Agrar-, Ernährungs- und Ingenieurwissenschaftliche Fakultät

Einfluss des Tauwurms (Lumbricus terrestris L.) auf Quantität und Qualität von Bioporen in Ackerböden: Strategien zur Maximierung positiver Effekte des mehrjährigen Futterbaus

2026-06-10T12:35:09Z

Einfluss des Tauwurms (Lumbricus terrestris L.) auf Quantität und Qualität von Bioporen in Ackerböden: Strategien zur Maximierung positiver Effekte des mehrjährigen Futterbaus Lüsebrink, Marcel In den Jahren 2011, 2013, 2014 und 2015 wurden auf einem tiefgründigen Lösslehm (Campus Klein-Altendorf, Universität Bonn) Feldversuche zur Bioporengenese und Mortalität von Lumbricus terrestris nach einer Bodenbearbeitung durchgeführt. Ergänzend wurden Gefäßversuche angelegt, um die Grabegeschwindigkeit der Tauwürmer bei unterschiedlichen Bodenbedingungen und die Biomasseentwicklung bei unterschiedlichen Nahrungsangeboten zu bestimmen. Oberziel der Arbeit war es, die natürlichen Prozesse in Bezug auf die Bioporengenese und Mehrung der Bodenfruchtbarkeit durch L. terrestris zu quantifizieren. Im Hinblick auf eine maximale Perforation des Unterbodens durch Bioporen mit hoher Qualität der Drilosphäre innerhalb eines mehrjährigen Fruchtfolgefeldes wurden zwei Strategien verfolgt. Zum einen sollte eine möglichst hohe Ausgangspopulation zu Beginn der Bodenruhe erhalten werden ohne die Intensität der Bodenbearbeitung zu reduzieren. Zum anderen sollte ein mehrjähriges Fruchtfolgefeld gefunden werden, welches sowohl das Wachstum der Tauwurmpopulation fördert als auch die Grundlage für eine nährstoffreiche Drilosphäre bietet.
Durch eine Bodenbearbeitung freigelegte oder natürlich abgewanderte Tauwürmer müssen umgehend eine neue Wohnröhre für sich erschließen, um den Gefahren an der Bodenoberfläche zu entgehen. Im Versuch hatten neu angelegte Bioporen bei gering komprimierten (1,3 g * cm^-3) Böden eine nahezu vertikale Ausrichtung. Unmittelbar oberhalb des stärker komprimierten (>1,55 g * cm^-3) Unterbodens wurde jedoch eine zunehmend horizontale Porenausrichtung beobachtet. Ab der Ebene zwischen Ober- und Unterboden besiedelte Lumbricus terrestris in allen Versuchsjahren bevorzugt Altporen wieder, um tiefer in den Bodenkörper einzudringen. Im Mittel der Versuchsjahre waren es 38 % der Tauwürmer, die eine neue Pore im Unterboden anlegten. Tauwürmer, die durch eine Bodenbearbeitung verschüttet wurden, benötigten mit zunehmender Höhe der Überdeckung (= Bearbeitungstiefe) mehr Zeit, um einen erneuten Zugang zur Bodenoberfläche anzulegen. Durch die Gefäßversuche wurde statistisch belegt, dass L. terrestris mit sinkender Feuchtigkeit und zunehmender Lagerungsdichte der aufliegenden Bodenschicht mehr Zeit für die Porenneuanlage zur Bodenoberfläche benötigt. In Freilandversuchen kam es ab einer Bodenauflage von 20 cm zu Ausfällen unter den Tauwürmern; dabei stieg die Mortalitätsrate mit zunehmender Auflagehöhe.
Die vertikalen Bewegungen der Tauwürmer wurden in einem artifiziellen Versuchsaufbau aufgezeichnet. Dabei lag die bevorzugte Aufenthaltstiefe der Tauwürmer unterhalb des vom Pflug beeinflussten Bereichs (unterhalb 30 cm Bodentiefe). Lediglich zwischen Mitternacht und den frühen Morgenstunden gab es eine erhöhte Aktivität einzelner Tauwürmer im Bereich von 0 bis 30 cm.
Bodenanalysen der Versuchsanlage in Klein-Altendorf ergaben, dass im Vergleich zum umliegenden Boden C, N, P, S und Ca in der Drilosphäre in signifikant erhöhten Gehalten vorlagen. Ein Gefäßversuch belegte, dass die Intensität der Nährstoffanreicherung auch vom Nahrungsangebot abhängt. Zudem wurde die Biomasseentwicklung der Tauwürmer durch das Nahrungsangebot beeinflusst. In den Nahrungsversuchen erwies sich Wegwarte bezüglich des Biomassezuwachses der Tauwürmer und der Nährstoffanreicherung in der Drilosphäre als die günstigste der vier untersuchten Varianten. Bei einem abwechslungsreichen Nahrungsangebot nahm L. terrestris jedoch nicht bevorzugt Wegwarte auf. Präferiert wurde Weizenstroh, welches als einzige Nahrungsvariante im Test eine Biomassereduktion der Tauwürmer zur Folge hatte.; In the years 2011, 2013, 2014 and 2015 field trials were conducted on a deep loess loam (Campus Klein-Altendorf, University of Bonn) to analyze biopore formation and mortality of dew worms (Lumbricus terrestris) after tillage. Additional column experiments were carried out to estimate (i) the time L. terrestris needs to rebuild a new connection to the soil surface after tillage under different soil conditions and (ii) the development of dew-worm biomass supplied with different food sources. The aim of this study was the quantification of natural processes, in relation to the bioporegenesis and increase of soil fetility by L. terrestris. In order to optimize perennial fodder cropping with regard to increased perforation of the subsoil by biopores with high nutrient concentrations in the drilosphere two startegies have been investigated. Firstly, a high initial population of L. terrestris is required at the beginning of the soil rest. Secondly, a perennial fodder crop is needed that is capable of creating biopores with taproots and supports a high population density and provides the basis for a nutrient rich drilosphere.
Dew worms exposed to the surface by tillage or naturally migrating dew-worms need to create a new burrow to avoid the dangers on the soil surface. Newly created biopores had an almost vertical orientation in the low compacted topsoil (1.3 g * cm^-3). Immediately above the more compacted subsoil (> 1.55 g * cm^-3) a nearly horizontal burrow orientation was observed. From the plane between topsoil and subsoil L. terrestris preferred to reuse burrows for deeper penetration into the soil. In average of three experimental years 38 % of the dew-worms created new burrows to enter the subsoil. With increasing plowing depth Nightcrawlers surviving tillage in deeper soil layers needed more time to rebuild an exit to the soil surface. Column experiments have shown that reduced moisture and increased compaction of the overlying soil layer can also enlarge the time interval. In field trials the mortality rate increased with increasing plowing depth.
The vertical movements of L. terrestris were recorded with an experimental setup based on an artificial pore equipped with inductive sensors. The preferred depth of residences was below the area affected by plowing (> 30 cm depth). In 0 - 30 cm depth increased activity was recorded between midnight until the early morning hours.
Analysis of soil samples from the study site in Klein-Altendorf have shown that nutrient concentrations of C, N, P, S and Ca are significantly increased in the drilosphere compared to the bulk soil. Furthermore, another experiment showed that the intensity of nutrient enrichment depended on the food source. The development of dew worm biomass was also affected by the type of food supply. Chicory resulted in the higher enrichment of dew-worm biomass and nutrient concentration in the drilosphere than lucerne, tall fescue or wheat straw. Therefore, it was unexpected that dew-worms fed with four food types avoided Chicory. In contrast nightcrawlers preferred wheat straw, which is the only tested food source that resulted in a reduction of dew-worm biomass.

