whereas temperature changes can lead to non-uniform temporal shifts, I demonstrate that geographic range shifts and with that altered photoperiods will not change emergence phenology in bees and their parasitoids. In the tritrophic system I investigated in this dissertation climate warming may negatively affect the reproductive success of the early spring plant and the spring bees but not of the parasitoids, which may even benefit from warming temperatures.
I. Climate change comprises average temperatures rise, changes in the distribution of precipitation and an increased amount and intensity of extreme climatic events in the last decades. Considering these serious changes in the abiotic environment it seems obvious that ecosystems also change. Flora and fauna have to adapt to the fast changing conditions, migrate or go extinct. This might result in shifts in biodiversity, species composition, species interactions and in ecosystem functioning and services. Mountains play an important role in the research of these climate impacts. They are hotspots of biodiversity and can be used as powerful natural experiments as they provide, within short distances, the opportunity to research changes in the ecosystem induced by different climatic contexts. In this dissertation two approaches were pursued: i) surveys of biodiversity, trait dominance and assembly rules in communities depending on the climatic context and different management regimes were conducted (chapters II and III) and ii) the effects of experimental climate treatments on essential ecosystem features along the altitudinal gradient were assessed (chapters IV, V and VI). II. We studied the relative importance of management, an altitudinal climatic gradient and their interactions for plant species richness and the dominance of pollination types in 34 alpine grasslands. Species richness peaked at intermediate temperatures and was higher in grazed grasslands compared to non-managed grasslands. We found the climatic context and also management to influence the distribution and dominance structures of wind- and insect-pollinated plants. Our results indicate that extensive grazing maintains high plant diversity over the full subalpine gradient. Rising temperatures may cause an upward shift of the diversity peak of plants and may also result in changed species composition and adaptive potential of pollination types. III. On the same alpine grasslands we studied the impact of the climatic context along an altitudinal gradient on species richness and community assembly in bee communities. Species richness and abundance declined linearly with increasing altitude. Bee species were more closely related at high altitudes than at low altitudes. The proportion of social and ground-nesting species, as well as mean body size and altitudinal range of bees, increased with increasing altitude, whereas the mean geographic distribution decreased. Our results suggest that community assembly at high altitudes is dominated by environmental filtering effects, while the relative importance of competition increases at low altitudes. We conclude that ongoing climate change poses a threat for alpine specialists with adaptations to cool environments but low competitive capacities. IV. We determined the impacts of short-term climate events on flower phenology and assessed whether those impacts differed between lower and higher altitudes. For that we simulated advanced and delayed snowmelt as well as drought events in a multi site experiment along an altitudinal gradient. Flower phenology was strongly affected by altitude, however, this effect declined through the season. The manipulative treatments caused only few changes in flowering phenology. The effects of advanced snowmelt were significantly greater at higher than at lower sites, but altitude did not influence the effect of the other treatments. The length of flowering duration was not significantly influenced by treatments. Our data indicate a rather low risk of drought events on flowering phenology in the Bavarian Alps. V. Changes in the structure of plant-pollinator networks were assessed along an altitudinal gradient combined with the experimental simulation of potential consequences of climate change: extreme drought events, advanced and delayed snowmelt. We found a trend of decreasing specialisation and therefore increasing complexity in networks with increasing altitude. After advanced snowmelt or drought networks were more specialised especially at higher altitudes compared to control plots. Our results show that changes in the network structures after climate manipulations depend on the climatic context and reveal an increasing susceptibility of plant-pollinator networks with increasing altitude. VI. The aim of this study was to determine the combined effects of extreme climatic events and altitude on leaf CN (carbon to nitrogen) ratios and herbivory rates in different plant guilds. We found no overall effect of climate manipulations (extreme drought events, advanced and delayed snowmelt) on leaf CN ratios and herbivory rates. However, plant guilds differed in CN ratios and herbivory rates and responded differently to altitude. CN ratios of forbs (legume and non-legume) decreased with altitude, whereas CN ratios of grasses increased with altitude. Further, CN ratios and herbivory rates increased during the growing season, indicating a decrease of food plant quality during the growing season. Insect herbivory rates were driven by food plant quality. Contrasting altitudinal responses of forbs versus grasses give reason to expect changed dominance structures among plant guilds with ongoing climate change. VII. This dissertation contributes to the understanding of factors that determine the composition and biotic interactions of communities in different climates. The results presented indicate that warmer climates will not only change species richness but also the assembly-rules for plant and bee communities depending on the species' functional traits. Our investigations provide insights in the resilience of different ecosystem features and processes towards climate change and how this resilience depends on the environmental context. It seems that mutualistic interactions are more susceptible to short-term climate events than flowering phenology and antagonistic interactions such as herbivory. However, to draw more general conclusions more empirical data is needed.
