Impact of Land Use and Climate Change on Plant Diversity Patterns in Africa

African plant diversity is strongly threatened by land use and climate change. The growing future demand for food and energy in combination with a climate-change induced decrease in yield will lead to an expansion of agricultural areas. In addition, climate change may reduce habitat suitability within the remaining areas and induce shifts of species ranges. Comprehensive concepts that integrate biodiversity conservation and the facilitation of sustainable human development require appropriate methodical approaches and monitoring schemes. Interactions between land use and biodiversity are complex and not completely understood. Various approaches to incorporate biodiversity change by broad scale global change models are compared. It is recognized that no reliable and scientific concepts exist that are able to comprehensively include all relevant drivers of diversity loss. The implementation of species interactions, composition and adaptation, according to land use type, intensity and extent, contributes to an improved understanding of species responses to land use-change, and is still not properly dealt with. For that purpose, interdisciplinary collaborations are required in order to develop joint approaches at the interface between broad scale land use and biodiversity modelling. The integration of land cover change information considerably improves classical species distribution models by delimitating habitat suitability for species and estimating the quality of habitats. Results for a set of woody species in West Africa indicate a decline of their habitat quality by 65% due to woodland cover changes in the reference period from 1990 to 2000. In contrast, within protected areas, local habitat loss is overcompensated by a general improvement of habitat quality by 63%. The approach highlights the benefit of combining the expertise of two different disciplines, remote sensing and macroecology. It is an improvement for the evaluation of habitat quality inside and outside protected areas, and for the spatially and temporally explicit monitoring of biodiversity loss. Habitat conversion, fragmentation and destruction, may cause a severe decline of species ranges. Until 2050, a considerable proportion of plant species occurring across continental Africa is of particular threat by land use change-induced pressure on their habitats. Potential species range sizes decrease from 63% in 2000 to 56% in 2050 in average. While land use activities predominantly affect range-restricted species today, the assumed future expansion of land use areas may additionally impact the ranges of more widespread species that are located in regions of prospected land use intensification. In addition to land use change, climate change is responsible for considerable shifts in geographic size and distribution of species ranges. Accordingly, the reduction of the potential range of a particular species leads to an increase of the relative importance of its remaining range. The range-size rarity index reflects the sum of the inverse range size of all species occurring within a particular area. Shifts in range size rarity for 3,144 plant species due to either land use or climate change and for both in combination for continental Africa were considered. Today, areas housing a large proportion of overall species ranges are located in lowland rainforests and the Afrotropical mountains. Due to the combined effect of land use and climate change, the contribution of many lowland areas the overall species ranges decreases pronouncedly. In contrast, the relative importance of Afromontane areas, the Angolan escarpment, and the Namibian coast to represent overall species ranges increases. The approach facilitates a better measure of the conservation value of particular areas in respect to the future impact of land use and climate change. Thus, the presented results contribute to refine priority areas for conservation, and serve as a valuable indicator to improve nature conservation and management policy. This thesis incorporates assessments of the current and future threat of land use into the evaluation of the status of plant diversity and emphasizes the need for more target-oriented conservation planning. Altogether, it contributes to the development of new methodological approaches for a better understanding of the impact of land use and climate change on plant diversity patterns in Africa.Einfluss von Landnutzung und Klimawandel auf die Pflanzenvielfalt Afrikas Die Pflanzendiversität in Afrika ist durch Landnutzung und Klimawandel bedroht. Die zukünftig nachwachsende Nachfrage von Nahrungsmitteln