Integrating Optical Sensing and Environmental Data for Predicting and Monitoring Plant Diseases in Sugar Beet

2026-06-10T12:15:20Z

Integrating Optical Sensing and Environmental Data for Predicting and Monitoring Plant Diseases in Sugar Beet Ispizua Yamati, Facundo Ramón Cercospora leaf spot (CLS), caused by the fungus Cercospora beticola, is a major foliar disease in sugar beet that shows increased incidence under favorable climatic conditions. This dissertation develops a modular and scalable framework for the detection, quantification, and prediction of disease dynamics under real field conditions. The framework is primarily based on imagery obtained from uncrewed aerial vehicles (UAVs) and integrates remote sensing, machine learning, and epidemiological modeling.
A georeferenced, plant-level monitoring system was established using UAV-acquired red-green-blue and multispectral images. This system enables consistent identification and tracking of individual plants throughout the growing season and supports the generation of standardized datasets for phenotyping. Using this foundation, convolutional neural networks were trained to detect and classify CLS severity directly from UAV imagery with high accuracy. The methodology was successfully applied to Rhizoctonia crown and root rot, demonstrating its robustness and adaptability to diseases with distinct symptomatology.
To evaluate scalability and interoperability, CLS detection was further investigated using satellite and ground-based datasets. A U-Net model was trained to convert UAV images into synthetic satellite observations with characteristics similar to those of PlanetScope data for disease classification. Complementarily, a multisensor ground platform equipped with hyperspectral, thermal, RGB, and LiDAR sensors allowed for presymptomatic detection and detailed canopy characterization. These extensions demonstrate the ability to detect CLS across multiple spatial scales and sensor modalities.
Finally, a hybrid epidemiological model was developed by integrating image-derived features with environmental data and mechanistic, phase-specific predictors. The epidemic process was divided into biologically meaningful phases, including incubation, sporulation, dispersal, and yield impact. This approach enhances both predictive accuracy and biological interpretability.
This dissertation makes three primary contributions: the development of a temporally structured, plant-based monitoring system; the demonstration of a cross-platform sensing strategy spanning UAVs, ground-based sensors, and satellites; and the implementation of a hybrid modeling pipeline that combines mechanistic epidemiological understanding with remote sensing and artificial intelligence. Together, these advances provide a strong foundation for predictive, explainable, and scalable disease monitoring aimed at sustainable crop protection