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.
The increase in intensively used areas and climate change are direct and indirect consequences of anthropogenic actions, caused by a growing population and increasing greenhouse gas emissions. The number of research studies, investigating the effects of land use and climate change on ecosystems, including flora, fauna, and ecosystem services, is steadily growing. This thesis contributes to this research area by investigating land-use and climate effects on decomposer communities (arthropods and microbes) and the ecosystem service ‘decomposition of dead material’.
Chapter II deals with consequences of intensified land use and climate change for the ecosystem service ‘decomposition of dead organic material’ (necromass). Considering the severe decline in insects, we experimentally excluded insects from half of the study objects. The decomposition of both dung and carrion was robust to land-use changes. Dung decomposition, moreover, was unaffected by temperature and the presence/ absence of insects. Along the altitudinal gradient, however, highest dung decomposition was observed at medium elevation between 600 and 700 m above sea level (although insignificant). As a consequence, we assume that at this elevation there is an ideal precipitation:temperature ratio for decomposing organisms, such as earthworms or collembolans. Carrion decomposition was accelerated by increasing elevation and by the presence of insects, indicating that increasing variability in climate and an ongoing decline in insects could modify decomposition processes and consequently natural nutrient cycles. Moreover, we show that different types of dead organic material respond differently to environmental factors and should be treated separately in future studies.
In Chapter III, we investigated land-use and climate effects on dung-visiting beetles and their resource specialization. Here, all beetles that are preferentially found on dung, carrion or other rotten material were included. Both α- and γ-diversity were strongly reduced in agricultural and urban areas. High precipitation reduced dung-visiting beetle abundance, whereas γ-diversity was lowest in the warmest regions. Resource specialization decreased with increasing temperatures. The results give evidence that land use as well as climate can alter dung-visiting beetle diversity and resource specialization and may hence influence the natural balance of beetle communities and their contribution to the ecosystem service ‘decomposition of dead material’.
The following chapter, Chapter IV, contributes to the findings in Chapter II. Here, carrion decomposition is not only explained by land-use intensity and climate but also by diversity and community composition of two taxonomic groups found on carrion, beetles and bacteria. The results revealed a strong correlation between bacteria diversity and community composition with temperature. Carrion decomposition was to a great extent directed by bacterial community composition and precipitation. The role of beetles was neglectable in carrion decomposition. With this study, I show that microbes, despite their microscopic size, direct carrion decomposition and may not be neglected in future decomposition studies.
In Chapter V a third necromass type is investigated, namely deadwood. The aim was to assess climate and land-use effects on deadwood-inhabiting fungi and bacteria. Main driver for microbial richness (measured as number of OTUs) was climate, including temperature and precipitation. Warmer climates promoted the diversity of bacteria, whereas fungi richness was unaffected by temperature. In turn, fungi richness was lower in urban landscapes compared to near-natural landscapes and bacteria richness was higher on meadows than on forest sites. Fungi were extremely specialized on their host tree, independent of land use and climate. Bacteria specialization, however, was strongly directed by land use and climate. These results underpin previous studies showing that fungi are highly specialized in contrast to bacteria and add new insights into the robustness of fungi specialization to climate and land use.
I summarize that climate as well as intensive land use influence biodiversity. Temperature and precipitation, however, had positive and negative effects on decomposer diversity, while anthropogenic land use had mostly negative effects on the diversity of decomposers.