und Energie, in Kombination mit einem vom Klimawandel verursachten Rückgang der Ernteerträge, kann in Zukunft zu einer Ausdehnung landwirtschaftlich genutzter Flächen führen. Darüber hinaus kann der Klimawandel zu einer Verminderung der Habitateignung innerhalb der verbleibenden Flächen führen sowie eine Verschiebung der Artareale verursachen. Umfassende Konzepte, die den Schutz der Biodiversität und die Option für eine nachhaltige Nutzung integrieren, erfordern den Aufbau methodisch geeigneter Monitoring-Ansätze. Die Wechselwirkungen zwischen Landnutzung und Biodiversität sind komplex und nicht vollständig verstanden. In dieser Arbeit wurden Modellierungsansätze, die Veränderungen der Biodiversität in die Modellierung des “Global Change” auf kontinentaler und globaler Ebene einbeziehen, miteinander verglichen. Daraus geht hervor, das kein umfassendes, wissenschaftlich anerkanntes Konzept existiert, das alle relevanten Faktoren des Diversitätsverlustes umfassend einschließt. Die Einbeziehung von Wechselwirkungen zwischen Arten, deren Zusammensetzung und Anpassungsfähigkeit, bezogen auf den Typ, die Intensität und die Ausdehnung der Landnutzung, trägt zu einem verbesserten Verständnis bei, und wurde bisher nicht ausreichend behandelt. Interdisziplinäre Zusammenarbeit ist erforderlich, um die Wechselwirkungen zwischen Landnutzung und Biodiversität auf kontinentaler und globaler Ebene zu modellieren. Die klassische Artverbreitungsmodellierung wird durch die Einbeziehung von Informationen zur Änderung der Landbedeckung wesentlich verbessert, wodurch der Einfluss auf Habitateignung für Arten und die Habitatqualität abgeschätzt werden kann. Ergebnisse für eine Gruppe holziger Arten in Westafrika deuten auf einen Rückgang ihrer Habitatqualität um 65% hin, verursacht durch die Veränderung der Waldbedeckung im Referenzzeitraum von 1990 bis 2000. Im Gegensatz dazu wird innerhalb der Schutzgebiete der Verlust auf lokaler Ebene durch eine Verbesserung der Habitatqualität von 63% kompensiert. Der Ansatz unterstreicht den Nutzen der Kombination zweier Fachdisziplinen, der Fernerkundung und der Makroökologie. Dies trägt zu einer verbesserten Bewertung der Habitatqualität innerhalb und außerhalb von Schutzgebieten und zu einem detailliert räumlichen und zeitlichen Biodiversitäts-Monitoring bei. Konvertierung, Fragmentierung und Zerstörung von Habitaten können Gründe für eine drastische Verkleinerung von Artarealen sein. Bis zum Jahr 2050 ist ein beachtlicher Anteil der Pflanzenarten, die im kontinentalen Afrika vorkommen, auf Grund des Landnutzungsdruckes auf ihre Habitate besonders gefährdet. Im Vergleich zur potentiellen Größe der Artareale verkleinert sich diese durchschnittlich auf 63% im Jahr 2000 und 56% im Jahr 2050. Während Landnutzungsaktivitäten heute vorrangig kleinräumig verbreitete Arten betreffen, wird für die Zukunft angenommen, dass eine Ausweitung von Landnutzungsflächen zusätzlich Einfluss auf weiträumig verbreitete Arten hat. Zusätzlich zum Landnutzungswandel ist der Klimawandel verantwortlich für maßgebende Veränderungen in Größe und Verbreitung der Artareale. Demzufolge führt eine Verringerung der Arealgröße zu einem Anstieg der relativen Wichtigkeit innerhalb der verbleibenden Fläche. Die “range-size rarity” beschreibt die Summe der inversen Arealgröße aller Arten, die zu der Fläche beitragen. Verschiebungen der “range-size rarity” durch entweder Landnutzung oder Klimawandel und für beide in Kombination wurden für 3,144 Pflanzenarten für den Kontinent Afrika betrachtet. Die größten Proportionen von den gesamten Artarealen beherbergen heute überwiegend die Tieflandregenwälder und die afrotropischen Gebirge. Durch die Kombination der Faktoren Landnutzung und Klimawandel sinkt der Beitrag der gesamten Artareale in vielen Gebieten im Flachland. Im Gegensatz dazu steigt die Wichtigkeit der afromontanen Gebiete, des angolischen Eskarpments und der namibischen Küsten, die die gesamten Artareale repräsentieren. Diese Ansatz ermöglicht eine bessere Beurteilung von Schutzwerten bestimmter Flächen in Hinblick auf zukünftige Landnutzung und Klimawandel. Somit präsentieren die Ergebnisse einen Beitrag zur Verfeinerung der prioritären schützenswerten Flächen, und dienen als ein Indikator zur Verbesserung von Naturschutz und Managmentregelungen. Die durchgeführten Modellierungen verdeutlichen den Einfluss der heutigen und zukünftigen Bedrohung von Biodiversität durch Landnutzung und zeigt einen erhöhten Bedarf für zielorientierte Naturschutzplanung. Insgesamt trägt diese Arbeit mit methodischen Ansätzen zu einem besseres Verständis des Einflusses der Landnutzung und des Klimawandels auf die Pflanzendiversitätsmuster in Afrika bei