Phenotypic and molecular adaptations of Zea mays L. to low boron levels

2026-06-10T07:15:19Z

Phenotypic and molecular adaptations of Zea mays L. to low boron levels Matthes, Michaela Boron is an essential micronutrient for crops and deficiencies of boron severely impact on yield. The molecular mechanisms of boron functions in plants, however, remain largely unexplored. Research summarized in this habilitation thesis covers phenotypic adaptations to and molecular processes affected by boron deficiency in the crop maize. This thesis further opens up new research avenues for breeding plants adapted to boron-limited soil conditions.

Computational Geodesy

2026-06-08T06:35:10Z

Computational Geodesy Brockmann, Jan Martin The observation of the dynamically changing system Earth is one major task in geodesy. To measure the temporal changes globally, observations collected by satellites are analyzed to highlight the changes with respect to some long term mean, for instance comparing the measurements to reference surfaces. Furthermore, reference surfaces are required for the realization of reference systems, e.g. the geoid for the definition of the vertical datum. Therefore, an accurate knowledge of these reference surfaces is important in geodesy and other geoscientific disciplines, such as oceanography or geophysics.
This thesis covers the estimation of three different reference surfaces: the geoid - or more generally the Earth's gravity field, the Mean Dynamic ocean Topography (MDT), and the Mean Sea Surface (MSS). The basic idea for the determination of these reference surfaces is to formulate the problem as a (constrained) least squares parameter estimation problem. As a consequence of this design, a tailored parametric representation of the reference surface has to be established. In the framework of least squares estimation, it is immediately possible to account for the stochastic characteristics of the observations and to combine various complementary observation groups in a joint one-step estimation. The solution of the inverse problems becomes numerically and computationally demanding, as a large number of parameters (10⁵ to 10⁶) is required to adequately model the surfaces of interest. Furthermore, a huge number of (correlated) observations (10⁷ to 10⁸) has to be analyzed. Therefore, these challenges have to be solved utilizing specific numerical properties and High Performance Computing (HPC). In this context, the model design, the stochastic modelling and an efficient solution and implementation is referred to as Computational Geodesy.
The first reference surface studied in this contribution is the geoid. The main focus is on the computation of a static global gravity field model from the observations taken by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite. While the general idea is inline with the time-wise GOCE-only models published previously, the improved EGM_TIM_RL06 model benefits from reprocessed gravity gradients and a refined stochastic model. The approach is summarized and the improvements of the new model are presented. Additionally, it is shown how EGM_TIM_RL06 is used as input in the GOCO06S satellite-only model and aspects for the combination with terrestrial gravity data are discussed.
To estimate a geodetic MDT, a parametric least squares estimation approach is proposed and studied in different configurations. The proposed approach is used to jointly estimate the geoid and the MDT from altimetric Sea Surface Height (SSH) observations. A parameterization tailored to the characteristics of the MDT by a C¹-smooth linear combination of Finite Element (FE) basis functions is derived, which is used to approximate the unknown MDT surface. The approach enables to include information about the geoid as stochastic data sets and allows observations related to surface currents to be included (e.g. surface drifters or Synthetic Aperture Radar (SAR) derived Radial Surface Velocity (RSV)). It is shown with the help of simulated and real data experiments, that this kind of complementary observations strongly support the signal separation of the SSH into geoid and MDT.
Similarly, an alternative estimation approach to estimate a parametric MSS model is proposed and numerically studied. Although basically 'just' the temporal average of altimetric SSHs in the analysis period has to be computed, this is challenging due to the spatial and temporal sampling characteristics of the different altimetry missions. Therefore, it is shown how the ocean variability can be coestimated as an additional Sea Level Anomalies (SLAs) model. For both model components, MSS and MDT, a tailored continuous C¹-smooth FE model function is derived. In case of the SLA, it is extended towards a spatio-temporal model using separable basis functions. Numerical real data studies are used to demonstrate the performance of the proposed approach.
For all applications studied, it can be concluded that the parametric approaches accounting for the stochastic characteristics of the observations and using the developed parametric models are well suited and offer advantages compared to the existing (grid based) approaches.