Combined effects of climate change and extreme events on plants, arthropods and their interactions
(2013)
I. Global climate change directly and indirectly influences biotic and abiotic components of ecosystems. Changes in abiotic ecosystem components caused by climate change comprise temperature increases, precipitation changes and more frequently occurring extreme events. Mediated by these abiotic changes, biotic ecosystem components including all living organisms will also change. Expected changes of plants and animals are advanced phenologies and range shifts towards higher latitudes and altitudes which presumably induce changes in species interactions and composition. Altitudinal gradients provide an optimal opportunity for climate change studies, because they serve as natural experiments due to fast changing climatic conditions within short distances. In this dissertation two different approaches were conducted to reveal species and community responses to climate change. First, species richness and community trait analyses along an altitudinal gradient in the Bavarian Alps (chapters II, III) and second, climate change manipulation experiments under different climatic contexts (chapters IV, V, IV). II. We performed biodiversity surveys of butterfly and diurnal moth species on 34 grassland sites along an altitudinal gradient in the National Park Berchtesgaden. Additionally, we analysed the dominance structure of life-history traits in butterfly assemblages along altitude. Species richness of butterflies and diurnal moths decreased with increasing altitude. The dominance of certain life-history-traits changed along the altitudinal gradient with a higher proportion of larger-winged species and species with higher egg numbers towards higher altitudes. However, the mean egg maturation time, population density and geographic distribution within butterfly assemblages decreased with increasing altitude. Our results indicate that butterfly assemblages were mainly shaped by environmental filtering. We conclude that butterfly assemblages at higher altitudes will presumably lack adaptive capacity to future climatic conditions, because of specific trait combinations. III. In addition to butterfly and diurnal moth species richness we also studied plant species richness in combination with pollination type analyses along the altitudinal gradient. The management type of the alpine grasslands was also integrated in the analyses to detect combined effects of climate and management on plant diversity and pollination type. Plant species richness was highest at intermediate altitudes, whereby the management type influenced the plant diversity with more plant species at grazed compared to mown or non-managed grasslands. The pollination type was affected by both the changing climate along the gradient and the management type. These results suggest that extensive grazing can maintain high plant diversity along the whole altitudinal gradient. With ongoing climate change the diversity peak of plants may shift upwards, which can cause a decrease in biodiversity due to reduced grassland area but also changes in species composition and adaptive potential of pollination types. IV. We set up manipulation experiments on 15 grassland sites along the altitudinal gradient in order to determine the combined effects of extreme climatic events (extreme drought, advanced and delayed snowmelt) and elevation on the nutritional quality and herbivory rates of alpine plants. The leaf CN (carbon to nitrogen) ratio and the plant damage through herbivores were not significantly affected by the simulated extreme events. However, elevation influenced the CN ratios and herbivory rates of alpine plants with contrasting responses between plant guilds. Furthermore, we found differences in nitrogen concentrations and herbivory rates between grasses, legumes and forbs, whereas legumes had the highest nitrogen concentrations and were damaged most. Additionally, CN ratios and herbivory rates increased during the growing season, indicating a decrease of food plant quality during the growing season. Contrasting altitudinal responses of grasses, legumes and forbs presumably can change the dominance structure among these plant guilds with ongoing climate change. V. In this study we analysed the phenological responses of grassland species to an extreme drought event, advanced and delayed snowmelt along the altitudinal gradient. Advanced snowmelt caused an advanced beginning of flowering, whereas this effect was more pronounced at higher than at lower altitudes. Extreme drought and delayed snowmelt had rather low effects on the flower phenology and the responses did not differ between higher and lower sites. The strongest effect influencing flower phenology was altitude, with a declining effect through the season. The length of flowering duration was not significantly influenced by treatments. Our data suggest that plant species at higher altitudes may be more affected by changes in snowmelt timing in contrast to lowland species, as at higher altitudes more severe changes are expected. However, the risk of extreme drought events on flowering phenology seems to be low. VI. We established soil-emergence traps on the advanced snowmelt and control treatment plots in order to detect possible changes in abundances and emergence phenologies of five arthropod orders due to elevation and treatment. Additionally, we analysed the responses of Coleoptera species richness to elevation and treatment. We found that the abundance and species richness of Coleoptera increased with elevation as well as the abundance of Diptera. However, the abundance of Hemiptera decreased with elevation and the abundances of Araneae and Hymenoptera showed no elevational patterns. The advanced snowmelt treatment increased the abundances of Araneae and Hymenoptera. The emergence of soil-hibernating arthropods was delayed up to seven weeks at higher elevations, whereas advanced snowmelt did not influence the emergence phenology of arthropods immediately after snowmelt. With climate change earlier snowmelt will occur more often, which especially will affect soil-hibernating arthropods in alpine regions and may cause desynchronisations between species interactions. VII. In conclusion, we showed that alpine ecosystems are sensitive towards changing climate conditions and extreme events and that many alpine species in the Bavarian Alps are endangered. Many alpine species could exist under warmer climatic conditions, however they are expected to be outcompeted by more competitive lowland species. Furthermore, host-parasite or predator-prey interactions can be disrupted due to different responses of certain guilds to climate change. Understanding and predicting the complex dynamics and potential risks of future climate change remains a great challenge and therefore further studies analysing species and community responses to climate change are needed.