Parikh Automata on Infinite Words

Parikh automata on finite words were first introduced by Klaedtke and Rue{\ss} [Automata, Languages and Programming, 2003]. In this paper, we introduce several variants of Parikh automata on infinite words and study their expressiveness. We show that one of our new models is equivalent to synchronous blind counter machines introduced by Fernau and Stiebe [Fundamenta Informaticae, 2008]. All our models admit {\epsilon}-elimination, which to the best of our knowledge is an open question for blind counter automata. We then study the classical decision problems of the new automata models

Die weltraumqualifizierte Datenakquisition des Übergangsstrahlungsdetektors im AMS-02 Experiment auf der Internationalen Raumstation. The Space Qualified Data Acquisition for the Transition Radiation Detector of the AMS-02 Experiment on the International Space Station

The transition radiation detector (TRD) of the Alpha Magnetic Spectrometer (AMS-02) for cosmic rays allows a separation of positrons and protons and will be operated on the International Space Station for three years. Its space qualified readout electronics, developed and operated under responsibility of University of Karlsruhe, and the TRD front end have shown an excellent performance with cosmic rays on the ground in 2008. The readout system and the results of the first data are discussed

Remarks on Parikh-recognizable omega-languages

Several variants of Parikh automata on infinite words were recently introduced by Guha et al. [FSTTCS, 2022]. We show that one of these variants coincides with blind counter machine as introduced by Fernau and Stiebe [Fundamenta Informaticae, 2008]. Fernau and Stiebe showed that every $\omega$-language recognized by a blind counter machine is of the form $\bigcup_iU_iV_i^\omega$ for Parikh recognizable languages $U_i, V_i$, but blind counter machines fall short of characterizing this class of $\omega$-languages. They posed as an open problem to find a suitable automata-based characterization. We introduce several additional variants of Parikh automata on infinite words that yield automata characterizations of classes of $\omega$-language of the form $\bigcup_iU_iV_i^\omega$ for all combinations of languages $U_i, V_i$ being regular or Parikh-recognizable. When both $U_i$ and $V_i$ are regular, this coincides with B\"uchi's classical theorem. We study the effect of $\varepsilon$-transitions in all variants of Parikh automata and show that almost all of them admit $\varepsilon$-elimination. Finally we study the classical decision problems with applications to model checking.Comment: arXiv admin note: text overlap with arXiv:2302.04087, arXiv:2301.0896

Study of leakage currents in pCVD diamonds as function of the magnetic field

pCVD diamond sensors are regularly used as beam loss monitors in accelerators by measuring the ionization of the lost particles. In the past these beam loss monitors showed sudden increases in the dark leakage current without beam losses and these erratic leakage currents were found to decrease, if magnetic fields were present. Here we report on a systematic study of leakage currents inside a magnetic field. The decrease of erratic currents in a magnetic field was confirmed. On the contrary, diamonds without erratic currents showed an increase of the leakage current in a magnetic field perpendicular to the electric field for fields up to 0.6T, for higher fields it decreases. A preliminary model is introduced to explain the observations.Comment: 6 pages, 16 figures, poster at Hasselt Diamond Workshop, Mar 2009, accepted version for publicatio

Reverse engineering queries in ontology-enriched systems: the case of expressive horn description logic ontologies

We introduce the query-by-example (QBE) paradigm for query answering in the presence of ontologies. Intuitively, QBE permits non-expert users to explore the data by providing examples of the information they (do not) want, which the system then generalizes into a query. Formally, we study the following question: given a knowledge base and sets of positive and negative examples, is there a query that returns all positive but none of the negative examples? We focus on description logic knowledge bases with ontologies formulated in Horn-ALCI and (unions of) conjunctive queries. Our main contributions are characterizations, algorithms and tight complexity bounds for QBE

Lorentz shift measurements in heavily irradiated silicon detectors in high magnetic fields

An external magnetic field exerts a Lorentz force on drifting electric charges inside a silicon strip sensor and thus shifts the cluster position of the collected charge. The shift can be related to the Lorentz angle which is typically a few degrees for holes and a few tens of degrees for electrons in a 4 T magnetic field. The Lorentz angle depends upon magnetic field, electric field inside the sensor and temperature. In this study the sensitivity to radiation for fluences up to 10^16 n/cm^2 has been studied. The Lorentz shift has been measured by inducing ionization with 670 nm red or 1070 nm infrared laser beams injected into the back side of the irradiated silicon sensor operated in magnetic fields up to 8 T. For holes the shift as a function of radiation is increasing, while for electrons it is decreasing and even changes sign. The fact that for irradiated sensors the Lorentz shift for electrons is smaller than for holes, in contrast to the observations in non-irradiated sensors, can be qualitatively explained by the structure of the electric field in irradiated sensors.Comment: Accepted publication for RD09 conference in Proceedings of Scienc

Ontology-Mediated Querying with Horn Description Logics

An ontology-mediated query (OMQ) consists of a database query paired with an ontology. When evaluated on a database, an OMQ returns not only the answers that are already in the database, but also those answers that can be obtained via logical reasoning using rules from ontology. There are many open questions regarding the complexities of problems related to OMQs. Motivated by the use of ontologies in practice, new reasoning problems which have never been considered in the context of ontologies become relevant, since they can improve the usability of ontology enriched systems. This thesis deals with various reasoning problems that occur when working with OMQs and it investigates the computational complexity of these problems. We focus on ontologies formulated in Horn description logics, which are a popular choice for ontologies in practice

How to Approximate Ontology-Mediated Queries

We introduce and study several notions of approximation for ontology-mediated queries based on the description logics ALC and ALCI. Our approximations are of two kinds: we may (1) replace the ontology with one formulated in a tractable ontology language such as ELI or certain TGDs and (2) replace the database with one from a tractable class such as the class of databases whose treewidth is bounded by a constant. We determine the computational complexity and the relative completeness of the resulting approximations. (Almost) all of them reduce the data complexity from coNP-complete to PTime, in some cases even to fixed-parameter tractable and to linear time. While approximations of kind (1) also reduce the combined complexity, this tends to not be the case for approximations of kind (2). In some cases, the combined complexity even increases