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.
Bewertung und Auswirkungen der Simulationsgüte führender Klimamoden in einem Multi-Modell Ensemble
(2013)
Der rezente und zukünftige Anstieg der atmosphärischen Treibhausgaskonzentration bedeutet für das terrestrische Klimasystem einen grundlegenden Wandel, der für die globale Gesellschaft schwer zu bewältigende Aufgaben und Herausforderungen bereit hält. Eine effektive, rühzeitige Anpassung an diesen Klimawandel profitiert dabei enorm von möglichst genauen Abschätzungen künftiger Klimaänderungen.
Das geeignete Werkzeug hierfür sind Gekoppelte Atmosphäre Ozean Modelle (AOGCMs). Für solche Fragestellungen müssen allerdings weitreichende Annahmen über die zukünftigen klimarelevanten Randbedingungen getroffen werden. Individuelle Fehler dieser Klimamodelle, die aus der nicht perfekten Abbildung der realen Verhältnisse und Prozesse resultieren, erhöhen die Unsicherheit langfristiger Klimaprojektionen. So unterscheiden sich die Aussagen verschiedener AOGCMs im Hinblick auf den zukünftigen Klimawandel insbesondere bei regionaler Betrachtung, deutlich. Als Absicherung gegen Modellfehler werden üblicherweise die Ergebnisse mehrerer AOGCMs, eines Ensembles an Modellen, kombiniert. Um die Abschätzung des Klimawandels zu präzisieren, wird in der vorliegenden Arbeit der Versuch unternommen, eine Bewertung der Modellperformance der 24 AOGCMs, die an der dritten Phase des Vergleichsprojekts für gekoppelte Modelle (CMIP3) teilgenommen haben, zu erstellen. Auf dieser Basis wird dann eine nummerische Gewichtung für die Kombination des Ensembles erstellt. Zunächst werden die von den AOGCMs simulierten Klimatologien für einige
grundlegende Klimaelemente mit den betreffenden klimatologien verschiedener Beobachtungsdatensätze quantitativ abgeglichen. Ein wichtiger methodischer Aspekt
hierbei ist, dass auch die Unsicherheit der Beobachtungen, konkret Unterschiede zwischen verschiedenen Datensätzen, berücksichtigt werden. So zeigt sich, dass die Aussagen, die aus solchen Ansätzen resultieren, von zu vielen Unsicherheiten in den Referenzdaten beeinträchtigt werden, um generelle Aussagen zur Qualität von AOGCMs zu treffen. Die Nutzung der Köppen-Geiger Klassifikation offenbart jedoch, dass die prinzipielle Verteilung der bekannten Klimatypen im kompletten CMIP3 in vergleichbar guter Qualität reproduziert wird. Als Bewertungskriterium wird daher hier die Fähigkeit der AOGCMs die großskalige natürliche Klimavariabilität, konkret die hochkomplexe gekoppelte
El Niño-Southern Oscillation (ENSO), realistisch abzubilden herangezogen. Es kann anhand verschiedener Aspekte des ENSO-Phänomens gezeigt werden, dass nicht alle AOGCMs hierzu mit gleicher Realitätsnähe in der Lage sind. Dies steht im Gegensatz zu den dominierenden Klimamoden der Außertropen, die modellübergreifend überzeugend repräsentiert werden. Die wichtigsten Moden werden, in globaler Betrachtung, in verschiedenen Beobachtungsdaten über einen neuen Ansatz identifiziert. So können für einige bekannte Zirkulationsmuster neue Indexdefinitionen gewonnen werden, die sich sowohl als äquivalent zu den Standardverfahren erweisen und im Vergleich zu diesen zudem eine deutliche Reduzierung
des Rechenaufwandes bedeuten. Andere bekannte Moden werden dagegen als weniger bedeutsame, regionale Zirkulationsmuster eingestuft. Die hier vorgestellte
Methode zur Beurteilung der Simulation von ENSO ist in guter Übereinstimmung mit anderen Ansätzen, ebenso die daraus folgende Bewertung der gesamten Performance
der AOGCMs. Das Spektrum des Southern Oscillation-Index (SOI) stellt somit eine aussagekräftige Kenngröße der Modellqualität dar.
Die Unterschiede in der Fähigkeit, das ENSO-System abzubilden, erweisen sich als signifikante Unsicherheitsquelle im Hinblick auf die zukünftige Entwicklung einiger fundamentaler und bedeutsamer Klimagrößen, konkret der globalen Mitteltemperatur,
des SOIs selbst, sowie des indischen Monsuns. Ebenso zeigen sich signifikante Unterschiede für regionale Klimaänderungen zwischen zwei Teilensembles des CMIP3, die auf Grundlage der entwickelten Bewertungsfunktion eingeteilt werden. Jedoch sind diese Effekte im Allgemeinen nicht mit den Auswirkungen der
anthropogenen Klimaänderungssignale im Multi-Modell Ensemble vergleichbar, die für die meisten Klimagrößen in einem robusten multivariaten Ansatz detektiert und
quantifiziert werden können. Entsprechend sind die effektiven Klimaänderungen, die sich bei der Kombination aller Simulationen als grundlegende Aussage des
CMIP3 unter den speziellen Randbedingungen ergeben nahezu unabhängig davon, ob alle Läufe mit dem gleichen Einfluss berücksichtigt werden, oder ob die erstellte nummerische Gewichtung verwendet wird. Als eine wesentliche Begründung hierfür kann die Spannbreite der Entwicklung des ENSO-Systems identifiziert werden. Dies
bedeutet größere Schwankungen in den Ergebnissen der Modelle mit funktionierendem ENSO, was den Stellenwert der natürlichen Variabilität als Unsicherheitsquelle
in Fragen des Klimawandels unterstreicht. Sowohl bei Betrachtung der Teilensembles als auch der Gewichtung wirken sich dadurch gegenläufige Trends im SOI
ausgleichend auf die Entwicklung anderer Klimagrößen aus, was insbesondere bei letzterem Vorgehen signifikante mittlere Effekte des Ansatzes, verglichen mit der
Verwendung des üblichen arithmetischen Multi-Modell Mittelwert, verhindert.
Die mit dem Klimawandel einhergehenden Umweltveränderungen, wie steigende Temperaturen, Abnahme der Sommer- und Zunahme der Winterniederschläge, häufigere und längere Trockenperioden, zunehmende Starkniederschläge, Stürme und Hitzewellen betreffen besonders den Bodenwasserhaushalt in seiner zentralen Regelungsfunktion für den Landschaftswasserhaushalt. Von der Wasserverfügbarkeit im Boden hängen zu einem sehr hohen Grad auch die Erträge der Land- und Forstwirtschaft ab. Eine besonders große Bedeutung kommt dabei der Wasserspeicherkapazität der Böden zu, da während einer Trockenphase die effektiven Niederschläge den Wasserbedarf der Pflanzen nicht decken können und das bereits gespeicherte Bodenwasser das Überleben der Pflanzen sicherstellen kann. Für die land- und forstwirtschaftlichen Akteure sind in diesem Kontext quantitative und qualitative Aussagen zu den Auswirkungen des Klimawandels auf den Boden essenziell, um die notwendigen Anpassungsmaßnahmen für ihre Betriebe treffen zu können.
Zielsetzungen der vorliegenden Arbeit bestehen darin, die Dynamik der Bodenfeuchte in unterfränkischen Böden besser zu verstehen, die Datenlage zum Verlauf der Bodenfeuchte zu verbessern und die Auswirkungen von prognostizierten klimatischen Parametern abschätzen zu können. Hierzu wurden an sechs für ihre jeweiligen Naturräume und hinsichtlich ihrer anthropogenen Nutzung charakteristischen Standorten meteorologisch-bodenhydrologische Messstationen installiert. Die Messstationen befinden sich in einem Rigosol auf Buntsandstein in einem Weinberg bei Bürgstadt sowie auf einer Parabraunerde im Lössgebiet bei Herchsheim unter Ackernutzung. Am Übergang von Muschelkalk in Keuper befinden sich die Stationen in Obbach, wo eine Braunerde unter Ackernutzung vorliegt und im Forst des Universitätswalds Sailershausen werden die Untersuchungen in einer Braunerde-Terra fusca durchgeführt. Im Forst befinden sich auch die Stationen in Oberrimbach mit Braunerden aus Sandsteinkeuper und in Willmars mit Braunerden aus Buntsandstein. Der Beobachtungszeitraum dieser Arbeit reicht von Juli 2018 bis November 2022. In diesen Zeitraum fiel die dreijährige Dürre von 2018 bis 2020, das Jahr 2021 mit einem durchschnittlichen Witterungsverlauf und das Dürrejahr 2022.
Das Langzeitmonitoring wurde von umfangreichen Gelände- und Laboranalysen der grundlegenden bodenkundlichen Parameter der Bodenprofile und der Standorte begleitet. Die bodengeographischen-geomorphologischen Standortanalysen bilden zusammen mit den qualitativen Auswertungen der Bodenfeuchtezeitreihen die Grundlage für Einschätzungen zu den Auswirkungen des Klimawandels auf den Bodenwasserhaushalt. Verlässliche Aussagen zum Bodenwasserhaushalt können nur auf Grundlage von zeitlich und räumlich hoch aufgelösten Daten getroffen werden. Bodenfeuchtezeitreihen zusammen mit den bodenphysikalischen Daten lagen in dieser Datenqualität für Unterfranken bisher nur sehr vereinzelt vor.
Die vorliegenden Ergebnisse zeigen, dass die untersuchten Böden entsprechend den jeweiligen naturräumlichen Gegebenheiten sehr unterschiedliche bodenhydrologische Eigenschaften aufweisen. Während langer Trockenphasen können beispielsweise die Parabraunerden am Standort Herchsheim wegen ihrer höheren Wasserspeicherkapazität die Pflanzen länger mit Wasser versorgen als die sandigen Braunerden am Standort Oberrimbach. Die Bodenfeuchteregime im Beobachtungszeitraum waren sehr stark vom Witterungsverlauf einzelner Jahre abhängig. Das Bodenfeuchteregime bei einem durchschnittlichen Witterungsverlauf wie in 2021 zeichnet sich durch eine langsame Abnahme der Bodenfeuchte ab Beginn der Vegetationsperiode im Frühjahr aus. Regelmäßige Niederschläge im Frühjahr füllen den oberflächennahen Bodenwasserspeicher immer wieder auf und sichern den Bodenwasservorrat in der Tiefe bis in den Hochsommer. Im Hochsommer können Pflanzen dann während der Trockenphasen ihren Wasserbedarf aus den tieferen Horizonten decken. Im Gegensatz dazu nimmt die Bodenfeuchte in Dürrejahren wie 2018 bis 2020 oder 2022 bereits im Frühjahr bis in die untersten Horizonte stark ab. Die nutzbare Feldkapazität ist zum Teil schon im Juni weitgehend ausgeschöpft, womit für spätere Trockenphasen kein Bodenwasser mehr zur Verfügung steht. Die Herbst- und Winterniederschläge sättigen den Bodenwasservorrat wieder bis zur Feldkapazität auf. Bei tiefreichender Erschöpfung des Bodenwassers wurde die Feldkapazität erst im Januar oder Februar erreicht.
Im Zuge der land- und forstwirtschaftlichen Nutzung ist eine gute Datenlage zu den bodenkundlichen und standörtlichen Gegebenheiten für klimaadaptierte Anpassungsstrategien essentiell. Wichtige Zielsetzungen bestehen grundsätzlich in der Erhaltung der Bodenfunktionen, in der Verbesserung der Infiltrationskapazität und Wasserspeicherkapazität. Hier kommt dem Boden als interaktive Austauschfläche zwischen den Sphären und damit dem Bodenschutz eine zentrale Bedeutung zu. Die in Zukunft erwarteten klimatischen Bedingungen stellen an jeden Boden andere Herausforderungen, welchen mit standörtlich abgestimmten Bodenschutzmaßnahmen begegnet werden kann.